Assessment of alternative indigenous fish species for culture in Ghana; case study of Chrysichthys nigrodigitatus (Lacepède, 1803)

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November, 2016
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This study consisted of two parts with the first assessing fish farmers’ knowledge on Chrysichthys nigrodigitatus in the Ashanti Region while the second aspect assessed the growth performance, feed utilization and body composition of C. nigrodigitatus on formulated diets. Aspects of the life history traits, ecology and natural distribution of C. nigodigitatus were investigated through a survey on indigenous knowledge on the species. Five farmers in Kumasi and its environs were selected and interviewed to gather information on the species. Overall knowledge on the species was low, farmers indicated that C. nigrodigitatus is dominant in the Offin River. The species is omnivorous, survives under pond conditions, feed on compound feeds with appreciable growth of 0.5-1 kg in 6 months. There is the need to protect the species because of their restricted distribution. An experiment was conducted over 10 weeks to determine the optimal inclusion level of protein in diets for C. nigrodigitatus, in twelve indoor 60-L rectangular glass tanks designed as flow through systems. Four experimental diets were formulated to be isoenergetic containing varying crude protein (CP) levels (32.1%, 34.6%, 42.8%, and 47.1%) using fish meal/soybean meal as sources of protein. Each dietary treatment was run in triplicate with 12 fingerlings (initial weight 16.30 ± 0.07 g) in a completely randomized design. Results showed that body weight gain (BWG%) and specific growth rate increased up to 42.8% (P <0.05) but declined at 47.1% CP. Protein efficiency ratio followed a similar trend with no significant differences between the treatments. Feed conversion ratio (FCR) decreased with increasing dietary protein level. Dose-response analysis in addition to the polynomial broken stick regression ascertained that the optimal protein requirement in diets for juvenile C. nigrodigitatus is 42.8%. Data from proximate composition of fish flesh showed that C. nigrodigitatus had CP (15.77%- 19.37%), lipid (2.8%-5%), moisture (73.26%-73.69%) and ash (3.8%-4.96%). It is recommended that diets for juvenile C. nigroditatus are formulated with a protein inclusion level of 42.8%.
A thesis submitted to the Department of Fisheries and Watershed Management, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the degree of Master of Philosophy in Aquaculture.