Preprint volume - SIBM

Pre-print Volume – Oral presentations
Topic 3: INTEGRATED COASTAL ZONE MANAGEMENT
breams were censused by SCUBA in November 2004 and September 2005. Fish
density was evaluated along strip transects (25×5 m) in shallow (4-7 m) rocky habitat.
During each period, eight replicated transects were surveyed at each of 18 sites: 6
within the MPA (2 at each reserve zone) and 12 in nearby fished areas (6 beyond the
western reserve boundary and 6 beyond the eastern boundary up to a distance of about
3.6 km from the reserve edge) (Fig. 1).
N
1
1 KM
Fig. 1. - Map of the Portofino promontory (Ligurian Sea) showing the different zones (zone A=black;
zone B=dark grey; zone C=light grey) of the marine reserve. The arrows show sampling sites
location within and outside the MPA.
Mappa del promontorio di Portofino (Mar Ligure) con le differenti zone (Zona A=nero; Zona
B=grigio scuro; Zona C=grigio chiaro) della riserva marina. Le frecce indicano la posizione
dei siti di campionamento dentro e fuori l’AMP.
All sea breams along the transect were recorded and their total length estimated to the
nearest 2 cm. Fish weights were estimated using published length-weight relationships
(Froese and Pauly, 2003). To determine the relationships between mean fish abundance
(density and biomass) and distance from the innermost reserve zone, we used a logistic
function (Kaunda-Arara and Rose, 2004). The logistic decay model was fitted
separately for the eastern and western reserve boundaries and only to data initially
showing a significant linear decline across the reserve boundaries.
Results - To evaluate the size distribution of the three species in the study area, each
sample was divided into three size classes (small: 24 cm TL). Large individuals were recorded only within the MPA, whereas fish
samples outside the reserve were dominated by small individuals. To assess gradient in
fish density and biomass across the reserve boundaries only medium and large
individuals (i.e. those most heavily targeted by fishery) were considered. A significant
linear decrease in sea bream density and biomass across the reserve borders was always
observed, except for biomass of D. vulgaris in September 2005, likely due to the
occurrence of many large individuals in the eastern side of C zone. Density and
biomass of both species were usually higher within the MPA zones than outside and in
September 2005 with respect to November 2004 (Fig. 2).
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
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