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

More documents

Recommendations

Info

depending more on body size than age. Most adult grayling leave their overwintering areas andenter a bog-fed or unsilted rapid-runoff stream to spawn (Tack, 1980). Only in large unsiltedrapid runoff rivers do grayling spawn in the same stream in which they overwinter; even in theserivers, most grayling migrate upstream to parts not used for overwintering (Armstrong, 1986).Migrations to feeding areas depend on the size and age of the fish. Post-spawning adult fishmove into higher reaches in the river, above or in the vicinity of the spawning grounds to feed.Subadults tend to migrate to feeding grounds in the middle portions of the stream, whilejuveniles occupy lower reaches of the stream.The arctic grayling is common throughout Alaska and northern Canada and is found fromthe west side of Hudson bay to the western shores of Alaska. In the Copper River drainage, theymost likely occupy most clearwater tributaries and streams. They are known to exist in HaleyCreek, Uranatina River, O’Brien Creek, Gulkana River, Tonsina River, Bear Creek and others.The Gulkana River is noted as having a particularly abundant grayling fishery.Rainbow Trout and SteelheadRainbow trout (Oncorhynchus mykiss) are widely distributed throughout western NorthAmerica and have been introduced around the globe. The following life history summary willfocus on those populations of rainbow trout inhabiting the coastal regions of North America.Rainbows are very similar to their salmon relatives, but exhibit a variety of life histories withsignificant differences. Coastal rainbows comprise distinct populations of fish that migrate, andfish that do not. The behavior of the individuals making up these populations is remarkablyconsistent (Watson, 1999). Rainbow trout live as residents to freshwater for the duration of theirlives. Rainbow trout also occur in an anadromous form, which are called steelhead. These twovery distinct forms may often overlap in the same reaches of a stream and can sometimes bedifficult to tell apart based on appearance alone.Page 16 of 27
Figure 14. Typical rainbow trout coloration (left) (Morrow, 1980). The author (right) with atypical steelhead trout in ocean colors.There are no major physical differences between rainbow and steelhead trout. However,the nature of their differing lifestyles has resulted in subtle differences in color, shape andgeneral appearance (Van Hulle, 2002). Rainbow trout are often much more colorful, with greaternumbers of black spots and a characteristic red band along the lateral line. Steelhead, especiallyduring their ocean phase, are bright silver, with few spots. As they enter freshwater, theircoloration begins to resemble that of the resident rainbow trout (Fig.14).Rainbow trout are generally considered to be spring spawners, with most fish spawningin mid-April to late June. Typical of most salmonid behavior, females will select the nest site,while males exhibit courting behavior and chase off competing males. Eggs are laid in redds duginto the gravel of riffle areas above pools. Fry will emerge after consuming their yolk sacs asalevins and will then move to sheltered areas of the stream. Juvenile forage primarily on insects,while adults forage opportunistically on larval and adult insects, crustaceans, and other small fishand even leaches. Migration patterns of rainbow trout are variable, but usually do not involvegreat distances. Stream resident trout will remain in the stream after spawning, while lakeresident rainbows will return to their lake habitats after completing their spawning run in atributary stream. Many rainbow trout spawn more than once. If environmental conditions aregood, rainbows may spawn annually for up to five successive years (Hartman, 1959).Steelhead return to their natal streams to spawn at different times of the year, dependingon the particular stream and latitude. In Alaska, some rivers receive strong runs of steelhead inthe fall, while some southeastern rivers have spring run fish that arrive in mid-April, May andJune. Steelhead trout in the Copper River are believed to have a fall run timing (Fleming, 1999).Fry emerge from the gravel in mid-summer and then seek refuge along the steam edges and quietwaters. Juveniles spend up to three years in freshwater before undergoing smoltification andmigrating to the sea in spring. After reaching the ocean, steelhead will feed aggressively andgrow large for up to three years before returning to spawn. While in the ocean, steelhead mayfeed on crustaceans, squid, small fish and large zooplankton.Steelhead are distributed all along the North American coast as far south as southernCalifornia, and as far west as the Kamchatka Peninsula. Rainbow and steelhead trout populationsthat inhabit the Upper Copper/Upper Susitna drainages are considered the northernmost wildPage 17 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 10 and 11: sometimes specialize on certain pre
Page 12 and 13: stocks of chum stay out for 3-4 yea
Page 14 and 15: and early June. Alaganik Slough and
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

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?