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GESTÃO DO RECURSO, INCIDÊNCIA DE IMPOSEX, POTENCIAL DE MOLUSCICULTURA E VIABILIDADE DE REPOVOAMENTO DA CANILHA BOLINUS BRANDARIS NA RIA FORMOSA

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Publications

Meat yield of Bolinus brandaris (Gastropoda: Muricidae): comparative assessment of the influence of sex, size and reproductive status
Publication . 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.
Socio-economic, operational and technical characterisation of the harvesting of gooseneck barnacle (Pollicipes pollicipes) in SW Portugal: Insights towards fishery co-management
Publication . Carvalho, Andre N.; Vasconcelos, Paulo; Pilo, David; Pereira, Fabio; Gaspar, Miguel
The present study characterised the socio-economic, operational and technical aspects of harvesting the gooseneck barnacle (Pollicipes pollicipes) along the southwestern coast of Portugal. For this purpose, face-to-face interviews were conducted with commercial harvesters of the two most representative fishery associations (covering 51% licensed harvesters) in the area of the Parque Natural do Sudoeste Alentejano e Costa Vicentina. Based on traditional ecological knowledge, this study confirmed the local importance, ancestral character and family traditions of this activity, which constitutes the exclusive occupation of nearly half of the interviewed harvesters and an important source for household incomes. In addition, data was also gathered on preferential fishing zones, harvesting effort and duration, daily catches and selling prices. The main concerns, problems and difficulties experienced in this activity relate to the excessive number of recreational harvesters, creating problems at the levels of exploitation, commercialisation, management and inspection. The study further confirms the rising interest and involvement of the commercial harvesters in enhancing the competences of the local fishery associations. In particular, local harvesters want to encourage the development of a co-management system comprising spatial-temporal measures to avoid conflicts of use over space and resources, as well as innovative marketing strategies to improve the recognition, value and traceability of the shellfish. Overall, the information gathered is most valuable for adopting an alternative approach based on the cooperation and co-responsibility at local and regional levels, involving the stakeholders in the proposal of management measures adapted to the specificities of this area, activity and resource.
Reproductive cycle of the commercially harvested sea urchin (Paracentrotus lividus) along the western coast of Portugal
Publication . Machado, Ines; Moura, Paula; Pereira, Fabio; Vasconcelos, Paulo; Gaspar, Miguel
Harvested populations of the sea urchin (Paracentrotus lividus) from the northwestern (Carreco) and southwestern (Aljezur) coasts of Portugal were surveyed to describe the species reproductive cycle and assess possible relationships with geographical location and seawater temperature. Individuals were sampled monthly to analyze gonad histology, mean gonadal index (GI), and gonadosomatic index (GSI) during 2 consecutive years (November 2010-November 2012). Both populations presented an annual reproductive cycle, with synchronous gonad maturation and gamete release between sexes. Gonad maturation occurred throughout autumn-winter, followed by a single but prolonged spawning season during spring-summer. The duration of the spawning season displayed a latitudinal gradient likely related to the north-south increasing trend in seawater temperature, with the northwestern population (Carreco) exhibiting a shorter spawning period compared to the southwestern population (Aljezur). The timing and duration of the spawning season was compared with several populations throughout the distributional range of P. lividus in the Atlantic Ocean and Mediterranean Sea. In the population from Carreco, the size at first sexual maturity (test diameter = 35.9 mm) was considerably smaller than the minimum conservation reference size (MCRS) of 50 mm test diameter legally established for P. lividus. This study confirms that sustainable exploitation depends on harvesters' awareness of and compliance with the MCRS and provides useful information for the eventual establishment of a closed season in the harvesting of P. lividus.
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, Miguel
Although 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.

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Funding agency

Fundação para a Ciência e a Tecnologia

Funding programme

Funding Award Number

SFRH/BPD/26348/2006

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