Oviposition Substrate Preference in Scyliorhinid Sharks
Turner, Alec J.
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Understanding habitat use is key to managing any organism, especially long-lived, late maturing species with low fecundity like chondrichthyans. Despite their abundance and diversity, life history characteristics for most catsharks (Scyliorhinidae) remain poorly understood. Initial observations suggest oviparous scyliorhinid sharks may have substrate preference for oviposition on deep-sea corals. Images from remotely operated vehicle surveys in southern California and the Gulf of Mexico were used to quantify egg case abundance <i>in situ</i> on deep-sea substrates. While there were regional differences in substrate use, the tops of substrates were significantly preferred in all regions. Additionally, regional differences were present for branched and unbranched substrates used <i>in situ</i>. When given a choice of coral, sponge, or rock structures in a choice experiment, female chain dogfish, <i>Scyliorhinus retifer</i>, only laid eggs on the structure mimicking coral morphology. Oviposition site was observed between two experimental trials with different water flow regimes and no significant difference in egg distribution on substrates was observed. Based on these findings, benthic invertebrates, such as sponges and corals, serve as ecologically equivalent substrates that provide the morphology necessary for successful oviposition by female catsharks and contribute to their reproductive success.