By Patrick Cooney
During the cold winter this year at the Shedd Aquarium in Chicago, Illinois, one of Shedd’s researchers was heading to the warm waters of the Bahamas to better understand the movement patterns of Nassau Grouper.
On a recent trip to the Bahamas, Kristine and a team of collaborative scientists set out to capture and tag Nassau Grouper. A device (acoustic tag) was surgically implanted in the abdomen of the fish to track its movements, and an external tag was implanted into the muscle and skin so that if an angler caught this fish, they would know there was a research tag inside.
Traps were set and fish swam in…but how will the divers ever get those fish to the boat? With a fish elevator of course!
Kristine says, “Our lucky grouper subjects were caught carefully either by hand while scuba diving or by live traps. We built our traps in the style of commercial fishermen. However, we couldn’t just pull the traps up quickly from the boat like the fishermen do because we needed to keep our groupers alive. Therefore, we Scuba dive down to the traps and bring them up very slowly with a lift bag over a period of about 45 minutes. The lift bag is then attached, filled slowly with air, and then we all proceed to the surface together. This method minimizes barotrauma: the risk of the internal organs expanding too quickly with a change in pressure as the fish ascend.”
But what happens to the fish after they get tagged?
Kristine goes on to say, “After catching and surgically implanting grouper with acoustic tags, each individual is returned to the reef by hand to monitor is release. The acoustic tracking transmitter is in the fish’s body cavity, and therefore is not visible from the outside. However, a secondary external yellow tag is visible on its left dorsal side in the video. If someone catches this individuals in the future, they can report it back to the scientists using the contact information on the tag. The capture information can be used to learn a lot about the grouper’s journey!”
We look forward to a follow up in the future on how this research is going and what researchers find from the fish tracking tags.
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