Browsing by Author "Caselle, Jennifer E."
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- Fishers' behaviour in response to the implementation of a marine protected areaPublication . Horta e Costa, Bárbara; Gonçalves, Leonel; Erzini, Karim; Caselle, Jennifer E.; Cabral, Henrique N.; Gonçalves, Emanuel J.Marine Protected Areas (MPAs) have been widely proposed as a fisheries management tool in addition to their conservation purposes. Despite this, few studies have satisfactorily assessed the dynamics of fishers' adaptations to the loss of fishing grounds. Here we used data from before, during and after the implementation of the management plan of a temperate Atlantic multiple-use MPA to examine the factors affecting the spatial and temporal distribution of different gears used by the artisanal fishing fleet. The position of vessels and gear types were obtained by visual surveys and related to spatial features of the marine park. A hotspot analysis was conducted to identify heavily utilized patches for each fishing gear and time period. The contribution of individual vessels to each significant cluster was assessed to better understand fishers' choices. Different fisheries responded differently to the implementation of protection measures, with preferred habitats of target species driving much of the fishers' choices. Within each fishery, individual fishers showed distinct strategies with some operating in a broader area whereas others kept preferred territories. Our findings are based on reliable methods that can easily be applied in coastal multipurpose MPAs to monitor and assess fisheries and fishers responses to different management rules and protection levels. This paper is the first in-depth empirical study where fishers' choices from artisanal fisheries were analysed before, during and after the implementation of a MPA, thereby allowing a clearer understanding of the dynamics of local fisheries and providing significant lessons for marine conservation and management of coastal systems.
- 'Reserve effect' within a temperate marine protected area in the north-eastern Atlantic (Arrabida Marine Park, Portugal)Publication . Horta e Costa, Bárbara; Erzini, Karim; Caselle, Jennifer E.; Folhas, Henrique; Gonçalves, E. J.Benefits of marine protected areas depend on local ecological and socio-cultural aspects which are critical to the success of the protection measures. In particular, before-after comparisons are indispensable to disentangle the effects of protection from those of different physical and ecological characteristics among areas. Using underwater visual surveys, we assessed whether biomass and abundance of temperate reef fish assemblages and target invertebrates increased inside a no-take area in the Arrabida Marine Park (Portugal) 3 to 4 yr after its establishment. Data were compared to a previous study, conducted 10 yr before protection was effective. Control-effect comparisons after reserve establishment showed a positive response of legal-size demersal fish and below legal-size target invertebrates. The first evidence of protection was found in biomass but not in numbers. Non-target groups and below legal-size demersal fish had a significant interaction among reserve and habitat complexity indices for either density or biomass, suggesting a lack of a reserve effect. Before-after comparisons revealed non-significant patterns of increase in numbers of target species compared to non-target ones. The most important commercial species showed the largest increase in density after protection was established. Significantly higher abundances and proportionally heavier individuals of these species were also found inside the reserve in the control-effect comparisons. These findings are reinforced by an increasing trend in landings which are consistent with the early detection of a reserve effect.
- Tropicalization of fish assemblages in temperate biogeographic transition zonesPublication . Horta e Costa, Bárbara; Assis, J.; Franco, Gustavo; Erzini, Karim; Henriques, Miguel; Gonçalves, Emanuel J.; Caselle, Jennifer E.Biogeographic transition zones in marine temperate systems are often hotspots of biodiversity, with high levels of resilience to short-term climate shifts due to naturally occurring cyclic oscillations of oceanographic conditions. However, these environments are likely vulnerable to a steady global warming scenario in which these cyclical conditions could be disrupted. Here, we evaluate how changes in local oceanography affect the structure of rocky reef fish assemblages over a period of 50 yr in a biogeographic transition zone. Using a 12 yr time series of rocky reef fish assemblage structure, we identified the set of oceanographic variables that most influenced assemblage dynamics. Descriptive and predictive models (multivariate regression trees) were compared to observed data using the area under the curve. Winter northward wind stress and sea surface temperature (SST) were the most important drivers of change in assemblage structure. Only warmer years had indicator species with warm-temperate or tropical affinities. A fish assemblage 'tropicalization' index was developed in response to both local-spatial resolution and short-term environmental variation (1993-2011), and to regional spatial resolution and long-term SST (1960-2012). Predictive modelling for the last 50 yr revealed that species with tropical affinities have increased in frequency compared to cold-temperate species, coinciding with the trend of increasing mean winter SST. Since the mid-1980s, warm-temperate and tropical species have responded rapidly to more frequent warm winters, suggesting that species distributions are shifting polewards. Our results support a hypothesis that cold species retreat more slowly than the advance of warm species. We discuss the importance of transition zones as ` barometers' of climate change.