Tracking sharks to answer questions about predator and prey

An international team of scientists has compiled a dataset of shark movements and interactions with game fishes. The research. published in the journal Ecological Applications, outlines how the scientists were able to track sharks using acoustic telemetry paired with machine learning.     

“It’s so rare to observe multi-species interaction in the ocean,” said Lucas Griffin, the paper’s co-lead author and a postdoctoral researcher in environmental conservation at UMass Amherst.

Many sharks like hammerheads and bull sharks range over large areas of the ocean and are hard to track. There is anecdotal evidence from fishing vessels that suggests that predation by sharks is rising, but there is no scientific evidence of this. 

The researchers focused on the Florida Keys, where they tagged 257 fishes, including 73 sharks, and deployed almost 300 acoustic receivers. When one of the tagged animals came within range of a receiver, its location at a certain date and time were recorded. 

This approach gave the experts raw data on the migratory patterns and ecology of the fishes. The research team then analyzed the research with a machine learning algorithm to more fully understand what was happening. 

“Combining acoustic telemetry and machine learning helped us to answer a host of questions about predators and prey,” said Grace Casselberry, the paper’s other co-lead author and a graduate student in the program in marine sciences and technology in UMass Amherst’s Department of Environmental Conservation. 

According to the analysis of the data, it appears that tarpon and permit return to the same places every year to spawn and the sharks follow them. “They seem to remember where and when the tarpon and permit aggregate,” said Cassleberry.

The scientists said that this research would not have been possible without the cooperation of many agencies and universities, in Florida as well as in the Bahamas. 

“We also worked extensively with the local fishing-guide community to help tag game fish and sharks, and figure out where to place the receivers,” said Griffin. 

“Our lab very much embraces a collaborative and cooperative spirit,” said co-senior author Professor Andy Danylchuk. “We are grateful for our research partners and hope our science will help to hone conservation and management strategies for both game fish and sharks.”

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By Zach Fitzner, Earth.com Staff Writer