"Length-at-age and Size-Selective Mortality of the Western Basin Lake E" by Emily Crisovan

Date of Award

2011

Publication Type

Master Thesis

Degree Name

M.A.Sc.

Department

Biological Sciences

Keywords

Biology.

Supervisor

Ciborowski, Jan (Biological Sciences)

Rights

info:eu-repo/semantics/openAccess

Abstract

Size-selective mortality is common in systems where selective harvesting targets a specific size- or age-class. In general, commercial and recreational fisheries selectively remove the largest and fastest growing individuals, which may have evolutionary consequences. My goals were to examine length-at-age patterns, age at first and full recruitment to the fishery, and to determine if size-selective mortality existed in a commercially and recreationally fished population of walleye in Lake Erie of the Laurentian Great Lakes between 2000 and 2008. Mean fork length-at-age was found to increase from west to east within Lake Erie for age 2 and 3 walleye. However, mean fork-length at age 1 was not statistically different among sampling areas. Walleye first recruited to the fishery at age 1 and were not fully recruited by age 3. Smaller (slower growing) individuals were found to disproportionately survive to older ages than faster-growing fish, indicating that size-selective mortality of larger (faster growing) fish occurred. Size-selective mortality will likely have a negative effect on morphological (i.e., body size) and life history traits.

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