Preprint volume - SIBM

Density (individuals / 125 m 2 )
Biomass (gr)
20
16
12
8
4
0
3200
2400
1600
800
0
Pre-print Volume – Oral presentations
Topic 3: INTEGRATED COASTAL ZONE MANAGEMENT
D. sargus
Western boundary Eastern boundary
D. sargus
8200 6200 4200 2200 200 1800 3800 5800 7800 9800 11800
Distance from A zone center (Km)
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
164
D. vulgaris
Western boundary Eastern boundary
D. vulgaris
8200 6200 4200 2200 200 1800 3800 5800 7800 9800 11800
Distance from A zone center (Km)
Fig. 2. - Density and biomass (mean+SE) of sea breams across the MPA boundaries (broken vertical
lines). Circles and squares (A zone=black; B-C zones=grey; unprotected areas=white) refer to
sampling carried out in November 2004 and September 2005, respectively.
Densità e biomassa (media+ES) dei saraghi dentro e fuori i confini (linee tratteggiate
verticali) dell’area marina protetta. Cerchi e quadrati (zona A=nero; zone B-C=grigio; aree
non protette=bianco) si riferiscono ai campionamenti effettuati in Novembre 2004 e
Settembre 2005.
Particularly steep gradient of sea breams density and biomass across the reserve
boundaries were recorded in September 2005. Regardless to species, both density and
biomass dropped sensibly just 100 m outside the reserve and remained close to zero in
the westward sampling sites. Along the eastern coasts, sea bream density and biomass
slightly recovered about 1 Km apart from the reserve boundary (Fig. 2). Density and
biomass data of D. sargus fitted significantly a decay model across both reserve
borders, but only during September 2005. In D. vulgaris, the fits for density were
always significant (except eastward in November 2004), whereas a significant gradient
of biomass was detected only in September 2005 across the eastern boundary. The
inflection point (the distance at which mid-reserve density or biomass is halved) of the
logistic decay model was usually located inside the AMP boundaries, within the B or C
zone; in two cases only (both in D. vulgaris), it was outside the MPA borders.
Conclusions - The higher density and biomass of sea breams as well as the larger size
of the individuals within the Portofino MPA than in the adjacent unprotected areas
demonstrated a positive effect of the protection on the sea breams populations. The
very small size of the “no take” area and the low fishing pressure usually occurring in
the B and C zones made all the protected area fairly homogeneous in terms of fish
density or biomass. In the last decade, a number of species heavily targeted by fishing,
such as the sparids D. sargus and D. vulgaris, benefitted from the enforcement of
regulation on fishing activities in the B and C zones (Guidetti et al., 2008). The
patterns of decrease in density and biomass of sea breams observed beyond the western