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Effects of Low-level Salinity on Egg Hatching and Larval Rearing of Tilapia (oreochromis Niloticus)

MAHMUD HASAN
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh

MD. GOLAM RABBANE
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh

MD. MONIRUL SLAM
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh

A.F.M. ARIFUR RAHMAN
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

Two experiments were conducted to evaluate the effects of low-level salinity on hatching of tilapia egg and rearing of early larval stages. The results showed that 6 and 4 ppt salinity have significant (P < 0.05 and P < 0.01) beneficial effect on egg hatching and larval rearing of tilapia.

Keywords: Salinity effect, Hatching, Larval rearing, Tilapia

Location:

Start Date:

End Date:

Program Area: Animal Health and Management

Commodity: Tilapia

Objectives:

To evaluate the effect of low-level salinity on egg hatching of tilapia and
To evaluate it's effect on rearing of tilapia hatchling to fry.

Methodology:

Two sets of experiments were conducted for egg hatching, and hatchling rearing. In the first set, two levels of salinity, for example, 0 and 6 ppt each with three replicates were conducted for five days, because tilapia requires long time holding to hatch out. Experimental units composed of small plastic tray with re circulation in 700 L circular tank for two different treatments. Stocking density was 300 eggs per tray. Air pump was used for continuous aeration to water. For larval rearing experiment , initially six different salinity levels were tested for two weeks and the preliminary results did not show any significant differences among 2, 4, 8 and 10 ppt salinity. Based on the result of preliminary test, five different salinity levels, such as, 0, 3, 4, 6 and 8 ppt each with three replicates were tested further. Th,e experiment was conducted in round 10 L glass jars with static water in November 2002 for 20 days following completely randomized design (CRD) method . Saline water was prepared by mixing common salt with tap water. Unfed hatchlings were collected from AIT hatchery and stocked at 10 hatchlings/L (Commercial practice of AIT) . Fish fed one day after stocking. The feed composed of fish meal powder (FMP) with MT (17 a-methyl testosterone hormone) twice a day at 20 % of their body weight. Everyday 2 L water was exchanged from each jar and the total water volume was changed every week. Water temperature, DO and salinity were measured by using refractometer and DO meter. The systems were aerated by continuous air diffusion using air stone. Batch weight of fish was taken weekly to determine the amount of ration. Survival rate was determined at the end of the experiment to reduce stress.

Source of Information: Dhaka Univ. J. Biol. Sci. 14(1): 91-94, 2005 (January)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Maximum (88.34%) survival rate was recorded in low. level salinity (4 ppt), which was found to be the most effective (P < 0.01) in improving survival rate. Rearing tilapia hatchling at 4 ppt saline water therefore, has potential to improve the current practices.

Knowledge Management: Journal