The genetic connectivity of the silky shark (Carcharhinus falciformis) across Indonesia

Abstract

Silky shark (Carcharhinus falciformis) has been listed as CITES Appendix II and Vulnerable by IUCN red list. Reports from Indian, Pacific and Atlantic Ocean showed a sharply declining C. falciformis population every year, including in Indonesia. Despite this issue, information on local and regional genetic population structure of this species is still lacking. In this research, we aim to assess the population condition of C. falciformis across Indonesia Fisheries Management Area (FMAs), using mitochondrial genetic data. A total of 225 fins or tissue samples collected from various traditional fish market and shark-fin exporters across Indonesia, then sequenced using mtDNA control region, yielding 510 bp of sequence. The overall Haplotype diversity is high (h: 0.534 ± 0.035). Meanwhile, the nucleotide diversity (θπ) is low (range of 0.00067 – 0.00201) compared to the Atlantic and Red Sea. In addition, the genetic diversity of C. falciformis in Indonesia is lower than other pelagic shark species. Furthermore, AMOVA and Fst results showed a significant structure between Aceh and other locations in Indonesia. Samples from across Indonesia also showed a certain degree of haplotype sharing but with significant genetic structure with others, additionally, the combined dataset revealed a pattern that is similar to previous studies, which showed that the Atlantic population is different from the rest. The distinct genetic population of C. falciformis observed in Aceh may indicate that this population should be managed separately. Meanwhile, the shared genetic information within the Timor Sea indicates the necessity of establishing a co-management plan between Indonesia and neighbouring countries such as Timor-Leste and Australia to ensure the sustainable use of this marine resource.