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Determination of Spawning Seasons of 15 Commercial Fishes of Coastal Waters and the Bay of Bengal

N. G. DAS
Institute of Marine Science and Fisheries, Chittagong University, Chittagong

Abstract/ Executive Summary:

Fifteen commercially important estuarine and marine fishes were selected for the study of maturity, gonado-somatic index (GSI) and fecundity for the determination of their spawning season. Most of the fishes spawned during the post monsoon period extending from November - December up to April - May when salinity attained 30%₀₀and spawning period was confirmed by their GSI value and state of ova.

Keywords: Spawning season, Bay of Bengal, GSI, Fecundity

Location: Chittagong, Cox's Bazar and Teknaf

Start Date: 01-11-1999

End Date: 31-10-2000

Program Area: Resource Development and Management

Commodity:

Objectives:

To identify the spawning pattern of the most commercial fishes that may help to perform artificial breeding and culture practices including hatchery installation and coastal aquaculture. The results are also required for prescribing the minimum mesh size of the fishing gears used

Methodology:

The present study includes the data on spawning season, body length, weight, gonad weight and fecundity of 15 marine fishes of the coastal and offshore water of Bangladesh. The fish samples were collected twice a month during full and new moon from November, 1999 to October, 2000 at different coastal landing centres of Chittagong, Cox's Bazar and Teknaf. Commonly available fishes were collected and only ripe fishes were selected for the study of sexual maturity along with length and weight measurements, length and weight of gonads, estimation of fecundity and gonado-somatic Index (GSI). Specimens were measured by a cm tape after removing excess moisture by blotting paper and weighted (g) by a digital balance. After dissecting out the two lobes of each ovary the same procedure was used for length and weight measurements. Fecundity was estimated by gravimetric method (Lagler 1956). Six cross sectional samples, each weighting 0.1 g, were removed along with the accompanying tissues from the anterior, central and posterior region of the two lobes of ovaries. Total number of eggs in each of the six samples were counted. The total numbers of eggs for each fish were calculated from the sample mean and the total weight of the ovary. The gonado somatic index (GSI) i.e., the percentage ratio of gonad weight to body weight was calculated (Lagler 1956). Place and time of collection of fish were also recorded. From GSI the spawning season and its duration were determined for each species of fish.

Source of Information: J. Asiat. Soc. Bangladesh, Sci., 34(2): 129-135, December 2008

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

From the study of 15 commercial fishes, it may be concluded that the spawning occurred through out the year round in the near-shore and offshore waters of the Bay of Bengal. Most of the fishes behaved spawned during the post monsoon period extending from November - December up to April - May when the salinity range was very high up to 30 - 32%₀. The fishes, Sillago domina and Coilia dussumierii were found to be double breeders in a year. The prolonged spawning activity was recorded in three fishes, Eleutheronema tetradactylum, Polynemus paradiseus and Setipinna taty. The short breeding record was only observed in the migratory fish, Lates calcarifer during pre monsoon where as Tenualosa ilisha spawned both in the pre-monsoon and monsoon period. Mugilids, i.e, Mugil cephalus and Liza subviridis were found to their spawning response during the winter months of December to February.

Knowledge Management: Journal