Date of Award

Spring 5-2007

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Chair

Dr. Bruce H. Comyns

Committee Chair Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 2

Nancy Brown-Peterson

Committee Member 2 Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 3

Dr. Terry Henwood

Committee Member 3 Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 4

Dr. Jeffery Lotz

Committee Member 4 Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 5

Dr. Chet Rakocinski

Committee Member 5 Department

Coastal Sciences, Gulf Coast Research Laboratory

Abstract

Age, growth and reproduction research was conducted on yellow edge grouper, Epinephelus flavolim batus, obtained from the commercial harvest and National Marine Fisheries Service scientific cruises in the Gulf o f Mexico (GOM) during 1979-2005. Fish ranged in size from 107-1,170 mm total length (TL). Ages ranged from 0 to 85 years; maximum age greatly exceeded previously reported ages. Bomb-produced 14C was used to validate ages determined by counting otolith growth increments. A strong linear relationship existed between otolith weight and fish age (R2 = 0.84). The von Bertalanffy growth equation was TL=970.8(l-e"° 063(1+4 84)). Length and age structure yellow edge grouper harvested today are considerably smaller and younger than those in the past. Yellow edge grouper are monandric protogynous hermaphrodites and have an extended spawning season from March through September. Results indicated a change in the sex ratio over the last 25 years due to a 14% decrease o f males. Size at sexual maturity and size at transition have also decreased.

Yellow edge grouper were distributed throughout the GOM, but regional differences in population density, size and age structure and sexual maturity suggest at least two or three separate stocks occur in the GOM. Yellow edge grouper in the western GOM were larger, older and more abundant while fish in the eastern GOM were smaller and younger. Yellow edge grouper in the eastern GOM aggregate in denser patches than those in the western GOM.

Yield-per-recruit and spawning stock biomass-per-recruit analyses were applied to determine biological reference points and evaluate the status o f the fishery. Results indicated stocks cannot sustain high levels o f fishing mortality (F

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