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Spawning Behaviour and Induced Breeding of an Estuarine Catfish, Mystus Gulio (ham.)

M.J. Alam
Bangladesh Fisheries Research Institute Brackishwater Station, Paikgacha, Khulna 9280, Bangladesh

M. Begum
Bangladesh Fisheries Research Institute Brackishwater Station, Paikgacha, Khulna 9280, Bangladesh

M.A. Islam
Bangladesh Fisheries Research Institute Brackishwater Station, Paikgacha, Khulna 9280, Bangladesh

H.K. Pal
Bangladesh Fisheries Research Institute Brackishwater Station, Paikgacha, Khulna 9280, Bangladesh

Abstract/ Executive Summary:

Spawning behaviour of hormone induced estuarine catfish, Mystus gulo was observed in captive condition. Spawning activities that include pairing, chasing and resting, nudging, and twisting, started about 5 hours post injection and ended with release of eggs within 1-2 hours of courtship. Three different dosages of "ovaprim" (1 ml/kg, 1.5 ml/kg, and 2 ml/kg in a single dose) were used in induced breeding of M gulio. The latency period was less (6-7 hours) with the dose of 1.5 and 2 ml/kg, while it was more (7-8 hours) with that of 1 ml/kg. However, all females spawned successfully with each of three different dosages, without any significant differences in the rate of fertilization and hatching. Eggs under all hormone dosages hatched between 18-20 hours after spawning. The hatching rate with 1, 1.5, and 2 ml/kg varied from 71.3-72.7%, corresponding to the fertilization rate of 80.7-84.7%.

Keywords: Spawning behaviour, Breeding, M. gulio

Location: Brackishwater Station of the Bangladesh Fisheries Research Institute (BFRI), Paikgacha, Khulna

Start Date:

End Date:

Program Area: Variety and Species

Commodity: Cat fish

Objectives:

To observe the spawning behaviour of hormone inducted M. gulio in captivity and find out the effects of different doses of hormone on induced breeding.

Methodology:

The study was carried out during June-July 2006 at the Brackishwater Station of the Bangladesh Fisheries Research Institute (BFRI), Paikgacha, Khulna, Bangladesh. Fish & experimental vessel Live gravid females and ripe males of M. gulio were collected from local traditional shrimp ghers in June 2006. The matured males and females were selected on the basis of their morphological criteria. The gravid female has genital papillae of round reddish pink with thick muscular ring, while ripe male has that of conical and protruded muscular. The fishes were kept in an indoor rectangular concrete tank ( 4.45 m x 1.45 m x 1.0 m), which contained gravel-sand filtered pond water of 10%0 salinity, and acclimatized for a period of 24 hours. No feed was given to the broods during conditioning. While the spawning behaviour of hormone inducted M. gulio was observed in a single nylon net hapa, the experiment on induced breeding under different hormone doses was conducted in 9 glass nylon hapas (120 cm x 90 cm x 90 cm). The hapas were set into three rectangular concrete tanks (4.45 m x 1.45 m x 1.0 m) in the hatchery building of the station. Each tank had water inlet-outlet system with connection to an overhead water tank, containing brackishwater that has been pumped from the reservoir pond and passed through a gravel-sand filter. A little amount of water was continuously exchanged using the inlet-outlet system. One water shower was also set over each hapa. Gentle aeration was provided with each hapa using portable electric aerator. Spawning behaviour: To observe the spawning behaviour, 5 females and 10 males were injected with a synthetic hormone, "ovaprim" at the rate of 2 ml kg- 1 body weight and placed into a glass nylon ha pa. The observation of spawning behaviour was carried out since the pushing of injection and continued until the fish were gone in resting after the release of eggs. Hormone doses and injection: A synthetic gonadotropin realising hormone analogue (SGnRH) named 'ovaprim' (Syndel Lab. Ltd., Vancouver, Canada) was used in induced breeding of M. gulio. Three different doses of 1 ml/kg, 1.5 ml/kg, and 2.0 ml/kg of body weight were tested. Each of the hormone doses was considered as treatment and had three replications. In case of both male and female, a singe dose of hormone was injected in deep muscle at the base of dorsal fin. Two males and one female fish, injected with particular test hormone dose, were released into a separate glass nylon hapa, preset in the concrete tanks. Spawning, fertilization and larval rearing: After 5 hours since the first spawning, spent fishes were removed from the spawning hapas. The eggs were non-floating and remained stick to the wall and bottom of the hapa. To estimate the ovulation success, spent females were stripped and the females, from which there was no egg to come out, were considered fully ovulated. In case of any egg to come out, the spent female fishes were dissected and eggs retaining in the abdomen were counted. The number of unreleased eggs was used to calculate the number of egg released, taking into account the relative fecundity of 740 eggs/gm body weight of the species in the month of June (Momtaz, unpublished data). A total of 100 eggs from each hapa were transferred into a bucket and classified as fertilized or unfertilized under a binocular microscope. The fertilization rate was calculated as the number of fertilized eggs divided by the total sampled number (n = 100) of eggs. All newly hatched larvae from each hapa were collected into a bucket containing 10 litres of brackishwater and the hatching percentage was estimated by random volumetric sampling and counting. Meanwhile the hapas were cleaned, disinfected using potassium permanganate solution, and hatchlings were transferred again into the respective hapa. When about 80% of hatchlings were observed with their absorbed yolk sac, feeding was started with boiled and screened hen's egg yolk. The feeding in hapa continued for 5 days and the larvae were collected from hapas. At least five samples of larvae in a 10 ml volume were counted directly, made an average, and total number of larvae in each treatment was estimated. Larval rearing: Newly hatched larvae were collected and transferred to 'new hapas in the concrete tank, as used in case of breeding trials. The larvae were reared for a period of five days. Larvae were fed with boiled and screened hen's egg yolk. Length (n = 10) and weight (n = 50) of larvae were estimated everyday using measuring scale and high precision (±0.001g) digital balance, respectively. Data analysis: Data were analyzed using one-way ANOVA following the Duncan's Multiple Range Test for any significant differences among the treatments. The analysis was done by using a PC package 'STATGRAPHICS Ver. 7. Arc sin values were used, wherever necessary, to stabilize extreme variances in the percentage data.

Source of Information: Bangladesh j. Fish. Res., 10(2), 2006: 101-109

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Eggs under all hormone dosages hatched between 18-20 hours after spawning. The hatching rate with 1, 1.5, and 2 ml/kg varied from 71.3-72.7%, corresponding to the fertilization rate of 80.7-84.7%.

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