Growth Performance, Survival and Economics of Clarias Gariepinus (Burchell 1822) Under Mono- And Polyculture with Oreochromis Niloticus on Varying Crude Protein Levels

Abstract

With the progressive decline of capture fisheries and human population upsurge worldwide, aquaculture is expected to play a great role in ensuring sufficient fish in the market. Thus, aquaculture is promoted by world food production agencies and governments, and has experienced significant growth. However, for African countries such as Kenya, aquaculture production is disproportionately lower than capture fisheries. Thus, there is urgent need to improve aquaculture production in these countries to meet the growing demand for fish through effective aquaculture practices and systems. Clarias gariepinus, a fish that has been underutilized, with qualities such as high fecundity, fast growth, and high tolerance to environmental changes is a key candidate for improving aquaculture production in Africa. Currently, there are no affordable and quality feeds, and suitable aquaculture production systems for C. gariepinus. The full potential of growth performance of C. gariepinus in cages fed on low CP is yet to be established.Fry/larval survival in most hatcheries is low and requires improvement. Hence, this study aimed to evaluate the growth performance, survival and economics of C. gariepinus raised as monoculture and in polyculture with Oreochromisniloticus, to determine the effectiveness of low crude protein (CP) level in C. gariepinus diets andalso in fry/larval to fingerling survival. Clarias gariepinus and O. niloticus weighing averagely 3.0 ± 0.001 g and 10.0 ± 0.001 g respectively were placed at a stocking density of 70 fish in a 2 m by 2 m hapa as mono- or 1:1 ratio in polyculture. The hapas were placed randomly in 400 m2 earthen pond. The fish were fed on diets containing caridina, soybean, wheat pollard and cotton seed cake combined in different CP ratios to give 25%, 30%, and 35%. Crude protein ratio of 28% was used as control.Feeding was done thrice daily at 3% body weight for 182 days. Growth parameters and survival data were taken fortnightly. Enterprise budgets were used to compare the relative profitability of monoculture and polyculture system fed on varying CP diets. For fry/larval experiment, fish larvae (0.03 ± 0.01 g) were stocked in glass aquaria (15 liters) at the rate of seven fish/liter and cultured for six weeks with measurements of parameters being taken weekly. Statistical comparisons were performed by one-way ANOVA with Tukey’s post-test or Unpaired t-test using GraphPad Prism software. Clarias gariepinus fed on formulated diets had significantly higher growth performance with respect to weight gain(CP 35% p<0.001), length gain(CP 35% p<0.001), specific growth rate(CP 35% p<0.01). However for feed conversion ratio and survival there were no significant differences from those fed on commercial diet. Results on culture systems indicated that polyculture had significant output than monoculture on all feeds (p<0.001).The performance and economicindices of polyculture were significantly higher than monoculture system irrespective of the CP level (p < 0.05). Moreover, C. gariepinus larvae fed on the formulated diets exhibited higher performance and survival than those fed on commercial feed (p < 0.05). These results demonstrated that formulated feed with relatively low CP levels could potentially be utilized as an alternative to the commercial feed in C. gariepinus fingerling or grow-out culture. Further,C. gariepinus polyculture with O. niloticus is more promising in terms of performance and economics than the monoculture system. The present findings strongly suggest that farmers and policy makers could adopt C. gariepinus polyculture systems with cheap and low CP diets to maximize aquaculture productionin-order to meet the country’s animal protein need and the overall agenda on food security.