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Executive Summary

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Document (.pdf, .doc)
1904
Published: 
Thursday, January 1, 1976
U.S. Agency for International Development
The research objective was to breed the milkfish, Chanos chanos, in captivity and to raise the fry from the egg. In the first year, eight very mature fish were captured and deemed ready for final spawning inducement. One fish (with eggs 0.818 mm in diameter) hydrated and was partially ovulated by two injections of 25 mg salmon gonadotropin SG-G100. The eggs were not fertilized. The injection procedure of excessive handling and sampling of three other fish resulted in early atresia (reabsorption) of the oocytes. Two fish died from the sampling and handling procedures, and two proved to be too immature with eggs below 0.6 mm in diameter. The preliminary results indicate that oocytes of 0.8 mm and above are at a critical stage (or beyond), and at which immediate hypophysantion is needed. Injection cannot be delayed. Excessive handling or stress at this stage causes rapid stresia of the oocytes. It appears that oocytes of about 0.7 mm are more suitable for reacting positively to injections. The size of an ovulated egg is about 1.2 mm in diameter. General husbandry methods have been developed for adults in captivity, and a diet formulated which appears to be acceptable. Safe handling systems have been developed using ice, and hypotheses made for the results of this treatment and general conditions of stress.
Theme(s) & Sub-theme(s): 
Aquaculture
Resource type: 
Project Report
Resource Scale: 
Global

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