Habitat Preference and Population Structure of Two Data Deficient Seahorse (Syngnathidae) Species

Abstract

Ecological studies of seahorses are sparse in the Indian Ocean. The vulnerability of seahorses to overfishing and increased anthropogenic impacts on coastal habitats necessitates better management of wild seahorse populations that in turn requires understanding habitat preferences and population structure. The distribution patterns and population structure of two species of seahorse (Hippocampus fuscus and H. spinosissimus) were assessed for the first time in a tropical estuary in north-western Sri Lanka. Both species have previously not been studied in the wild and have not been known to occur in estuaries. H. fuscus was the more abundant and widely distributed species, and was significantly larger than H. spinosissimus. Both species had significant differences in size between sexes, and the mean height was towards the lower end of the range know for both species. Some sexually mature males were smaller than the size reported in the literature. Seahorses occurred in low densities with patchy distribution, with abundance being higher in areas with the seagrass species Enhalus acoroides and Cymodocea serrulata that appear to be the favored habitat of seahorses within the study area.