Date of Award

1997

Degree Type

Thesis

Degree Name

Master of Science in Zoology

Department

Zoology

First Advisor

David A. Bengtson

Abstract

Experiments were conducted to investigate larval mortality in cultured summer flounder during the first two weeks after hatch. The importance of feeding success, parentage, addition of algae, water quality, and the microbial community to mortality during this period were investigated. Larvae were raised in 2-L bowls at initial densities of 50 and 75/L with light aeration, 12L:12D photoperiod, and regular 1-L water changes. In all experiments mortalities were recorded and removed daily. In the first two experiments daily samples of larvae were taken to assess feeding success and to relate that to survival. The second experiment investigated the effects of both feeding success and the addition of algae to larval culture bowls on larval survival. The third experiment investigated the effects of water quality and bacterial load on survival during the experimental period. The first two experiments indicated that failure to establish .feeding is probably not the cause of catastrophic mortality of the larvae, although a statistical relationship existed between feeding incidence and survival in two of six cases. High variability (34 ± 38% n=82) in survival was seen in the first two experiments (both within and between parental crosses) suggesting that catastrophic mortalities were due to rearing conditions rather than gamete quality. The addition of algae to larval cultures increased survival from 13 ± 24% (n=33) during the first experiment to 46 ± 39% (n=49 ) during the second experiment. The final experiment indicated that larval mortality was not linked to the measured microbial or water quality conditions. The relationship between the percentage of floating eggs at time of fertilization and survival at 10 DAH was found to be not significant, providing further evidence that gamete quality was not as important as rearing conditions in these experiments.

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