ecological effects of marine protected areas empafish project ...

EMPAFISH Booklet no. 1 Ecological effects of Atlanto-Mediterranean MPAs in the EU
mortality of P. lividus, the high intensity of fishing in unprotected areas would
explain the patterns observed. Additionally, Sala & Zabala (1996) showed that
the population structure of this species is determined by fish predation within
the protected area of the MIMR, while recruitment success determines the
population structure in unprotected areas.
� Fish movement (including spillover)
As in the other MPAs selected as case studies within the CE project BIOMEX
(http://biomex.univ-perp.fr), studies have been undertaken to test the
hypothesis that spillover from MPAs to neighbouring areas should have as a
consequence the observation of gradients of fish biomass across boundaries.
In Medes, this hypothesis is going to be tested by using UVC, baited video,
and collection of fish eggs and larvae by plankton nets as sampling
techniques, following a sampling design including several sites inside the MPA
plus other sites outside the MPA (to the North). Results of these studies are
being analysed at present.
� Other biological (e.g. density-dependent) effects
Natural mortality (M) rates were determined for five common species (Coris
julis, Diplodus annularis, Diplodus sargus, Serranus cabrilla and Symphodus
roissali) by UVC in the MIMR (Macpherson et al. 2000). This study showed low
variability of M at seasonal and interannual scales. The mortality rates were
not affected by a “reserve effect”, i.e. they were not significantly different
between the protected and unprotected study sites of the MIMR. This finding
was explained by the higher abundance of piscivorous predators in the
protected areas, which are the main cause of natural mortality in fishes.
Macpherson et al. (1997) evidenced a density-dependent effect on mortality
from settlement to recruitment to the adult population in three species of
sparid fishes, Diplodus puntazzo, D. sargus and D. vulgaris. This densitydependent
effect on mortality of settlers explained the low variability in yearclass
strength for the three species studies. Additionally, this study showed
that mortality rates did not differ significantly in protected and unprotected
areas of the MIMR, suggesting that marine reserves are not necessarily a sink
for post-settlement fishes.
The MIMR has also allowed for interesting studies on the reproduction and
territoriality of the dusky grouper Epinephelus marginatus, scarce elsewhere
in the Mediterranean (Zabala et al. 1997a, b). These authors reported the first
observations on reproductive behaviour in this species by scuba diving
surveys in 1996. This study also showed that Oblada melanura preys strongly
on recently spawned eggs, suggesting that high densities of this sparid fish
may undermine the reproductive success of the dusky grouper in the MIMR.
� Effects on habitat (including impact of divers)
MIMR receives ca. 60,000 divers per year, concentrated between April and
September. Most divers visit the same diving places where buoys are located
and maintained by the Park Service. The diving spots represent ca. 10% of
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