Effect of Stocking Density on Growth Performance of Hybrids of Oreochromis niloticus♀ and Oreochromis urolepis urolepis♂ in Saline Water

Fingerlings of Oreochromis niloticus♀ and Oreochromis urolepis urolepis♂ hybrids were reared at stocking densities of control, 5, 10, 15 and 20 fish/m3 at 15 Practical Salinity Units (PSU) in 1m3 plastic tanks for 63 days. They were kept at low, intermediate and high densities respectively. All hybrids were fed on a formulated, balanced diet consisting of 40% crude protein, at a ratio of 5% body weight, twice daily. Low stocking density showed better growth performance in terms of mean weight gain, specific growth rate (SGR), feed conversion ratio (FCR) and survival rate, than intermediate and high stocking densities. SGR, FCR and survival rates did not vary significantly between treatments (p>0.05). Average final weight gain was significantly different between intermediate and high densities (p<0.05), high and low densities, but not in low and intermediate densities. Density was found to have an effect on the growth of the juvenile hybrids, since higher growth was recorded at low stocking densities compared to the intermediate and high densities. Hybrids were 100% male when inspected. The low and intermediate densities are therefore recommended for hybrids aquaculture in brackish water with the latter being suggested due to its higher yield compared to the low stocking density.

The Need of a Structured Tilapia Breeding Program in Tanzania to Enhance Aquaculture Production: A Review

Breeding programs are crucial for boosting productivity and increase sustainability of aquaculture. Over years, Tanzania has witnessed fluctuation in its capture fisheries production from 320,900 to 375, 535 and back to 362,595 metric tonnes in the years 2000, 2005 and 2016, respectively (URT 2016). The declining trend in fish production has made fish supply in the country unstable and conversely, increased the demand for fishes to about 730,000 metric tonnes in 2017. However, the local aquaculture production has not increased accordingly. Tanzania is importing fish mainly from Asia to meet its increased demand. In 2017, a total of 2,055,721 kg of frozen tilapia were imported from China and Mozambique (URT 2017). The introduction of exotic fish species in Tanzania should be carefully managed because introduced species have many negative impacts to the indigenous species. Tanzania should have a moderate scale tilapia breeding program that will produce good quality fingerlings at affordable price for smallholder fish farmers. The availability of reliable good quality fingerlings is key to improve aquaculture production in the country. Among 17 existing hatcheries, only 12 hatcheries are active, however these hatcheries are not performing well due to low investment and technology leading to the production of low quantity and quality fingerlings. The need for a structured sustainable Tilapia breeding program with bio secured and reliable hatcheries to enhance aquaculture production in Tanzania is given in this review.Keywords: Aquaculture, Breeding programs, Nile tilapia, Local strains

Efficacy of Lactobacillus plantarum and Saccharomyces cerevisiae on growth improvement of hybrid Nile and Rufiji tilapia populations

An investigation of the role of Lactobacillus plantarum and Saccharomyces cerevisiae on growth performance of hybrids from Oreochromis niloticus and Oreochromis urolepis urolepis was carried out in plastic tanks at 10 fish/m3 density and a salinity of 25 units. The probiotic treatments were 2, 4 and 6 g/kg feed while the control feed did not include any probiotics. Growth parameters were measured fortnightly and water quality parameters monitored every day. Survival rate and water quality factors revealed non-significant variations (p > 0.05). Final weight differed significantly among the treatments (p < 0.05). Furthermore, Food Conversion Ratio (FCR), Specific Growth Rates (SGR), and weight gain did not differ significantly (p > 0.05) between the control and 2 g/kg treatments. However, the 4 and 6 g/ kg feed treatments showed significant differences (p < 0.05) from the control diet and 2 g/kg for both L. plantarum and S. cerevisiae. The condition factor did not show any significant difference (p > 0.05) among the treatments. Results of this study indicate that increasing the quantity of commercial probiotics in feeds improved growth rates. Condition factor observed in the treatments could be due to the role of the tested probiotics in improving the water quality of tanks. Therefore, probiotics could potentially be used to enhance coastal aquaculture development