Graduate Thesis Or Dissertation
 

Determination of marine migratory behavior and its relationship to selected physical traits for least cisco (Coregonus sardinella) of the western Arctic coastal plain, Alaska

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  • With increased resource development on the western Arctic coastal plain of Alaska (especially within the oil extraction industry) it is important to understand the basic life history attributes of whitefish stocks in the region in order to ensure appropriate management. These fish are a crucial part of subsistence harvests for native Alaskans. Multiple forms of the whitefish least cisco (Coregonus sardinella) have been described based on both appearance and life history traits. Two major forms of least cisco have been mentioned in the literature: a larger normal amphidromous form with fork lengths of approximately 420 mm and a dwarf lake resident form with lengths up to 230 mm. However, there is considerable evidence for additional forms and life history strategies of least cisco. I investigated the relationship between migratory behavior and selected physical traits of least cisco in six lakes and one brackish lagoon in the western Arctic coastal plain of Alaska. I used electron microprobe technology to determine the levels of Sr and Ca in the otoliths of 258 least cisco in order to resolve their marine migratory life history. I also investigated the relationship between migratory behavior and the numbers of gill rakers, lateral line scales, anal rays and dorsal rays as well as condition factor. The vast majority of least cisco captured in these sites were normal in form, yet only ~12% of all samples yielded any sign of sea-run behavior. Evidence for migratory behavior was low even for sites within close proximity to brackish waters. Fish exhibiting marine migratory behavior tended to make their first migrations to sea before age three (mean=2.6 years), although fish in one coastal site (Joeb's) averaged over 5 years of age at first marine visit. There was some evidence of higher condition factors for fish with sea-run migratory experience. There were significant differences in lateral line and dorsal ray numbers among sites but none for anal rays or gill rakers. Variability in all of these characters was high, and fish from coastal sites tended to have greater variability than those from inland sites. Only dorsal rays showed significant differences in meristic traits between sea-run and resident least cisco. These results suggest that least cisco exhibit high variability in physical traits. Also, least cisco appear to be flexible in their use of the marine environment, even within similar forms in the same lake. Some of the most basic life history characteristics of least cisco remain uncertain. With increased resource extraction occurring on the western Arctic coastal plain of Alaska, it is important to continue to investigate these and other life history strategies so as to ensure a sustainable fishery for native inhabitants of the region.
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