Browsing by Author "Sequeira, Vera"
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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.
- Age and growth of small red scorpionfish, Scorpaena notata (Actinopterygii: Scorpaeniformes: Scorpaenidae), a common discard species from the Portuguese fisheryPublication . Neves, Ana; Sequeira, Vera; Vieira, Ana Rita; Paiva, Rafaela Barros; Gordo, LeonelBackground. The small red scorpionfish, Scorpaena notata Rafinesque, 1810, appears as a bycatch of Portuguese fisheries. Bycatch species are likely to suffer the same declines as commercial species with which they co-occur but information on those species for Portuguese waters does not exist. In order to increase the knowledge for the Portuguese continental-shelf waters several aspects of the species growth were investigated. Materials and methods. Age and growth of Scorpaena notata from Portuguese continental-shelf waters were studied using 379 otoliths. A subsample of 70 otoliths, covering all length classes, was read by three of the authors to establish a reading and interpretation pattern. The von Bertalanffy growth model was fitted to sex-specific age–length data. The likelihood ratio tests were used to evaluate the significance of differences on growth parameters between sexes and with the parameters estimated in different areas. Results. Females dominated in smaller length classes while males prevailed in larger ones, although overall sex ratio did not deviate from 1 : 1. Females ranged from 10.5 to 18.8 cm total length (TL) and from 1 to 6 years; males ranged from 11.4 to 20.7 cm TL and from 1 to 7 years. The von Bertalanffy growth parameters estimated for the Portuguese shelf waters showed significant differences between sexes and were: L∞ = 18.23 cm TL, k = 0.43yr–1, t0 = –0.99 yr for females and L∞ = 21.17 cm TL, k = 0.28yr–1 and t0 = –1.73 yr for males. The age range found in the Portuguese shelf waters was similar to that found in the Balearic Islands but about half of that found for the Adriatic Sea. Significant differences between growth parameters from the Portuguese coast and those from the Balearic Islands and Adriatic Sea were found. Conclusion. Estimates of L∞ in the presently reported study were the highest but rather consistent with the maximum length given for the species.
- Age, growth and mortality of the comber Serranus cabrilla (Linnaeus, 1758) in the Eastern AtlanticPublication . Gordo, Leonel; Neves, Ana; Vieira, Ana Rita; Paiva, Rafaela Barros; Sequeira, VeraComber is an important bycatch species in the trawl fishery both in the Mediterranean and the Atlantic. Age and growth studies have been restricted to the eastern Mediterranean and no methodologies were ever applied to ensure accuracy and precision. In this study a total of 471 otoliths from specimens ranging from 12 to 26 cm were used. Precision indices showed a high level of agreement between readers and no evidence of systematic disagreement was obtained. To estimate fish growth and due to the absence of individuals smaller than 12 cm, three approaches were used to estimate the von Bertalanffy growth parameters: whole otolith readings, back calculation and a combination of both methodologies. Akaike’s information criterion suggests that the back calculation approach was the best one for describing comber growth: TL = 25.26 [1−e(−0.21(t+1.72)]. Natural mortality estimates varied between M = 0.44 year−1 and M = 0.48 year−1 while estimates of the fishing mortality varied between 0.12 year−1 and 0.16 year−1 and the exploitation rate between 0.20 and 0.27.
- Age, growth and reproduction of the protandrous hermaphrodite fish, Sarpa salpa, from the Portuguese continental coastPublication . Paiva, Rafaela Barros; Neves, Ana; Sequeira, Vera; Vieira, Ana Rita; Costa, Maria José; Gordo, LeonelSalema, Sarpa salpa is a commercial exploited species in the Atlantic Ocean with little available information for the essential population parameters, such as age, growth and reproduction. The present study aims to describe these parameters for S. salpa obtained off the coast of Portugal. Ages were estimated from the whole otolith readings; the minimum and the maximum ages observed were 0 and 14 years, respectively, corresponding to 5.2 and 41.4 cm of total length (TL). Whole otolith readings and back-calculation approaches were used to estimate the parameters of the von Bertalanffy growth function and the Akaike's information criterion value suggested that the second approach was the best one to describe the growth of salema: L ∞ = 45.07 cm, k = 0.14 year−1 and t 0 = −1.43 year. The species is a protandric hermaphrodite and the sex change process occurred between 28.6 and 40.9 cm TL. A short spawning season was identified, extending from September to November. The estimated length at first maturity for males was 24.5 cm TL, corresponding to an age of 2 years at first maturity. This species exhibited a determinate fecundity type and the relative annual fecundity varied between 462 and 2662 oocytes per gram of gutted weight.
- Bluemouth, Helicolenus dactylopterus (Delaroche, 1809) : biology and stock structure in portuguese watersPublication . Sequeira, Vera; Gordo, Leonel Serrano, 1957-The biology and ecology of many commercially important species are not subject to study before they began to be exploited. Besides, the knowledge of stock structure and degree of mixing among populations is vital for the rational management of marine resources. Bluemouth, Helicolenus dactylopterus, is a benthic deep-water species and the most commerciallly important Scorpaenidae landed in Portuguese waters although its exploitation is unregulated. Available biological information is scarce and contradictory and its stock structure is unknown. This thesis aims to gather new and important biological information on bluemouth and clarify the stock structure of this species in Portuguese waters (mainland Portugal, Azores and Madeira). Age and growth studies confirmed bluemouth as a slow-growing, long-lived, k-strategist species and consequently vulnerable to fishing exploitation. Reproductive studies revealed novel information on their reproductive strategy, namely that bluemouth release embryos in initial development stages enclosed in a gelatinous matrix produced by the ovary that stays within the gonad for a presumed period of 12-18 h. The fecundity type was also investigated suggesting that this species presents an indeterminate fecundity. The evolution of the maturity stages along the year, the bioenergetic indexes and the length-at-first maturity were analysed in order to characterize bluemouths’ sexual cycle in Portuguese waters. Stock structure was investigated following a holistic approach which involved an array of complementary techniques. Life history parameters, parasites, body geometric morphometrics and otolith shape were analysed and the results clearly suggest the existence of three stocks of bluemouth in Portuguese waters.
- Diet and feeding strategy of the forkbeard Phycis phycis (Pisces: Phycidae) from the Portuguese continental coastPublication . Silva, Ana Rita; Vieira, Ana Rita; Sequeira, Vera; Paiva, Rafaela Barros; Gordo, Leonel; Neves, AnaThe diet and feeding behaviour of the forkbeard Phycis phycis was studied based on 246 stomachs collected between May 2011 and April 2012 from a commercial fleet operating off the central west coast of Portugal. A total of 44 prey items were identified in the stomachs which were merged into major groups to avoid problems with low expected frequencies. The following taxonomic categories were considered: non-decapod Crustacea, Caridea, Anomura, Munida spp., Processa spp., Brachyura, Pisces, Trisopterus luscus . In order to investigate possible diet differences between fish size classes, a cluster analysis was performed using the mean abundance of each prey group by forkbeard 5 cm length class, and three length groups (LG) were obtained: <22.5, 27.5 – 37.5 and >42.5 cm. Seasonally, Caridea was the main prey group during winter and autumn while Pisces was predominant during the rest of the year. Caridea was the most important prey group for LG1 and LG2 while in LG3 Pisces was the principal one. The forkbeard feeding behaviour may be characterized as presenting a shift pattern from a more generalist diet (small Crustacea, mainly Caridea) in the young adults to a more specialist strategy (teleosts) in the adults.
- Diversity of sexual strategies of fish species caught by bottom trawl off the western Iberian PeninsulaPublication . Sequeira, Vera; Neves, Ana; Paiva, Rafaela Barros; Vieira, Ana Rita; Canário, Adelino; Gordo, LeonelSamples of boarfish Capros aper, small red scorpionfish Scorpaena notata and comber Serranus cabrilla were collected from monthly by-catch samples on board commercial trawlers off the western coast of Portugal. A histological approach was undertaken to study each species’ reproductive strategy and annual sexual cycle. Temporal variations of the gonadosomatic index and of two condition indices (hepatosomatic and Fulton's K) were also analysed. Results showed that C. aper and S. notata are gonochoristic whilst S. cabrilla is a simultaneous hermaphrodite. Fertilization is external and development of secondary growth follicles is asynchronous in the three species. Mass atresia characterized the end of the spawning season in S. notata and S. cabrilla. In C. aper a high prevalence of atresia was observed throughout the year and was not attributed to regressing or regenerating phases or skip spawning events. The main spawning season of the three species was in the summer and it is suggested that spawning is related to upwelling. During the summer, the spawning interval was 1.09, 1.23 and 1.84 days for S. cabrilla, S. notata and C.aper, respectively. The results of this study indicate potential plasticity and environmental adaptation of sexual strategies.
- 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.
- Estimating fecundity in the zygoparous species Helicolenus dactylopterus (Actinopterygii, Scorpaeniformes): adaptation of the gravimetric methodPublication . Sequeira, Vera; Neves, Ana; Vieira, Ana Rita; Paiva, Rafaela Barros; Canário, Adelino; Gordo, LeonelBluemouth, Helicolenus dactylopterus is zygoparous species with internal fertilization spawning multiple batches of early-celled embryos in gelatinous masses. Its unusual reproductive strategy required methodological adjustments to estimate potential annual fecundity. The present study applied an adaptation of the gravimetric method, estimated batch fecundity based on different spawning fraction criteria (gestation, early-celled, and blastula females), and compared these estimates with the number of developing oocytes (NDOR) in the beginning of spawning to clarify the oocyte development pattern. Spawning fraction estimation based on the gestation criterion was considered the most reliable given its low variance and the subjectivity of staging early-celled embryos. On average, 87 batches were spawned with a mean spawning interval estimated at 1.73 days, and a mean relative annual total fecundity of 1,773 embryos g−1 carcass. The inexistence of a clear decreasing trend in the NDOR throughout the spawning season, and the lower NDOR estimates in females in the beginning of spawning comparing with relative annual fecundity (gestation criterion) suggests vitellogenic oocyte recruitment supporting previous results of indeterminate fecundity in Portuguese coast. The method proposed can be considered in fecundity studies of other commercial important species which extrudes gelatinous egg masses.
- Genetic and Morphological Variation of the Forkbeard, Phycis phycis (Pisces, Phycidae): Evidence of Panmixia and Recent Population Expansion along Its Distribution AreaPublication . Vieira, Ana Rita; Rodrigues, Ana Sofia B.; Sequeira, Vera; Neves, Ana; Paiva, Rafaela Barros; Paulo, Octávio S.; Gordo, LeonelThe knowledge of population structure of a species is essential to effectively assess and manage fisheries. In the present study, genetics, by mitochondrial DNA cytochrome b sequence analysis, and body geometric morphometrics were used to evaluate the existence of distinct populations of the forkbeard (Phycis phycis), an important commercial species in several European countries, especially Portugal and Spain. For geometric morphometric analysis, specimens were collected in the Northeast Atlantic Ocean-Azores, Madeira and mainland Portugal, and for genetic analysis, these samples were complemented with samples collected in the Mediterranean Sea-Spain, Italy and Croatia, in order to cover the entire distribution area of the species. Body shape of the forkbeard from the Northeast Atlantic was found to be highly variable. This variation was probably associated with different environmental factors between the study areas. Despite morphological variation, a low genetic differentiation between samples from different areas was found, most likely due to gene flow that occurred in the past or with the demographic history of the species. Moreover, the presence of unique haplotypes in the Northeast Atlantic and in the Mediterranean suggests that recent gene flow between populations from these areas should be limited. Altogether, a high haplotype diversity, a low nucleotide diversity, a "star-like" network and the results of the mismatch distribution, indicate a possible signature of recent population expansions, which probably started during the end of the Last Glacial Maximum and led to the colonization of the Northeast Atlantic and the Mediterranean.
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