Sinclair, M.

1988

Marine populations: an essay on population regulation and speciation.

Washington Sea Grant Program and University of Washington Press, Seattle. 252pp.

marine, populations, regulation, speciation, abundance, richness, pattern, variability, marine fish, zooplankton

Four components of population regulation (abundance, variability, spatial pattern, richness) in ocean environments were discussed, particularly for marine fish. A historical background of marine population concepts provided insight into the development of these concepts since the late 1800?s. A better understanding of population regulation may be attributed to work in the fishery biology field. Additional background material was provided by a review of current progress on Atlantic herring (Clupea harengus) population biology. A hypothesis concerning population regulation of herring in the oceans was discussed, posing questions pertaining to the number of populations, levels of absolute abundance and controlling mechanisms of interannual variability in abundance, and variability in spawning times between populations. A review of the literature revealed, ?some characteristics of the population biology are simply not addressed.? With respect to herring, ?spatial constraints are considered to be important to the diverse aspects of the population regulation problem.?

A member/vagrant hypothesis was introduced ?to explain and describe what regulates populations of sexually reproducing marine species.? Three statements comprised this hypothesis, which ?emphasizes the importance of spatial constraints in the oceans to life-cycle closure.? First, ?population pattern and richness are functions of the number and location of geographic settings (within the overall distributional area of the species) within which the species? life cycle is capable of closure.? Second, ?absolute abundance is scaled according to the size of the geographic area in which there is closure of the life cycle of the free crossing population.? Third, ?temporal variability in abundance is a function of the intergenerational losses of individuals (vagrancy and mortality) from the distributional area that will ensure membership within a given population.? Physical oceanographic processes were considered in large part to regulate populations containing species with complex life histories. It was concluded that for such species with complex life histories, ?population regulation does not necessarily require competition for limited resources or food-chain interactions for stability.? Marine literature mostly since the 1960?s was then reviewed to lend support for this hypothesis and ?implications for selected ecological issues? were discussed. It was argued ?that life-cycle selection plays the predominant selective role in speciation (the origin of reproductive isolation), with food-chain selection involved in so-called energetics adaption.?

Solazzi, M.F., T.E. Nickelson, and S.L. Johnson.

1991

Survival, contribution, and return of hatchery coho salmon (Oncorhynchus kisutch) released in freshwater, estuarine, and marine environments.

Canadian Journal of Fisheries and Aquatic Sciences 48:248-253.

Columbia River, estuary, juvenile coho salmon, survival, hatchery

For five consecutive years, six groups of marked yearling hatchery coho salmon were released each year at six locations in the lower Columbia River and estuary system to assess survival rates. This experiment was designed to identify river, estuary or ocean locations where a survival "bottleneck" may arise for coho salmon, as well as establishing if the total contribution of in-river fisheries differed among the six groups. Previous studies outlining some of the factors affecting survival of juvenile salmon were noted.

The release sites were immediately downstream of the Bonneville Dam (control), head of saltwater intrusion, Columbia River bar, in the Columbia River plume, in coastal water north of the plume, and in the ocean approximately 38 km from shore. Coho salmon were released at the Bonneville Dam site two weeks before the other groups. Fish from the other groups were transported via truck to the respective release locations. Commercial and recreational catches in the ocean provided estimates from each release group; otherwise tags were recovered from returning adults at the hatchery of origin.

The most significant discovery found the coho salmon released at the head of saltwater intrusion (estuarine point) exhibited greater survival (and thus contribution to the gillnet fishery) compared to fish released at the river location near Bonneville dam (control group), despite transportation stress to the release point. This conclusion tended to support preliminary results from other studies reporting increased survival with release of juveniles directly into the estuary. A survival bottleneck likely exists in the lower Columbia River, though it does not explain the inter-annual variation for survival of the release groups. No significant difference in survival was observed between the other release groups and the control group.

Tallman, R.F., and M. C. Healey.

1991

Phenotypic differentiation in seasonal ecotypes of chum salmon, Oncorhynchus keta.

Canadian Journal of Fisheries and Aquatic Sciences 48:661-671.

British Columbia, chum salmon, phenotype, genetics, spawning, reproduction, timing, migration, morphology

This study tested the hypothesis that phenotypic differences between early and late season breeding stocks of chum salmon (Oncorhynchus keta) in two closely located coastal creeks on Vancouver Island correspond to ?adaptations to the season of reproduction rather than adaptations to geographic location.? The morphology, incubation environment, and seasonality between the autumn (Bush Creek) and winter (Bush Creek, Walker Creek) spawning populations were compared. Approximately two months separate the start, peak and end of reproduction for these populations, as revealed by thirty years of escapement records. The timing of downstream migration of fry was similar for the chum stocks. From 1981-1984, in-stream spawners were counted in both creeks from September through February. Spatial barriers were absent in both creeks after mid-November. Sampling methods and statistical calculations were discussed.

Chum fry from the single autumn run and two winter runs emerged and migrated ?in relative synchrony? even though eggs were deposited during different seasons. The majority (95%) of the fry from both creeks migrated at night. Differences were not evident in age at maturity, spawner length, egg size, vertebrae counts, and timing of fry migration between the Walker Creek and Bush Creek autumn runs. The winter run of Bush Creek exhibited differences from the other runs in egg size and vertebral counts. Fewer temperature units were required by the winter runs versus the early run to achieve emergence. It was concluded, ?these results do not support the hypothesis that distinct life history morphs are associated with the season of reproduction.? Rather, selection may be responsible for the great similarity in morphology and seasonality between the chum runs. Finally, ?genetic divergence may have occurred to compensate for the environmental differences experienced during embryonic development.?

Taylor, E. B.

1990

Environmental correlates of life-history variation in juvenile Chinook salmon, Oncorhynchus tshawytscha (Walbaum).

Journal of Fish Biology 37:1-17.

North Pacific, juvenile Chinook salmon, life history, migration

A summary of life-history variations in juvenile Chinook is provided from literature sources and other available data. Two basic life-history patterns are followed, "stream-type" Chinook that migrate to sea after one or more years rearing in fresh water, and "ocean-type" Chinook that migrate to sea after only several months rearing in fresh water.

Stream-type Chinook predominate in populations north of 56?N and in inland populations south of this line. Ocean-type Chinook predominate in coastal populations south of 56?N, but are rare in populations north of this line. Environmental factors exert a strong influence on age at seaward migration in these populations, especially "growth opportunity." In areas of low growth opportunity as measured by temperature and photoperiod and/or distance from the sea tend to have stream-type populations.

Teel, D.J., G.B. Milner, G.A. Winans, and W.S. Grant.

2000

Genetic population structure and origin of life history types in chinook salmon in British Columbia, Canada.

Transactions of the American Fisheries Society 129:194-209.

British Columbia, Chinook salmon, genetics, diversity, population, life history, hatchery

Genetic population structure and origin of life history types of Chinook salmon (Oncorhynchus tshawytscha) were examined from 63 populations in British Columbia Rivers and hatcheries. Ninety-one samples were collected from 1981 to 1991; the genetic data were used in previous studies. The distribution of genetic diversity among populations was estimated at three hierarchical levels (rivers, areas, regions). Cluster analyses were used to infer genetic relationships between Chinook populations, searching for patterns of divergence in accordance with distributions of ocean- and stream-type life history types.

Within British Columbia, intermediate levels of within-population genetic variability were observed in Chinook when compared to populations from other regions. A high degree of allele-frequency variability among Chinook populations was seen at all levels of the geographic hierarchy in British Columbia. Two analyses of genetic distances revealed two primary groups of populations: a coastal group and an inland group, each composed of a number of sub-groups (i.e., rivers and regions in British Columbia). The geographic extent of both groups ?largely coincided with the geographic distributions of stream- and ocean-type juvenile forms and may reflect postglacial colonization by two ancestral lineages that survived in Pleistocene refugia.? The results suggested a long period of genetic isolation between inland (stream-type) and coastal (ocean-type) Chinook populations. Zoogeographic explanations for the appearance of different life history types were discussed, for example ocean-type life history occurrence in southern British Columbia. Finally, ?the presence of genetically undifferentiated stream-type fish in coastal streams populated by ocean-type fish may reflect either postglacial life history differentiation from ancestral ocean-type fish or life history flexibility of ocean-type fish.?

Trenberth, K.E.

1990

Recent observed interdecadal climate changes in the northern hemisphere.

Bulletin American Meteorological Society 71: 988-993.

Climate, marine, Northern Hemisphere, sea-surface temperature, El Nino/Southern Oscillation, La Nino

Surface temperature anomalies in the Northern Hemisphere prior to 1988 (in particular, 1977-1988) were investigated. Large-scale sea-surface temperature trends, causes of climate variations and potential links with the greenhouse effect were addressed. Differences in surface temperatures over Alaska versus the North Pacific Ocean, atmospheric dynamics and local/regional physical processes affecting temperature change, mixing, circulation and winds, El Nino/Southern Oscillation and La Nino events were discussed.

Tschaplinski, P. J.

1987

The use of estuaries as rearing habitats by juvenile coho salmon.

Pages 123-147 in Chamberlin, T.W. ed. Proceedings of the workshop: applying 15 years of Carnation Creek results. Pacific Biological Station, Nanaimo, British Columbia.

British Columbia, estuary, juvenile coho salmon, rearing, habitat, timing, predation, survival, growth rate, diet, food

Coho (Oncorhynchus kisutch) fry used the upper intertidal zone of a small estuary at the mouth of Carnation Creek for rearing from shortly following emergence, through the summer. Fry remained within salinities of about 15% until late in the summer, when they either returned to the stream for the winter, or moved offshore into higher salinity water. Most dispersed seaward into Barkley Sound.

Coho fry in the estuary preferred depths of 45-225 cm, cover in the form of under cut banks (often with overhanging vegetation), and masses of large debris (tree roots, logs or fallen trees).

Coho fry rearing in the estuary rapidly outgrew their stream dwelling counterparts. The fry consumed mostly prey from drift, with feeding activity significantly elevated by tidal currents. Most feeding movements occurred during flood tide or within the first hour of receding tides. Prey species consumed were highly variable. Chironomids and amphipods (Corophium spinicorne, Eogammarus confervicolus) were the most important (61-89%) prey items in the estuary. Isopods (Gnorimosphaeroma oregonense) were also consumed by the fry. The coho fry were judged to be generalist predators. Potential prey items such as fish larvae and oligochaete worms were either avoided or unavailable to the fry.

Walters, C.J., R. Hilborn, R.M Peterman, and M.J. Staley.

1978

Model for examining early ocean limitation of Pacific salmon production.

Journal of Fisheries Research Board Canada 35:1303-1315.

British Columbia, juvenile, Pacific salmon, marine, growth rate, survival, productivity, population, food, simulation model, density dependence

A result of a workshop, this paper described the use of a computer simulation model to synthesize coastal production with respect to potential limits for Pacific salmon (Oncorhynchus spp.). Growth and survival were examined during approximately the first three months of ocean life for all the major salmon stocks entering marine waters from British Columbia Rivers. Numerous scientists collaborated on the development of this model. Rather than provide ?firm predictions of ocean capacity,? the objectives were to demonstrate the feasibility of large-scale predictions, and identify data gaps that hinder predictions from being ?believable.? Four components of production were incorporated into the model: spatial and temporal distribution of zooplankton abundance, feeding and growth of young salmon with regard to food availability, mortality rates with regard to body size, and timing of arrival at ocean and coastal migration.

Trophic relationships were emphasized as potential limits to salmon enhancement. The model was unable to identify subtle problems related to seasonal and spatial arrangement of juvenile fish and food. Food production in the coastal region was sufficient to support existing and greater abundances of juvenile salmon. It was concluded ?ocean limitation of production is unlikely unless only a small fraction of total zooplankton production is available to the salmon.? Numerous assumptions, predictions and uncertainties were stated. Key uncertainties pertaining to trophic relationships were discussed (e.g., inadequate measurements of zooplankton replenishment to near surface areas, poorly understood salmon response to prey density and relationship between body size and mortality rates, and poorly documented migration patterns of juvenile fish).

Wissmar, R., and C.A. Simenstad.

1998

Variability of riverine and estuarine ecosystem productivity for supporting Pacific salmon, pp 253-301. In: Change in Pacific Northwest Coastal Ecosystems G.R. McMurray and R. J. Bailey (eds).

NOAA Coastal Ocean Program, Decision Analysis Series No. 11.

Pacific Northwest, Chinook salmon, chum salmon, pink salmon, sockeye salmon, coho salmon, estuary, riverine, productivity, habitat, processes, scale, growth rate, food web, survival, life history

Part of a larger body of work, this chapter reviewed important characteristics of riverine and estuarine habitats in the coastal regions of the Pacific Northwest with respect to utilization of habitats by the five species of Pacific salmon (Oncorhynchus spp.). Three main sections were included: ecosystem variability and scales influencing juvenile salmon growth and survival; summaries of juvenile salmon life histories and genetic diversity variation; and suggested future research.

Productivity is variable in riverine and estuarine ecosystems when supporting and sustaining juvenile Pacific salmon populations. River drainage physiographic character and variability and productivity of these ecosystems were discussed first. Variability in climate, hydrology, geomorphology and life history types and their importance to riverine ecosystem productivity was described. Biological productivity of riverine systems and implications to juvenile salmon was discussed. Physiographic characteristics of estuarine ecosystems (circulation, salinity) in the Pacific Northwest were described as variable. A lengthy discussion of productivity in estuarine ecosystems was provided. Estuarine production was described as ?extremely pulsed? and variability can be predictable, subtle or stochastic. Food webs and the timing, quantity, quality and pathways for distribution were covered in some length (e.g., detritus, nutrient budgets, isotopic analyses, carrying capacity). Human actions and the ensuing degradation of riverine and estuarine ecosystems were addressed.

Pacific salmon adaptation, population resilience and life history diversity were discussed in the next section. The principal river systems producing Pacific salmon populations in the Pacific Northwest (coastal, Puget Sound) were outlined. The diversity of Pacific salmon life histories for the five species (Chinook [O. tshawytscha], chum [O. keta], coho [O. kisutch], sockeye [O. nerka], pink [O. gorbuscha]) was described. Life history traits were presented in tabular form and life history pathways of chum, coho, sockeye, and stream-type and ocean-type Chinook salmon were presented in graphical form. Next, genetic diversity, local and regional scales, a case study of chum salmon life history diversity, and historical salmon management was discussed.

The final section of the chapter addressed the need for additional research pertaining to the variability of riverine and estuarine ecosystems, the recovery of salmon populations, salmon life history, and predation issues. Select research questions were also offered.