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Induced Breeding of Endangered Spiny Eel (mastacembelus Armatus) Using Pg Extract

MR Ali
Bangladesh Water Development Board, Dhaka, Bangladesh

MFA Mollah
Department of Fisheries Biology and Genetics, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

MRI Sarder
Department of Fisheries Biology and Genetics, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Abstract/ Executive Summary:

Mastacembelus armatus is an important freshwater spiny eel of Bangladesh. The experiment was initiated to establish an induced breeding technique of the species with two induced breeding trials. In trial I, four different doses viz. 20, 40, 60 and 80 mg PGkg^-1 body weight of the fish were used to standardize the PG dose to ovulate the female M. armatus, and in trial II, the best dose identified in trial I was injected to fish once (whole dose) or twice with divided dose of PG at the rate of 30% and 70% at 6h interval to observe the effect of the mode of hormonal injection. Among the four doses applied in trial I, best result was obtained from 40 mg PGkg^-1 body weight in respect of ovulation rate (100%) of females and fertilization (93.00±2.00%) and hatching rates (58.30±3.50%) of eggs. In trial II, the females treated once (with the whole dose) or twice with divided dose of PG equally responded and no significant difference (p>0.05) was observed between the modes of hormone injection in respect of ovulation rate of females and fertilization and hatching rates of eggs. As M. armatus is considered as endangered fish, this induced breeding technique will help to conserve the fish as well as to produce seed in commercial hatcheries.

Keywords: Mastacembelus armatus,Induced breeding, Eel

Location: Mithamoin haor of Kishoreganj district of Bangladesh

Start Date:

End Date:

Program Area: Variety and Species

Commodity: Eel

Objectives:

This study was performed to build up an appropriate induced breeding technique of M. armatus that will help saving it from the present state of endangered situation and as such the biodiversity of this endangered fish will be saved.

Methodology:

The experimental fish: The fish were collected from the Mithamoin haor of Kishoreganj district of Bangladesh and stocked in indoor cistern for domestication. The cisterns are of 2.33m × 1.34m in size each having the water exchange and aeration facilities. Special shelter of 0.91m long PVC pipe having a diameter of 10 cm for breeding purposes was also provided in the cistern. The fish attained sexual maturity at the size of 32 cm (total length) for female and 34 cm for male both after their second year of life. The brood fish were fed with trash fish at the rate of 3 to 5% of body weight. Since the fish are nocturnal the feed was provided in the early morning and in the evening near the shelter made for the fish. Selection of brood fish: Good looking and healthy broods were collected from the domesticating cistern and subsequently selected for breeding. Male and female broods were identified considering some external appearances. The females having swollen abdomen and round and swollen urogenital papillae were selected as probable broods. However, the mature males had their flat abdomens and long protruded genital papillae. Conditioning of brood fish: Selected brood fish were weighed and kept in cistern to inject with PG extract. Separate cisterns having continuous water supply and aeration facilities were used for conditioning male and female broods. Experimental procedure- Two trials were given to optimize the PG dose. Trial I-Four treatments such as TI, TII_, TIII and TIV each having three females were used. The females under each treatment were indicated as R₁, R₂ and R₃ and kept separately in cistern. Each female under TI, TII, TIII and TIV was treated with PG dose of 20, 40, 60 and 80 mg kg^-1 body weight, respectively. Two males were employed for each female and in total 12 females and 24 males were used in this trial. Trial II-In this trial two treatments i.e., TI and TII each having 6 females were used. The females were treated with PG at the dose of 40 mg kg^-1 body weight. Six females of TI received the whole dose at a time. On the contrary, the dose was divided into two equals and administered to each of the 6 females of TII 6h apart. Induction of ovulation-Source of pituitary gland (PG) and preparation of PG extract: For induction of ovulation, PG extract prepared from commercially available dry carp pituitary glands (PG, available in the market) was used. Requirement of PG was found out according to the total body weight of broods using the following formula: Weight (mg) of required amount of PG (W_t) = W_bxP_t,Where, W_b represents total body weight (kg) of all the fish to be injected and P_t represents the rate in mg of PG to be injected kg^-1 body weight under a particular treatment. The volume of extract needed was calculated using the following formula: Volume of extract (ml) = W_t x1.0 [W_t = Weight of PG (mg)] Where, 1.0 represents the volume of the extract in ml to be injected kg^-1 body weight. The required amount of PG was weighed and homogenized adding a little amount of distilled water. The homogenate was then taken very carefully in a centrifuge tube. The tissue homogenizer was washed several times by distilled water to ensure the transfer of suspension as much as possible. The suspension was centrifuged for 6 min at 6000 rpm. The clear supernatant on top was taken in a vial and pre-determined volume was obtained by adding distilled water. Injecting the PG extract to fish: Based on the body weight of the gravid female the required volume of extract (1.0mlkg^-1) was taken in a graduated 1.0ml hypodermic syringe. Intramuscular injection was given to the dorsal side of the fish above the lateral line. In trial I, the dose was divided into two volumes (30% and 70%) and the females were injected at 6h interval. In trial II, the whole dose was injected to the females under TI at a time while the dose was divided into two volumes (30% and 70%) and injected to the females under TII at 6h interval. Each male was injected with a dose of 10 mg kg^-1 body weight when 2^nd injection was given to the females. Ovulation, collection of eggs and fertilization with milt: After treatment with PG extract both the males and females of each treatment were released in the same cistern. Close supervision was made during this period for their pairing or courtship behavior. Checking for commencement of ovulation was started after 18 th of first injection by gently pressing their abdomen. Commencement of ovulation was confirmed when a few eggs extruded following a slight pressure on the abdominal region of the female. The ovulated females were immediately stripped and separate fertilization trays or petri dishes were used for incubation of eggs of each fish. Milt from males were also stripped out for fertilizing the eggs. If the milt is unavailable through stripping, the testes of male had to be dissected out from body cavity and subsequently macerated in 0.85% NaCl solution. The sperm suspension was mixed with eggs by gently stirring with a feather to ensure fertilization while a small amount of water was added to the egg- sperm mixture to have better activation of sperm for effective fertilization of eggs. Excess milt, blood and dirt if any were removed by washing the eggs several times with clean water. Data analysis: Several indices of effectiveness of PG dose were analyzed by Microsoft Excel (MS Excel) computer package as descriptive values such as mean and percentage. Data were analyzed with the aid of the computer software SPSS version 11.5.

Source of Information: Progressive Agriculture 29 (3): 267-275, 2018

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

M. armatus is an endangered fish though it was abundant in natural water bodies few years ago. However, environmental and anthropogenic activities degraded the natural breeding and nursery grounds of the species and made them endangered. Therefore, it is essential to conserve the fish species otherwise, it will be extinct in near future. Development of induced breeding techniques and production of seeds is one of the ways to protect the species. Induced breeding of M. armatus has been possible using pituitary gland extract in this study and the larvae survived. So, this technique can be used to produce seed of the species in hatcheries in commercial scale and it can also be used for breeding of other endangered fish species of the country.

Knowledge Management: Journal