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Species that have shown strong responses to protection are those that have moderate vagility in relation

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6I5N and 6°C were determlned for plants invertebrdtes and f~s h e s collected from 3 s~t e s on the southern coast of the Mediterranean Island of Mallorca Spdln The sites were separated by distances of 1250 to 3750 m The mean Si5N of plants was 1 1 to 4 1 " W , , benthic Invertebrates 5 9 to 6 g':%) planktonic Invertebrates 5 5 to 5 8% and fishes 8 4 to 13 8%" 6"N became ennched with increasing trophic level The mean 6I3C of plants was -11 4 to -16 3'Xo benthlc invertebrates -14 8 to -16 8'X, planktonlc Invertebrates -19 3 to -19 8 O W b and fishes -16 1 to -19 2"y) There were s~g n~f i c a n t d~f f e iences in the lsotopic c o m p o s~t~o n of ~ndividual specles w~t h i n the plant invertebrate 01 flsh groupings at each slte and there were s~g n~f i c a n t d~fferences in the ~s o t o p~c composit~on of the same specles at dlfferent sites Depleted ' < C was assoc~ated w~t h b e n t h~c food chalns and enrlched ''C w~t h planktonlc chalns The data suggest that b e n t h~c food chalns are Important to the rocky reef assoclated f~s h e s studled as might be expected In a nutrlent poor system where planktonlc product~on IS relatively low Hoivever, the vanance In 6I1C composltlon between sltes was such that the r e l a t~v e s~g n~f l c a n c e of the 2 pdthways could not be determlned I5N measurements indicated that some of the flsh species studled had adopted d~fferent feedlng strategies at d~fferent sites and, as a result ~n d l v~d u a l s of the same species could sometimes be a s s~g n e d to different t r o p h~c groups at different sltes The data suggest that these f~s h e s e x h i b~t plast~clty in t h e~r feedlng strateg~es and this may p r o v~d e them wlth greater adaptlve flexibll~ty to respond to s~t e -s p e c~f~c changes In food avallabllity Moreover the data p r o v~d e emplrlcal support for current theones of food web dynamlcs w h~c h suggest that trophlc levels a r e dynamlc rather than flxed and that multlchannel omnivory IS an Important feature of food webs KEY WORDS Stable lsotopes T r o p h~c interact~ons Variablllty Mediterranean Reefs Feeding strategy

We investigate the effects of the Columbretes Islands Marine Reserve (CIMR, Western Mediterranean) on the adjacent Palinurus elephas (Fabricius, 1787) fishery. After 9 to 12 yr of no-take protection there was a gradient of lobster density from the interior of the reserve up to a distance of about 4 km from its boundary. Catch and effort data were collected onboard commercial fishing boats in the fishery adjacent to the CIMR, and combined with catch per unit effort (CPUE) data from monitoring surveys conducted annually inside the reserve. Generalized additive (GAM) and linear (GLM) models were employed to examine the relationships of CPUE and catch per unit area (CPUA) as a function of distance to the reserve boundary. CPUE showed a significant non-linear decline with distance from the centre of the reserve, with a depression at the boundary followed by a plateau. This depression was caused by local depletion associated with concentration of fishing effort at the reserve boundary, while the plateau suggests that lobster export from the reserve is sufficient to maintain stable catch rates up to 1500 m from the boundary. Commercial catch and effort data were combined to estimate CPUA, which declined linearly with distance from the reserve. Analysis of recaptures of lobsters tagged and released inside the reserve indicates that the density gradient is caused by lobsters emigrating from the reserve.