Life Histories and Distributions of Copper River Fishes (.pdf)

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sometimes specialize on certain prey items. As pink salmon fry become larger, they begin tomigrate to off shore waters. Their diets change to incorporate larger items such as fish, andsquid.Figure 8. Pink salmon fry after emergence (Groot and Margolis, 1991).Pink salmon have a very rigid two-year life cycle, with 18 months spent at sea. Oceanmigration routes can involve considerable distances, and usually consist of a large counterclockwisecircular pattern. This pattern is completed once during the ocean phase. Sexualmaturation begins on the last leg of the ocean migration, but is not completed until feeding hasstopped and the fish has entered fresh water. The rigid two-year life cycle of the pink salmonmay contribute to the odd and even-year cycles. Odd-year fish tend to be more closely related toodd-year fish of other rivers than to even-year fish of the same river. This is also a reflection ofthe fact that pinks generally have less accuracy in returning precisely to their natal streams. Thistendency to stray away from their home streams is thought to help support populationsthreatened by disaster (Watson, 1999).Figure 9. Male (top) and female (bottom) pink salmon in spawning colors (Morrow, 1980).Page 10 of 27
Pink salmon are distributed between Point Hope and Point Barrow and have beenreported as far west as the Lena River on Russia’s northern shores. Breeding populations alsooccur all along the Bering Sea coastline, and down to Puget Sound. These fish are able tocolonize more northern habitats, since they can escape freshwater quickly before winter bringstemperatures to lethal levels, and thus have extended their distribution considerably. Inshore runsin southeastern Alaska return primarily in July and August, but vary according to latitude andodd/even years (Fig. 9). Spawning occurs mostly in late August and September. In the CopperRiver, these fish should be seen in the lowest portions of the river, and in the intertidal portionsof the Delta.Chum SalmonThe chum salmon, Oncorhynchus keta (Walbaum), is second only in adult size to thechinook. Individuals have been reported at over a meter long, weighing over 20kg. Chumsalmon, like the pinks, often spawn below the upper reaches of high tide, but may also makelonger migrations. Like the pink salmon, chum salmon fry migrate downstream soon afteremerging from the gravel. Fry may migrate long distances to the ocean, or just a few hundredmeters, depending on where they were spawned. Most migrations occur at night, but someexceptions occur. Longer migrations require fish to travel during some daylight hours to coverenough distance each day. Turbid glacial waters also provide similar protection from predatorsthat nightfall usually brings. Chum fry often travel in large shoals to reduce individual predationrisk.Estuaries provide an important stopover point for chum fry as they make their waytowards the ocean. Chum fry increase their chance of survival in the ocean by growing quicklyon the rich food supply of estuary habitats, although they are less dependent on this stage ofmigration than are chinook. The time spent in the estuary is variable, but usually lasts a fewweeks. It seems likely that chum salmon of the Copper River system would capitalize on thelarge Copper River Delta as an ideal rearing habitat. The timing of juvenile chum salmon entryinto seawater is commonly correlated with the warming of the nearshore waters and theaccompanying plankton blooms (Groot and Margolis, 1991). After inshore resources havedeclined, and the chum have reached an appropriate size to avoid predation, they then move tooffshore waters. Most chum spend 2 to 5 years at sea, explaining their larger size. NorthernPage 11 of 27
Page 1 and 2: Life Histories and Distributions of
Page 4 and 5: spawning areas in this region are t
Page 6 and 7: Figure 4. Chum salmon fry (Groot an
Page 8 and 9: summer, and others, as in the Karlu
Page 12 and 13: stocks of chum stay out for 3-4 yea
Page 14 and 15: and early June. Alaganik Slough and
Page 16 and 17: depending more on body size than ag
Page 18 and 19: stocks of this species in North Ame
Page 20 and 21: that 10 and 12 years old. The retur
Page 22 and 23: with several bony plates, giving th
Page 24 and 25: tributaries in the upper watershed
Page 26 and 27: Fleming, D. F. 1999. Surveys and st

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