Zuckerreaktionen

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Characterizing and predicting the distribution of Baltic Sea flounder (Platichthys flesus) during the spawning season

Identi\ufb01cation of essential \ufb01sh habitats (EFH), such as spawning habitats, is important for nature conservation, sustainable \ufb01sheries management and marine spatial planning. Two sympatric \ufb02ounder (Platichthys \ufb02esus) ecotypes are present in the Baltic Sea, pelagic and demersal spawning \ufb02ounder, both displaying ecological and physiological adaptations to the low-salinity environment of this young inland sea. In this study we have addressed three main research questions: 1) What environmental conditions characterize the spatial distribution and abundance of adult \ufb02ounder during the spawning season? 2) What arethe main factors de\ufb01ning the habitats of the two \ufb02ounder ecotypes during the spawning season? 3) Where are the potential spawning areas of \ufb02ounder? We modelled catch per unit of e\ufb00ort (CPUE) of \ufb02ounder from gillnet surveys conducted over the southern and central Baltic Sea in the spring of 2014 and 2015 using generalized additive models. A general model included all the stations \ufb01shed during the survey while two other models, one for the demersal and one for the pelagic spawning \ufb02ounder, included only the stations where each \ufb02ounder ecotype should dominate. The general model captured distinct ecotype-speci\ufb01c signals as it identi\ufb01ed dual salinity and water depth responses. The model for the demersal spawning \ufb02ounder revealed a negative relation with the abundance of round goby (Neogobius melanostomus) anda positiverelation withSecchi depth and codabundance. Vegetation and substrate did not play an important role in the choice of habitat for the demersal ecotype. The model for the pelagic spawning \ufb02ounder showed a negative relation with temperature and bottom current and a positive relation with salinity. Spatial predictions of potential spawning areas of \ufb02ounder showed a decrease in habitat availability for the pelagic spawning \ufb02ounder over the last 20 years in the central part of the Baltic Sea, which may explain part of the observed changes in populations' biomass. We conclude that spatiotemporal modelling of habitat availability can improve our understanding of \ufb01sh stock dynamics and may provide necessary biological knowledge for the development of marine spatial plans

Small scale fisheries in Europe: A comparative analysis based on a selection of case studies

Full text: http://archimer.ifremer.fr/doc/00118/22934/20757.pdf (Version "auteur", 0.44 Mo)International audienceSmall-scale fisheries have traditionally received less research effort than large-scale fisheries and are generally under-studied in Europe. In spite of their comparatively low volume of catches and economic importance, small-scale fisheries are socially important and an integral part of the European coastal zone. Considering the high heterogeneity of situations and the paucity of quantitative data, we used an analytical methodology based on the comparative method. We carried out an analysis of small-scale fisheries (SSFs) in Europe based on a selection of nine case studies. Our objective was to obtain a comprehensive description of small-scale fleets covering different areas/fisheries/species, encompassing the diversity and specific conditions under which SSFs operate, in order to demonstrate the ecological and social sustainability of this often overlooked fisheries segment. A common approach formulated so that the case studies could be compared with the case histories of other competing users, required that for each set of criteria - technical, biological, socio-economic, and institutional - a set of relevant items and indicators was established. An analysis of characteristics common to the selected case studies is conducted and an attempt made to extend our comparisons to the whole of the European Union. Our results show that (as compared with large-scale fleets, their main competitor) small-scale fleets: (i) are composed of smaller vessels and, consequently, travel lower distances to fishing grounds, and are more reliant on coastal areas; (ii) have smaller crews (although the global employment figure is similar to that of large-scale fleets in Europe); (iii) use mostly, but not exclusively, passive gears; (iv) use multi-purpose fishing approaches, and can change the fish species they target during the year; (v) have lower extraction rates; (vi) have lower total capital investments (including fishing rights), turnover and costs; and (vii) have lower fuel consumption, making them less sensitive to changing oil prices. Dependence on subsidies is lower (viii). Involvement in fisheries management is variable, conservation and access regulation measures are largely local in origin. For the selected case studies, the most significant competitors are large-scale fleets, and recreational fisheries, but other sources of interaction (water quality, invasive species, etc.) cannot be ignored