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- Age and growth of the blue jack mackerel, Trachurus picturatus Bowdich, 1825 (Pisces: Teleostei) off Madeira archipelagoPublication . Vasconcelos, Joana; Alves, Adriana; Gouveia, Elisabete; Faria, GraçaBetween 1984 and 1986, 630 pairs of sagitta otoliths were collected to determine the age and growth of the blue jack mackerel, Trachurus picturatus from Madeiran waters. The oldest specimen in this study was nine years old and the largest was 46 cm of total length (TL). The parameters of the von Bertalanffy growth curve were estimated for the whole period studied for all fish (L∞=42.32 cm, k=0.161 year-1, t0= -2.563 year; r2=0.743) for males (L∞=39.57 cm, k=0.194 year-1, t0=-2.282 year; r2=0.722) and for females (L∞=49.78 cm, k=0.114 year-1, t0=-3.052 year; r2 = 0.747). There was no significant differences in mean lengths (t–test, p>0,05) and in the von Bertalanffy growth curves (F test, p>0,05) between sexes. The validity of otolith readings for estimating age and growth was supported by results from backcalculation method. No significant differences were found in the Bertalanffy growth curves between direct reading of otoliths and backcalculation. Growth parameters estimated from backcalculated sizes-at-age were: for both sexes, L∞=48.28 cm, k=0.135 year-1, t0=-2.898 year and r2=0.999; for males, L∞=44.79 cm, k=0.143 year-1, t0=-3.207 year, r2=0.999; and females, L∞=44.63 cm, k=0.163 year-1, t0=-2.430 year, r2=0.999. The relationship between length and weight was calculated for all fish (Wt=0.00764Lt3.05746; r2=0.951), for males (Wt=0.01271Lt2.90807; r2=0.915) and for females (Wt=0.00604Lt3.12613; r2=0.948).
- Endoparasites of Trachurus picturatus (Pisces: Carangidae) from the Madeira and Canary Islands: selecting parasites for use as tagsPublication . Costa, Graça; Garcia Santamaria, Maria Teresa; Vasconcelos, Joana; Borges Perera, Clara; Moreira, Egberto MeloIn order to evaluate the use of parasites as biological tags to identify populations of the oceanic horse mackerel, Trachurus picturatus, two samples of 100 fish each, caught off the Madeira and Canary Islands from January to June 2009, were examined for the presence of anisakids, trypanorhynchs, acanthocephalans and liver coccidians. In T. picturatus from Madeira, prevalence of the coccidian Goussia cruciata reached 82%, whereas prevalence of the nematode Anisakis sp., the acanthocephalan Rhadinorhynchus cadenati and the trypanorhynch Nybelinia lingualis were 12.0%, 8.9% and 7.0%, respectively. In samples from the Canary Islands, prevalence of G. cruciata was 8.0%, Anisakis sp. and R. cadenati reached 5.0% and 42.0% respectively, and N. lingualis was not recovered. The absence of N. lingualis and the lower prevalence of Anisakis sp. appear to be related to the smaller size of the oceanic horse mackerels examined from the Canary Islands. Although significant differences in prevalence of two parasites, G. cruciata and R. cadenati, were found between the two regions investigated (χ2=125.13, df=1, p=0.000 and χ2=40.77, df=1, p=0.000), only G. cruciata was considered useful as a biological tag for the identification of populations of T. picturatus. In order to reach sound conclusions, an expansion of the temporal and spatial sampling strategy is recommended.
- The use of parasites as biological tags for stock identification of Blue Jack Mackerel, Trachurus picturatus, in the North-eastern AtlanticPublication . Vasconcelos, Joana; Hermida, Margarida; Saraiva, Aurélia; González, José Antonio; Gordo, Leonel SerranoThe use of parasites as biological tags for discriminating stocks of blue jack mackerel, Trachurus pic turatus (Osteichthyes, Carangidae), in the northeast Atlantic Ocean is assessed herein. In this study the following parasites have been selected as possible biological tags: Anisakis spp. (Nematoda: Anisakidae), Rhadinorhynchus sp. (Acanthocephala: Rhadinorhynchidae), Nybelinia sp. (Cestoda: Tentaculariidae) and Bolbosoma sp. (Acanthocephala: Polymorphidae). Anisakis spp. was the most prevalent parasite taxon found in all localities, attaining higher values in fish from Peniche, mainland Portugal. The occurrence of Rhadinorhynchus sp. in fish from all studied areas was rare (prevalence <10%) but significantly different between localities, with higher values in both archipelagos. Nybelinia sp. specimens were only detected in fish from Madeira and cystacanths ofthe genus Bolbosoma were never detected. The distinctive pattern of infection of these parasite species points to the existence of three stocks of blue jack mackerel in the northeast Atlantic: one in Portuguese mainland waters, one in Madeira archipelago and another in the Canary archipelago. These results support the management strategy which treats the three populations studied as separate stocks.
- Estrutura populacional do Chicharro, Trachurus picturatus do Atlântico NordestePublication . Vasconcelos, Joana Patrícia Reis; Kaufmann, Manfred; Gordo, Leonel SerranoEsta dissertação abordou duas temáticas principais: a identificação da estrutura do stock de chicharro, Trachurus picturatus (Bowdich, 1825), no sul do Atlântico nordeste e o estudo dos parâmetros de história de vida para a população da Madeira. A estrutura do stock de chicharro ainda é desconhecida e para identificar as unidades populacionais, foram selecionadas três áreas, Madeira, Portugal continental e Canárias, e utilizadas várias metodologias: morfologia do contorno do otólito, morfologia do corpo e análise parasitológica. Na primeira, foram analisados 100 otólitos por área, tendo os resultados da análise aos descritores elípticos de Fourier normalizados (NEFDs) revelado diferenças significativas entre as três áreas (classificação geral de 86.3%). Relativamente à morfologia do peixe, a atribuição de espécimes às localizações geográficas em estudo foi classificada corretamente em 80.7% das amostras (K = 0.67). Estes resultados juntamente com o padrão de infeção dos parasitas Anisakis spp., Rhadinorhynchus sp. e Nybelinia sp. confirmaram a distinção de 3 unidades populacionais no sul do Atlântico nordeste. Nos parâmetros de história de vida, a idade foi determinada a partir de 1405 espécimes, colhidos entre 2009 e 2010. A verificação das leituras foi efetuada segundo a análise do incremento marginal e a evolução mensal do tipo de bordo. Os resultados mostraram a existência de dois anéis por ano, tendo sido atribuídos sete grupos de idade (0-6). Não se verificaram diferenças significativas entre sexos nos comprimentos médios à idade e nas curvas de crescimento de von Bertalanffy. Os parâmetros de crescimento estimados foram: L∞ = 27.98 cm, k = 0.266 ano-1 e t0 = -2.713 ano. A relação peso-comprimento estimada para todos os indivíduos foi de Wt = 0.00411Lt3.230. A época de desova estendeu-se de janeiro a abril. A espécie atinge a maturidade sexual no primeiro ano com comprimentos de 17.06 e 17.04 cm para fêmeas e machos respetivamente.