Instituto Portugues Do Mar E Da Atmosfera Ipma Ip

Olhão, Portugal

Instituto Portugues Do Mar E Da Atmosfera Ipma Ip

Olhão, Portugal
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Fraile I.,Tecnalia | Arrizabalaga H.,Tecnalia | Groeneveld J.,University of Bremen | Kolling M.,University of Bremen | And 7 more authors.
Journal of Marine Systems | Year: 2016

Otoliths of Atlantic bluefin tuna (Thunnus thynnus) collected from the Mediterranean Sea and North Atlantic Ocean were analyzed to evaluate changes in the seawater isotopic composition over time. We report an annual otolith δ13C record that documents the magnitude of the δ13C depletion in the Mediterranean Sea between 1989 and 2010. Atlantic bluefin tuna in our sample (n = 632) ranged from 1 to 22 years, and otolith material corresponding to the first year of life (back-calculated birth year) was used to reconstruct seawater isotopic composition. Otolith δ18O remained relatively stable between 1989 and 2010, whereas a statistically significant decrease in δ13C was detected across the time interval investigated, with a rate of decline of 0.05‰ yr-1 (-0.94‰ depletion throughout the recorded period). The depletion in otolith δ13C over time was associated with the oceanic uptake of anthropogenically derived CO2.. © 2016 Elsevier B.V.


Coelho R.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Infante P.,University of Évora | Santos M.N.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip
Fisheries Research | Year: 2013

At-haulback mortality of blue shark (Prionace glauca) captured by the Portuguese pelagic longline fishery targeting swordfish in the Atlantic was modeled. Data was collected by onboard fishery observers that monitored 762 fishing sets (1. 005. 486 hooks) and recorded information on 26. 383 blue sharks. The sample size distribution ranged from 40 to 305. cm fork length, with 13.3% of the specimens captured dead at-haulback. Data modeling was carried out with Generalized Linear Models (GLM) and Generalized Estimation Equations (GEE), given the fishery-dependent source of the data. The explanatory variables influencing blue shark mortality rates were year, specimen size, fishing location, sex, season and branch line material. Model diagnostics and validation were performed with residual analysis, the Hosmer-Lemeshow test, a receiver operating characteristic (ROC) curve, and a 10-fold cross validation procedure. One important conclusion of this study was that blue shark sizes are important predictors for estimating at-haulback mortality rates, with the probabilities of dying at-haulback decreasing with increasing specimen sizes. The effect in terms of odds-ratios are non-linear, with the changing odds-ratios of surviving higher for the smaller sharks (as sharks grow in size) and then stabilizing as sharks reach larger sizes. The models presented in this study seem valid for predicting blue shark at-haulback mortality in this fishery, and can be used by fisheries management organizations for assessing the efficacy of management and conservation initiatives for the species in the future. © 2013 Elsevier B.V.


Oliveira M.T.,Oceanario de Lisbon S.A. | Oliveira M.T.,University of Algarve | Ramos J.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Santos M.N.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip
Journal of Applied Ichthyology | Year: 2015

In the present paper there was a twofold hypothesis, i.e. that the deployment of artificial reefs adds value to natural features by diversifying diving sites and thus be a certain propensity concerning the type of added value (either of non-extractive direct or indirect use). Two vessels were used as artificial reefs off Sal Island (Cape Verde) in 2006 and 2008, with the aim of bolstering the local economy through ecotourism. The additional economic value anticipated was to: (i) enhance fish aggregation as well as other marine organisms, and (ii) mitigate human pressure on natural reefs by diverting divers. The supply-side view of diving trips was tested and analysed over a 4-year period (2008-2011) in the choice of divers between natural and artificial reefs, as well as such reef attributes as reef depth, reef distance from the main pier in Santa Maria Bay, and the year-season as well as combinations thereof. Data were also analysed to determine if the deployed reefs off Sal Island had a complementary or a substitute function. It was observed that the presence of artificial reefs created more dive users, but that divers who used these reefs were not deterred from diving at natural reefs. This resulted in a low-diversion effect (low substitutability). Thus, dive operators can offer additional options to divers (moderate to highly complementary). The distance to diving sites was the most influential factor in diving decisions (linear model results indicated 15 more divers at distances closer to Santa Maria Bay than elsewhere). From the log-linear model the number of divers would be expected to change, the distance being the most influential factor (11.7 times higher at closer sites); reef type and depth were less influential (0.2 times fewer divers at artificial reefs; 2.3 times more divers in shallower waters). Also apparent was that the depth of the reef was fundamental in the diver niche allocation throughout the seasons. © 2015 Blackwell Verlag GmbH.


Amorim S.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Santos M.N.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Coelho R.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Coelho R.,University of Algarve | And 2 more authors.
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2015

This paper reports the results of using different hook style and bait type combinations on the catches of targeted, bycatch and discarded fishes in the Portuguese commercial longline fishery targeting swordfish (Xiphias gladius) in the South Atlantic Ocean. In total, 310 longline experimental sets (446 400 hooks) were deployed between October 2008 and February 2012. Three different hook styles were tested; the traditional J-hook (9/0) 10o offset was compared with two 17/0 circle hooks (a non-offset and a 10o offset), and squid (Illex spp.) bait was compared with mackerel (Scomber spp.). Catch per unit effort (CPUE) was calculated for each fish species per fishing set and compared between the different hook style and bait type combinations. Results indicated that the effects of hook style and bait on the CPUEs were species-specific. For example, swordfish (target species, Xiphias gladius) CPUEs were higher with J-hooks baited with squid, while for the blue shark (most important bycatch species, Prionace glauca) the highest CPUEs were obtained with circle hooks baited with mackerel. For tuna (Thunnus spp.) and marlin (blue, Makaira nigricans and white, Kajikia albida) only the bait effect was significant, with higher catches with squid. For the discarded species, the proportions of alive vs dead specimens at the time of fishing gear retrieval were also species-specific. The total retained catch value per unit of effort (VPUE) did not changed between the different hook and bait combinations, but these VPUEs are highly dependent on market fluctuations. © 2015 John Wiley & Sons, Ltd.


Oliveira M.T.,Oceanario de Lisbon S.A. | Oliveira M.T.,University of Algarve | Santos M.N.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Coelho R.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | And 3 more authors.
Journal of Applied Ichthyology | Year: 2015

Summary: This study reports weight-length and length-length relationships for selected coastal reef fish species of the Cape Verde Archipelago (tropical north-eastern Atlantic). Specimens were caught with different types of gear (long-lines, hand-lines, purse-seines and traps) during commercial fishing activities and sampled during fish market operations. A total of 8328 individuals were sampled, representing 29 species from 14 Families. This study provides the first references on weight-length and length-length relationships for five and 23 fish species worldwide, for 10 and 24 species for the Eastern Atlantic and for 12 and 26 species for Cape Verde Archipelago, respectively. Additionally, it provides revised weight-length relationships for 11 species from Cape Verde waters. © 2014 Blackwell Verlag GmbH.


Coelho R.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Coelho R.,University of Algarve | Santos M.N.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Fernandez-Carvalho J.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | And 2 more authors.
Fisheries Research | Year: 2015

The interaction between tuna fisheries and sea turtles is commonly recognized as one of the major threats and causes for the decline of sea turtle populations. Within the tuna and swordfish fisheries, the incidental sea turtle bycatch is usually more frequent from longline fisheries targeting swordfish. Therefore it is important to test possible mitigation measures, particularly in areas where fishing activities and high abundance of these species overlaps, as is the case of the Tropical Northeast Atlantic Ocean. Between August 2008 and December 2011, a total of 202 experimental pelagic longline sets were carried out in that region (latitude: 11-22°N, longitude: 20-38°W). The aim was to test the effects of changing the traditional J-style hooks (10° offset) baited with squid used by the fishing industry, against two circle hooks (one non-offset and one with 10° offset) and mackerel bait. Four sea turtle species were captured, with the leatherback Dermochelys coriacea comprising most of the bycatches (BPUE, bycatch per unit of effort using the traditional configuration of 0.990 turtles/1000 hooks), followed by three hardshell species: the loggerhead Caretta caretta and the olive ridley Lepidochelys olivacea (BPUE. =. 0.165 turtles/1000 hooks), and the Kemp ridley Lepidochelys kempii (BPUE. =. 0.024 turtles/1000 hooks). In general, the sea turtle interactions in the fishery can be reduced by changing from the traditional gear to one of the experimental combinations. However, those reductions were species-specific, with the leatherback bycatches reduced only when changing from J-style to the non-offset circle hook, while for the hardshell turtles both the hook style (using a circle hook, with or without offset) and the bait (using mackerel) significantly reduced the incidental bycatches. Hooking location was also species-specific, with most hardshell specimens hooked by the mouth and esophagus, while leatherbacks were mostly hooked externally by the flippers. Most of the sea turtles were captured and released alive with the mortality rates independent of the hook style and bait type used. A reduction of 55% in leatherback incidental bycatches can be expected in this fishery by changing from J-style to circle hooks, whereas for the hardshell species a 50-59% reduction can be obtained by changing to circle hooks (respectively with and without offset), and a 55% reduction by using mackerel bait. © 2014 Elsevier B.V.


Fernandez-Carvalho J.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Fernandez-Carvalho J.,University of Algarve | Coelho R.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Coelho R.,University of Algarve | And 2 more authors.
Fisheries Research | Year: 2015

The incidental bycatch of sea turtle in tuna and swordfish fisheries is currently recognized as one of the major threats to the populations of these species. Therefore a number of mitigation measures have been tested, particularly for longline fisheries targeting swordfish. As mitigation measures may also affect the fish catches, it is important to quantify these impacts both at the ecological and socio-economic levels. Between August 2008 and December 2011, a total of 202 experimental pelagic longline sets were carried out in the Tropical Northeast Atlantic Ocean. The combination J-hook baited with squid (traditionally used by the fishery) was compared against two circle hooks (one non-offset and one with 10° offset) and mackerel bait. Catches per unit effort (CPUE) were calculated and compared between the different hook style and bait combinations for all target, bycatch and discarded fish species. In addition, a GLM (generalized linear model) was applied for swordfish Xiphias gladius and blue shark Prionace glauca (two main target species) and bigeye thresher Alopias superciliosus (most discarded species). The swordfish catches were negatively affected when changing from the traditional gear (J-style hooks baited with squid) to one of the experimental combinations, with the bait type having a stronger influence than the hook style on this reduction. However, the overall target species CPUE and the value of the retained catch (VPUE, value per unit of effort) were not significantly affected, due to an increase on the blue shark CPUE. Furthermore, the hook style and the bait type did not seem to influence the at-haulback mortality rates of most discarded species, which were highly species-specific. Given the apparent lack of impact on the overall value of the retained catch, the use of circle hooks baited with mackerel on this particular fishery and region would be highly beneficial for sea turtle conservation, without affecting the economic viability of the fishery. © 2014 Elsevier B.V.


Fernandez-Carvalho J.,University of Algarve | Coelho R.,University of Algarve | Santos M.N.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Amorim S.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip
Fisheries Research | Year: 2014

The incidental bycatch of sea turtle in tuna and swordfish fisheries is currently recognized as one of the major threats to the populations of these species. Therefore a number of mitigation measures have been tested, particularly for longline fisheries targeting swordfish. As mitigation measures may also affect the fish catches, it is important to quantify these impacts both at the ecological and socio-economic levels. Between August 2008 and December 2011, a total of 202 experimental pelagic longline sets were carried out in the Tropical Northeast Atlantic Ocean. The combination J-hook baited with squid (traditionally used by the fishery) was compared against two circle hooks (one non-offset and one with 10° offset) and mackerel bait. Catches per unit effort (CPUE) were calculated and compared between the different hook style and bait combinations for all target, bycatch and discarded fish species. In addition, a GLM (generalized linear model) was applied for swordfish Xiphias gladius and blue shark Prionace glauca (two main target species) and bigeye thresher Alopias superciliosus (most discarded species). The swordfish catches were negatively affected when changing from the traditional gear (J-style hooks baited with squid) to one of the experimental combinations, with the bait type having a stronger influence than the hook style on this reduction. However, the overall target species CPUE and the value of the retained catch (VPUE, value per unit of effort) were not significantly affected, due to an increase on the blue shark CPUE. Furthermore, the hook style and the bait type did not seem to influence the at-haulback mortality rates of most discarded species, which were highly species-specific. Given the apparent lack of impact on the overall value of the retained catch, the use of circle hooks baited with mackerel on this particular fishery and region would be highly beneficial for sea turtle conservation, without affecting the economic viability of the fishery. © 2014 Elsevier B.V.


Santos M.N.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Coelho R.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Fernandez-Carvalho J.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip | Amorim S.,Instituto Portugues Do Mar E Da Atmosfera Ipma Ip
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2013

The incidental catch of marine turtles is a major problem in commercial pelagic longline fisheries. The present paper reports marine turtle bycatch composition and rates from a Portuguese commercial longline fishery targeting swordfish in the South Atlantic, and investigates the effects of changes in hook style and bait type. In total, 310 longline sets were carried out between 2008 and 2012. Three different hook styles were tested, traditional J hook (9/0) and two 17/0 circle hooks (a non-offset and a 10o offset), but only one bait type was used in each set (Scomber spp. or Illex spp.). Two species of sea turtles were caught, the leatherback Dermochelys coriacea, and the loggerhead Caretta caretta, the latter comprising the majority of the catches. The highest mean bycatch per unit of effort values for both species combined (1.693/1000 hooks) and for the individual species (1.505/1000 hooks for loggerheads) occurred with J-style hooks baited with squid. Changing from J-style to one of the circle hooks was only significant when using squid bait (with the odds-ratios decreasing between 54% and 63%). Hooking location was species-specific, with most loggerheads hooked by the mouth, while leatherbacks were mostly hooked externally by the flippers. Overall, 65% of all sea turtles were released alive (85% for leatherbacks compared with 63% for loggerheads). Significant reduction of sea turtle accidental catches on the swordfish longline fisheries can be achieved by changing the J hooks to circle hooks, especially if baited with mackerel. However, such gain is species-specific and area dependent. © 2013 John Wiley & Sons, Ltd.

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