Browsing by Author "Afonso, P."
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- Can small MPAs protect local populations of a coastal flatfish, Solea senegalensis?Publication . Abecasis, D.; Afonso, P.; Erzini, KarimThe benefits of protection of a small (4.3 km(2)) marine protected area (MPA) for Senegalese sole, Solea senegalensis, were investigated through experimental fishing trials and long-term (up to 293days) passive acoustic telemetry. A total of 106 trammel net sets were carried out between 2007 and 2011. Significant differences in abundance and biomass of sole between bottom types/depths (sandy bottoms between 12 and 20m deep vs muddy bottoms between 35 and 45m deep) were found, but no significant differences were attributable to the implementation of the no-take area. Passive acoustic telemetry revealed that most Senegalese sole spent a large part of their time between first and last detections (average residency index=69%) inside a relatively small area (average 95%=1.2km(2)), during which they preferred sandy bottoms, the most common habitat inside the MPA. Results also demonstrated that Senegalese sole do regular excursions beyond reserve boundaries, eventually emigrating from the MPA. The results suggest that small coastal MPAs providing adequate habitat may protect individuals of this species while allowing for moderate levels of adult spillover to neighbouring areas.
- Changes in movements of white seabream (Diplodus sargus) during the reproductive seasonPublication . Abecasis, D.; Afonso, P.; Erzini, KarimIt has been hypothesized, based on anecdotal information and reports, that adult white seabream migrate and aggregate during spawning. Because most of the past telemetric studies on this ecologically and commercially important species were short in duration and did not cover the reproductive season, we set out to use longer-term passive acoustic telemetry to test this hypothesis. We found that white seabream expands its home range and increases the frequency of forays during the reproductive season, but found no obvious signs of spawning aggregations. Our results thus provide evidence for short-range behavioral shifts in fish space use related to reproductive activity, and support the notion that small MPAs may be effective in managing reef fish populations by effectively protecting their spawning biomass. (c) 2015 Elsevier Ltd. All rights reserved.
- Combining multispecies home range and distribution models aids assessment of MPA effectivenessPublication . Abecasis, D.; Afonso, P.; Erzini, KarimMarine protected areas (MPAs) are today's most important tools for the spatial management and conservation of marine species. Yet, the true protection that they provide to individual fish is unknown, leading to uncertainty associated with MPA effectiveness. In this study, conducted in a recently established coastal MPA in Portugal, we combined the results of individual home range estimation and population distribution models for 3 species of commercial importance and contrasting life histories to infer (1) the size of suitable areas where they would be fully protected and (2) the vulnerability to fishing mortality of each species. Results show that the relationship between MPA size and effective protection is strongly modulated by both the species' home range and the distribution of suitable habitat inside and outside the MPA. This approach provides a better insight into the true potential of MPAs in effectively protecting marine species, since it can reveal the size and location of the areas where protection is most effective and a clear, quantitative estimation of the vulnerability to fishing throughout an entire MPA.
- Contrasting movements and residency of two serranids in a small Macaronesian MPAPublication . Afonso, P.; Abecasis, D.; Santos, Ricardo Serrão; Fontes, JorgeProtection inside marine reserves and the desired ‘reserve effect’ depend directly on the home rangeand sedentary behaviour of fishes throughout their lives. Benthic territorial predators are typically seenas major candidates to beneficiaries, but empirical evidence of short-versus long term residency is stillsurprisingly rare. We studied the inter-annual patterns of site fidelity and finer scale movements in twoof the most abundant benthic predators of the NE Atlantic coastal reefs, the dusky grouper (Epinephelusmarginatus) and the blacktail comber (Serranus atricauda), using passive acoustic telemetry inside andaround a small marine reserve in the Azores islands, central North Atlantic. Individuals of both speciesresided in the reserve year-round, occupying stable core activity areas within relatively small homeranges. Groupers were detected nearly every day (n = 11, median = 5.0 years) while combers were stilldetected in 2/3 of the days (n = 9, median = 2.0 years). Some dusky groupers underwent daily short-rangeforays during the summer, most probably related to spawning events, whereas combers appeared toforay for longer periods with no direct relation with reproductive activity. The two species also contrastin their diel pattern, strictly diurnal in the comber but crepuscular in the grouper. This study evidencesthat even small reserves within the size range of most coastal reserves can accommodate the multiple-scale patterns of space use of exploited benthic territorial species, and promote the recovery of theirlocal exploited populations in the long-term via the ‘reserve effect’ and, potentially, via the ‘larval export’effect.
- Early reserve effects linked to small home ranges of a commercial fish, Diplodus sargus, SparidaePublication . Abecasis, D.; Costa, B. H. E.; Afonso, P.; Gonçalves, E. J.; Erzini, KarimStudies that combine both the ecological responses of marine species and protection measures with movement patterns and habitat use are of major importance in order to better understand the performance of marine protected areas (MPA) and how species respond to their implementation. However, few studies have assessed MPA performance by relating local individual movement patterns and the observed reserve effects. In this study, we combined acoustic telemetry with abundance estimates to study the early effects of a recently established small coastal MPA on the local populations of white seabream. The results show that even small, recently established coastal MPAs can increase the abundance and biomass of commercial fish species, provided that target species have small home ranges and exhibit high site fidelity.
- Multidisciplinary estimates of connectivity and population structure suggest the use of multiple units for the conservation and management of meagre, Argyrosomus regiusPublication . Abecasis, David; Ogden, R.; Winkler, Alexander; Gandra, Miguel; Khallahi, B.; Diallo, M.; Cabrera-Castro, R.; Weiller, Y.; Erzini, Karim; Afonso, P.; Assis, JorgeInformation on population structure and connectivity of targeted species is key for proper implementation of spatial conservation measures. We used a combination of genomics, biophysical modelling, and biotelemetry to infer the population structure and connectivity of Atlantic meagre, an important fisheries resource throughout its distribution. Genetic samples from previously identified Atlantic spawning locations (Gironde, Tejo, Guadalquivir, Banc d'Arguin) and two additional regions (Algarve and Senegal) were analysed using genome-wide SNP-genotyping and mitochondrial DNA analyses. Biophysical models were conducted to investigate larval dispersal and connectivity from the known Atlantic spawning locations. Additionally, thirteen fish were double-tagged with biotelemetry transmitters off the Algarve (Portugal) to assess movement patterns and connectivity of adult individuals. This multidisciplinary approach provided a robust overview of meagre population structure and connectivity in the Atlantic. Nuclear SNP-genotyping showed a clear differentiation between the European and African populations, with significant isolation of the few known Atlantic spawning sites. The limited level of connectivity between these subpopulations is potentially driven by adults, capable of wide-ranging movements and connecting sites 500 km apart, as evidenced by tagging studies, whilst larval dispersal inferred by modelling is much more limited (average of 52 km; 95% of connectivity events up to 174 km). Our results show sufficient evidence of population structure, particularly between Africa and Europe but also within Europe, for the meagre to be managed as separate stocks. Additionally, considering the low degree of larvae connectivity, the implementation of marine protected areas in key spawning sites could be crucial towards species sustainability.
- Small MPAs do not protect cuttlefish (Sepia officinalis)Publication . Abecasis, D.; Afonso, P.; O'Dor, R. K.; Erzini, KarimMarine reserves have been widely implemented as tools for biodiversity conservation and fisheries management, amongst other goals. A large number of empirical studies have focused on their effects on reef fish populations. Yet, few studies have looked at their effectiveness on semelparous species such as cephalopods, in spite of their commercial importance in many coastal regions across the globe. In this study we combine behavioural (biotelemetry) and demographic (experimental fishing) data to understand the effects of the Luiz Saldanha Marine Park (LSMP) on local populations of cuttlefish, Sepia officinalis. We used a beyond-BACI design to analyze the possible effect of the implementation of a no-take area on the abundance and biomass of this species and acoustic telemetry data to assess its site fidelity and movements within the study area. Results indicate that there was no detectable effect of the implementation of the no-take area on the abundance or biomass of cuttlefish. We found evidence that acoustically tagged adult cuttlefish leave the reserve a few days or weeks after tagging. The fact that cuttlefish have low site fidelity inside the reserve and large movements across and beyond the study area explains why there is no increase in the population inside the MPA. These results suggest that small coastal marine reserves such as the LSMP are not effective in providing long term protection to cuttlefish populations and, probably, those of other short-lived, highly mobile cephalopods. (C) 2013 Elsevier B.V. All rights reserved.
- Toward adaptive management of coastal MPAs: The influence of different conservation targets and costs on the design of no-take areasPublication . Abecasis, D.; Afonso, P.; Erzini, KarimThere is still much discussion on the most appropriate location, size and shape of marine protected areas (MPAs). These three factors were analyzed for a small coastal MPA, the Luiz Saldanha Marine Park (LSMP), for which a very limited amount of local ecological information was available when implemented in 1998. Marxan was used to provide a number of near-optimal solutions considering different levels of protection for the various conservation features and different costs. These solutions were compared with the existing no-take area of the LSMP. Information on 11 habitat types and distribution models for 3 of the most important species for the local artisanal fisheries was considered. The human activities with the highest economic and ecological impact in the study area (commercial and recreational fishing and scuba diving) were used as costs. The results show that the existing no-take area is actually located in the best area. However, the no-take area offers limited protection to vagile fish and covers a very small proportion of some of the available habitats. An increase in the conservation targets led to an increase in the number of no-take areas. The comparative framework used in this study can be applied elsewhere, providing relevant information to local stakeholders and managers in order to proceed with adaptive management. (C) 2015 Elsevier B.V. All rights reserved.