Growth and maturity of the lesser-spotted dogfish Scyliorhinus canicula (Linnaeus, 1758) in the southern Portuguese continental coast.

Growth and reproductive parameters were estimated for Scyliorhinus canicula from the south-western Portuguese coast. The sample consisted of 148 specimens with total length ranging from 187 to 580 mm (82 males and 66 females). Maximum ages assigned to males and females were 12 and 13 years, respectively. Linf and k were estimated as 63.6 cm and 0.16 year-1 for males and 63.2 and 0.15 year-1 for females. Length and age at first maturity were estimated as 42.6 cm and 6 years for males and 44.5 cm and 7 years for females.

Identification of potential essential fish habitats for skates based on fishers' knowledge.

Understanding of spatio-temporal patterns of sensitive fish species such as skates (Rajidae) is essential for implementation of conservation measures. With insufficient survey data available for these species in Portuguese Continental waters, this study shows that fishery-dependent data associated with fishers' knowledge can be used to identify potential Essential Fish Habitats (EFH) for seven skate species. Sites with similar geomorphology were associated with the occurrence of juveniles and/or adults of the same group of species. For example, sites deeper than 100 m with soft sediment include predominantly adults of Raja clavata, and are the habitat for egg deposition of this species. Raja undulata and R. microocellata are the more coastal species, preferring sand or gravel habitats, while coastal areas with rocks and sand seabed are potential nursery areas for R. brachyura, R. montagui and R. clavata. The main output of this study is the identification of preferential fishing sites enclosing potential EFH for some species, associated with egg-laying and nursery grounds. The location of these areas will be considered for future seasonal closures, and studies will be conducted to evaluate the biological and socio-economic impacts of such measures. As in the past, fishermen will collaborate in the process of evaluating those impacts, since they have practical and applied knowledge that is extremely valuable for evaluating the advantages and disadvantages of such closures. In conclusion, this study is a first contribution to the understanding and identification of EFH for skate species, associated with nursery and egg deposition sites, with direct application to management.

Dataset of the complete mitogenome of the deep-sea sailfin roughshark, Oxynotus paradoxus Frade, 1929.

Chondrichthyans comprise a diverse group of vertebrate species with extraordinary ecological relevance. Yet, multiple members of this evolutionary lineage are associated with significant extinction risk. The sailfin roughshark Oxynotus paradoxus is a deep-water benthic shark currently listed as vulnerable due to population declines in parts of its range. Here we provide the first complete mitochondrial genome of O. paradoxus, comprising also the first record for the genus and family Oxynotidae. These data can facilitate future monitoring of the genetic diversity in this and related species. Genomic DNA was extracted from O. paradoxus collected in the eastern North Atlantic off western Portugal (37.59°N, 9.51°W) and sent for Illumina Paired-End (2 × 150 bp) library construction and whole genome sequencing on a Novaseq6000 platform. Trimmomatic (version 0.38) was used to remove adapters and MitoZ (version 3.4) to assemble and annotate the mitogenome. This mitogenome with 17 100 bp has a total of 38 genes, 13 of which are protein-coding genes, 23 transfer RNA genes, and 2 ribosomal RNA genes. Eight transfer RNAs and 1 protein-coding gene (NADH dehydrogenase subunit 6, NAD6) are in the complementary strand. In the provided phylogenetic inference, with all available and verified Squalomorphii mitogenomes, the four orders are well separated, and as expected, O. paradoxus is placed in the Squaliformes order. This data reinforces the need for more genomic resources for the Oxynotidae family.

Genetic population structure of the Blackspot seabream (Pagellus bogaraveo): contribution of mtDNA control region to fisheries management.

Marine fisheries management models have traditionally considered biological parameters and geopolitical boundaries. The result is the existence of fisheries management units that do not match genetic populations. However, this panorama is changing with the contribution of genetic and genomic data. Pagellus bogaraveo is a commercially important sparid in the northeast Atlantic, with three stock components being considered by ICES: the Celtic Sea and Bay of Biscay, Atlantic Iberian waters and the Azores. The northern stock collapsed (1975-1985) and is essential to characterize the genetic makeup of the species, particularly in the Iberian Peninsula, where it is managed as a single stock. The mitochondrial control region was used to screen the intraspecific diversity and population structure of individuals from six locations across the species range. The genetic diversity found is similar among sites, and there is differentiation between the Azores and the remaining locations.

Assessing spatio-temporal changes in marine communities along the Portuguese continental shelf and upper slope based on 25 years of bottom trawl surveys.

The Portuguese continental coast is influenced by several oceanographic processes and is located near the confluence of three biogeographic realms (from the North Atlantic, South Atlantic and Mediterranean). Given these features, the topography of the Portuguese coast, possible variations in fishing effort and reported increasing sea surface temperature in the last decades, we hypothesized that changes in marine communities in space and time occurred since 1990. In this study, research survey data collected yearly along the Portuguese continental slope (20-500 m deep) from 1990 to 2016 were analysed with the objective of identifying spatio-temporal changes. Latitude and depth were found to play a major role in communities' spatial differentiation, probably associated to temperature, and three ecological areas were defined (north, southwest and south). In the studied period, Macroramphosus spp. abundance showed a marked decrease in all areas whereas Sparids increased in abundance in the south. Despite these major changes and fluctuations in species abundance over time no major trends in communities were observed. Fishing activity, environmental conditions (including climate change) and biotic factors are all drivers possibly responsible for those changes.

A global perspective on the trophic geography of sharks.

Sharks are a diverse group of mobile predators that forage across varied spatial scales and have the potential to influence food web dynamics. The ecological consequences of recent declines in shark biomass may extend across broader geographic ranges if shark taxa display common behavioural traits. By tracking the original site of photosynthetic fixation of carbon atoms that were ultimately assimilated into muscle tissues of 5,394 sharks from 114 species, we identify globally consistent biogeographic traits in trophic interactions between sharks found in different habitats. We show that populations of shelf-dwelling sharks derive a substantial proportion of their carbon from regional pelagic sources, but contain individuals that forage within additional isotopically diverse local food webs, such as those supported by terrestrial plant sources, benthic production and macrophytes. In contrast, oceanic sharks seem to use carbon derived from between 30° and 50° of latitude. Global-scale compilations of stable isotope data combined with biogeochemical modelling generate hypotheses regarding animal behaviours that can be tested with other methodological approaches.