Theses and Dissertations


Name: Williams, Kresimir

Degree: MS

Chair: Ronald P. Phelps


University: Auburn, University

Location: Auburn, Alabama

Date: 2002

Pages: 95

Keywords: Red snapper,larval development,water temperature,induced spawning


Development of early larvae of red snapper (Lutjanus campechanus) was described through the end of endogenous resources and the development of feeding ability to address possible causes of larval mortality associated with first feeding, which has limited sustainable production of juveniles in captivity. Additionally, the effects of temperature on development rate and utilization of yolk materials were examined in order to establish larval incubation protocols. All measurements were made from digital images of live larvae, using an image analysis. In the first study, larval development and yolk utilization was described for unfed larvae over the period of 5 days post-hatch. Larvae were maintained at 28 ± 0.7 °C for the duration of the trial. Larval development was rapid, with yolk reserves consumed by 36 hours post-hatch, and mouth articulation evident by 42 hours, at which time 1 + 0.5 % of oil globule resources remained. Larval standard length reached a maximum of 2.84 mm at 18 hours post-hatch, after which length retracts, along with body depth and width, which start to decline following mouth articulation. In the second study, one preliminary trial and one experimental trial were conducted to determine the influence of temperature on yolk conversion efficiency growth, and survival of red snapper larvae. Larvae were regularly monitored for yolk volume, oil globule volume, and length by means of an image analysis system. Samples were also analyzed for nucleic acid ratios (RNA:DNA). Experimental treatments consisted of 26, 28, and 30 °C. The fastest growth rates and yolk utilization rates were observed at 30 °C, with time of mouth articulation estimated at 39 hours post-hatch, eight hours earlier than seen at the 26 °C treatment. All treatments exhibited negative growth, with larvae reared at 26 °C reaching greatest length (2.81 mm). The amount of oil globule reserves measured at the moment of full orbit pigmentation did not differ significantly among treatments (P = 0.19), however, larvae raised at 30 °C were smaller (3~5 %, P < 0.05), and had a significantly lower survival and RNA:DNA ratio (P < 0.05) than larvae raised at 26 °C. Survival to development of first-feeding ability declined with increasing temperature, being 7.5 % at 30 °C and 55 % at 26 °C. The results of this study indicate that higher temperatures are inhibitive to growth and survival of red snapper yolk-sac larvae, and should be avoided in the hatchery setting.

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