Date

Fall 2019

Document Type

Master's Thesis (Open Access)

Degree Name

Master of Science (M.S.)

Department

Moss Landing Marine Laboratories

Abstract

Fish populations exhibit variation in life-history and demography based on a variety of biological, environmental, and anthropogenic factors. Understanding the spatial patterns in life-history variability for commercially exploited fish stocks is important when making management decisions and designating stock boundaries. Between 2015 and 2017, 2,189 Lingcod were collected from seven geographically distinct regions along the West Coast to investigate latitudinal patterns in population distribution, growth, timing of maturity, condition, and natural and fishing mortality. Life history parameters of growth, maturity, longevity, condition, and natural and total mortality were calculated and compared for Lingcod in each region and by sex. A principle components analysis was used to relate trends in life-history parameters to coastwide environmental patterns in sea surface temperature and productivity. Non-metric multidimensional scaling ordination plot and PERMANOVA were used to identify biologically relevant breakpoint(s) for Lingcod along the U.S. West Coast. The results from this study demonstrate that Lingcod exhibit strong latitudinal patterns in life history that is consistent with Bergmann’s Rule, where Lingcod from colder, northern waters grow faster and larger, live longer, mature at larger sizes, and have lower natural mortality rates than Lingcod from warmer, southern waters. Lingcod total mortality rates did not follow a latitudinal trend but were highest in Washington and Southern California regions, which is consistent with historic fishing practices, current fishing pressure, and local patterns of productivity within those regions. Between sexes, female Lingcod were found to grow faster and larger, live longer, mature at larger sizes, and were in worse condition than male conspecifics. These findings suggest that while Lingcod life-history traits related to age, growth, and condition are strongly influenced by localized patterns of temperature and oceanography along the coast, there can be considerable variation based on a regions’ history of exploitation. A biologically relevant breakpoint for Lingcod along the U.S. West Coast was identified at the central Oregon coast, dividing the Lingcod stock into northern and southern substocks. The coastwide Lingcod population and fishery may benefit by using this boundary as a biologically appropriate break point when conducting future stock assessments. Implications for applying these findings to other federally managed groundfish species and stock assessment models are discussed.

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