The problem when mixing different species is that it

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The problem when mixing different species is that it disturbs the pond frequently as not all species will be ready for breeding at the same period. Fish that are seined often will be stressed and be subject to injuries and loss of scales that will favor the development of diseases. Fish that usually spawn during the same period should be stocked together, especially if they have different feeding habits. The problem of disturbance is aggravated in some stations where spawned broodfish are returned to their original stocking pond. In the following weeks, that pond will be seined again for getting more broodfish for reproduction and spawned fish, already weakened by their spawning session, are then re-caught and cannot recuperate. The rule should be that after spawning fish should be stocked into another pond for reconditioning, where no seining will occur until the next season. 3.4 NUMBER OF SPECIES All the former considerations should lead to limit the number of species present in a hatchery according to the number of ponds, their size and their water capacity. No fixed rules can be given here. In some stations with limited ponds areas or problems with water supply, 2 species should be a maximum. Tilapia can be added as it reproduces naturally.
Page 25 of 86 Self-Assessment Briefly answer the following questions. Your answers will be rated based on the rubrics. 1. What are the bases on which to select good future breeders? 2. What are desirable hereditary qualities typical of improved strains? 3. What are the basic economic parameters essential for the sustainable operation of a small fish hatchery? References 1) Demoulin, F. 1999. Guidelines for Broodstock and Hatchery Management. The Food and Agriculture Organization of the United Nations, Bangkok. 8 pp. Summary 1. For the purpose of broodstock management, the main species can be classified according to the following criteria: • The size at maturity • The method of reproduction (natural, semi-natural, artificial) • The location in the pond and the feeding behavior • The tolerance of adverse conditions 2. It should be noted that since fish ponds are almost all less than 1-meter-deep, the different feeding levels probably do not exist. From all these characteristics, it appears that: a) Fertilization of the pond, especially organic fertilization, is important to all species by increasing the amount of natural food present in the pond. b) Some species have the same feeding habits and therefore should not be stocked together as they will compete for the food. If stocked together the total stocking density should be decreased. 3. A common stocking rate is 1,000 kg of broodfish per hectare, which means 10 kg/100 m 2 . Such a rate supposes however that fish are stocked and maintained in good conditions: a) Water depth is as advised previously (1 to 2.5 m) and should be kept constant throughout the year.

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