Browsing by Author "Assis, Carlos"
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- Adding Value to Bycatch Fish Species Captured in the Portuguese Coast—Development of New Food ProductsPublication . Silva, Frederica; Duarte, Ana M.; Mendes, Susana; Borges, Patrícia; Magalhães, Elisabete; Pinto, Filipa R.; Barroso, Sónia; Neves, Ana; Sequeira, Vera; Vieira, Ana Rita; Magalhães, Maria Filomena; Sampaio e rebelo, Rui; Assis, Carlos; Gordo, Leonel Serrano; Gil, Maria ManuelWe live in a world of limited biological resources and ecosystems, which are essential to feed people. Consequently, diversifying target species and considering full exploitation are essential for fishery sustainability. The present study focuses on the valorization of three low commercial value fish species (blue jack mackerel, Trachurus picturatus; black seabream, Spondyliosoma cantharus; and piper gurnard, Trigla lyra) and of two unexploited species (comber, Serranus cabrilla and boarfish, Capros aper) through the development of marine-based food products with added value. A preliminary inquiry with 155 consumers from Região de Lisboa e Vale do Tejo (Center of Portugal) was conducted to assess fish consumption, the applicability of fish product innovation, and the importance of valorizing discarded fish. Five products (black seabream ceviche, smoked blue jack mackerel pâté, dehydrated piper gurnard, fried boarfish, and comber pastries) were developed and investigated for their sensory characteristics and consumer liking by hedonic tests to 90 consumers. The most important descriptors were identified for each product (texture, flavor, color, and appearance). Comber pastries had the highest purchase intention (88%), followed by black seabream ceviche (85%) and blue jack mackerel pâté (76%). Sensory evaluations showed a clear tendency of consumers to accept reformulated products, with the introduction of the low-value and unexploited species under study.
- Enhancing knowledge on low‐value fishing species: the distinct reproductive strategy of two gurnard speciesPublication . Neves, Ana; Sousa, Inês; Sequeira, Vera; Vieira, Ana Rita; Silva, Elisabete; Silva, Frederica; Duarte, Ana Marta; Mendes, Susana; Ganhão, Rui; Assis, Carlos; Sampaio e rebelo, Rui; Magalhães, Maria Filomena; Gil, Maria Manuel; Gordo, Leonel SerranoThe depletion and overexploitation of several fish stock demands for a valorisation of non-target and discarded species. Nonetheless, such species are often poorly studied, and information on their biological parameters must be gathered for effective population management. For 1 year, the reproductive strategy of the piper gurnard Trigla lyra and the red gurnard Chelidonichthys cuculus was studied by monthly samples obtained from commercial boats operating on western Portuguese coast. Both species showed a biased sex ratio towards females, especially for larger length classes. Length at first maturity could be estimated only for red gurnard (22.1 and 19.9 cm for females and males, respectively) because all piper gurnard individuals caught were mature. Piper gurnard showed determinate fecundity and a short spawning season, from November to February with a peak in January, whereas red gurnard showed indeterminate fecundity and a wide spawning season, from late December to May. The relative annual fecundity estimated for red gurnard (1893 ± 728 oocytes × g−1 eviscerated weight [EW]) was higher than the one estimated for piper gurnard (1018 ± 250 oocytes×g−1 EW). Although important information for understanding the species dynamics is presented in this study, additional information on other life-history parameters and of species landings is required.
- Estudo morfológico dos otólitos Sagitta, Asteriscus e Lapillus de teleósteos (Actinopterygii, teleostei) de Portugal ContinentalPublication . Assis, Carlos; Costa, Maria José Rosado, 1947-Os otólitos são concreções acelulares de carbonato de cálcio e outros sais inorgânicos, que se desenvolvem sobre uma matriz proteica no ouvido interno dos vertebrados. Nos peixes ósseos, os otólitos são em número de três pares, sagittae, asterisci e lapilli, e atingem normalmente dimensões apreciáveis, preenchendo quase completamente a cavidade interna dos três principais compartimentos do labirinto membranoso, sacculus, lagena e utriculus, respectivamente. Entre os três pares de otólitos, os sagittae estão actualmente bastante bem estudados, encontrando-se entre as peças anatómicas dos peixes que maior utilidade têm, e cujo estudo um maior número de aplicações permite. Tais aplicações não se limitam ao domínio da ictiologia, mas estendem-se amplamente a alguns aspectos dos domínios da Paleontologia, Mamalogia, Ornitologia, Arqueologia e Zoogeografia. Em contrapartida, os outros dois pares de otólitos têm sido quase completamente negligenciados pelos ictiologistas, pouco se sabendo actualmente sobre a sua morfologia. O presente trabalho apresenta alguns dos resultados de um estudo morfológico dos três pares de otólitos, baseado em amostras de 183 espécies, distribuídas por 22 ordens e 63 famílias de peixes ósseos das águas costeiras, estuarinas e continentais portuguesas. Ao longo dele, (1) é apresentada a morfologia básica dos três pares de otólitos dos peixes; (2) são elaboradas propostas de uniformização e pormenorização da terminologia actualmente adoptada para os otólitos sagitta; (3) é proposta uma terminologia para as partes e estruturas dos asterisci e lapilli consideradas como importantes para a caracterização desses pares de otólitos; (4) é pormenorizadamente descrita a morfologia dos três pares de otólitos de algumas das espécies (119) representadas na colecção de referência organizada; (5) são fornecidas chaves para a identificação de cada uma dessas espécies, utilizando exclusivamente as características morfológicas dos seus otólitos; (6) é feito um estudo sumário da variabilidade intra-específica das características dos otólitos, para as espécies em que foram obtidas amostras com alguma representatividade; (7) são deduzidas expressões matemáticas que permitem a realização de estimativas do tamanho de exemplares das espécies estudadas, a partir das dimensões dos seus otólitos; e (8) são discutidas as potencialidades da utilização dos três pares de otólitos, em especial dos asterisci e lapilli, em estudos de Filogenia, Sistemática e Ecologia.
- Ichthyological collection of the Museu Oceanográfico D. Carlos IPublication . Silva, Ana Serra; Pitta Groz, Maria; Leandro, Paula; Assis, Carlos; Figueira, RuiThe collection of the Museu Oceanográfico D. Carlos I is a historical specimen, instrument, and document collection that has been housed at the Aquário Vasco da Gama since 1935. The collection is largely the result of several scientific campaigns conducted by Dom Carlos de Bragança between 1896 and 1907. Specifically, the ichthyological collection consists of 675 surviving catalogue records of specimens caught, acquired or offered to D. Carlos I between 1892 to 1907, and includes the type specimen for Odontaspis nasutus Bragança, 1904 (junior synonym of Mitsukurina owstoni Jordan, 1898), along with several specimens of deep sea species. All specimens were captured in coastal Portuguese waters, and were preserved in alcohol, formalin, or mounted.
- Life cycle, distribution and trophodynamics of the lanternfish Krefftichthys anderssoni (Lönnberg, 1905) in the Scotia SeaPublication . Lourenço, Sílvia; Saunders, Ryan A.; Collins, Martin; Shreeve, Rachel; Assis, Carlos; Belchier, Mark; Watkins, Jonathan L.; Xavier, JoseMyctophid fish play an important role in the Southern Ocean pelagic food web. The lanternfish Krefftichthys anderssoni is one of the most common myctophids in the region, but its ecology is poorly known. This study examines spatial and temporal patterns in the species distribution of density, life cycle, population structure and diet using samples collected by mid-water trawl nets deployed in different seasons across the Scotia Sea. Virtually absent from the sea-ice zone, the species was most abundant in the northern Scotia Sea around the Georgia Basin at depths below 400 m that are associated with the Circumpolar Deep Water. The species migrated during night from waters deeper than 700 m to waters above the 400 m following their main prey species: the copepods Rhincalanus gigas and Calanoides acutus and euphausiids of the Thysanoessa genus. Larvae length distribution and post-larvae length-frequency analyses suggested a life cycle of ~ 3 years with spawning and recruitment strongly connected with APF and the South Georgia shelf. Our results show that species spatial distribution, population structure and diet changed both seasonally and ontogenetically. This study is the most comprehensive examination of the ecology of K. anderssoni in the Southern Ocean to date and contributes to resolving how pelagic food webs and ecosystems operate in the region.
- Mark-recapture abundance estimate of tucuxi dolphins (Sotalia fluviatilis) in a lake system of the Central AmazonPublication . Coimbra, Zulmira H.; Assis, Carlos; da Silva, Vera M. F.; dos Santos, Manuel E.The tucuxi (Sotalia fluviatilis) is a small dolphin endemic to the Amazon River basin. Because the abundance and trends are currently unknown for the species, this study aimed to estimate its abundance in a lake system of the Central Amazon. A total of 10 two-day sampling periods were carried out from March to June of 2013 throughout a 13.5 km2 area in the Mamirauá Reserve. In the 104 encounters with the species, a minimum number of 389 dolphins were sighted and photographed, which allowed the positive identification of 49 individuals. Mark-recapture models were used to estimate an abundance of 119 individuals (95% CI = 105–150) (corrected for the proportion of identifiable individuals). This is the first estimation of S. fluviatilis abundance using mark-recapture analyses and, together with the photo-id catalog made available, provides a useful reference for future studies regarding tucuxi dolphins.
- Modelling Fish Growth with Imperfect Data: The Case of Trachurus picturatusPublication . Neves, Ana; Vieira, Ana Rita; Sequeira, Vera; Silva, Elisabete; Silva, Frederica; Duarte, Ana Marta; Mendes, Susana; Ganhão, Rui; Assis, Carlos; Sampaio e rebelo, Rui; Magalhães, Maria Filomena; Gil, Maria Manuel; Gordo, Leonel SerranoGrowth modelling is essential to inform fisheries management but is often hampered by sampling biases and imperfect data. Additional methods such as interpolating data through back-calculation may be used to account for sampling bias but are often complex and time-consuming. Here, we present an approach to improve plausibility in growth estimates when small individuals are under-sampled, based on Bayesian fitting growth models using Markov Chain Monte Carlo (MCMC) with informative priors on growth parameters. Focusing on the blue jack mackerel, Trachurus picturatus, which is an important commercial fish in the southern northeast Atlantic, this Bayesian approach was evaluated in relation to standard growth model fitting methods, using both direct readings and back-calculation data. Matched growth parameter estimates were obtained with the von Bertalanffy growth function applied to back-calculated length at age and the Bayesian fitting, using MCMC to direct age readings, with both outperforming all other methods assessed. These results indicate that Bayesian inference may be a powerful addition in growth modelling using imperfect data and should be considered further in age and growth studies, provided relevant biological information can be gathered and included in the analyses.
- Modelling Fish Growth with Imperfect Data: The Case of Trachurus picturatusPublication . Neves, Ana; Vieira, Ana Rita; Sequeira, Vera; Silva, Elisabete; Silva, Frederica; Duarte, Ana Marta; Mendes, Susana; Ganhão, Rui; Assis, Carlos; Sampaio e rebelo, Rui; Magalhães, Maria Filomena; Gil, Maria Manuel; Gordo, Leonel SerranoGrowth modelling is essential to inform fisheries management but is often hampered by sampling biases and imperfect data. Additional methods such as interpolating data through back-calculation may be used to account for sampling bias but are often complex and time-consuming. Here, we present an approach to improve plausibility in growth estimates when small individuals are under-sampled, based on Bayesian fitting growth models using Markov Chain Monte Carlo (MCMC) with informative priors on growth parameters. Focusing on the blue jack mackerel, Trachurus picturatus, which is an important commercial fish in the southern northeast Atlantic, this Bayesian approach was evaluated in relation to standard growth model fitting methods, using both direct readings and back-calculation data. Matched growth parameter estimates were obtained with the von Bertalanffy growth function applied to back-calculated length at age and the Bayesian fitting, using MCMC to direct age readings, with both outperforming all other methods assessed. These results indicate that Bayesian inference may be a powerful addition in growth modelling using imperfect data and should be considered further in age and growth studies, provided relevant biological information can be gathered and included in the analyses.
- Negative impact on the reproductive potential of blue jack mackerel Trachurus picturatus by Kudoa infection of the ovaryPublication . Neves, Ana; Gordo, I.; Sequeira, Vera; Vieira, Ana Rita; Silva, E.; Silva, F.; Duarte, A.M.; Mendes, S.; Ganhão, R.; Peleteiro, M.C.; Assis, Carlos; Sampaio e Rebelo, Rui; Magalhães, Maria; Gil, M.M.; Gordo, Leonel S.Reproduction of Trachurus picturatus off the western Portuguese coast was studied over 1 yr. During histological analyses, the presence of Kudoa sp. was detected in advanced vitellogenic oocytes. Kudoa infections are known to cause economic loss through the induction of postmortem liquefaction of fish muscles, but ovarian infection as reported in this study will seriously affect the reproductive potential of the species and thus impact fisheries productivity. Only females showed gonad infection which led to total degradation of advanced vitellogenic oocytes. No macroscopic, somatic or condition indices revealed differences between infected and uninfected females, rendering this infection event a concealed suppression of reproduction.
- Seasonal study of the nutritional composition of unexploited and low commercial value fish species from the Portuguese coastPublication . Duarte, Ana M.; Silva, Frederica; Mendes, Susana; Pinto, Filipa R.; Barroso, Sónia; Silva, Elisabete; Neves, Ana; Sequeira, Vera; Magalhães, Maria; Sampaio e rebelo, Rui; Assis, Carlos; Vieira, Ana Rita; Gordo, Leonel Serrano; Gil, Maria ManuelTarget species diversification is essential for fisheries sustainability and fish market revitalization. Fish discards are a widely recognized problem resulting from fisheries worldwide, and are of major concern for all sector players, from administrations, to fishermen, and scientists. However, non-target species are seldom studied, and information on nutritional profiles and seasonal changes in nutritional properties is generally lacking. This study assessed the seasonal nutritional composition of two unexploited (Serranus cabrilla, Capros aper) and three low commercial value fish species (Trachurus picturatus, Spondyliosoma cantharus, and Trigla lyra), captured on the Portuguese coast over 1 year. Significant seasonal variations were observed in the nutritional composition of all the species studied. Moisture and ash contents varied from 70% to 81% and from 5% to 13%, respectively. The maximum fat contents were 5% for C. aper and 4% for T. picturatus, allowing to classify all studied fishes as lean. The highest protein contents were recorded for C. aper (25%) and S. cantharus (20%). The unexploited and low commercial value fish species studied were shown to be good fat and protein sources, comparable to commonly consumed species, such as cod and salmon, having a great potential to become commonly consumed fish in Portugal.