Wild Salmon Stocks Research Articles

Salmon policy: science, society, restoration, and reality

Salmon policy in the Pacific Northwest illustrates a class of contentious, socially wrenching issues that are becoming increasingly common in the western United States as demands increase for limited ecological resources. Many Pacific salmon “stocks” (a term used in fisheries management for a group of interbreeding individuals that is roughly equivalent to “population”) have declined and some have been extirpated. The salmon “problem” is one of the most vexing public policy challenges in natural resource management. Even with complete scientific knowledge — and scientific knowledge is far from complete or certain — it would be a challenging policy problem. The salmon decline issue is often defined simplistically as a watershed management problem, in part because changes in watersheds are highly visible and often occur on public or corporate lands where individuals and organizations often have direct input to decision making. Yet, changes in climate and ocean conditions, for example, occur frequently and such changes have a major influence on salmon abundance. The scientific challenges are great, but the more difficult — and critical — aspect of the debate concerns policies and decisions affecting everyone, including those involved in rural enterprises (especially farming and logging); manufacturing and construction; electricity generation (including hydro, fossil fuel, and nuclear); national defense; urban development; transportation (including road, rail, air, and water). The debate also involves competing personal rights and freedoms; the prerogatives and roles of local, state, and federal government and Indian tribes; policies on human population level, reproduction, emigration, and immigration; and the future of fishing (commercial, recreational, and Indian). The salmon policy conundrum is characterized by: (1) nearly everyone claims to support maintaining wild salmon runs; (2) many competing societal priorities exist, many of which are partially or wholly mutually exclusive; (3) the region’s rapidly growing human population creates increasing pressures on all natural resources (including salmon and their habitats); (4) policy stances in the salmon debate are solidly entrenched; (5) society expects salmon experts to help solve the salmon problem; (6) each of the many sides of the political debate over the future of salmon use salmon experts and scientific “facts” to bolster its argument; (7) it has proved to be nearly impossible for salmon scientists to avoid being categorized as supporting a particular policy position; and (8) many advocates of policy positions couch their positions in scientific terms rather than value-based preferences. Although far from indisputable, I conclude that over the next century and allowing for considerable year-to-year and decade-to-decade variation, many, perhaps most, stocks of wild salmon in the Pacific Northwest likely will remain at their current low levels or continue to decline in spite of costly protection and restoration efforts.

The incidence of escaped farmed Atlantic salmon, Salmo salar L., in the Faroese fishery and estimates of catches of wild salmon

Hansen, L. P., Jacobsen, J. A., and Lund, R. A. 1999. The incidence of escaped farmed Atlantic salmon, Salmo salar L., in the Faroese fishery and estimates of catches of wild salmon. ‐ ICES Journal of Marine Science, 56: 200‐206. The proportion of Atlantic salmon escaped from fish farms and caught in the Faroese salmon fishery was estimated using scale analysis. Samples were obtained of fish landed in the commercial fishery from 1980/1981 to 1990/1991 fishing seasons and from research catches in the 1991/1992 to 1995/1996 seasons. The material collected was in some years limited to only part of the fishing season. The estimated proportion of farmed salmon in the fishery was relatively low from 1980/1981 to 1986/1987, but increased considerably thereafter, and reached a peak in the 1989/1990 fishing season when more than 40% of the catch was estimated to be of farmed origin. Later, the proportion declined, and in recent seasons the proportions of farmed salmon were estimated to be around 20%. These estimates were used to split the Faroese catch into wild and farmed components. It is concluded that if farmed components in salmon catches are not accounted for, catches of wild salmon will be overestimated and assessments of fisheries and stocks of wild salmon confounded. Furthermore, the increase observed in catch per unit of eVort (c.p.u.e.) in the 1980s and early 1990s might have been caused by an increasing abundance of farmed salmon. ? 1999 International Council for the Exploration of the Sea

Effect of Pollution on Fish Diseases: Potential Impacts on Salmonid Populations

Anthropogenic factors have contributed to the precipitous decline of wild Pacific salmon stocks, although the mechanisms and processes at work are largely unknown. Pollution may be one of these factors. Sediments in estuaries are known to act as repositories for contaminants, and estuaries are important habitats for ocean- and river-migrating salmon. We have shown that juvenile salmon Oncorhynchus spp. and their prey bioaccumulate chlorinated hydrocarbons and aromatic hydrocarbons—important classes of toxic xenobiotics. Furthermore, we have shown that exposure to these pollutants can lead to immunosuppression and increased disease susceptibility in juvenile salmon. Whether pollution influences natural disease outbreaks in host populations, including salmon, is currently unknown. It is postulated that the occurrence of disease depends on the interaction of the host, the environment, and the pathogen. Absence of pathogens would reduce the potential for adverse environments to influence disease outbreaks. However, a recent reconnaissance survey of juvenile chinook salmon Oncorhynchus tshawytscha from Oregon coastal rivers revealed that pathogens were an integral component in all systems studied, although the prevalence of the pathogens varied. Furthermore, recent studies of natural fish populations have demonstrated that infectious-disease-induced mortality can significantly reduce the size of the host population. By creating adverse environments (e.g., polluted estuaries) which alter the susceptibility of the host to pathogens that are integral and ubiquitous components of the habitat, pollution increases the probability of disease-related impacts on fish populations.

The advantage of using smolt age with allozymes for assessing wild stock contributions to Atlantic salmon catches in the Baltic Sea

Information about the occurrence and proportions of endangered wild Atlantic salmon stocks in Baltic Sea catches is invaluable to the fishery managers responsible for sustaining these populations. The usefulness of stock mixture analysis (SMA) from characters of sampled fish was evaluated by applying the method in an estimation of actual and simulated catch compositions. Samples for seven variable genetic loci, expressed by allozymes, and smolt age from 17 stocks from Finland and Sweden which are potential contributors to the fishery were used with similar samples collected in 1993 from catches in a Finnish trapnet fishery along the east coast of the Bothnian Sea. Identified by their character similarities, three stock management units and their estimated catch contributions were: resident Neva stock (29%), wild baseline stocks (28%), and migratory hatchery stocks (43%). The contributions of the units varied during the fishing season. With allozyme data alone, the management units were not so distinctive. Nevertheless, three major wild stocks (Tornionjoki, Kalixalven, and Simojoki), which accounted for 68% of the total wild smolt production of the area, were similar in their allozymes and distinctive from the other stocks. The increase in reliability of wild stock composition estimates when smolt age was added to the allozyme loci was evaluated by simulation. Smolt age improved the precision of composition estimates for both the combined wild baseline stocks and their aforementioned subset comprising three major stocks; it controlled bias better for the combined wild baseline stocks than their subset.

Hatchery and wild production of Pacific salmon in relation to large-scale, natural shifts in the productivity of the marine environment

Pacific salmon have been fished extensively for at least a century and artificial production of Pacific salmon has been a management strategy to improve production for almost as long. Hatchery production is considered important because it is commonly believed that the carrying capacity for salmon in the ocean has remained more or less constant and is underutilized as a consequence of limited production of smolts in fresh water. Since the mid-1960s, there has been an increase in hatchery production, partly as a response to a desire to increase catch and partly because of improved hatchery techniques. Since the late 1970s there has been a dramatic increase in the total Pacific salmon catch. The increases in catch are now known to result from a large-scale shift in the productivity of the sub-arctic Pacific and management and enhancement actions. Environmental indices changed about 1989-1990 and may indicate that the productive regime of the 1980s has ended. This would imply that under natural conditions Pacific salmon abundance would decline. There are no clear indications of what to expect in the new regime, but it is apparent that the massive production of artificially reared Pacific salmon would not be necessary in a less productive regime. Of concern is the impact that the large numbers of artificially reared salmon will have on wild salmon stock levels.

Implications of Trends in Marine-derived Nutrient Influx to South Coastal British Columbia Salmonid Production

Marine nutrients and carbon transported by adult salmon are important to the productivity of the oligotrophic lakes and streams in which salmon spawn. Reduced carcass availability results in a decline in nutrient and carbon sources for stream-rearing salmonids. We examined 42 years of escapement records for five species of Pacific salmon for Georgia Strait, the west coast of Vancouver Island, and the mainland coast of British Columbia to estimate the status of this nutrient source. Salmon stocks from enhanced streams frequently dominated the total escapement of entire regions. As a result, most of the influx of marine nutrients is focused toward a few large stream systems already undergoing significant salmon enhancement, while nutrient influx to the more-numerous unenhanced streams is declining. In the large number of streams with smaller salmon escapements, stream-rearing species already in decline may decrease further from oligotrophication. Risk-averse escapement targets for wild salmon stocks need to include sufficient spawners to provide the nutrient influx linked to the maintenance of stream productivity. Declining trends in nutrient influx to wild salmon streams in most regions are a cause for concern and more intensive examination.

Joint use of multiple environmental assessment models by a Bayesian meta-model: the Baltic salmon case

An approach to construct a meta-modeling framework using Bayesian calculus is presented. It allows the inclusion of several—both causal and empirical—models in a Bayesian belief network that is capable of real-time updating of uncertainties in the system. The approach can be used for diagnosis and forecasting purposes. It is illustrated with the assessment problem of the threatened, wild salmon stocks in the Baltic Sea. As usual, the institutions responsible for the management are prone to accept well-known standard assessment models. In this case, the Virtual Population Analysis approach and a set of regression models have been used. A debate on possible superiority of one or more of these models over the others is met at each annual international negotiation among stock assessment experts. The need has arisen to develop a methodology that would allow analytic fusion of these models to learn from the properties of the models and from the problem setting in general, as well as to facilitate probabilistic predictions that would utilize as much of the available information as possible. Moreover, the probabilistic approach is very compatible with and supportive to the use of the precautionary principle (risk-averse attitude). The belief network approach has shown appropriateness for handling of this type of problem in environmental and resource management.

Post-vaccination intra-abdominal adhesions as a marker to identify Atlantic salmon, Salmo salar L., escaped from commercial fish farms

Intraperitoneal vaccination of Atlantic salmon, Salmo salar L., against furunculosis using oil adjuvanted vaccines causes visible intra-abdominal markers of apparently permanent character. The feasibility of these side-effects for discrimination between fish from vaccinated and unvaccinated populations was evaluated in an open study using samples of vaccinated and unvaccinated farmed salmon, and in a blind study using individually tagged fish from a sea ranching vaccination trial. Vaccines were trivalent, oil adjuvanted bacterins extensively used in Norwegian aquaculture. Adhesions between internal organs and the gut wall were more sensitive and more specific for identifying fish from vaccinated populations than pigmentations on the peritoneum or on the viscera of the fish. Samples of farmed fish drawn from 3 to 35 months after vaccination yielded sensitivities of 93–100% and a specificity of 100% for this marker trait. In the blind study, intraperitoneal inoculation of saline as a placebo was found to induce minor adhesions, thus reducing the specificity of the adhesion marker to 75%. Using the observed sensitivities and specificities in a data simulation, the intra-abdominal adhesion marker proved feasible for the identification of fish from unvaccinated populations even under unfavourable sampling situations. Provided the current practices of vaccinating farmed salmon prevail, exclusion of individual fish carrying the intra-abdominal adhesion marker is recommended when estimating the number of wild salmon stocks, and when selecting broodfish for propagation of specific river populations of Atlantic salmon.

Supplementation of wild salmon stocks: A cure for the hatchery problem or more problem hatcheries?

Supplementation is a hatchery technology that attempts to correct for many of the problems associated with traditional hatcheries. Indian tribes along the Columbia River plan to use this technology to restore many of the badly damaged runs in the basin. The technology is not without risk to wild fish populations, however, and a rift has developed between the tribes and conservation groups, which generally oppose the construction of any new hatcheries intended to augment production. The Endangered Species Act, the National Environmental Policy Act, the Northwest Power Act, and tribal treaty rights all play a role in the current conflict. The author examines the scientific, legal, and policy positions on the two sides of the debate and offers possible solutions.

High numbers of farmed Atlantic salmon. Salmo salar L., observed in oceanic waters north of the Faroe Islands

. To estimate the proportion of escaped fanned Atlantic salmon. Salmo salar L., at the feeding grounds in the north-east Atlantic Ocean, samples of salmon caught with long-lines north of the Faroe Islands were examined. Identification of reared fish was carried out using scale analysis. The proportion of fanned fish was estimated to range from 25 to 48% in the different samples, suggesting that high numbers of escaped farmed salmon occur in the Norwegian Sea. The farmed fish were significantly smaller in size than the wild salmon. Although it is suggested that most of the farmed fish are of Norwegian origin, farmed fish of Scottish, Faroese and Irish origin are also believed to be present. If not accounted for, high numbers of reared salmon in fisheries and stocks will seriously affect the assessments of fisheries and stocks of wild salmon.

Biological interactions of natural and enhanced stocks of salmon in Alaska

A workshop on ‘Biological interactions of natural and enhanced stocks of salmon in Alaska’, was held in autumn 1991 at the Prince William Sound Science Center in Cordova, AL, USA. The subject and site were relevant as the impacts of hatchery operations on wild salmon stocks have recently become an international concern and Prince William Sound contains one of the largest salmon hatchery operations in the world. This workshop was designed to review the evidence, or lack thereof, that hatchery salmon are affecting the growth, survival, and natural genetic diversity of wild salmon in Alaska. International, national, and regional perspectives identified the important biological interactions between hatchery and wild salmon stocks, and characterized them in terms of genetics, carrying capacity, and harvest management. The workshop participants unanimously agreed on the importance of ‘maintaining genetic diversity within and between natural populations of salmon to sustain productivity of both wild and enhanced stocks’. An expansion of stock assessment and identification research and monitoring programs using new technologies (acoustics, optics, electronic mapping, marking, and gene sequencing) is the key to the acquisition of information needed to protect wild stocks from future over-exploitation.

The status of wild and hatchery propagated Swedish salmon stocks after 40 years of hatchery releases in the Baltic rivers

The Baltic stocks of Atlantic salmon have been subjected to human exploitation for many centuries. During the last century, however, these salmon populations have been subjected to especially dramatic changes in spawning stream access, fishing patterns, and fishing pressure. At the end of the nineteenth century, salmon spawned in 60–70 rivers in the Baltic proper. From 1940 onwards many of the large salmon rivers were dammed, most of them below the lowest spawning rapids for salmon. Methods for rearing salmon up to the smolt stage were developed, and the first smolt releases started around 1950. The number of smolts released in Swedish rivers gradually increased to about 2–2.5 million by the middle of the 1980s. During the last 10 years other countries have started salmon release programs, resulting in an annual release of about 3 million smolts. Smolt releases have been successful, showing high survival rates of stocked fish. Today, only about 20 suitable rivers, most of them in Sweden, are available for natural spawning runs. The runs are very weak.Before the Second World War the Baltic salmon fishery mainly consisted of coastal and river catches of spawning migrators ascending the rivers. However, since the end of the war an offshore drift gillnet fishery has been developed, and nowadays makes up the major part of the total catch. As a consequence, the spawning runs of wild salmon have decreased dramatically. One hundred years ago the natural production of salmon from the Baltic salmon rivers was around 7–8 million smolts annually. In the early 1970s, the wild smolt run to the Baltic included about 2 million fish. At present, only about 0.5 million wild smolts are recruited to the whole Baltic proper, which is only about 20% of the smolt production capacity still remaining in the rivers.The offshore fishery on mixed populations in the central areas of the Baltic proper leads to an extremely high fishing pressure on the Baltic salmon stocks. Wild stocks are unable to cope with the present exploitation rate. As a result, the number of wild spawners in natural streams has gradually been diminishing. In the absence of a compensatory program, a reduction in stock-size of the magnitude shown by wild salmon in the Baltic would decrease catch-per-unit-effort to such a degree that there would be no economic incentive for a commercial salmon fishery. At present, however, about 90% of the salmon smolts leaving Baltic rivers are of hatchery origin. Owing to their extremely high egg-to-smolt survival rates the reared stocks can withstand this high exploitation. Thus the success of hatchery enhancement programs in combination with a lack of effective regulations, allowing a high-catch-per unit effort in the offshore fishery, is largely responsible for the sad fate of remaining wild salmon stocks in the Baltic.Any biologically sound management program for the Baltic salmon would have to include regulations prohibiting or severely restricting the offshore fishery on mixed stocks. Salmon stocks should be exploited in relation to the capacity of individual populations, by a more terminal fishery at the coast or in rivers. However, an established offshore fishery in the main Baltic, including (at least) seven nations, has so far made any kind of regulation difficult.

One-generation effects of farmed fish immigration on the genetic differentiation of wild Atlantic salmon in Norway

One-generation effects of various amounts of farmed fish immigration on the genetic differentiation among wild salmon stocks in Norway were examined. Known allel frequencies at three electrophoretic loci and population sizes of five Norwegian salmon stocks and one farmed fish strain were input in formulae for gene flow, and the results measured as reduction in G-st at electrophoretic loci.In general, a raised immigration rate from a common source will reduce the existing genetic differentiation between stocks. In absolute terms, the reduction in wild stock G-st will be largest in the first generation, because the genetic differences between immigrant and recipient are largest then. Both the magnitude and pattern of immigration effects are substantilly influenced by whether immigrant number is equal in all rivers (model I) or proportional to local population size (model II). Assuming equal fitness of immigrants and recipients, the currently reported farmed fish proportion among spawners of about 30% (the mean value in 50 Norwegian reivers as reported for 1989) was estimated to reduce existing genetic differentiation (measured as G-st) between the wild stocks involved by almost 70% in one generation under model I, and by more than 50% under model II. Each of the wild stocks will take on the genetic characteristics of farmed fish at corresponding rates. First-generation effects on G-st of burst immigrations in connection with rearing pen wrecks may be used to estimate farmed fish fitness in nature.

Attempts to reduce the impact of reared Atlantic salmon on wild in Norway

Measures to reduce the impact of reared Atlantic salmon on wild are discussed according to the current knowledge. The most important elements are rational location of fish farms, technical improvements at the farms, effective routines for catching escaped fish in the sea and in the rivers, strengthening of the wild salmon stocks by stock enhancement and strict regulations for salmon fishing. A gene bank for salmon stocks has been established to safeguard the genes of local wild salmon stocks for the future.

The potential interactions between salmon aquaculture and the wild stocks — a review

This paper reviews the literature concerning the possible interactions between salmon aquaculture and the wild salmon stocks. These include possible genetic interactions, interactions resulting from the introduction and transfer of diseases and parasites and non-indigenous fish species, economic interactions and the potential impact of aquaculture on the aquatic environment.

Wild Chinook Salmon Management: An International Conservation Challenge

The complexity of managing wild chinook salmon (Oncorhynchus tshawytscha) stocks arises primarily from marine migrations across political boundaries, the currently seriously overfished condition of stocks along the North American Pacific Coast, and detrimental impacts from activities of competing users of the freshwater habitat. Despite the fact that data and analytical capabilities are adequate, many chinook salmon stocks continue to decline. This is happening bemuse consistent management standards are lacking or not applied by decision-making bodies in favor of various unquantified socio-political alternatives. Yielding to socio-political pressures occurs even at the biological staff level, resulting in compromised biological recommendations that further undermine the fundamental management goal of long-term stock health and viability. We describe three chinook salmon case histories as paradigms of the problem: (1) the Georgia Strait stock where managers have failed to apply management standards aimed at increasing spawning escapements; (2) the Klamath River stock where managers have applied situational management standards which continuously compromise or ignore spawning escapement objectives; and (3) the upper Columbia River bright stock where conditional standards are being applied by numerous regulatory entities placing spawning escapement needs at a lower priority than other considerations.

A Wild Salmon, Trout, and Char Watch: An International Strategy for Salmonid Conservation

This paper elaborates an international strategy to register and monitor stocks of wild salmon, trout, and char through the Holarctic region. The urgent need for such a watch has been emphasized by the increasingly international nature of environmental pollution and stress (e.g. acid precipitation), and the fact that several local 'watch-like' schemes have recently arisen independently in different countries. The main objective of a watch is to foster the conservation of distinct species and stocks of wild salmonids and their habitats by an international program of monitoring and information exchange. At intervals a global wild salmonid status report would be produced for public release. The watch would be developed through an international network of interested parties and organized by a steering committee, probably set up within an existing international organization.Key words: wild salmon, trout, char, watch, worldwide strategy, stock conservation