Effect of Stocking Density and Rearing Facility on Growth and Profitability of Tilapia rendalli Fry
A study was conducted to compare the growth potential of Tilapia rendalli at three different stocking densities, using different rearing facilities. T. rendalli fry of 0.9±0.1g average weight were stocked in tanks and hapa-in-ponds at the stocking density of 30, 60 and 90 fry/m 3 . Locally made feed (CP-18%) was administered at 5% body weight three times a day for three months. Monthly sampling was conducted to assess growth by measuring weight and length for specific growth rate (SGR), average daily gain (ADG), weight gain (WG), and biomass (BM). The results of the study showed a significantly higher (P 0.05) as well as within the stocking densities (P > 0.05). The results of this study have a significant contribution towards stocking densities as well as rearing facilities used by hatchery operators. It is recommended that hapas mounted in pond fry rearing for T. rendalli fingerling production is most ideal. The results of the present study suggested that production of good quality fingerlings at stocking densities of 30 fry/m 3 must be adopted in the culture of T. rendalli as fish grows faster than the other stocking densities of 60 and 90 fry/m 3 as demonstrated in this study.
Growth parameters and economics of tilapia cage culture using two commercial fish diets
Two commercial aquaculture feed diets available on the Ghanaian market was subjected to daily feeding of Oreochromis niloticus and growth parameters and economic profitability evaluated in a 66.67 m3 cages. The 12 week trial performed using 16,000 fish with mean weight 102.17 ± 3.1 g was sampled, counted and divided equally to four cages. The two test diets (Diet I: Nicoluzzi and Diet II: Rannan) were in duplicate. Mean live weights of fish in trial groups reached 420.23 ± 20.44 g and 408.62 ± 54.31 g for test Diets I and II respectively. Growth data indicated that, the final live weight, average daily weight gain, condition factor showed no significant difference among test diets (p > 0.05). The best FCR of 1.47 was obtained from test Diet I. Specific growth rate also showed similar values. High gross and net yield was recorded for fishes fed with Diet I and could be due to their relatively good growth performance, good feed conversion rate, relatively high survival rate which, in turn, gave high profit index of 1.87. The total feed fed to fish allotted Diet II was high which reflected in the total cost of feed, coupled with the high price of feed per kilo. This increased the cost of production (in Diet II cages) affected the profit index (1.76) generated from the sale of fish although not significant from fish fed Diet I. The results suggest that, both test diets with almost similar crude protein level, is economical and may be recommended for production. However, alternative source of cheap and cost effective feeds needs to be investigated and encourage our local industry in the production of relatively cheaper aquaculture feeds.
CONTINUOUS PRODUCTION OF BLUE‐TYPE CHEESE FLAVOR BY SUBMERGED FERMENTATION OF Penicillium roqueforti
A two-stage continuous process for the production of Blue cheese flavor from lipolyzed milk fat by submerged fermentation of Penicillium roqueforti was developed. In the first stage, P. roqueforti was grown aerobically on a corn-steep liquor/sucrose medium at 25° C, pH 7, aeration rate 1 liter air/min/L medium, and dilution rate 0.05 hr−1. The effluent air and culture over-flow were led to a maturing tank and allowed to age 24 hr. The mycelial culture was then pumped into a second fermentor to which lipolyzed milk fat was also fed continuously. An average 24 hr contact time between mold mycelium and fatty acids was maintained. The fatty acids and perhaps other components of the lipolyzed cream were metabolized by the P. roqueforti mycelium to produce a fluid product with a Blue cheese-type flavor. Small portions of this product were acceptably added to snack and party dips and salad dressings, as a Blue cheese replacement.