Bangladesh: Improving productivity of tilapia in ponds

Bangladesh has about 5 million ha of inland water resources such as rivers, estuaries, natural and manmade reservoirs, ponds and floodplains. The major species cultured are Indian and Chinese carps, tilapia and pangasius. However, in recent years, tilapia production has increased and expanded faster than carps and pangasius. Over the last 15 years, tilapia production increased to approximately 200,000 tonnes per annum, according to the Department of Fisheries (2014).

 

The increase in production and rapid expansion were achieved as a result of the successful adaptation of technology, such as high yielding all male seed, intensification, faster growth, and better profitability in culturing tilapia compared to other species. In Bangladesh, pond culture is the most common method for rearing tilapia. However, tilapia is often farmed in polyculture with Indian carp, Chinese carp and pangasius. This approach provides additional yields, better feed management and utilisation of natural productivity. The constraints include: disease and mortality caused by pathogens such as Streptococcus; ectoparasites; inappropriate health management protocols for antibiotic application for treatment and prevention of disease (Komar, 2008); higher feed costs; and low farm gate prices.

 

 

Tilapia farmers are looking for further improvement of rearing conditions to increase yields per unit area, prevent disease and mortality, reduce feed cost and increase average body weights at harvest. With rising production costs in China, tilapia farmers in Bangladesh see an opportunity to be the cheapest producers of farmed tilapia, alongside Vietnam.

 

The objectives of this study were to assess the impact of two types of probiotics and a formulation of natural plant extracts to prevent disease and to improve growth and yields in tilapia pond culture.

 

 

The study was conducted at K.K. Dairy, Poultry and Fisheries Ltd., located at Muhuri Irrigation project, Mirsharai, Chittagong, Bangladesh (commonly known as Meridian Tilapia hatchery and farm) between March and November 2014. The farm size is approximately 32 ha. It includes a hatchery producing all male tilapia, carp and pangasius, as well as 70 culture ponds. The annual production of fish at the farm is approximately 400 tonnes of tilapia, pangasius and carps at the ratio of 70:20:10. It produced 30 million all male tilapia fry, 3 million pangasius fingerlings and 20 kg of carp hatchlings.

 

In this study, we used two 0.3 ha ponds for nursery culture. All male tilapia fry from the same batch were stocked in nursery ponds at a stocking density of 60 fry/m2 for 30-70 days. Nursery ponds were treated with the probiotic Sanolife PRO-W. The application rate at pre-stocking and post stocking application was 200 g per ha fortnightly. At the end of the nursing period, tilapia fingerlings of average body weight (ABW) of 3-10 g were stocked in grow out ponds at a density of 5 fingerlings/m2. In addition, Indian and Chinese carps (catla, rohu, mrigal, silvercarp), and pangasius were stocked at a density of 0.5 fish/m2. In total, 11 grow out ponds (2 control and 9 treatment ponds) were used in this trial. Pond sizes ranged between 0.2 and 0.8 ha. Total pond water area was 5.3 ha.

 

There were three treatments in this study. Treatment 1 used only Sanolife PRO-W. Treatment 2 used a combination of Sanolife PRO-W and PRO-F. Treatment 3 was a combination of Sanolife PRO-W and Sanolife GUT, an antimicrobial compound. All products are from INVE Aquaculture (Belgium). Each treatment was carried out in triplicate.

 

Sanolife PRO-W is a microbial water conditioner. It comprises strains of Bacillus subtilis and B. licheniformis with a minimum concentration of 5 x 1010 CFU/g. Sanolife PRO-F is a mixture of probiotic delivered with feed. It comprises strains of B. subtilis, B. licheniformis and B. pumilus with a minimum concentration of 1 x 1010 CFU/g. The application rate was 2 g per kg of feed. Sanolife GUT is a formulation with selected plant extracts and medium chain fatty acids. It is applied with feed at a rate of 2 g per kg of feed. Probiotics or antimicrobial compounds were not applied in control ponds.

 

Fish were fed commercial feed (Quality Feed Ltd., and CP Bangladesh Ltd.). Powder feed was used for the nursery diet while sinking and floating pellets were used for the grow-out ponds. Crude protein composition ranged from 26% to 32% in these feeds. The feeding rate was adjusted in 10 day intervals according to calculated total biomass from the average body weight (ABW) and the estimated survival rate. Feeding rate followed the size range of tilapia (Table 1). Floating feed was supplemented with sinking pellets after the tilapia ABW reached more than 50 g. Fish were fed two rations per day.

 

 

In two nursery ponds, tilapia fry did not show any signs of disease and mortality. Survival rates were 70% and 80%, a significant achievement compared to previous production data of that farm.

 

Tilapia in the grow-out ponds treated with Sanolife PRO-W and those fed a feed mixed with Sanolife PRO-F did not show any signs of disease. Major mortality did not occur in those ponds. However, in one control pond, there was an emergency harvest due to disease and mortality. In another pond (Sanolife PRO-W and Sanolife GUT), there were signs of disease on several occasions, but these sporadic mortalities did not require an emergency harvest. This clearly showed the benefit of the combined application of selected probiotics as a water conditioner and as feed additives to increase tilapia production.

 

The addition of Bacillus probiotics or the natural plant extract formulation in feed increased the ABW by 40-50 g (Figure 1). Probiotics in the water (Sanolife PRO-W) and or in the feed (Sanolife PRO-F) reduced FCR from 1.5 to 1.2 (Figure 2). Better yield was found in all treatments (probiotics in water, feed mixed with probiotics or plant extract formulation) than the control. The maximum yield reached approximately 13.0 tonnes/ha in 180 days in ponds treated with probiotics in water and mixed with feed. In 2012 and 2013, the average production in those ponds was only 9.0 tonnes/ha in the same period of year.

 

The average farm gate price for 180-200 g tilapia decreased from USD 1.65/kg in 2013 to USD 1.38/kg in 2014. At the same time, the feed cost increased from USD 0.45/kg to USD 0.58/kg. These changes have put more pressure on tilapia producers to improve the production efficiency, such as yield, growth rate and FCR.

 

1. DoF, 2014. Fisheries Statistical Year Book of Bangladesh. Department of Fisheries. Government of Bangladesh, 52 pp. Komar, C. 2008. Disease management in Tilapia. Global Aquaculture Advocate. 77-79 p.