Keeping Track of ‘Students’ in a Shark Kindergarten

Photo by Pelayo Salinas De Leon
A school of juvenile Galapagos sharks is recorded by a baited remote video station. Photo by Pelayo Salinas De Leon

By Pelayo Salinas de Leon

Over the past week we have been conducting daily surveys and tagging trips to quantify shark species composition, abundance, and distribution around Clipperton atoll.

We have been using stereo baited remote video stations (BRUVs), where a small amount of bait inside a PVC canister is used to attract sharks and other predatory fishes towards the cameras. Because the video cameras are filming in 3-D, we can use special software to measure each animal’s total length. Marine biologists use total length to estimate maturity stages and the total biomass of fish in the area.

Our preliminary results reveal that Clipperton atoll is a kindergarten for baby sharks! Juvenile and even newborn Galapagos (Carcharhinus galapagensis) and silvertip (C. albimarginatus) sharks are the reef masters around Clipperton coral reefs. On the two-hour camera drops, we have recorded up to 15 individual sharks in an individual video frame and many sharks have given their best pose for the cameras!

Photo by Pelayo Salinas De Leon
A juvenile silvertip approaches one of the BRUVs. Photo by Pelayo Salinas De Leon

In addition to video surveys, we have conducted night fishing trips to catch and tag baby sharks with individually coded radio transmitters. My colleague, Dr. Mauricio Hoyos, has three acoustic receivers located around Clipperton atoll and every time a tagged shark swims past one of these receivers, its presence is recorded.

With this information scientists can determine species-specific habitat use patterns and regional migratory routes. Mauricio is not alone on this quest: a network of scientists involved in the Eastern Tropical —> Read More