Graduation Date

Fall 2017

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources, option Fisheries

Committee Chair Name

Tim Mulligan

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Dr. Joe Tyburczy

Second Committee Member Affiliation

Community Member or Outside Professional

Third Committee Member Name

Dr. Laurie Richmond

Third Committee Member Affiliation

HSU Faculty or Staff

Subject Categories

Fisheries

Abstract

Traditionally, the recreational fishery for Pacific halibut has been open in California from 1 May through 31 October. In 2014, however, the Pacific halibut fishery was closed in California during the month of August for the first time in history in an effort to reduce harvest and bring total catch closer to what is allocated to our region by the Pacific Fisheries Management Council (PFMC) Catch Sharing Plan. To determine the effects that the closure had on businesses along the North Coast, I conducted an economic impact survey in 2014. The results of the survey showed that fishing-related businesses lost between 0 percent and 8 percent of their revenue in 2014, as a result of the closure; lodging and traveler service companies lost between 0.3 percent and 1 percent of their revenue in the same year. None of the businesses changed the number of employees as a result of the closure. We estimated a decrease in revenue for businesses on the North Coast to be between $189,750 and $222,250.

Age and growth are important components in stock assessment models, but biological data in general are scarce on populations of Pacific halibut found in northern California. For this reason, I conducted a study that examined the age and growth of Pacific halibut landed in this region, expanding on a previous study to examine possible interannual variation in the age/growth structure, and broadened the study into central Oregon, to compare two distinct bioregions. Results from my study show that mean size-at-age of female Pacific halibut from northern California and central Oregon was larger than those from the IPHC setline surveys in most of Alaska, but similar to those from Oregon and Washington. In addition, fish from this study in northern California and central Oregon were smaller for a given age than those from the 2014 IPHC survey conducted in northern California. Possible reasons for the trend in size-at-age include poor oceanic conditions during my study, the movement of slower-growing halibut into northern Californian waters, and sampling error.

The maturity stage of female gonads is also an important component in stock assessment models, but these data are also scarce for Pacific halibut populations in northern California. For this reason, I conducted a study that characterized the maturation of Pacific halibut landed in northern California and central Oregon. I also compared the macroscopic maturity staging method currently utilized by the IPHC against the more rigorous microscopic methods (microscopic staging and measuring oocyte diameter). Results of this study and that of Perkins (2015) indicate that Pacific halibut caught in northern California and central Oregon matured three years earlier than those caught during IPHC setline surveys in waters off of Alaska, and about a year earlier than those caught by the IPHC in Oregon and Washington. The length-at-50%-maturity in Pacific halibut caught in northern California and central Oregon was smaller than that of fish caught in the IPHC setline survey. In addition, for all three stages of maturity observed in females (immature, mature, and resting; spawning-stage females were not observed) there was at least 66 percent agreement between macroscopic and histological staging methods, with the highest level of agreement (94 percent) seen in mature ovaries. This study largely validated the macroscopic staging methods because of its high accuracy in identifying mature ovaries; the inaccuracy in distinguishing resting versus immature ovaries had little effect on length- and age-at-maturity analysis.

Citation Style

APA

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