The Effect of Ocean Conditions on Salmon Survival and Return

The Effect of Ocean Conditions on Salmon Survival and Return

Joseph C. Greene, Research BiologistClaudia J. Wise, Physical Scientist

Greene Environmental Services

Hypothetical escapements to the Russian River for all species of salmon

[Estimates based on conservative expansion of U. S. Bureau of Fish and Fisheries (1885), Warm Springs Hatchery return numbers, and anecdotal CDFG reports.] (Steiner, 1996).

Numerous human and natural factors have been implicated in the crash of West Coast salmon runs.

It seems no one factor alone has caused the decline, but each has contributed to the

problem in its own negative fashion.

Habitat has been altered or destroyed by:

sedimentation;

water diversions;

riparian vegetation removal; and,

elevated water temperatures.

Finally, natural events combined with human activity have culminated in a distinct crisis for the Klamath species.

The natural equilibria of predation and competition have been shifted by human activities.Infection and disease have become increasingly prominent as water temperatures rose, dams were built, and hatcheries were operated.

Chinook harvest over the years (both legal and illegal) has caused further detriment to the species.

The number of returning spawners, wild and hatchery-reared, fluctuates considerably

between years but in most areas the long-term trend is that the runs have diminished and in

many cases gone extinct.

The dynamics behind those changes are often far from understood and due to the complex

salmon life cycle their survival can be impacted by a multitude of physical and biological

factors in local watersheds and the ocean.

NRC (National Research Council). 1996. Upstream: Salmon and society in the Pacific Northwest. Washington, DC: National Academy Press.

Habitat Salmon Needs at Each Stage of the Life CycleWhen adults spawn, they need the right stream gravel, or substrate, for their nests. Each species has unique spawning area requirements, including substrate size, area, depth, and water velocity. Spawning adults also need clear, clean, and cold water.

When fertilized eggs mature into embryos, they need a constant supply of clean, cold, and clear water. This water flows through the gravel in the redds (or nests) providing oxygen to the growing embryos and removing waste products.

When freshly hatched alevins, mature into fry, they need plenty of food in the form of microscopic plants and animals, called phytoplankton and zooplankton. Fry also need slower-moving water when they emerge from the redd, because they are not strong enough to swim in swift currents.

When fry mature into smolts, they undergo physiological changes so that they can live in salt water. Shallow estuary areas with brackish water help smolts adjust gradually to the ocean’s salt water. These areas also supply smolts with abundant food, helping them grow and improving their chance of survival after they migrate into the ocean.

When smolts grow into adults, they need ample ocean food. Unfortunately, little is known about this part of the life cycle, and it is different among different salmon species and regions.

The U. S. Fish and Wildlife Service Lists 8 Peer-Reviewed Reasons for Salmon Decline in the Klamath River Basin

Over fishing;

Logging; The Trinity River Diversion;

Irrigation Diversions in the lower Klamath Basin tributaries;

The 1964 Flood;

The 1976 - 77 drought which was a 50 year/100 year drought, back-to-back; Sea Lion predation;

Brown Trout predation.

Chinook are deeper water fish, and due to 3,4,5 variable return age can handle fluctuating ocean conditions

Steelhead head off the shelf and north to more productive waters off the artic circle which are less affected by regime shifts. Their life cycle and variable age of return is more adapted to variable conditions

Species differencesCoho salmon appear to be more affected by the Pacific Decadal

Oscillations and El Nino/Southern Oscillation shifts. WHY?

Coho are shallow water fish. They are tied to:

Sea Surface Temperatures; Upwelling; Spring transition; 1st winter ocean conditions; and, They have a 3 year life cycle.

Once in the ocean, they continue to eat zooplankton, but add crustacean larvae to their diet.

Young salmon in freshwater mainly eat zooplankton, benthic amphipods and insects.

As they become larger, they will prey on small fishes and sometimes squid.

Upon entering fresh water to spawn, salmon stop feeding entirely.

Plankton

Phytoplankton are the energy for all of life in the underworld.

Most phytoplankton photosynthesize, changing light energy from the sun into energy that all non-photosynthesizing organisms can use.

Phytoplankton = microscopic plant life

Zooplankton = animal like organisms

Plankton size relative to the eye of an needle

In most cases phytoplankton are

eaten by very small animal-like organisms called

zooplankton.

The Pacific Northwest Index (PNI) The Pacific Northwest Index (PNI) characterizes cool/wet and warm/dry climate characterizes cool/wet and warm/dry climate

patterns in the Pacific Northwestpatterns in the Pacific Northwest

James J. Anderson, School of Fisheries, University of Washington, Review of the Influence of Climate on Salmon

The catch of the Columbia River spring chinook is correlated with the PNI

James J. Anderson, School of Fisheries, University of Washington, Review of the Influence of Climate on Salmon

Warm & Dry

Cool & Wet

Warm & Dry

Cool & Wet

Coastal Ocean Variability and Coastal Ocean Variability and Ocean Survival of Coho SalmonOcean Survival of Coho Salmon

Coastal ocean conditions play an important role in Coastal ocean conditions play an important role in marine survival of young coho salmonmarine survival of young coho salmon, and the number , and the number of adults returning to freshwater each year.of adults returning to freshwater each year.

Upwelling variability during the juvenile coho's first Upwelling variability during the juvenile coho's first ocean spring and summer may be particularly important ocean spring and summer may be particularly important in determining adult productionin determining adult production..

Since 1985Since 1985 there has been a sharp decline in the there has been a sharp decline in the ocean survival of coho salmonocean survival of coho salmon..

Frank Schwing, Completion of Manuscript on Remotely Sensed Coastal Ocean Variability and Ocean Survival of Coho Salmon,

(831-648-9034, [email protected])

Returns of Steelhead to Iron Gate Hatchery had been increasing at about 2% per year since 1963, but

exhibited a strong decline since 1987

Figure B-17. Returns of adult steelhead to Iron Gate Hatchery on the Klamath River

NOAA, 1994, Status Review for Klamath Mountains Province Steelhead, Technical Memorandum NMFS-NWFSC-19


The relationship between coho survival and sea surface temperature anomalies, calculated weekly in the region 37-51°

N during 1985-1996, was examined using univariate and bivariate

regression analysis for a number of different time frames.



The sum of negative sea surface temperature anomalies from April to June, when juvenile

coho first enter the ocean, was highly correlated against survival.


The sea surface temperature variables explain over 90% of interannual variability in the marine survival of hatchery-reared coho

salmon from 1985 to 1996.



Hatchery Raised FishHatchery Raised Fish

Numerous studies have been published describing Numerous studies have been published describing the genetic and ecological risks that artificial the genetic and ecological risks that artificial production may pose for naturally spawning fish production may pose for naturally spawning fish populations.populations.

In assessing the risks to any particular population, it In assessing the risks to any particular population, it is usually difficult to demonstrate conclusively that is usually difficult to demonstrate conclusively that adverse effects are actually occurring, and, if they adverse effects are actually occurring, and, if they are demonstrated, how serious they are.are demonstrated, how serious they are.

In assessing the status of stocks proposed for In assessing the status of stocks proposed for listing under the ESA, NMFS found the effects of listing under the ESA, NMFS found the effects of artificial propagation to be among the most difficult artificial propagation to be among the most difficult and controversial to incorporate into risk analyses.and controversial to incorporate into risk analyses.

CDFG, National Marine Fisheries Service Southwest Region Joint Hatchery Review , 2001, Report on Anadromous Salmonid Fish Hatcheries in California.

Survival rates of coho and chinook salmon released from hatcheries on the U.S. and

Canadian Pacific coast 1972–1998

Magnusson, A., 2002, Survival rates of coho (Oncorhynchus kisutch) and chinook salmon (O. tshawytscha) released from hatcheries on the U.S. and Canadian Pacific coast 1972–1998, with respect to climate and habitat effects, University of Washington, School of Aquatic and Fishery Sciences, Thesis for Masters Degree.

Smolt-to-adult survival rates were estimated for 18,659 coho and chinook coded wire tag groups released in 1972–1998 from 206 hatcheries on the U.S. and Canadian Pacific coast.

Survival rates of 153 wild coded wire tag groups showed similar trends as those of hatchery fish.

The long-term trend for both coho and chinook was a decline in all regions south of Alaska.

Regional and annual variation explained 46% of the total variation for coho, 34% for fall chinook, and 42% for spring chinook.

Survival rates of coho and chinook salmon


Regression analysis was used to explore the relationship between survival rate and climate during the year of release, and the variable that showed the strongest relationship was summer sea surface temperature at the place where the fish reach the ocean.

The sea surface temperature variable alone explained 41% of the regional and annual variation of coho survival rates.



Little is known about the ecological dynamics that link sea surface temperature and survival rate, but sea surface temperature is highly correlated with a suite of physical and biological factors in the ocean.

There has been a long-term increase in sea surface temperature from the early 1970s to the late 1990s, corresponding to the declining survival rates south of Alaska and increasing survival rates in Alaska.



The decline in wild salmon abundance in the 1990s was due in considerable part to changes in ocean conditions



and increases in wild stock abundance may be expected if ocean

conditions change.

The 1998 El Nino and the following 1999 La Nina were the largest amplitude El Nino/Southern Oscillation cycle in recent (measured) history;

Many Pacific Northwest stocks will be depleted for several decades;

Several year classes already severely depleted were subject to this event; and,

The effects were particularly severe on coho salmon.

Effects on Fish

What does this mean for fish?

Winter sea surface temperature in the smolt year;

Date of spring transition to saltwater;

Spring upwelling; and,

winter sea surface temperature …

correlate with annual mean temperature and are indicators of coho production.

What does this mean for fish?Lowering of sea surface temperature,

increased upwelling,

increases ocean productivity,

Increase in prey species,

decrease in predator species, and shift from salmon to baitfish (herring, anchovy, sardine and smelt) as prey item for predators

… favors ocean survival

Pacific Decadal Oscillation signal has turned and remained negative since July 1998, longest period of negativity since 1976 (Peterson, 2002 NOAA).

Oregon Plankton tows show a doubling of the copepod species has been observed, and a shift in biomass to increased boreal neritic species”, concurrently with decreased “transitional/subtropical neritic species”- CA copepods have disappeared from BC tows (Zamon 2002).

Zooplankton resemble the assemblage seen in the 1970’s during the last negative Pacific Decadal Oscillation.

Recent Research

as the causes of decline for coho salmon. Both petitioners argued that the primary cause for decline has been habitat destruction (Oregon Trout et al. 1993, Pacific Rivers Council et al. 1993). Oregon Trout et al. (1993) also identified over utilization of the species for commercial and recreational purposes as an equally important factor for Oregon coho salmon, while the Pacific Rivers Council et al. (1993) identified deteriorating ocean conditions as a major cause for the general decline of west coast coho salmon. Both petitioners cited adverse effects of artificial propagation as an aggravating factor. Pacific Rivers Council et al. (1993) also identified intraspecific hybridization and interspecific hybridization with chinook salmon as an additional concern.

Causes of Decline for Coho Salmon

NOAA, 1995, Status Review of Coho Salmon from Washington, Oregon, and California, NOAA Technical Memorandum NMFS-NWFSC-24

The petitioners for ESA status for Coho salmon identified: habitat destruction; over fishing; artificial propagation; and, poor ocean conditions

A principal component analysis reveals that Pacific salmon catches in Alaska have varied inversely with catches from the U.S. West Coast during the past 70 years.

If variations in catch reflect variations in salmon production, then results of our analysis suggest that the spatial and temporal characteristics of this “inverse” catch/production pattern are related to climate forcing associated with the Pacific Decadal Oscillation, a recurring pattern of pan-Pacific atmosphere-ocean variability.

Temporally, both the physical and biological variability are best characterized as alternating 20-to 30-year-long regimes punctuated by abrupt reversals.

From 1977 to the early 1990s, ocean conditions have generally favored Alaska stocks and disfavored West Coast stocks.

Unfavorable ocean conditions are likely confounding recent management efforts focused on increasing West Coast Pacific salmon production.

Hare, S. R., N. J. Mantua and R. C. Francis, 1999, Fisheries, 24:6–14

What scientists at the University of Alaska Fairbanks say about salmon declines in Alaska

Ted Cooney, professor of fisheries oceanographyInstitute of Marine Science

School of Fisheries and Ocean SciencesUniversity of Alaska Fairbanks

Cooney: "Scientific data on these natural cycles in

salmon populations go back to the 1920s. These

analyses show that for Alaska salmon stocks, there

have been cycles in the past. The cycles seem to run

on the order of 20 years. In some years more fish are

produced and in other years fewer fish are produced.

So, the recent declines aren't terribly surprising."

Do salmon runs in the North Pacific Ocean fluctuate according to cycles?

http://www.uaf.edu/seagrant/issues/salmon_gone.html

Milo Adkison, professor of fisheriesFisheries Division



Explain what you mean by the history of salmon fisheries.

Adkison: "The record of salmon returns is that they

are highly variable. The salmon survival rates are

highly variable. You get large year-to-year variations

and you also get shifts in the productivity that run for

a couple of decades or so and then shift to a different

level of productivity. And it's all connected to changes

operating on similar time scales on the ocean."


Adkison: "The conditions out in the ocean have been really

unusual the last couple of years. It's not surprising that the models

we use to make predictions fall apart when we encounter a whole

new set of conditions. Generally, warmer sea surface temperatures

are better for salmon [in Alaska]. But the temperatures these past

couple of years have been much warmer than what we've seen

before. We may be going past the optimum to where warmer

temperatures may actually be counterproductive for salmon.

So what went wrong this year?





Adkison: "I'm not saying that we've entered a new regime, but the problem is that you have shifts that occur every 15 years or so. On top of that you have this huge year-to-year variation. So it's really hard to look at a year like last year and say 'Okay, things were lousy this year and so they're going to be lousy next year.' It's very common to have things be lousy one year and good the next year. Because there's this large interannual variability, you have a hard time deciding that you're in a new regime until you've seen five years of bad returns in a row or five years of exceptional returns in a row."

Is that what you think is happening now, that salmon are responding to long-term ocean cycles?







Adkison: "I wouldn't have thought so, but we have to take a look at that. The thinking among most fisheries biologists is that it's the youngest salmon that are the most vulnerable. So what you would have expected to see is a bad year out in the ocean and then a couple of years later a fall-off in salmon production, because the fish that had just gone to the ocean that year would be the ones most strongly affected. The adults due to come in that year could probably weather it better. So it's puzzling that the year the ocean conditions were a bit strange, the run failed the same year and not a couple years later."

Should the environmental changes seen in the North Pacific Ocean last year, such as warmer water

temperatures, seabird die-offs, and scarce plankton have tipped off managers that the salmon returns

would be low this year?

Adkison: "There's an increasing verbal focus on

ecosystem considerations. But where the rubber hits the

road there is a growing awareness that from a practical

point of view it's very difficult to take an ecosystem

approach to managing fish stocks. The data requirements

are beyond what is available for most fisheries."


Fishery managers have come under fire for not considering the ocean's effects in their forecasts. Do you sense that fisheries managers are willing to take ecosystem influences into account in their forecasts?



Adkison: "People are doing the obvious things. They look at

the abundance of principal predators; they'll look at the

abundance of food; they'll look at indicators of the state of the

overall ecosystem such as sea surface temperatures, weather

patterns, and use them as empirical predictors of salmon

survival. But it's still baby steps.

Are there some key environmental variables that could be used to improve salmon return

predictions without having to fully understand the entire ecosystem?



Tom Weingartner, assistant professor of oceanographyInstitute of Marine Science


Weingartner: "It's a little hard to say what the time scales are,

because there is a variety of time scales, but we have seen

some rather striking changes in the last year or so. Last

summer, we noticed an unusual warming that was confined to

the surface layers of the Gulf of Alaska and the Bering Sea.

Those temperature changes were two to three degrees above

normal beginning about the middle of the summer and

continuing through the fall.

Are you seeing environmental changes in the North Pacific Ocean?


Weingartner: Beyond the fall, the temperature changes were

even more dramatic. They weren't confined to just the surface

but, at least in the Gulf of Alaska, they extended down at least

250 meters or so on the continental shelf. They were about

two to three degrees above normal, and they continued

through the spring. A lot of heat is required to elevate ocean

temperatures by those few degrees.

Are you seeing environmental changes in the North Pacific Ocean? continued …


Are you seeing environmental changes in the North Pacific Ocean? continued …

Weingartner: "Through the winter we noticed that there was a

decrease in the amount of cooling that usually takes place in the

Gulf of Alaska. That was very dramatic. Our Canadian colleagues

have noticed in the Gulf of Alaska that nutrients necessary for

phytoplankton production were depleted from the surface layers

of the ocean. That has not been observed before in the Gulf of

Alaska. Other things that have been noticed are a change in the

phytoplankton species composition in the Bering Sea. That is

usually dominated by a community called diatoms, but the last

couple of summers it has been dominated by cocolithophores, a

very different phytoplankton species."


Weingartner: "Yes, very definitely so--I think in large measure

because many of the mechanisms, say temperature change

effects on phytoplankton and how such changes are transmitted

on up the food chain, are not well understood at all. Until those

connections are understood, ecosystem management of, say, a

salmon population would be difficult to make. Although I believe

this is the direction we need to go, it won't occur overnight."

Is our understanding of the marine ecosystem a field that is still in its infancy?


Donald Schell, directorInstitute of Marine Science



Your research has focused on understanding the Bering Sea ecosystem and the role it played in the declines of Steller sea lions,

seabirds and other species. Specifically, your work seeks to understand how the sea's

production of plankton, the basis of the marine food chain, has changed over time. But to

understand ocean productivity, you're studying bowhead whales. Please explain.


Schell: "We've actually looked at bowhead whales to learn

how ocean productivity has changed over the past 50 years.

… Bowhead feed on zooplankton. Zooplankton are the first

consumers of phytoplankton, the small plants that are the

first rung of the ocean food chain and an important indicator

of productivity in the ocean. … This productivity can be

measured by using isotope ratios in the baleen of whales.

Since you are what you eat, the carbon in this case is from

the consumption of plankton. The changes in carbon type in

whale baleen reflects the abundance of plankton in any

given year and can be used as an index to changes in ocean

primary productivity."


The record shows that from 1946 to 1963 everything went along fairly smoothly at a relatively high rate of productivity.

And then in the mid-1960s it increased and peaked at around 1965.

Then ocean plankton productivity began to decline, and since the mid-1970s it has gone down and down and down.

The last samples we have from 1994, 1995 and 1996 show the lowest primary productivity in the Bering Sea over this 50-year period."

Schell: We have developed a record of phytoplankon

productivity in the Bering Sea all the way back to

1946. The story it tells is amazing because the whale

baleen reflects phytoplankton productivity quite well.


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The Effect of Ocean Conditions on Salmon Survival and Return