Academic literature on the topic 'Pacific salmon fisheries Fish populations Climatic changes'

<em>Abstract.</em>—The most abundant salmon of the Yukon River is chum salmon <em>Oncorhynchus keta, </em>which make annual spawning runs from the Bering Sea up the Yukon River, traversing more than 1300 river miles across Alaska into Yukon Territory in Canada. Genetically distinct summer and fall runs exist and these runs are differentiated into stocks by timing of migration and by spawning river. The fall-run stocks are harvested from mid-July through early October and most Yukon River fisheries occur on a mixture of populations or stocks. This paper provides descriptions of fall chum salmon life history, the Yukon River fishery and its management, changes in stock abundance over time, and harvest. Six fisheries occur for fall-run chum salmon: subsistence, personal use, aboriginal, domestic, sport, and commercial. Subsistence fisheries in Alaska are comparable to aboriginal fisheries in Canada, as are personal use, sport, and domestic fisheries. The fisheries use a variety of gear including gillnets and fish wheels. Jurisdictionally, management requires cooperation among state, federal, and international organizations during both the ocean and river phases of the salmon life history. The goal of management is to regulate the harvest of commercial and traditional-use fisheries to provide an adequate number of fish for spawning (escapement) to ensure the reproduction of the next generation, and to sustain Alaskan and Canadian fisheries. Subsistence and aboriginal fisheries have priority over other fisheries in allocation of harvest. Regulations are used to control how many fish are caught through restrictions on effort, fishing efficiency, and the scheduling of where, when, and how long fishery openings will be allowed. Over the period 1974–2008, the largest runs of fall chum salmon occurred in 1975, 1995, and 2005 (> 1.47 million fish) and smallest runs occurred in 1999, 2000, and 2001 < 334,000 fish). Odd-year runs tend to be larger than even-year runs. The run failures of 1998–2002 were followed by increased run numbers in 2003–2008. Primary variables that influence the total run of fall chum salmon are the spawning success of previous generations, natural variability in marine and freshwater survival due to climatic and oceanographic processes, and fishery harvests in both marine and freshwater. Salmon escapement numbers typically emulated total run estimates. Every river monitored had low estimated escapements from 1998–2002. From 1974–2008, total harvest of fall chum salmon in Alaska (average 291,982 fish) exceeded Canadian harvests (average 20,314 fish) by an order of magnitude. Some lessons learned from management of this fishery are offered that may be applicable to other fisheries: stakeholder involvement is critical to effective harvest management; rapid, effective information sharing is a requirement for fast-paced, in-season decision-making; limited entry alone did not control harvest; and some things that make management difficult just cannot be changed!

<em>Abstract</em>.-Pacific salmon <em>Oncorhynchus </em>spp. play a central role in coastal ecosystems that rim the North Pacific Ocean. Given the ecological, cultural, and economic importance of Pacific salmon, there is great interest in defining the magnitude and frequency of change in these fish stocks. Fisheries scientists, through analyzing harvest records, have demonstrated pronounced salmon production variability. The causes underlying such marked fluctuations are currently debated. Collating harvest records across a broad geographic range over the past ~80 years, fisheries scientists have advanced a plausible argument that climate-induced oceanographic changes explain a significant fraction of the variation in salmon catch records. However, without data that predate the introduction of large-scale human interventions (e.g., commercial harvesting, dams, hatchery releases), it is difficult to isolate the role of climate in shaping fish stock dynamics. Within the past decade, however, we have developed a paleolimnological approach for tracking past sockeye salmon <em>Oncorhynchus nerka </em>population abundances, and numerous papers have applied this approach to infer changes in these fish over the past hundreds to thousands of years. Here, we provide an overview of the approach and a synthesis of the work that has been conducted in this field to date. It is clear that numerous sockeye salmon populations have undergone pronounced changes, even prior to human interventions. Furthermore, tracking salmon populations over millennial timescales with paleolimnology has revealed modes of change that were previously never imagined possible. Such long-term perspectives indicate that sockeye salmon is a resilient fish species. We note, however, that when natural environmental changes are compounded by intense human impacts, populations have been particularly susceptible to extirpation.

<em>Abstract.</em>—The Mackenzie River is the second longest river in North America and drains 1.8 × 10<sup>6</sup> km<sup>2</sup>. of Arctic and sub-Arctic Canada. Thirty-eight fish species have been recorded in the lower Mackenzie River. These species represent a unique mixture of fishes from the Beringian and Agassisian refugia. Many of the species important for subsistence and commercial fisheries in the lower Mackenzie River have complex life cycles and undertake long migrations to spawn, rear, and overwinter. The lower Mackenzie River is a relatively pristine environment with no dams or major industry, a low human population, and species only lightly harvested. This explains why the species composition is relatively stable. However, recently, the effects of climate change may be starting to influence the species composition in terms of greater frequency of rare species such as Pacific salmon. Moreover, a major gas pipeline proposed for the lower Mackenzie River region will probably disturb the fish assemblage structure.

<em>Abstract.</em>—The Mackenzie River is the second longest river in North America and drains 1.8 × 10<sup>6</sup> km<sup>2</sup>. of Arctic and sub-Arctic Canada. Thirty-eight fish species have been recorded in the lower Mackenzie River. These species represent a unique mixture of fishes from the Beringian and Agassisian refugia. Many of the species important for subsistence and commercial fisheries in the lower Mackenzie River have complex life cycles and undertake long migrations to spawn, rear, and overwinter. The lower Mackenzie River is a relatively pristine environment with no dams or major industry, a low human population, and species only lightly harvested. This explains why the species composition is relatively stable. However, recently, the effects of climate change may be starting to influence the species composition in terms of greater frequency of rare species such as Pacific salmon. Moreover, a major gas pipeline proposed for the lower Mackenzie River region will probably disturb the fish assemblage structure.

<em>Abstract.</em>—This paper reviews the history of the subsistence, commercial, and sport fisheries, describes variation in salmon runs and harvest over time, and summarizes past management of salmon in the Norton Sound and Port Clarence Management Districts. The drainages of Norton Sound support important subsistence and commercial fisheries for salmon. Sport fisheries are small in comparison. Archeological evidence dating back 2,000 years indicates fishing has been an important part of life for Norton Sound residents for centuries. Since statehood in 1959, salmon abundance and harvest peaked in the late 1970s and early 1980s. The 1998 and 1999 salmon runs were some of the poorest on record. Since 2003, large increases in spawning escapement have been recorded for chum <em>Oncorhynchus keta</em>, pink <em>O. gorbuscha</em>, coho <em>O. kisutch</em>, and sockeye <em>O. nerka </em>salmon stocks. Chinook <em>O. tshawytscha </em>salmon runs have declined since the late 1990s and not rebounded. Salmon management seeks to allow sufficient escapement to spawning rivers to ensure long-term sustainable yields. Salmon fisheries are managed under three different sets of regulations: subsistence, commercial, and sport. Subsistence harvests are given a priority over commercial and sport harvests. In 1999, due to low salmon returns to spawning streams, the U.S. government declared the Norton Sound region a federal fisheries disaster and the state of Alaska began managing the subsistence fishing in the Nome Subdistrict as a limited entry fishery (Tier II permit). Restoration of salmon is dependent on a wide set of variables including suitable juvenile rearing habitat, favorable ocean conditions for growth and survival, and adequate numbers of returning adults for spawning and producing the next generation of salmon. Regulation of harvest is critical to salmon restoration so that adequate spawning escapements occur and that this critical link within the life cycle of salmon remains unbroken. More restrictive harvest regulations than in the past has allowed more salmon to reach the spawning grounds and helped to restore salmon populations and their fisheries. These harvest restrictions affected not only the fish but also those who fished, and caused changes in fishing patterns in time and space and potentially changed cultural values towards some species.

<em>Abstract.</em>—The effects of changing climate on salmon populations depend on the species and life history of interest, local expressions of climate change, characteristics of habitat, and the adaptation of specific populations to geographic variation in habitat characteristics. Here we review some of the key changes in climatic conditions that have affected freshwater ecosystems used by Pacific salmon in the recent past and summarize how these will be further impacted by future changes in temperature and precipitation patterns. Recent climate change has affected some well-studied populations allowing for some generalization about climate impacts on specific populations. One recurrent response to warming in freshwaters is a positive growth response in juveniles and an acceleration of the freshwater component of life histories, although these responses are unlikely to occur at the southern range boundaries for salmon. In addition to substantial latitudinal variation in recent and expected climate impacts on salmon ecosystems, there is increasing evidence of regional variation among population responses to the same overriding regional changes in climate. Biocomplexity, defined as the variation in habitat characteristics and its associated suite of locally adapted populations, provides a portfolio effect to salmon stocks. A portfolio effect results from weakly correlated dynamics in the component populations of a salmon stock. A stock characterized by a high diversity of populations and their associated dynamics, is less sensitive to the variation in an individual population, compared to a stock with low diversity. This portfolio effect provides resilience to salmon fisheries in the face of ongoing climate change because fisheries integrate across the component diversity within stocks. While many of the future characteristics of freshwater habitats remain highly uncertain in the face of ongoing climate change, protection of diverse networks of viable habitat and the stock diversity that maps onto this landscape diversity, is one obvious strategy to ameliorate the effects of future climate change on salmon stocks.

<em>Abstract.</em>—This paper presents a synopsis of discussions by commercial and subsistence fishers, biologists, fishery managers, and academicians about salmon management held at the symposium (this volume). The group reviewed current strategies and discussed changes that may be made to improve management with respect to fish numbers, stakeholder needs, and engagement of local people. The conservation of salmon <em>Oncorhynchus </em>spp. was a shared value among all participants along with the belief that sustainable salmon yields will ensure sustainable rural communities within the Arctic-Yukon-Kuskokwim (AYK) region. Management by escapement goals was a useful management strategy; however, substantial concerns were expressed that high risks to salmon populations and fisheries existed when goals were based on maximum sustained yield concepts. Weekly in-season teleconferences among fishery participants and managers have provided important information, improved decision making, and built relationships and trust between managers and fishers. Traditional ecological knowledge was viewed as an important source of information and could be further incorporated into management decisions. Studies should be conducted to understand the nature of selective fishing on salmon (e.g., size, life history, sex), and its effects on the long-term sustainability of salmon populations. Allocation of subsistence harvest in times of salmon scarcity should recognize and prioritize human food as the highest use, then dog food, and last customary trade uses. Opportunities should be explored to increase interaction between freshwater and ocean managers to achieve a more holistic, ecosystem-based management of salmon stocks over their entire life history. Tensions exist within the fisheries including: commercial versus recreational versus subsistence fishers; downstream versus upstream fishers; and state versus federal management of subsistence fisheries. These tensions will continue to pose a challenge to management. With improved information, communication, and cooperation, successful management of AYK salmon is possible and will help ensure sustainability and opportunity for use by future human generations.

<em>Abstract.</em>—Salmon hatcheries in the Pacific Northwest continue to produce fish for harvest, largely to fulfill a mitigation function. Fisheries management struggles with the need to integrate this harvest opportunity from hatcheries with wild fish conservation. Warm Springs National Fish Hatchery demonstrates a program that balances this need to help offset salmon losses, provide fisheries, and protect wild fish. The U.S. Fish and Wildlife Service and Confederated Tribes of the Warm Springs Reservation of Oregon initiated the hatchery program in 1978 with wild, native fish from the Warm Springs River. The goal is to cooperatively manage hatchery operations to balance harvest opportunities with protection of wild fish populations and their inherent genetic resources. The management objectives are (1) to produce spring Chinook salmon <em>Oncorhynchus tshawytscha </em>for harvest in tribal subsistence and sport fisheries, (2) to preserve the genetic characteristics of the native population both in the hatchery and in the naturally spawning component of the integrated population, (3) to manage impact on wild fish to levels which pose a minimum risk, and (4) to develop and implement a hatchery operations plan to achieve both the harvest and conservation goals for the Warm Springs River Chinook population. To determine if these objectives are met, data on harvest, escapement, recruitment, spawning success, fish health, survival, run timing, age and size at return, and juvenile production characteristics have been collected to monitor changes over time and to compare performance of wild and hatchery origin fish. These data have been cooperatively collected by the Confederated Tribes of the Warm Springs Reservation, Oregon Department of Fish and Wildlife, and U.S. Fish and Wildlife Service for more than 25 years. Every 5 years, a hatchery operation plan has been developed based on this monitoring. The following list of actions are identified in the 2002–2006 hatchery operations plan and are measures for protecting the natural population while operating the hatchery for harvest augmentation: (1) Mass marking and codedwire tagging of hatchery production for selective fisheries, broodstock management, and hatchery evaluations; (2) Selecting broodstock to mimic wild fish run timing; (3) Incorporating wild fish in the hatchery broodstock using a sliding scale; (4) Limiting the number of hatchery fish allowed to spawn naturally; (5) Operating an automated passage system for returning adults to reduce handling of wild fish; (6) Replacing the hatchery’s water intake structure to meet new screening criteria to protect juvenile fish; (7) Simulating environmental and biological factors in the hatchery environment to match natural production; (8) Managing fish health at the hatchery; (9) Assessing ecological interactions between wild and hatchery fish; and (10) Determining the reproductive success of hatchery fish spawning in the stream. The monitoring and management of Warm Springs National Fish Hatchery demonstrates a sustainable program, integrating the need for both harvest and wild fish conservation.

<i>Abstract</i>.—Success achieving fishery management goals is possible but often requires concurrent strategies addressing ecology, politics, and public communication combined with some level of good fortune. As an introduction to this book, we identify several themes consistently highlighted among the fish management stories that follow, regardless of species, their life history, habitat needs, or type of waters they live in—streams, lakes, or ocean. In almost every case, success of management relied first and foremost on the abilities of professionals to restore the quality and quantity of a fish’s habitat. The success of these efforts varied in magnitude but was accomplished by a combination of effective environmental regulation, substantial public and private investment, and direct habitat manipulation—whether in Lake Erie (Canada and USA), the Vindeln River in northern Sweden, an Adirondack Mountain lake of New York (USA), or Sea Lamprey <i>Petromyzon marinus</i> along the Atlantic coast (USA). Fish need acceptable water quality and habitat for living: simply stated and obvious—fish need water! When water and fish habitat are restored, fish populations can naturally recover through colonization from remnant populations, as was experienced in the Scioto River, Ohio. In some cases, populations were restored by stocking fish, using careful genetic considerations, such as told for Snake River Sockeye Salmon <i>Oncorhynchus nerka</i>. Public engagement was a common theme among case studies presented in this text. Public support for management yielded the political will to provide funding, regulation, and enforcement. Public involvement was a critical component of stories told about Great Smoky Mountains Brook Trout <i>Salvelinus fontinalis</i>, Pacific salmon in British Columbia and Idaho, and Tonle Sap fisheries of Cambodia. Consistently, management success came when goals were clearly articulated and combined with an effective consensus-built management plan that had the long-term commitment of personnel and support of their agencies. These attributes yielded programs where actions were taken and long-term monitoring and assessment were implemented to gauge success. Assessment information allowed programs to be adaptive over time to changes in the ecological system and society and thereby helped address new, as well as ongoing, challenges the fish and fishery were experiencing. The stories in this text provide incontrovertible evidence that good things can happen with the development and implementation of effective fish management programs, demonstrating the value of our profession and providing clear evidence that success is not an impossible allusion but rather an achievable event. These success stories of restored fish and fisheries throughout the world should be celebrated within fishery science.