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Feeding Biology of Near Threatened Small Indigenous Species Dhela, Osteobramacotio (hamilton 1822)

H. M. A. K. Rafin
Department of Fisheries Biology and Genetics, Bangladesh Agricultural University, Mymensingh2202, Bangladesh

M. A. Islam
Department of Fisheries Biology and Genetics, Bangladesh Agricultural University, Mymensingh2202, Bangladesh

J. Sifat
Department of Fisheries Biology and Genetics, Bangladesh Agricultural University, Mymensingh2202, Bangladesh

M. K. Fatema
Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh

S. M. N. Nabi
Aquaculture and Agribusiness Freelance Consultant, Dhaka, Bangladesh

M.A. R. Hossain
Department of Fisheries Biology and Genetics, Bangladesh Agricultural University, Mymensingh2202, Bangladesh

Abstract/ Executive Summary:

To get success in culture of any fish species, detail information on food and feeding habit of that particular fishspecies is really crucial. So the present study has been performed toget the information on the food and feeding habit of Osteobrama cotio. A total of 30 Genera of food organisms were identified and recorded from the gut content of O. cotio, where 29 Genera belong to phytoplankton and one belongs to zooplankton. The percentage of food composition recorded from the gut of the fish were: Bacillariophyceae (12.90%), Chlorophyceae (63.82%), Cyanophyceae (11.32%), Euglenophyceae (8.13%), Rhodophyceae(1.57%), Rotifera (1.43%) and Benthos (0.83%). Chlorophyceae was the most preferred food item and benthos was the least preferred food item of the fish. Gut fullness of the fish was the highest during May and June and the lowest in December. The study results suggest, Osteobrama cotio is an omnivorous column feeder with much higher preference for phytoplankton over both zooplankton and benthos. As it is expected that the outcomes of the present study would be useful in the conservation and management of Dhela in the open water and in the domestication in future to pave the way of the aquaculture in captivity of this nutritionally rich threatened small fish of Bangladesh.

Keywords: Osteobramacotio, Food habit, Gut content

Location: The Dhanuriver of Mohanganjupazilla of Netrokona district, Bangladesh

Start Date: 00-12-2017

End Date: 00-10-2018

Program Area: Animal Health and Management

Commodity: Fish

Objectives:

To study the feeding biology of this important but threatened fish species with the expectation that the outcome of the study would contribute to the efficient management of wild stocks of O. cotio and would pave the ways of its domestication.

Methodology:

Fish sample of O. cotio were collected from part of the Dhanuriver of Mohanganjupazilla of Netrokona district once in a month from December 2017 to October 2018 except January 2018 due to unavailability of fish. Fishes are collected randomly with the help of fine meshed seine net in order to ensure all size group of O. cotio population available in the catch.Immediately after collection, the fishes were preserved in 10% formalin in a plastic bottle prevent digestion of food materials and to stop the enzymatic activity of the gut content. Seventeen to twenty one fishes were chosen randomly to study the gut content at each month. The fishes were washed with tape water and soaked with tissue paper. Total Length (TL) and Body Weight (BW) of each fishwere measured to the centimeter for length and gram for body weight.The body cavity of the fishes were carefully openedand the alimentary canal was dissected outand preserved in 10% formalin in a labeled small plastic bottle to analyze gut content. Each gut contents were analyzed separately. Food contents of the guts were taken out and were diluted in 5 ml distilled water using the method adopted by Miah and Siddique (1992) and Dewan et al. (1985). One ml sub sample from 5 ml were transferred by a pipette to a Sedgwick Rafter cell. Ten fields out of 1000 fields of the counting cell were chosen randomly and the total number of plankton found in the 10 fields were counted and multiplied by 500 to get the total number of plankton in the gut. By using a binocular microscope (Olympus BH-2 with phase contrast facilities) all organisms were counted and identified up to genus level. Four methods namely Numerical method, Frequency of occurrence method, Index of fullness method and Points methods were applied for the determination of food items taken by the fish.All the gut contents were analyzed and total number of individuals in each food categories was recorded and wasexpressed as a proportionof total individual of all food categories (Ikusemiju and Olanian 1977, Crisp et al. 1978).Stomach contents were examined and the individual food organisms were sorted and identified to calculate the number of stomach containing one or more individuals of each category. The number of stomachs is then expressed as a percentage of all stomach (Hyslop 1980). An index of fullness of the stomach was recorded irrespective of size of gut of fishto observe the intensity of feeding. The gut was classified as full, three fourth full, half full, one fourth full and empty gut as suggested by Pillay (1952) and 4, 3, 2, 1, and 0 points were allotted to each gut respectively.The food items wereallotted points on the basis of quantity and all the points assigned to different food items were summed up and scaled down to express them in percentage composition of gut content of all the fishes examined (Hynes 1950).

Source of Information: Bangladesh J. Fish. (2019) 31(1) : 77-84

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The result of the gut content analysis of O.cotio showed that the fish feed on variety of food items which were broadly categorized as Phytoplankton, Zooplankton and Benthos. A total of 30genera of food organisms were identified and recorded from the gut content of O. cotio, where 29 genera belonged to phytoplankton, one belonged to zooplankton and the benthic organisms were unidentified. Among the plankton population five groups were phytoplankton which were Bacillariophyceae, Chlorophyceae, Cyanophyceae, Euglenophyceae and Rhodophyceae and one group of zooplankton that was Rotiferafound the gut content of O.cotio. The food organisms recorded from the gut content of O.cotio were presented. December. The study results suggest, Osteobrama cotio is an omnivorous column feeder with much higher preference for phytoplankton over both zooplankton and benthos. As it is expected that the outcomes of the present study would be useful in the conservation and management of Dhela in the open water and in the domestication in future to pave the way of the aquaculture in captivity of this nutritionally rich threatened small fish of Bangladesh.

Knowledge Management: Journal