ecological effects of marine protected areas empafish project ...

EMPAFISH Booklet no. 1 Ecological effects of Atlanto-Mediterranean MPAs in the EU
Using data from the MEDITS surveys conducted in the subsequent years
(MEDITS 2001, 2002, 2003; Anon. 2002, 2003, 2004), fishing induced
changes in composition, diversity and size spectra of demersal fish
communities in the strait of Sicily, in areas exposed to different levels of
fishing pressure (Gristina et al. 2000; Fiorentino et al. 2003, 2004; Gristina et
al. 2003; Gristina et al., 2004). According to Gristina et al. (2003), the
Shannon-Weiner diversity index (H`) and the taxonomic distinctness index
(∆) (Hall and Greenstreet, 1998) do not seem to be the best measures to use
to investigate the impact of fishing on the demersal fish communities; in fact,
significantly lower diversity values were not at all clearly linked to trawl
disturbance. On the contrary, the structure of the demersal assemblages and
the analysis of size spectra proved to be more sensitive for detecting changes
in the demersal communities. Gristina et al., (2004) developed a multispecies
index defined as the ratio between bottom-dwelling fish and overall-fish
biomasses (BOI index). According to these authors, the BOI index used in
association with biomass indices, seemed to distinguish between areas with
different levels of trawling pressure.
� Benthic communities
Prior to 2003, information on the benthos and benthic assemblages and on
their ecology within the FMZ was limited to relatively shallow waters, 50 – 80
m (Biomaerl team 1998, 1999; Borg et al., 1998a, 1998b; Dimech et al.,
2004; Lanfranco et al., 1999; Schembri, 1998). In an effort to address this
lack of basic information, the Malta Centre for Fisheries Sciences (MCFS)
together with the Marine Ecology Research Group (MERG) of the Department
of Biology of the University of Malta initiated several studies on the benthic
habitats and biotic assemblages of actual and potential fishing grounds within
the Maltese FMZ in the ambit of the MEDITS, GRUND and MedSudMed
programmes. Research activities which originated from the MEDITS 2003,
2004, 2005 and GRUND 2003, 2004 research cruises included studies on:
• the benthic assemblages and sediment characteristics of the deep
water fishing grounds within the FMZ (Page 2003; Dimech & Schembri
2003, 2004, 2005);
• the relationships between demersal commercial species, benthic
assemblages and sediment characteristics in the FMZ (Dimech et al.,
2005a, 2005b);
• the abundance of anthropogenic litter in Maltese waters and its use as
a substratum by epibenthos (Pace 2006);
• selected decapod of commercial importance (Aristeomorpha foliacea,
Parapenaeus longirostris, Nephrops norvegicus and on dominant
echinoderm species (Cidaris cidaris, Stylocidaris affinis) inside and
outside the FMZ (Balzan 2006).
The latter study showed that for all the decapods, smaller sized individuals
were recorded for within the Malta FMZ than found outside, while only P.
longirostris was found to be significantly more abundant within the FMZ than
outside (Balzan, 2006).
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