Suchergebnisse

Short communication ; The seagrass Posidonia oceanica is able to reproduce by asexual formation of plantlets directly in the inflorescence. Pseudoviviparous plantlets were observed during May 2004 in 26% of the inflorescences in a P. oceanica meadow off the island of Formentera (Balearic Islands, Western Mediterranean Sea). We do not know how frequently pseudovivipary occurs in Posidonia oceanica, nor the mechanisms triggering it, but this strategy can contribute significantly to short-distance dispersal and meadow maintenance, which is especially relevant in a species whose meadows can persist for thousands of years and whose colonization of new space occurs very slowly. ; This work was supported by the Fisheries Department (Direcció General de Pesca) of the Balearic Government. ; Peer reviewed

13 páginas, 6 figuras, 5 tablas. ; The use of MPAs to recover fish stocks in littoral areas of the western Mediterranean has made it possible to obtain time dataseries on the biomass evolution over the last decade. The biomass of six fully protected MPAs increased between two- and threefold over a period of five years. After this time the biomass remained stable. This pattern allowed us to adjust logistic curves between the biomass and protection time, and to estimate the carrying capacity (K) of each site. In the present study we investigate the relationships between carrying capacity (K) and habitat characteristics at each protected site. The relationships between habitat/environmental variables and K are analysed by applying generalized linear models. Environmental descriptors showing major effects on biomass are related to depth, exposure, rugosity, and offshore slope at different spatial scales. Comparison of observed and predicted values using the model for exploited sites in the Balearic Islands made it possible to determine their conservation status. This empirical approach to the relationships between environmental factors and fish assemblage biomass could constitute a very useful tool when traditional fishery management based on catch and effort data from the artisanal and recreational fleets is difficult to apply. ; This paper is mostly a result of the projects funded by the Balearic regional Government for the development of MPAs in the Balearic Islands and the co-funded EU projects LIFE 00NAT/E/7303, IFOP ES.R.BAL.3.1.04, ES.R.BAL.3.1.07 and FEP 321NBAL00001. ; Peer reviewed