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Unedited notes from an aquaculture class. I believe in sharing any and all information. Feel free to contact me with any questions on this. I'll see what I can remember.
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1/23/09 11:56 AM
Preliminary terms/definitions:
Capture fishery – harvesting of fish or other aquatic organisms that
nature has largely produced – usually related to commercial fishing
(fishing for profit)
Sport fishery – harvesting of fish or other aquatic organisms for
primarily recreational purposes.
Culture fishery (a.k.a. aquaculture – a farmer harvests fish or other
aquatic organism (including shellfish aquatic plants) – that he/she
stocked into a pond, cage, indoor recirculation tank, raceway, etc
and a varying degrees managed their growth and survival often to
be sold for profit. But also subsistence or to support sportfishing.
Some familiar examples of aquaculture
Channel catfish reared in ponds to be sold as food fish.
Atlantic salmon reared in nearshore marine net pens as food fish.
Rainbow trout reared in raceways for stocking purposes re/
sportfisheries
Golden shiners and fathead minnows reared in ponds to sell as bait
dealers
Largemouth bass or bluegill reared in ponds for stocking primate
and recreational ponds / small impoundments
Some less familiar examples of aquaculture
Rearing marine flatflish in anchored, offshore marine nets as food
fish (“open-ocean aquaculture”)
Culturing redear sunfish in ponds for snail control
Paddlefish ranching in small to mid-size impoundments (KY, MO,
Asia) for caviar / meat market
Ultra-extensive “family ponds” in Nepal and other 3rd world
countries for subsistence
Integrated aquaculture systems with carps (agriculture wastes
placed in pounds to stimulate fish production)
Complete vs. Incomplete Aquaculture Operations
Complete: producer deals with all life stages / aspects of rearing a
given culture species: spawning – egg hatching – larval stage –
fingerlings – adult stage; may even produce own feeds (e.g., Kahr’s
paddlefish culture operation)
Incomplete: producer deals only with a few life stages of a species
– e.g. Mo sunfish producers often purchase 1-2” fingerlings, pond
rear to 3-6” (“grow-out”) then sell or e.g. producer deals only with
fingerlings and sells to others for grow-out
Common expressions/subcategoies of aquaculture
Mariculture – any type of aquatic animal/plant aquaculture in ocean
Brakish water aquaculture – in coastal areas
Fish culture – rearing finned fish
Shellfish culture – oysters, clams, mussels
Crustacean culture – crayfish, shrimp, lobsters, crabs
Marine farming – in ocean
Open-ocean aquaculture – offshore marine farming
Warmwater and Coldwater Aquaculture
Terms commonly used in U.S. aquaculture
Terms originate from the two main culture species (channel catfish
and rainbow trout) which involve very distinct rearing methods.
In general, warmwater aquaculture involves fish that grow best at
21-30C (70-86 F) vs. 7-16C) (45-61F_ for coldwater fish
“warmwater facilities” involve largely pond rearing and may include
some coldwater species (catfish, LMB, BG, / HSB, crappie, walleye,
muskelluge, perch [lost valley]
1/23/09 11:56 AM
Extensive vs. Intensive Aquaculture
Extensive: Rearing culture species under conditions close to the
natural production capacity of the rearing environment (e.g. a pond)
typically low-maintenance (natural fish density; no supplemental
feed)
o (Note: in pond settings, adding only fertilizer to stimulate
primary production is still considered “extensive”)
o Example:
Raising fish in fertilized or unfertilized fonds at natural
densities without adding prepared feeds
Rearing planktivorous fishes in netpens or
impoundments
Traditional polyculture
Intensive – rearing culture species under conditions where
productivity is artificially boosted to well above what is natural;
maintenance of such unnatural conditions must be carefully
sustained to avoid catastrophic loss.
o Common characteristics – use of formulated feed; high
stocking density; need for water quality control – O2 NH3,
disease control, need for continuous monitoring
o Examples: Catfish ponds (stocking 10,000 vs. 500 fingerlings
per acre), formulated feed, aeration, careful monitoring of DO
o Salmon in net pens (high density; feed medicants) vs. salmon
ranching
o Indoor water recirculation tanks – RASs; formulated feed only;
high fish densities; management of water quality; temp,
chemistry and solids removal; disease control
1/23/09 11:56 AM
History of Aquaculture (and species cultured world-wide)
Indo-Pacific
o China:
Earliest records of aquaculture
Chinese aquaculture closely associated with silk
manufacturing (2700 BC)
Artificial hatching practiced ~2000 BC
Treatise on Common Carp (*Cyprinus carpio) culture
written by Fan Lai 475 BC
1214 AD: records of carp fry being transported in
baskets (nature of early aquaculture)
1639 AD: Heu wrote “A complete Book of Agriculture”
(carp collected from rivers and reared in ponds)
Story of origin of Chinese polyculture:
Common carp pronounced “Lee” in China
During 6th Century, emperor’s name also pronounced
“Lee”, causing embarrassment b/c “eating common
carp” sounded like one was “eating the emperor”
Efforts put forth to rear other carp species
Collected multiple carp species from rivers to rear in
ponds, but couldn’t effectively select out the common
carp; i.e., didn’t solve the problem but led to rearing of
mixed carp species together, polyculture ; for which
China is now known for
What is polyculture?
Involves rearing of more than one culture species together to
achieve productive advantage (versus monoculture)
Best known polyculture developed and perfected by Chinese –
involves rearing up to six “Asian carp” species together in ponds
Production increases come from two sources:
o 1) taking advantage of multiple feeding niches in a pond
o 2) “enrichment effects” – feeding by one species enhances
food supply of another
Up to six species involved:
o Common carp Cyprinus carpio – consumes benthic
invertebrates (chironomids) and detritus (detritus is dead
organic matter)
o Silver carp Hypophthalmichtys molitrix feeds of the
phytoplankton in midwater
o Bighead carp Aristichtys nobilis feeds on zooplankton in
midwater
o Grass carp Ctenopharyngodon idellus consumes vegetation
(nearshore)
o Black carp Mylopharyngodon piceus has pharyngeal teeth and
consumes snails (imported for snail control)
o Mud carp Cirrhinus moliforella eats decaying vegetation, some
benthic inverts and detritus on pond bottom
o Enrichment effects – e.g., mud and common carps both
consume the feces of grass carp; bighead carp’s zooplankton
consumption releases trapped phosphorous which stimulates
bottom-up productivity; grass carp feces stimulate primary
productivity in pond
o Note: the six carp species are not obligate feeders – i.e., some
diet flexibility
Chinese Polyculture
o Chinese have perfected stocking rates of the six carps (or
subsets), pond fertilizing regimes, and/or additions of
agricultural wates to maximize fish production via extensive
pond culture according to local conditions
o Production data from China has been hard to secure. Former
Soviet Union study shows polyculture (extensive) increases
pond production 400-600 kg/ha at mid latitudes; 600-1000
kg/ha at southern latitudes. Chinese may achieve more
production gains.
Duo-culture
o Involves rearing of two aquatic species together
o We have reared bulegill and yellow perch together in cages
and RASs to enhance BG growth
o How – the perch interfere with aggressive behaviors among
the BG (shading) which normally leads to dominate
hierarchies
Asian Polyculture (cont.)
o Current trends are towards intensive polyculture where
prepared feeds are given to further enhance pond production
o Maximum polyculture production levels of 7500 to 8000 kg/ha
(wow ~ 7000 lbs / acre) have been documented in the Far
East
o Average Asian production levels for intensive polycultures are
3000 – 4000 kg/ha
Side note: Asian carp in U.S.
o At least five of six major Asian carp (all but mud carp)
introduced into U.S.
o Common carp introduced over a century ago
o Other Asian carps more recently introduced for aquaculture-
related purposes (food-fish; vegetation control; snail control)
Black carp for snail control
U.S. consumers eat negligible amounts of carp
Asian enclaves (large U.S. cities, Toronto) represent a
substantial demand for bighead and grass carp; other
carps
Establishment of Asian carp populations in “natural
waters” of the U.S. (MS drainage) has contributed to
negative view of aquaculture as an “environmentally-
unfriendly” industry
Bighead, silver carp, and grass carp populations in MS
drainage appear to be growing/expanding rapidly
Concern over trophic competition with native species –
zooplankton, phytoplankton (evidence of declining Wr of
resident species in IL)
o Silver carp – Illinois River
Fish reaching weights up to 60 pounds
Major effort being put forth to exclude from Great Lakes
Jumping tendency is likely a fright response – presents
hazard for boaters
o Grass carp
Well-known for vegetation control
Reach 100 lbs: valued as a food-fish by Asian enclaves
Also present a jumping hazard when seining production
ponds
o A Point re/ Asian Carps
Characteristics that cause Asian carps that cause them
to be so widely reared (in aquaculture) and consumed:
E.g., general “hardiness”. High tolerance to
handling; feed low on food chains but, flexible
feeders; tolerate wide temp. ranges; highly
prolific; disease resistant fast growers ---
Also make good “invaders”
History
Chinese emigrants believed to have brought aquaculture concepts
to nearby countries: Taiwan, Thailand, Malaysia and Indonesia
Many species historically cultured in these four countries; most
common is the milk fish (*Chanos chanos) whose culturing is
believed to have begun in Java in the 15th century
Euryhaline, fast-growing, reared in brackish water ponds; feed low
on the food chain; disease resistant; harvested well below
maximum sizes
Cambodia: Siluroid catfishes have long been reared in bamboo
cages in flowing water and ponds
Most important species is *Pangasius sutchi reaching 150 cm (60
in); tolerates poor water quality; voracious feeders; supplemental
feeding needed; high stocking densities (also sold as aquarium fish
– Iridescent shark)
Thailand: Pangasius spp. Has long culture history; also Java tilapia
(*Oreochromis mossambicus) reared since 1930s; tolerate warm
water, low DO and variable salinity
India/Pakistan:
Long history of aquaculture documented back to 300 BC
Major culture species include Indian carps: “catla” (*Catla catla),
“rohu” (*Labeo rohita), “Mrigal” (*Cirrhinus mrigala); “calbasu”
(Labeo calbasu); often grown together in polyculture
Also catfish Pangasius and * Clarias spp. (possess accessory
breathing organ – “walking catfish”) and prawns; Asian carps
Reared together in polyculture
Hybrids have been formed with Chinese carps for hybrid vigor
(growth) in ponds
Japan
Substantial aquaculture activity dating to 745 AD (clam culture)
Current major culture species: mullet (*Mugil spp.) brakish water
ponds; yellowtail (*Seriola quinqueradiata) cage culture now
including “OOA” (Hawaii); common carp; rainbow trout
(*Oncorhynchus mykiss); shrimp (*Penaeus spp.); oyster
(*Crassostrea gigas)
Mullet (mugil spp_)
o Exist world-wide, in temperate to tropic zones; harvested in
capture fisheries
o Inhabit marine / brakish waters; benthic feeders; max size
~20 in.
o Excellent flesh texture and taste
o >100 species; many species called mullet are not mullet
(mullet’s favorable reputation being “extended” to other
species) (e.g., white sucker in Ithaca NY)
o Culture characteristics:
Euryhaline
Wide temperature tolerance
Reared in brackish-water coastal ponds
Accept supplemental feeds (rice bran, peanut meal)
beyond natural diet
Cultured mainly as a food fish
Artificially spawned – gives control over seed
availability; versus harvesting seed
Yellowtail Seriola quinqueradiata (Carangidae)
o Pacific Ocean; pelagic species; fast swimmers
o Culture: reared to 4-6 pounds (age 2); cage culture;
cannibalistic in culture systems
Australia
Oyster farming has longest hsitroy (1800s): rock oyster (Crassostrea
commercialis); marron crayfish (*Cherax tenuimanus) and red claw
(C. quadricarinatus); rainbow and brown trout (Salmo trutta);
recently Southern bluefin tuna reared for Japan’s sashimi market
Hawaii; Milkfish (Chanos chanos); freshwater prawn (Macrobrachium
rosenbergii); mullet (Mugil spp.) in ponds
Southern Bluefin Tuna (Thunnus macoyii)
Reared off southern Australia since 1991 (Port Lincoln)
High prices paid by Japan fish market; One grow-out net-pen
(pontoon) contains ~1700 fish; market value $1.7 million
Individual fish (dressed, frozen) auctioned off in Japanese fish
markets
Loaded into transport pontoons and slowly (1 month) towed to
coastal rearing area
Currently fed baitfish (prepared diets being developed – less costly);
40,000 tons baitfish used annually in one operation! (bio-concern??)
Fish reachmarket weight between 20-30kg (55 lbs) in 4-9 months
Culturing the fish give desirable marble trait
Overfishing and consequent low/declining densities of SBFT and also
NBFT keep value of cultured BFT very night
Entry into SBFT culture operation difficult; --must be former
commercial fisher with quota-harvest share;
Pontoons costly ($80-200k); feed costs high; must secure coastal
area lease
Tasmania
Trout farms; giant freshwater grayfish (*Astracopsis sp.) reaches 8
lbs, activity in Moberly, MO (“freshwater lobsters”)
Atlantic salmon
Aquaculture advantages in Australia and Tasmania; strong
government leadership favorable for aquaculture; low population
density; good environmental record; proximity to vast Asian
markets
Trend shift in Indo-Pacific region:
Post WW-II, aquaculture production focused on efficient protein
production to feed growing human population high-yield/ low- input
species e.g., carps, tilapia and mollusks; environmentally favorable
– little N, P, BOD
Post 1980, emphasis shifted to production of “high-value” carniv.
Species (shrimps/salmon), paralleled by shifts from extensive to
more intensive rearing; commercial feeds, protein wasting, less
environmentally friendly
This was in response to growing demand for certain higher-level-
feeding species by the “sophisticated pallet” of developed countries
like the U.S.
E.g. Indonesia; milkfish to black tiger shrimp (*Penaeus monodon);
China, the base of efficient carp production became #1 shrimp
producer
“Feeding up the food chain”; more protein required; more wastes /
pollutants
Israel is only country in region with substantial history of aquaculture
Main species cultured; common carp, tilapia, mullets, other Chinese
carps in polyculture with common carp
Inrael has water supply limitation – led to reduced total culture-pond
numbers as development has progressed:
Post 1970s, # of ponds declined (79 to 59; 10,000 to 7,000 surface
acres 30%)
Yet, fish yields increased (3.5 + tons/acre) by shifting from mono- to
polyculture (intensive)
Egypt – some pond culture of Indian carps (Labeo, Cirrhina, Catla) plus eel
(*Anguilla), Chineese silver carp (*Hypophalmichthys molitrix); common carp
and Nile tilapia (Oreochromis niloticus) (major species)
Iran – sturgeon (*Acipenser spp.)
Syria – African catfishes (*Clarias spp.)
Iraq – Barbus spp. (local herbivorous cyprinid; Tawes); common, grass and
silver carps in pond culture; 1,893 fish farms; Fish Research Centre; Baghdad
– aquaculture research; 100 of staff
Sudan – Heterotis niloticus (African Arowana, filter-feeder, omnivore /
carnivore)
Saudi Arabia – tilapia, marine shrimp. Freshwater prawn, rabbitfish (Siganus
spp., marine, herbivore); water limits
Europe
Aquaculture quite widespread
Earliest records from Rome 2000 years ago - - Oysters collected
from Adriatic Sea and transferred to locations where they might
grow better
Central and Western Europe
Fish culture developed in Middle Ages (11-1400)
Common carp main species
Carp bred and cultured in monasteries
Germany, Poland, Czech, Hungary, Yugoslav. And Romania cultured
carp at significant levels
14th Century – trout culture stimulated by French monks who
developed artificial fert. Capacity
15-16th Centuries – carp culture grows in prominence (450,000 ac of
carp pronds in Bolivia, Moravia and Czech)
England
Aquaculture established 14,00-1500 AD (carp focus)
Current culture species: marine flatfishes: plaice (*Pleuronectes
platessa), Dover sole (*Solea solea) and turbot (*Scophalmus
maximus)
Blue mussel Mytilus edulis (suspension culture)
Scotland
Atlantic salmon (Salmo salar), brown trout (*Salmo trutta) in net
pens; market values often plunge for salmon when large producers
saturate the market; e.g., Nutrco (35% of total on world market)
Europe
History of strong interest in crayfish culture in Scandinavia, Austria,
Poland and Spain
Native species (Actecus) decimated by fungal disease (the plague)
1960s-70s
Crayfish imported from California: signal crayfish (*Pacificatus), and
from Louisiana: red swamp crayfish (*Procambarus clarkii); high
prices paid to U.S. producers
Spain currently major aquaculture producer in Europe – current top
species: blue mussel, rainbow trout, gilthead bream Sperus auratus
(demersal species; reared in costal ponds; also cage culture)
(demersal means near the bottom)
Norway: long fishing history – major fish eaters
Yet, fish farming began only in 1950s with 70-80 trout/salmon farms
by 1970s
Net-pen culture of salmonids prominent by late 1980s (82,000
tons/yr)
Production jumped to 170,000 tons/yr by early 1990s; now among
top producers of salmonids in world (esp. Atlantic salmon)
Currently the largest aquaculture producer in Europe; Salmon,
rainbow trout and blue mussel
Scandanavia
Denmark
o Mainly involved in trout culture: 90% rainbow trout
(*Oncorhynchus mykiss) w/ 600 farms by 1972
o Brown trout cultured mainly by exporting eggs; much global
demand for healthy BT eggs
o Trout cultured in ponds and fed “trash fish” collected from
seas (vs. pelleted feed_ due to high availability of prey fish.
France and Italy
o Also significant European producers of trout.
o France
Top culture species now: Pacific cupped osyteer
Crassostrea ariekensos, blue mussle and rainbow trout
Russia
Modest production of carp in major cities including Leningrad
2500 ac of ponds in 1970s
Sturgeon culture was prominent – mainly for caviar production
In U.S. efforts to rear white and shortnose sturgeon are ongoing;
artificial spawning and culture; high market value potential
Africa
Despite food security issues, little development of aquaculture,
particularly inland; northern nations – water limited; southern
nations = abundant water but economically limited.
U.S. AID supports efforts to increase aquaculture
Tilapia stocked at 1-2 fish/m2 agriculture byproducts fed; very
extensive w/ little to no managmenet; Clarias garipinus
High reproductive slows tilapia growth rates
Despite producing few eggs, survival very high
Stocking of Hemichromis fasiatus (predatory cichlid) often done to
control tilapia reproduction
Vs. use of mono-sex males (sex-reversal) as in more advanced
tilapia culture operations
Stocking of Hemichromis fasciatus (predatory cichlid “banded
jewelfish”) often done to control tilapia reproduction
Vs. use of mono-sex males (sex0reversal) as in more advanced
tilapia culture operations
Some trout production done in coastal Morocco
Central and South America
Historically very little aquaculture activity but rapidly increasing –
impacts on U.S.
Mexico: pond culture of common carp began – 1964 w/ 31,000 acres
of ponds, tilapia species introduced as well as grass carp
(*Clenopharyngodon idella)
Brazil: also involved in carp farming. Rearing parana and tilapia.
Great potential for increase: large freshwater supply. Soybean
production (good protein source for tilapia)
Now major exporters of “fresh” tilapia (iced) into U.S.; flown into
Miami to wholesalers
China’s subst. exports of cheap, frozen tilapia to U.S. plus C/S
American’s imports squeezes U.S. tilapia producers; few U.S. tilapia
niches exist (live market?)
Shrimp farming (*Penaeus spp. Whiteleg and blue shrimp)
developed substantially
Chile has emerged as major producer of Atlantic salmon (*Salmo
salar) in nearshore net-pens
Production comparable to Norway and Scotland, also coho salmon
(O. kisutch), rainbow trout, seaweeds (uses: food, fertilizers,
biofuels, cosmetics)
North America
Aquaculture only about 150 years old in U.S.
Oysters received earliest attention; initially harvested from public
beds by hand; 1850s
Yugoslavs settled in Louisiana brought knowledge of oyster farming,
involved harvesting and translocating small oysters in favorable
settings
Theodatus Garlick – began artifical fertilization of brook trout
(*Salvelinus fontinali) in 1853
This is key development stimulated growth of trout and salmon
culture in US and gov. fisheries
Early culture efforts were aimed at producing fish to stock natural
waters, enhance fishing activities and counter fish stock depletion
Declines in U.S. capture fisheries reported as early as 1762 striped
bass (*Morone saxatilis) and sturgeon eliminated from Exeter River
in NH, dam building had prevented alewife from spawning in NW by
1790
Privately owned hatcheries emerged 1864 Seth Green began
rearing brook trout – originally planned to rear food fish but made
more by selling eggs; hatchery building still used by NYDEC
By 1870 fish cultures practiced in 19 of 37 states
In addition to the prominenet brook trout state fish commissions
cultured Atlantic salmon, American shad (Alosa sapidissima), lake
trout (Salelinus namaycush), yellow perch (*Perca flavescens)
largemouth bass (*Micropterus salmoides) and others
Many species transported about the country – stocked well outside
their native ranges (Larval fish often stocked due to inability to rear
to later stages) (survival was assumed better in non-native
environs)
1870 a meeting of fish culturists in New York resulted in formation
of the American Fish Culture Association which later became the
American Fisheries Society
Commerical wamrwater fish culture
o Baitfish
Commericail catfish farming (channel catfish, *Ictaluris punctatus)
farming emerged in 1950s after failing efforts with buffalo and
indications at Aurburn University that catfish could be reared
profitably; fash growth, hardy species
Substantial gov’t research funding was directed towards enhancing
catfish rearing techniques in MS
Crayfish farming began in 1940s in Lousiana – industry remains
focused there today
1969: 1,300 acres 1980s: 140,000 acres
Major farmed species is red swamp crawfish (*Procarnbarus clarkii)
Lesser involvement in: MO, TX, MS, NC, SC and AR
Hint: know order oa appearance of catfish, crayfish, baitfish and
brook trout production in U.S.
o Baitfish, crayfish, catfish
Canada and Alaska
Japanese Oyster (*Crassostrea gigas) culture practiced as early as
1912 in British Columbia with seed imported from Japan
Freshwater trout farming began in 1950s
Salmon culture emerged in 1970s. Pacific salmon; coho
(*Oncorhynchus kisutch) Chinook (O. tshawytscha), rainbow trout
(O. mykiss) and the Atlantic salmon (Salmo salar) are major species
cultured
1984 – 10 licensed salmon farms along B.C. coast – over 170 by late
80s
Atlantic Salmon most prominent salmon species cultured on Pacific
Coast
Basis for Aquaculture
World human population growing exponentially:
Population “doubling times”; 1700s (230 years); 1800s (100 years);
since 1950 (37 years)!
Population increased from 2.5 billion in 1950 to 6.1 billion by
2000Recently growing nearly 90 million annually (about like adding
a new U.S. every 3 years)Despite slowing trends, population
expected to continue rapid increase possibly reaching 10-12 billion
before leveling off as 2050 its approached
Global birth rate is 27/1000 people and death rate is 10/1000 per
year
Trends in per Capita Consumption
In addition to population size, per capita consumption also
influences the strain placed on world’s essential resources (water,
food, energy) by the human population
Global demand for food is increasing to a large extent b/c of
exponential human population growth, but also substantially b/c of
increasing per capita demand.
Grain does not account for all sources of human food but its
availability is a good, global-scale barometer of food availability for
humans.
Grain consumption
Developing countries: 400# / person /yr. here grain is largely
consumed directly
Developed countries: 2000# / person, <10% being directly
consumed, mostly eaten in form of animals that were fed grain.
Associated efficiencies of grain to protein conversion; beef: 31%,
pork 56%, poultry 71% (wasting protein)
As countries develop and become more affluent, they include more
animal products in their diet thus further increasing demand on
world grain supply.
Increased demand for grain contributes to higher prices and may
negatively affect availability to poorer countries parallel situation
with aquatic species consumed e.g. eating salmon vs. carp
Only 30% of world’s land is suitable for food production (crop,
rearing and grazing by food animals)
Increase land production?
Increase land area farmed
Increase yields on existing farm land by multi-cropping, fertilizing
and imgating, use of pesticides
Negative environmental impacts
o Overuse of water supply
o Loss of high quality farm land
o Pollution impacts
Alternative food sources
Single cell proteins from algae, yeasts and bacteria
Fish Protein Concentrate
o Contains high-density fish protein
o Aimed at using underexploited fish stocks
o Species used: hake, menhaden, herring, anchovy, alewife,
ocean pout (oily; high fat)
o Expt. Facility in MA produced 7.5 tons of FPC from 50 tons of
fish per 24 h.
1/23/09 11:56 AM
Hydroponics
Growing plants in nutrient solutions (water) as opposed to soil;
minimal land requirement
Liquid hydroponic systems have no medium for mechanical support
of plant; aggregate systems incorporate support medium (sand,
gravel, rockwool)
Potential for high productivity, conservation of water, minimal land
requirement and environmental impacts
Systems that include fish as nutrient source for plants have
received attention (fish feeds sometimes used)
Hydroponics has had multiple upstarts since late 1800s; though
believed to hold good potential, has not reached potential to date.
Consumption of Fish
~20% of global protein consumption as fish
Mean, global per capita fish consumption; 12 kg (27 lbs/person/yr)
Highly variable by world region:
o Europeans and Asians consume fish regularly
o Greatest fish consumers: Iceland (196 lbs/yr), Japan (164),
Denmark (89)
o Latin America variable: Brazil, Cuba, Mexico: low levels (<20
lbs); signif. Higher in Panama.
o Middle East and Africa: generally low; higher in coastal areas
Consumption of Fish in U.S.
Beef and pork historically most importantn animal protein in diet
(100-150 lbs/person/yr)
Poultry: 40-60 lbs (globally, has surpassed beef)
Fish: distant 4th (10-15 lbs); tendency to focus on high-value species
(salmon, shrimp); eaten more for taste than as a source of protein
Low fish consumption in U.S. has impeded growth of U.S.
aquaculture industry
Fish protein content similar to beef and chicken (18%) and higher
than pork (10%)
Fish generally have low fat content similar to chicken (<5%); less
than beef and pork (10-18%); beef and pork fats being reduced
Fish have lower caloric density due to lower fat (2 cal/g for RBT)
than beef (27) and pork (51); similar to chicken
Fish, crustaceans, mollusks 90%-100% digestible due to high ratio
of muscle protein: connective tissue, relative to mammals
Fish low in cholesterol relative to beef and poultry; high in omega-3
PUFAs; believed to reduce arterial sclerosis; enhance brain function)
Some “shellfish” (lobster) higher cholesterol
Fish vitamin rich: A,D (fish liver oil), B complex; also good sources of P, K, Fe,
Ca, Mg and Cl, trace minerals
Four Compositional Groups of Fish
Low fat / high protein (<5%/>15%): channel catfish, lobster, shrimp,
RBT, tuna
Medium fat (5-15%) / high protein: Pacific and Atlantic salmon
High fat / low protein (>15%/<15%): lake trout, herring, mackerel,
sardine
Low fat / low protein: Oysters and clams
Very high energy fish: eel (17% fat)
High protein fish: yellowfin tuna (34%)
Situation with Capture Fisheries
Oceans cover 70% of world’s surface; freshwater lakes and streams
cover only 0.4%
Common view as recently as ~1950s was that overuse/depletion of
marine fishery resources was unlikely to impossible
In fact, open ocean areas (90% of total) are low in productivity due
to low nutrient supply; levels of photosynthesis (algae production) –
the base of fish production are generally low here
Situation with Capture Fisheries
Nearshore marine areas e.g., estuaries, shallow continental shelf
zones, certain upwelling areas where nutrients vertically
transported to upper, warmer waters are the most productive areas
(10% of ocean surface)
Estimates of instantaneous total available fishery products from all
oceans: 220-275 mmt
However, much less than this amount is available in a sustainable
way
Situation with Capture Fisheries
Estimates of sustainable yield of fishery products from all oceans
(more meaningful) range from 75-150 mmt/year
Higher sustainable yields have been thought possible, if lower-food-
chain marine organism were targeted also (e.g., krill in Antarctic –
bad idea!)
Implication from harvest curve is that we’re extracting all that we
can from world’s capture fisheries
Likely we are harvesting above sustainable levels b/c despite
increasing fishing effort harvest is showing indications of decline
In reality, to maintain harvest of about ~90 mmt/yr we are “fishing-
down” many populations to “economic extinction” then jumping to
the next most available population (“fishing up”)
Economic extinction: costs can not be recouped on fishing
population
also targeting smaller and smaller fish
Fishing pressure
Harvest increases, stimulates fish production
Increase slows, approaching max sustainable level
MSY = max sustainable yield (anything past is, called overfishing)
Harvest downturns, harvesting beyond replacement capacity
Drops rapidly increase
“Fishing down” the population
Situation with capture fisheries
FAO data indicated that 50^ of FRPs have been overexploited
(fished down), while about 25% are fully exploited or in early stages
of overexploitation
Only about 25% of FRPs are considered underexploited (recent
Science article – 2040)
Note!: fished-down FRPs often don’t rebound for long periods after
fishing pressure is relaxed due to bio-ecological reasons
Also, any signs of modest population recovery often bring about
renewed fishing pressure
Influences on aquaculture’s growth
Environmental impacts from aquaculture: as aquaculture grows, an
environmentally concerned public keeps watch
Logic suggest that aquaculture should avoid rearing carnivorous
species (salmon, trout, cod, halibut, tuna, walleye, perch, HSB, LMB,
but rearing of carnivores is increasing fast due to high demand and
profit potential
At current rates of increasing carnivore production supplies of fish
(high-fat species) for fish oil and fish meal projected to be
extinguished by 2010 and 2050
Aquaculture thought to “spare” capture fishery species, but has
increased overfishing of some; already extending to additional
species: mackerel, herring, shifting. Norway pout and krill; fishmeal
prices will increase
General points
World harvest from capture fisheries has fluctuated annually since
1996 around 90 MMT/ YR
Total harvest from aquaculture has shown a steady increase since
1996, reaching 37.5 MMT in 2005
Currently about 30% of total harvest comes from aquaculture,
while 70% comes from CFs
75% of total fish harvest going to human consumption 25% going to
animal production
Per capital availability of fish has been increasing reaching 35.7 lbs
per person per year
China’s Major influence
Accounts for 18% of capture fisheries
Aquaculture harvest 69% and total harvest 33%
China believed to be overstating their harvest levels from all
sources, such that globally we’re not as well off as we think
Without china, no increase in world harvest since 1988
Suitability of aquatic organisms for culture in any rearing setting is critical to
success and depends on many factors.
General: a species may have high market value but not be
economical due to high competition from other producers (e.g.
yellow perch) or due to requirement of conditions/resources not
available (e.g., rainbow trout which require continuous high
volumes of cold water)
Alternatively, local conditions may be ideal to rearing a species but
acceptability/demand may be low (e.g. Macrobrachium – rw prawn)
Typically, only well-established producers able to “test the waters”
for a new culture species (Kahrs have profited greatly with
paddlefish but had firm base prior to that)
Many culture aspects may be favorable for rearing a species in a
given setting but a single weakness may be economically fatal
E.g., many MO producers must “live haul” their products to market:
this 1 increases operational costs (hauling truck, travel costs,
personnel) 2 renders some culture species infeasible to due to long
distances to major buyers
Curt Harrison has established purchase agreements (paid good
prices) with Chicago fish housing plants.
Selected species must be amendable to culture conditions
examples of “problems”
E.g., some MO entrepreneurs invested in large, recirculation
systems (RASs) and started by rearing walleye (have high market
value in northern Midwest)
Walleye present severe probelsm due to cannibalism (must size
grade, keep satiated); growers lost initial product and whole facility
due to insufficient research hybrid walleye better choice)
Must interest in rearing crappie – strong demand – but species
prone to becoming overstressed at harvest and
Temperature: many culture species eurythermal, but most grow
optimally only with a narrow temp. range e.g., 4-5C
E.g. bluegill survive and exhibit some growth from 4-31C (39-88F),
but grow best at 22-26C
To be competitive, must be able to provide optimal temp to growth
of species for substantial portions of year
This is why advantages exist for certain species at different
latitudes in ponds e.g. perch / walleye to north: bluegill to south
Maintaining constant favorable temps possible with, heated
effluents, springs, underground, indoor pools
Biological considerations
Temperature: optimal-growth temperature ranges for juvenile fishes
are typically higher than for adult stages (7C)
Water quality:
o In addition to temperature, DO, ammonia (NH3) and nitrite
(NO2) are often the most critical water quality parameters in
aquaculture (DO monitored daily)
o Range of tolerance for DO: trout species typically require >5-6
mg/L and so require large volumes of cold water for
production; tilapia can tolerate <1 mg/L DO
o Ammonia is excreted over the gills in fish and is toxic. It is
readily broken down to nitrite by de-nitrifying bacteria (less
toxic) causing brown-blood disease, and then to non-toxic
nitrate
Salinity: Many culture species grow best in either fresh-brackish- or
sualt water (35 ppt) a few species grow well over a wide range of
salinity
Some species cultured at extremes of tolerance range to produce
other benefits e.g. channel catfish reared at 6 ppt as this reduces
off-flavor problems, negates reproduction in ponds, no effect on
growth
Natural feed:
Blankton, macrophytes, benthos, detritus, molluscs and other
smaller animal species
Prepared (artificial) feed:
Complete diets supply all the nutrients necessary
Importance
Supplies nutrients required for optimal growth
Increases fish production
Also, reduces culture period as fish gains body weight at their
maximum potential
o Feed costs 40-60% of operational costs in fish farming
Major components of a feed
Complete feed
o Water
nutrients
Dry matter
Inorganic
o Minterals (salts)
Organic
o Proteins, lipids, carbohydrates
Nutrients
Nutrients are organicia nad inorganic compounds needed to support
essential life processes
Nutrient is considered to be essential if an animal can not
synthesize them – has to be provided via food.
Proteins
Made up of amino acids
Fish consume protein to build new proteins (as during growth and
reproduction) to replace existing proteins (maintenance)
Protein also serves as an energy source
Essential amino acids vs. Non essential amino acids
EAA – fish can not synthesis
Carbohydrates
Carbohydrates are compounds made up of sugars
Function: Sources of energy
Fish, particularly carnivores, are not efficient in utilizing
carbohydrates as energy
Classified by size
o Monosaccharides / simple sugars (glucose)
o Disaccharides (sucrose)
o Oligosaccarides and polysaccarides
Lipid
Five major classes: fatty acids, triglycerides
Phospholipids, sterols and sphingolipids
o Functions
Source of energy
Components of cell membranes
Serve as a vehicle for the absorption of fat-soluble
vitamins
Vitamins
Required for normal metabolism, and normal biological functions
Vitamin deficiency causes growth deficiency
Minerals
Needed for the formation of bones, scales, teeth, etc and for many
physiological functions
E.g. Calcium, phosphorous, sodium, chloride, etc
Fish can absorb part of the required minerals from water through
gills
Energy terms
Intake energy: gross energy content of food soruces
Digestible energy: difference between gross enerhy and energy
available to animals
Metabolizable energy: Difference between digestible energy and
energy lost
Feedstuff
Feed incredient suitable for production of animal feed
Sources of nutrients
Protein rich foodstuffs:
o Animal protein sources
o Plant protein sources
Energy rich feedstuffs: corn, wheat, oil
Fish meal: ground product of dried, defatted fish or fish processing
waste
Pultry by-product meal: made from rendered parts of slaughtered
poultry
Types of GI Tract
Herbivores
o Small stomaches and long intestine
Tilapia
Car
Omnivores
o Moderate size stomach and intestine
Catfish
Piscivores/Carnivores
o Large stomach and short intestine
Trout
Striped bass
Factors in choosing feedstuff
Nutrient content
Digestibility
Price
Availability of feedstuff at your area
Palatability
Feed types
Floating pellets, slow sinking pellets
Diets for different life stages (2-3 diets)
o Fry feed
o Fingerling feed
o Adult feed
Juvenile level: high protein
Importance for providing right amount dietary nutrients
Provides optimum growth and health
Reduces feed cost and feed waste
Reduces nutrient pollution
Biological Considerations
Biological Considerations
o Growth Rate
In general, fast-growing species preferred in
aquaculture
Less obvious benefit of faster growing species is
reduced risk of “crop” loss
Investment in a crop increases exponentially as the
growth period progresses
But-so does the likelihood of mass mortality as the
increasing fish biomass approaches CC of system
Acceptable maximum grow-out time (growing
juveniles/fingerlings to larger market size) in U.S. is
typically two years (e.g., blugills)
High-value, slower-growing species (>2 years) are
sometimes still reared b/c high prices paid; offsets
“risks” of longer rearing times
E.g., Signal crayfish (Pacificus leniusculus) takes up to
three years to rear, but commands high market values,
producers more likely to take risk
Fast growing
Red swamp crawfish
Hatch to market size: 3 months
Paddlefish
Polyodon spathula – ave. 2.2 lb weight gain
per month (in ponds vs. rivers)
Grass carp 1.1 lb per month under ideal conditions
(note: MO producers unable to maintain fast grass
carp growth for long, due to running out of pond
veg. need prepared diet; larger fish desired; tier
method – Paula Moore
Even fast-growing species reach natural slow-down
points – usually association with maturation; slower
growth continues
Often, culture species are harvested once “slow-down”
point reached, to avoid loss of time efficiency
E.g. recall milkfish grow rapidly to 1 lb and then slow
down, commonly harvested at 1 lb despite capacity to
reach 10 lbs
Main Points – faster-growing species are generally
advantageous (time efficient, less risk) but there is
sometimes good reason to rear slower growers market
size etc
o Feeds and Feeding – preliminary points
Must be able to accommodate a culture species’ shifting
nutritional needs with life stage
Protein and energy requirement change with stage –
often, only generic diets available – too little P&E for
young, too much for older fish (e.g. fatty liver problem)
Local e.g. Currently can rear LMB well with available
prepared foods (e.g. trout diet) to .75 to 1 lb range
When intensively rearing early life stages of finned fish,
precise sizes/species of zooplankton must be provided
post yolk-sac absorption
Must be in proper sequence to avoid tendency for
starvation (point of no return)
“brine shrimp” (Artemia) are often provided towards
end of feeding sequence to “transition” young fish onto
prepared feeds
Situation much simplified for some culture species like
(shellfish and crayfish) that remain on natural feeds
throughout all life station
o Reproduction
Often, undesirable for culture species to reproduce
during grow-out phase (occurs mainly in earthen pond
culture)
Why? Growth rates of larger fish (maturing/adult)
impeded by competition from vast numbers of young for
natural pond foods (zoop. Algae, benthos)
Natural foods important in ponds b/c prepared diets are
often “incomplete” – required nutrients provided
As young grow they may also compete with larger fish
for prepared feeds as well
Monosex populations, male-skewed hybrids, or sterile
triploid populations, commonly used to prevent
minimize in pond reproduction
Advantageous that culture species reach market size
before maturation
Developing monosex populations of the later maturing
sex improves growth rate
Use of MT, TBA, estradiols common for “sex reversal”
Hardiness – ability to tolerate culture conditions – high
rearing density, periods of poor WQ, handling,
harvesting, incomplete feeds, disease resistant
In nature, food supply defines carrying capacity of
aquatic environments; restricts fish population densities
from becoming too high
For many species, group rearing promotes aggressive
social interaction among fish, can result in graded
dominance hierarchies where “dominant” )often larger)
fish eat well and lower status fish “trained” to eat less
subordinated fish may carry high stress loads (MET
costs) Arctic char an exception
Social costs reduce average growth rate (20% in
sunfish) cause low Fes and much size disparity
1/23/09 11:56 AM
Biological Consideration
Hardiness con’t
For many species, group rearing promotes aggressive social
interaction among fish
Can result in graded dominance hierarchies where “dominant”
(often larger) fish eat well and lower status fish “trained” to eat
less; subordinated fish may carry high stress loads (MET costs);
Arctic char an exception
Social costs reduce average growth rate (e.g. ~30% in sunfish),
cause low Fes, and fish size variation
Size grading sometimes reduces hierarchies but does not eliminate
totally; extreme high density rearing and forced swimming also can
be effective as can duoculture and cull-harvesting (aka – “topping
off”)
Despite strong efforts to maintain high water quality in intensive
culture, breaches are common
Culture species that will tolerate episodes of low DO, temperature
swings, increased NH3-nitrite-nitrate, will perform better overall.
Fish that are less stressed under intensive culture conditions are
less prone to disease/mortality (e.g., blue catfish x channel catfish
hybrid)
Further considerations in culture-species selection
Productivity: aim is to achieve high production of culture species in
form that is marketable.
If only 2+lb fish are marketable and less than 50% of all you rear
reach this size within grow-out time limit, this may be inadequate
for “profitability”
Unless high market price allows this inefficiency (common
impediment for “emerging” culture species industry facing this
problem with raising large food-size sunfish.
Marketing Consideration
Rearing culture species that have diverse markets tends to reduce
risk and increase profit potential
E.g., channel catfish can be sold as; fingerlings; food fish; for private
pond stocking (various sizes), for fee-fishing; as brood stock; for by-
products (catfish oil for crayfish bait); for feeds: carcass and viscera
to feed mills.
Contrast with producer with 2,000,000 small bluegills
Considerations
Channel catfish
o Rapid growth of industry in SE U.S. after 1960s (210,000
metric tonnes as of 1993) increased further – now declining –
represents ½ U.S. production
o Vs. 2.9 mmt for silver carp
o Spawn in captivity at 21C (70F) fail to spawn at higher temps
and elevated salinity (2-11 ppt) but still grow well under these
condictions
o Fignerlings stocked in grow-out ponds
o Fed daily with prepared diet
Cull harvesting now more common than batch harvesting
o Batch harvesting ponds drained all fish removed
o Cull harvesting only larger market size fish removed by size
selecting seining every 3 weeks ponds not drained one
fingerling stocked for ever lb removed
o Culling promotes more consistent supply of marketable fish
o Reduced water use reduced environmental impact
o Culling might reduce social hierarchies
Typical pond production: 10,000 lbs/acre/yr
Sales to: processing plants; local stores-restaurants; liver haulers;
backyard sales; fee-fishing; niche markets (local grocery stores,
rest)
Summer water quality problems; DO swings (extremes at mid-day
vs. sunrise-why?) late afternoon prediction/aeration
NH3 to nitrite *causes brown blood disease) – nitrite binds with
hemoglobin producing methemoglobin – poor O2 transport
Brown blood common in spring/fall? Heavier feeding produces more
NH3 then nitrite (less efficient at warm temps)
Water quality problems cont
o Off flavor problem is major issue
o Common source of origin – fish eat decaying feed/OM on pond
bottom when feed supply insufficient for satiation (salinity /
depuration)
o Common disease – Enteric septicemia (bacterium targeting
fingerling channel catfish) GI tract ailment) =- antibiotic
treatment
o Note: recent study apply our CG-inducing off/on feeding
resulted in reduced presence of ESC in challenged fingerling
CC
o Blue and white catfish grown to lesser extent than channel
catfish (CC) in US Why?
o White catfish – slower growing low “dress-out weight” weight
when gutted, head off / whole fish weight due to large head
o Blue catfish – high dress out (60%) less size variation than CC;
slower 1st year growth; but grows larger than CC in 2nd yr
BC x CC hybrid
o Bc x cc hybrid shows substantial “hybrid vigor” (hardiness
traits) in pond settings
o Tolerates crowding well (possibly due to low aggressiveness)
o Disease tolerant
o High feed efficiency (FE = wt. gain / feed provided; FCR =
1/FE (MUST BE ABLE TO CALCULATE) higher FE is better, lower
FCR is better
o Fe is feed efficiency
o Fcr = feed conversion ratio
o Problems with producing seed stock – insufficient availability
of hybrid
Yellow and brown bullhead (I. natalis, I nebulosus); slow growth is major
impediment – however –
Flathead catfish (Pylodictus olivaris); highly piscivorous aspect is a drawback
(cannibalism)
Clarias bactachus (walking catfish in FL) and C. macrocepalus highly valued
culture species in SE Asia / India – tolerates low DO high density rearing frow
well on fish scraps and rice
Clarias gariepinus reared at subsistence levels in Africa – also reared in
Other catfish
Pangasius spp – reared in Asia, India-China in floating cages
6” fingerlings reach 2.25lbs in 8-10 months
Pangasius spp. Also reared in polyculture with Oreochromis niloticus
in Thailand – wild fly captured in rivers
Siluris glanis (sheatfish; Wels catfish) reared in Europe – used as
provider
Heterobranchus bidorsalis = highly prized culture species in Liberia, reared
in combination with O niloticus
Rhamdia spp. Catfish species receiving some attention in Brazil
Tilapia Culture
Tilapia is general name for group of cichild fishes endemic to Africa
and Middle East
Tilapia laterally-compressed body shape resembling U.S. sunfish –
this similarity was exploited early on for market purposes in U.S.
(fish species recognition is important to product acceptance)
Tilapia fishes used in aquaculture comprise 3 genera: Oreochromis,
Tilapia and Sarotherodon
Tilapia are nest builders; fertilized eggs guarded by parent (often
male)
In Oreochromis and Sarotherodon, additional parental care is given
via “mouth brooding” of eggs to post-hatch stage
Major positive features of Tilapia for aquaculture (FOR TEST)
o High tolerance of poor water quality
o Ability to use broad range of natural food organism –
important extensive and intensive culture in ponds
Major constraining features (FOR TEST)
o Inability to tolerate cold water (50-53F)
o Early sexual maturation leading to unwanted reproduction in
ponds – overcrowding, stunting, marked size variation, slow
growth
o Predator stocking is common in extensive pond culture for
control (e.g. Clarias Hemichromis)
o Primary large-scale culture species are Nile tilapia (O.
niloticus), followed by blue tilapia (O aureus) and
Mossambique tilapia (O. mossambica); hybrids have become
common in part for preferred color, high % male (faster
growth vs. female)
Production
o Annual global production of Tilapia – 1.5 Million tons/year;
among cultured finned-fishes 2nd only to Chinese carps
o International trade of Tilapia growing rapidly
o Major producers – Central America (Costa Rica, Ecuador,
Honduras) – exporting mainly to U.S.
o Major Asian producers (Taiwan, China, Indonesia, Thailand)
also export to U.S. and Japan
o Largest exporter (Taiwan) supplies high-quality fillets to Japan
for Sashimi market
o Taiwan also supplies frozen Tilapia to U.S. (40,000 tons/yr)
China also exports 12,500 tons/year of frozen Tilapia in US
o Zimbabwe and Viet Nam recently entered global market as
exporters
o Tilapia now 3rd highest imported aquaculture product to U.S.,
behind only shrimp and salmon
o Exporting of Tilapia to Europe has begun with vast increases
U.S. Perspective
o In general, Tilapia are imported to U.S. from Asia as frozen
whole fish or fillets
o Mainly fresh fillets are imported from Latin Americato US. Via
airfreight into Miami, then to U.S. distributors
o This leaves “live Tilapia” as the primary “open Tilapia niche”
for U.S. growers
o US consumption of Tilapia surpassed rainbow trout in 1994
only salmon and catfish exceed Tilapia for finned-fish
consumption
o 17 million labs (8,500 tons) of Tilapia produced annually in
U.S; 2 million lbs (12%) produced in Midwest (ND – in RASs);
6.7 million pounds (highest) in CA (39%)
o among most rapidly increasing culture species
o Three major Tilapia species are grown in the U.S. plus hybrids
(differences in: low-temp, tolerance limit, color, % male fish)
Grown in every state, either in ponds, cages in ponds, RASs
(indoor tanks)
In Midwest most Tilapia grown in RASs due mainly to
temperature constraint; also eliminates reproduction problem
– why? No substrate
o Major markets: NYC, Toronto, DC, Los Angeles, San Fran,
Seattle
o Substantially untapped domestic market potential through to
exist in Chicago, STL, KC, Atlanta, Denver, Soutwest USA
Recommendations for Midwest Tilapia Producers
o Feeds/Nutrition:
Complete feeds needed for Tilapia rearing in RASs –
why?
No nutrients in RAS, must provide
Also less solid wastes by 1 reducing waste feed 2
increasing feed digestibility (% digestibility of feed
components often not determined)
Compensatory Growth Studies at MU – Examining two impediments to fuller
use of CG in fish culture:
Compensatory growth
o Natural capacity of fish to undergo a period of rapid, catch up
growth once food supply recovers after a period of low
availability
Culture Systems
Ponds
o Usually earthen, sometimes concrete water impounding
structures: liners now common
o For aquaculture, ponds typically in range of 0.5-10 surface
acres.
o Largely closed systems; water added at filling, and
periodically to compensate evaporative loss and seepage;
draw-downs needed on occasion (harvest, repair, mud
removal)
o Few ponds have continuous, low-level flow-through e.g., well-
known KS pond with very high catfish production.
o Favorable attributes:
Relatively few legal/social concerns if privately owned
Effluent impacts tend to be low, esp. if complete draw-
down is not done frequently
Natural foods in ponds supplement prepared diet (fare,
complete diets less required)
Lower “fish” densities vs. other culture systems:
reduces disease and parasite problems
Nutrient rich pond water can be applied to agriculture
land crops (integrated aquaculture)
o Less favorable aspects:
Large land area required
Construction costs can be high (heavy equipment
required)
Periodic maintenance required: mowing of levees,
repairing leaks
Require maintenance/storage facility for farm
equipment, harvesting gear
Large supply of good-quality water needed to fill; may
require digging of wells (costly)
Costly to treat disease due to high, static water volume
Very limited control over water environment: temp., DO,
introductions, preds/pests, reproduction (vs. e.g., tanks,
raceways
Harvesting requires equipment, personnel, time
consuming
Difficult to “stage” production (serial harvesting:
continuous supply of marketable fish) multiple harvests
costly; non-continuous growing season
o Pond Types
Watershed pond – constructed on rolling land by
damming at a strategic location; (+) no digging; filled
by run-off (inexpensive); (-) uneven bottom impedes
seining; but, suitable for cage culture
Excavated pond – dug below ground level; no levees
constructed (borrow-pit ponds: common along
highways) usually filled by rainwater
Usually not constructed with aquaculture in mind; yet,
may be suitable for cage culture and spotfisheries (OH
program);
Problems pollutants from highway and public access
Embankment ponds (levee pond) – contructed by
excavation: removed soil used to build levees (banks);
built on flat land
Water supplied from wells or by pumping from
nearby stream / often have drain and inflow pipes
Top choice of inland fish farms – good control over
filling/draining; size, shape, depth by design vs.
“what you get”
Marsh Pond – constructed in coastal marsh areas; ponds
dug and levees constructed; often filled and drained by
pumping; water salinity variable;
Sometimes with weirs (low-level dams that allow
tidal water inflow/outflow w/o loss of culture
species or intro of unwanted species)
Beach pond – constructed in sandy coastal areas; water
seepage reduced by liners; sometimes made of
concrete; common in Taiwan, Indonesia, other island
nations for rearing salt- and brackish-water species
(shrimp, milkfish) weirs common – 2005? Tsunami
Intertidal pond
Located just offshore in marine cove or bay,
blocked off by levee (net or rock piles); water
interchange with tide; levees used to contain
culture species; common in Hawaii
Cage Culture
o Cage culture practiced for many species; not just salmon (net
pens are cages)
o In U.S. these include bluegill and hybrid BG, hybrid striped
bass, channel catfish, tilapia, many others
o Cage culture also very prominent outside of U.S. – globally
one of the fastest-growing aquaculture rearing systems – e.g.,
cages in many impoundments in China
o Small farm ponds and lakes not designed for AQC often well-
suited for cage culture
o Unlike in ocean, water currents in ponds, impounds often
don’t facilitate movement of water and wastes, out of cages 0
creates substantial risk.
Benefits of Cage Culture
o Can be applied in water bodies not suited for conventional
harvest methods (e.g. where seining/pond draining not
possible)
o Can readily observe fish in cage – helps to gauge feeding
rates, assess growth, identify disease onset, WQ problems,
incipient mortality
o Ease of harvesting – important as harvesting of ponds
requires time and expensive equipment
o Can facilitate due culture – cage rear one species rear another
in the poen pond can feed both groups separately rear
predators (out) and prey (in)
Downside
o Increased potential (vs. open-pond rearing) for water-quality-
related stress (death) on fish b/c restricted (laterally and
vertically)
o Fish can’t escape cage conditions, fish in open pond have
much advantage – WQ in open pond usually better vs. cage;
fish can seek viable micro-environs in ponds
o High fish density increases likelihood of disease
o Close proximity can promote agonistic social interaction
(competition) leading to growth dispensation and substantial
size variation at harvest, yet some species may show more
uniform growth (e.g., Large mouth bass, hybrid blue gill?)
o High potential for predator problems and theft
Cages
o Agriculture and fish farming supply companies sell cages (or
construction materials)
o Common configurations: cylindrical, square, rectangular
4ft deep for winter/summer
o Common frame material: wood, iron, steel, aluminum,
fiberglass, PVC
o A depth allows fish to access cooler water, avoids access to
pond bottom, poor WQ
Points
o Overall stocking densities in open pond setting (3,000-8000
catfish/pond acre) are greater than for caged fish (2,000-
4000); production levels (lbs/acre, kg/ha) parallel stocking
densities
o Why? The water volume available for fish production is lower
in cage-culture than in open-pond setting, even when max #
cages used
o Pond/cage, Density Comparison; catfish in open pond =
0.02fish/ft3 cage = 1.5 fish/ft3 (75x)
o Tilapia in cages = 6 fish / ft3 this becomes very crowded as
fish reach final sizes
Cages- DO
o DO levels in cage will drop quickly if water exchange is not
sufficient
o On calm days DO outside of cage may be good, but not so
inside, continual water movement in/out of cage is critical.
o Situating a aerator close to cage can promote water flow
through, too close can stress fish, air lift pumps located inside
cages have shown much promise (quiet, efficient)
o Conditions where DO must be carefully monitored in cages,
summer in general 24 h DO swings, low-ind periods, cloudy
weather (limited photosynthesis/algae respire, summer t-
storms, plankton die-off (id by loss of greenish color) plankton
decay has BOD
o Cages should be located where emergency airation can occur
o At least 4ft deep to allow fish to escape warm water in
summer and water too cold in winter
o Alkalinity of pond with cages should be maintained at >50
ppm CACO3 buffer against nitrification process
o Biofouling of cages from algal buildup. Bryozoans is common
and must be countered, high pressure washing small sock of
CuSO4, other herbicides used
o More complete diets appropriate – reduced access to natural
foods (unless fish are plankton feeders)
o Use of floating vs sinking feeds beneficial in cages
o Feeding rings used PVC to keep feed from exiting cage from
feeding activity wind
o Still, feed and feces tend to accumulate on bottom below cage
caused localized WQ problems, “diaper” small mesh net
situated below cage) often used for periodic removal of waste
feed and feces
o During summer (favorable growth period) feeding more than
one daily beneficial for many species growth; season max
feed amounts for ponds usually known.
o Rectangular cages with long side facing prevailing winds
maximized water circulation through cage
o Cage mesh size of > 0.5 inch recommended – due to
biofouling – consiquences usually start with larger fish in
cage-culture vs. open-pond rearing
o Cages should be at least two feet off bottom
o Minimum distance of 15 ft between cages
o Cages may be anchored to bottom or attached at intervals to
rope stretch across pond
o Placing multiple cages around a pier can limit flow
Salmon aquaculture – major species
o Atlantic salmon: single species: Salmo salar (Atlantic salmon)
o Pacific salmon: Major culture species
o Pink salmon (oncorhynchus gorbuscha)
o Sockeye (O. nerka) [Kokaneese, freshwater race]
o Coho (silver) (O. kisutch)
o Chinook (spring, king) (O. tshawytscha)
o Shum (O. keta)
General background
o Anadromous, coldwater species
o Pacific salmon are semelparous
Go to ocean, mature, come back 2,3,4 years, spawn,
die. Nutrients from body provide nutrients to young.
o Atlantic salmon are iteroparous
Spawn 2-4 times
o Culture techniques well developed due to long history as high-
value sport and commercial sp.
o E.g., many federal hatcheries for pacific salmon on U.S. west
coast to counter population declines (overfishing, dams
impeding upstream (adults) / downstream *(smolt)
movement, domestication)
o Majro commercial production of salmon in: Japan, Norway,
Scotland, Ireland, Chile, Canada, Maine, U.S. west coast
o Culture systems used: ponds, raceways, nearshore net-pens,
ocean ranching, open-ocean pens/cages
o Commercial salmon farming on U.S. west coast under much
scrutiny – likely arising from competition with capture fishery
communities
o Some of salmon culture’s blame for negative environmental
impacts likely emanates from commercial fishers being out-
competed
Ocean Ranching
o Popular in Oregon, Alaska (Prince William Sound)
o Facing much criticism b/c “domesticated fish” are
intentionally released into ocean – believed to be diluting the
“wild fish” gene pool
o Pink salmon is major species in salmon ranching
General process
o Returning brood fish selected for quality “hand-stripped” eggs
and milt for artificial spawning: wild fish often marked by
DNRs to distinguish from “ranching” fish
o Indoor jar-hatching of eggs – fish offered prepared floating
diet near swim-up phase (small feed particles feed frequently,
e.g. 5x per hour)
o Feeding of larger fingerlings typically in land-based
tanks/pens with freshwater until saltwater phase is reaching
*duration of fw phase varies among species)
o Fish in sw phase released into ocean; return within 1-2 years
and harvested
o Most growth occurs free of charge, courtesy of ocean number
of fish returning highly valuable
Net-pens and raceways
o Floating nearshore net-pens have become most common
culture system for salmon
o Complete ground-based Atlantic salmon culture using
raceways containing pumped saltwater still done in some
areas (nearshore)
Atlantic salmon culture
o 100 year history
o parr: early juvenile freshwater phase (vertical bars on fish
called “parr marks”)
o smolts – smolt stage is reached as fish begin to enter
saltwater phase and in nature begin to migrate downstream
to sea (silvery color develops)
o 1st year at sea fish called grilse
o in nature atlantic salmon have returned to freshwater up to
five times to spawn (2-3 times typical)
o typical culture sequence for Atlantic salmon
o broodfish artificially spawned in hatchery – young are feed
trained at 1-2 inches, parr stocked into outdoor, freshwater
tanks with feeding
o smolt stage reached in 1-2 years (fairly protracted freshwater
phase) fish then stocked into floating saltwater net pens
o within 1-2 more years, marketable fish are produced (4-10
lbs)
o Most popular of culture species is
o Fry to smolt survival rates : nature <1%
Culture: >80%
o In saltwater phase (net pens), viable temp. range is typically
31-60f
o Below31f freezing occurs, above 60F growth favorable, but
lower DO and higher temps promote stress/disease
o In east coats U.S. waters, temperature ranges limit number of
desirable sites
o Survival rates in saltwater phase >90% (in net-pens)
o Predation by birds and seals are a major problem-storms
impair predator exclusion nets
o For netpen systems FCRs of 1.3 have been achieved (Fes of
1/1.3 = 0.77; ideally ~1.0
o Much research done on feeds (for all life stages) and feeding
strategies; protein:fat ratios for life stages
o Selective breeding done to improve FCR
o Underwater video used to reduce waste feed (waste feed
costly, water quality impacts)
o Two aspects to feed efficiency
Amount of feed thrown that gets consumed
Part of that going into growth
o Selective breeding
Has led to most major improvements in Atlantic salmon
culture; growth rates, FCR, flesh color, disease
resistance
Fish/shellfish have higher genetic variance among
individuals and higher recundity than farmed land
animals – allows higher selection intensity for favorable
traits in aquaculture
Useful changes within 2 generations are common
Mono-sex female populations commonly reared for
faster-growth; new marketing approach (Organic
Rearing) directed towards reducing sex hormone use
(e.g. estrodiols)
Brood stock rotation (to reduce degreee or
domestication of fish_ is practiced to reduce
susceptibility to disease in net pens)
Pink salmon (O. gorbuscha)
Named for pink-colored flesh
Negligible freshwater phase 0 young fish go quickly to sea (few
weeks)
Typically reach 4-6 lbs within 2 years of hatching.
Major “ocean ranching” species
Few fw phase means little early investment (e.g., feed costs)
Small initial investment allows risking poor returns in some years
Culture hardy; first salmon species reared in net-pen culture on U.S.
west coast
Popular in European sea-farming
Matures early in the grilse stage – slowing growth
Consequently, cultured to smaller “pan-sized” (12 oz.) within 6-8
months
Can be cultured completely in freshwater
Coho salmon
Coho salmon valued because resistant to many common salmonid
viruses (including IHN)
Interspecific hybridization of coho with other salmon species and
rainbow trout often evaluated for disease resistance
Increased disease resistance often achieved but negative attributes
(poor viability and growth) common
Triploidization after hybridization improves viability in some crosses
Sockeye salmon
Historically harvested for canning industry (deep red flesh) canned
fish sales declined causing sockeye to be less cultured vs. other
“Pacifics”
Renewal of interest in sockeye for “upscale” smoked, packaged
salmon fillets have led to their increased production in aquaculture
Feshwater races (Kokanee) popular for stocking inland fisheries
(including Lake Taneycomo, Mo in 1970s)
Kokanee least piscivorous of the Pacific salmon
Populations highly prown to IHN, viral disease affecting fish liver
Chum salmon
Flesh is not considered sufficiently high-quality for high U.S.
consumption
Japan and former Soviet Union countries have been involved in
culturing
Some culturing of chum salmon as food fish in the U.S. is done; e.g.
in Alaska
Popular sportfish in Alaska, some commercial fish producers funded
by DNR to produce chum salmon
Chinook salmon
Major production off British Columbia coast – in floating net-pens
Enters saltwater phase early
Unlike the coho Chinook mature late and so grow large
Limitation to egg supply noted as current impediment to production
Salmon culture – general
Salmon culture has experienced major social/legal issues associated
with rearing in nearshore marine environments
Net-pens: concerns over pollution of nearshore waters from feed
waste (BOD, P, N) antibotics (terramycin) in fish themselves, plus in
aquatic environment; vaccination required in some states,
escapement of fish is major concern
Market competition is notoriously high
Aquaculturist’s competitors include capture fishers, salmon culture
from other countires, including mega-companeis with rearing
facilities spread globally (e.g. Nutreco Aquaculture)
High volume producers can endure periods of low profit margins
Crowding in net pens has led to numerous disease problems
Vibreo sp. Bacterial disease – can be trnasmited to humans that
consume infected fish causing GI-tract illness
Samon louse, causes discolor and devalue
Feed costs are generally most expensive component of fish culture
% protein in diets greatly influences feed costs
Feed cost is particularly high in net-pens (>50% of total var costs) –
feed falls through pens contributing to feed wastage *underwater
photography for judging satiation)
Fish that grow well on lower protein diets or will tolerate animal
protein substitutes. Will have economic advantage
Pink-red flesh color as in wild fish is desired – feed additives
(astraxanthin) used to achieve flesh color
Choice sites for net-pens limited
Some degreee of waste movement desirable for water replacement
and removal of wastes
Optimal sites are a compromise between sufficient water movement
and safety of workers
Open-Ocean rearing in development
Wastes dispersed well by stronger offshore currents
Salmon forced to swim – leaner with higher flesh density
Being out-of-sight will reduce problems with the public
Larger space available for increasing production
Larger pens will allow lower-density rearing with potential for lower
social costs and less disease transmission (less medicated feed)
Tank Culture Systems
Involve circular or rectangular tanks made typically of fiberglass,
plastic (300=25,000+ gallons)
Can involve open systems – water trickles in and exits tank via a
standpipe (which controls water depth)
Typically used in low-productivity settings e.g., rearing fry to
fingerlings or for holding a few larger fish – otherwise substantial
water flow through required
Intensive culture involves closed systems where water is
reconditioned and reused
Basis for RASs (recirculating aquaculture system)
Filling a typical production pond requires 10to the six gallons of
water per acre
An additional equivalent volume needed per acre to make up for
evaporative and seepage losses annually
Assuming annual pond yield of 5,000 lbs of fish/acre
400 gallons required per pound of fish produced
RASs require <10% of water volume needed by ponds to produce
similar fish biomass
RASs require far less land
Major reductions in water demand and land requirement vs ponds
Costs on construction and particularly operation can be high: also
higher feed costs (complete diets)
RAS does
o Removes solid wastes
o Reduce/alter by-produces of fish metabolism
o Replenish DO lost from fish respiration and breakdown of
waste feed and egesta
Solids
o Settleable, suspended, fine and dissolved
Settleable
Re=suspend settleable solids via agitation and
move water through separate settling tank
(clarifier)
Suspended solids (limit fish production: irritate gills –
removed by filtration (screens or granules)
Fine and dissolved solids (<30 microns: >50% of total
suspended solids; create BOD and gill irritation
Foam fractionation – air bubbled up through tube
creates surface foam to which fine/dissolved
solids adhere – film is skimmed off along with
solids
Nitrogen management
o Total ammonia-nitrogen: includes NH3 and NH4+
o Excreted across gills of fish as feed is consumed assimilated
by-product of protein breakdown
o NH3 highly toxic to most fish, NH4+ less so.
o Difference between the two depends on PH (ph7=NH4+
ph=8.0, mostly NH3)
o TAN is oxidized to nitrite (NO2) by nitrifying bacterium
Nitrosomonas
o Colonies grown on surfaces of substrate located in biofilter
component of RASs over which water moves (biofilters contain
high surface area media – (sand,gravel, plastic)
o Nitrosomonas will establish naturally on substrate if fish in
tank, but initial colony growth expected by seeding
o Nitrobacter oxidizes nitrite for nitrate (NO3) which is
essentially non-toxic (up to >100 mg/L)
o Nitrification = NH3 – NO2 – NO3
PH
o Sometimes important to be monitored
Nitrification is an acid producing process – hydrogen ions given off
As hydrogen ions given off they combine with bases; this reduces
alkalinity and tends to lower pH
Concern – Low pH in RAS-tanks (<4.5) can harm fish; ph<7 reduces
activity of nitrifying bacteria, leads to toxic NH3 and NO2
Ammonia build-up is the major factor that limits carrying capacity of RASs
However, adequate DO is clearly of high importance as well
Maintaining adequate BO requires that oxygen use rate is compensated for
by oxygen replacement
Major sources of DO uptake in RAS
o Respiration of the fish
o Oxygen demand of bacteria
CO2 is produced in RASs from fish respiration
o Under low DO, CO2 can reach high levels in blood
Dissolved nitrogen gas
o Rarely a problem, particularly in warm water systems readily
exits RAS
Can be problem when pressurized by aeration oxygenation is done
as nitrogen can become supersaturated in water
Causes gas bubble disease
Addition of oxygen or release of CO2 can be accomplished by: air
diffusers, agitators or by packed columns
FACT – system aeration is often done in a culture tank itself,
however is not the most optimal location to perform aeration
o Oxygen transfer efficency of aerators drops with increasing
DO concentration
o Better location to aerate is in water flow stream JUST PRIOR
TO RE-ENTRY TO TANK; WHERE DO LEVELS ARE LOWESTA
NAD CO2 LEVELS ARE HIGHEST
o Packed column aerators (PCAs) are effective at re=aerating
water in a stream flow
o In highly intensive RASs DO uptake can be too high
Pure gaseous O2 diffusion is used
Typical DO saturation levels are <8.75 mg/L at >20C
with pure O2 diffusion immediate receiving water
becomes supersaturated with O2 (>40 mg/L) at STP
results in rapid diffusion into tank water
Raceway systems
Can produce substantial quantities of fish in much less land area
than is required by ponds: fish held at high density due to high
water flow through
Used for cold and cool water species
Cells often arranged in step down series, sometimes in parallel.
Require large quantities of water
o Springs, artesian wells, hypolimnetic releases
o Gravity flow is a major benefit
o Water volume requirement
o Raceway construction size based on water flow capacity
o Water inflow requirement can be reduced if in-raceway
aeration is used (costly!)
o Closed/semi-closed systems eveloped to conserve water and
reduce effluents
o Some fish farmers combine raceways with ponds for closed
systems: ponds serve to restore water quality (solids removal,
natural biofiltratyion, reaeration
o Rule of thumb: total pond volume should hold 7x daily
discharge from raceway system: deep ponds not suitable for
aquaculture may be used.
o Biofiltration (NH3 to nitrate) and reaeration, sometimes UV
treatment for decreasing disease organisms
o Loading density
Lbs of fish/cubic foot of water flow/minute
o Fish stocking densities (ON TEST)
Sometimes set so crop at harvest will be close to
system carrying capacity
Result underutilizes the potential carrying
capacity of system
But
Low risk of loss
Alternatively
Stocking density can be started at carrying
capacity
o Remove fish as they grow to prevent
exceeding carrying capacity
Plus side: max production of
system
Downside: more risk
Demand feeders
Reduce labor
May not reduce overfeeding
ON TEST
Feed efficiency = total weight gain / weight feed
provided
Higher values better
Feed conversion ratio = FCR = 1/FE
Lower values are better
Values close to 1 considered favorable
Bad FCR
Improper feeding
Inadequate diet composition
Adverse environmental factors
TEST
5-7 book chapters
1/23/09 11:56 AM
Fish nutrition, feeds and feeding
Complete diets
contain all protein 18-50%, lipid 10-25%, carbohydrates 15-20%,
ash<8.5%, phosphorus(<1.5%) and trace amounts of vitamins and
minerals that a species requires
Supplemental diets
o Do not contain full vitamin and mineral requirement
Intended to supplement natural food by providing extra
protein and carbohydrate and/or lipid
Protein
o Most expensive feed component
Important not to overprovided
o 10 of the 20 needed AAs in fish can not be synthesized by
fish, must be in diet
are essential amino acids
lysine, methionine ON TEST
are most limiting essential amino acids in
fish diets
o growth rate reduced if not sufficient
o When soybean meal is substituted for fishmeal protein in fish
diets, methionine levels are too low and must be added
o Important to add proper protein requirement and AA
requirement for each fish species/life stage
o Protein requirement typically higher in intensive culture and in
juvenile fish
o Protein requirements also vary with temperature, water
quality, feeding rates and genetic strain (influence growth
rate
o Protein in diet should be used for fish growth
Occurs when adequate energy levels are present in diet
o Protein made of carbon, nitrogen, oxygen and hydrogen
o Up to 65% of protein in feed can be lost to environment
o Excreted nitrogen from diet protection, plus that from wasted
feed contributes to eutrophication problems associated with
aquaculture
Lipids (fats)
High energy nutrients
Keep protein from becoming energy source
Supply essential fatty acids (EFAs)
Serve as transporters of fat-soluble vitamins
o Lipids provide
Energy
EFAs
Transport vitamins
o Fish typically require fatty acids
Omega 3 and omega 6 families
Fatty acids can be saturated, polyunsaturated or highly
unsaturated
Marine fish oils
High in omega-3 HUFas (>30%)
o Marine fish require omega 3 HUFAs in diets
o Two major EFAs
Eicosapentaenoic acid (EPA)
Docosaphexanoic acid DHA)
o Freshwater fish do not require long-chain HUFAs directly like
marine fish
Carbohydrates
CHOs are most economical (inexpensive) energy source in fish diets
Not essential but used to reduce feed costs (protein sparing) and for
“binding” qualities
Causes it to float
o Cooking starch makes it more bio-available
CHOs stored as glycogen
Major energy source for mammals
Mammals extract 4kcals of E per gram
1.6 k calls by fish
Vitamins
Normal growth and health
Water-soluble
o Vitamin C
Antioxidant needed for healthy immune system
Fat soluble
Minerals
Micro-minerals (trace minerals)
Macro-minerals
1/23/09 11:56 AM
