The length-weight relationship, food habits and condition factor of wild juvenile milkfish in Sri Lanka
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Wild juvenile milkfish (Chanos chanos) were obtained from Negombo lagoon in September 1984. Thirty-one specimens (92–186 mm FL) had a fork length-body weight relationship of log W = −5.6083 + 3.2598 log L. These fish were caught in the early morning and had empty guts. The mean condition factor (K) was 8.7. The intestine length to fork length ratio (I) was 3.7. Two large specimens (245 mm and 340 mm FL) caught around mid-day from the ocean off Negombo had full guts. Food was mostly blue-green algae, diatoms and detritus, with a number of copepods and nematodes. These fish had K values of 11.7 and 13.6 and I values of 8.1 and 8.5. The age and the month of spawning of these fish were back-calculated using known milkfish growth rates. It seems that in Sri Lanka, milkfish spawn from January to at least November.
Contribution No. 174 of the SEAFDEC Aquaculture Department.
CitationBagarinao, T., & Thayaparan, K. (1986). The length-weight relationship, food habits and condition factor of wild juvenile milkfish in Sri Lanka.
We thank Dr. Y. Taki and Dr. H. Kohno of the SEAFDEC Aquaculture Department for critical review of the manuscript. This study was partially supported by the International Development Research Centre (IDRC, Canada) through a grant to the SEAFDEC Aquaculture Department under Project No. 3-P-81-0171 (Phase III).
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The use of chemicals in carp and shrimp aquaculture in Bangladesh, Cambodia, Lao PDR, Nepal, Pakistan, Sri Lanka and Viet Nam. M Phillips - In Use of Chemicals in Aquaculture in Asia : Proceedings of the Meeting on the Use of Chemicals in Aquaculture in Asia 20-22 May 1996, Tigbauan, Iloilo, Philippines, 2000 - Aquaculture Department, SEAFDECThis paper provides an overview on the use of chemicals in seven countries in Asia (Bangladesh, Cambodia, Nepal, Laos PDR, Pakistan, Sri Lanka and Viet Nam), with an emphasis on coastal shrimp aquaculture and inland carp farming systems. The data come primarily from a recently completed survey of aquaculture farms in Asian countries conducted under the ADB/NACA Regional Study and Workshop on Aquaculture Sustainability and Environment. The issues discussed include the types and uses of chemicals in shrimp and carp culture, farm management practices and use of chemicals, hazards and adverse impacts associated with chemical use, alternative approaches to chemical use, and research recommendations. In inland carp farming, apart from lime and fertilizers, which are unlikely to give rise to any significant negative environmental impact, the overall use of chemicals is extremely low. Piscicides are used in some countries to control predators prior to stocking of ponds, but the use of antimicrobials and disease-control chemicals is limited to a small percentage (<5%) of producers. Most small-scale producers, who dominate aquaculture production in these countries, simply do not have the resources or need for such chemicals. The situation is similar in shrimp culture, with lime and fertilizers, followed by piscicides, being the most common chemicals used. The use of antimicrobials increases with intensification in shrimp culture, and these chemicals are mostly used in more intensive shrimp farming. In both shrimp and carp culture, promotion of “primary” health management practices probably offers greatest scope for prevention of aquatic animal disease outbreaks and the need for chemical use.
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