Feeding habits of the two-banded sea bream (Diplodus vulgaris) and the black sea bream (Spondyliosoma gantharus) (Sparidae) from the south-west coast of Portugal

The stomach contents of Diplodus vulgaris and Spondyliosoma cantharus were: analysed using three simple methods (numeric, gravimetric and frequency of occurrence) and a composite index (I.R.I - Index of Relative Importance). To compare the species, the Schoener index was used. The diet of D. vulgaris consisted mainly of ophiuroids, polychaetes, amphipods and echinoids, while polychaetes, amphipods and hydrozoans dominated in the case of S. cantharus. There were some size-related differences in S. cantharus feeding. Diet overlap was relatively slight, with significant differences in feeding between the two species, notably in terms of greater consumption of echinoderms by D. vulgaris and hydrozoans by S. cantharus. As is the case for the majority of sea breams, D. vulgaris and S. cantharus are characterised by a diverse diet in terms of prey reflecting available prey items in their environment.

Genetic differentiation among Parastichopus regalis populations in the Western Mediterranean Sea: potential effects from its fishery and current connectivity

Parastichopus regalis (Cuvier, 1817) is the most expensive seafood product on the Catalonian market (NE Spain), with prices at approximately 130 €/Kg (fresh weight). Despite its ecological and economic importance, biological and genetic information on this sea cucumber species is scarce. Here, we provide both the first insight on the genetic structure of P. regalis using sequences of cytochrome oxidase I (COI) and 16S genes and a morphological description of its population. Individual sea cucumbers were collected in six locations along the Spanish Mediterranean coast, including an area under fishery pressure (Catalonia). We found high haplotype diversity and low nucleotide diversity for both genes, with higher levels of genetic diversity observed in the COI gene. The population pairwise fixation index (FST), AMOVA and correspondence analysis (CA) based on the COI gene revealed significant genetic differentiation among some locations. However, further analysis using nuclear markers (e.g., microsatellites) is necessary to corroborate these results. Moreover, the genetic and morphological data may indicate fishery effects on the Catalonian population with a decrease in the size and weight averages and lower genetic diversity compared with locations that lack fishery pressure. For the appropriate management of this species, we suggest the following: 1) accurately assessing the stock status along the Spanish coasts; 2) studying the reproductive cycle of this target species and the establishment of a closed fishery season according to the reproductive cycle; and 3) establishing protected areas (i.e., not take zones) to conserve healthy populations and favour recruitment in the nearby areas.

The reproductive biology of the two-banded sea bream (Diplodus vulgaris) from the southwest coast of Portugal

The study of the reproduction of Diplodus vulgaris (Geoff.) as part of a base-line study of the fishery resources of the southwest coast of Portugal, was based on the analysis of the spawning season, gonad maturation, size at maturity, fecundity and hermaphroditism. The spawning season is relatively long, from December to March, with peaks in January and February. No significant differences were found either in the sex ratio (M:F = 1.01) over the year or by size. The size at first maturity (L-50) for all sexes and undetermined individuals combined was 18.33 cm total length (TL), with no significant differences between males and females. The estimated L-50 is considerably greater than the minimum legal size in Portugal of 15.0 cm. Mean absolute fecundity (F-a) was 131 127 oocytes, ranging from 31 523 to 250 608. The relationship between absolute fecundity and total length (TL) (F-a = 25 398 TL-484 426) and somatic weight (SW) (F-a = 878.8SW-71 416) was of the linear type. The mean number of oocytes per gram of somatic weight was 526, ranging from 194 to 887. The reproductive strategy of this species is characterized by a rudimentary hermaphroditism with possible protandry, as evidenced by the existence of individuals in sexual transition.