An ecological and fishing approach to support management decisions

Leitão, F., Monteiro, J. N., Cabral, P., Teodósio, M. A., & Roa-Ureta, R. H. (2023). Revealing the role of crab as bait in octopus fishery: An ecological and fishing approach to support management decisions. Marine Policy, 158, 1-11. [105878]. https://doi.org/10.1016/j.marpol.2023.105878 --- This study received Portuguese National Funding from MAR2020 project CRUSTAPANHA (MAR-01.04.02-FEAMP-0005 CRUSTAPANHA). FL has received Portuguese national funds from FCT within the contract program DL57/2016/CP1361/CT0008 and FCT 2022.04803. CEECIND. JNM received an FCT PhD fellowship SFRH/BD/06336/2021. This study received Portuguese national funds from FCT - Foundation for Science and Technology through projects UIDB/04326/2020, UIDP/04326/2020 and LA/P/0101/2020. Authors would like to acknowledge all fishers’ associations that participated in CRUSTAPANHA project and helped the completion of the study: AAPF- Associação de Armadores e Pescadores da Fuseta (Fuseta); Associação Armalgarve Polvo Organização De Produtores (Quarteira); OLHAOPESCA Organização de Produtores de Pesca do Algarve, C.R.L. (Olhão). We acknowledge DGRM for fisheries data provided and for granting licenses for researchers onboard fishing vessel; To the coast guards forces of the following ports: Capitania do Porto de Albufeira; Capitania do Porto de Faro; Capitania do Porto de Olhão; Capitania do Porto de Lagos; Capitania do Porto de Tavira; We would like to acknowledge specific captains due to their role in the study, namely: Ricardo Santana; Francisco Molina; Arlindo da Silva Correia; Paulo Guerreiro. We would like to acknowledge all the members of ECOREACH group that help in the measurement of the octopus specimens, namely Andreia Ovelheiro, Daniela Nobre, Juan Bueno-Pardo and Miguel PintoIn southern Portugal, artisanal octopus fisheries play an important socioeconomic role. Live crab bait in traps was used up to 2010 and banned in 2012. Such regulation, based on co-management advice, was not established under a scientific fundament. As a result, a long-standing controversy ensued with some fishing associations claiming that live crab bait increased fishing effort and exploitation rates and therefore risked the octopus stock status, while other fishers denied all these alleged impacts. The issue has not been resolved so far due to lack of scientific studies. In this study, we resolve the controversy conducting experimental fishing to determine by-catch and octopus catch rates using live crab bait versus other types of baits based on fish and assess the stock status of octopus over-time with constant parameters (hypothesis of no effect of the use of live crab bait) versus time-varying parameters (hypothesis of raised exploitation rates and riskier stock status). Bycatch was very low regardless of bait type. Our experimental fishing trials showed that fish-based baits increase bycatch and octopus catch rates. Stock assessment models showed that exploitation rates and stock status do not worsen in years of use of crab bait. We conclude that the use of crab bait in octopus fishery does not lead to increased exploitation rate or risks for stock sustainability status. Other considerations involving fishing costs and fishing operations further highlight the advantages of lifting the ban on the use of live crab bait in the Algarve octopus fishery.publishersversionpublishe

Spatial and temporal variation of commercially important bivalve species in the Algarve coast, Portugal

Dissertação de mestrado, Biologia Marinha, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015Artisanal fisheries in the Algarve are a very important industry for local communities and for the local economy. The target species in this fishery are the white clam (Spisula solida), the striped venus (Chamelea gallina), the donax clam (Donax trunulus) and razor clam (Ensis siliqua). The Portuguese Institute of the Sea and Atmosphere (IPMA) is responsible for the management of these fisheries and the existing resources, to ensure its sustainable development. It is known that in addition to the fishing pressure exerted on these coastal bivalve populations, there are environmental factors that influence their growth and reproductive success. This study was based on the monitoring campaigns of these bivalve banks, held annually by the IPMA, from 1999 to 2011, as well as environmental data of rainfall, an indicator of food availability (chlorophyll a), wind index and Sea surface Temperature (SST) over these 13 years. The objectives of this study are to analyze the variation of the spatial and temporal distribution of these species in the Western and Eastern Algarve, as well as to evaluate how the studied environmental parameters condition the abundance of the species concerned, in the following year, for the period before spawning and for the period after spawning + one month. Thus, annual distribution maps were elaborated for each species and region (Western and Eastern) and 16 linear models were applied to all four studied species, the two regions (Barlavento and Sotavento) and the study period ( three months before spawning and spawning + one month The results of this study showed that the distribution and abundance of these species varies over the years, revealing different patterns of banks in terms of preference or absence for each species, and that all the analyzed environmental factors were significant in determining their abundance, the following year. The most significant environmental parameters affecting abundance were the rainfall and the chlorophyll a levels, especially in the Western area. In general, increasing chlorophyll levels were beneficial in contributing to the abundance of species either breeding adults or growing larvae, while the most abundant rainfall levels were positive for adult populations, and negative to the early life stages of these bivalves. This study also shows the need to develop a better understanding of the relationship between the environmental parameters studied and the specific characteristic of the Algarve coast, so there can be a better management of the stocks, and an anticipated prediction of the populations’ growth, which will enable a better monitoring of these important bivalve communities.Artisanal fisheries in the Algarve are a very important industry for local communities and for the local economy. The target species in this fishery are the white clam (Spisula solida), the striped venus (Chamelea gallina), the donax clam (Donax trunulus) and razor clam (Ensis siliqua). The Portuguese Institute of the Sea and Atmosphere (IPMA) is responsible for the management of these fisheries and the existing resources, to ensure its sustainable development. It is known that in addition to the fishing pressure exerted on these coastal bivalve populations, there are environmental factors that influence their growth and reproductive success. This study was based on the monitoring campaigns of these bivalve banks, held annually by the IPMA, from 1999 to 2011, as well as environmental data of rainfall, an indicator of food availability (chlorophyll a), wind index and Sea surface Temperature (SST) over these 13 years. The objectives of this study are to analyze the variation of the spatial and temporal distribution of these species in the Western and Eastern Algarve, as well as to evaluate how the studied environmental parameters condition the abundance of the species concerned, in the following year, for the period before spawning and for the period after spawning + one month. Thus, annual distribution maps were elaborated for each species and region (Western and Eastern) and 16 linear models were applied to all four studied species, the two regions (Barlavento and Sotavento) and the study period ( three months before spawning and spawning + one month The results of this study showed that the distribution and abundance of these species varies over the years, revealing different patterns of banks in terms of preference or absence for each species, and that all the analyzed environmental factors were significant in determining their abundance, the following year. The most significant environmental parameters affecting abundance were the rainfall and the chlorophyll a levels, especially in the Western area. In general, increasing chlorophyll levels were beneficial in contributing to the abundance of species either breeding adults or growing larvae, while the most abundant rainfall levels were positive for adult populations, and negative to the early life stages of these bivalves. This study also shows the need to develop a better understanding of the relationship between the environmental parameters studied and the specific characteristic of the Algarve coast, so there can be a better management of the stocks, and an anticipated prediction of the populations’ growth, which will enable a better monitoring of these important bivalve communities

Estimating fishing effort in small-scale fisheries using high-resolution spatio-temporal tracking data (an implementation framework illustrated with case studies from Portugal)

Marta M. Rufino is funded by a DL57 contract (junior researcher) awarded by IPMA within the project “Real-time monitoring of bivalve dredge fisheries” (MONTEREAL, MAR-01.03.02-FEAMP-0022), funded by the Fisheries Operational Programme (MAR 2020) and co-financed by the European Maritime and Fisheries Fund (EMFF 2014–2020). João Samarão received a research grant (Ref: IPMA-2022-015-BII) awarded by IPMA within the framework of the project PESCAPANHA.Small-scale fisheries (SSF, boats < 12 m) represent 90% of this sector at a worldwide scale and 84% of the EU fleet. Mapping the areas and intensity where the fishing operations occur is essential for spatial planning, safety, fisheries sustainability and biodiversity conservation. The EU is currently regulating position tracking of SSF fishing vessels requiring precision resolved geo-positional data (sec to min resolution). Here we developed a series of procedures aimed at categorizing fishing boats behaviour using high resolution data. Our integrated approach involve novel routines aimed at (i) produce an expert validated data set, (ii) pre-processing of positional data, (iii) establishing minimal required temporal resolution, and (iv) final assessment of an optimized classification model. Objective (iv) was implemented by using statistical and machine learning (ML) routines, using novel combinations of fixed thresholds estimates using regression trees and classification methods based on anti-mode, Gaussian Mixture Models (GMM), Expectation Maximisation (EM) algorithms, Hidden Markov Models (HMM) and Random Forest (RF). Of relevance, the final evaluation framework incorporates both error quantification and fishing effort indicators. We tested the method by running through four SSF fisheries from Portugal recorded every 30 sec, with 183 boat trips validated, and concluded that the more robust time interval for data acquisition in these metiers should bePublisher PDFPeer reviewe

Improving fisheries management through spatio-temporal analysis of catches, discards, fishing effort and selectivity, across different métiers

I would first like to thank my advisers, especially Dr. Karim Erzini for helping me with the project change during the first of the PhD and for overall support since the beginning of my master’s project. I deeply admire your passion for fisheries research and the number of hours you have spent reviewing my writing. Thank you to Dr. Aida Campos for giving me an opportunity to expand my horizons in fisheries when I joined the TecPescas project and for support in and outside the PhD. Thank you to Dr. Jorge Gonçalves for the local support during the PhD, especially for helping me learn how to take care of the financial side of science. Finally, a thank you to Dr. Svein Løkkeborg in Norway for the original opportunity to collaborate with him prior to my change in the project and for the support during writing my first review. Thank you to all the fishers I worked with, and we interviewed for giving me the data that I needed to complete this PhD. A special thanks to the captain and crew of Mar Vivo, for a very wild experience on the sea and delicious fresh lunches. And to the captain and crew of Bartolomeu who worked with us on the trammel net project as I thoroughly enjoyed the dinners that I received from them and due to all of them being extremely friendly. A thank you to all my colleagues who worked with me at various periods of the PhD. Without your support I could not have finished my work. Thank you to Mariana Fernandes, Ana Marçalo and especially Pedro Monteiro for helping me grow as a researcher from the master’s until now. Thank you to all the people of Fisheries, Biodiversity and Conservation lab for all the help, for creating a general environment of friendliness and for making time to chat. Thank you so much to all my friends and to my husband that have also been there for me throughout the PhD. From getting coffees in the morning, to lunches in the afternoon, to those who were there from the beginning and to those I met later in the PhD program, as well as those who I’ve known from 6 to 15 years and have supported my dreams in science. Thank you to my parents who have supported my journey in science since I decided I was going to do a PhD in marine biology when I was only 13 years old. Thank you for the sacrifices you both made and for being role models in what hard and efficient work can mean, as well as taking pride in your work. Thank you to my sister who has been my cheerleader through the past years and especially during my periods of struggle, I am extremely thankful to have a sibling who cares so much to see me succeed. Thank you to my grandma for getting on skype almost every weekend and to my grandpa for making me laugh. (PL: Dziękuję mojej babci za to, że prawie w każdy weekend wchodziła na skype i słuchała mnie i mojemu dziadkowi za rozśmieszenie mnie.) Fishers in the Southern Portuguese multi-gear coastal fleet own licenses for a variety of fishing gears including static nets, longlines, and traps, and dredges. Information on the fishing gear being actively used is scarce and most vessels are not required to report geographic location, making the impact of the local environment difficult to evaluate. The first and main objective of this thesis was to identify métiers in the multi-gear coastal fisheries operating in the Portuguese south coast, including the type of gear being used to target specific species or assemblages in certain areas during a specific time of year in a three-step process. The first step was a review to understand the definition of fisheries métiers using static longlines due to their well-defined target species, little environmental impacts, and various characteristics that can be modified for improved fishing. This was followed by a cluster analysis on landing profiles for the fleet (2012-2016), followed by the second and third step in which validations using questionnaires and onboard observations, respectively. The main finding was the application of a low-cost analysis to identify métiers within a multi-gear fleet with limited data, and specific to this fleet, an increasing number of vessels active within the octopus (Octopus vulgaris) trap métier. The second objective was to assess a proposed raised trammel net (by insertion of a section referred to as “aranha”) to reduce by-catch and habitat impacts in the cuttlefish (Sepia officinalis) trammel net fishery. The results were promising as the modified net caught significantly less habitat forming organisms and similar target species’ amounts as the standard net. The results presented in this thesis can contribute to the management of this multi-gear fleet by presenting the necessary information to make decisions, especially for métiers with high number of vessels, and effort in highlighting the necessity for gear modifications in areas where the habitat is impacted.As embarcações da frota costeira polivalente que opera na costa sul portuguesa possuem geralmente várias licenças de pesca, incluindo redes de emalhar e de tresmalho, armadilhas, potes (alcatruzes), palangres de deriva e de fundo, e dragas. A informação existente sobre as artes efetivamente utilizadas e as áreas de operação é escassa, pois só um número muito reduzido de embarcações nesta frota está equipada com o sistema de monitorização das pescas (MONICAP e diários eletrónicos de pesca). Uma vez que a utilização de artes distintas resulta em grandes diferenças quer na composição das capturas, quer nos efeitos sobre os diferentes habitats, é difícil avaliar o impacte desta frota sobre o ecossistema onde opera. O primeiro e principal objetivo desta tese foi identificar os métiers desta frota, incluindo as artes de pesca utilizadas em determinadas áreas ao longo do ano e as espécies capturadas por estas artes. Para responder a este objetivo foi adotada uma abordagem em quatro etapas sequenciais (Capítulos 2 a 6). A primeira etapa visou melhorar a compreensão sobre o conceito de métier, através da revisão bibliográfica sobre os principais parâmetros operacionais que podem afetar as capturas em palangres de fundo e semi-pelágicos, artes de pesca consideradas altamente seletivas, ambas utilizadas pela frota polivalente costeira. A revisão bibliográfica (Capítulo 2) resultou na definição das características destas artes (tipo e tamanho do de anzol) e estratégias de pesca (tipo de isco e tempo de imersão) associadas a diversos métiers. Concluiu-se que a utilização de anzóis circulares melhora a seletividade e a eficiência de captura em diversas pescarias com esta arte, enquanto que o tempo de imersão não afetará de modo significativo estas características, embora isso possivelmente se deva ao fato de ser um parâmetro mascarado por outros parâmetros. Os resultados contribuem para futuros estudos que tenham como objetivo otimizar as estratégias de pesca com esta arte e melhorar a eficiência de captura. A segunda etapa (Capítulo 3) envolveu a utilização de técnicas de análise multivariada (Clustering Large Aplications, CLARA) com o objetivo de definir os perfis de desembarque para esta frota entre 2012 e 2016, identificando as principais espécies-alvo, bem como possíveis alterações sazonais na composição das capturas e ainda propondo, com base em conhecimento prévio, as artes de pesca utilizadas. A terceira etapa (Capítulo 4) foi dedicada à validação dos métiers propostos por meio de inquéritos/entrevistas nos portos, utilizando dois questionários, o primeiro contendo questões abertas sobre as características da viagem e das artes de pesca utilizadas, incluindo perguntas sobre as espécies-alvo, enquanto que o segundo visou a associação entre espécies-alvo e operações de pesca em perguntas fechadas. A comparação das respostas nos dois questionários permitiu avançar na identificação dos métiers. Na quarta etapa (Capítulo 5) procedeu-se a uma validação adicional dos métiers através de observações a bordo, onde foi registada a composição das capturas, juntamente com os detalhes e a localização geográfica das operações de pesca nos métiers amostrados. Os resultados dos Capítulos 3 a 5 apontam para a relevância de uma pescaria dirigida ao polvo (Octopus vulgaris) com alcatruzes e armadilhas, durante todo o ano, a profundidades até aos 100 metros, tendo sido definido um conjunto de espécies acessórias numa pescaria anteriormente conhecida como sendo mono-específica. Outros métiers importantes são a pescaria do tamboril (Lophius spp.) com redes de emalhar, no período do inverno ao verão, a profundidades até 400 metros; e da pescada branca (Merluccius merluccius) e a azevia (Microchirus spp.), também com redes de emalhar, durante todo o ano, a profundidades até 100 e 50 metros, respetivamente, com capturas acessórias mais reduzidas quando comparadas com as capturas reportadas em estudos anteriores sobre estes métiers. Os bivalves, incluindo o pé-de-burrinho (Chamelea gallina), a amêijoa-branca (Spisula solida) e as conquilhas Donax spp, são capturados com ganchorras, durante todo o ano. Por fim, o choco (Sepia oficinallis) e a canilha (Bolinus brandaris) são capturados com tresmalhos, o primeiro no inverno e na primavera e a segunda durante todo o ano. Estes resultados permitiram validar métiers propostos em estudos anteriores, embora os nossos resultados indiquem que mais de metade das embarcações se encontram envolvidas na captura de polvo, tendo alterado as suas licenças de pesca para incluir alcatruzes e armadilhas durante o período em análise. De um modo geral, as embarcações que operam redes alternam sazonalmente entre tresmalhos e redes de emalhar. No Capítulo 5, procedeu-se a uma caracterização mais aprofundada de alguns dos métiers propostos, tendo sido identificados alguns métiers adicionais envolvendo um número reduzido de embarcações. Um segundo objetivo desta tese (Capítulo 6) foi propor e testar modificações às artes para reduzir capturas acessórias e impactes negativos no ecossistema, concretamente na pesca de choco (Sepia officinalis) com redes de tresmalho, em áreas com fundos rochosos, onde as capturas acessórias de invertebrados são elevadas. As alterações à rede tradicionalmente utilizada consistiram na introdução de uma secção entre os panos de rede e o cabo dos chumbos, à qual os pescadores chamaram “aranha”, e que permitiu levantar a rede do fundo. Os resultados apontam para uma redução dos principais invertebrados (incluindo esponjas, corais, pepinos-do-mar e estrelas-do-mar), com alterações não significativas na captura das duas principais espécies-alvo, o choco e a azevia. As entrevistas que foram feitas após a análise permitiram recolher opiniões dos pescadores sobre a utilidade de uma futura implementação das alterações propostas, tendo oferecido uma solução que poderá ser testada no futuro. Os resultados apresentados nesta tese fornecem uma base para a identificação de métiers através de uma abordagem que envolve três etapas sequenciais. A informação obtida com a análise das atividades desta frota pode ser utilizada para avaliar o impacte no meio ambiente local de acordo com as artes de pesca efetivamente utilizadas. Os diferentes métodos de entrevista devem também ser considerados e, para fins futuros, os dois formulários utilizados podem ser reunidos num único formato. No entanto, reconheceu-se que a segunda rodada de questionários foi mais útil, pois forneceu respostas mais diretas às questões colocadas aos pescadores. Curiosamente, os resultados obtidos relativamente às rejeições ao mar foram diferentes daqueles esperados para as embarcações que operam com armadilhas e redes. Os resultados apresentados nesta tese podem ser utilizados na gestão desta frota polivalente, voltando potencialmente a atenção para o segmento da frota que visa o polvo, uma vez que este métier envolve mais de metade das embarcações ativas desta frota. Além disso, os ensaios de pesca experimental podem ajudar a gestão a avaliar os impactos das artes estáticas nas espécies formadoras de habitat e, ao apoiar futuros estudos com foco na captura acidental desses organismos, reduzir os impactos negativos da atividade da pesca.The primary data, landings by vessel, were provided by the Directorate-General for Natural Resources, Safety and Maritime Services (DGRM) and the DocaPesca Portos e Lotas SA of Portugal. The bottom sediment chart was accessed through Observation Data Network (EMODnet), Seabed Habitats initiative (www.emodnet-seabedhabitats.eu), financed by the European Union under Regulation (EU) No 508/2014 of the European Parliament and of the Council of 15 May 2014 on the European Maritime and Fisheries Fund. The remainder of the data used in this thesis was collected by the author with her colleagues within the framework of the project “TecPescas – Tecnologia da Pesca e Seletividade” (Mar2020 16-01-04-FMP-0010 – IPMA)

Bycatch in bivalve fisheries of Algarve

Dissertação de mestrado, Biologia Marinha, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2016The present study assessed bycatch in Algarve grid dredge fisheries and estimated fishing gear inflicted damage and mortality, with the purpose of formulating mitigation measures, specifically fishing gear modifications. Bycatch using this dredge has been shown to surpass target species catch and, although it would not be a major problem if the discarded individuals survive, it nonetheless creates an issue of concern for fishers. Fishing surveys were conducted bimonthly onboard commercial fishing vessels in the same coastal areas near Olhão, throughout six months, in order to ascertain seasonal variation. Fishing targeted commercially valuable clam species, either Donax trunculus, using the DDredge, or Spisula solida and Chamelea gallina, using the SDredge. All individuals captured were attributed scores from a damage table ranging from 1 to 4, where 1 or 2 equate organism survival and 3 or 4 mortality. Results showed significant differences between fisheries regarding total catch composition, confirming dredge capacity to maximize target catch, but none for bycatch, demonstrating similar benthic communities in all sampled sites. Bycatch reached a maximum of 57.5% in abundance, and was significantly higher using the DDredge. Damage and mortality, although overall low, varied as a result of the morphological characteristics of the taxa itself, as such Echinodermata was presented as most subject to damage. Higher percentages of bycatch in the DDredge indirectly led to higher mortality rates as well. Seasonality analysis indicated the influence of spring on an increase of bycatch abundance in the DDredge. The implementation of a BRD and net bag in the grid dredge are proposed to reduce bycatch, as well as its damage and mortality, while maintaining fishing yield. Comparative studies are advised as to evaluate BRD effects on catch composition, bycatch amount, mortality, and discard rates. Additionally, the re-evaluation of the damage table through survival experiments is recommended.A pesca acidental ou acessória é geralmente definida como a captura não intencional de organismos que não se enquadram na definição de captura alvo, por exemplo, indivíduos de espécies sem importância comercial ou juvenis das espécies alvo. A captura acessória inclui todos os indivíduos que são descartados para o mar, as rejeições e aqueles que, apesar de não serem considerados captura alvo, por qualquer outra razão sejam retidos e desembarcados. A pesca acessória é, assim, a diferença entre a captura total e a captura alvo. Portugal é um pequeno país com a terceira maior Zona Económica Exclusiva (ZEE) da União Europeia. As comunidades costeiras portuguesas dependem da pesca e de atividades com ela relacionadas como meio de subsistência, sendo estas uma forte componente do património cultural português. Apesar de a atividade pesqueira ser regulada por legislação própria, continua a ser um elemento perturbador dos ecossistemas e das comunidades marinhas. Este projecto focou-se na frota pesqueira que se dedica à captura de amêijoa branca (Spisula solida), pé-de-burrinho (Chamelea gallina) e conquilha (Donax trunculus) com ganchorra de grelha. A ganchorra de grelha é utilizada na pesca de bivalves ao longo da costa algarvia e em especial na área do presente estudo. Esta ganchorra é composta por uma boca com um pente de dentes na barra inferior, acoplada a uma armação de grelha metálica onde a captura é retida. Os indivíduos de pequenas dimensões, incluindo juvenis da espécie alvo, isto é, abaixo dos 25 mm de tamanho mínimo legal, escapam por entre as barras da grelha, enquanto a captura alvo e indivíduos maiores da captura acessória são mantidos e trazidos a bordo. Encontra-se demonstrado para o uso desta ganchorra uma redução da captura de juvenis da espécie-alvo e uma rápida recuperação dos indivíduos que escapam através das barras da grelha. No entanto, a sua utilização acarreta consequências, já que esta arte de pesca não é tão seletiva como seria desejável, promovendo capturas acessórias e, consequentemente, rejeições. O presente trabalho tem como objetivo avaliar a importância das capturas acessórias na pesca de bivalves com ganchorra de grelha no Algarve, determinar o dano e mortalidade causados por esta arte de pesca à captura total, aferir a existência de sazonalidade e propor medidas que minimizem a pesca acidental. Tais objetivos foram alcançados através da quantificação das capturas acessórias obtidas com ganchorras de grelha com diferentes espaçamentos entre as barras paralelas, 8 mm para a captura de D. trunculus (DDredge) e 12 mm para S. solida e C. gallina (SDredge). A amostragem decorreu duas vezes por mês, entre Fevereiro e Julho, a bordo de embarcações de pesca comercial na costa algarvia perto de Olhão. A determinação da mortalidade de cada indivíduo foi calculada através da atribuição de uma escala de dano de 1 a 4, em que 1 ou 2 implicam a sobrevivência do organismo rejeitado e 3 e 4 a sua morte. Foram encontradas diferenças significativas entre a composição das capturas totais das duas ganchorras, confirmando a capacidade de cada ganchorra maximizar a captura da sua respectiva espécie alvo. Porém, nenhuma diferença foi encontrada entre a composição da captura acessória, demonstrando a presença de comunidades bentónicas semelhantes em todos os locais de amostragem. A captura acidental atingiu um máximo de 57.5% em abundância e 35.1% em biomassa e foi significativamente maior usando a DDredge, devido à menor abundância da espécie alvo. Dano e mortalidade, embora baixos, variaram em resultado das características morfológicas de cada taxa. As espécies alvo mostraram, em geral, baixas mortalidades devido à natureza resistente das conchas destas espécies de bivalves, com S. solida como mais resistente e D. trunculus mais susceptível a dano. Tanto na pescaria de S. solida e C. gallina como na de D. trunculus, Echinodermata foi o phylum com maior mortalidade e dano, em particular a classe Echinoidea, devido à sensibilidade a dano mecânico das placas fundidas que compõem estes organismos. Elevadas percentagens de capturas acessórias na DDredge causaram, assim, indiretamente taxas de mortalidade significativamente maiores, já que se verificou menor abundância de espécies resistentes a dano. Análises de sazonalidade indicaram o aumento da abundância das capturas acessórias na DDredge desde o Inverno até à Primavera. Não foram observadas diferenças significativas entre o Verão e as restantes estações, presumivelmente devido ao baixo tamanho da amostra causado pelo fecho da pesca durante esses meses. Porém, visto que outros autores indicaram também a presença de sazonalidade na abundância das capturas da ganchorra de grelha, especificamente durante o Outono, torna-se evidente a necessidade de estudos adicionais que explorem estas variações. Recomenda-se a implementação de um aparelho que reduza a proporção de rejeições (BRD) na ganchorra de grelha. Este BRD consiste numa grelha articulada diagonalmente posicionada na armação metálica da ganchorra e na criação de uma abertura no topo da mesma. O espaçamento entre as barras da grelha do BRD deverá ser largo o suficiente para a permitir a entrada e retenção da espécie alvo, mas estreito de modo a prevenir a entrada de indivíduos da captura acessória de maiores dimensões, excluindo-os através da abertura mencionada. No entanto, é indispensável que esta alteração à ganchorra não cause redução no rendimento de pesca. Propõe-se, assim, que a grelha posterior da ganchorra seja eliminada e um saco de rede acoplado. Desta forma evita-se a perda de captura alvo pela abertura no topo da armação metálica durante a recolha da ganchorra, o único momento da operação de pesca em que esta se encontra numa posição vertical. Prevê-se que, com estas alterações, as rejeições sejam reduzidas, bem como o dano e mortalidade causados pela ganchorra de grelha, visto que a imediata exclusão de organismos lhes permitirá rápida recuperação de atividade e menor risco de predação. Estudos comparativos que avaliem o efeito das modificações propostas são aconselhados. Deste modo, deverá proceder-se ao arrasto simultâneo de ganchorras com e sem BRD, de modo a avaliar os efeitos do mesmo no rendimento de pesca, composição das capturas, proporção de capturas acessórias, mortalidade e taxas de rejeição. Recomenda-se também a reavaliação da tabela de danos usada através de experiências de sobrevivência

Environmental impact and sustainability of portuguese fisheries

Tese de doutoramento, Biologia (Biologia Marinha), Universidade de Lisboa, Faculdade de Ciências, 2009Assess fishing impacts on marine ecosystem and fisheries sustainability is essential to achieve proper management of the sector and for the conservation of resources and marine ecosystem. The main fishing impacts (bycatch, namely of protected species, discards, and impacts on habitats and on marine trophic web) of seven Portuguese fisheries were assessed. The ecological impact requiring more urgent attention was bycatch, which in some cases led to significant amounts of discards. In particular, it was analyzed the elasmobranchs bycatch in trammel nets fishery, which constituted an important part of the total biomass caught and of the individuals discarded, and the impact of nets loss in the marine environment, which continue to fish for a relatively long periods of time, especially in rocky bottom. We also observed changes in the marine trophic web of Portuguese waters by analysis of the mean trophic level of national landings. The analysis of the sustainability of the national fisheries sector has shown that, in general, it has increased in recent years, although at a higher rate in economic and institutional dimensions than in ecological and social dimensions. The traditional fisheries of the Tagus estuary showed an intermediate sustainability, making clear the need for intervention. The Portuguese fisheries management measures were assessed considering their effects on commercial species, verifying that in general they have not the desired effects and that the current management model should be changed. Marine protected areas have been suggested as a tool for fisheries management. A methodology to assess their effectiveness in the small fisheries sustainability was developed and applied to the marine area of the Natural Park of Arrábida, for which there is only improvements in ecological and management areas.Assess fishing impacts on marine ecosystem and fisheries sustainability is essential to achieve proper management of the sector and for the conservation of resources and marine ecosystem. The main fishing impacts (bycatch, namely of protected species, discards, and impacts on habitats and on marine trophic web) of seven Portuguese fisheries were assessed. The ecological impact requiring more urgent attention was bycatch, which in some cases led to significant amounts of discards. In particular, it was analyzed the elasmobranchs bycatch in trammel nets fishery, which constituted an important part of the total biomass caught and of the individuals discarded, and the impact of nets loss in the marine environment, which continue to fish for a relatively long periods of time, especially in rocky bottom. We also observed changes in the marine trophic web of Portuguese waters by analysis of the mean trophic level of national landings. The analysis of the sustainability of the national fisheries sector has shown that, in general, it has increased in recent years, although at a higher rate in economic and institutional dimensions than in ecological and social dimensions. The traditional fisheries of the Tagus estuary showed an intermediate sustainability, making clear the need for intervention. The Portuguese fisheries management measures were assessed considering their effects on commercial species, verifying that in general they have not the desired effects and that the current management model should be changed. Marine protected areas have been suggested as a tool for fisheries management. A methodology to assess their effectiveness in the small fisheries sustainability was developed and applied to the marine area of the Natural Park of Arrábida, for which there is only improvements in ecological and management areas

Oceanography

How inappropriate to call this planet Earth when it is quite clearly Ocean (Arthur C. Clarke). Life has been originated in the oceans, human health and activities depend from the oceans and the world life is modulated by marine and oceanic processes. From the micro-scale, like coastal processes, to macro-scale, the oceans, the seas and the marine life, play the main role to maintain the earth equilibrium, both from a physical and a chemical point of view. Since ancient times, the world's oceans discovery has brought to humanity development and wealth of knowledge, the metaphors of Ulysses and Jason, represent the cultural growth gained through the explorations and discoveries. The modern oceanographic research represents one of the last frontier of the knowledge of our planet, it depends on the oceans exploration and so it is strictly connected to the development of new technologies. Furthermore, other scientific and social disciplines can provide many fundamental inputs to complete the description of the entire ocean ecosystem. Such multidisciplinary approach will lead us to understand the better way to preserve our "Blue Planet": the Earth