Use of whole-stream patterns of age segregation to infer the interannual movements of stream salmonids: A demonstration with arctic grayling in an interior Alaskan stream

Authors
Citation
Nf. Hughes, Use of whole-stream patterns of age segregation to infer the interannual movements of stream salmonids: A demonstration with arctic grayling in an interior Alaskan stream, T AM FISH S, 127(6), 1998, pp. 1067-1071
Citations number
20
Categorie Soggetti
Aquatic Sciences
Journal title
TRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY
ISSN journal
00028487 → ACNP
Volume
127
Issue
6
Year of publication
1998
Pages
1067 - 1071
Database
ISI
SICI code
0002-8487(199811)127:6<1067:UOWPOA>2.0.ZU;2-3
Abstract
I show how patterns of whole-stream age segregation can be used to infer in terannual movements of stream salmonids. First, estimates of recruitment an d mortality rates for the population as a whole are calculated using data f rom fish sampled along the entire length of the river. These rates are used to simulate the age structure of an idealized population. Next, each age-c lass is divided among lower, middle, and upstream reaches, according to the proportions observed in the real population. Finally, the amount of intera nnual movement is estimated from the pattern of age segregation that would exist after 1 year if recruitment and mortality were allowed to act on the simulated population but no fish moved between reaches. Application of this technique to the "older-fish-upstream" distribution pattern of Arctic gray ling Thymallus arcticus in an Alaskan river showed that substantial movemen ts are required to maintain the observed pattern of age segregation. Annual emigration was estimated at 24%, 11%, and 0% for downstream, midriver, and upstream reaches respectively, estimated immigration was 2%, 30%, and 51%.