Percorrer por autor "Carvalho, André N."
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- 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.
- Morphometric relationships, relative growth and roe yield of the sea urchin (Paracentrotus lividus) from the Portuguese coastPublication . Nicolau, Lídia; Vasconcelos, Paulo; Machado, Inês; Pereira, Fábio; Moura, Paula; Carvalho, André N.; Gaspar, MiguelSea urchin (Paracentrotus lividus) populations from the northwestern (Carreco) and southwestern (Aljezur) coasts of Portugal were surveyed to analyse and compare their morphometric relationships, relative growth (isometry vs. allometry) and roe yield. Specimens were hand-collected from intertidal rock pools and sampled monthly during two consecutive years (November 2010-November 2012). Overall, 1220 P. lividus larger than 40 mm in test diameter (542 from Carreco and 678 from Aljezur) were analysed during the study period. Morphometric relationships established between specimen size (test diameter, height and volume) and weight (total and gonad weight) were statistically significant and displayed high correlation coefficients (r = 0.484 - 0.974), with allometric coefficients ranging from b = 0.962 to 1.239 (linear variables) and from b = 2.541 to 3.437 (linear and ponderal variables). Sea urchins mean roe yield was significantly higher in Carreco (7.5 +/- 3.1%) than in Aljezur (6.8 +/- 3.5%) and varied depending on the sampling month. The present data on morphometric relationships, relative growth and roe yield was duly compared with previous studies available on these topics, through an exhaustive review covering the distributional range of P. lividus along the Atlantic Ocean and Mediterranean Sea.
- Occurrence, infestation rate, and spatiotemporal distribution of the African pea crab (Afropinnotheres monodi) inhabiting Mediterranean mussels (Mytilus galloprovincialis) from southern PortugalPublication . Santos, Agatha C. N.; Vasconcelos, Paulo; Pereira, Fábio; Piló, David; Carvalho, André N.; Gaspar, MiguelThe present study aimed to analyze the occurrence and prevalence, infestation rate and intensity, host-guest colonization pattern, morphometric relationships, and spatiotemporal distribution of the African pea crab (Afropinnotheres monodi) inhabiting the shell of Mediterranean mussels (Mytilus galloprovincialis) from the Algarve coast and Ria Formosa lagoon (southern Portugal). Sampling campaigns were performed with a trimestral periodicity in 2018-2019 and comprised 13 collecting sites distributed in the Ria Formosa, along the Algarve coast, and in an offshore mussel farm. Altogether, 10,109 individuals of M. galloprovincialis in a broad range of sizes (9.0-91.2 mm in shell length) were sampled, among which 571 host mussels (14.6-73.6 mm in shell length) contained a total of 598 individuals of A. monodi, corresponding to an infestation rate of 5.6% (prevalence rate of 5.9% due to multiple occurrences). The sample of pea crabs also covered an extensive range of sizes (1.7-14.5 mm in carapace width) and included eight juveniles, 163 males, and 427 females (82 hard females and 345 soft females, of which 128 were non-ovigerous and 217 ovigerous). Overall, hard (13.9%) and soft (58.5%) females prevailed over males (27.6%), corresponding to female-biased sex ratio of 1 male:2.6 females. In terms of infestation intensity, 95.4% of host mussels contained a single pea crab, with multiple infestations (two or three crabs inside a single mussel) being more frequent in the lagoon than along the coast. Morphometric relationships between host shell length and pea crab carapace width were highly correlated (r values ranged .218-.631), although there were no significant differences between sexes or female demographic categories and maturity stages. Overall, the present study provided further insights into the colonization of M. galloprovincialis by A. monodi.
- Recreational harvesting of the wedge clam (Donax trunculus) in southern Portugal: characterization of the activity based on harvesters’ perception and local ecological knowledgePublication . Sordo, Laura; Vasconcelos, Paulo; Piló, David; Carvalho, André N.; Pereira, Fábio; Gaspar, MiguelThis study was the first attempt to characterize the recreational harvesting of the wedge clam (Donax trunculus). For this purpose, 403 face-to-face interviews were performed in the summers of 2018 and 2019 in southern Portugal. The majority of the harvesters frequented the selected beaches during holidays and collected wedge clams as a hobby for an appetizer. The respondents reported an inter-annual variation in their catches of wedge clam with a decreasing abundance in 2018 followed by a recovery in 2019, but with more recreational harvesters collecting undersized individuals. Although most harvesters declared to consume D. trunculus, only a few bought wedge clams being the clams' size a secondary factor in their valorization. The majority of the recreational harvesters did not know the species' minimum conservation reference size nor the legally allowed maximum daily catch. It was estimated that recreational harvesters can collect 13 tonnes of wedge clams during the summer season along the southeastern coast of Algarve. Even though manual harvesting is not an efficient fishing technique, the lack of selectivity of harvesters can eventually compromise the resilience of D. trunculus populations. Despite most respondents affirmed to get informed about marine biotoxins, most surveys were done during periods of interdiction for shellfish harvesting. The present results revealed that the population is still unaware of the health risks of consuming shellfish contaminated with biotoxins. Educational activities and awareness campaigns are required to further inform recreational harvesters about the regulations in force for this activity and the sanitary threats of marine biotoxins.
- Shell morphology, morphometric relationships and relative growth of three topshell species (Gastropoda: Trochidae) from the Algarve Coast (Southern Portugal)Publication . Vasconcelos, Paulo; Santos, Agatha C. N.; Pereira, Fábio; Moura, Paula; Carvalho, André N.; Gaspar, MiguelThis study analysed the shell morphology, morphometric relationships and relative growth in three topshell species (Phorcus lineatus, Phorcus sauciatus and Steromphala umbilicalis) collected in the Algarve coast (southern Portugal). A total of 1382 individuals were sampled (465 P. lineatus, 447 P. sauciatus and 470 S. umbilicalis) and all species comprised individuals with broad size and weight ranges. Morphometric relationships were established between linear (shell height, width, spire height, aperture height, aperture width) and ponderal (total weight) variables, whose relative growth (isometry vs. allometry) was analysed to assess variation throughout the species ontogeny. All morphometric relationships were highly significant (P < 0.001) and displayed invariably high correlation coefficients (r = 0.828 to 0.977), presenting mostly negative allometries (77.8%), distantly followed by positive allometries (16.7%) and by isometric growth (5.5%). In addition, four morphometric indices (sphericity, conicity, aperture roundness and density) were calculated to further describe and discern variation in shell shape in these topshell species. Moreover, this study provides a useful compilation and comparison of morphometric relationships, indices and relative growth features, thus improving the knowledge currently available on these subjects for P. lineatus, P. sauciatus and S. umbilicalis.
- Size at sex change and reproductive cycle of the limpets Patella vulgata and Patella ulyssiponensis (Mollusca: Patellogastropoda) from intertidal rocky shores of the Algarve coast (southern Portugal)Publication . Vasconcelos, Paulo; Umapathy, Uthesh; Moura, Paula; Pereira, Fábio; Carvalho, André N.; Gaspar, MiguelThis study describes the reproductive cycle of the common limpet (Patella vulgata) and rough limpet (Patella ulyssiponensis) from the Algarve coast (southern Portugal). Individuals of both species were sampled monthly during two consecutive years, and subjected to gonad histology and calculation of the mean gonadal index (GI). Both species had balanced sex ratios (P. vulgata = 1M: 0.98F; P. ulyssiponensis = 1M: 1.03F), similar size-frequency distribution between sexes, and equivalent mean shell lengths (SL) and total weights (TW) between males and females. In these protandrous hermaphrodites, the estimated size at sex change was slightly smaller in P. vulgata (SL50 approximate to 29 mm) than in P. ulyssiponensis (SL50 approximate to 36 mm). The reproductive cycles of both species were characterised by a main spawning season in early spring to early summer, sometimes including subsidiary spawning events. A comparison of the main spawning season throughout the species distributional ranges revealed that populations of P. vulgata and P. ulyssiponensis from southern Portugal have later spawning periods than other populations from the northeastern Atlantic Ocean. The present information is relevant for conservation purposes and for the proposal of management measures for the harvesting activity targeting P. vulgata and P. ulyssiponensis in southern Portugal.