J. Forcada et P. Hammond, GEOGRAPHICAL VARIATION IN ABUNDANCE OF STRIPED AND COMMON DOLPHINS OFTHE WESTERN MEDITERRANEAN, Journal of sea research, 39(3-4), 1998, pp. 313-325
Line-transect data from sighting surveys conducted in the western Medi
terranean (in 1991) and the Alboran Sea (in 1992) were analysed to est
imate densities and numbers of striped and common dolphins in various
areas of the western Mediterranean. Density of striped dolphins in the
northwestern Mediterranean was estimated as 0.20 dolphins km(-2) (CV
= 0.24; 95% CI = 0.12 and 0.32) and was 41% higher than in the southwe
stern Mediterranean, where it was estimated as 0.12 dolphins km (CV =
0.38; 95% CI = 0.05 and 0.25). The highest densities were observed in
the Liguro-Provencal basin, with 0.24 dolphins km(-2) (CV = 0.26; 95%
CI = 0.14 and 0.40), and the Alboran Sea, with 0.20 dolphins km(-2) (C
V = 0.33; 95% CI = 0.10 and 0.36). These areas, and especially the Lig
urian Sea, appear to be the most productive in terms of the food consu
med by striped dolphins. Common dolphins were abundant only in the Alb
oran Sea with an estimated density of 0.16 dolphins km(-2) (CV = 0.40;
95% CI = 0.08 and 0.35), scarce in the south Balearic area and almost
absent in the northwestern Mediterranean. The magnitude of the dolphi
n by-catch in fishing operations in the Alboran Sea and other areas st
resses the need for further assessment of densities and numbers, notab
ly in the Alboran Sea and the North African Mediterranean waters. (C)
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