First description of a sex segregated aggregation of silky sharks (Carcharhinus falciformis)

Photo credit: © Gabriel Velázquez

First description of a sex segregated aggregation of silky sharks (Carcharhinus falciformis) and the frequency and distribution of mating wounds off the tip of the Baja California Peninsula

Darren A. Whitehead | Joel H. Gayford | Edgar Mauricio Hoyos | Nikolai Madland Shorter | Felipe Galván-Magana | James T. Ketchum

Environmental Biology of Fishes 105, 961 (2022)

DOI: https://doi.org/10.1007/s10641-022-01304-x

Abstract

The silky shark (Carcharhinus falciformis) is a pelagic carcharhiniform shark species distributed globally in tropical and subtropical oceans. In this study, we report a seasonal sex segregated aggregation off the southern tip of the Baja California Peninsula and record the distribution and frequency of mating wounds, to determine if males targeted specific regions of the body before and during mating. A total of 210 individual female silky sharks were photographed during mating events from June to July 2021, 63 of which (30%) showed evidence of fresh mating wounds. To quantify differential occurrence of mating wounds in different regions of the body of sampled individuals, we defined 6 regions on each side of the body, and we observed a significant difference in the abundance of mating wounds between these regions (p = < 0.0001). Mating wound frequency did not differ significantly between June and July (p = 0.11), suggesting that these mating events may be longer than previously thought, or that phenological changes could be occurring within populations of C. falciformis in this region. This study highlights the occurrence of a sex segregated aggregation of silky sharks and the implications on their reproductive biology off the tip of the Baja California Peninsula.

Keywords: Carcharhinus falciformis, Gulf of California, Distribution, Mating wounds, Silky shark