Browsing by Author "Costa, Ana Maria"
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- ANÁLISE DA AMOSTRAGEM BIOLÓGICA DE PESCADA (Merluccius merluccius) PROVENIENTE DAS CAMPANHAS DEMERSAIS DE OUTONO ENTRE 1990 E 2013Publication . Costa, Ana Maria; Instituto Português do Mar e da AtmosferaThis work was carried out in order to compile the results obtained with the biological sampling of hake from the information collected in demersal autumn surveys conducted from 1990 to 2013 under the PNAB/EU DCR-Data Collection Regulation. 71817 individuals were analyzed and three geographical areas were considered, northwest (NW), south west (SW) and south (S). In each zone the length distributions and the sex ratio, with their distributions in depth, were studied; the percentage of maturity stages, the maturity ogives and the length at the 1st maturity were also estimated for each zone. There was a predominance of males in the length classes below 40 cm and of females above 50 cm. The values of the L50 varied in the NW coast between 21 cm (in 2008) and 74.9 cm (in 1994), in the SW coast between 18.6 cm (in 2008) and 51.5 cm (in 1990) and in the S coast between 11.3 cm (in 2010) and 61.7 cm (in 1996), showing a slight decreasing trend in recent years.
- FIRST STEP FOR IMPLEMENTATION OF VISUAL ASSESSMENT OF THE MESENTERIC FAT CONTENT OF HORSE MACKEREL, TRACHURUS TRACHURUS (LINNAEUS, 1758), IN THE PORTUGUESE COASTPublication . Costa, Ana Maria; Instituto Português do Mar e da AtmosferaThe objective of this study was to visually obtain the amount of mesenteric fat content and its relationship with length and maturity cycle of horse mackerel in three different regions. Between January and December 2015, a total of 3124 individuals (1467 males, 1439 females and 218 unsexed or indeterminate) were collected at Matosinhos, Peniche and Portimão fish auctions, with total lengths between 11.1 and 43.9 cm. A sex ratio of 1:0.98 in favor of males was obtained, with small non-significant differences in fat content between sexes. A significant inverse relationship was found between the amount of mesenteric fat and the phase of the maturity cycle, corresponding also to a significantly relationship between fat and fish condition. During the spawning season, in the 1st quarter of the year, most of the fish had practically no mesenteric fat, whereas in the resting season, corresponding to the summer months, the individuals presented the highest fat content. During the summer months the leanest specimens were recovering, while the highest fat content was recorded in maturing individuals. These observations were common to the three zones studied. The visual assessment of the amount of mesenteric fat is a quick and easy technique, well-suited for use at sea, in opposition to the determination of lipid content, which is more expensive and time consuming.
- Report of the Workshop on Sampling Design and Optimization of fisheries data - WKSDOPublication . Azevedo, Manuela; Silva, Cristina; Vølstad, Jon Helge; Prista, Nuno; Alpoim, Ricardo; Moura, Teresa; Figueiredo, Ivone; Dias, Marina; Fernandes, Ana Cláudia; Lino, Pedro G.; Felício, Mónica; Chaves, Corina; Soares, Eduardo; Dores, Sandra; Gonçalves, Patrícia; Costa, Ana Maria; Nunes, Cristina; Instituto Português do Mar e da Atmosfera, I.P.O “Workshop on Sampling Design and Optimization (WKSDO)”, presidido pelas investigadoras Cristina Silva e Manuela Azevedo (IPMA) e o investigador Norueguês Jon H. Vølstad (IMR), decorreu no IPMAAlgés, de 17 a 20 de Novembro de 2014, para analisar o actual Programa Nacional de Amostragem Biológica (PNAB/Data Collection Framework) com o objectivo de optimizar o programa de amostragem em lota para estimação da composição por comprimento da captura/desembarque das espécies capturadas pela frota nacional, de amostragem das capturas a bordo e da amostragem biológica para estudos de crescimento e reprodução. O Workshop, organizado no âmbito do projecto de investigação nacional GesPe (Planos de Gestão Pesqueira, PROMAR) e do PNAB/DCF, foi planeado e calendarizado tendo em conta o início do processo de revisão do programa Europeu de recolha de dados da pesca de suporte à avaliação e gestão dos recursos pesqueiros (DFC). Foram analisados e discutidos vários métodos e abordagens que resultaram num conjunto de instruções e recomendações para trabalho futuro, relevantes para assegurar uma elevada qualidade e optimização do futuro programa de amostragem.
- Validation of the macroscopic maturity stages for blue jack mackerel, Trachurus picturatus (Bowdich, 1825), according to histological examinationPublication . Feijó, Diana; Silva, Carmo Nunes; Correia, Georgina; Inácio, Mónica; Abreu, Paula; Costa, Ana Maria; Instituto Português do Mar e da AtmosferaThe assessment of fisheries resources requires the correct identification of fish maturity stages. The methodologies applied should be standardised and all uncertainty regarding macroscopic identification should be validated by microscopic observation. This work proposes a microscopic maturity scale for the blue jack mackerel (Trachurus picturatus, Bowdich, 1825), based on individuals collected by commercial bottom trawl in northern Portugal. After assigning the macroscopic maturity stage, the gonads were processed for histological observation. The slides were observed and the gonads were classified into 6 stages according to Walsh et al. (1990). The corresponding macroscopic and microscopic maturity stages were described. The correspondence to the new maturity scale presented at WKASMSF (ICES, 2018) is also presented, which is mandatory when reporting maturity data to ICES databases (since the 1st. January 2020).
- VARIAÇÃO DO COMPRIMENTO DA PESCADA NA PRIMEIRA MATURAÇÃO ENTRE 2000 E 2010 NA COSTA PORTUGUESAPublication . Costa, Ana Maria; I.P.Neste trabalho foi estimado o tamanho da pescada (Merluccius merluccius), na primeira maturação, na costa portuguesa pertencente à área de distribuição do stock sul (Divisões VIIIc e IXa do ICES). Os dados recolhidos nos cruzeiros de primavera e outono de 2000 a 2010 foram analisados numa base anual, considerando em separado fêmeas, machos e sexos combinados. O L50 foi sempre superior para as fêmeas, com um valor médio de 41,3 cm para todos os anos estudados, e de 27,1 cm para os machos, o que se traduziu num comprimento médio de 34,5 cm dos dois sexos na primeira maturação para o período 2000-2010. Foram também analisados os valores da temperatura da superfície do mar, que registaram uma média de 16,7º C para este período.
- WHY DO WE NEED HISTOLOGY OF HAKE (MERLUCCIUS MERLUCCIUS) GONADS? THE PORTUGUESE CASEPublication . Costa, Ana Maria; Silva, Maria do Carmo; Instituto Português do Mar e da AtmosferaWith a monthly sampling frequency between 2010 and 2013, 4238 fish were collected and their gonads were macroscopically and microscopically staged. The percentages of error encountered with the macroscopic assignments were analysed by sex, length class and month, both for all stages together and for stage 1 separately, where the highest percentages of error are found on the identification of the immature stages that in fact were already mature. When considering all the individuals the highest errors occurred in the females (11%), in the length classes of 28 and 40 cm (26% and 25%, respectively) and in June (17%). The greatest misidentifications of maturity stage 1 were verified in males in length classes under 32 cm (92%) and over 57 cm (100%) and in the months of June, July and October (100%). The L50 decreased 8.1 cm (from 34.4 to 26.3 cm) with the microscopic identification, considering combined sexes and 2.3 cm (from 40.6 to 38.3 cm) only in females.
- WORKSHOP DO PNAB: ATRIBUIÇÃO DE ESTADOS DE MATURAÇÃO MACROSCÓPICOS A GÓNADAS DE PEIXESPublication . Costa, Ana Maria; Instituto Português do Mar e da Atmosfera, I.P.The macroscopic maturity scales workshop was held between 31st of January and 3rd of February 2017, at IPMA Matosinhos and was attended by 21 participants, distributed into 4 groups, according to the level of knowledge of each in the classification of the biology of each species. The maturity stages of fresh and frozen samples of horse mackerel (Trachurus trachurus Linnaeus, 1758), blue jack mackerel (Trachurus picturatus Bowdich, 1825), Atlantic mackerel (Scomber scombrus Linnaeus, 1758) and chub mackerel (Scomber colias Gmelin, 1789) were assigned according to the macroscopic scale of Walsh et al. (1990). The highest mean percentage of disagreement was recorded for the frozen samples, 27.3%, versus 22.5% for the fresh samples. The percentages of agreement with the reference stages varied between 92.5% in the females stage 2 (F2, beginning of develop) of the fresh samples and 98.0% in the males stage 1 (M1, immature) of the frozen samples. In all the species the greatest doubts arose in the distinction between spawners (stage 4) and post-spawners (stage 5). From this work it was concluded that the attribution of the macroscopic maturity stages should be preferably done in fresh fish and it is recommended to repeat this workshop in another season of the year to observe the other maturity stages.