Graduate Thesis Or Dissertation
 

Influence of landscape-scale variables on the age and growth of coastal cutthroat trout Oncorhynchus clarkii clarkii in headwater streams

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/8336h485b

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  • This thesis provides the first general description of the natural variation in age structure, growth rates, and survival in headwater populations of coastal cutthroat trout Oncorhynchus clarkii clarkii from western Oregon, and a subsequent synthesis of these life-history characteristics across the range of the subspecies. Age, growth, and survival were estimated by analyzing scales from 4,250 fish collected from 37 headwater watersheds in western Oregon from 1999 to 2001. Age was validated for 234 marked and recaptured coastal cutthroat trout from two watersheds, and >94% of the scales exhibited the expected number of annuli between capture dates. Variation among readings was low (< 9%), and there was only a slight bias between readings for older fish (primarily age-5 fish). Missing first-year annuli, often observed in cutthroat trout subspecies, were not observed for these populations. Mean relative growth rates decreased with age and size. In three populations maximum age was 3 years, but in the majority, maximum age was 4 (24 populations) or 5 years (8 populations). Annual survival rates of age-3 coastal cutthroat trout (i.e., between age-2 and age-3) ranged from 23% to 65%. Akaike's Information Criterion (AIC) was used to select multiple regression models that "best" described biological response (i.e., length at age-1, mean length, and survival) to physical habitat variables. The model with January water temperature and calcium ions as predictor variables was the "best approximating model" for predicting mean length at age 1. The model with maximum pool depth and stream channel connectivity was most useful for predicting mean fish length in a watershed, and mean survival was best predicted by a model with mean July water temperature and maximum pool depth as predictor variables. Summary of range-wide life-history data for coastal cutthroat trout suggests that patterns in growth, age, and length do not follow a generalized geographic trend from north to south, and at least some differences appear to be related to life-history type.
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file details Rehe91307PDFthesis.pdf 2017-08-14 Public Télécharger