Vera Sequeira

Vera Sequeira
MARE – Marine and Environmental Sciences Centre · Fisheries Biology Laboratory

Ph D

About

55
Publications
10,372
Reads
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531
Citations

Publications

Publications (55)
Article
The most consumed fish species in Portugal do not correspond to the most caught fish species on the Portuguese coast. From the point of view of ocean sustainability and economics, it is important to study unexploited or underexploited fish species that have the potential to be introduced into the food market. This potential can be reflected by thei...
Article
Full-text available
Target species diversification is essential for fisheries sustainability and fish market revitalization. Fish discards are a widely recognized problem resulting from fisher-ies worldwide, and are of major concern for all sector players, from administrations, to fishermen, and scientists. However, non-target species are seldom studied, and informati...
Article
Full-text available
Growth 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 w...
Article
The depletion and overexploitation of several fish stock demands for a valorisation of non-target and discarded species. However, such species are often poorly studied, and information on their biological parameters must be gathered for effective population management. For one year the reproductive strategy of the piper gurnard Trigla lyra, and the...
Article
The boarfish Capros aper is one of the most commonly discarded non-commercial species in the International Council for the Exploration of the Sea (ICES) Subdivision VIII in the Atlantic. An increasing interest in this fishery and an incomplete knowledge on the status of the stock justified the present investigation focused on the determination of f...
Article
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We 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 picturatu...
Article
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Overfishing is increasing over time, and according to FAO (Food and Agriculture Organization), about one third of the world’s fish stocks are now overfished. Thus, diversifying the target species is essential for fisheries sustainability contributing to improve resource-efficient processes. Non-target species can be valuable resources for the devel...
Article
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 post-mortem liquefaction of fish muscles, but ovarian infection as reported in...
Article
The complexity and spatio‐temporal scale of populations’ dynamics influence how populations respond to large‐scale ecological pressures. Detecting and attributing synchrony (i.e. temporally coincident fluctuations in populations’ parameters) is key as synchronous populations can become more vulnerable to stochastic events that can affect the viabil...
Article
Full-text available
Resolution of population structure represents an effective way to define biological stocks and inform efficient fisheries management. In the present study, the phylogeography of the protogynous sparid Spondyliosoma cantharus, in the East Atlantic and Mediterranean Sea, was investigated with nuclear (S7) and mitochondrial (cytochrome b) DNA markers....
Article
Knowledge on population units is critical for understanding population dynamics and providing an adequate fisheries management. Despite its vast distribution and commercial importance, there is no information on black seabream population structure. Different approaches to otolith analysis were used to elucidate on the stock structure of this specie...
Article
Full-text available
The 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 frequenci...
Article
Information on fish reproductive strategy is essential to understand population dynamics. Samples of black seabream, Spondyliosoma cantharus, were collected from the western Portuguese continental coast to investigate the reproductive cycle, the timing of spawning, length at maturity and sex change, fecundity type and fecundity. This species is a p...
Article
Knowledge of population spatial structure is essential in fisheries management. The study of morphological variation patterns in fishes can indicate differences in growth and maturation rates, and thus provide information on group dynamics that should be modelled and managed separately. Identification of intraspecific groups which have different li...
Article
The population structure of the blue jack mackerel (Trachurus picturatus, Osteichthyes, Carangi-dae), in the northeast Atlantic is still unknown. To identify any distinct population units, three areas were selected: waters off Madeira, Peniche (mainland Portugal), and the Canary Islands. Knowledge of population structure is an aspect of the populat...
Article
The 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 frequenci...
Article
Full-text available
Age determination of fish species is a key process for fisheries management and the accuracy of assessments is highly dependent on age estimates. To model complex life histories such as protogynous hermaphroditism, the growth curve to fit the age-length data should be carefully chosen. For the first time, the first annual growth increment of Spondy...
Article
Two hundred and seven individuals (103 females and 104 males) of bluemouth Helicolenus dactylopterus (Scorpaeniformes, Sebastidae), a commercially important deep-water species with an unusual reproductive strategy, from the eastern Atlantic Ocean ranging from 13·9 to 37·5 cm total length (LT) were analysed from September 2011 to October 2012. The a...
Article
Knowing fish reproductive strategy is essential for understanding population dynamics. This study intends to define the spawning season, length at first maturity, fecundity type, and estimate fecundity of forkbeard, Phycis phycis, from the Portuguese coast. Monthly samples collected from commercial landings between May 2011 and December 2012 were u...
Article
Full-text available
The 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 specie...
Article
Full-text available
Salema, 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 min...
Article
Full-text available
Comber 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 i...
Article
Bluemouth, 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 batc...
Article
Full-text available
Background. 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 co...
Article
Samples 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 gon...
Article
Full-text available
The stock structure of forkbeard, Phycis phycis, in the Northeast Atlantic is still unknown. The knowledge of the stock structure of a species is essential to effectively assess the stock and manage fisheries. Otolith shape analysis has been successfully applied in stock identification using the elliptic Fourier analysis. This method was used to ev...
Article
Les ovaires de la saupe, Sarpa salpa (Linnaeus, 1758), présentent des structures dures et facilement visibles macroscopiquement. Leur analyse histologique montre que ce sont des masses d’ovocytes hydratés résultant d’un événement de ponte, incomplète ou non. Le modèle linéaire généralisé (MLG) montre que la présence de kystes a été significativemen...
Article
Full-text available
The forkbeard, Phycis phycis, is an important commercial species in Portugal; however, little information is available on its biology. Age and growth of the forkbeard from Portuguese continental waters were studied using 687 otoliths from specimens caught between May 2011 and December 2012. Otoliths were transversally sectioned, and assigned ages w...
Article
The knowledge of the reproductive strategy is essential for the comprehensive understanding of the population dynamics of any fish species. This study intends to define the spawning season, verify the type of fecundity regulation and estimate relative annual fecundity for Serranus atricauda inhabiting the south-west of Portugal seamounts (Gorringe,...
Poster
Full-text available
The presence of atretic hydrated oocytes has been reported sporadically in fishes being related with changes in the habitat characteristics (e.g. pollution) or in the stock structure (e.g. sex ratio). But in salema these structures appeared frequently and associated to the regenerating stage, and in all months (except October), suggesting to be cha...
Article
Several studies on bluemouth age and growth have been published over the last two decades, but they show inconsistent differences in maximum age estimates, suggesting interpretation differences in reading whole or sectioned otoliths. In order to clarify this issue, the present study was carried out to assess bias and precision of age reading betwee...
Poster
Full-text available
Os peixes regulam a produção de ovos através de um processo denominado por atrésia. Esta é semelhante em todas as espécies de peixes e pode ocorrer em fêmeas em diferentes estados de desenvolvimento sexual, mas a atrésia de oócitos hidratados ovulados (livres das membranas foliculares, granulosa e teca) é tido como um evento raro e pouco documentad...
Article
Full-text available
Age and growth of Pontinus kuhlii were studied using otoliths of 153 males and 148 females, with males having a greater length (and age) than females. A high level of agreement was achieved among readers. Due to gear selectivity, only ages above 7 years (males) and 8 years (females) were estimated in whole otoliths. To estimate length-at-age in you...
Article
Full-text available
Purpose – There are very few studies that characterize the properties of the edible part from deep-water fish species which constitute a new target for developing fisheries. Therefore this paper aimed to examine the balance between health benefits and risks associated to the birdbeak dogfish consumption, with a special emphasis on the assessment of...
Article
Full-text available
In order to investigate the feeding habits of Helicolenus dactylopterus dactylopterus along the conti-nental Portuguese coast, a total of 619 individuals were sampled of which 60% contained food in their stomach and 35% had more than one prey item. Among the 81 prey items that were identified in the stomachs, benthic and benthopelagic prey prevail...
Article
Full-text available
Bluemouth, Helicolenus dactylopterus, is a zygoparous species with internal fertilization that stores the spermatozoa in crypts within the female ovaries and then releases embryos in initial development stages enclosed in a gelatinous matrix. It is a batch spawner species but the type of fecundity is unclear. This issue is investigated based on fou...
Article
Full-text available
Little information is available on the maternal–embryonic relationships among sharks. Birdbeak dogfish Deania calcea) has been described as ovoviviparous, but this term comprises a wide range of forms on how the embryos are nourished including lecithotrophy and matrotrophy. To evaluate the maternal–embryonic relationship in birdbeak dogfish we have...
Article
The age, growth and reproductive biology of bluemouth, Helicolenus dactylopterus were studied in order to assess the use of these life history parameters as possible population discriminators in Portuguese waters. Fish were obtained from commercial landings in mainland Portugal (Peniche), Azores, and Madeira and supplementary samples were obtained...
Article
Full-text available
The understanding of the stock structure of a species is essential to effectively manage fisheries. Otolith shape analysis has been successfully applied in stock identification using the elliptic Fourier analysis. This method was used to assess possible differences in the otolith shape of Helicolenus dactylopterus caught around the Azores, Madeira...
Article
Full-text available
In this study, landmark-based geometric morphometric methods were applied to evaluate the possible existence of different bluemouth, Helicolenus dactylopterus (Delaroche, 1809), populations in the NE Atlantic. Fish were obtained from commercial landings in Azores, Madeira, and Peniche (mainland Portugal). Samples from a research survey along the Ga...
Article
Full-text available
The bluemouth, Helicolenus dactylopterus dactylopterus (Pisces: Sebastidae), is a zygoparous species with internal fertilization that stores the spermatozoa in crypts within the female ovaries. It spawns gelatinous egg masses that were investigated in this study. Histological analysis confirmed that the ovarian wall and peduncular epithelia play an...
Article
Full-text available
Little information is available on the reproductive parameters of the commercially exploited deep shark Deania calcea (Lowe, 1839). Samples were obtained from deep-water longlines operating at depths round 1450 m in the Portuguese continental slope between September 2008 and July 2009. Both the male and female reproductive tracts were morphological...
Article
Full-text available
In this study, landmark-based geometric morphometric methods were applied to evaluate the possible existence of different bluemouth, Helicolenus dactylopterus (Delaroche, 1809), populations in the NE Atlantic. Fish were obtained from commercial landings in Azores, Madeira, and Peniche (mainland Portugal). Samples from a research survey along the Ga...
Article
In the present study, the macroparasite assemblage infecting Helicolenus dactylopterus (Delaroche, 1809) in three different areas off the Portuguese coast was evaluated in order to assess their use as biological tags in stock identification. Fish were obtained from commercial landings in Azores, Madeira and mainland Portugal (Peniche), and were exa...
Article
Full-text available
Gonads of the NE Atlantic black scabbardfish were examined to give an insight into the reproductive biology of this species. It was concluded that black scabbardfish had determinate fecundity because: (i) a distinct hiatus in oocyte size was observed between pre-vitellogenic and vitellogenic oocytes; (ii) vitellogenic oocytes increased in size duri...
Article
Full-text available
Though whole otoliths are commonly adopted in age assignment of black scabbardfish, this study showed that sectioned otoliths are more appropriate because growth increments are more evident and ageing of larger specimens is easier. Vertebrae are not the most appropriate structure for ageing but, in the absence of otoliths, this structure may be use...
Article
The importance of cephalopods in marine ecosystems is well recognized as they serve as important predators and prey in many food chains. During a 1-year period, cuttlefish were monthly sampled in five areas throughout the Sado estuary, and the stomachs of 445 individuals were examined. Significant changes in the diet according to their life stage w...
Article
The cuttlefish (Sepia officinalis) is the most important traditional fishing activity in the Sado estuary. In order to analyse the spatial and temporal distribution patterns and to study the reproductive cycle of this species, twenty sampling areas were towed along the estuary on a monthly basis from May 2001 to April 2002. The higher densities wer...
Article
Full-text available
In all, 933 bluemouth (Helicolenus dactylopterus) were obtained from bottom-trawl research surveys along the Portuguese continental slope between October 2005 and February 2007 and from commercial landings. Age was determined by reading whole sagittal otoliths, and age estimates were validated by daily growth increment (DGI) analysis. Fish ranged f...
Article
From May 2001 to April 2002 the ichthyofauna from Tagus and Sado estuary was monthly sampled. 25 species from 18 families were identified in Tagus samples, and 38 species from 21 families in Sado estuary. Only 14 species (26%) occurred in the two estuaries, but 14 families (58%) were common for both. Pomatoschistus minutus, Gobius niger, Syngnathus...
Article
The reproductive patterns of Helicolenus dactylopterus are presented; the species is zygoparous. The first photographic record of three embryonic stages in the intraovarian gelatinous matrix is also presented.

Projects

Project (1)
Project
Bring science to schools and promote marine literacy.