2
Salmon Life History and Background

LIFE HISTORIES OF SALMON SPECIES IN THE AYK REGION

The following sections describe the life histories of the five species of Pacific salmon (Oncorhynchus spp.) found in the Arctic-Yukon-Kuskokwim (AYK) region. These sections focus on habitat use over the course of their life histories; more detailed information on reproduction, foraging, predation, and other aspects of salmon life history is provided in other sections of this report. The concluding section presents some information on recent variations in run sizes, catches, and revenue from commercial fishing in the AYK region.

Testimony presented by village elders and others during the 2003-2004 National Research Council (NRC) site visits showed that there is a substantial body of traditional knowledge about salmon life history in the AYK region that has yet to be integrated with information from the published scientific literature. Much of the information in this chapter is summarized from more detailed reviews by Burgner (1991) (O. nerka, sockeye or red salmon), Healey (1991) (O. tshawytscha, Chinook or king salmon), Heard (1991) (O. gorbuscha, pink or humpback salmon), Salo (1991) (O. keta, chum or dog salmon), and Sandercock (1991) (O. kisutch, coho or silver salmon).

The Norton Sound Scientific Technical Committee (NSSTC) reviewed life history information specific to AYK salmon (Mundy et al. 2002). Brodeur et al. (2003) reviewed U.S. research on the ocean life history of juvenile salmon—that is, salmon in their first year at sea



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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon 2 Salmon Life History and Background LIFE HISTORIES OF SALMON SPECIES IN THE AYK REGION The following sections describe the life histories of the five species of Pacific salmon (Oncorhynchus spp.) found in the Arctic-Yukon-Kuskokwim (AYK) region. These sections focus on habitat use over the course of their life histories; more detailed information on reproduction, foraging, predation, and other aspects of salmon life history is provided in other sections of this report. The concluding section presents some information on recent variations in run sizes, catches, and revenue from commercial fishing in the AYK region. Testimony presented by village elders and others during the 2003-2004 National Research Council (NRC) site visits showed that there is a substantial body of traditional knowledge about salmon life history in the AYK region that has yet to be integrated with information from the published scientific literature. Much of the information in this chapter is summarized from more detailed reviews by Burgner (1991) (O. nerka, sockeye or red salmon), Healey (1991) (O. tshawytscha, Chinook or king salmon), Heard (1991) (O. gorbuscha, pink or humpback salmon), Salo (1991) (O. keta, chum or dog salmon), and Sandercock (1991) (O. kisutch, coho or silver salmon). The Norton Sound Scientific Technical Committee (NSSTC) reviewed life history information specific to AYK salmon (Mundy et al. 2002). Brodeur et al. (2003) reviewed U.S. research on the ocean life history of juvenile salmon—that is, salmon in their first year at sea

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon (ocean age .0, before January 1 of their second year at sea).1 Information on the ocean life history of immature and maturing AYK salmon is based largely on extensive high-seas research gill net, purse seine, longline, and trawl surveys; tagging experiments; and stock identification studies conducted as part of the research programs of the International North Pacific Fisheries Commission (INPFC) from 1953 to 1992 and the North Pacific Anadromous Fish Commission (NPAFC) from 1993 to present. Detailed research methods and results are presented in the annual report, bulletin, statistical yearbook, and technical report series of INPFC and NPAFC (also see reviews by Burgner 1992, Myers et al. 2000). Broad syntheses of the INPFC/NPAFC data were used to develop conceptual models of the movements of immature and maturing salmon on the high seas (coho salmon, Godfrey et al. 1975; sockeye salmon, French et al. 1976; chum salmon, Neave et al. 1976; Chinook salmon, Major et al. 1978; pink salmon, Takagi et al. 1981), although these models need to be updated with new information. Additional sources of information are cited throughout the text. General Life History Characteristics The life histories of all five species of Pacific salmon found in the AYK region share several general characteristics. All species are anadromous: spawning occurs in the fall, usually in freshwater, and juveniles then migrate to the marine environment. In the ocean, salmon grow to maturity, and mature adults return to freshwater to spawn. Individuals in all species typically home rather precisely to their natal area to spawn. All species are semelparous, spawning only once and dying a few days or weeks later. Within this general framework, many other life history characteristics are common to all species. Mature females bury their relatively 1   Age and life history are designated by the European method. For example, an age 1.3 Chinook salmon spent one winter in freshwater (F) and three winters in the ocean (W). The number before the dot designates the number of winter annuli laid down on the fish’s scales while in freshwater, and the number after the dot designates the number of winter annuli formed in the ocean. The Alaska Department of Fish and Game may designate the age of an adult salmon by its total age (T) at return, where T = F + W + 1 (for example, a 1.3 Chinook is 5 years old). This calculation accounts for the fact that scales do not form until after the fish hatch, so the first winter of life spent as a developing egg and alevin in the stream gravels is not recorded on the scales.

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon large (5-10 mm) eggs in stream gravels, and, in the case of beach spawning sockeye, along lake shores. Average fecundities range from 1,200 for pink salmon to 17,000 for Chinook salmon. Typically, a female selects a redd site and digs a depression in the gravel, where she deposits her eggs in a series of pockets, and covers each pocket in turn. Males fight among themselves for proximity to a female to increase their chances of fertilizing her eggs, and small males may fertilize eggs by sneaking into the nest depression at the time the female releases her eggs. After spawning, a female typically spends her last few days of life defending her nest site against late-arriving females. The female protects her eggs from predators and environmental extremes by burying them in the gravel. She also selects a habitat that will provide her offspring with suitable conditions for development. Principal requirements of eggs are a temperature regime that provides sufficient degree-days for development, adequate dissolved oxygen for respiration and growth, and adequate through-gravel flow to supply oxygen and remove waste products. The temperature regime in the spawning gravels is closely related to the time at which salmon spawn. Spawning occurs earlier in areas where the water in the gravel cools to near freezing early in the winter, and it occurs later in areas where upwelling groundwater maintains relatively high intragravel temperatures during winter. In the AYK region, salmon eggs typically hatch in early to midwinter and alevins remain in the gravel until they emerge in spring. During this time, they live on the energy reserves in their yolk sac and can be quite mobile, often burying more deeply into the gravel, presumably to avoid being disturbed by floods. Salmon fry emerge from the gravel in spring, typically at night, and at this point their life histories diverge. Most pink and chum salmon begin their migration to the ocean within a few days of emergence when they are still small fish (approximately 1 g, 25-35 mm) and concurrently undergo the physiological, morphological, and behavioral changes associated with smolting. These changes prepare them for their downstream migration and for entering the marine environment. The other three species—sockeye, coho, and Chinook salmon—will spend 1 or 2 years rearing in freshwater and reach a larger size (8-20 g, 70-150 mm) before smolting. The smolt migration of all species typically occurs soon after spring breakup, a time associated with increasing water temperatures and flows, and the fish arrive in the marine environment in early summer. At ocean entrance, juvenile salmon often first aggregate in intertidal (littoral) waters; then, as they grow, they gradually move offshore to neritic habitats (shallow, pelagic areas near shore or over the continental

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon shelf, from low-tide mark down to a depth of about 200 m). Tagging experiments have revealed that the direction of movement and migratory routes of juvenile salmon in coastal waters are inherited or specific to regional stock groups. Initial coastal movements of AYK juvenile salmon may be in the direction of prevailing ocean currents. AYK juvenile salmon spend most or all of their first summer and fall at sea in waters over the continental shelf in the Bering Sea, Aleutian Islands, and Arctic Ocean. Distributions of Bering Sea and Gulf of Alaska salmon stocks at the juvenile stage do not overlap for any salmon species. Gradual offshore movements of juvenile AYK salmon continue throughout their first summer and fall in neritic waters over the Bering Sea shelf, where they are distributed in surface or near-surface waters (to a depth of 20-30 m). Salmon (surface trawl) surveys in the eastern Bering Sea in July-September by the National Marine Fisheries Service (NMFS), Auke Bay Laboratory, Ocean Carrying Capacity (OCC) indicate substantial annual, seasonal, and spatial variation in distribution by species and stock (Farley et al. 1999; 2000a,b; 2001). These surveys also suggest that oceanic conditions, especially as indicated by coccolithophore blooms, influence the distribution and migration routes of juvenile salmon. Studies in other regions indicate that vertical distribution of juvenile salmon in neritic habitats is influenced by biotic (species, age, size, and forage location) and abiotic (water temperature, salinity, season, light, turbidity, currents, tides, and bottom topography) factors. Seasonal use of neritic habitats by juvenile salmon in other regions has also been linked to many factors, such as species-, stock-, and size-specific preferences for water temperature and distribution and availability of their preferred prey. After their first summer at sea, salmon from the AYK region of western Alaska range widely throughout the Bering Sea and Aleutian Islands, the central and eastern North Pacific Ocean, and the Gulf of Alaska during extensive ocean feeding migrations. Historical International North Pacific Fisheries Commission/North Pacific Anadromous Fish Commission (INPFC/NPAFC) data are inadequate to infer migration patterns between juvenile and immature age 0.1 life history stages of AYK salmon. The extent of their offshore movements in the Bering Sea and North Pacific Ocean in late fall and winter is unknown. In general, western Alaskan stocks migrate farther offshore in winter than stocks from more southerly regions of North America. Based on the distribution of age 0.1 salmon the following spring, many or most AYK juvenile sockeye, chum, pink, and coho salmon move south through the Aleutian passes into the central and eastern North Pacific Ocean in late fall or

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon winter. Winter trawl surveys have revealed that all species of salmon in their first winter at sea can be caught far offshore in the North Pacific Ocean by January and February, although the stock composition of these catches is not known. The area where juvenile AYK salmon are distributed at the end of their first winter at sea may vary from year to year depending on species, stock, age, growth, and environmental conditions and could be the approximate high-seas location where they begin their adult return migrations to natal streams. Data from INPFC/NPAFC tagging experiments show that the ocean distributions of AYK salmon and of salmon from other regions of North American (central and southeast Alaska, British Columbia, and the U.S. West Coast) overlap primarily in the Gulf of Alaska (defined as northeast of 50°N 170°W), the northeastern North Pacific Ocean (defined as southeast of 50°N 170°W), and the southeastern Bering Sea (Myers et al. 1996). The offshore distribution and migration patterns of AYK salmon are more similar to Asian (Russian and Japanese) salmon than to other regional stocks of North American salmon. The distributions of Asian and AYK salmon are known to overlap eastward from about 170°E, across most of the Bering Sea and Aleutian Islands, North Pacific Ocean, and western and central Gulf of Alaska. The extent of overlap in the distributions of AYK and Asian salmon in the Russian exclusive economic zone (EEZ) in the Arctic Ocean, western Bering Sea, and western North Pacific Ocean is not known. Knudsen (2003) and NSSTC (Mundy et al. 2002) reviewed information on the marine life history of adult salmon returning to the AYK region (sex ratios, ages, sizes, travel and stray rates, milling time in the vicinity of river mouths, and upstream migration timing). Upstream migrations of AYK salmon generally occur between the first of June and the end of October. Interspecific patterns of upstream migrations are similar across the AYK region, with Chinook salmon entering rivers first, followed by summer chum and pink salmon, and with fall chum and coho salmon entering last. Knudsen (2003) concluded that very little is known about the marine life history of AYK salmon at this time. Species-Specific Life History Characteristics Within this broad framework, each species of salmon has unique life history characteristics that set it apart from the others. Some of these characteristics include the number of years spent in the freshwater and marine environments and the use fish make of freshwater and marine

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon habitats. Adults of the five species in the AYK region are often smaller than their counterparts farther south. Pink Salmon Pink salmon are distinguished by their obligate 2 year life cycle and brief freshwater residence. All fish have a 0.1 life history. Because of this obligate life cycle, there are even- and odd-year runs that do not interbreed. Pink salmon in the AYK region typically spawn close to the ocean, often in short coastal streams. Outmigration of juvenile pink salmon from the Yukon River peaks before mid-June, and they seem to move rapidly through delta habitats to the delta front. Recent (2002-2003) OCC surveys over the eastern Bering Sea shelf and Kotzebue Sound show that in the fall juvenile pink salmon are found in offshore habitats between 60°N and 63°N (Farley et al. 2003a,b; Murphy et al. 2003). Historical INPFC/NPAFC data on the distribution of age 0.1 fish the following spring suggest that many or most AYK pink salmon move south through the Aleutian passes into the central and eastern North Pacific Ocean in late fall or winter. Pink salmon, averaging 30 cm long, are broadly distributed across the southern Gulf of Alaska in January and February. In the North Pacific Ocean west of 180°, pink salmon are distributed south of 46°N in January-March. Early in their second summer at sea, maturing AYK pink salmon begin their homeward migration and are distributed in the northeastern North Pacific in early spring (April) and in the central North Pacific Ocean, Aleutian Islands, and Bering Sea in June and July, reaching their spawning grounds in western Alaska in middle to late summer. Pink salmon are the smallest of the five species and mature adults typically weigh 1-2.5 kg. Chum Salmon Chum salmon migrate to the ocean soon after they emerge from the gravel, but, unlike pink salmon, the length of their marine residency is variable. Life histories for AYK chum salmon stocks are predominantly 0.3 and some mature at age 4. A significant percentage mature as 0.2 and 0.4 fish at ages 3 and 5, respectively. Two distinctly different races of chum salmon exist in Alaska: summer chum and fall chum. By convention, adults returning before July 15 are termed summer chum, and those returning after July 15 are termed fall chum. Summer chum spawn

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon in late summer in clearwater runoff rivers, often in areas of upwelling flows. Fall chum spawn later, in early winter, typically in areas of groundwater upwelling on glacially influenced streams. In the Yukon River, the outmigration of juvenile chum salmon peaks in late June when millions of small fry (approximately 40 mm) are dispersed by high river discharges through numerous distributary channels into coastal habitats. Catches of rearing fry in Yukon delta habitats decrease as water temperatures increase (18-21°C) in mid-July, and fish are found in coastal and delta front habitats from June through early August. Similar movements of juvenile chum salmon have been observed in Norton and Kotzebue Sounds. Genetic (allozyme) stock-identification analysis of samples of juvenile chum salmon collected in fall 2000 and 2002 surveys in the eastern Bering Sea recently has provided more detailed information on the distribution of AKY chum early in their first summer at sea. This work shows that: (1) Kotzebue Sound chum salmon are distributed as far south as the Yukon River, suggesting a southerly migratory pathway; (2) Yukon River fall chums are widely distributed from off the mouth of the Yukon River, eastward to 62°N 172°W, and as far south as Nunivak Island (60°N), suggesting a southwesterly migration pathway along the Bering Sea shelf; (3) Kuskokwim fish are narrowly distributed south of Nunivak Island from the mouth of the Kuskokwim River, south to 58°N and as far west as 168°W, suggesting a westerly migration pathway along the Bering Sea shelf; and (4) northern Russia stocks (mainly Gulf of Anadyr watersheds) are distributed as far east as 62°N 171°W (Farley et al. 2003a,b; Murphy et al. 2003). Recent (2002-2003) OCC surveys in neritic habitats over the eastern Bering Sea shelf and Kotzebue Sound show that juvenile AYK chum salmon are generally north of 58°N in the fall. Based on the distribution of age 0.1 fish the following spring, many or most of these individuals are thought to move south through the Aleutian passes into the central and eastern North Pacific Ocean in late fall and winter. In subsequent years of ocean life, immature AYK chum salmon are distributed in the northeastern Pacific Ocean in fall (November), in the Gulf of Alaska in fall (November), spring (May), and summer (May-August), in the Aleutian Islands in late spring and summer (June-August), and in the Bering Sea in summer (July). Maturing AYK chum salmon are distributed in the central and eastern North Pacific Ocean in spring (April-May), in the Gulf of Alaska in spring and summer (April-August), in the Aleutian Islands in spring and summer (May-July), and in the Bering Sea in summer (June-August). Summer chum salmon reach their spawning areas by middle to late summer, and fall run fish reach

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon their spawning grounds in fall and early winter. Adult chum salmon in the AYK region typically weigh 2.5-4.5 kg. Sockeye Salmon Sockeye salmon are distinguished from the other species of Pacific salmon in that they spend a significant amount of time rearing in freshwater lakes. As a result, large sockeye runs are restricted to systems with suitable lakes. In Alaska, sockeye are particularly abundant in the lake systems of Bristol Bay, although smaller but significant stocks do exist in the drainages farther north. Life histories in the Kuskokwim River are predominantly 1.3, 2.3, and 1.2. Sockeye spawn in lake inlet and lake outlet streams and, in some systems, along lake shores. Fry migrate into the lake after emergence and spend one or two summers rearing there before smolting. Recent (2002-2003) OCC surveys over the eastern Bering Sea shelf and Kotzebue Sound show that by fall, juvenile sockeye salmon, primarily Bristol Bay stocks, are broadly distributed across the eastern Bering Sea shelf south of 59°N (Farley et al. 2003c). Based on the distribution of age 0.1 salmon the following spring, many or most AYK juvenile sockeye then move south through the Aleutian passes into the central and eastern North Pacific Ocean in late fall or winter. By January and early February relatively few juvenile sockeye salmon remain in the Bering Sea, and they are broadly distributed across the central and eastern North Pacific Ocean. Their winter high-seas distribution in the North Pacific extends southward to about 46°N in the central North Pacific and 48-51°N south of the Alaska Peninsula. Their migrations are extensive, covering an estimated distance of 1,300-1,850 km at a travel rate of at least 14.8-18.5 km per day. Subsequent movements see immature western Alaska sockeye salmon (mostly Bristol Bay, ocean age 0.1 and 0.2) widely distributed in North Pacific waters south of 50°N from the Gulf of Alaska to about 175°E during midwinter. In early spring they may move farther south to feed on the first plankton blooms, and by midspring they move northward over a broad east to west front between about 175°E and 155°W. By June they are distributed in the boundary region between westward and eastward flowing currents (sometimes called the ridge domain) and in the narrow (less than 30 km wide), high-velocity (more than 50 cm/s), and westward flowing Alaska current, immediately south of the Aleutian

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon Islands, where they may remain through the summer. Summer migrations of immature sockeye salmon in this region are initially westward, and at least some immature fish make extensive migrations to the west and northwest through the Aleutian passes and into the central and western Bering Sea. In fall and early winter, immature fish move south and are joined by a new brood of age 1 and 2 fish. Maturing fish remain throughout the winter and spring in more northerly waters of the North Pacific Ocean than immature fish. Sockeye salmon that mature after only one winter at sea (jacks) may remain throughout the fall, winter, and spring in eastern Aleutian Islands and Bering Sea waters. Sockeye reach their spawning grounds in midsummer. Adult sockeye salmon typically weigh 2-3 kg. Coho Salmon Coho salmon are distinguished from pink and chum salmon by a period of freshwater rearing and from sockeye salmon by the fact that they typically rear in streams rather than in lakes. Life histories of AYK coho salmon are typically 2.1, so fish are 4 years old when they spawn. Some male coho mature after only a few months at sea and these are known as jacks. Jacks typically have a 1.0 life history, having grown rapidly in freshwater and smolted after 1 year. Coho salmon spawn in small streams in coastal areas of the AYK region and in spring-fed streams in the interior. The timing of spawning is later than for other species, with the exception of fall chum: late summer in coastal systems and early winter in the interior. After emerging from the gravel in spring, coho salmon fry feed on drifting invertebrates in streams, moving to faster, deeper water as they grow. Coho salmon also make considerable use of off-channel habitats such as beaver ponds, side channels, and oxbows for summer feeding and also will rear in lakes when these are available. Like most salmonids that use small streams, coho spend much of the winter concealed in cover, typically under stream cobbles, and they often migrate to overwinter in off-channel habitats or small streams. Recent (2002-2003) OCC surveys over the eastern Bering Sea shelf and Kotzebue Sound found juveniles in nearshore habitats during fall, suggesting juvenile coho salmon spend a considerable part of their first summer near shore. During salmon research (purse seine) fishing operations in the eastern Bering Sea and Aleutians in July, Hartt and Dell (1986) also caught juvenile AYK coho salmon in small numbers in the

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon eastern Bering Sea in July, August, and September. Based on the distribution of age 0.1 salmon the following spring, many or most AYK juvenile coho salmon move south through the Aleutian passes into the central and eastern North Pacific Ocean in late fall and winter. In the North Pacific Ocean west of 180°, coho salmon are distributed south of 46°N in January-March and well offshore in the central Gulf of Alaska. Maturing AYK coho salmon are distributed in the northeastern Pacific Ocean in spring, while in summer they occur in the central North Pacific Ocean to the western Gulf of Alaska. Maturing coho salmon reach their spawning grounds in late summer. Adult AYK coho salmon typically weigh 2.5-3.5 kg. Chinook Salmon The life history of Chinook salmon in the AYK region resembles that of coho salmon in some ways, but they are distinguished by their longer marine residence and larger body size. With few exceptions, AYK juvenile Chinook salmon smolts are stream-type (predominantly freshwater age 1.) and differ from those found farther south, which are the ocean-type (freshwater age 0.). Most Yukon River Chinook have 1.3 or 1.4 life histories, maturing at age 5 or 6. However, age at maturity is quite variable; significant numbers of males also mature at ages 4 and 7, and significant numbers of females mature at age 7. Chinook salmon spawn in small streams in coastal areas of the AYK region and in clearwater runoff streams in the interior. Their use of small streams in coastal areas resembles coho salmon, but, unlike coho, very few Chinook spawn in spring-fed streams in the interior. Instead, they resemble chum salmon in their choice of clearwater runoff systems, where they generally spawn in the tails of large pools and in runs in areas where downwelling predominates. Upon emergence from the gravel, Chinook salmon feed on drifting invertebrates, moving to faster deeper water as they grow. Chinook fry and fingerlings may migrate upstream from spawning areas to feed in smaller streams; they also may move downstream to feed in larger glacially influenced systems, where the turbidity may provide protection against predators. Chinook are also less likely than coho to use off-channel habitats such as beaver dams. Juvenile Chinook typically are found in larger streams, concentrated in areas where there is woody debris, often along the outside of meander bends in pools. This woody debris undoubtedly provides cover from predators but also may provide

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon velocity refuges and generate systems of vortices that small fish can use to reduce the energetic cost of foraging. Upon migration to the ocean, Chinook smolts from the Yukon River do not appear to use littoral habitats in the vicinity of the delta, contrasting with ocean-type Chinook salmon in British Columbia (Healey 1991). However, recent (2002-2003) OCC juvenile salmon surveys over the eastern Bering Sea shelf and Kotzebue Sound reveal that juvenile Chinook salmon occur in nearshore marine habitats during fall, suggesting that they do not all move offshore as soon as they enter the marine environment. Traditional ecological knowledge also reveals that Norton Sound is a rearing area for Yukon River Chinook salmon juveniles in summer and fall. This finding (observation) is supported by recent tag recoveries of juvenile Yukon River Chinook salmon in Norton Sound. Salmon research on (purse seine) fishing operations in the eastern Bering Sea and Aleutians in July shows that some Chinook salmon do move offshore early in their first summer at sea (Hartt and Dell 1986). Juvenile Chinook salmon first appeared in eastern Bering Sea catches in late June, and they were also caught in all subsequent time periods. NMFS observer data indicated that in December at least some juvenile Chinook salmon are distributed in the international waters of the central Bering Sea. Data from INPFC/NPAFC tagging experiments show that immature AYK Chinook salmon are distributed in the central and eastern Bering Sea in winter and spring and in the central and western Bering Sea in summer. Maturing AYK Chinook salmon are distributed in the central and eastern Bering Sea in winter and spring. Chinook salmon are the largest of the five species, with recorded weights of up to 45 kg; in the AYK region adults typically weigh 5-10 kg. Stock-Specific Life History Differences The fact that mature salmon home rather precisely to their natal areas means that fish spawning in different parts of a drainage are reproductively isolated and local adaptations can evolve. This has farreach ing implications because these reproductively isolated groups (stocks or populations) often evolve life history characteristics that adapt them to the unique conditions they encounter in the habitats they use for spawning and rearing. As a result, considerable stock-specific variation in life history characteristics exists that fits particular stocks to their particular habitats. Summer and fall chum salmon populations in the Yukon

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon River provide an example of this kind of local adaptation. The timing of their spawning migrations and the location of their spawning areas are distinct and adapt them to spawn at a time and place that will provide the correct thermal environment for egg development. Kuskokwim Chinook provide another example. Fish destined to spawn in upstream tributaries begin their upstream migration before fish bound for tributaries farther downstream; this is likely to be an adaptation that allows upstream stocks more time to reach the spawning areas at the appropriate time for spawning. Another example of local adaptation is the large body size of some Chinook salmon stocks. This is thought to have evolved as an adaptation for spawning in fast, deep water with a large spawning substrate. Conversely, small body size and drab coloration has evolved in sockeye salmon stocks that spawn in shallow streams subject to heavy predation by bears. Similar local adaptations of other life history traits undoubtedly exist, including characteristics such as egg size, fecundity, developmental rates, foraging and predator avoidance behavior, length of freshwater and marine residence, migratory timing, migratory routes, and reproductive behavior. This diversity of local adaptation is one of the characteristics that allow salmon to make such effective use of fresh water and marine environments and undoubtedly contributes to their abundance. This variability among a large variety of stocks within each species, and among species, likely provides resilience to environmental change. Changes in the marine environment, however, are likely to cause changes in all stocks because salmon spend most of their life at sea, where most of their growth and reproductive potential is attained. This variability among stocks within species serves to complicate conservation measures, for this variability contributes unique characteristics (phenotypic and genotypic) that should be preserved into the future (e.g., Hilborn et al. 2004). Management practices that do not recognize and preserve this diversity will endanger the resilience of the system. RECENT VARIATIONS IN RUNS AND CATCHES Here we present some information on the recent declines in run sizes, catches, and revenue from commercial fishing for AYK salmon. As we discuss in later chapters, it is not clear whether the recent declines reflect long-term trends or instead shorter-term fluctuations. In either case, they have been accompanied by hardship and anxiety among the region’s residents and were a major reason for the establishment of the AYK Sustainable Salmon Initiative (SSI) and the present committee.

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon Figure 2-1 provides information on commercial catches of salmon in the Arctic-Yukon-Kuskokwim (AYK) region. The information before the 1980s cannot be used as an indicator of run sizes, because commercial catches do not depend only on run sizes. They depend also on the amount of fishing effort expended, which in turn depends on factors such as the price of salmon, the availability of salmon markets, the degree to which a community is involved in a cash economy, regulatory restrictions, and other factors. The declines in the past 15 years are at least somewhat reflective of declines in run sizes. Figures 2-2 and 2-3 present information on gross earnings from commercial fishing in the Yukon-Koyukuk and the Wade Hampton census areas. The former area includes much of the interior part of the AYK region, focusing on the Yukon River drainage. The second area includes much of the downriver area of the Yukon River, including the delta. Recent commercial-fishing incomes in the Yukon-Koyukuk Census Area have been 78% less than they were in 1995. The overall economic base of the Wade Hampton Census Area decreased 23% from 1995 to 1999. The decrease was primarily due to poor FIGURE 2-1 Historical trends in commercial catches of salmon in the Arctic-Yukon-Kuskokwim management region (1913-2004). Preliminary data for 2004 include only Chinook and sockeye salmon catches through July 9, 2004. Source: Alaska Commercial Fisheries Entry Commission 2004.

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon salmon runs beginning in 1996 and cutbacks in federal government spending. Gross earnings from commercial fishing were 24% less than what they were before the collapse of salmon runs. The low salmon returns resulted in lower catches and increased regulatory restrictions on fishing. That resulted in reduced revenue for cash-short communities along the region’s rivers. Those losses forced fishers, especially in the lower reaches of the rivers, to reduce fishing times and use less expensive and less efficient gear. Restrictions on subsistence fishing and lower catches also affected all aspects of the lives of people in the region. Especially in interior regions, where other subsistence foods were less abundant during that period and groceries are either extremely expensive or not available, people were short of food and had to rely on government subsidies. The loss of subsistence food and reliance on other food sources results in cultural changes—subsistence is a central feature of Native cultures in the region—that include the loss of traditional knowledge, language, and change in cultural priorities. Those losses are progressively harder to reverse with time. FIGURE 2-2 Gross earnings from commercial fishing in the Yukon-Koyukuk census area. Source: Alaska Commercial Fisheries Entry Commission 2004.

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Developing a Research and Restoration Plan for Arctic-Yukon-Kuskokwim (Western Alaska) Salmon FIGURE 2-3 Gross earnings from commercial fishing in the Wade Hampton census area. Source: Alaska Commercial Fisheries Entry Commission 2004.