Reading Assignment:
Chapter 23: Perciformes
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Notice:
• Projects Due: Wednesday 10 December
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Behavior & Communication:
1. Schooling
2. Feeding
3. Aggressive Behavior
4. Dominance Hierarchies
5. Resting Behavior
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1. Schooling - moving in close
coordinated association • 25% of fishes school
– herring schools to 4.5 billion m3
• @ density 0.5-1 fish per m3
• 1/7 th vol. of Lake Sakakawea
– consider: Lake Sakakawea 30 billion m3
• 200 mi long; 185 ft max depth
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Advantages of Schooling:
• Reduced risk of predation– school may appear as large organism– collective alertness– predator confusion
• difficulty of selecting target (flock-shooting)
• movement camouflage
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sergeant majorend
Advantages of Schooling continued:
• Hydrodynamics--energetic efficiency in swimming– drafting– snout-cone effect– similar to V-formation in birds
• 25 birds could get a 70% increase in distance for a given energy expenditure
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Hydrodynamics of Schooling
thrust
streamlines
turbulence
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Carangidae--bigeye jack schoolend
diagonal banded sweetlips end
Advantages of Schooling continued:
• increased efficiency in finding food
• increased reproductive success
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2. Feeding Behavior• Generalists--wide variety of prey
– omnivores -- catfishes
• Specialists--specific prey– herbivores -- plant/algae eaters– planktivores– piscivores -- fish eaters– extreme specialists
• scale-eating cichlids• parrot fishes -- coral• cookie-cuter sharks
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Scaridae--parrot-fishesend
cookie cutter shark
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cookie cutter shark
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goblin shark
caught at depth of 960 m
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Feeding Behavior continued:
• Opportunists -- take advantage of abundant prey – even if outside normal mode of feeding– non-surface feeders may feed at surface during
mayfly hatch– trout feeding on insect hatches
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Foraging Factors:
• prey size versus mouth size• energetic efficiency--energy spent versus energy
gained– prey distance– ease of capture - speed; maneuverability– handling - spines; armor– ease of digestion - composition; scales; bone– energy/nutrient content
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3. Aggressive Behavior
• Territoriality - some defend territories, generally for a limited resource– mates– breeding sites– feeding territories– Ex. Tilapia in thermal gradient
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Aggressive Behavior continued:
• Aggressive encounters:– charges– nips– flare fins– lateral displays– submissive behaviors
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Aggressive Behavior continued:
• Factors affecting aggressive advantage:– size– prior residency– result of previous encounters
• Dominance Hierarchies– often established in interacting groups– Advantages/Disadvantages?
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4. Resting Behavior
• “sleeping” or inactive
• observed in many species
• day night dusk dawn
• schools become disorganized
• some change color
• some do not react to vision or touch
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Communication
Pheromones--already covered
1. Visual Signals
2. Auditory Signals
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1. Visual Signals:• Color -- important in visual comm.
– pigments: • carotenoids - reds, yellows (contribute to green)• melanins - dark red, brown, black
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Color continued:
– Structural colors: (reflected light)• purines - reflective (colorless)
– ex: guanine (iridiophores) cells containing guanine
– iridescence: produced when light waves are reflected in parallel
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carotenoids
clown fishend
Salvelinus fontinalis--brook trout
carotenoids
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carotenoids
diagonal banded sweetlipsend
melanins
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Poeciliidae -- black mollymelanins
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Etheostoma nigrum - johnny dartermelanins
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guanineblue marlin
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guanine
Hiodon alosoides -- goldeye end
guanine
Dorosoma petenense -- threadfin shad
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guanine
Sphyraenidae -- barracudaend
Example of coloration:
Campostoma--stonerollerend
Example of coloration:
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Etheostoma exile--Iowa darter
Example of coloration:
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Lepomis cyanellus -- green sunfish
Example of coloration:
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Chromatophores -- pigment cells
• branched cells
• contain pigments or reflective crystals
• pigments can be concentrated in center or distributed in branches
• control: neuro-endocrine system
Chromatophore
pigment
Vision & Nerve control
Normal coloration
EX: experiments with flounders--role of vision
Pleuronectiformes
adrenaline
Chromatophore
pigment
Lighter color
acetyl
cholin
e
Chromatophore
pigment
Return to normal color
Function of coloration
• thermoregulation - dark absorbs heat; light reflects heat
• intraspecific communication
• evasion of predators
squirrelfishred coloration
Examples:
red--first wavelength to be filtered
red coloration
short distance advertisement
northern redbelly dace
countershading
countershading
poster colors--complex color patterns
(common in reef fish)
Function of Poster colors:• advertisement of territory ownership• contact between foragers• intraspecific communication of sex, status,
maturity (Labridae, Scaridae)• predator avoidance--cryptic on color
background• aposmatic coloration--advertisement of
danger (poison; spines)
poster colors
butterfly fish
poster colors
poster colors
queen angelfish
poster colors
poster colors lionfish--aposmatic coloration
disruptive coloration--patterns that disrupt outline
flicker fusion--patterned fish against patterned background
disruptive coloration
camouflage
disruptive coloration
camouflage
disruptive coloration
camouflage
disruptive coloration
camouflage
guitarfish
disruptive coloration
camouflage
leafy seadragon
eye concealment
eye concealment
eye concealment
eye enhancement
French angelfish
eye enhancement
moray eel
eyespots
lateral stripes
common in schooling spp
For orientation &
pred. confusion
lateral stripes
polychromatism
• different colors in different individuals– ex: midas cichlid
• gold morphs win comp. for food
• rarely common in wild (prob. due to pred.)
– ex: annual killifish• brightly colored morphs dominant--greater
reproductive success early
• dull forms live longer--rep. success later in season
special patterns
Ex: egg-shaped spots on male cichlids– mouth brooders– females take eggs into mouth after laying– attempts to pick up “dummy” eggs aids
fertilization
photophores dragonfish
Light producing cellsMost common in twilight-zone fishes 300-1000 m
Self-liminescence--liciferin/luciferace chem. react
Symbiotic luminescence--luminescent bacteria
in gland-like structures
photophores
lanternfish