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Size Related Feeding Patterns and Electivity Indices of Silver Barb (barbodes Gonionotus Bleeker) from a Pond, Bangladesh

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

M. Sadiqul Islam
Department of Fisheries Biology & Genetics, Bangladesh Agricultural University, Mymensingh

M.K. Rahman
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

S.M. Rahmatullah
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Abstract/ Executive Summary:

The feeding patterns with respect to quality and quantity of food of silver barb, Barbodes gonionotus varied with their size and development. The results indicated that the fish in the size group I (7-25 mm TL) were fairly omnivore with particular liking for rotifera, green and blue-green algae while the size group II (25.1-44 mm TL) and III (44.1-55 mm TL) were omnivore with higher tendency of feeding on debris, aquatic plants, green algae, blue-green algae and rotifera. However, the fish of the size group IV (55.1-80 mm TL) were found to be herbivore with feeding preference for aquatic plants, green and blue-green algae. In all the size groups, debris was the most dominant food item. Feeding preference of the fish showed clear ontogenetic shift. The electivity indices revealed that the fish were selective feeder.

Keywords: Food, Feeding, Electivity index, Barbodes gonionotus

Location: Bangladesh Agricultural University.

Start Date: 00-04-1996

End Date: 00-06-1996

Program Area: Animal Health and Management

Commodity: Fish

Objectives:

To know the feeding habit and the variations in quality and quantity of food taken by different sizes of B. gonionotus

Methodology:

The B. gonionotus for the present study was collected from April to June '96 by a small seine net from a rainfed artificial pond. Samplings were done fortnightly at 9.00 to 10.00 am and a total of 60 fish measuring 7-80 mm in total length (TL) were collected. Immediately after collection, the fish were killed by suffocation and preserved in 10% buffered formalin to prevent further digestion of food and brought to the laboratory and dissected out the gut and put on a labeled vial for further studies. For the study, the total length of fish in millimeter were measured and grouped into four groups according to their size. All fishes were divided into four size groups and was designated as - group I (7-25 mm TL), young; group II (25.1-44 mm TL), juvenile; group III (44.1-55 mm TL), pre-adult and group IV (55.1-80 mm TL), adult. Gut content analysis: The stomach of individual fish was dissected out immediately after sampling and the index of fullness of the stomach was visually recorded irrespective of the size of the stomach or the fish and assigned a score of; 0 for empty, 1.0 for one-fourth, 2.0 for half, 3.0 for three-fourth and 4.0 for full. Then the volume of stomach contents was also assessed visually on an obsolete scale and points were allotted to each stomach according to the volume of its contents. The stomach with largest volume was allotted 100 points, and each of the stomach as examined was then rated in one of the following point categories 0, 3, 6, 12, 25, 50 and 100 points according to volume of the food present. The categories were based on inspection and estimation, but a set of stomachs of all categories were made from extra stomach and was used in relating absolute volumes to assign point values. Stomach with intermediate quantities of food were allotted to the point categories which they closely approach. Then it was diluted with distilled water to 4 ml. One ml sub-sample from 4 ml sample was transferred by a pipette to a Sedgwick-Rafter cell. By using a binocular microscope (Swift, M-4000D), all organisms were counted and each food item was identified to the nearest taxonomic group. Organisms of each taxonomic group were then summed together and points were assigned to the different categories of food according to their respective volume partitioning the total points allotted to the fish. Plankton collection, preservation and enumeration: Water samples were also taken from different areas and depth of the pond to make representative sample of the sampling days and filtered through a fine mesh sealed plankton net. Filtered sample was taken into a plastic bottle and preserved in 5% formalin for further studies. By using a Sedgwick-Rafter cell and a binocular microscope, 1 ml sub-sample was examined for each sample and identification of different food items were done.

Source of Information: Bangladesh J. Fish. Res., 5(2), 2001: 105-114

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The results indicated that the fish in the size group I (7-25 mm TL) were fairly omnivore with particular liking for rotifera, green and blue-green algae while the size group II (25.1-44 mm TL) and III (44.1-55 mm TL) were omnivore with higher tendency of feeding on debris, aquatic plants, green algae, blue-green algae and rotifera. However, the fish of the size group IV (55.1-80 mm TL) were found to be herbivore with feeding preference for aquatic plants, green and blue-green algae. In all the size groups, debris was the most dominant food item. Feeding preference of the fish showed clear ontogenetic shift. The electivity indices revealed that the fish were selective feeder.

Knowledge Management: Journal