Browsing by Author "Maia, Catarina"
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- Designing a coastal monitoring marine biodiversity survey, using trammel nets and gillnets in PortugalPublication . Rufino, Marta M.; Maia, Catarina; Dinis, David; Farias, Inês; Moura, Teresa; Gomes, Pedro; Quaresma, Ivania; Martins, Rogélia; Figueiredo, Ivone; Serra-Pereira, Bárbara; Gaspar, Miguel; Moreno, AnaAlthough coastal areas are of great importance, they often lack long term monitoring surveys, which are essential for effective management, fisheries sustainability, and marine spatial planning. To address this, we conducted two experimental surveys aimed at assessing communities and their biodiversity, with the objective of designing a monitoring program for marine coastal biodiversity, based on gear type, depth, sampling arrangement, total net length, and panel position within the haul. Depth was found to be the most important factor shaping biodiversity, while gear type had the greatest impact on assessing species richness. Overall, both number of species and diversity increased with depth, though significant differences were only found between hauls deployed at 10 m and deeper (30-50 m). Trammel nets caught a larger number of species compared to gillnets, and there was evidence of an interaction between depth and gear, in terms of abundance and at the community level; samples taken deeper than 10 m showed more gear-related differences. We found that neither the panel position within the haul nor the number of nets had any impact on species diversity or abundance. Similarly, there was no evidence for an effect related to the arrangement of nets, as results were consistent whether using separated or continuous net panels. However, the number of nets used as a sampling unit significantly influenced the results, as the variation in species abundance and diversity with depth and gear type was similar, when 20 or 30 nets were used, but became more variable when only 10 nets were used, even with increased replication. We concluded that both trammel nets and gillnets should be included in a coastal biodiversity monitoring program, as each catches a different set of species, including both demersal and pelagic taxa. Further, we recommend using a minimum of 20 nets (ideally 30+) per station, with replication. The evaluated monitoring system has a minimal impact on the ecosystem, can be easily deployed using commercial vessels and effectively captures a large number of species, being thus, highly recommended to be used in coastal monitoring surveys.
- How is the morphology of the oviducal gland and of the resulting egg capsule associated with the egg laying habitats of Rajidae species?Publication . Maia, Catarina; Serra-Pereira, Bárbara; Erzini, Karim; Figueiredo, IvoneEgg capsules of Rajidae species vary in size, shape and adornments. These differences can be used as a taxonomic tool to differentiate species. Furthermore, since egg capsule external morphology is adapted to the environment where they are laid, it can be used make inferences on egg-laying grounds. In the present study, oviducal glands and egg capsules of seven species of skates (Leucoraja naevus, Raja brachyura, Raja montagui, Raja microocellata, Raja miraletus, Raja clavata and Raja undulata) are described and compared, and a taxonomic key developed. The resulting taxonomic key constitute a useful tool to identify skate species inhabiting Portuguese continental waters and, therefore, to improve our knowledge of egg laying habitatsproviding useful information for conservation and management.
- Identification of potential essential fish habitats for skates based on fishers' knowledgePublication . Serra-Pereira, Bárbara; Erzini, Karim; Maia, Catarina; Figueiredo, IvoneUnderstanding of spatio-temporal patterns of sensitive fish species such as skates (Rajidae) is essential for implementation of conservation measures. With insufficient survey data available for these species in Portuguese Continental waters, this study shows that fishery-dependent data associated with fishers' knowledge can be used to identify potential Essential Fish Habitats (EFH) for seven skate species. Sites with similar geomorphology were associated with the occurrence of juveniles and/or adults of the same group of species. For example, sites deeper than 100 m with soft sediment include predominantly adults of Raja clavata, and are the habitat for egg deposition of this species. Raja undulata and R. microocellata are the more coastal species, preferring sand or gravel habitats, while coastal areas with rocks and sand seabed are potential nursery areas for R. brachyura, R. montagui and R. clavata. The main output of this study is the identification of preferential fishing sites enclosing potential EFH for some species, associated with egg-laying and nursery grounds. The location of these areas will be considered for future seasonal closures, and studies will be conducted to evaluate the biological and socio-economic impacts of such measures. As in the past, fishermen will collaborate in the process of evaluating those impacts, since they have practical and applied knowledge that is extremely valuable for evaluating the advantages and disadvantages of such closures. In conclusion, this study is a first contribution to the understanding and identification of EFH for skate species, associated with nursery and egg deposition sites, with direct application to management.
- Reproductive biology of the species Leucoraja naevus from Portuguese continental watersPublication . Maia, Catarina; Erzini, Karim; Figueiredo, IvoneSkate populations tend to be highly vulnerable to exploitation as a result of the main life history characteristics (slow growth, late maturity and low fecundity). The cuckoo ray, Leucoraja naevus, one of the skate species landed in Portugal, is mainly a by-catch species from the artisanal mixed-fishery, and for this reason it is very difficult to acquire information about its basic biology. The two main goals of the present work were to estimate the length at first maturity, fecundity and reproductive cycle of the species Leucoraja naevus and to compare the microscopic structure and chemical nature of the secretions produced by the oviducal gland of the species Leucoraja naevus with other skate species taking into account their reproductive strategy. Although the species has been studied in other NE Atlantic geographic areas, namely Celtic Sea, Irish Sea and North Sea, this study is the first to provide information on the reproductive biology of Leucoraja naevus in Southern European waters. Length at first maturity was estimated at 57 cm and 55 cm TL for males and females, respectively. Active females were observed in every months of the year suggesting that reproduction may occur year round, with a reproductive peak during winter months between January and April. Females release follicles in batches of 5. However, it was not possible to determine the number of reproductive episodes realized by a female during a 1-year period. Leucoraja naevus, Raja brachyura, Raja miraletus, Raja undulata, Raja microocellata and Raja montagui, have similar microscopic structure divided in four zones: club, papillary, baffle and terminal. However, differences were found between Leucoraja naevus and the remaining species in the chemical nature of the secretions produced in the papillary zone, that seems to have a higher content of sulphated acid mucins, and in the terminal zone that, like in Raja microocellata, lacks serous gland tubules. The differences found are related with the reproductive strategy displayed by each species, namely with the capsule and spawning habitats characteristics. Sperm was found in all species as laterally aligned bundles in the deep recessed tubules of the baffle zone, adjacent to the muscle layer, suggesting short-term sperm storage. These results provide essential information on the reproductive biology not only about the species Leucoraja naevus but also about other by-catch species inhabiting Portuguese continental waters and, therefore, constitute an important tool for a proper management plan.