Reproductive cycle of female Brazilian codling, Urophycis brasiliensis (Kaup 1858), caught off the Uruguayan coast

Abstract

Between August 1993 and September 1995, aspects of reproduction of female Urophycis brasiliensis (Phycidae), a euryhaline species found in the Western Atlantic between 23° and 40° S, were studied. A total of 2500 specimens (23–60 cm; 113–2400 g) were obtained from artisanal fishermen at two locations on the Uruguayan coast: Piriapolis, influenced by the discharge of the Rio de la Plata, and La Paloma, a marine site. The ovaries of 900 fish, analysed according to standard histological techniques, revealed eight maturity stages, including one virgin ovary obtained from the catch of a research vessel. The gonadosomatic index ranged from 0.13 to 8.7. Its maximum was determined in the autumn in La Paloma, whereas a shift towards the winter was observed in Piriapolis. In both capture areas, resting stage 2 was present in the samples throughout the year, reaching 67% of the total. At no time were hydrated ovaries observed. The histological cycle is described and compared with macroscopic features of the female gonad. Maturity stages determined in the field had to be confirmed by histological analysis in order to avoid erroneous classification. Although the two ports are only 150 km apart, data indicate different and extended reproductive periods, between June and December for Piriapolis, and March to May for La Paloma. Data indicate synchronous group spawning, possibly as a reproductive strategy in a highly variable environment. The results are compared with scarce information available on U. brasiliensis in its distribution area and data on other species of the same genus.