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Preliminary results on the ovarian histology of rabbitfish Siganus rivulatus (Forsskal, 1775) in the southern Aegean Sea, Turkey

Engin Serha, Soykan Ozan, Cerim Hasan, Gülşahin Anıl

Oceanological and Hydrobiological Studies

2020

Vol. 49, No. 3

207--214

The study aimed to determine the annual reproductive cycle of Siganus rivulatusfi females based on monthly variation of the gonadosomatic index (GSI) and histological changes in gonads. A total of 240 fish samples were collected monthly from small-scale (trammel nets) and recreational (angling and pot fishery) fishing from Gökova Bay, the southern Aegean Sea, between July 2017 and June 2018. The length and weight of female fish varied from 10.8 to 26.1 cm with a mean length of 18.7 ± 0.2 cm and from 14.98 to 293.42 g with a mean weight of 91.1 ± 2.93 g. GSI values began to increase in May, peaked in June and gradually decreased in July, indicating that the spawning season was early summer. A total of 240 gonads were histologically examined. Granular, pinkish structure of eggs was observed primarily between April and June, which was consistent with the increase in the gonadosomatic index. Post-spawning follicles were determined in July. Values of the gonadosomatic index gradually decreased after August and they were minimal between September and November. During this period, ovaries were surrounded by immature oocytes at the chromatin and peri-nucleolus stages. These results revealed that Siganus rivulatusstarted vitellogenesis in April and the gonadosomatic index peaked in June.

Biological studies on juvenile fish of Siganus rivulatus (Forsskal 1775) in Port-Said fishing harbour, Egypt

El-Mor M., El-Etreby S., Sapota M.R.

Oceanological Studies

2002

Vol. 31, No. 3-4

17-30

A total of 999 specimens of Siganus rivulatus were collected from trash catches of small beach seine operating in the Port Said fishing harbour at the entrance of the Suez Canal during the period from January to December 1997. The species constituted 20.1% of the trash catch and about 4 - 5% of the total catch of the gear. The juveniles of S. rivulatus could stay at the nursery grounds from October till April, and be recruited from October till December. The length-weight relationships, as well as the condition factor of the juvenile fish, were studied. The feeding activities were quite high in winter months. From May to September, juveniles of S. rivulatus appear to be exclusively deposit feeders in most months, feeding mainly on algae and molluscs.