Date of Award

Fall 12-2014

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Chair

Dr. Eric Saillant

Committee Chair Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 2

Dr. Nancy Brown-Peterson

Committee Member 2 Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 3

Dr. Robert Joseph Griffitt

Committee Member 3 Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 4

Dr. Jeffrey Lotz

Committee Member 4 Department

Coastal Sciences, Gulf Coast Research Laboratory

Abstract

The quality of red snapper Lutjanus campechanus eggs is highly variable and unpredictable in aquaculture, leading to high mortality during early larval rearing. In this work, the viability of red snapper eggs was investigated from fertilization until larvae expired due to exhaustion of vitellin reserves. The studied spawns were obtained via strip spawning wild-caught (n=17) and captive (n=7) females following hormonal induction. The fertilization rate, the hatch rate, and the duration of survival of unfed larvae post hatch were weakly correlated to each other, revealing occurrence of distinct and independent components of egg quality.

Spawns from captive females were characterized by a longer latency interval between hormonal induction and ovulation, lower fecundity, and lower hatch rates, as compared to those from wild females. Among the wild brood fish, a positive correlation was observed between the age of the female and the hatch rate.

The proximate composition, fatty acid, and amino acid profiles of the ova did not differ significantly between spawns from captive and wild females.

RNA-sequencing analysis revealed that the standardized measure of gene expression differed significantly between wild and captive groups for 1,349 mRNA transcripts. Variation in hatch rate was significantly related to changes in 1,304 transcripts abundance. Other egg quality variables were only associated with variation in abundance of smaller subsets of transcripts (392-696), suggesting that maternal mRNAs had a more pronounced effect on the embryonic development. More than 40% of the transcripts related to hatch rate were also associated with female age, suggesting that the better hatching success of eggs from older females is related in part to maternal mRNAs content.

During challenge experiments conducted to determine oxygen and ammonia requirements during incubation and early larval rearing, significant mortalities were observed when dissolved oxygen levels were lower than 3 mg L-1 and unionized ammonia levels greater than 0.2 mg L-1.

Continued exploration of the relationships between egg quality parameters and endogenous characteristics of ova or developing embryos is warranted.

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