Bailey, J. E., B. L. Wing, and C. R. Mattson.

1975

Zooplankton abundance and feeding habits of fry of pink salmon, Oncorhynchus gorbuscha, and chum salmon Oncorhynchus keta, in Traitor's Cove Alaska, with speculations on the carrying capacity of the area.

National Marine Fisheries Service, Fishery Bulletin 73:846-861.

Alaska, juvenile chum salmon, juvenile pink salmon, carrying capacity, timing, abundance, food, diet, distribution, size

These fry fed little in fresh water but fed heavily in estuary. Did not feed on cloudy moonless nights. In aquaria fry consumed 2-3 zooplankters/min at 65-170 foot candles, but decreased to 0.5 zooplankters/min at 2 foot candles. In dark conditions the fry consumed 0-0.2 zooplankters/min. Epibenthic prey was rare in stomachs of fry less than 60 mm. Traitor's Cove has rocky shorelines providing little benthic feeding opportunity. Dominant prey: cladocera, decopod zoea, and larvacea. The barnacle nauplii were a small portion of diet even though a large portion of the plankton. The feeding rate was higher at lower water velocities. Maximum feeding rate at 0-10.7 cm/sec. Feeding ceased at 20-24 cm/sec. Fry avoided currents greater than 24 cm/sec. Estimated 1-7 million fry present during each of the three years studied. Carrying capacity of Traitor's Cove estimated at 50-100 million fry.

Bax, N. J.

1983

Early marine mortality of marked juvenile chum salmon (Oncorhynchus keta) released into Hood Canal, Puget Sound, Washington, in 1980.

Canadian Journal of Fisheries and Aquatic Sciences 40:426-435.

Puget Sound, Hood Canal, juvenile chum salmon, hatchery, survival, mortality

Hatchery-reared chum (50 cm) were marked with fluorescent pigment and released near the mouth of the Skokomish R. in south Puget Sound. Marked fish were recaptured by beach seine (37 x 3 m) and tow net along the beaches of southern Hood Canal. Average daily mortalities of 31% and 46% were estimated for periods of two and four days. Concluded mortality is initially high (especially for fish remaining near point of entry) and decreases during first 40 days following entry into saltwater.

Bax, N., and C. J. Whitmus.

1981

Early marine survival and migratory behavior of juvenile chum salmon released from the Enetai Hatchery, Washington, 1980.

University of Washington, Fisheries Research Institute Report 8109, 48 pp.

Hood Canal, estuary, juvenile chum salmon, migration, survival, distribution, behavior, growth rate, hatchery

Differentially marked juvenile chum salmon (Oncorhynchus keta) from a hatchery were released and recaptured in Hood Canal in 1980 over a five day period. An estimate of survival was reported for the 380,000 juvenile chum salmon released along the west shore of Hood Canal, as well as for the two groups totaling more than 60,000 juvenile chum salmon held and later released from holding pens. Migration routes and growth rates were also reported. Juvenile chum were spray-marked with fluorescent pigment and minimal initial mortality from the marking procedure was noted. Fish were recaptured via surface townetting and beach seining, and then sorted, enumerated, identified by marker color and preserved in 10% formalin. To estimate survival over time, the two smaller groups with different marker colors were released two and four days later from the release date of the larger group, and at the center of larger group's distribution point.

One day after release of the larger group, fish migrated north and south and nearly one seventh of the fish recaptured in the nearshore (seine) and two-thirds of the fish recovered in the pelagic zone (townet) had migrated cross Canal to the east shore (approximately two miles) before being recaptured. Size and weight of the migrating fish were not significantly different than those fish remaining on the west shore. The beach seine sites along the west shore at the Skokomish River flats (release point) yielded the highest catch-per-unit-effort. The migratory behavior of the smaller groups was similar to the larger group. The mean estimate of survival for the larger group over two days after release was estimated at 51% assuming no emigration, 55% when correcting for any emigration. For the second group the estimates were 42% and 52%. The estimated survival rate appeared constant over four days, 20% with no emigration and 26% assuming emigration. Data were variable when calculating growth rates, but it was estimated as 8.6% body weight per day for the recaptured fish.

Beachum, T.D.

1993

Competition between juvenile pink salmon (Oncorhynchus gorbuscha) and chum salmon (O. keta) and its effect on growth and survival.

Canadian Journal of Zoology 71:1270-1274.

British Columbia, estuarine, nearshore, juvenile pink salmon, juvenile chum salmon, growth rate, survival, competition

The relative competitive ability of Fraser River juvenile pink (Oncorhynchus gorbuscha) and juvenile chum (O. keta) salmon was investigated. The species were reared in varying proportions in both a monoculture and duoculture environment (six different environments) and growth and survival measured to determine if rearing in a duoculture environment affected growth and survival, and if relative densities of both species played a role in this effect. Gametes were collected from adult pink and chum salmon, and in a controlled environment the eggs were fertilized and the pink and chum salmon were reared for 60 days.

The mean weight of chum salmon was 50% greater than pink salmon at emergence. The biomass of pink salmon and chum salmon increased from 0.08–1.8% and 3.2–3.8% per day, respectively, depending on the environment. Pink salmon growth rates were impacted more severely by high initial biomass than were chum salmon growth rates, and pink salmon growth was poor even in a monoculture. Pink salmon survival ranged from 70-90% in the six environments. Maximum survival of pinks occurred in the environment with 50% pink and 50% chum individuals. Chum salmon survival was a minimum of 95% in each of the environments. Under culture conditions “chum salmon can have a significant inhibitory effect on pink salmon growth.”

Beachum, T.D. and C.B. Murray.

1987

Adaptive variation in body size and developmental biology of chum salmon (Oncorhynchus keta) in British Columbia.

Canadian Journal of Fisheries and Aquatic Sciences 44:244-262.

British Columbia, chum salmon, morphology, timing, life history

In rivers of different size, over 10,000 chum salmon from 78 stocks were examined for several characteristics including variation in size and age at maturity, body morphology, and comparative developmental biology. It was shown that chum salmon possess variable traits that are specifically adapted to different environments.

Chum salmon were surveyed and various measurements were made to determine age and morphology (sex ratios, age, size, morphology). Gametes were collected for examinations related to developmental biology. It was reported that males were more abundant (at younger and older ages) than females, and age at maturity was dependant on spawn timing and stock abundance. Chum from large rivers were larger in size than those from smaller rivers. Additional characteristics and differences were noted.

Beamer, E., R. Henderson, A. McBride, and K.W. Wolf.

2003

The importance of non-natal pocket estuaries in Skagit Bay to wild chinook salmon: an emerging priority for restoration.

Skagit System Cooperative, Research Department, La Connor, WA 10pp

Skagit Bay, pocket estuaries, juvenile Chinook salmon, density dependence, life history, restoration

Non-natal habitat use by wild juvenile Chinook salmon (Oncorhynchus tshawytscha)in nearshore regions of Skagit Bay was studied during 2002. Substantial habitat loss in the delta region has occurred over time. A density dependent relationship was illustrated where current delta habitat conditions were shown to restrict the capacity of chinook rearing in the delta, displacing some Chinook from delta habitats.

Within Skagit Bay, pocket estuaries were described as smaller estuaries formed behind spits or barrier beaches and include tidal lagoons, salt marsh and channels. Low energy regimes and freshwater input (depressed salinities) characterized pocket estuary habitats. Juvenile Chinook salmon utilized pocket estuaries as rearing habitat and refuge from predatory fish. Results from various sampling methods revealed wild Chinook salmon fry migrant life history types utilized and preferred pocket estuary habitats from late winter through spring as compared to adjacent nearshore regions. Fry migrants measured larger in the pocket estuaries than in the adjacent nearshore regions during the rearing period prior to May. Pocket estuaries early in the year appeared to be a refuge for fry migrants, exposing these fish to less risk from larger predatory fish.

Much of the historic pocket estuary area is unavailable to the Chinook salmon fry migrant life history type. Restoration and protection of pocket estuaries may be considered a recovery priority for the fry migrant life history type of Skagit River Chinook populations. This strategy should occur in addition to, not in place of, restoration of the Skagit delta estuary that would benefit the delta-rearing life history types. Continued research is needed to prioritize and support restoration attempts.

Beamish, R. J., and D.R. Bouillon.

1993

Pacific salmon production trends in relation to climate.

Canadian Journal of Fisheries and Aquatic Sciences 50:1002-1016.

North Pacific Ocean, pink salmon, chum salmon, sockeye salmon, climate, abundance, mortality, survival, food, hatchery, management

Commercial pink (Oncorhynchus gorbuscha), chum (O. keta) and sockeye (O. nerka) salmon catch data from 1925-1989 for several countries was examined for trends in salmon production relative to large-scale marine environmental changes in the northern North Pacific Ocean. The distribution of salmon species from Japan, Canada, Russia and the United States overlap in this region of the North Pacific, dominated by the Aluetian Low pressure system. Methods were described for calculating lost production due to Japanese high seas interception of salmon stocks, and for creating an Aleutian Low Pressure Index.

Similar trends were observed for the combined nations catch of pink, chum and sockeye as well for each species individually. Catch trends were also examined for each country individually. The observation of similar trends in catch for the three species “suggests that common events over a vast area affect the production of salmon in the North Pacific Ocean” despite the presence of other variables (different fishing gear, increased effort, different fleet dynamics, different policies). The annual relationship between salmon production and the Aleutian Low Pressure Index was highly variable. Potential factors affecting production trends other than the environment were discussed, such as overfishing and artificial rearing or enhancement activities. Hatchery production, survival rates, and catch rates were compared for each species and for each nation. An important conclusion was that “the long-term pattern of the Aleutian Low pressure system corresponded to the trends in salmon catch, to copepod production, and to other climate indices, indicating that climate and the marine environment may play an important role in salmon production.” When trends in salmon production change, “it may not be an appropriate strategy to continue to release large numbers of artificially reared smolts during a period of decreasing marine survival of salmon.” When managing a fishery, a reduction in marine survival should be treated differently versus a decline in survival due to fishing mortality.

Beamish, R.J. D. J. Noakes, G.A. McFarlane, L. Klyashtorin, V.V. Ivanov, and V. Kurashov.

1999

The regime concept and natural trends in the production of Pacific salmon.

Canadian Journal of Fisheries and Aquatic Sciences 56:516-526.

Climate, Pacific Ocean, salmon, production, abundance, modeling

Persistent patterns and synchronous shifts in the climate and ocean environment of the Pacific Ocean were demonstrated by previous research. Mounting evidence has also provided a link between major trends in Pacific salmon abundance and climate trends. Persistent trends in salmon (or fish) populations or ocean conditions was referred to as ìregimes,î and defined as ìa multiyear period of linked recruitment patterns in fish populations or as stable means in physical data series. A regime shift is a synchronous change in these variables.î Six indices of climate over the Northern Hemisphere were examined in this study for persistence and synchrony of change; four indices were combined to generate a regime index. The regime concept has value in fishery management because the impacts of a natural shift in fish abundance should be distinguished from the results of fishing pressure. It was demonstrated that synchrony exists among the major climate indices in the Northern Hemisphere. Furthermore, a strong relationship was noted between climate and population dynamics, necessitating an understanding of global warming linkages to population dynamics.

Beamish, R.J., and C. Mahnken.

2001

A critical size and period hypothesis to explain natural regulation of salmon abundance and linage to climate and climate change.

Progress in Oceanography 49:423-437.

British Columbia, marine, Chinook salmon, coho salmon, chum salmon, abundance, production, mortality, predation, survival, hypothesis, climate, hatchery

A new hypothesis was proposed to explain the linkages between climate and climate change and fluctuations in abundance of Chinook (Oncorhynchus tshawytscha), coho (O. kisutch) and chum (O. keta) salmon. The “critical size and critical period” hypothesis stated “that salmon year class strength is determined in two stages during the first year in the ocean” where during the first stage, predation accounts for most of the marine mortality soon after salt water entry, and the second stage where mortality occurs in the fall and winter of the first year for fish that fail to reach a “critical size” due to their inability “to meet minimum metabolic requirements.” The hypothesis was tested based on results from ocean survey research in the Strait of Georgia, British Columbia as well as experimental feeding studies on coho. Otolith weights and hormone levels were measured. Abundance estimates for juvenile coho (and possibly Chinook) pointed to high mortality during the fall and winter of their first year in the ocean. It was concluded that these studies “provide evidence for the general hypothesis that growth-related mortality occurs late in the first marine year and may be important in determining the strength of the year class (brood year).” Mortality and climate linkages “could be operating via the availability of nutrients regulating the food supply and hence competition for food (i.e., bottom-up regulation).”

Beckman, B.R., D.A. Larsen, and W.W. Dickhoff.

2003

Life history plasticity in chinook salmon: relation of size and growth rate to autumnal smolting

Aquaculture 149-165.

Hood Canal, Chinook salmon, growth rate, smolt, life history, plasticity

The plasticity of autumnal smolting of hatchery spring Chinook (Oncorhynchus tshawytscha) salmon was investigated. The relative influence of body size and growth rate on autumnal smolting was assessed through an experiment consisting of rearing fish of two different size groups at reduced ration in four treatment groups (large fish-high feed, large fish-low feed, small fish-high feed, and small fish-low feed). The goal was to determine whether size differences or growth rate altered the expression of autumnal smolting. Throughout the July-November study period, physiology and behavior were assessed and a subset of fish from each treatment group tagged and movement patterns observed.

Chinook under-yearlings from each treatment group exhibited autumnal smolting. Different feeding rates resulted in fish with different growth trajectories (high feed = high growth rates, low feed = low growth rates). Fish from the large-high feed treatments differed in several respects from fish in the small-low feed treatments from August through September: higher condition factor, more silvery skin, and higher levels of plasma T4 and IGF-I hormones and gill Na+ -K+- ATPase activities. During October and November fish from the large-high feed group exhibited greater activity levels than fish from the small-low feed group. Fish from the large-high feed group “displayed physiological traits [and behavior] consistent with smolting over a longer period” than did fish from the small-low feed group. The data demonstrated “that differences in growth through the summer-autumn period has a significant effect on both physiological and behavioral expression of smolting.”