Theses and Dissertations


Title: Fecundity estimation and induced spawning of Red Snapper, Lutjanus campechanus

Name: Bueno, Fabricio Tessmer

Degree: MS

Chair: Ronald P. Phelps

Resides:

University: Auburn University

Location: Auburn, Alabama

Date: 2002

Pages: 81

Keywords: Fecundity estimation,induced spawning,Red Snapper

Abstract:

Two studies were conducted: The first to determine the fecundity of wild red snappers, and the second to investigate the efficiency of an HCG induced spawning protocol. In the first study, ovaries from 146 wild red snappers were collected approximately every week from April 1 through September 9, 1999. Gonadosomatic Indices were calculated for all 146 fish, and fecundities were estimated for 99 fish. The results were used to characterize the spawning habits of wild red snapper in the Gulf of Mexico. The spawning season lasted from mid May through mid August. The total number of oocytes per fish increased with fish weight (R2=0.34, P<0.001), but the number of vitellogenic oocytes per fish was not related to fish weight (R2=0.033). Gonadosomatic index showed a significant linear relationship with total fecundity (R2=0.498, PO.001),potential fecundity (R2=0.440, P<0.001), total number of oocytes per female (R2=0.257, P<0.001), total number of pre-vitellogenic oocytes per fish (R2=0.22, P<0.001), and number of vitellogenic oocytes per fish (R2=0.406, P<0.001). The percentage of vitellogenic eggs in the ovary was not related to GSI (R2=0.11), but showed a linear relationship with potential fecundity (R2=0.62, P<0.001). There was indication of lunar cycle influence on GSI. Gonadal development accelerated when sea surface water temperature reached 25-26 C. In the second study, female red snappers were collected by hook and line during May, June and July 1999 to investigate the efficiency of a strip-spawning protocol when performed on HCG-induced and non-induced fish. Forty-eight percent of females had hydrated eggs upon arriving at the lab. Floating egg fecundity and percent hatch were highest for females induced to spawn with HCG (mean ± SD = 95,896 ± 63,742 eggs/kg, and 40.3 ± 23.3%, respectively), and lowest for non-induced fish (31,711 ± 26,443 eggs/kg, and 12.6 ± 14.8%, respectively). Mean response time to HCG injection was 26.9 ± 3.9 hours. Red snappers have a prolonged spawning season typical of asynchronous spawners. The spawning season is limited to the warm summer months. They are a highly fecund species, and large numbers of eggs and larvae can be obtained from hormone-induced spawns. Apparently, only a fraction of the vitellogenic oocytes in the ovary can be induced to mature using an HCG-inducement protocol.

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