| Although habitat selection is relatively well studied in some elasmobranchs, no field or lab studies have focused on sediment preference, which is important to other benthic marine vertebrates. To determine the relative abundance and sediment preference of shallow water benthic elasmobranch inhabitants of North Inlet, SC, we employed 187 30 minute tangle net sets over two sediment types (mud and sand). The majority of our capture consisted of 41 Dasyatis sayi (tagged 37) and 31 Sphyrna tiburo (tagged 14). Although D. sayi had been recorded in North Inlet, previous studies found greater numbers of congeners D. americana and D. sabina. This sampling method yielded a different elasmobranch population structure than was previously found with gill nets and longlines. Neither D. sayi (p=0.885, Mann-Whitney U) nor S. tiburo (p=0.180, Mann-Whitney U) exhibited a sediment preference, site fidelity, or habitat preferences based on temperature, salinity, turbidity or dissolved oxygen in North Inlet, SC. Ex situ experiments conducted on captured D. sayi (dw <52 cm) also showed no sediment preference (p=0.552, Wilcoxon signed ranks test). We conclude that the homogeneity of other habitat selection factors in this system accounts for the lack of sediment preference in these species. |
