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Gharsallah I.H.,Institute National Des Science Et Technologies Of La Mer Instm | Vasconcelos P.,Instituto Nacional Of Recursos Biologicos Inrb | Zamouri-Langar N.,Institute National Des Science Et Technologies Of La Mer Instm | Missaoui H.,Direction Generale de la Peche et de lAquaculture DGPA
Aquatic Biology | Year: 2010

This study investigates the reproductive cycle, size at first sexual maturity and biochemical composition of Hexaplex trunculus from the Bizerte lagoon (northern Tunisia). Overall, females predominated over males, resulting in an unbalanced sex ratio of 1.2:1. Males dominated in the smaller size classes (<40 mm shell length, SL), sex ratios were balanced at the 40 to 50 mm SL range, and females dominated in the larger size classes (>50 mm SL). The gonad developmental stages and the gonadosomatic index (GSI) indicated that H. trunculus apparently has an annual reproductive cycle with extended periods of gonadal activity. In both sexes, examination of the appearance of the gonads showed that gamete release occurred mainly from March to May (with an apparent spawning between March and April), followed by a period of empty gonads between June and August. Sexual maturity occurred at smaller sizes in males (SL50 = 41.02 mm SL) than in females (SL50 = 50.47 mm SL). The contents of protein, lipids and carbohydrates were invariably greater in the gonads than in the foot, confirming the key role of the reproductive tissues in energetic storage. The monthly variation in protein, lipids and carbohydrates in the gonads followed the oscillation in the relative proportion of developed gonads and in the GSI, reflecting energetic mobilisation during maturation and spawning. Overall, the data gathered in this study constitutes valuable baseline information for making preliminary recommendations to the fishing community targeting H. trunculus in the Bizerte lagoon. Further studies and more solid data on the reproductive cycle of the species are required before definitive management measures for this locally important artisanal fishery can be proposed. © Inter-Research 2010. Source

Tzanatos E.,University of Patras | Castro J.,Spanish Institute of Oceanography | Forcada A.,University of Alicante | Matic-Skoko S.,Croatian Institute Of Oceanography And Fisheries | And 2 more authors.
ICES Journal of Marine Science | Year: 2013

The present work presents an integrated comparative assessment of the sustainability of fishing tactics or métiers (combinations of area, season, fishing gear, and target species). An index, which includes biological, conservation, socioeconomic, and management criteria, was created for this purpose: the "Métier Sustainability Index" (MSI25). It was designed using the traffic lights approach and comprises 25 indicators that refer to the "health" of the fisheries. Additionally, the MSI25 provides an indication of the "certainty" of that information with regard to the data type/heterogeneity. Subsequently, the index was tested using data from six case studies (81 métiers) from the Mediterranean and the Atlantic. The index showed that 63.0% of the métiers were "sustainable", 21.0% were "unsustainable" and 16.0% were "under pressure"; 59.3% of characterizations were considered as "certain". The index evaluation showed significant differences between areas and gears. This paper considers the characteristics of the datasets used, the case management status, and the applicability of the index in improving the management of specific fisheries. Overall, the MSI25 was found to be a useful tool for the evaluation and management of highly heterogeneous fisheries and data from various sources and types. © 2012 International Council for the Exploration of the Sea. Source

Vasconcelos P.,Instituto Nacional Of Recursos Biologicos Inrb | Morgado-Andre A.,University of Algarve | Morgado-Andre C.,University of Algarve | Gaspar M.B.,Instituto Nacional Of Recursos Biologicos Inrb
ICES Journal of Marine Science | Year: 2011

The smooth clam Callista chione is exploited by a fleet of dredgers along the southwestern coast of Portugal and suffers from a high incidence of shell damage. The force required to break C. chione shells in relation to fishing impacts and dredge damage is quantified. Fishing trials and shell-strength measurements (compression and compaction experiments) were performed to determine whether shell damage was attributable to the direct impact of the dredge teeth or to sediment compaction. A three-dimensional model of C. chione was subjected to simulated force by the finite element method. Analyses of damage areas and breakage patterns revealed two groups of samples, one containing the samples from compression experiments and another with the samples from dredging and compaction experiments, suggesting that most shell damage was attributable to compaction within the sediment. Information is provided to help improve the design of bivalve dredges, by increasing both length and angle of the dredge teeth, which would reduce the compaction force and distribute it differentially within the sediment, forcing upward movement of the bivalves. © 2010 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved. Source

Vasconcelos P.,Instituto Nacional Of Recursos Biologicos Inrb | Gaspar M.B.,Instituto Nacional Of Recursos Biologicos Inrb
Journal of Environmental Monitoring | Year: 2010

The present study aimed at creating a so called "single-site baseline" (SSB) of imposex in the purple dye murex (Bolinus brandaris) from the Ria Formosa lagoon (Algarve coast, southern Portugal), at the moment that the IMO Antifouling System Convention (banning globally the use of organotin compounds in antifouling paints on ships' hulls) entered into force (September 2008). In the context of monitoring long-term temporal trends of pollution levels, SSBs are proposed whenever it is difficult to obtain adequate numbers of bioindicator specimens in most of the study area or if significant short-term variability in imposex levels is likely to occur. In order to deal with these constraints, this study created a SSB by sampling on a monthly-basis (from October 2008 to September 2009) in a single site considered to be representative of the Ria Formosa as a whole (vicinities of the Culatra Island) and where B. brandaris is abundant all year round. The SSB provided a good characterisation of the monthly variation in the imposex indices, which ranged throughout the year between 72.7 < I% < 100; 0.08 < FPLI < 1.73; 1.20 < RPLI < 23.27; 1.29 < VDSI < 3.54. Only a SSB could have detected this large variability, which otherwise might have been unnoticed and would have produced biased temporal and spatial comparisons, leading to erroneous interpretations of environmental monitoring data. Therefore, this SSB of imposex in B. brandaris constitutes valuable reference data to assess the future trend of organotin pollution in the Ria Formosa, after the benchmark date of the complete eradication of organotin from antifouling agents was implemented worldwide. © 2010 The Royal Society of Chemistry. Source

Matos E.,University of Algarve | Goncalves A.,Instituto Nacional Of Recursos Biologicos Inrb | Nunes M.L.,Instituto Nacional Of Recursos Biologicos Inrb | Dinis M.T.,University of Algarve | Dias J.,University of Algarve
Aquaculture | Year: 2010

The aim of this study was to assess the independent effects of harvesting stress and slaughter method on seabream flesh quality. Two groups of 32 gilthead seabream (mean body weight: 536 ± 96 g) were subjected to different pre-slaughter harvesting stress: profound anesthesia (PA, low stress condition) and net crowding (NC, high stress condition). Subsequently, fish from both harvesting stress conditions were slaughtered using either ice-salt water slurry (IW), to simulate commercial practices, or a lethal dose of anesthesia (LA), to isolate the effect of the pre-slaughter treatments. Rigor mortis was measured during the first 72 h after death, and muscle from the dorsal area was collected at regular intervals (0, 2, 6 and 48 h after death) during this period, for subsequent biochemical analysis of pH, TBARS, sulfated glycosaminoglycans and hydroxyproline content. Texture in raw and cooked fillets was measured instrumentally, using an Instron texture analyzer. The onset of rigor mortis was earliest for the NC-IW treatment, reaching highest values 2 h after death, while fish from the PA-IW treatment attained highest rigor scores 21 h after death. Resolution of rigor mortis started 3 and 32 h after death in fish subjected to NC and PA, respectively. Both harvesting stress and slaughter method had a significant effect (P< 0.05) on muscle pH, with highest values found in fish subjected to PA conditions, and in those slaughtered by lethal anesthesia. Muscle TBARS were significantly affected by harvesting stress. Collagen and sulfated glycosaminoglycan content of the samples decreased markedly through storage time, but were not significantly affected by harvesting stress conditions or slaughter method. In fish slaughtered in ice-salt water slurry, fillet hardness ranged between 5.0 ± 2.1 and 5.7 ± 1.8. N in raw fillets, and between 4.9 ± 0.9 and 5.6 ± 0.9. N in cooked fillets, but no significant differences among treatments were found. The use of zero withdrawal anesthetic improved muscle pH and delayed rigor mortis, although harvesting and slaughter stress had no major effect on muscle structure of gilthead seabream. © 2010 Elsevier B.V. Source

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