Tracking pregnant silky sharks in the Red Sea
Colin is using ultrasound technology to understand if pregnant silky sharks are using particular coral reef sites in the Red Sea as pupping grounds. He will be tracking them to decipher their movement patterns. Silky sharks are often highest on the list of fished species in the Indian Ocean and Arabian Region, putting them squarely at risk of major declines. That makes knowing where they are pregnant and pupping – and at their most vulnerable – important to understand, and to inform spatial management plans.
Collin Williams
I grew up in the southern USA and spent much of my time on the water catching all kinds of critters, but fish have always been at the forefront of my mind. My fishy interests eventually developed into a career in marine research, focusing on the spatial ecology and life histories of predatory fishes. I’ve had the opportunity to conduct research at various institutions, including the Dauphin Island Sea Lab, Oregon Sea Grant and the National Marine Fisheries Service. During a particularly dark and cold Alaskan winter, I realised that I needed more sunshine in my life, which...
Tracking pregnant silky sharks in the Red Sea
To identify spatial and temporal patterns of silky shark gestation at offshore coral reefs in the Red Sea.
The harvest of pregnant sharks by fisheries has a disproportionate impact on shark populations. Accordingly, the areas where pregnant sharks gestate and pup are particularly vulnerable areas for these populations and represent locations of high conservation priority. By identifying spatial patterns of pregnant silky sharks in the Red Sea, this project aims to identify priority areas for this species’ protection in an effort to mitigate ongoing regional population declines.
Like many other oceanic sharks, silky sharks have undergone substantial population declines. In the Indian Ocean and Arabian Region, they are often the primary shark species harvested in commercial fisheries. However, the management of regional silky shark populations is limited by a general lack of information, particularly regarding spatial patterns of reproduction. During a recent tracking study on silky sharks in the Red Sea, a very large and presumably pregnant female shark was tagged. Repeated sightings of this individual throughout the year revealed that she maintained her girth for many months before suddenly appearing noticeably leaner. Around the time of this ‘weight loss’, small silky sharks were observed at a provisioning site where the female had recently been resighted. Given that a majority of the silky sharks observed in this region are female, we began to wonder if silky sharks utilise offshore reef habitats in the Red Sea for gestation. This study seeks to determine if gravid females are present at these sites and, if so, to explore any potential seasonal and spatial patterns of gestation. The reefs where silky sharks are commonly sighted are also popular areas for commercial and recreational fishing as well as recreational diving. The results of this project have the potential to identify specific areas where the regional population of these sharks might be particularly vulnerable. Identifying such areas is crucial right now, when human activities in this part of the Red Sea are increasing and spatial management plans for Saudi Arabia’s marine environments are currently being developed.
This project aims to:
- Conduct ultrasound scans on female silky sharks in the Red Sea;
- Identify potential spatial and temporal patterns of silky shark gestation on coral reefs;
- Disseminate findings among regulatory authorities in Saudi Arabia to inform the ongoing restructuring of spatial management frameworks.