Page 7 - DeidunSchembri2006

Mo 1ile fauna of infra lilfora/ fringe of Ma/lese beaches 361

Xatt 1-Ahmar samples appears related to the exclusive presence of many fish spe-
cies and the absence of most species of mysids in the uppermost levels of the
infralittoral zone on this beach. Surf zones are often important nursery areas

for fish due to their high Jevels of secondary production by resident crustacean
populations (Brown & McLachlan, 1990) so the inverse relationship between fish

and mysids at Xatt 1-Ahmar may be related to this. Xatt 1-Ahmar has one of the
lowest exposure values of the beaches studied, which may also contribute to the
high population density of fish found here in autumn and winter, when juvenile
fish seek shelter from the turbulence of the open coast. The low popularity of

this beach with bathers (Deidun et al. , 2003) might also explain the high fish
densities. The surf zone sedeiment at Xatt L-Ahmar is relatively coarse (grain size
ranging from 1.00 to 1.55 phi) when compared to that of other beaches (refer to
Tab. l) and this might explain the lack of mysids at this location. Interestingly,

the beach which received the highest input of wrack (White Tower Bay) also had
the highest individuai abundances during both sampling years, although not the
highest species richness.

The results of the feeding functional group analysis agree with expectations;
McLachlan & Brown (1990) report that most surf-zone zooplankton are oppor-
tunists and omnivores, and omnivory was the most represented feeding type in

the present study.
As for the Catalan beaches sampled by Munilla & San Vicente (2005), the

fauna in the centrai Mediterranean beaches studied there was dominated by per-
acarid crustaceans, mainly mysids (the most abundant) and amphipods (the most

species rich). The swimming behaviour of mysids, adapted to move along the
beach, can explain the abundance of this group in the surf zone (Clutter, 1967).

The total number of species (50) and individuals (1699 from a total area of
900 m2) recorded from this study are markedly lower than those from other Medi-
terranean beaches; thus, Munilla & San Vicente (2005) reported 145 species and
29,717 individuals (from a total area of 750 m2) from the Catalan beaches they

studied. This may be related to the different sampling strategies employed in the
two studies but may also have a biologica! basis, perhaps related to the higher
productivity of the northwestern Mediterranean coastline compared to the more
oligotrophic centrai Mediterranean.

In spite of the overall similarity between the fauna! assemblages of the beaches
studied in the present work, the different beaches do not have identica! suites

of species; thus, 30 species (60% of the total found in the present study) were
recorded from one beach only. The majority of these were decapods and polycha-
etes (8 species/16% of ali species each), followed by amphipods and fish (5 spe-
cies/10% of ali species). For amphipods this is hardly surprising since these lack

free-ranging larvae. The majority of the species reported from just one beach were
collected from Ramla on Gozo (10 species were exclusive to this beach). Although
some species occurred on the Maltese beaches only and not on those of the other
islands studied, their absence from the non-Maltese beaches studied here is very

likely mostly related to sampling effort and only to a !esser extent to the physical
characteristics of the beaches.

For the Maltese beaches at least, the results of this study have some impor-
tant implications for conservation. In the Maltese Islands, sandy beaches are an
overali rare type of coast, constituting only 2.4% of the ca 271 km coastline of
the islands; moreover, ali these beaches are pocket beaches separated from each