Portuguese Continental Coast Research Articles

Adapting the sampling design of research surveys to improve the biomass estimation of secondary species—the case study of Raja clavata

Abstract Research surveys are important to evaluate fishery resources’ spatial distribution and abundance. Although the underlying sampling is usually conceived with a focus on specific species, efficient designs can also collect data on secondary species. We present a framework to explore and evaluate the adequacy of alternative sampling designs for fishery research surveys aiming to maximize accuracy estimates of the secondary species abundance while maintaining the quality of the abundance estimates of primary species. A geostatistical model-based approach was developed considering the semi-continuous nature of the data and the excess of zero values commonly observed for secondary species. New sampling designs were defined according to optimization weights and evaluated based on the resulting prediction exactness. The framework was applied to the bottom trawl survey conducted along the Portuguese continental coast with European hake, Merluccius merluccius, as the primary species and thornback ray, Raja clavata, as the secondary species. The sampling design URSI provided the best balance between the accuracy for both primary and secondary species. The methodology can be replicated for other bottom trawl research surveys and an extended set of species. We recommend that a decision on which sampling design to adopt in future surveys should consider a cost-efficiency analysis.

Time and spatial trends in landing per unit of effort as support to fisheries management in a multi-gear coastal fishery

Landings by the multi-gear coastal fleet operating off the Portuguese continental coast include about 300 species, from which only a few are the object of management plans. In this study, daily landings (kg trip-1) are used, along with an effort indicator, vessel length overall (LoA), to obtain landings per unit of effort (LPUE) as a proxy for the species relative abundance, for a total of 48 species. LPUE indices were used as a response variable in linear models where year (2012–2016), season, region (north and south) and NAO index were explanatory variables. Seasonal and regional effects were found to significantly affect species abundance for a total of 41 and 40 species respectively, while year trends were found to be significant for 19 species, and the NAO index for 3 species. LPUE density maps are presented for several selected species and a subsample of trips, where VMS records were available. It is proposed that geographic and seasonal changes in LPUE can be used to understand trends in abundance and obtain information that can be used in support regional management plans.

Deep-sea trawling off the Portuguese continental coast––Spatial patterns, target species and impact of a prospective EU-level ban

Following the implementation of the European Council EC Regulation 2016/2336, which restricts bottom trawling below 800 m for vessels capturing deep-sea fish species, the quantification and characterization of the fishing activities at those depths became essential to evaluate potential negative economic impacts. In this study, the activity of the Portuguese coastal trawlers operating at fishing grounds deeper than 800 m is characterized for the period 2005–2016, based on the analysis of VMS data and landing declarations in national ports. A total of 13 of 125 active trawlers in the coastal fleet were found to be partially engaged in deep-sea trawling, but only two units were entirely dedicated to this activity over the period in analysis. The scarlet shrimp Aristaeopsis edwardsiana was landed from 2006 onwards as the only target species at these depths. For each of these 13 vessels, the correspondence between VMS records of trajectories assigned to fishing trips, and landing registers, provided information on the spatio-temporal patterns of activity along the time period under analysis. Among fish by-catch, only in 2006 and 2007 were deep-sea species protected under Reg. 2016/2336 recorded, after which only small, occasional landings occurred. Results show that the implementation of the trawl ban does not affect the economic activity of the Portuguese coastal trawl fleet. Even if a full ban was to be implemented it would only impact the activity of two single vessels, which would have to completely redirect their fishing operations.

Assessing spatio-temporal changes in marine communities along the Portuguese continental shelf and upper slope based on 25 years of bottom trawl surveys

The Portuguese continental coast is influenced by several oceanographic processes and is located near the confluence of three biogeographic realms (from the North Atlantic, South Atlantic and Mediterranean). Given these features, the topography of the Portuguese coast, possible variations in fishing effort and reported increasing sea surface temperature in the last decades, we hypothesized that changes in marine communities in space and time occurred since 1990. In this study, research survey data collected yearly along the Portuguese continental slope (20–500 m deep) from 1990 to 2016 were analysed with the objective of identifying spatio-temporal changes. Latitude and depth were found to play a major role in communities’ spatial differentiation, probably associated to temperature, and three ecological areas were defined (north, southwest and south). In the studied period, Macroramphosus spp. abundance showed a marked decrease in all areas whereas Sparids increased in abundance in the south. Despite these major changes and fluctuations in species abundance over time no major trends in communities were observed. Fishing activity, environmental conditions (including climate change) and biotic factors are all drivers possibly responsible for those changes.

Toxin profile of Ostreopsis cf. ovata from Portuguese continental coast and Selvagens Islands (Madeira, Portugal)

The toxigenic dinoflagellate Ostreopsis cf. ovata is known to produce a range of palytoxin (PLTX) - related compounds named ovatoxins (OVTX). O. cf. ovata presents a wide variability in toxin production and its toxic profile is strain-specific. Several OVTXs, denominated from -a to -h and -l have been reported from different strains of this benthic microalgae up to now, mainly in Mediterranean isolates. However, less is known about the toxin profile of the strains present in the Atlantic coasts of Europe. In this work, strains of O. cf. ovata isolated from the South coast of Portugal mainland (Algarve) and Selvagens Island (Madeira, Portugal) were cultured and tested for toxicity by hemolytic assay. Toxin profiles were qualitatively elucidated by Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS). The strain from Algarve presented lower toxic potency than the strain from Selvagens island (12.3 against 54.8 pg of PLTX equivalents per cell) showing in both cases the characteristic toxin profile of Mediterranean strains. The major component, OVTX-a, was concomitant with OVTX from -b to -g and isobaric PLTX. Regarding the morphological characteristics of these strains, as well as their toxin fingerprint, it is likely they are closely related to strains from Mediterranean coasts. The present study reports for the first time the occurrence of several OVTX congeners and iso-PLTX in O. cf. ovata from Portuguese waters. This study provides valuable information to characterize the risk of OVTXs-related outbreaks in Portugal.

Spatial distribution and abundance of the by‐catch coastal elasmobranch Raja undulata: Managing a fishery after moratorium

AbstractThe undulate ray Raja undulata Lacepède is a coastal species common along the north‐eastern Atlantic Ocean and Mediterranean Sea and is highly accessible to coastal fisheries. Between 2009 and 2015, the species was under a European Union (EU) fisheries moratorium that hampered the collection of data to assess its stock status in Portuguese waters. After that period, a small experimental EU fishing quota was set for Portugal enabling collection of fishery data under a fishermen self‐sampling scenario. Based on the data collected, R. undulata abundance was estimated along the Portuguese continental coast through the application of a N‐mixture model and incorporating environmental factors. The results support the species coastal and patchy nature across the study area with higher abundances estimated in areas associated with shallow sandy bottoms as the Southwest region. The present work constitutes an important step for the management of this fishery resource, in particular concerns about its abundance trends over time and its spatial distribution and habitat requirements.

Morphological Variability of Phorcus lineatus (da Costa, 1778) Shells along the Coast of Portugal and the Significance of the Environment on Shell Morphology

Phorcus lineatus (da Costa, 1778) is a marine intertidal gastropod occurring in the Eastern Atlantic, from Northern Ireland and Wales to Mauritania. Along the Portuguese continental coast, it displays marked shell variability. Northern shells have a worn spire, but southern specimens display good preservation. At most sites, the majority of shells show no umbilicus, but at sites scattered along the coast, most shells display a distinct or conspicuous umbilicus. In order to understand these discrepancies, I carried out analyses of the mean grain size of the beach sand where live animals were collected and estimations of the annual mean wave height near the sampling sites by using Portuguese Institute for Sea and Atmosphere (IPMA) forecasts. Sampling, experiments and data loading were carried out in the period 2012–2015. Whereas no direct correlation was found between umbilicus prominence, shell size and studied environmental variables, abrasion and wear of the spire were found to be primarily dependent upon sea wave height and on beach sand grain size. It was concluded that current malacological literature, particularly field guides, sub-represent the morphological diversity of P. lineatus shells omitting eroded shells, and that worn shells occur along the distribution range of this species. Abrasion and wear of P. lineatus shells appear to increase with increasing sea wave height, and also with increasing beach sand grain size, reflecting the intensity of the hydrodynamics at a local scale.

Striped dolphins as trace element biomonitoring tools in oceanic waters: Accounting for health-related variables

In Europe, monitoring contaminant concentrations and their effects in the marine environment is required under the Marine Strategy Framework Directive (MSFD, 2008/56/EC). The striped dolphin (Stenella coeruleoalba) is the most abundant small cetacean species in Portuguese oceanic waters, representing a potential biomonitoring tool of contaminant levels in offshore waters. Concentrations of nine trace elements were evaluated by ICP-MS in kidney, liver and muscle samples of 31 striped dolphins stranded in the Portuguese continental coast. The mean renal Cd concentration was high (19.3 μg.g−1 wet weight, range 0.1–69.3 μg.g−1 wet weight) comparing to striped dolphins from other locations. Therefore, the present study reports a possibly concerning level of Cd in the oceanic food chain in Portuguese offshore areas. This study also aimed at evaluating potential relationships between trace element concentrations and striped dolphins' biological and health-related variables. Individual length was related with some of the trace element concentrations detected in striped dolphins. Indeed, Cd, Hg and Se bioaccumulated in larger animals, whereas the reverse was observed for Mn and Zn. Striped dolphins with high parasite burdens showed higher levels of Hg, while animals showing gross pathologies presented higher concentrations of Cd and Se. This study reported relationships between trace element concentrations and health-related variables for the first time in striped dolphins and it also provided information on the relative contamination status of Portuguese oceanic waters in comparison to other regions in the world.

Tetrodotoxins Occurrence in Non-Traditional Vectors of the North Atlantic Waters (Portuguese Maritime Territory, and Morocco Coast).

Tetrodotoxin (TTX) is a potent alkaloid typically from tropical ecosystems, but in the last decade its presence has been more pronounced in the temperate waters of the Atlantic. In its last scientific opinion, the European Food Safety Authority (EFSA) stressed the need for data regarding TTX prevalence in European waters. To address EFSA’s concerns, benthic organisms such as mollusks, crustaceans, echinoderms and fish with different feeding habits were collected along the Portuguese continental coast, islands (São Miguel, Azores, and Madeira) and the northwestern Moroccan coast. A total of 165 samples were analyzed by ultra high performance liquid chromatography high resolution mass spectrometry (UHPLC-HRMS) and ultra high performance chromatography mass spectrometry (UHPLC-MS/MS). Geographical tendencies were detected as follows, by descending order: S. Miguel Island (Azores), Moroccan coast, Madeira Island and Portuguese continental coast. The toxin amounts detected were significant, above the Dutch limit value established in 2017, showing the importance and the need for continuity of these studies to gain more knowledge about the prevalence of these toxins, unraveling new vectors, in order to better assess human health risk. This work represents a general overview of new TTX bearers (7) most of them in gastropods (Patella depressa, Nucella lapillus, Onchidella celtica and Aplysia depilans), followed by echinoderms (Echinus esculentus and Ophidiaster ophidianus) and puffer fish Sphoeroides marmoratus.

Economic Feasibility of Wave Energy Farms in Portugal

This paper develops a methodology to determine the economic feasibility of implementing offshore wave energy farms on the Portuguese continental coast. This methodology follows several phases: the geographic phase, the energy phase, the economic phase, and the restrictions phase. First, in the geographic phase, the height and the period of the waves, the bathymetry, the distance from the farm to the shore, from farm to shipyard, and from farm to port, are calculated. In the energy phase the energy produced by each wave energy converter is determined, and in the economic phase, the parameters calculated in the previous phases are used as input to find the economic parameters. Finally, in the restrictions phase, a limitation by the bathymetry will be added to the economic maps, whose value will be different depending on the floating offshore wave energy converter (WEC). In this study, three wave energy converters have been considered, Pelamis, AquaBuOY, and Wave Dragon, and several scenarios for electric tariffs have been taken into account. The results obtained indicate what the best WEC is for this study in terms of its levelized cost of energy (LCOE), internal rate of return (IRR), and net present value (NPV), and where the best area is to install wave energy farms.

Insight on reproductive strategy in Portuguese waters of a commercial protogynous species, the black seabream Spondyliosoma cantharus (Sparidae)

Information on fish reproductive strategy is essential to understand population dynamics. Samples of black seabream, Spondyliosoma cantharus, were collected from the western Portuguese continental coast to investigate the reproductive cycle, the timing of spawning, length at maturity and sex change, fecundity type and fecundity. This species is a protogynous hermaphrodite, showing a sharped biased sex ratio towards females for lengths smaller than 25 cm, and significantly biased towards males above this value, with no females occurring above 35 cm. Development of secondary growth follicles was asynchronous, and it was estimated that each female spawns 27 batches during the spawning season, which takes place from February to May. Half of the females’ population was mature at 18.41 cm and have changed sex at 25.62 cm. Sex change takes only a brief period of time, as transitional individuals were scarce and most showed oocytes regressing into cystic structures. The species presents a clear indeterminate fecundity type with massive atresia happening at the end of the spawning season. Mean values of 203 oocytes and 5431 oocytes by gram of eviscerated female were estimated for relative batch fecundity and relative annual fecundity, respectively.

Wave energy distribution along the Portuguese continental coast based on a thirty three years hindcast

Abstract An assessment of wave power resource for Portugal continental coast is presented, using thirty three years (1979–2012) of wave hindcast. The hindcast system is based in two spectral wave models, WWIII (WAVEWATCHIII) for the wave generation and SWAN (Simulating WAves Nearshore) for wave transformation in coastal areas. To improve the SWAN model performance, six high resolution areas (Agucadoura, Figueira da Foz, Sao Pedro de Moel, Peniche, Cascais and Sines) were nested into one large area (Iberian coast). The assessment of wave power potential was done by studying the spatial and temporal behaviour using average for different time scales (monthly, seasonal, inter-annual and total time). Moreover, the wave climate variability was determined through the calculation of the coefficient of variation, seasonal variability index and monthly variability index. The results have shown that in Portugal the wave energy is higher in the northwest, that the wave climate variability has more impact in the south and that the month with the highest energy is January. A bivariate distribution of significant wave height and energy period was also determined, showing that the sea states where more wave power can be extracted are different than the ones that occur more frequently.

Variability of wave parameters and Hmax/Hs relationship under storm conditions offshore the Portuguese continental coast

The relevance of long-term wave storm characterization based on in-situ measurements extends from marine ecosystems management to the design of ocean engineering structures. We analyze wave storms recorded over almost three decades (1988–2015) in three points offshore the Portuguese continental coast located between 83 and 97 m water depth. We provide Probability Distribution Functions for mean wave direction (θm), directional wave spreading (σθ), significant wave height (Hs), maximum wave height (Hmax), mean wave period (Tz) and, Hmax/Hs relationship based on four storm datasets. In the highly energetic Portuguese west coast (Leixões and Sines), Hmax and Hmax/Hs ranged between 5.5 and 17.3 m and 1.16 to 2.47, respectively. We conclude that a GEV distribution can represent Hmax and Hmax/Hs variability at the three analyzed locations. Despite the differences in the dataset lengths and the differences in the range and variability of θm, σθ, Tz, Hs, and Hmax, we found that the range and variability of Hmax/Hs are very similar for the four storm datasets. For the analyzed period, σθ ranged between 8 and 52° and 10 to 59° in the west and south coast (Faro Atlantic and Faro Levante storms), respectively, and its variability can be described by a log-logistic distribution.

Diet and feeding strategy of the forkbeard Phycis phycis (Pisces: Phycidae) from the Portuguese continental coast

The diet and feeding behaviour of the forkbeard Phycis phycis was studied based on 246 stomachs collected between May 2011 and April 2012 from a commercial fleet operating off the central west coast of Portugal. A total of 44 prey items were identified in the stomachs which were merged into major groups to avoid problems with low expected frequencies. The following taxonomic categories were considered: non-decapod Crustacea, Caridea, Anomura, Munida spp., Processa spp., Brachyura, Pisces, Trisopterus luscus. In order to investigate possible diet differences between fish size classes, a cluster analysis was performed using the mean abundance of each prey group by forkbeard 5 cm length class, and three length groups (LG) were obtained: <22.5, 27.5–37.5 and >42.5 cm. Seasonally, Caridea was the main prey group during winter and autumn while Pisces was predominant during the rest of the year. Caridea was the most important prey group for LG1 and LG2 while in LG3 Pisces was the principal one. The forkbeard feeding behaviour may be characterized as presenting a shift pattern from a more generalist diet (small Crustacea, mainly Caridea) in the young adults to a more specialist strategy (teleosts) in the adults.

AUTOMATED SYSTEM FOR NEAR-REAL TIME PREDICTION OF OIL SPILLS FROM EU SATELLITE-BASED DETECTION SERVICE

ABSTRACT 2017-244: The state-of-the-art in both operational oceanography, remote sensing, and computational capacity, enables now the possibility of developing near-real time, holistic automated services capable of dramatically improving maritime situational awareness to responding to oil spill emergencies. Based on the European satellite-based oil spill and vessel detection service – CleanSeaNet (EMSA – European Maritime Safety Agency), which distributes oil pollution detection standardized notification packages in less than 30 minutes, a new automated early warning system (EWS) for near-real time modelling and prediction of the detected oil spills was developed. This EWS provides 48-hour oil spill forecasts + 24-hour backward simulations, delivering results 5–10 minutes after the reception of the oil spill detection notifications. These forecasts are then distributed in multiple formats and platforms (e.g. Google Earth, e-mail). The oil spill fate and behaviour model used in this EWS is part of MOHID modelling system, and is coupled offline with metocean forecast solutions, taking advantage of autonomous models previously run in multiple institutions. The system is currently able to integrate various metocean forecasting systems, being agnostic about the data sources and applied locations, as long as their outputs comply with commonly adopted formats, including CF compliant files or CMEMS (Copernicus Marine Environment Monitoring Service). The EWS is currently operational in western Iberia, supporting Portuguese Maritime Authority, and is being expanded to neighbourhood regions (from Spain and Morocco) with high resolution metocean models (MARPOCS project funded by European Union Humanitarian Aid & Civil Protection). Taking advantage of the coupling of MOHID oil spill model and CleanSeaNet, an oil spill hazard assessment is made in the Portuguese continental coast, based on the cumulative analysis of drift model simulations from previously detected spills using metocean model data, for a period between 2011–2016. Although this EWS doesn’t replace on-demand operational oil spill forecasting systems, it supports maritime authorities with a fast first-guess forecast solution, allowing:Anticipation of tactical response (including visual inspection of the spill) and mitigation of the pollution episode;A more effective identification of the pollution source, and in case of suspected illegal spill, earlier actions towards effective prosecution of the polluter;In the other hand, the hazard assessment generated is a valuable instrument for the development of efficient planning and prevention strategies. The EWS can be connected to any satellite-based detection service (inside or outside Europe) as long as the detected oil slicks are automatically distributed in a structured and standardized data format similar to CleanSeaNet.

Age, growth and reproduction of the protandrous hermaphrodite fish, Sarpa salpa, from the Portuguese continental coast

Salema, Sarpa salpa is a commercial exploited species in the Atlantic Ocean with little available information for the essential population parameters, such as age, growth and reproduction. The present study aims to describe these parameters for S. salpa obtained off the coast of Portugal. Ages were estimated from the whole otolith readings; the minimum and the maximum ages observed were 0 and 14 years, respectively, corresponding to 5.2 and 41.4 cm of total length (TL). Whole otolith readings and back-calculation approaches were used to estimate the parameters of the von Bertalanffy growth function and the Akaike's information criterion value suggested that the second approach was the best one to describe the growth of salema: L∞ = 45.07 cm, k = 0.14 year−1 and t0 = −1.43 year. The species is a protandric hermaphrodite and the sex change process occurred between 28.6 and 40.9 cm TL. A short spawning season was identified, extending from September to November. The estimated length at first maturity for males was 24.5 cm TL, corresponding to an age of 2 years at first maturity. This species exhibited a determinate fecundity type and the relative annual fecundity varied between 462 and 2662 oocytes per gram of gutted weight.

Patterns of benthic assemblages invaded and non-invaded by Grateloupia turuturu across rocky intertidal habitats

Intertidal benthic assemblages invaded and non-invaded by the introduced Asian red alga Grateloupia turuturu were compared at a rocky shore along the NW coast of Portugal. The structure of whole assemblages, the total richness of taxa and the abundance of individual taxa were examined as response variables in two different habitats (rock pools and emergent rock), two shore levels (low and mid intertidal) and two dates of sampling (June 2013 and June 2014).Invaded and non-invaded assemblages differed consistently across habitats and shore levels. Such differences were driven by 13 (with the green alga genus Ulva, the red alga Chondrus crispus and the mussel Mytilus galloprovincialis driving the total dissimilarity) out of the total 37 taxa identified. Individual taxa revealed idiosyncratic patterns, in several cases (C. crispus, M. galloprovincialis, articulated coralline algae of the genus Corallina and the crustose sporophyte of the red alga Mastocarpus stellatus) there were differences in the abundance of a taxon between invaded and non-invaded assemblages varying with levels of some other experimental factors. The total number of taxa was higher in invaded compared to non-invaded assemblages for each combination of habitat and shore level.Patterns of invasion by G. turuturu along the Portuguese continental coast were recently described in terms of its temporal and spatial distribution, but never examined in terms of differences between invaded and non-invaded assemblages. Such information is very limited for other geographic areas where this species is recorded out of its native range of distribution. Therefore, the present study provides a new contribution to the understanding of modifications of native assemblages associated with the invasion of G. turuturu, opening avenues of research aimed at specifically examining the factors and processes likely responsible for the invasion dynamics and success of this species.

Ingestion of marine litter by loggerhead sea turtles, Caretta caretta, in Portuguese continental waters

The accumulation of litter in marine and coastal environments is a major threat to marine life. Data on marine litter in the gastrointestinal tract of stranded loggerhead turtles, Caretta caretta, found along the Portuguese continental coast was presented. Out of the 95 analysed loggerheads, litter was present in 56 individuals (59.0%) and most had less than 10 litter items (76.8%) and less than 5g (dm) (96.8%). Plastic was the main litter category (frequency of occurrence=56.8%), while sheet (45.3%) was the most relevant plastic sub-category. There was no influence of loggerhead stranding season, cause of stranding or size on the amount of litter ingested (mean number and dry mass of litter items per turtle). The high ingested litter occurrence frequency in this study supports the use of the loggerhead turtle as a suitable tool to monitor marine litter trends, as required by the European Marine Strategy Framework Directive.

Quantification of interactions between the Portuguese sardine purse-seine fishery and cetaceans

AbstractInteractions between cetaceans and the purse-seine fishery operating along the whole Portuguese continental coast were studied based on on-board observations from 2010 to 2011. Cetacean presence and mortality were estimated and characteristics under which interactions were most likely to occur were identified. Observations were made on 163 fishing trips (0.7% of the average annual number of fishing trips) and 302 fishing operations/hauls. Cetaceans were present during 16.9% of fishing events; common dolphins (Delphinus delphis) accounted for 96% of occurrences, mostly overnight in summer and early autumn. Regression models showed that cetacean presence during a fishing set was significantly (p < 0.05) associated with sardine catches, effort, and latitude/longitude. Encirclement and mortality occurred in 2.3 and 1.0% of fishing events, respectively. Encircled species were the common dolphin, bottlenose dolphin (Tursiops truncatus), and harbour porpoise (Phocoena phocoena), but only common dolphin showed mortality (three individuals); raised to fleet level, estimated total mortality rates of common dolphins were 69 (95% CI 37–110) in the north and 91 (95% CI 55–165) in the south for 2010 and 78 (95% CI 47–140) in the south only for 2011. The estimated annual mortality rate due to purse seining is 113 (95% CI 3–264) common dolphins, which is ∼0.63% of the current most optimistic estimate of population size for the Portuguese fishing area (SCANS II). The wide confidence limits, as well as variation between years, reflect low observer coverage, emphasizing the need for increased monitoring to cover gaps in the spatial and seasonal distribution of observer effort and provide reliable estimates of bycatch.

Wave modelling at the entrance of ports

The objective of the present work was to develop and validate a flexible wave prediction system able to provide information about the wave conditions at the entrance of ports. Although the method is general, the present application addresses the major Portuguese ports, namely Leixões and Sines that are located in the northern and in the central part, respectively, of the Portuguese continental coast. A multilevel system for modelling the wave transformation (SWAN based) is implemented in the entire west Iberian nearshore and validated with buoy data. The ocean forcing is provided by WAM model simulations in an implementation over the entire North Atlantic basin. Both hindcast, nowcast and forecast schemes are evaluated and discussed. Focusing then on the two target areas, an analysis of some coastal processes such as diffraction and triad wave–wave interactions, as they are reflected in the simulations based on spectral models, is also performed. Finally, some average energetic and storm scenarios were also considered for the two harbours.