ecological effects of marine protected areas empafish project ...

EMPAFISH Booklet no. 1 Ecological effects of Atlanto-Mediterranean MPAs in the EU
1987 and 1989) and four years after it was in place (spring 1994) were
compared. Sampling design was based on three depth strata (10-50 m, 51-
100 m, 101-200 m); twenty-one and thirty hauls were made before and after
the ban, respectively. Eleven target species (nine finfish and two
cephalopods) as well as the total catch were used for comparisons. The total
catch underwent an 8-fold increase in biomass after the four-year ban, and all
the considered species underwent an increase, ranging from 1.2-fold for
musky octopus (Eledone moschata) to 497-fold for gurnard (Lepidotrigla
cavillone). The only decrease was for horned octopus (Eledone cirrhosa).
Further studies showed that the demersal biomass remained at very high
levels in the following years, in both inshore sandy areas and offshore muddy
areas (D’Anna et al. 2001; Pipitone et al. 2001; Pipitone et al. 2004). A model
of distribution was set up using cellular automata for the red mullet
(Badalamenti et al. 2002b).
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o Trophodynamic changes
The consequences for food-web structure of protecting marine communities
from trawling have been explored in the Gulf (Badalamenti et al. 2000b;
Badalamenti et al. 2002d). Using stable isotopes of carbon and nitrogen, our
objectives were to see if mean trophic level and omnivory had increased after
the ban in three of the most common fishery-target species, namely, the
anglerfish Lophius budegassa, Mediterranean hake Merluccius merluccius, and
red mullet Mullus barbatus. We compared size data from before and after the
fishery closure, but we also compared recently derived data from outside and
inside the closed area. In all three species δ13C and δ15N were found to differ
markedly depending on fish size. δ13C was found to decrease in L. budegassa
and M. merluccius but increase in M. barbatus with increasing fish length.
δ15N increased in all three species, and this was thought to reflect feeding at
increasingly higher trophic levels during the animals’ lives. Mean length, and
therefore δ15N derived trophic level, increased after the trawl ban only in the
anglerfish L. budegassa. Based on δ13C and δ15N data, none of the species
became more or less omnivorous after the ban. After 9 years of no trawling,
increases in numerical abundance were not accompanied by substantial sizerelated
trophodynamic shifts in any of the three species of fish studied.
The trophodynamics of three Mediterranean fishes robust to trawling
disturbance was also investigated (Badalamenti et al., in press). Trawling has
a significant effect on the structure of marine communities, yet the ubiquity of
trawling impacts makes the testing of spatial variation in such effects difficult.
This study examines trawling impacts on fish trophodynamics by comparing
trophodynamics in the Gulfs of Castellammare and Termini Imerese (northern
Sicily) the first of which has had a large no-trawl area since 1990. Nitrogen
and carbon stable isotope data were used to assess trophic levels and source
of production supporting 3 demersal fish species (Mediterranean hake, red
mullet and anglerfish). The exclusion of trawling has no ecologically significant
effect on fish trophic level at size and no systematic effect on the sources of
production supporting any species at the size sampled, thus discounting a
large bottom-up influence on fish trophodynamics. Smaller scale variations
(east/central/west sectors or depth strata) in δ13C isotopic signatures