Browsing by Author "Vasconcelos, Paulo"
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- Age and growth of a highly successful invasive species: the Manila clam Ruditapes philippinarum (Adams & Reeve, 1850) in the Tagus Estuary (Portugal)Publication . Moura, Paula; Garaulet, Lucia L.; Vasconcelos, Paulo; Chainho, Paula; Costa, Jose Lino; Gaspar, MiguelThe Manila clam Ruditapes philippinarum (Adams & Reeve, 1850) was introduced in several regions worldwide where it is permanently established. In Portuguese waters, the colonisation of the Tagus Estuary by this invasive species coincided with a significant decrease in abundance of the native Ruditapes decussatus (Linnaeus, 1758). This study aimed to estimate the age and growth of the Manila clam, to compare the growth performance between R. philippinarum and R. decussatus in several locations worldwide, and to ascertain whether the Manila clam's growth patterns contributed to the extensive distribution of this invasive bivalve in the Tagus Estuary. The growth of R. philippinarum in the Tagus Estuary was described through the von Bertalanffy equation SLt=65.2[1-e(-0.34(t+0.93))],corresponding to a phi-prime index (phi') of 3.160 and an overall growth performance of 4.974. This growth performance is the second highest recorded for R. philippinarum worldwide and was much higher than that of R. decussatus from Portugal. This study confirmed that the Tagus Estuary presents near-ideal environmental conditions for growth of the Manila clam. R. philippinarum displayed clearly invasive behaviour, spreading widely and growing faster than the native R. decussatus, which certainly contributed to the decline of its populations in the Tagus Estuary.
- Bycatch and discard survival rate in a small-scale bivalve dredge fishery along the Algarve coast (southern Portugal)Publication . Anjos, Mariana; Pereira, Fábio; Vasconcelos, Paulo; Joaquim, Sandra; Matias, Domitília; Erzini, Karim; Gaspar, MiguelAlthough the bivalve dredge used on the Algarve coast (southern Portugal) is highly selective for the target species, in some periods of the year the bycatch can exceed the catch of the commercial species. The present study aimed to quantify the bycatch and discards, estimate damage and mortality, and propose management measures to minimize discards and mortality. A total of 15 fishing surveys (60 tows) were performed using two types of dredges (“DDredge” targeting Donax trunculus and “SDredge” targeting Spisula solida and Chamelea gallina). Of the 85257 individuals (392.4 kg) of 52 taxa that were caught, 73.4% belonged to the target species, 22.1% to commercially undersized target species and 4.5% to bycatch species. Bycatch rates were lower for SDredge (13.5% in number and 6.3% in weight) than for DDredge (46.0% in number and 32.9% in weight). Damage and mortality rates were also lower using SDredge (1.3% and 1.0% of the total catches, respectively) than using DDredge (4.0% and 2.8% of the total catches). Survival experiments revealed the diverse vulnerability of the taxa and confirmed the influence of the damage score on the mortality rate. The results gathered in the present study encourage the adoption of a bycatch reduction device to reduce both direct and indirect mortality.
- Bycatch, discards and survival rates in the small‐scale cuttlefish trap fishery on sandy bottoms off the Algarve coast (southern Portugal)Publication . Vasconcelos, Paulo; Pereira, Fábio; Moreno, Ana; Gaspar, MiguelThis study reports a detailed description of the bycatch, discards and survival rates in the cuttlefish (Sepia officinalis) trap fishery off the Algarve coast (southern Portugal). A total of 86 fishing surveys involving 6,311 cuttlefish traps were performed between May and September from 2009 to 2014. Bycatch species were caught in 1,037 traps (bycatch catchability rate of 16.4%), comprising 1576 individuals with an overall weight of 268.3 kg. During the study period, bycatch CPUEs were 12.5 ind./50 traps and 2.1 kg/50 traps, with bycatch rates of 21.1% by number and 15.9% by weight. Thirty-four species (89.5% of bycatch taxa) were discarded at sea, corresponding to discard rates of 19.5% by number and 11.1% by weight. The short-snouted seahorse, Hippocampus hippocampus (L.), was the third most abundant bycatch species (11.6% No.; 0.4% kg) and the second most discarded (12.6% No.; 0.6% kg), being invariably discarded live and undamaged owing its conservation status. This markedly seasonal small-scale trap fishery constitutes a locally important socio-economic activity during spring and summer, characterised by low bycatch and discard rates, complemented by high survival rates of discards.
- Catches of Sepia officinalis in the small-scale cuttlefish trap fishery off the Algarve coast (southern Portugal)Publication . Pereira, Fábio; Vasconcelos, Paulo; Moreno, Ana; Gaspar, MiguelThe present study reports a detailed description of the catches of cuttlefish (Sepia officinalis) in the trap fishery performed seasonally off the Algarve coast (southern Portugal). A total of 86 fishing surveys were performed during the fishing season (May-September) from 2009 to 2014, on sandy bottoms at bathymetrics ranging from 8 to 10 m depth. During the whole study period, fishing operations involved 6311 cuttlefish traps with a gear catch rate of 37% (frequency of traps with cuttlefish) and a mean of 0.9 S. officinalis caught per trap. A total of 5883 S. officinalis (1424.0 kg) were caught, being only recorded 282 dead individuals (mortality rate of 4.6%). The mean fishing yield (standardised CPUE's in number and weight) was 46.6 individuals and 11.3 kg 50 traps(-1). Overall, males (n = 3188) outnumbered females (n = 2695), producing a significant male-biased (1 M: 0.85 F) sex ratio. On average, females were significantly larger and heavier (124.4 +/- 22.9 mm ML; 253.1 +/- 148.8 g TW) than males (121.9 +/- 24.0 mm ML; 230.7 +/- 143.1 g TW). Accordingly, the length-frequency distributions displayed significant gender differences, with 89.6% of females and 85.8% of males accomplishing the MCRS (100 mm ML). This markedly seasonal, highly sustainable and low impacting small-scale fishery constitutes a locally important socio-economic activity during spring and summer. Undamaged catches and highly fresh individuals further contribute to the considerable price reached by S. officinalis caught using this artisanal fishing gear.
- Cytogenetics of Bolinus brandaris and phylogenetic inferences within the Muricidae (Mollusca: Gastropoda)Publication . Leitao, Alexandra; Vasconcelos, Paulo; Ben-Hamadou, Radhouan; Gaspar, Miguel; Barroso, Carlos M.; Ruano, FranciscoThe purple dye murex, Bolinus brandaris (Linnaeus, 1758), is a muricid gastropod common throughout the Mediterranean and along the Moroccan and Portuguese Atlantic coasts. In the present study, we confirmed the diploid chromosome number of 2n = 70 for this species, and established for the first time the karyotype, which comprised 12 metacentric, 15 submetacentric and eight subtelocentric chromosome pairs. To facilitate cytotaxonomic comparisons, we carried out a comparative karyological analysis through multidimensional scaling between B. brandaris and three other 2n = 70 muricid species (Hexaplex trunculus, Ocenebra erinaceus, and Stramonita haemastoma) for which chromosomal measurements have been previously published. The interpretation of the ideograms and the statistical analysis highlighted the closest similarity of B. brandaris and H. trunculus compared to S. haemastoma and O. erinaceus. Indeed, B. brandaris and H. trunculus showed the smallest dissimilarities both for relative length and arm ratio, with O. erinaceus presenting intermediate values, whereas the highest dissimilarities were found between H. trunculus and S. haemastoma for both data. The karyotypes of B. brandaris and H. trunculus (subfamily Muricinae) presented the highest proportions of metacentric chromosomes compared to the other two muricids analysed, suggesting that those karyotypes could be considered primitive within the 2n = 70 Muricidae studied so far. (C) 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 185-193.
- Development of indices for nonsacrificial sexing of imposex-affected Hexaplex (Trunculariopsis) Trunculus (Gastropoda : Muricidae)Publication . Vasconcelos, Paulo; Gaspar, Miguel; Castro, MargaridaThe muricid Hexaplex (Trunculariopsis) trunculus lacks external sexual dimorphism and is highly affected by imposex, which further complicates its sexual identification. In this context, the aim of this study was to develop sexual indices based on the dimensions of male and imposex-affected female penis, which could constitute a useful, simple and nonsacrificial tool for sexing live specimens of T. trunculus. The adoption of sexual indices consisting of penis dimensions of both sexes relative to individual size revealed a high accuracy in the sexual identification of sacrificed specimens (> 95% correct sexing). Additionally, multivariate discriminant analysis allowed correct sexing of 98.8% of the original 1053 sacrificed individuals, with accurate sexual identification being higher for males (99.5%) than for imposex-affected females (97.7%). An anaesthetization experiment was performed to investigate the effects produced by the anaesthetic (MgCl2) on penis measurements, to test this nonsacrificial approach and to validate the previously developed sexual indices. The anaesthetic provoked an expected enlargement in penis dimensions but, despite this side effect, the sexual indices developed for sacrificed specimens were still highly successful in sexing anaesthetized T. trunculus (generally more than 95% correct sexual identification). The practical application and some limitations of developing and employing this kind of index for the sexual identification of T. trunculus and other imposex-affected gastropod species are discussed.
- First record of the spottail mantis shrimp, Squilla mantis (Stomatopoda, Squillidae), in the Ria Formosa lagoon (Algarve coast, southern Portugal)Publication . Vasconcelos, Paulo; Carvalho, Andre N.; Pilo, David; Gaspar, Miguel; Cristo, Margarida
- Habitat structure shaping megabenthic communities inhabiting subtidal soft bottoms along the Algarve coast (Portugal)Publication . Rufino, Marta M.; Pereira, Alexandre M.; Pereira, Fabio; Moura, Paula; Vasconcelos, Paulo; Gaspar, MiguelThe present study analysed the megabenthic diversity in subtidal soft bottoms and assessed the main environmental drivers of megabenthic community organisation along the Algarve coast (southern Portugal). We tested the hypothesis that megabenthic communities respond to the same environmental drivers than macrofauna. We found that similar to macrofauna, megafaunal communities were organised in relation to the depth of closure, light reaching the bottom, and the hydrodynamic conditions related with exposure within the shallower areas. The influence of the main river outflow prevailed over other drivers, but only up to 9 m depth. We found that seven different spatial units should be considered, each characterised by different indicator species. Additionally, among a total of 412 taxa collected between 4 and 50 m depth, we provide the characteristics of the 64 commonest species in terms of occurrence, frequency, distribution, abundance, bathymetric and sedimentary preferences, which constitutes most valuable information for ecosystem modelling. Megabenthic alpha diversity decreased with depth, contrary to evenness and was higher in the proximity of the river Guadiana and in highly exposed shores. We conclude that the megafauna, which is significantly quicker to collect and analyse, can provide an accurate alternative to macrofauna sampling, as their communities are shaped by the same drivers.
- Hand dredging for the wedge clam (Donax trunculus) in the Algarve coast (southern Portugal): fishing yield, bycatch, discards and damage ratesPublication . Nicolau, Lídia; Vasconcelos, Paulo; Carvalho, André N.; Pereira, Fábio; Piló, David; SORDO, LAURA; Gaspar, MiguelThis study aimed to characterize the catches, quantify fishing yield, bycatch and discards, and also estimate damage and mortality rates using hand dredges with two different mesh sizes (20 and 25 mm) for harvesting the wedge clam (Donax trunculus). A total of 160 tows were performed in Lota Beach and Armona Island in the Algarve coast (southern Portugal). Overall, were caught 12,319 individuals (3985 in Lota Beach and 8334 in Armona Island) belonging to 48 taxa distributed among seven phyla (14 taxa in Lota Beach and 44 taxa in Armona Island). Bycatch proportions ranged from 13.1% to 32.0% in abundance and from 10.7% to 32.9% in biomass, with more bycatch using hand dredges with 20 mm mesh size. Commercially undersized D. trunculus (MCRS = 25 mm SL) prevailed within the bycatch, representing over 40% of discards using both mesh sizes. Due to different size selectivity, the target catch (CPUE) and bycatch per unit effort (BCPUE) in abundance and biomass, as well as fishing yield as a function of tow duration and towed area, were lower for hand dredges with 25 mm mesh than with 20 mm mesh. In general, damage and mortality rates were fairly low (1.3-2.6%) independently of mesh size, reinforcing the importance of releasing live bycatch to the sea immediately after sorting the catches. Overall, this study prompted the need to develop a good practice guide for hand dredgers, aiming to mitigate avoidable indirect discards mortality and improve the sustainability of this traditional harvesting activity.
- Meat yield of Bolinus brandaris (Gastropoda: Muricidae): comparative assessment of the influence of sex, size and reproductive statusPublication . Vasconcelos, Paulo; Barroso, Carlos M.; Gaspar, Miguel B.The present study assessed the influence of sex, size and reproductive status on the meat yield (soft tissues proportion) of the purple dye murex (Bolinus brandaris) from the Ria Formosa lagoon (southern Portugal). During one year of monthly sampling (October 2008-September 2009), average meat yield of B. brandaris was 40.5 +/- 6.1% (range: 25.8-56.1% wet weight), with no significant differences between sexes. Relationships established between specimen size and soft parts weight indicated that both shell length and total weight are excellent indicators of meat yield. Significant differences in meat yield between size classes further reinforced the trend of increasing meat yield during ontogeny. Meat yield exhibited significant monthly variation and a similar temporal trend in both sexes, which were directly related to the reproductive status. Meat yield of B. brandaris was compared with that of other muricid species and the marked influence of the reproductive status on meat yield prompted a comparative assessment of the spawning season and peak of three sympatric muricids (B. brandaris, Hexaplex trunculus and Stramonita haemastoma). Overall, these findings have implications at diverse levels, including the management, regulation and inspection of this fishing/ harvesting activity and the commercialization and consumption of this seafood product.
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