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Reserve effect of a small North-East Atlantic marine protected area (Arrabida, Portugal) on soft-sediment fish species

Publication . Martínez Ramírez, Lucas; Priester, Carl Robert; Sousa, Inês; Erzini, Karim; Abecasis, David

The implementation of marine protected areas (MPAs) has been widely used as a tool to manage and conserve marine resources and services. Yet, to date, the reserve effect is still weakly evaluated, particularly for soft-sediment habitats. The Arrabida MPA, considered as a biodiversity hotspot, was fully established in 2009 on the west coast of Portugal and is characterized by large expanses of soft-sediment habitats. This MPA was established to protect biodiversity and to ensure the livelihood of the local small-scale fisheries community. Beyond before-after-control-impact (BACI) analyses were carried out on catch data (abundance and biomass) of 351 trammel net sets from experimental fishing campaigns (2007-2019) to study the reserve effect on demersal fish populations. The results show a declining trend in abundance inside and outside the protected area, with significant positive effects only found for undersize commercial species and Solea senegalensis, and a general increase in fish species total length. Despite the lack of any obvious reserve effect, the increase in fish length can be considered as a first sign. Anthropogenic pressures are generalized around the area, and transgressions of the restrictions are frequently observed inside the no-take zone. These can, among other aspects, delay or prevent the expected reserve effects. Therefore, enforcement and/or modification of the spatial plan must be incentivized to achieve the goals of the MPA.

2021-07Journal article

Restricted

Residency and space use estimation methods based on passive acoustic telemetry data

Publication . Kraft, Sebastian; Gandra, Miguel; Lennox, R. J.; Mourier, J.; Winkler, Alexander; Abecasis, David

Acoustic telemetry has helped overcome many of the challenges faced when studying the movement ecology of aquatic species, allowing to obtain unprecedented amounts of data. This has made it into one of the most widely used methods nowadays. Many ways to analyse acoustic telemetry data have been made available and deciding on how to analyse the data requires considering the type of research objectives, relevant properties of the data (e.g., resolution, study design, equipment), habits of the study species, researcher experience, among others. To ease this decision process, here we showcase (1) some of the methods used to estimate pseudo-positions and positions from raw acoustic telemetry data, (2) methods to estimate residency and (3) methods to estimate two-dimensional home and occurrence range using geometric or hull-based methods and density-distribution methods, a network-based approach, and three-dimensional methods. We provide examples of some of these were tested using a sample of real data. With this we intend to provide the necessary background for the selection of the method(s) that better fit specific research objectives when using acoustic telemetry.

2023-03-01Journal article

Open Access

Potential biodiversity connectivity in the network of marine protected areas in Western Africa

Publication . Assis, Jorge; Failler, Pierre; Fragkopoulou, Eliza; Abecasis, David; Touron-Gardic, Gregoire; Regalla, Aissa; Sidina, Ebaye; Dinis, Herculano; Serrao, Ester

Marine Protected Areas (MPAs) must function as networks with sufficient stepping-stone continuity between suitable habitats to ensure the conservation of naturally connected regional pools of biodiversity in the long-term. For most marine biodiversity, population connectivity is mediated by passively dispersed planktonic stages with contrasting dispersal periods, ranging from a few hours to hundreds of days. These processes exert a major influence on whether threatened populations should be conserved as either isolated units or linked metapopulations. However, the distance scales at which individual MPAs are connected are insufficiently understood. Here, we use a biophysical model integrating high-resolution ocean currents and contrasting dispersal periods to predict connectivity across the Network of MPAs in Western Africa. Our results revealed that connectivity differs sharply among distinct ecological groups, from highly connected (e.g., fish and crustacea) to predominantly isolated ecosystem structuring species (e.g., corals, macroalgae and seagrass) that might potentially undermine conservation efforts because they are the feeding or nursery habitats required by many other species. Regardless of their dispersal duration, all ecological groups showed a common connectivity gap in the Bijagós region of Guinea-Bissau, highlighting the important role of MPAs there and the need to further support and increase MPA coverage to ensure connectivity along the whole network. Our findings provide key insights for the future management of the Network of MPAs in Western Africa, highlighting the need to protect and ensure continuity of isolated ecosystem structuring species and identifying key regions that function as stepping-stone connectivity corridors.

2021-11-27Journal article

Open Access

Small coastal marine protected areas offer recurring, seasonal protection to the common stingray (Dasyatis pastinaca)

Publication . Kraft, Sebastian; Winkler, Alexander; Abecasis, David

Marine protected areas (MPAs) are a crucial tool in safeguarding marine biodiversity. However, elasmobranchs are often not the primary protection target of MPAs, and their contribution to protect these species remains to be better understood. In this study we examine the movement patterns of common stingrays in the Professor Luiz Saldanha marine park, a Portuguese temperate coastal MPA. Using acoustic telemetry, we tagged 31 common stingrays and analyzed their spatial and temporal distribution within the MPA and adjacent areas using a long-term data set. Our findings indicate that this species exhibits seasonal site fidelity, with greater presence during the colder months and reduced presence during warmer months. Space use areas did not exceed the size of the fully protected area, and nocturnal and crepuscular activity was significantly higher than during daytime. Additionally, we observed that most individuals seasonally migrated between this MPA and the nearby Sado estuary, likely to reproduce in the latter. These results demonstrate the site fidelity of common stingrays to an area within the marine park, however the protection provided is only seasonal. Seasonal protection of the movement corridor between the marine park and the estuary would improve the management of this species.

2023-12Journal article

Open Access

Depth and temperature preferences of meagre, argyrosomus regius, as revealed by satellite telemetry

Publication . Winkler, Alexander; Astrid Bovim, Lily; Macena, Bruno C. L.; Gandra, Miguel; Erzini, Karim; Afonso, Pedro; Abecasis, David

Argyrosomus regius (commonly referred to as meagre), is one of Europe's largest coastal bony fish species and supports important recreational and commercial fisheries in the Atlantic and Mediterranean coasts. Demand for this species, and more recently for their swim bladders, has led to regional population declines and growing importance as an aquaculture species. Despite intense research in captivity, little is known about the spatial ecology of A. regius's wild population, including basic information such as vertical migrations and depth/temperature preferences. Previous research based on indirect data suggests a seasonal habitat shift from shallow to deeper waters, but this has never been validated through direct high-resolution movement data. In this study, we tagged 13 adult A. regius with pop-up satellite archival tags in the South of Portugal, which successfully returned data from 11 individuals including high-resolution data from six recovered tags (mean, range: 167 days, 28-301 days). We found that adults of this population spend 95.2% of their time between 5 and 75 m depth (mean +/- SD, 30.9m +/- 18.3m) and do not venture beyond 125 m. Across seasons, A. regius move across water temperatures between 13.3 and 24.8 degrees C with a preferred thermal range between 14 and 18 degrees C where they spent 75.4% of their time. The inferential modelling using this electronic data validated previous hypotheses by showing significant differences between a shallower and warmer summer habitat vs. a deeper and cooler winter habitat. Visual investigation of the diel effects on depth preferences suggests subtle changes in depth use between day and night during the warmer months of the year. We speculate that these patterns are in response to the species' behavioural ecology and physiology, reflecting the seasonal changes in water stratification and presence of prey, as well as on the species reproduction, which results in summer spawning aggregations in shallower areas.

2023Journal article

Open Access