William W. Smoker

Hatchery Reform in Washington State

Abstract Hatcheries support nearly all major fisheries for Pacific salmon (Oncorhynchus spp.) and steel-head (anadromous O. mykiss) in the Pacific Northwest. However, hatcheries have been a major source of controversy for over 30 years. The Hatchery Scientific Review Group (HSRG) was tasked by Congress to identify solutions to well-known problems so hatcheries could better meet their goals of supporting sustainable fisheries and assisting with the conservation of natural populations. We reviewed over 100 facilities and 200 programs and identified three principles of hatchery reform: (1) goals for each program must be explicitly stated in terms of desired benefits and purposes; (2) programs must be scientifically defensible; and (3) hatchery programs must respond adaptively to new information. We also identified several emerging issues critical to the success of hatcheries. We concluded that hatcheries must operate in new modes with increased scientific oversight and that they cannot meet their goals witho...

Outbreeding depression in hybrids between odd- and even-broodyear pink salmon

Abstract Fewer F 2 hybrids between even- and odd-broodline pink salmon ( Oncorhynchus gorbuscha ), which are lines that are genetically isolated by their strict two-year life cycle, survived than did F 2 controls, indicating outbreeding depression. Cryopreserved sperm of 40 broodyear 1990 males and of 40 broodyear 1991 males fertilized equal subsamples of eggs from 40 broodyear 1992 females. Return rates of F 1 hybrids (1.73%) and controls (1.63%) in 1994 did not differ significantly ( P =0.30). F 2 hybrid and control crosses were made from 40 males and 40 females selected at random from each return group. Offspring were differentially marked and released. In 1996, returns differed significantly ( P =0.011) between hybrids ( n =34, 0.34%) and controls ( n =44, 0.42%). The low rate of return of the control fish was similar to the measured return of a much larger group of tagged Auke Creek pink salmon, and probably not an artifact of the experiment. Although no increase in fluctuating asymmetry of paired meristic counts was observed in either F 1 or F 2 hybrids, size and some meristic counts of hybrids exceed measurements of controls, suggesting heterosis for those traits. The observations of decreased survival in F 2 hybrids confirm previous work [Gharrett, A.J., Smoker, W.W., 1991. Two generations of hybrids between even- and odd-year pink salmon ( O. gorbuscha ). Canadian Journal of Fisheries and Aquatic Science 48(9) 1744–1749]. Although genetic divergence between pink salmon broodlines is large and outbreeding depression might be expected in such unlikely hybrids, the results document the occurrence of outbreeding depression in salmon and signal caution in making management and aquacultural decisions that may create the possibility of outbreeding depression in self-sustaining or cultured populations.

Outbreeding depression in hybrids between spatially separated pink salmon, Oncorhynchus gorbuscha , populations: marine survival, homing ability, and variability in family size

Hybridization between distinct populations and introgression of nonnative genes can erode fitness of native populations through outbreeding depression, either by producing a phenotype intermediate to that of both contributing genomes (and maladapted in either populationi¯s environment) or by disrupting distinct coadapted complexes of epistatic genes. In salmon, fitness-related traits such as homing ability or family-size distribution may be eroded. We investigated geographically separated pink salmon populations in repeated trials in independent broodyears (odd and even). Hybrids were made between female Auke Creek (Southeast Alaska) pink salmon and Pillar Creek (Kodiak Island, ∼1 000 km away) males; hybrids and their offspring were compared to offspring of control crosses of the same females with Auke Creek males. Parentage assignment from microsatellite analysis was used to improve estimates of survival and straying and to examine variation of family size. Hybridization reduced return rates of adults (a proxy for survival at sea) in the F1 generation in the odd-year broodline (p < 0.0001) but not in the even-year broodline (p = 0.678). Hybridization reduced survival in both the odd- and even-broodyear F2 (p < 0.005 and p < 0.0001). Hybridization did not appear to impair homing ability; weekly surveys revealed similar straying rates (∼2%) by both hybrid and control fish into nearby (∼1 km) Waydelich Creek in both generations in both trials. Hybridization did not increase the index of variability (μ2 /μ;) in family size. Decreased survival in the hybrid F2 generation supports an epistatic model of outbreeding depression; nonepistatic effects may have contributed to reduced survival in the odd-broodyear F1 hybrid fish. Outbreeding depression in hybrids of geographically separated populations demonstrates that introgression of nonnative fish can erode fitness, and should be recognized as a potential detriment of both aquaculture and management practices.

A perspective on the adaptive importance of genetic infrastructure in salmon populations to ocean ranching in Alaska

Abstract Salmon hatcheries, like other resource management practices and tools, potentially have genetic effects on wild-spawning populations of salmon. These effects, which theory predicts will erode vital genetic diversity, would be expected to operate through straying and gene introgression, and through other processes. Genetic diversity among populations is well known from analysis of neutral biochemical traits and is less well known from observation of polygenic, ecologically adaptive, phenotype differences. We note increasing evidence of adaptively important polygenic genetic diversity within populations and evidence that this variability is partitioned temporally or spatially among distinct segments of salmon populations, a partitioning we call infrastructure. For example, in one well-studied small population, Auke Creek pink salmon, there is evidence of genetically based variability of timing of anadromous migration and simultaneous evidence of the importance to survival of that timing. We believe that the adaptedness and productivity of salmon stocks are dependent on genetic infrastructure; fisheries management practices, including enhancement of harvests by hatcheries and ocean ranching, potentially reduce genetic infrastructure as they may reduce other levels of genetic diversity. Rational resource management should seek to conserve genetic diversity at all levels. Treatment of salmon stocks as homogeneous units, neglecting within-stock diversity or infrastructure, will not be adequate to conserve fitness and productivity of these commercially valuable resources.

Comment: A Review of the Hatchery Programs for Pink Salmon in Prince William Sound and Kodiak Island, Alaska

Recently, Hilborn and Eggers (2000) have asserted that hatcheries in Prince William Sound (PWS), Alaska, have caused a decline in the productivity of wild pink salmon Oncorhynchus gorbuscha in PWS and that hatchery fish to a large degree have replaced, not enhanced, pink salmon returns. Pink salmon catches in PWS are currently at historic highs, averaging 27 million fish per year over the past decade. Over 85% of the harvest is from a system of large hatcheries (Pinkerton 1994; McNair 2000). There is concern that hatchery production may have been deleterious to wild pink salmon in PWS, complicating management and the achievement of escapement goals and reducing productivity (e.g., Tarbox and Bendock 1996). Hilborn and Eggers estimate that more than 90% of the recent annual production would have been attained by wild stocks alone in the absence of hatchery production. We, however, find compelling evidence that hatchery fish have greatly increased the total pink salmon harvest in PWS and that Hilborn and Eggers’s estimates of wild stock productivity in the hypothetical absence of hatchery fish are not credible. While countervailing trends in the abundance of wild and hatchery pink salmon in PWS superficially appear to support Hilborn and Eggers’s arguments, careful consideration of the evidence indicates that the program has had substantial net benefits. We address three central points of the Hilborn and Eggers paper: (1) that retrospective analysis indicates that the proportional increases in pink salmon production in PWS have been similar to those in regions of Alaska without major hatcheries, on the basis of which Hilborn and Eggers conclude there is no evidence from between-region comparisons that the large increases in the catch in PWS were due to hatcheries; (2) that, because wild stock productivity is correlated negatively with the magnitude of fry releases from hatcheries, wild stock fish would have produced more than 90% of the current record runs in PWS in the absence of hatcheries; and (3) that wild stock escapements (i.e., the number of reproducing wild salmon) have declined due to deleterious interactions with salmon released from hatcheries. Proportionality Argument

Relationship of size at return with environmental variation, hatchery production, and productivity of wild pink salmon in Prince William Sound, Alaska: does size matter?

Pink salmon (Oncorhynchus gorbuscha) returning to Prince William Sound (PWS), Alaska, have increased to historically high levels of abundance in recent years, but average body size at return has declined. We examined how body size at return of PWS pink salmon was related to 10 biophysical factors, including the scale of hatchery production. We also examined the effect of body size at return on productivity of wild pink salmon in PWS. For the 1975–1999 brood years, we found that an index of total abundance of pink salmon in the Gulf of Alaska and sea surface temperature during the year of return best explained the variation in pink salmon body size over time. Body size at return was significantly correlated with productivity of wild pink salmon. We used stepwise-regression to fit a generalized linear version of the Ricker spawner-recruit model to determine if body size would explain significant variation in wild-stock productivity in context with other environmental variation, including hatchery production. The results indicate that variability in wild-stock productivity is primarily driven by density-independent factors in the marine environment, but that body size of wild spawners also significantly affects productivity of wild PWS pink salmon. We conclude that the success of large-scale enhancement increasing the total run in PWS may have contributed to the decline in body size because of density-dependent growth in the Gulf of Alaska. We used a simulation model to estimate the impact of hatchery-induced changes in adult body size on wild-stock production in PWS. We estimated an annual wild-stock yield loss of 1.03 million pink salmon, less than 5% of the annual hatchery return of 24.2 million adult pink salmon for brood years 1990–1999.

Spawning Habitat Segregation of Sympatric Sockeye and Pink Salmon

Abstract Spatiotemporal distributions and microhabitat use of pink salmon Oncorhynchus gorbuscha and sockeye salmon O. nerka were studied in Lake Creek, southeast Alaska, during three spawning seasons. Sockeye salmon migrated approximately 1 week earlier than pink salmon and spawned 250–350 m upstream from pink salmon. Habitat overlap measured with proportional similarity index monotonically increased with increasing spawner densities. Multidimensional niche spaces measured with water depth, current velocity, and channel gradient at redds were significantly different between pink and sockeye salmon (P < 0.005, Hotellings T 2-test). However, classification of the redds into individual species was subjected to large error rates; 33% of 70 pink salmon redds and 34% of 125 sockeye salmon redds were misclassified. Competitive interaction between pink and sockeye salmon was not demonstrated.

Fine‐scale temporal adaptation within a salmonid population: mechanism and consequences

We demonstrate a clear example of local adaptation of seasonal timing of spawning and embryo development. The consequence is a population of pink salmon that is segmented into spawning groups that use the same limited habitat. We synthesize published observations with results of new analyses to demonstrate that genetic variation of these traits results in survival differentials related to that variation, and that density‐dependent embryo mortality and seasonally variable juvenile mortality are a mechanism of selection. Most examples of local adaptation in natural systems depend on observed correlations between environments and fitness traits, but do not fully demonstrate local adaptation: that the trait is genetically determined, exhibits different fitness in common environments or across different environments, and its variation is mechanistically connected to fitness differences. The geographic or temporal scales of local adaptation often remain obscure. Here, we show that heritable, fine‐scale differences of timing of reproductive migration in a pink salmon (Oncorhynchus gorbuscha) resulted in temporal structure that persisted several generations; the differences enable a density‐dependent population to pack more spawners into limited spawning habitat, that is, enhance its fitness. A balanced trade‐off of survivals results because embryos from early‐migrating fish have a lower freshwater survival (harsh early physical conditions and disturbance by late spawners), but emigrant fry from late‐migrating fish have lower marine survivals (timing of their vernal emergence into the estuarine environment). Such fine‐scale local adaptations increase the genetic portfolio of the populations and may provide a buffer against the impacts of climate change.

Variation of Morphology among Juvenile Chinook Salmon of Hatchery, Hybrid, and Wild Origin

Abstract Body morphology differed significantly between juvenile hatchery Chinook salmon Oncorhynchus tshawytscha that have experienced five generations of hatchery culture and juveniles derived from the wild founding stock and cultured in the same environment. All lines tested were raised in a similar hatchery environment. Thin-plate spline analysis was used to characterize the morphometric variation among these lines of fish. Hatchery fish had a more compressed body, a narrower head, shorter maxillae, and a longer and narrower caudal peduncle than wild fish. Canonical discriminant analysis was able to correctly classify 88% of hatchery fish and 90% of wild fish. Second-generation hybrids of the two lines were morphologically intermediate to but significantly different from both the hatchery and wild lines, and they appeared to be more similar to the wild line. These results suggest that the differences observed between lines are largely genetic in origin and may be a result of the divergence of the hatc...

Ecological interactions between wild and hatchery salmonids and key recommendations for research and management actions in selected regions of the North Pacific

Advances in salmon culture practices during the latter part of the 20th century provided the opportunity for mass production of juvenile salmon. Hatchery-produced salmon currently outnumber wild salmon in some regions around the Pacific Rim, raising concerns about their ecological impacts on wild salmon. We convened five regional sessions at an international conference to identify and discuss issues related to ecological interactions between wild and hatchery salmon. Session participants were charged with identifying key interaction types by salmon life stage. Each group was asked to summarize key research needs and identify management actions that might be needed to reduce risks from hatchery programs. Some common themes emerged in all the sessions, including the importance of predation and competition interactions in freshwater environments during juvenile life stages and breeding interactions among adults. Much less is understood about interactions in estuarine and marine ecosystems, even though these environments may be critical in determining recruitment success. Some groups identified a need for field experiments to test hypotheses related to ecological interactions and the need to understand and, where possible, control hatchery straying. Some groups also discussed the importance of carrying capacity in different environments and how hatchery programs may be contributing to density-dependent effects. There is a lack of focused studies on ecological interactions between wild and hatchery salmon in the Western Pacific. The authors of this paper hope to encourage new research efforts to better understand ecological interactions to help inform management efforts aimed at reducing hatchery risks to wild salmon.