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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
Author(s) -
Hughes Nicholas F.
Publication year - 1998
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1998)127<1067:uowspo>2.0.co;2
Subject(s) - grayling , arctic , population , upstream and downstream (dna) , fish <actinopterygii> , fish migration , fishery , environmental science , geography , physical geography , ecology , upstream (networking) , biology , demography , computer network , sociology , computer science
I show how patterns of whole‐stream age segregation can be used to infer interannual movements of stream salmonids. First, estimates of recruitment and mortality rates for the population as a whole are calculated using data from 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‐class is divided among lower, middle, and upstream reaches, according to the proportions observed in the real population. Finally, the amount of interannual 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 grayling Thymallus arcticus in an Alaskan river showed that substantial movements 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%.