Partial economic analysis for penaeus indicus h. Milne edwards (1837) semi - intensive ulture at theMtwapa mangrove Creek,Kenya
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Shrimp farming IS carried out in intertidal areas in most parts of the world leading to transformation and loss of habitat. In South East Asia, Latin America and some parts of the Western Indian Ocean, shrimp aquaculture has led to loss and degradation of mangrove forests. The current study aimed at demonstrating the economic viability and environmental sustainability of small scale semi intensive farming of Indian shrimp, Penaeus indicus (H. Milne Edwards, 1837). The study was carried out in manure fertilized ponds in Mtwapa mangrove creek, Kenya (03",57.295' S , 039", 42.943' E). A total of 4 experimental ponds were used. The experimental design involved the use of three hap as per pond as experimental units. The following treatments were applied: Treatment 1: Control (no manures added), Treatment 2: chicken manure, Treatment 3: urea and Treatment 4: cow dung. During the 3.5 months study period, weekly water quality parameters, including dissolved oxygen, temperature, pH and salinity were measured in situ both in the morning and afternoon. In addition, phosphate, nitrate, nitrite and total ammonium nitrogen (TAN) were measured fortnightly in the laboratory. Phytoplankton and zooplankton densities were monitored monthly. The growth performance of the shrimp was monitored fortnightly by measuring their weight (g) and length (mm). From these, specific growth rate (SGR), Net shrimp yield (NSY) and Annual production (AP) were calcualted. A partial economic analysis was carried out at the end of the culture period in order to determine economic viability of the system. Water quality parameters were significantly different (p< 0.5) in each treatment. Mean dissolved oxygen in the morning for treatment 1-4 was 6.33, 7.59, 7.11 and 5.17 mgl." respectively. TAN levels in treatment 3 (urea) recorded a peak of 0.87 mgl.i'which was significantly higher (p <0.5) than in the other treatments. Specific Growth Rate (SGR % day') recorded for treatment 1-4 were 1.73, 2.34, 2.13 and 2.18 respectively. Similary, net shrimp yield (NSY Kgha') for treatments 1-4 was 12.35, 15.93, 14.65 and 18.87 Kgha respectively. while annual production (AP Kgha.ryr') for treatment 1-4 was 42.48, 54.87, 50.45 and 64.97 Kghayr respectively. Treating ponds with cow dung (Treatment 4) gave the highest yield. Results of experimental fishing indicated availability and abundance of post larvae of P.indicus throughout the season reaching a maximum mean of 0.67 shrimp m'which is not considered sustainable. These densities are also low compared to 173 shrimp m" in Ghubat bay which is a major shrimp fishery area in the Sultanate of Oman. A partial economic analysis of shrimp farming showed that there was an overall net loss in all the treatments. The cost of cultivating shrimps ranged from 251,500 -302,350 KSh ha-' season", in treatment I and 4 respectively. A loss was recorded in all treatments with treatment 4 having the highest loss of 287,850 Ksh ha season". From this study, therefore, it was concluded the intensive small scale shrimp farming under the conditions of the current study was not economically viable. Future studies should aim at exploring ways of making small scale shrimp farming more economically viable by developing cheap and locally available feeds which will boost production and hence income by allowing for higher stocking densities and also by increasing the growth rate of the shrimp. Also a shrimp hatchery must be put in place for the provision of seed before shrimp farming in Kenya can be promoted.