Abundance, distribution and habitat preference of H ippocampus guttulatus and H ippocampus hippocampus in a semi‐enclosed central M editerranean marine area

Abstract

Population abundance, distribution and habitat preference of the M editerranean sympatric seahorses H ippocampus guttulatus and H ippocampus hippocampus were investigated in a semi‐enclosed sea system ( A pulian coast, I onian S ea). A total of 242 individuals of seahorses were sighted in the 11 transects surveyed in summer 2011. H ippocampus guttulatus (n = 225) were 14 times more abundant than H . hippocampus (17). The mean abundance of H . guttulatus for all the pooled sites was 0.018 m −2 ( SE ± 0.003) ranging from a maximum of 0.035 ( SE ± 0.007) to a minimum of 0.008 ( SE ± 0.002). The size structure of long‐snouted seahorse shows a population ranging from 7 to 14 cm ( SL ) with a peak at 10 cm ( TL ). Juveniles (96.0 ± 8.0 mm) represent a significant fraction of the population, accounting more than 21% of the sighted individuals. In M ar P iccolo, H . guttulatus is able to shelter both in monotonous habitats, including the algal beds, and diversified ones, such as the rich filter‐feeder communities that colonize hard substrates. By contrast, H . hippocampus is mainly associated with habitats of low complexity. Today, the M ar P iccolo di T aranto is among the most heavily polluted water bodies in S outh I taly, with trace metals, hydrocarbons, pesticides and organic wastes affecting both biotic and abiotic matrices. However, despite the high level of degradation, the presence of a large mussel farm has avoided the impact of towed fishing gears, and eutrophication of water bodies has ensured a high trophic level that supports large crustacean populations, potential prey for seahorses.

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