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Quantification of interactions between the Portuguese sardine purse-seine fishery and cetaceans
No full textInteractions 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
Seabird bycatch in Portuguese mainland coastal fisheries: An assessment through on-board observations and fishermen interviews
Get PDFCompetition with fisheries and incidental capture in fishing gear are the major current threats for seabirds at sea. Fishing is a traditional activity in Portugal and is mainly composed of a great number of small vessels. Given the lack of knowledge on effects of the Portuguese fishing fleet on seabird populations, bycatch was assessed in mainland coastal waters for 2010–2012. Interviews and on-board data were divided into 5 strata, according to fishing gear: Bottom trawling, Bottom longline, Purse seine, Beach seine, Polyvalent (≥12 m) and Polyvalent (<12 m). Polyvalent included Setnets, Traps and Demersal longlines. Overall, 68 birds were recorded to be bycaught. The average catch per unit effort (CPUE) was 0.05 birds per fishing event. Polyvalent (<12 m), Polyvalent (≥12 m) and Purse seiners had the biggest seabird bycatch rates, with 0.5 (CPUE=0.1), 0.11 (CPUE=0.05) and 0.2 (CPUE=0.11) birds per trip, respectively. Within Polyvalent gear, Setnets captured the largest diversity of seabird species (CPUE=0.06), while Demersal longline had the highest CPUE (0.86). Northern gannet was the most common bycaught species. Although more observation effort is required, our results suggest that substantial numbers of Balearic shearwater might be bycaught annually, mainly in Purse seine and Setnets
Postglacial climate changes and rise of three ecotypes of harbour porpoises,Phocoena phocoena, in western Palearctic waters
No full textDespite no obvious barriers to gene flow in the marine realm, environmental variation and ecological specializations can lead to genetic differentiation in highly mobile predators. Here, we investigated the genetic structure of the harbour porpoise over the entire species distribution range in western Palearctic waters. Combined analyses of 10 microsatellite loci and a 5085 base-pair portion of the mitochondrial genome revealed the existence of three ecotypes, equally divergent at the mitochondrial genome, distributed in the Black Sea (BS), the European continental shelf waters, and a previously overlooked ecotype in the upwelling zones of Iberia and Mauritania. Historical demographic inferences using approximate Bayesian computation (ABC) suggest that these ecotypes diverged during the last glacial maximum (c. 23–19 kilo-years ago, kyrbp). ABC supports the hypothesis that the BS and upwelling ecotypes share a more recent common ancestor (c. 14 kyrbp) than either does with the European continental shelf ecotype (c. 28 kyrbp), suggesting they probably descended from the extinct populations that once inhabited the Mediterranean during the glacial and post-glacial period. We showed that the two Atlantic ecotypes established a narrow admixture zone in the Bay of Biscay during the last millennium, with highly asymmetric gene flow. This study highlights the impacts that climate change may have on the distribution and speciation process in pelagic predators and shows that allopatric divergence can occur in these highly mobile species and be a source of genetic diversity
Biology & Ecology of anchovies and sardine.
No full textApart from being commercially and socially significant, anchovies and sardines populations occupy crucial positions in the oceans’ ecosystems. Low in the food chain, clupeoids tend towards abundance, as if their purpose in life was to be eaten and fuel the upper levels of marine trophic chains. The present book covers a broad spectrum of topics on the biology (sytematics, phylogeography, reproduction, feeding) and ecology (habitat characterization, recruitment variability) of anchovies and sardines. It also puts together important information on the state of their fisheries, exploitation and management
Do pingers cause stress in fish? An experimental tank study with European sardine, Sardina pilchardus (Walbaum, 1792) (Actinopterygii, Clupeidae), exposed to a 70 kHz dolphin pinger
No full textAcoustic deterrent devices (pingers) that are designed to alert marine mammals to the presence of fishing gear have been successfully employed to reduce cetacean–fishery interactions. However, pinger sounds may affect fisheries target species: noise can induce short-term stress responses in fish that are reflected in increased blood cortisol concentrations and behavioural alterations, which may ultimately result in reduced catch rates. In order to test this hypothesis, the present study analyses the hormonal and behavioural stress response of European sardine (Sardina pilchardus) to a commercially available pinger—the 70 kHz dolphin pinger. The responses of wild captive fish to the pinger sounds were tested in tank experiments, measuring the stress level of fish by analysing blood plasma cortisol concentration and swimming behaviour. Mixed effect models were used for statistical analysis. During the experiments, pinger sounds caused subtle, but significant elevations in sardine plasma cortisol concentration and fish school compaction. However, when compared to the rates of increase reported for acute stress responses in similar studies, the observed increment was very small. This suggests that the sounds of the trialled pinger are not likely to significantly alter sardine behaviour and should consequently not have any negative impact on sardine catch rates
Fishers’ Behaviour in Response to the Implementation of a Marine Protected Area
Get PDFMarine Protected Areas (MPAs) have been widely proposed as a fisheries management tool in addition to their conservation purposes. Despite this, few studies have satisfactorily assessed the dynamics of fishers’ adaptations to the loss of fishing grounds. Here we used data from before, during and after the implementation of the management plan of a temperate Atlantic multiple-use MPA to examine the factors affecting the spatial and temporal distribution of different gears used by the artisanal fishing fleet. The position of vessels and gear types were obtained by visual surveys and related to spatial features of the marine park. A hotspot analysis was conducted to identify heavily utilized patches for each fishing gear and time period. The contribution of individual vessels to each significant cluster was assessed to better understand fishers’ choices. Different fisheries responded differently to the implementation of protection measures, with preferred habitats of target species driving much of the fishers’ choices. Within each fishery, individual fishers showed distinct strategies with some operating in a broader area whereas others kept preferred territories. Our findings are based on reliable methods that\ud
can easily be applied in coastal multipurpose MPAs to monitor and assess fisheries and fishers responses to different management rules and protection levels. This paper is the first in-depth empirical study where fishers’ choices from artisanal\ud
fisheries were analysed before, during and after the implementation of a MPA, thereby allowing a clearer understanding of the dynamics of local fisheries and providing significant lessons for marine conservation and management of coastal systems
Monitorização da população reprodutora de Roque-de-castro Oceanodroma castro do Farilhão Grande, Berlengas 2011-2012
Get PDFBreeding Madeiran Storm-petrels Oceanodroma castro on Farilhão Grande islet was first described in the early 80s. Despite being an important breeding colony at nationally and global level for the species distribution, few studies regarding monitoring and/or research have been developed. In order to update the knowledge about this population, SPEA, under the FAME project, made 7 visits to the islet between 2011 and 2012. We used mist-nets, nocturnal vocalizations and ground search to assess the population size. The population was estimated to be 473 individuals, resulting in 102-201 breeding pairs, which may indicate a high population decreasing. Comparison with previous studies emphasizes the need to conduct a directed census in order to obtain more robust estimate of this population. For the first time it was used a tracking device (GLS) in Madeiran Storm-petrels to assess movements and distribution of the species during the breeding season. The only GLS recovered showed that the individual made a 5 days trip over open sea to the west coast of Morocco. The walls built in 2002, during an action performed previously by SPEA, which host some Madeiran Storm-petrel nests, were rebuilt. We also implemented 36 new artificial nests that will enable future work with this population. A census of Yellow-legged Gull Larus michahellis that breeds on the islet took place, and 170-180 pairs were estimated. During the several visits to the island, it was detected gulls like signs of predation on Madeiran Storm-petrel. This effect however will be better reported later
Patterns and trends in the diet of long-finned pilot whales (Globicephala melas) in the northeast Atlantic
No full textThere is little previous information on feeding habits of long-finned pilot whales (Globicephala melas) in the northeast Atlantic. The present study analyzed stomach contents of pilot whales stranded in Portugal (n = 6), Galicia (northwest Spain) (n = 32), and Scotland (United Kingdom) (n = 10), from 1990 to 2011. These animals ranged from 213 to 555 cm in length (24 females, 19 males and 5 of unknown sex). The main prey identified were cephalopods of the families Octopodidae and Ommastrephidae, the former being numerically more important in Iberia (Portugal and Galicia) and the latter more important in Scotland, with Iberian whales also showing a more diverse diet. Multivariate analysis revealed evidence of geographical and seasonal variation in diet. Generalized Additive Modeling results indicated that more octopus (Eledone cirrhosa) were eaten in Iberia than in Scotland, more in the first half of the year, and more in larger whales. Numbers of ommastrephid squids in the stomach decreased over the study period and varied with season and whale length. This study confirms cephalopods as the main prey of pilot whales, as previously reported, although our results also suggest that, in the northeast Atlantic, ommastrephid squid are largely replaced as the main prey by octopods at lower latitudes
The system Tetrabothrius bassani (Tetrabothriidae)/Morus bassanus (Sulidae) as a bioindicator of marine heavy metal pollution
No full textHelminths are known to accumulate higher amounts of certain elements than their hosts. The present study assesses the accumulation of heavy metals in Tetrabothrius bassani and in its host, the Atlantic gannet (Morus bassanus) found dead due to bycatch along the seashore in the centre of Portugal. Samples of kidney, liver and pectoral muscle of 23 infected gannets, as well as specimens of T. bassani were analysed for As, Cd, Cr, Cu, Hg, Mn, Pb, Se and Zn by ICP-MS. The evidenced lower concentrations of Cr and Pb in tissues of gannets in comparison to an earlier study performed in the same area may reveal a change in the diet of M. bassanus between both study periods. The highest bioaccumulation factor was obtained for Cd with a 12.7-times higher concentration in the cestode than in gannet muscle. Lead concentration in T. bassani was 6.9-times higher than in kidney tissue, 8.5-times higher than in muscle and 9.5-times higher than in liver of M. bassanus. The cestode/seabird system T. bassani/M. bassanus can be considered a promising bioindicator system to monitor environmental Cd and Pb pollution in marine ecosystems
Monitorização de aves arrojadas\ud na costa Portuguesa 2011/12
No full textNo âmbito do projeto FAME – Future of the Atlantic Marine Environment, foi definido um esquema de monitorização de aves arrojadas, nos anos de 2011 e 2012, baseado em transetos nas zonas de maior extensão de areia da costa continental Portuguesa. Estas foram monitorizadas de Peniche para norte pela equipa da Universidade do Minho/SPVS, e de Peniche para sul por equipas da SPEA. Foi realizada uma parceria com a Polícia Marítima no sentido da utilização dos veículos “Rhino”.\ud
Entre março de 2011 e dezembro de 2012 foram prospectados 617 km de costa, e foram encontradas 163 aves marinhas, mas também cetáceos, tartarugas-marinhas e aves terrestres. Na zona norte foram efetuadas necrópsias no centro de recuperação QRAM-Quiaios, para deteção das causas de morte.\ud
Nos 3 períodos, num total de 22 espécies de aves marinhas detetadas, o arrojamento mais comum foi a gaivota não-identificada (35 na parte norte e 17 na parte sul), seguida da gaivota-de-patas-amarelas Larus michahellis (14 ind. na parte norte e 16 na parte sul). As gaivotas foram o grupo mais representado, com a presença de 103 indivíduos de 6 espécies. O período em que foram encontrados mais animais arrojados foi o outono (12,4 ind./10 km na parte norte, e 2,54 ind./10 km na parte sul). Este facto pode estar relacionado com a passagem pós-reprodutora de espécies invernantes (ex: gaivota-d'asa-escura Larus fuscus e alcatraz Morus bassanus) ou condições climatéricas adversas em alto mar.\ud
Quanto às causas de morte, de 750 indivíduos detetados em transetos e alertas, foram realizadas 559 necrópsias a 18 espécies diferentes desde setembro 2010 a outubro 2012, correspondendo a cerca de 70% das aves que foram detectadas arrojadas mortas em 150km da costa ocidental portuguesa. Este estudo permitiu identificar dois factores que ameaçam a conservação de aves marinhas: poluição e captura acidental em artes de pesca.\ud
De destacar um arrojamento massivos de 533 tordas-mergulheiras Alca torda, resultante de mortalidade por captura acidental em artes de redes.\ud
Na zona sul estudou-se ainda a composição dos resíduos encontrados nos transetos, em que a matéria vegetal registou os valores mais elevados (47%), sendo o restante composto por resíduos provenientes da pesca (26,5%) e recicláveis (26,5%)