Browsing by Author "Gordo, Leonel Serrano"
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- Fecundity and sex steroid profile in boarfish Capros aperPublication . Sequeira, Vera; Couto, Elsa; Neves, Ana; Vieira, Ana Rita; Canario, Adelino; Gordo, Leonel SerranoThe boarfish Capros aper is one of the most commonly discarded non-commercial species in the International Council for the Exploration of the Sea (ICES) Subdivision VIII in the Atlantic. An increasing interest in this fishery and an incomplete knowledge on the status of the stock justified the present investigation focused on the determination of fecundity type and its estimation, supported by sex steroid profiles for 17 beta-oestradiol (E2), 11-ketotestosterone and 17,20 beta-dihydroxypregn-4-en-3-one (17,20 beta-P). C. aper was found to have indeterminate fecundity with a mean relative batch fecundity during the spawning peak of 50 oocytes g(-1) eviscerated weight (W-E) and a mean relative annual fecundity of 4020 oocytes g(-1) W-E. E2 variations throughout the year indicated the existence of at least two important spawning events, one in winter (January-February) and the other in summer (June-August), with concentrations in females increasing from those with growing oocytes in the developing phase to those in the spawning capable phase. Higher E2 concentrations were also found from 2000 to 2400 hours and from 0800 to 1200 hours suggesting more intense vitellogenesis activity during the night and in the morning, in contrast to 17,20 beta-P concentrations, which were higher between 1200 and 2000 hours, suggesting a more intense spawning activity during this period.
- The use of caudal thorns for ageing Raja undulata from the Portuguese continental shelf, with comments on its reproductive cyclePublication . Moura, Teresa; Figueiredo, Ivone; Farias, Inês; Serra-Pereira, Bárbara; Coelho, Rui; Erzini, Karim; Neves, Ana; Gordo, Leonel SerranoThe present study focuses on age estimation, with reproductive information contributing to the better understanding of the growth and the biology of Raja undulata. In the age and growth study, two calcified structures were used: caudal thorns and central vertebra. Results of readings showed that there were no significant differences in age estimates between the two structures. Both von Bertalanffy and Gompertz growth models were fitted to size-at-age data by sex and geographical area. No significant differences were found between sexes for the two models but significant differences were found between geographical areas ( P = 0.05). The Gompertz growth function was selected as the best model to describe R. undulata growth because it presented the best fit and the most reasonable biological estimates. Reproductive analysis indicates one annual breeding season for R. undulata. The differences found in the estimates of length at first maturity between geographical areas (TL50% = 838 mm in Peniche and 762 mm in Algarve for females and TL50% = 781 mm in Peniche and 736 mm in Algarve for males), together with the regional differences found between growth parameters estimates ( P = 0.05), may reflect the existence of different local populations of R. undulata on the Portuguese continental shelf.