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Do individual seabirds specialize in fisheries' waste? The case of black-browed albatrosses foraging over the Patagonian Shelf Texto completo
1000 | 2014
Granadeiro, J. P. | Brickle, P. | Catry, P.
Do individual seabirds specialize in fisheries' waste? The case of black-browed albatrosses foraging over the Patagonian Shelf Texto completo
1000 | 2014
Granadeiro, J. P. | Brickle, P. | Catry, P.
Fisheries can have profound impacts on the structure and functioning of marine ecosystems and affect seabird populations. For seabirds, impacts can include direct mortality in fishing gear, but fisheries also represent an abundant source of food that may otherwise be inaccessible. Previous studies with seabirds have revealed the occurrence of individual foraging specializations, and therefore in scavenging species some individuals may have a higher propensity to feed on fisheries discharges than the rest of the population. Here we used recently developed techniques (spatio-temporal match of positions) to detect interactions between black-browed albatrosses Thalassarche melanophris and fishing vessels, and also stable isotope analysis of tissues with different turnovers, to investigate long-term individual specialization in fishery waste products. We combined global positioning system tracking data from 89 birds with vessel monitoring system data from the entire fleet operating around the Falklands Islands, in 2009 and 2011. Interactions with vessels (freezer/factory bottom trawlers) occurred in 15 out of 89 independent albatross trips. Among individuals tracked in both years, those that associated with fisheries in 2009 were not more likely to do so again in 2011. Carbon and nitrogen isotopic signatures in whole blood and feathers of albatrosses that interacted with trawlers were similar to those of individuals that did not. Also, we found no correlation between feather and blood isotopic ratios of carbon or nitrogen, indicating no long-term consistency in the isotopic niche of study birds. These results suggest no specialization of individual albatrosses with regard to fisheries. Studies of other albatrosses have also failed to show long-term trophic consistency, which may indicate that scavenging albatrosses, a group particularly threatened by fisheries activity, do not specialize in discards. Therefore, any management actions leading to a reduction of discards will be beneficial, decreasing the numbers of birds behind vessels and consequently the likelihood of incidental mortality.
Mostrar más [+] Menos [-]Do individual seabirds specialize in fisheries' waste? The case of black‐browed albatrosses foraging over the Patagonian Shelf Texto completo
2014
Granadeiro, J. P. | Brickle, P. | Catry, P.
Fisheries can have profound impacts on the structure and functioning of marine ecosystems and affect seabird populations. For seabirds, impacts can include direct mortality in fishing gear, but fisheries also represent an abundant source of food that may otherwise be inaccessible. Previous studies with seabirds have revealed the occurrence of individual foraging specializations, and therefore in scavenging species some individuals may have a higher propensity to feed on fisheries discharges than the rest of the population. Here we used recently developed techniques (spatio‐temporal match of positions) to detect interactions between black‐browed albatrosses Thalassarche melanophris and fishing vessels, and also stable isotope analysis of tissues with different turnovers, to investigate long‐term individual specialization in fishery waste products. We combined global positioning system tracking data from 89 birds with vessel monitoring system data from the entire fleet operating around the Falklands Islands, in 2009 and 2011. Interactions with vessels (freezer/factory bottom trawlers) occurred in 15 out of 89 independent albatross trips. Among individuals tracked in both years, those that associated with fisheries in 2009 were not more likely to do so again in 2011. Carbon and nitrogen isotopic signatures in whole blood and feathers of albatrosses that interacted with trawlers were similar to those of individuals that did not. Also, we found no correlation between feather and blood isotopic ratios of carbon or nitrogen, indicating no long‐term consistency in the isotopic niche of study birds. These results suggest no specialization of individual albatrosses with regard to fisheries. Studies of other albatrosses have also failed to show long‐term trophic consistency, which may indicate that scavenging albatrosses, a group particularly threatened by fisheries activity, do not specialize in discards. Therefore, any management actions leading to a reduction of discards will be beneficial, decreasing the numbers of birds behind vessels and consequently the likelihood of incidental mortality.
Mostrar más [+] Menos [-]Research and management priorities for Atlantic marine recreational fisheries in Southern Europe Texto completo
1000 | 2017
Pita, Pablo | Artetxe, Inaqui | Diogo, Hugo | Gomes, Pedro T. | Gordoa, Ana | Hyder, Kieran | Pereira, Joao | Pita, Cristina | Rangel, Mafalda | Garcia-Rodrigues, Joao | Sague, Oscar | Veiga, Pedro | Vingada, José V. | Villasante, Sebastian
Research and management priorities for Atlantic marine recreational fisheries in Southern Europe Texto completo
1000 | 2017
Pita, Pablo | Artetxe, Inaqui | Diogo, Hugo | Gomes, Pedro T. | Gordoa, Ana | Hyder, Kieran | Pereira, Joao | Pita, Cristina | Rangel, Mafalda | Garcia-Rodrigues, Joao | Sague, Oscar | Veiga, Pedro | Vingada, José V. | Villasante, Sebastian
Marine Recreational Fishing (MRF) is an important activity in Europe, with 9 million fishers and generating annually 6 billion in direct expenditures. However, there is a lack of data and understanding of MRF in Europe, particularly in Southern countries, which prevents a number of fish stocks from being effectively assessed and managed. In November 2016, a participatory workshop on MRF was held in Vigo (Spain) to identify challenges and opportunities for data collection, and to diagnose key research gaps and management issues for MRF in the Southern European Atlantic. Experts from a wide range of disciplines (researchers, policy makers, fisheries managers and commercial and recreational fishers) highlighted that the management of MRF is a challenge due to complex and dispersed legal frameworks, with multiple administrations involved, and overlapping uses of space with commercial fishing, aquaculture, navigation and tourism, among others. The lack of strong and representative fishing associations hampers research and management initiatives. Effective communication between recreational fishers, researchers and fisheries managers is also lacking. Despite the ecological, social and economic relevance of MRF, there is no systematic and comprehensive collection of information on fishing effort, recreational catches, expenses, social profile and access conditions of European recreational fishers. These data would be useful to avoid biases in the assessment of recreational fisheries due to the great diversity of ecosystems, species and typologies of users. Strategic recommendations and research priorities were also identified to address knowledge gaps and are discussed in the context of the management of MRF across Europe. | The 1st Workshop on Recreational Fishing on the Iberian Atlantic Coast was co-convened by the Federacion Gallega de Pesca Maritima Responsible y Nautica de Recreo, WWF-Spain, the Federacion Gallega de Actividades Subacuaticas, the International Forum for Sustainable Underwater Activities and the Universities of Santiago de Compostela, Minho and Aveiro. The workshop was also supported by the Confederacion Espanola de Pesca Recreativa Responsible, the Federacion Galega de Confrarias de Pescadores and the Autonomous Government of Galicia. The workshop was funded by the Autonomous Government of Galicia, RECREGES project under Grant [ED481B2014/034-0], by the conveners and through financial contributions of Baitra Accesorios Navales, Disvent Ingenieros, Jesus Betanzos Efectos Navales, Talleres Franinox and Yamaha. CP would also like to acknowledge FCT/MEC national funds and FEDER co-funding, within the PT2020 partnership Agreement and Compete 2020, for the financial support to CESAM, under Grant [UID/AMB/50017/2013].
Mostrar más [+] Menos [-]Research and management priorities for Atlantic marine recreational fisheries in Southern Europe Texto completo
2017
Pita, Pablo | Artetxe, Inaqui | Diogo, Hugo | Gomes, Pedro | Gordoa, Ana | Hyder, Kieran | Pereira, Joao | Pita, Cristina | Rangel, Mafalda | Garcia-Rodrigues, Joao | Sague, Oscar | Veiga, Pedro | Vingada, Jose | Villasante, Sebastian
Marine Recreational Fishing (MRF) is an important activity in Europe, with 9 million fishers and generating annually 6 billion in direct expenditures. However, there is a lack of data and understanding of MRF in Europe, particularly in Southern countries, which prevents a number of fish stocks from being effectively assessed and managed. In November 2016, a participatory workshop on MRF was held in Vigo (Spain) to identify challenges and opportunities for data collection, and to diagnose key research gaps and management issues for MRF in the Southern European Atlantic. Experts from a wide range of disciplines (researchers, policy makers, fisheries managers and commercial and recreational fishers) highlighted that the management of MRF is a challenge due to complex and dispersed legal frameworks, with multiple administrations involved, and overlapping uses of space with commercial fishing, aquaculture, navigation and tourism, among others. The lack of strong and representative fishing associations hampers research and management initiatives. Effective communication between recreational fishers, researchers and fisheries managers is also lacking. Despite the ecological, social and economic relevance of MRF, there is no systematic and comprehensive collection of information on fishing effort, recreational catches, expenses, social profile and access conditions of European recreational fishers. These data would be useful to avoid biases in the assessment of recreational fisheries due to the great diversity of ecosystems, species and typologies of users. Strategic recommendations and research priorities were also identified to address knowledge gaps and are discussed in the context of the management of MRF across Europe. | Confederacion Espanola de Pesca Recreativa Responsible | Federacion Galega de Confrarias de Pescadores | Autonomous Government of Galicia | Autonomous Government of Galicia, RECREGES [ED481B2014/034-0] | Baitra Accesorios Navales | Disvent Ingenieros | Jesus Betanzos Efectos Navales | Talleres Franinox | Yamaha | FCT/MEC | FEDER [UID/AMB/50017/2013]
Mostrar más [+] Menos [-]Interannual variability in the biochemical composition of newly hatched larvae of the spider crab Maja brachydactyla (Decapoda, Majidae) Texto completo
1000 | 2014
Rotllant, Guiomar | Simeó, Carles G. | Guerao, Guillermo | Sastre, Marta | Cleary, Daniel F. R. | Calado, Ricardo | Estévez, Alicia
The spider crab Maja brachydactyla is an important commercial species in Europe and supports intensive fisheries in the NE Atlantic. A field survey was performed to assess long-term and consecutive interannual (2005–2010) variation of the biochemical composition of newly hatched larvae of M. brachydactyla. Larval biochemical profiles differed significantly among years, with pronounced differences being recorded in 2010. Differences among batches of newly hatched larvae were mainly explained by the contribution of triacylglycerols and, to a lesser degree, by protein and lipid content. The use of different nutrition indices is discussed. The biochemical composition of newly hatched larvae from M. brachydactyla was highly variable, even though surveyed broodstock was obtained from the same local population and was always sampled during the same season. The unpredictable biochemical profiles of newly hatched larvae may condition their survival and recruitment. This largely overlooked aspect of larval variability should be considered in future fisheries management strategies and captive production of marine organisms that still rely on wild seeds.
Mostrar más [+] Menos [-]Economic, social and ecological attributes of marine recreational fisheries in Galicia, Spain Texto completo
1000 | 2018
Pita, Pablo | Hyder, Kieran | Gomes, Pedro T. | Pita, Cristina | Rangel, Mafalda | Veiga, Pedro | Vingada, José V. | Villasante, Sebastian
Economic, social and ecological attributes of marine recreational fisheries in Galicia, Spain Texto completo
1000 | 2018
Pita, Pablo | Hyder, Kieran | Gomes, Pedro T. | Pita, Cristina | Rangel, Mafalda | Veiga, Pedro | Vingada, José V. | Villasante, Sebastian
There are growing concerns about the impact of Marine Recreational Fishing (MRF) on marine ecosystems and its combined effects with other human activities, such as commercial fishing, especially on the higher trophic levels. Conversely, recreational fishers provide considerable economic benefits through their expenditure on many things including fishing tackle, boats, licenses, travel, and accommodation. However, research on MRF in Europe is limited, particularly in Southern countries. In Galicia (Northwest Spain) detailed information on MRF is still needed to support management and to reduce growing conflicts between recreational fishers and other stakeholders including the commercial fishing sector. This paper provides the first comprehensive analysis of MRF in Galicia including the economic, social, and ecological impacts, from a survey of 363 recreational fishers. It was estimated that there are 60 000 recreational fishers, comprised of 45 000 shore anglers, 12000 boat anglers and 3 000 spear fishers. Each year, they spend 86 EM on fishing gear and other expenses, while boat owners spend another 11 EM. Fishers activity is higher in summer and spring, especially in the case of boat anglers. Recreational fishers reported catching 38 species, but the most common were ballan wrasse (Labrus bergylta), European seabass (Dicentrarchus labrax), and white seabream (Diplodus sargus). Annual recreational catch is about 7 500 t (5-13% of commercial and recreational landings of the same species); shore anglers are responsible for 50% of total MRF catches, boat anglers for 40%, and spear fishers for 10%. The results are discussed in the context of management that could improve the socio-ecological sustainability of MRF. | The authors acknowledge the valuable comments and suggestions received at the 8th World Recreational Fishing Conference in July 16-20th, 2017 at Victoria, Canada. PP thanks the financial support from Xunta de Galicia (RECREGES project under Grant ED481B2014/034-0), and to Paz Brage, Eugenia Rodriguez, Ma Jose Cancelo, Ma Nazaret Diaz, Pablo R. Fernandez, and Carmen de Benito from Xunta de Galicia for providing information about recreational fishing licenses. Also, thanks Jose. A. Beiro and Francisco J. Nunez, chairmen of FEDPEMAR and FEGAS respectively, for their help and support. SV is grateful to the Xunta de Galicia for financial aid through project GPC 2015-045, and ICES Science Fund Project "Social transformations of marine social ecological systems". MR wishes to acknowledge the financial support of the Portuguese Science Foundation (FCT) through the post-doctoral grant SFRH/BPD/116307/2016. CP would like to acknowledge FCT/ MEC national funds and FEDER co-funding, within the PT2020 partnership Agreement and Compete 2020, for the financial support to CESAM (Grant No. UID/AMB/50017/2013).
Mostrar más [+] Menos [-]Economic, social and ecological attributes of marine recreational fisheries in Galicia, Spain Texto completo
2018
Pita, Pablo | Hyder, Kieran | Gomes, Pedro | Pita, Cristina | Rangel, Mafalda | Veiga, Pedro | Vingada, José | Villasante, Sebastián
There are growing concerns about the impact of Marine Recreational Fishing (MRF) on marine ecosystems and its combined effects with other human activities, such as commercial fishing, especially on the higher trophic levels. Conversely, recreational fishers provide considerable economic benefits through their expenditure on many things including fishing tackle, boats, licenses, travel, and accommodation. However, research on MRF in Europe is limited, particularly in Southern countries. In Galicia (Northwest Spain) detailed information on MRF is still needed to support management and to reduce growing conflicts between recreational fishers and other stakeholders including the commercial fishing sector. This paper provides the first comprehensive analysis of MRF in Galicia including the economic, social, and ecological impacts, from a survey of 363 recreational fishers. It was estimated that there are 60 000 recreational fishers, comprised of 45 000 shore anglers, 12 000 boat anglers and 3000 spear fishers. Each year, they spend 86 €M on fishing gear and other expenses, while boat owners spend another 11 €M. Fishers’ activity is higher in summer and spring, especially in the case of boat anglers. Recreational fishers reported catching 38 species, but the most common were ballan wrasse (Labrus bergylta), European seabass (Dicentrarchus labrax), and white seabream (Diplodus sargus). Annual recreational catch is about 7 500 t (5–13% of commercial and recreational landings of the same species); shore anglers are responsible for 50% of total MRF catches, boat anglers for 40%, and spear fishers for 10%. The results are discussed in the context of management that could improve the socio-ecological sustainability of MRF.
Mostrar más [+] Menos [-]Interaction between bottlenose dolphin (Tursiops truncatus) and trammel nets in the Archipelago de La Maddalena, Italy Texto completo
1000 | 2015
Pennino, M. Grazia | Rotta, A. | Pierce, Graham J. | Bellido, José M.
Interactions between bottlenose dolphins (Tursiops truncatus) and fisheries are an increasing problem in the Mediterranean and effective management measures are needed. In order to assess the impact of dolphin interactions on artisanal trammel nets, we examine 354 fishing operations performed in waters of the Archipelago de La Maddalena (Italy). We evaluate whether interactions were related to the species composition of the catch and, using the local commercial value of the target species, we assess whether there was a real economic loss for fishermen. Bayesian models and partial correspondence analysis were used to determine the extent to which dolphin interactions and habitat differences contributed to variation in the species composition of catches. CPUE for fishing operations with no dolphin interactions was significantly higher than that for operations with dolphin interactions, although clearly this does not confirm a direct causal link, and associated economic loss was estimated to be non-significant. Geographic location, season, depth of seabed, moon phase, and mesh size were all important factors affecting the amount and species composition of the catch. Our results suggest that it is likely that these differences in species composition are due to a mixture of habitat and dolphin-induced effects.
Mostrar más [+] Menos [-]Cross-vessel eco-efficiency analysis. A case study for purse seining fishing from North Portugal targeting European pilchard Texto completo
1000 | 2015
González-García, Sara | Villanueva-Rey, Pedro | Belo, Sara | Vázquez-Rowe, Ian | Teresa Moreira, María | Feijoo, Gumersindo | Arroja, Luis
Cross-vessel eco-efficiency analysis. A case study for purse seining fishing from North Portugal targeting European pilchard Texto completo
1000 | 2015
González-García, Sara | Villanueva-Rey, Pedro | Belo, Sara | Vázquez-Rowe, Ian | Teresa Moreira, María | Feijoo, Gumersindo | Arroja, Luis
Purpose European pilchard captures constitute an important source of income for the Portuguese fishing sector. This raw material is used for a varied range of final seafood products, such as canning, fresh seafood consumption or bait for other fisheries. The Portuguese purse seining fleet, which concentrates most of the pilchard landings, has recently obtained the Marine Stewardship Council certification scheme, demonstrating the effort of the fleet to comply with sustainable fishing practices. However, this scheme does not consider the human inputs to the fishery, such as fuel consumption or the use of other materials and resources. Consequently, life-cycle methods, such as Life Cycle Assessment (LCA), have arisen to provide a thorough assessment of the environmental profile of fishing fleets. In the current study, LCA is combined with Data Envelopment Analysis (DEA), a management tool, in order to understand the eco-efficiency of the individual vessels that compose this fleet. Methods A 5-step LCA+DEA method, previously used to assess resembling vessel samples, was used to examine the efficiency of 20 purse seiners in the northern Portugal for years 2011 and 2012. Individual Life Cycle Inventories (LCIs) were gathered for each vessel to perform, thereafter, the Life Cycle Impact Assessment (LCIA). DEA matrices were generated based on the LCI in order to obtain the efficiency values for each unit. Finally, based on the efficiency projections provided by the DEA model, a new LCIA was performed for inefficient vessels in order to calculate the potential environmental benefits of operating at higher levels of efficiency. Results and discussion The average efficiency of the fleet in the two different years of assessment was slightly above 60 %. Moreover, individual vessels showed a fairly low standard deviation across the 2 years of assessment, demonstrating that units with higher levels of efficiency tend to maintain these values through the analysed window. In fact, this result, given its strong correlation with fuel use, appears to have relation with the existence of a certain level of Bskipper effect^. Important environmental benefits, mainly linked to the optimisation of fuel resources, could be attained if inefficient vessels were to operate efficiently, especially in terms of two main impact categories: climate change and fossil depletion. Conclusions The results in this study confirm that fishing small-pelagic fish shows low energy intensity as compared to other fisheries. However, despite this worldwide tendency, the use of LCA+DEA confirms that substantial improvements in terms of optimising energy and material inputs, as well as in reducing environmental impacts, can be attained in these fishing fleets.
Mostrar más [+] Menos [-]Cross-vessel eco-efficiency analysis. A case study for purse seining fishing from North Portugal targeting European pilchard Texto completo
2015
González-García, Sara | Villanueva-Rey, Pedro | Belo, Sara | Vázquez-Rowe, Ian | Moreira, Maria Teresa | Feijoo, Gumersindo | Arroja, Luis
PURPOSE: European pilchard captures constitute an important source of income for the Portuguese fishing sector. This raw material is used for a varied range of final seafood products, such as canning, fresh seafood consumption or bait for other fisheries. The Portuguese purse seining fleet, which concentrates most of the pilchard landings, has recently obtained the Marine Stewardship Council certification scheme, demonstrating the effort of the fleet to comply with sustainable fishing practices. However, this scheme does not consider the human inputs to the fishery, such as fuel consumption or the use of other materials and resources. Consequently, life-cycle methods, such as Life Cycle Assessment (LCA), have arisen to provide a thorough assessment of the environmental profile of fishing fleets. In the current study, LCA is combined with Data Envelopment Analysis (DEA), a management tool, in order to understand the eco-efficiency of the individual vessels that compose this fleet. METHODS: A 5-step LCA + DEA method, previously used to assess resembling vessel samples, was used to examine the efficiency of 20 purse seiners in the northern Portugal for years 2011 and 2012. Individual Life Cycle Inventories (LCIs) were gathered for each vessel to perform, thereafter, the Life Cycle Impact Assessment (LCIA). DEA matrices were generated based on the LCI in order to obtain the efficiency values for each unit. Finally, based on the efficiency projections provided by the DEA model, a new LCIA was performed for inefficient vessels in order to calculate the potential environmental benefits of operating at higher levels of efficiency. RESULTS AND DISCUSSION: The average efficiency of the fleet in the two different years of assessment was slightly above 60 %. Moreover, individual vessels showed a fairly low standard deviation across the 2 years of assessment, demonstrating that units with higher levels of efficiency tend to maintain these values through the analysed window. In fact, this result, given its strong correlation with fuel use, appears to have relation with the existence of a certain level of “skipper effect”. Important environmental benefits, mainly linked to the optimisation of fuel resources, could be attained if inefficient vessels were to operate efficiently, especially in terms of two main impact categories: climate change and fossil depletion. CONCLUSIONS: The results in this study confirm that fishing small-pelagic fish shows low energy intensity as compared to other fisheries. However, despite this worldwide tendency, the use of LCA + DEA confirms that substantial improvements in terms of optimising energy and material inputs, as well as in reducing environmental impacts, can be attained in these fishing fleets.
Mostrar más [+] Menos [-]Zooplankton structure and dynamics in two estuaries from the Atlantic coast in relation to multi-stressors exposure Texto completo
1000 | 2015
Vieira, L. R. | Guilhermino, L. | Morgado, F.
The aim of this research was to investigate the response of pelagic zooplankton to different levels of abiotic multi-stressors in the North Atlantic coast, taking advantage of the comparison of the communities of two adjacent estuaries with different levels of historical pollution (estuaries of Minho and Lima Rivers). The zooplankton community structure, composition and temporal variation were comparatively investigated for 15 months, using different net meshes. Several abiotic factors were measured in situ and water samples were simultaneously collected for determination of nutrients and chlorophyll a. The overall results revealed a diverse community represented by species that have been found in subtropical and temperate zones. Although the highest diversity was observed in the Lima estuary, supported by higher contributions of marine taxa, the total zooplankton biomass was found to be significantly higher in the Minho estuary. The salinity gradient differences between estuaries, associated to significant differences in water nutrients levels, were found to be the main forcing factors affecting micro and mesozooplankton. Considering the importance of the impacts resulting from abiotic variation on the basis of aquatic food webs, the present investigation represented a case-study, based in two contrasting estuaries, one strongly influenced by freshwater discharges (Minho estuary) and the other with higher salinity levels (Lima estuary), contributing to a better understanding of the effects of multi-stressors on pelagic zooplankton communities, providing useful information for studies related with climate change impacts, biogeography, conservation and providing data contributing to the improvement of pelagic fisheries management models.
Mostrar más [+] Menos [-]Essential habitats for pre-recruit Octopus vulgaris along the Portuguese coast Texto completo
1000 | 2014
Moreno, A. | Lourenço, S. | Pereira, J. | Gaspar, M. B. | Cabral, H. N. | Pierce, G. J. | Santos, A. M. P.
Essential habitats for pre-recruit Octopus vulgaris along the Portuguese coast Texto completo
1000 | 2014
Moreno, A. | Lourenço, S. | Pereira, J. | Gaspar, M. B. | Cabral, H. N. | Pierce, G. J. | Santos, A. M. P.
The exploitation of the common octopus Octopus vulgaris in Portugal increased 50% in the last 20 years, largely motivated by the depletion of many fish stocks. Recently, the biomass of this fishery resource sharply decreased in some areas causing serious concern among local fishermen and an effort is underway to advise on novel and sustainable management measures. In this context, the octopus pre-recruit aggregations along the Portuguese coast are identified using georeferenced fishery-independent data, from autumn and winter sampling between 1996 and 2008. The relationships between pre-recruit aggregations and several environmental variables are analyzed to characterize their essential habitats (EFH). Pre-recruits are distributed throughout the Portuguese coast aggregated in 8 distinct recruitment grounds located on the middle-shelf at 11-19. km from the coastline, which are characterized by average bottom depths of 65-110. m and are associated to major rivers and lagoon systems. Within each season pre-recruit abundance is much higher in the south region, while pre-recruit aggregations on the northwest coast showed high inter-annual and seasonal variation driven by environmental variability. The western zone adjacent to Ria Formosa lagoon (southern coast) was identified as the main recruitment ground for O. vulgaris along the Portuguese coast. This is supported by the higher abundance of pre-recruits and by the recurrence of their presence in this area over the years analyzed, both in autumn and winter. The effects of physical variables on pre-recruit abundance modelled with generalized additive models (GAM) showed important regional differences. Bottom salinity and river runoff are the environmental variables that have most impact on pre-recruit distribution and abundance on the west coast, regardless of any seasonal effects. On the other hand, temperature imposes distinct seasonal and regional limitations on pre-recruit distribution, both on the NW and S regions. Pre-recruit preferential habitat is characterized by bottom temperatures of 14. °C, salinity values around 36.0, low precipitation (average <200. mm), and coarse sediments (in which they find shelters to escape predation). Some of the octopus recruitment grounds identified are located in areas under intense fishing pressure, both by artisanal fisheries using traps and by bottom trawling. Thus, their value for the sustainability of the octopus fishery should be taken into consideration in future marine management strategies.
Mostrar más [+] Menos [-]Essential habitats for pre-recruit Octopus vulgaris along the Portuguese coast Texto completo
2014
Moreno, A. | Lourenço, S. | Pereira, J. | Gaspar, M.B. | Cabral, H.N. | Pierce, G.J. | Santos, A.M.P.
The exploitation of the common octopus Octopus vulgaris in Portugal increased 50% in the last 20 years, largely motivated by the depletion of many fish stocks. Recently, the biomass of this fishery resource sharply decreased in some areas causing serious concern among local fishermen and an effort is underway to advise on novel and sustainable management measures. In this context, the octopus pre-recruit aggregations along the Portuguese coast are identified using georeferenced fishery-independent data, from autumn and winter sampling between 1996 and 2008. The relationships between pre-recruit aggregations and several environmental variables are analyzed to characterize their essential habitats (EFH). Pre-recruits are distributed throughout the Portuguese coast aggregated in 8 distinct recruitment grounds located on the middle-shelf at 11–19km from the coastline, which are characterized by average bottom depths of 65–110m and are associated to major rivers and lagoon systems. Within each season pre-recruit abundance is much higher in the south region, while pre-recruit aggregations on the northwest coast showed high inter-annual and seasonal variation driven by environmental variability. The western zone adjacent to Ria Formosa lagoon (southern coast) was identified as the main recruitment ground for O. vulgaris along the Portuguese coast. This is supported by the higher abundance of pre-recruits and by the recurrence of their presence in this area over the years analyzed, both in autumn and winter. The effects of physical variables on pre-recruit abundance modelled with generalized additive models (GAM) showed important regional differences. Bottom salinity and river runoff are the environmental variables that have most impact on pre-recruit distribution and abundance on the west coast, regardless of any seasonal effects. On the other hand, temperature imposes distinct seasonal and regional limitations on pre-recruit distribution, both on the NW and S regions. Pre-recruit preferential habitat is characterized by bottom temperatures of 14°C, salinity values around 36.0, low precipitation (average <200mm), and coarse sediments (in which they find shelters to escape predation). Some of the octopus recruitment grounds identified are located in areas under intense fishing pressure, both by artisanal fisheries using traps and by bottom trawling. Thus, their value for the sustainability of the octopus fishery should be taken into consideration in future marine management strategies.
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