Vierus, Tom and Gehrig, Stefan and Brunnschweiler, Juerg M. and Glaus, Kerstin and Zimmer, Martin and Marie, Amandine D. and Rico, Ciro (2018) Discovery of a multispecies shark aggregation and parturition area in the Ba Estuary, Fiji Islands. Ecology and Evolution, 8 (14). pp. 7079-7093. ISSN 2045-7758
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Abstract
Population declines in shark species have been reported on local and global scales, with overfishing, habitat destruction and climate change posing severe threats. The
lack of species-specific baseline data on ecology and distribution of many sharks, however, makes conservation measures challenging. Here, we present a fisheries-independent shark survey from the Fiji Islands, where scientific knowledge on locally occurring elasmobranchs is largely still lacking despite the location’s role as a shark hotspot in the Pacific. Juvenile shark abundance in the fishing grounds of the Ba Estuary (north-western
Viti Levu) was assessed with a gillnet-and longline-based survey from December 2015 to April 2016. A total of 103 juvenile sharks identified as blacktip Carcharhinus limbatus (n = 57), scalloped hammerhead Sphyrna lewini
(n = 35), and great hammerhead Sphyrna mokarran (n = 11) sharks were captured, tagged, and released. The condition of umbilical scars (68% open or semihealed), mean sizes of individuals (±SD) (C. limbatus: 66.5 ± 3.8 cm, S. lewini: 51.8 ± 4.8 cm, S. mokarran 77.4 ± 2.8 cm), and the presence of these species over recent years (based on fishermen interviews), suggest that the Ba Estuary area is a critical habitat for multiple species that are classified as “Near Threatened” or “Endangered.”
Specifically, the area likely acts as a parturition ground over the studied period, and potentially as a subsequent nursery area. We identified subareas of high abundance and found that temperature, salinity and depth acted as small-scale environmental drivers of shark abundance. The data suggests a tendency for species-specific spatial use, both horizontally (i.e., between sampling areas) and vertically (i.e., across the
water column). These results enhance the understanding of shark ecology in Fiji and provide a scientific basis for the implementation of local conservation strategies that contribute to the protection of these threatened species.
| Item Type: | Journal Article |
|---|---|
| Uncontrolled Keywords: | blacktip sharks, elasmobranchs, hammerhead sharks, neonates, shark bycatch, young-of-the-year sharks |
| Subjects: | G Geography. Anthropology. Recreation > GE Environmental Sciences Q Science > QH Natural history > QH301 Biology |
| Divisions: | Faculty of Science, Technology and Environment (FSTE) > School of Marine Studies |
| Depositing User: | Fulori Nainoca - Waqairagata |
| Date Deposited: | 18 Sep 2018 02:28 |
| Last Modified: | 18 Sep 2018 03:42 |
| URI: | https://repository.usp.ac.fj/id/eprint/11028 |
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