Aspects of the reproductive biology of Sarpa salpa (Pisces: Sparidae) off the east coast of South Africa

Abstract

The reproductive biology of the sparid fish, Sarpa salpa, was investigated along the east coast of South Africa between January 1994 and March 1995. A protracted winter spawning season was identified, extending from April through to September, and it was evident that S. salpa migrate annually to KwaZulu-Natal from juvenile nursery areas in the Eastern and Western Cape. Size at 50% maturity for male S. salpa was attained at 145 mm fork length, while the adult sex ratio in the shore-based catch was 1:1.6 in favour of males. Frequency distribution by size indicated that males dominated the smaller size classes while females dominated the larger size classes. Histological examination of gonadal development revealed five types of gonads, namely undifferentiated, juvenile, male, intersex, and female gonads. Intersex gonads were characterized by degenerating testicular tissue separated from a dormant ovary by connective tissue. The population demography and the presence of intersexual individuals with degenerating testicular tissue was suggestive of protandrous sex change in S. salpa. This was confirmed during a captive study in which male S. salpa changed sex to female. Group spawning behaviour is postulated based on various morphological and indirect behavioural characteristics.