Using biological variables and reproductive strategy of the undulate ray Raja undulata to evaluate productivity and
B Serra-Pereira1, K Erzini, I Figueiredo
1Instituto Português do Mar e da Atmosfera (IPMA), Departamento do Mar e Recursos Marinhos, Divisão de Modelação e Gestão de Recursos da Pesca, Av. Brasília, 1449-006 Lisboa, Portugal.
Abstract:
The present work provides a detailed analysis of the reproductive strategy of the undulate ray Raja undulata in Portuguese mainland waters. The species was found mostly between 30 and 40 m deep on sandy bottoms. Egg-laying sites were observed in the north, centre and south-west regions, mainly at depths below 30 m. The peak of the reproductive season occurred from December to May. Asynchrony between reproductively active females and males appeared to occur, although most adult males were capable of reproducing throughout the year. The estimated length at 50% maturity was 86·2 cm (8·7 years) and 76·8 cm (7·6 years) total length for females and males, respectively. The maximum potential fecundity was estimated to be 69·8 follicles per female per reproductive season, which are released in 4·7 batches of 15 follicles. The life-history and demographic parameters of R. undulata are similar to those of other skate species, while the potential rate of population increase (0·49) is above the published values for other elasmobranch species. With these new findings, this study makes an important contribution to the understanding of the life history of R. undulata, and provides a first evaluation of the productivity and susceptibility of the species to exploitation.
