– The Portuguese coast is particularly adequate for studies on the impact of climate change on fi... more – The Portuguese coast is particularly adequate for studies on the impact of climate change on fisheries, as it has faced an increase in both air and sea surface temperature and a decrease in intensity and frequency of rainfall. Ecological responses to climate change have already been observed in Portuguese waters, with consequences in fisheries. Regional climate models have predicted a further decrease in rainfall in Portugal by the end of the century, which will have a strong impact on the runoff into coastal areas. River drainage affects the physical, chemical and biological properties of coastal ecosystems, regulating habitat availability and favouring their productivity. The present study analysed the influence of river drainage on landings of coastal ports in the vicinity of four hydrologically distinct estuaries. Unlike previous results obtained for the Mediterranean, no significant relationships between river drainage and landings were found. Relationships between drainage and landings can be inconsistent among regions and dependent on how strongly a food web relies on nutrients and organic matter of river origin. In the Portuguese coast, an upwelling regime is of particular importance for the richness and diversity of the coastal ecosystem and for fisheries. The complexity of the coastal upwelling phenomenon together with a possible interaction of several other smaller scale factors acting on recruitment of commercial species may mask the effects of river drainage on landings. Nevertheless, as accentuated decreases in rainfall have been predicted for Portugal, the resulting reduction in river drainage may still strongly impact fisheries in the future.
The brown-shrimp beam trawl fishery carried out within the Tagus estuary produces discards due to... more The brown-shrimp beam trawl fishery carried out within the Tagus estuary produces discards due to the little commercial interest of most of the species caught. Between 1994 and 1996, monthly samples were collected in the two major fishing areas within the Tagus estuary, using a beam trawl, in order to estimate the amount of fish and crustaceans caught per unit of effort. The fishing effort of the commercial fleet was determined based on surveys of professional fishermen. Mortality estimates of discards were also evaluated experimentally. The main fish and crustacean species discarded after capture were Crangon crangon (Linnaeus, 1758), Liza ramada (Risso, 1826), Carcinus maenas (Linnaues, 1758) and Pomatoschistus minutus (Pallas, 1770). The estimated total amount of fishery discards in the upper part of the Tagus estuary is approximately 1500 tonnes per year, which represents ca. 90% of the captures. The mortality rate of the fishes and crustaceans discarded varied according to species and season, with the highest rates during Summer months. Considering nitrogen and carbon content of the main discarded species, an input of particulate organic matter of more than 140 tonnes of carbon and 35 tonnes of nitrogen per year were estimated for these estuarine areas.
Portugal is the third highest per capita consumer of fish in the world, with a fishing fleet cons... more Portugal is the third highest per capita consumer of fish in the world, with a fishing fleet consisting of trawlers, purse-seiners and multi-gear vessels, which use a wide variety of fishing gears, such as gillnets, trammel nets, longlines or traps. Climate change affects ocean conditions, impacting marine organisms and ecosystems, with consequences for marine fisheries. The consequences of climate change on fishing communities will depend on their exposure to this factor, the sensitivity of target species and ecosys- tems to climate change and fishermen’s ability to adapt to climate change. The Portuguese coast is mainly north-south oriented and located in a biogeographic transition zone, between temperate and subtrop- ical waters, where the northern or southern distribution limits of several species can be found. Also, the Portuguese coast is expected to suffer changes in temperature and precipitation more accelerated than the global mean alteration rate, which makes it particularly adequate for studies of the effect of climate change on coastal communities and fisheries. The present study analysed trends in landings of the most important fishing métiers in the Portuguese coast and the vulnerability and adaptation capacity of Portuguese fisheries to climate change. Official Portuguese landings (1992–2012) were analysed and a survey was conducted to assess fishermen’s perception of landings and their potential behaviour in response to the effects of climate change on fisheries. Eighteen new species were landed in Portuguese fisheries over the past 5 years, of which 12 were tropical or subtropical and 5 had their distribution limit along the Portuguese coast. A latitudinal pattern in the number of new species in landings was found, agreeing with a northward shift of subtropical species. The south coast has shown a higher vulnerability to climate change, in terms of both exposure and sensitivity of target species and ecosystems to its effects. Trawlermen may be more adaptable and less vulnerable to climate change, given the high mobility of their fleet. Multi-gear fisheries may be more flexible in changing target species or fishing gear, which makes them potentially less vulnerable to climate change. On the other hand, the high sensitivity of sardine to the effects of climate change makes the purse-seine fisheries particularly vulnerable to climate change.
Small pelagic fishes are particularly abundant in areas with high environmental variability (zone... more Small pelagic fishes are particularly abundant in areas with high environmental variability (zones of coastal upwelling and areas of tidal mixing and river dis- charge), and because of this, their abundance suffers large inter-annual and inter-decadal fluctuations. In Portugal, the most important species in terms of landings are European sardine, Atlantic horse mackerel and Atlantic chub mack- erel. Small pelagic fish landings account for 62.8 % of the total fish biomass and represent 32.7 % of the economical value of all catches. We have investigated trends in land- ings of these small pelagic fishes and detected the effects of environmental factors in this fishery. In order to explain the variability of landings of small pelagic fishes, we have used official landings (1965–2012) for trawling and purse seine fisheries and applied generalized linear models, using the North Atlantic Oscillation index (NAO) (annual and winter NAO index), sea surface temperature (SST), wind data (strength and North–South and East–West wind compo- nents) and rainfall, as explanatory variables. Regression analysis was used to describe the relationship between landings and SST. The models explained between 50.16 and 51.07 % of the variability of the LPUE, with the most important factors being winter NAO index, SST and wind strength. The LPUE of European sardine and Atlantic horse mackerel was negatively correlated with SST, and LPUE of Atlantic chub mackerel was positively correlated with SST. The use of landings of three important species of small pelagic fishes allowed the detection of variations in land- ings associated with changes in sea water temperature and NAO index.
Climate change affects ocean conditions, which will in turn impact marine organisms and ecosystem... more Climate change affects ocean conditions, which will in turn impact marine organisms and ecosystems, with consequences for fisheries. The Iberian Peninsula has faced an increase in both air and sea surface temperature, and rainfall has decreased in intensity and frequency in Portugal. As Portugal is the third highest per capita consumer of fish in the world and its coast is located in a biogeographic transition zone, between temperate and subtropical waters, the study of the effects of climate change on Portuguese fisheries is of the utmost importance. The present work focused on Setúbal, an important fishing port in central Portugal. Landings Per Unit of Effort (LPUE) time series (1927–2012) of the most important species were analysed and their relationships with sea surface temperature (SST), rainfall and the winter North Atlantic Oscillation (NAO) index were investigated. Mean annual SST has increased 0.9 ◦C from 1926 to 2012. The main target species in 2012 were the same as in 1927. However, their landings have changed and have responded to changes in environmental variables, particularly SST. LPUE of the European sardine has shown a decreasing trend and was negatively correlated with SST and NAO, whereas the LPUE of the Atlantic chub mackerel has been increasing since 2000. The LPUE of the common cuttlefish has kept more or less stable through the studied time series, but it was correlated with SST. The LPUE of soles has increased with time and SST. The LPUE of the common octopus was correlated with SST and NAO and has presented higher values since 1975. Further increases in sea temperature in the future will pose challenges for fisheries in Setúbal. Purse-seine fisheries may try to compensate the expected losses in sardine landings by targeting the chub mackerel. Although landings of the most important species in multi-gear fisheries seem to have been favoured by increases in temperature, further studies on the tolerance of each particular species to increases in temperature are needed. As a recent increase in the relative importance of subtropical species in Portuguese fisheries has already been previously detected, climate change may also bring new fishing opportunities for this region.
Trends in annual catches of fish species in the large marine ecosystems (LMEs) of the world were ... more Trends in annual catches of fish species in the large marine ecosystems (LMEs) of the world were analysed, relating them with changes in sea surface temperature. LMEs are large coastal areas with broad ecosystem similarities, and the vast majority of them have warmed in the period of 1982–2006. Changes in sea water temperature, induced by climate change, affect the geographic distribution of fish species in marine ecosystems. Shifts in distribution of fish will most likely affect the abundance, distribution and composition of fisheries catches. In the present paper, a decreasing trend in the catches of fish species in warming LMEs was observed. Catches in years of cold and warm winters were compared for each of the eight fish species most caught in the world. Generally, mean catches of polar and temperate species were higher in years of warm winters in the LMEs located in the northern part of the species range and in years of cold winters in LMEs of the southern regions of their ranges. Mean catches of subtropical species were higher in cold years in LMEs of lower latitudes and in warm years in LMEs of higher latitude regions. The results obtained for fish catches agree with a poleward shift of fish species as a response to ocean warming, posing challenges for future fisheries management.
Fisheries are an important source of food, with a high economic value and social significance. Th... more Fisheries are an important source of food, with a high economic value and social significance. The present worrying situation of the world fisheries is the result of the interaction between different factors (e.g. climatic variations, natural oscillations, technological innovation), but the greatest challenges are overfishing and climate change. The species richness of the Portuguese coast is generally higher than that found in northern Europe and similar to that of the Mediterranean, since many species have their southern or northern distribution limits along the Portuguese coast. The zoogeographic importance of this latitudinal area has long been recognized, representing the transition between north-eastern Atlantic warm-temperate and cold-temperate regions, which makes the Portuguese coast an area of great sensitivity to the detection of climate change. Official landing data for commercial species that have the Portuguese coast as their distribution limit were analysed together with sea surface temperature for the period of 1927–2011. In general, landings of species with affinity for temperate waters presented a decreasing trend, whereas species with affinity for subtropical/tropical waters showed an increasing trend. These variations were associated with variation in temperature: lower landings of temperate species occurred mainly in warm years, whereas landings of subtropical/tropical species presented an opposite trend, with higher landings in warm years. Preparing for the impacts of climate change is crucial for the sustainability of fisheries. Management should take into consideration information about environmental factors that affect species distribution and abundance.
For each Portuguese fleet component, landings of biogeographic groups of fish species were compar... more For each Portuguese fleet component, landings of biogeographic groups of fish species were compared for the period of 1993–2009. Wide-distribution species were the most abundant in landings, but have shown a decreasing trend. Temperate species had higher landings in trawl fisheries, whereas subtropical species were most abundant and exhibiting an increasing trend in landings of multi-gear fisheries. A latitudinal gradient was observed, with landings of temperate species being more important in the North-western coast than in the South-western and South coasts. Although trawl fisheries were relatively more important in the North-western coast, there has been a recent increase in the relative importance of multi-gear fisheries and of subtropical species in this area. The increasing relative importance of subtropical species in Portuguese fisheries along with the fact that landings of subtropical species were higher in multi-gear fisheries could indicate an easier adaptation of Portuguese multi-gear fisheries to the effects of climate change. However, as multi-gear fisheries include a wide range of gears, techniques and target-species, they may not all respond in the same manner to changes in fish species’ distribution. Among multi-gear fisheries, trammel nets catch a wider variety of species and a wider size range than gill nets or longlines; thus, trammel net fishers can adapt to changes in abundance of the main target species more readily than those using more species- and size-specific gears. Therefore, trammel net fisheries could more easily adapt to the effects of climate change on fish distribution than gill net or longline fisheries.
Multimetric fish-based indices have been increasingly gaining importance in Europe, as the Water ... more Multimetric fish-based indices have been increasingly gaining importance in Europe, as the Water Framework Directive (WFD) requires fish fauna, and particularly its composition and abundance, to be taken into account in the assessment of the ecological quality of continental surface waters, including transitional waters. These indices are composed of several metrics, mostly related with structural and functional characteristics of fish communities, such as species richness, the role of nursery areas, or trophic web structure. Therefore, ecological quality assessments should ensure that these structural and functional characteristics of fish communities were covered by the sampling methods used. In the present work, the influence of sampling effort on several metrics of the Estuarine Fish Assessment Index (EFAI) was studied. Pseudo-random samples were generated from data of four Portuguese estuaries and bootstrap cycles were performed, in order to obtain metrics’ means and standard deviations per number of hauls analysed. The number of hauls necessary for the means to level off differed with the metrics considered. Generally, for metrics on percentages (percentage of marine migrants, percentage of estuarine residents and percentage of piscivores) the curve levelled off with less than 20 hauls, both for the estuary as a whole and for different estuarine salinity zones. On the other hand, metrics on species richness required much larger samples. In order to decrease to −5% the current estimated bias of metrics, the WFD sampling costs would have to be more than 3 times higher than they currently are. The findings in the present study are of great importance for an effective assessment of estuarine ecological quality and particularly in the context of the WFD, as the metrics studied are common to other Member State indices.► Study of the influence of sampling effort on metrics of a fish-based index. ► Pseudo-random samples were generated from data of four Portuguese estuaries. ► For metrics on percentages, the means levelled off with less than 20 hauls. ► Metrics on species richness required much larger samples ► solutions alternative to increasing the sampling effort are suggested.
Other uses, including reproduction and distribution, or selling or licensing copies, or posting t... more Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited.
Community-based responses of fish fauna to anthropogenic pressures have been extensively used to ... more Community-based responses of fish fauna to anthropogenic pressures have been extensively used to assess the ecological quality of estuarine ecosystems. Several methodologies have been developed recently combining metrics reflecting community structure and function. A fish community facing significant environmental disturbances will be characterized by a simplified structure, with lower diversity and complexity. However, estuaries are naturally dynamic ecosystems exposed to numerous human pressures, making it difficult to distinguish between natural and anthropogenic-induced changes to the biological community. In the present work, the variability of several fish metrics was assessed in relation to different pressures in estuarine sites. The response of a multimetric index (Estuarine Fish Assessment Index) was also analysed. Overall, fish metrics and the multimetric index signalled anthropogenic stress, particularly environmental chemical pollution. The fish assemblage associated with this type of pressure was characterized by lower species diversity, lower number of functional guilds, lower abundance of marine migrants and of piscivorous individuals, and higher abundance of estuarine resident species. A decreased ecological quality status, based on the EFAI, was also determined for sites associated with this pressure group. Ultimately, the definition of each pressure groups favoured a stressor-specific analysis, evidencing pressure patterns and accounting for multiple factors in a highly dynamic environment.
The assessment of water quality has changed markedly worldwide over the last years, especially in... more The assessment of water quality has changed markedly worldwide over the last years, especially in Europe due to the implementation of the Water Framework Directive. Fish was considered a key-element in this context and several fish-based multi-metric indices have been proposed. In this study, we propose a multi-metric index, the Estuarine Fish Assessment Index (EFAI), developed for Portuguese estuaries, designed for the overall assessment of transitional waters, which could also be applied at the water body level within an estuary. The EFAI integrates seven metrics: species richness, percentage of marine migrants, number of species and abundance of estuarine resident species, number of species and abundance of piscivorous species, status of diadromous species, status of introduced species and status of disturbance sensitive species. Fish sampling surveys were conducted in 2006, 2009 and 2010, using beam trawl, in 13 estuarine systems along the Portuguese coast. Most of the metrics presented a high variability among the transitional systems surveyed. According to the EFAI values, Portuguese estuaries presented a “Good” water quality status (except the Douro in a particular year). The assessments in different years were generally concordant, with a few exceptions. The relationship between the EFAI and the Anthropogenic Pressure Index (API) was not significant, but a negative and significant correlation was registered between the EFAI and the expert judgement pressure index, at both estuary and water body level. The ordination analysis performed to evaluate similarities among North-East Atlantic Geographical Intercalibration Group (NEAGIG) fish-based indices put in evidence four main groups: the French index, since it is substantially different from all the other indices (uses only four metrics based on densities); indices from Ireland, United Kingdom and Spain (Astúrias and Cantábria); the Dutch and German indices; and the indices of Belgium, Portugal and Spain (Basque country). The need for detailed studies, including comparative approaches, on several aspects of these assessment tools, especially in what regards their response to anthropogenic pressures was stressed.
Fish-based indices are becoming important bioassessment tools for estuaries since the European Wa... more Fish-based indices are becoming important bioassessment tools for estuaries since the European Water Framework Directive included fish as a biological quality element to be monitored for the assessment of ecological status of those systems. In particular, data on species composition and abundance of the ichthyofauna must be used to evaluate the ecological status of European estuaries, but other factors like measures of fish health are also considered important metrics. These indicators of fish health include infections by parasites. The common goby, Pomastoschistus microps, and the Lusitanian toadfish, Halobatrachus didactylus, are fairly sedentary fish, very abundant in Portuguese estuaries, and were used to investigate if parasitism in fishes in transitional waters is a good metric to reflect anthropogenic impacts in the environment. No significant relationships were observed between the parasite levels in these two species and the intensity of human pressures, either at a large or small spatial scale. Results obtained also are contrary to the generalized idea that a higher proportion of parasitized fish necessarily reflects a decrease in their condition as a result of habitat degradation. A high degree of temporal and ontogenetic variability in the parasite levels of both P. microps and H. didactylus was detected, which make it difficult to establish the scores for this hypothetical metric even if significant relationships between parasite levels and human pressures are identified in the future. Therefore, the present work does not uphold the hypothesis that parasitism in fish is a good metric to assess ecological water quality in transitional waters.
According to the Water Framework Directive (WFD) transitional waters should be differentiated acc... more According to the Water Framework Directive (WFD) transitional waters should be differentiated according to type and, in some cases, divided into different water bodies. This raises a dilemma in trying to define parts of a continuum. In the sequence of WFD several indices have been proposed including the Estuarine Fish Assessment Index, which can be applied taking an estuary as a whole (EFAI – without water bodies division) or divided in water bodies (EFAIWB). The purpose of this work is to analyze the robustness of the Estuarine Fish Assessment Index, based on three different ways of dividing Portuguese estuaries into water bodies according to different criteria (criterion 1 – distance to the estuary mouth, criterion 2 – salinity and criterion 3 – morphology, salinity and human dimension as pressure and state). In this study we evaluated at which degree these three criteria could influence the ecological quality ratio (EQR) results, when the index was applied to water body level (EFAIWB). Also, for each estuary, the EQRWB results for each criterion of EFAIWB were combined and weighted according to the water bodies areas (EFAI overall weighted – EFAIOW). Finally, it was compared if the results obtained for each criterion with the EFAIOW were similar to the results of the index application taking the estuary as a whole (EFAI – without water bodies division). No significant differences were found in both cases, which indicated that this index is a robust method regarding the division of the estuaries in different water bodies, which is an important element of a fish-based multimetric tool for assessing estuarine ecological quality. However, in some cases, different ecological quality statuses were achieved when applying the EFAIOW or the EFAI. This work addressed several aspects regarding the possible division of water bodies at the WFD context.
Beam trawling results in large amounts of discards. Discards mortality may be influenced by some ... more Beam trawling results in large amounts of discards. Discards mortality may be influenced by some of the procedures aboard fishing vessels. In the present study, the influence of temperature of the sorting containers, of sorting time and of haul duration on the mortality of brown-shrimp discards from the beam trawl fishery in the Tagus estuary was evaluated. Experiments were conducted in the summer and in the winter of 2000, simulating on-board procedures, in different conditions. The sorting containers were either wooden, plastic or metallic, dark or light-coloured, and two sorting times (5 and 10 min) and three haul durations (10, 20 and 30 min) were considered. The light-coloured wooden and plastic containers presented the lowest temperatures, whereas the highest one was measured on the dark metallic container. For temperatures between 10 and 20 °C, mortality was nil; for values higher than 20 °C, mortality was high, reaching 96% in the temperature interval 40–50 °C. Discards mortality was similar for both sorting times considered. The mortality of discards increased with longer haul duration; for 10 min, mean mortality was 7%, whereas for 30 min was 75%. The use of light-coloured wooden or plastic sorting containers in summer and the avoidance of fishing activities at the hottest times of day in this season are suggested as management measures to minimise discards mortality in beam trawl fisheries.
The brown-shrimp beam trawl fishery carried out within the Tagus estuary produces discards due to... more The brown-shrimp beam trawl fishery carried out within the Tagus estuary produces discards due to the little commercial interest of most of the species caught. Between 1994 and 1996, monthly samples were collected in the two major fishing areas within the Tagus estuary, using a beam trawl, in order to estimate the amount of fish and crustaceans caught per unit of effort. The fishing effort of the commercial fleet was determined based on surveys of professional fishermen. Mortality estimates of discards were also evaluated experimentally. The main fish and crustacean species discarded after capture were Crangon crangon (Linnaeus, 1758), Liza ramada (Risso, 1826), Carcinus maenas (Linnaues, 1758) and Pomatoschistus minutus (Pallas, 1770). The estimated total amount of fishery discards in the upper part of the Tagus estuary is approximately 1500 tonnes per year, which represents ca. 90% of the captures. The mortality rate of the fishes and crustaceans discarded varied according to species and season, with the highest rates during Summer months. Considering nitrogen and carbon content of the main discarded species, an input of particulate organic matter of more than 140 tonnes of carbon and 35 tonnes of nitrogen per year were estimated for these estuarine areas.
– The Portuguese coast is particularly adequate for studies on the impact of climate change on fi... more – The Portuguese coast is particularly adequate for studies on the impact of climate change on fisheries, as it has faced an increase in both air and sea surface temperature and a decrease in intensity and frequency of rainfall. Ecological responses to climate change have already been observed in Portuguese waters, with consequences in fisheries. Regional climate models have predicted a further decrease in rainfall in Portugal by the end of the century, which will have a strong impact on the runoff into coastal areas. River drainage affects the physical, chemical and biological properties of coastal ecosystems, regulating habitat availability and favouring their productivity. The present study analysed the influence of river drainage on landings of coastal ports in the vicinity of four hydrologically distinct estuaries. Unlike previous results obtained for the Mediterranean, no significant relationships between river drainage and landings were found. Relationships between drainage and landings can be inconsistent among regions and dependent on how strongly a food web relies on nutrients and organic matter of river origin. In the Portuguese coast, an upwelling regime is of particular importance for the richness and diversity of the coastal ecosystem and for fisheries. The complexity of the coastal upwelling phenomenon together with a possible interaction of several other smaller scale factors acting on recruitment of commercial species may mask the effects of river drainage on landings. Nevertheless, as accentuated decreases in rainfall have been predicted for Portugal, the resulting reduction in river drainage may still strongly impact fisheries in the future.
The brown-shrimp beam trawl fishery carried out within the Tagus estuary produces discards due to... more The brown-shrimp beam trawl fishery carried out within the Tagus estuary produces discards due to the little commercial interest of most of the species caught. Between 1994 and 1996, monthly samples were collected in the two major fishing areas within the Tagus estuary, using a beam trawl, in order to estimate the amount of fish and crustaceans caught per unit of effort. The fishing effort of the commercial fleet was determined based on surveys of professional fishermen. Mortality estimates of discards were also evaluated experimentally. The main fish and crustacean species discarded after capture were Crangon crangon (Linnaeus, 1758), Liza ramada (Risso, 1826), Carcinus maenas (Linnaues, 1758) and Pomatoschistus minutus (Pallas, 1770). The estimated total amount of fishery discards in the upper part of the Tagus estuary is approximately 1500 tonnes per year, which represents ca. 90% of the captures. The mortality rate of the fishes and crustaceans discarded varied according to species and season, with the highest rates during Summer months. Considering nitrogen and carbon content of the main discarded species, an input of particulate organic matter of more than 140 tonnes of carbon and 35 tonnes of nitrogen per year were estimated for these estuarine areas.
Portugal is the third highest per capita consumer of fish in the world, with a fishing fleet cons... more Portugal is the third highest per capita consumer of fish in the world, with a fishing fleet consisting of trawlers, purse-seiners and multi-gear vessels, which use a wide variety of fishing gears, such as gillnets, trammel nets, longlines or traps. Climate change affects ocean conditions, impacting marine organisms and ecosystems, with consequences for marine fisheries. The consequences of climate change on fishing communities will depend on their exposure to this factor, the sensitivity of target species and ecosys- tems to climate change and fishermen’s ability to adapt to climate change. The Portuguese coast is mainly north-south oriented and located in a biogeographic transition zone, between temperate and subtrop- ical waters, where the northern or southern distribution limits of several species can be found. Also, the Portuguese coast is expected to suffer changes in temperature and precipitation more accelerated than the global mean alteration rate, which makes it particularly adequate for studies of the effect of climate change on coastal communities and fisheries. The present study analysed trends in landings of the most important fishing métiers in the Portuguese coast and the vulnerability and adaptation capacity of Portuguese fisheries to climate change. Official Portuguese landings (1992–2012) were analysed and a survey was conducted to assess fishermen’s perception of landings and their potential behaviour in response to the effects of climate change on fisheries. Eighteen new species were landed in Portuguese fisheries over the past 5 years, of which 12 were tropical or subtropical and 5 had their distribution limit along the Portuguese coast. A latitudinal pattern in the number of new species in landings was found, agreeing with a northward shift of subtropical species. The south coast has shown a higher vulnerability to climate change, in terms of both exposure and sensitivity of target species and ecosystems to its effects. Trawlermen may be more adaptable and less vulnerable to climate change, given the high mobility of their fleet. Multi-gear fisheries may be more flexible in changing target species or fishing gear, which makes them potentially less vulnerable to climate change. On the other hand, the high sensitivity of sardine to the effects of climate change makes the purse-seine fisheries particularly vulnerable to climate change.
Small pelagic fishes are particularly abundant in areas with high environmental variability (zone... more Small pelagic fishes are particularly abundant in areas with high environmental variability (zones of coastal upwelling and areas of tidal mixing and river dis- charge), and because of this, their abundance suffers large inter-annual and inter-decadal fluctuations. In Portugal, the most important species in terms of landings are European sardine, Atlantic horse mackerel and Atlantic chub mack- erel. Small pelagic fish landings account for 62.8 % of the total fish biomass and represent 32.7 % of the economical value of all catches. We have investigated trends in land- ings of these small pelagic fishes and detected the effects of environmental factors in this fishery. In order to explain the variability of landings of small pelagic fishes, we have used official landings (1965–2012) for trawling and purse seine fisheries and applied generalized linear models, using the North Atlantic Oscillation index (NAO) (annual and winter NAO index), sea surface temperature (SST), wind data (strength and North–South and East–West wind compo- nents) and rainfall, as explanatory variables. Regression analysis was used to describe the relationship between landings and SST. The models explained between 50.16 and 51.07 % of the variability of the LPUE, with the most important factors being winter NAO index, SST and wind strength. The LPUE of European sardine and Atlantic horse mackerel was negatively correlated with SST, and LPUE of Atlantic chub mackerel was positively correlated with SST. The use of landings of three important species of small pelagic fishes allowed the detection of variations in land- ings associated with changes in sea water temperature and NAO index.
Climate change affects ocean conditions, which will in turn impact marine organisms and ecosystem... more Climate change affects ocean conditions, which will in turn impact marine organisms and ecosystems, with consequences for fisheries. The Iberian Peninsula has faced an increase in both air and sea surface temperature, and rainfall has decreased in intensity and frequency in Portugal. As Portugal is the third highest per capita consumer of fish in the world and its coast is located in a biogeographic transition zone, between temperate and subtropical waters, the study of the effects of climate change on Portuguese fisheries is of the utmost importance. The present work focused on Setúbal, an important fishing port in central Portugal. Landings Per Unit of Effort (LPUE) time series (1927–2012) of the most important species were analysed and their relationships with sea surface temperature (SST), rainfall and the winter North Atlantic Oscillation (NAO) index were investigated. Mean annual SST has increased 0.9 ◦C from 1926 to 2012. The main target species in 2012 were the same as in 1927. However, their landings have changed and have responded to changes in environmental variables, particularly SST. LPUE of the European sardine has shown a decreasing trend and was negatively correlated with SST and NAO, whereas the LPUE of the Atlantic chub mackerel has been increasing since 2000. The LPUE of the common cuttlefish has kept more or less stable through the studied time series, but it was correlated with SST. The LPUE of soles has increased with time and SST. The LPUE of the common octopus was correlated with SST and NAO and has presented higher values since 1975. Further increases in sea temperature in the future will pose challenges for fisheries in Setúbal. Purse-seine fisheries may try to compensate the expected losses in sardine landings by targeting the chub mackerel. Although landings of the most important species in multi-gear fisheries seem to have been favoured by increases in temperature, further studies on the tolerance of each particular species to increases in temperature are needed. As a recent increase in the relative importance of subtropical species in Portuguese fisheries has already been previously detected, climate change may also bring new fishing opportunities for this region.
Trends in annual catches of fish species in the large marine ecosystems (LMEs) of the world were ... more Trends in annual catches of fish species in the large marine ecosystems (LMEs) of the world were analysed, relating them with changes in sea surface temperature. LMEs are large coastal areas with broad ecosystem similarities, and the vast majority of them have warmed in the period of 1982–2006. Changes in sea water temperature, induced by climate change, affect the geographic distribution of fish species in marine ecosystems. Shifts in distribution of fish will most likely affect the abundance, distribution and composition of fisheries catches. In the present paper, a decreasing trend in the catches of fish species in warming LMEs was observed. Catches in years of cold and warm winters were compared for each of the eight fish species most caught in the world. Generally, mean catches of polar and temperate species were higher in years of warm winters in the LMEs located in the northern part of the species range and in years of cold winters in LMEs of the southern regions of their ranges. Mean catches of subtropical species were higher in cold years in LMEs of lower latitudes and in warm years in LMEs of higher latitude regions. The results obtained for fish catches agree with a poleward shift of fish species as a response to ocean warming, posing challenges for future fisheries management.
Fisheries are an important source of food, with a high economic value and social significance. Th... more Fisheries are an important source of food, with a high economic value and social significance. The present worrying situation of the world fisheries is the result of the interaction between different factors (e.g. climatic variations, natural oscillations, technological innovation), but the greatest challenges are overfishing and climate change. The species richness of the Portuguese coast is generally higher than that found in northern Europe and similar to that of the Mediterranean, since many species have their southern or northern distribution limits along the Portuguese coast. The zoogeographic importance of this latitudinal area has long been recognized, representing the transition between north-eastern Atlantic warm-temperate and cold-temperate regions, which makes the Portuguese coast an area of great sensitivity to the detection of climate change. Official landing data for commercial species that have the Portuguese coast as their distribution limit were analysed together with sea surface temperature for the period of 1927–2011. In general, landings of species with affinity for temperate waters presented a decreasing trend, whereas species with affinity for subtropical/tropical waters showed an increasing trend. These variations were associated with variation in temperature: lower landings of temperate species occurred mainly in warm years, whereas landings of subtropical/tropical species presented an opposite trend, with higher landings in warm years. Preparing for the impacts of climate change is crucial for the sustainability of fisheries. Management should take into consideration information about environmental factors that affect species distribution and abundance.
For each Portuguese fleet component, landings of biogeographic groups of fish species were compar... more For each Portuguese fleet component, landings of biogeographic groups of fish species were compared for the period of 1993–2009. Wide-distribution species were the most abundant in landings, but have shown a decreasing trend. Temperate species had higher landings in trawl fisheries, whereas subtropical species were most abundant and exhibiting an increasing trend in landings of multi-gear fisheries. A latitudinal gradient was observed, with landings of temperate species being more important in the North-western coast than in the South-western and South coasts. Although trawl fisheries were relatively more important in the North-western coast, there has been a recent increase in the relative importance of multi-gear fisheries and of subtropical species in this area. The increasing relative importance of subtropical species in Portuguese fisheries along with the fact that landings of subtropical species were higher in multi-gear fisheries could indicate an easier adaptation of Portuguese multi-gear fisheries to the effects of climate change. However, as multi-gear fisheries include a wide range of gears, techniques and target-species, they may not all respond in the same manner to changes in fish species’ distribution. Among multi-gear fisheries, trammel nets catch a wider variety of species and a wider size range than gill nets or longlines; thus, trammel net fishers can adapt to changes in abundance of the main target species more readily than those using more species- and size-specific gears. Therefore, trammel net fisheries could more easily adapt to the effects of climate change on fish distribution than gill net or longline fisheries.
Multimetric fish-based indices have been increasingly gaining importance in Europe, as the Water ... more Multimetric fish-based indices have been increasingly gaining importance in Europe, as the Water Framework Directive (WFD) requires fish fauna, and particularly its composition and abundance, to be taken into account in the assessment of the ecological quality of continental surface waters, including transitional waters. These indices are composed of several metrics, mostly related with structural and functional characteristics of fish communities, such as species richness, the role of nursery areas, or trophic web structure. Therefore, ecological quality assessments should ensure that these structural and functional characteristics of fish communities were covered by the sampling methods used. In the present work, the influence of sampling effort on several metrics of the Estuarine Fish Assessment Index (EFAI) was studied. Pseudo-random samples were generated from data of four Portuguese estuaries and bootstrap cycles were performed, in order to obtain metrics’ means and standard deviations per number of hauls analysed. The number of hauls necessary for the means to level off differed with the metrics considered. Generally, for metrics on percentages (percentage of marine migrants, percentage of estuarine residents and percentage of piscivores) the curve levelled off with less than 20 hauls, both for the estuary as a whole and for different estuarine salinity zones. On the other hand, metrics on species richness required much larger samples. In order to decrease to −5% the current estimated bias of metrics, the WFD sampling costs would have to be more than 3 times higher than they currently are. The findings in the present study are of great importance for an effective assessment of estuarine ecological quality and particularly in the context of the WFD, as the metrics studied are common to other Member State indices.► Study of the influence of sampling effort on metrics of a fish-based index. ► Pseudo-random samples were generated from data of four Portuguese estuaries. ► For metrics on percentages, the means levelled off with less than 20 hauls. ► Metrics on species richness required much larger samples ► solutions alternative to increasing the sampling effort are suggested.
Other uses, including reproduction and distribution, or selling or licensing copies, or posting t... more Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited.
Community-based responses of fish fauna to anthropogenic pressures have been extensively used to ... more Community-based responses of fish fauna to anthropogenic pressures have been extensively used to assess the ecological quality of estuarine ecosystems. Several methodologies have been developed recently combining metrics reflecting community structure and function. A fish community facing significant environmental disturbances will be characterized by a simplified structure, with lower diversity and complexity. However, estuaries are naturally dynamic ecosystems exposed to numerous human pressures, making it difficult to distinguish between natural and anthropogenic-induced changes to the biological community. In the present work, the variability of several fish metrics was assessed in relation to different pressures in estuarine sites. The response of a multimetric index (Estuarine Fish Assessment Index) was also analysed. Overall, fish metrics and the multimetric index signalled anthropogenic stress, particularly environmental chemical pollution. The fish assemblage associated with this type of pressure was characterized by lower species diversity, lower number of functional guilds, lower abundance of marine migrants and of piscivorous individuals, and higher abundance of estuarine resident species. A decreased ecological quality status, based on the EFAI, was also determined for sites associated with this pressure group. Ultimately, the definition of each pressure groups favoured a stressor-specific analysis, evidencing pressure patterns and accounting for multiple factors in a highly dynamic environment.
The assessment of water quality has changed markedly worldwide over the last years, especially in... more The assessment of water quality has changed markedly worldwide over the last years, especially in Europe due to the implementation of the Water Framework Directive. Fish was considered a key-element in this context and several fish-based multi-metric indices have been proposed. In this study, we propose a multi-metric index, the Estuarine Fish Assessment Index (EFAI), developed for Portuguese estuaries, designed for the overall assessment of transitional waters, which could also be applied at the water body level within an estuary. The EFAI integrates seven metrics: species richness, percentage of marine migrants, number of species and abundance of estuarine resident species, number of species and abundance of piscivorous species, status of diadromous species, status of introduced species and status of disturbance sensitive species. Fish sampling surveys were conducted in 2006, 2009 and 2010, using beam trawl, in 13 estuarine systems along the Portuguese coast. Most of the metrics presented a high variability among the transitional systems surveyed. According to the EFAI values, Portuguese estuaries presented a “Good” water quality status (except the Douro in a particular year). The assessments in different years were generally concordant, with a few exceptions. The relationship between the EFAI and the Anthropogenic Pressure Index (API) was not significant, but a negative and significant correlation was registered between the EFAI and the expert judgement pressure index, at both estuary and water body level. The ordination analysis performed to evaluate similarities among North-East Atlantic Geographical Intercalibration Group (NEAGIG) fish-based indices put in evidence four main groups: the French index, since it is substantially different from all the other indices (uses only four metrics based on densities); indices from Ireland, United Kingdom and Spain (Astúrias and Cantábria); the Dutch and German indices; and the indices of Belgium, Portugal and Spain (Basque country). The need for detailed studies, including comparative approaches, on several aspects of these assessment tools, especially in what regards their response to anthropogenic pressures was stressed.
Fish-based indices are becoming important bioassessment tools for estuaries since the European Wa... more Fish-based indices are becoming important bioassessment tools for estuaries since the European Water Framework Directive included fish as a biological quality element to be monitored for the assessment of ecological status of those systems. In particular, data on species composition and abundance of the ichthyofauna must be used to evaluate the ecological status of European estuaries, but other factors like measures of fish health are also considered important metrics. These indicators of fish health include infections by parasites. The common goby, Pomastoschistus microps, and the Lusitanian toadfish, Halobatrachus didactylus, are fairly sedentary fish, very abundant in Portuguese estuaries, and were used to investigate if parasitism in fishes in transitional waters is a good metric to reflect anthropogenic impacts in the environment. No significant relationships were observed between the parasite levels in these two species and the intensity of human pressures, either at a large or small spatial scale. Results obtained also are contrary to the generalized idea that a higher proportion of parasitized fish necessarily reflects a decrease in their condition as a result of habitat degradation. A high degree of temporal and ontogenetic variability in the parasite levels of both P. microps and H. didactylus was detected, which make it difficult to establish the scores for this hypothetical metric even if significant relationships between parasite levels and human pressures are identified in the future. Therefore, the present work does not uphold the hypothesis that parasitism in fish is a good metric to assess ecological water quality in transitional waters.
According to the Water Framework Directive (WFD) transitional waters should be differentiated acc... more According to the Water Framework Directive (WFD) transitional waters should be differentiated according to type and, in some cases, divided into different water bodies. This raises a dilemma in trying to define parts of a continuum. In the sequence of WFD several indices have been proposed including the Estuarine Fish Assessment Index, which can be applied taking an estuary as a whole (EFAI – without water bodies division) or divided in water bodies (EFAIWB). The purpose of this work is to analyze the robustness of the Estuarine Fish Assessment Index, based on three different ways of dividing Portuguese estuaries into water bodies according to different criteria (criterion 1 – distance to the estuary mouth, criterion 2 – salinity and criterion 3 – morphology, salinity and human dimension as pressure and state). In this study we evaluated at which degree these three criteria could influence the ecological quality ratio (EQR) results, when the index was applied to water body level (EFAIWB). Also, for each estuary, the EQRWB results for each criterion of EFAIWB were combined and weighted according to the water bodies areas (EFAI overall weighted – EFAIOW). Finally, it was compared if the results obtained for each criterion with the EFAIOW were similar to the results of the index application taking the estuary as a whole (EFAI – without water bodies division). No significant differences were found in both cases, which indicated that this index is a robust method regarding the division of the estuaries in different water bodies, which is an important element of a fish-based multimetric tool for assessing estuarine ecological quality. However, in some cases, different ecological quality statuses were achieved when applying the EFAIOW or the EFAI. This work addressed several aspects regarding the possible division of water bodies at the WFD context.
Beam trawling results in large amounts of discards. Discards mortality may be influenced by some ... more Beam trawling results in large amounts of discards. Discards mortality may be influenced by some of the procedures aboard fishing vessels. In the present study, the influence of temperature of the sorting containers, of sorting time and of haul duration on the mortality of brown-shrimp discards from the beam trawl fishery in the Tagus estuary was evaluated. Experiments were conducted in the summer and in the winter of 2000, simulating on-board procedures, in different conditions. The sorting containers were either wooden, plastic or metallic, dark or light-coloured, and two sorting times (5 and 10 min) and three haul durations (10, 20 and 30 min) were considered. The light-coloured wooden and plastic containers presented the lowest temperatures, whereas the highest one was measured on the dark metallic container. For temperatures between 10 and 20 °C, mortality was nil; for values higher than 20 °C, mortality was high, reaching 96% in the temperature interval 40–50 °C. Discards mortality was similar for both sorting times considered. The mortality of discards increased with longer haul duration; for 10 min, mean mortality was 7%, whereas for 30 min was 75%. The use of light-coloured wooden or plastic sorting containers in summer and the avoidance of fishing activities at the hottest times of day in this season are suggested as management measures to minimise discards mortality in beam trawl fisheries.
The brown-shrimp beam trawl fishery carried out within the Tagus estuary produces discards due to... more The brown-shrimp beam trawl fishery carried out within the Tagus estuary produces discards due to the little commercial interest of most of the species caught. Between 1994 and 1996, monthly samples were collected in the two major fishing areas within the Tagus estuary, using a beam trawl, in order to estimate the amount of fish and crustaceans caught per unit of effort. The fishing effort of the commercial fleet was determined based on surveys of professional fishermen. Mortality estimates of discards were also evaluated experimentally. The main fish and crustacean species discarded after capture were Crangon crangon (Linnaeus, 1758), Liza ramada (Risso, 1826), Carcinus maenas (Linnaues, 1758) and Pomatoschistus minutus (Pallas, 1770). The estimated total amount of fishery discards in the upper part of the Tagus estuary is approximately 1500 tonnes per year, which represents ca. 90% of the captures. The mortality rate of the fishes and crustaceans discarded varied according to species and season, with the highest rates during Summer months. Considering nitrogen and carbon content of the main discarded species, an input of particulate organic matter of more than 140 tonnes of carbon and 35 tonnes of nitrogen per year were estimated for these estuarine areas.
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