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Domestication of an Endangered Fish Species Nandus Nandus (ham.): I. Laboratory Rearing of Young Fish Up to Sexual Maturity

M. Das
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

N. Zamal
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Abstract/ Executive Summary:

An experiment was conducted for rearing of Meni, Nandus nandus in laboratory condition for seven months with the objective to select appropriate feed for the species and to develop a rearing technique of the species up to the stage of sexual maturation. Different trials were conducted using artificial feed (35.5% protein), dead fresh kachki (Carica soborna), dead fresh prawn (Macrobrachium lamarrei) and live prawn (Macrobrachium lamarrei). The provision of bottom sediment did not significantly influence the growth of fish. Between dead fresh kachki and dead fresh prawn, the fish preferred dead fresh prawn. The fish was found to be reluctant to take dead fresh kachki and prawn as food unless they became very hungry. The fish was found actively feeding on live prawn. The FCR of the prawn as food for N. nandus was found to be 2.5. From the study, it was observed that in laboratory rearing N. nandus preferred live prawn as food than artificial feed, dead fresh kachki and dead fresh prawn. The fish fed on live prawn became sexually matured (eggs or white milt extruded by gentle pressure on the abdomen of the fish) in the laboratory at the end of the experiment.

Keywords: Endangered species, Nandus nandus, Laboratory rearing

Location: Bangladesh Agricultural University, Mymensingh.

Start Date: 00-10-1998

End Date: 00-04-1999

Program Area: Resource Development and Management

Commodity: Fish

Objectives:

To select appropriate feed for Meni, Nandus nandus and to develop a rearing technique of the species up to the stage of sexual maturation

Methodology:

The present study was conducted from October'98 to April '99 in the laboratory of the Department of Aquaculture under the Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh. Eight glass aquaria each having size of 60x35x30 cm were used to conduct the experiment. The aquaria were marked as number 1 to 8 for convenience ofthe study. A set of 4 aquaria (1 to 4) was provided with sandy layer. The rest 4 aquaria were of bared bottom. All the aquaria were filled with fresh tap water almost up to the top level. Experimental fish and acclimation: A total of 75 experimental N. nandus of "0" age group were collected from a fish trader which were caught by using bana and scoop net from a beel called Gopadmarchar near by the Bhramaputra river, under Mymensingh Sadar Thana. The fish caught form the beel were kept in a 50 liter aluminum pot and brought alive to the laboratory as early as possible. Fish were placed immediately into the aquaria in the laboratory. Three aerators were fitted to supply oxygen in the aquaria. The fish were treated with 1% salt solution (dip) as a prophylactic treatment. No feed was supplied to the fish on first two days of the experiment. Then the dead kachki (Carica soborna) was supplied as food and the fish were acclimatized for seven days. Stocking density: A total of eight fish were kept in each aquarium. From the collected fish a total of 64 fish were used in this experiment. The average body length and weight of the fish were 6.56 ± 0.62 cm and 4.10 ± 0.88 g respectively. Experiment- I: An experiment with two treatments viz. artificial feed (containing 35.5% protein) and dead fresh fish kachki (C. soborna) were used in two replicate aquaria of two types having sandy bottom and bared bottom. In all the experiments, feed was supplied once a day at morning (9.00 am). Feeding duration was for fifteen minutes every day. During the experiment the water was aerated by using aerators continuously to maintain dissolved oxygen concentration at saturation level. Experiment-II: Following the results of the pt experiment another experiment with two treatments viz. kachki (C. soborna) and dead fresh prawn (Macrobrachium lamarrei) were supplied as food in quadruplicate aquaria for another one month. Feeding time and duration were maintained as per 1st experiment. Rearing: Based on the findings of the 1st and 2nd experiments, which showed that growth of fish was not satisfactory with artificial feed, dead fresh kachki and dead fresh prawn, a four months rearing experiment was conducted by feeding live prawn. In rearing about one third of total water of each of the aquarium were changed in every morning and food (live prawn, 12 in each aquarium) was supplied once a day (9.00am) for fifteen minutes. Uneaten remaining prawn (if any) were removed from the aquarium. Total number of prawn eaten in each aquarium was counted and recorded properly. Any faeces on the bottom of the aquarium was removed by siphoning. Initial individual body weight (g) and total length (cm) and their average were measured and recorded. Monthly sampling was done to record the average body weight (g) and total length (cm) gain. The weight (g) of live prawn fed were also recorded for calculation of FCR. Maturity observation: Impirical observations of body color and body shape of fish were made in order to ascertain sexual maturity fortnightly intervals starting from 1st February'99. Maturity of fish were first perceived by observing the eggs or milt of fish by means of stripping process during the April'99. Dissections of fish were also made in order to know maturation stage and the maximum ripeness of eggs at the mid May'99. Analysis: Statistical analysis of growth data in experiment -I and experiment-II were performed using the two way ANOV A and one way ANOVA respectively by using the programme, Stategraphices (version 7). Moisture content of prawn was determined by following the standard method. The moisture content of the prawn was found to be 75.68%. The FCR (food conversion ratio) of prawn was calculated for N. nandus.

Source of Information: Bangladesh J. Fish. Res., 4(2), 2000:135-140

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

N. nandus preferred live prawn as food than artificial feed, dead fresh kachki and dead fresh prawn. The fish fed on live prawn became sexually matured (eggs or white milt extruded by gentle pressure on the abdomen of the fish) in the laboratory at the end of the experiment.

Knowledge Management: Journal