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Effect of Age on the Recruitment of Oocytes in the Climbing Perch, Anabas Testudineus (bloch)

AHM Shafiullah Habib
Department of Zoology, Jagannath University, Dhaka, Bangladesh.

Baharul Hoque
Department of Zoology, University of Chittagong, Chittagong-4331, Bangladesh.

Abstract/ Executive Summary:

Effect of age on the recruitment of oocytes in Anabas testudineus has been studied. For age determination opercular bones, otoliths and scales were collected from 210 adult females weight ranging between 18.0 g and 135.0 g and length between 8.5 cm and 20.5 cm. The scatter points of opercular bone length, scale length, and otolith length against the fish length showed linear relationships. The high values of coefficient of correlation (r) indicated that all hard parts grew proportionately with the corresponding growth of the fish. The marginal open zone in all hard parts had minimum width during the months of June and July indicating that the age ring might have been formed in the season immediately preceding these months due to spawning. The age rings were annulus in nature since the fish was found to spawn once in a year. Recruitment of oocytes were not affected by the age of the fish. No statistical significant difference was observed between the number of oocytes contained in the ovary of fishes falling into two different groups of the same body length.

Keywords: Anabas testudineus, Opercular bone, Otolith, Scale, Annulus, Age determination, Oocyte recruitment

Location: Chittagong city

Start Date:

End Date:

Program Area: Variety and Species

Commodity: Fish

Objectives:

To find out the influence of age on the manner of recruitment of oocytes in Anabas testudineus.

Methodology:

A total number of 210 adult female A. testudineus with body weight ranging from 18.0 g to 135.0 g and body length from 8.5 cm to 20.5 cm was used. Live fish samples were collected monthly between August ’98 and July ’99 from local markets around Chittagong city. At autopsy firstly the total body lengths and the total body weights were recorded. For age determination opercular bones, otoliths and scales were collected and then cleaned and stored properly. When opercular bones were dry the age rings on the opercular bones, if present, were visible and it was found that these rings were much clearer after some months of storage. The maximum distance between centre and its margin was taken as the length of opercular bone. When opercular bones were viewed against light, contrasting layers of ossification was observed giving the impression of rings between two layers. Age was then estimated by counting the number of rings completed on the opercular bones. Otoliths were removed by a lateral dissection on the head of each fish. Among the otoliths only the largest, the sagitta, was used for age determination. Before examination otoliths were ground finely following the acid contact method. Otoliths were placed in water in a petri dish and light was then transmitted from below through it. When transmitted light is passed through otolith the opaque zones appear a shadowy rings and the hyaline zone as bright light rings. Age was then determined by counting the number of rings in the otoliths. A millimeter scale determined the length of each otolith. The maximum distance between one edge to the other was considered as the length of the otolith and was finely measured with the help of millimeter scale. Four to five scales were collected from below of the lateral line and posterior of the dorsal fin. The maximum distance between the focal point (focus) and the anterior margin of the scale was taken as the radius of the scale. The margins of the scales were observed under a dissecting binocular microscope. Age was determined by counting the completed number of rings found on the scales. Relationship among the hard parts namely opercular bones, otoliths and scales against body length were established statistically through linear regression. Age groups were considered as 0+ (less than one year), 1+ (less than two years), 2+ (less than three years), and so on. Photographic records of the structures used were kept.

Source of Information: Bangladesh J. Zool. 43(1): 27-36, 2015, ISSN: 0304-9027 (Print), 2408-8455 (Online).

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

From the present study on the effect of age on the recruitment of oocytes, it is clear that there is no significant difference in the number of oocytes between two age group of female fish but with same body length.

Knowledge Management: Journal