A useful contribution to science or a clumsy yet well-intentioned way of doing damage to fish? Matt Kennedy investigates what the science of fish tagging is all about, and how a regular citizen scientist like yourself can get involved.

There’s a good chance you’ve caught a tagged fish along South Africa’s coastline and in its estuaries. Perhaps you are already into tagging or, like me, have seen others do it and wonder about the who/what/when and where of the whole shebang. To get a few answers I spoke to a couple of experts: Dr Bruce Mann, the former senior scientist at the Oceanographic Research Institute (ORI) and Dr JD Filmalter, an experienced ichthyologist, fish scientist and veteran tagger (grunter, kob and GTs are his speciality) who also happens to be The Mission’s in-house authority.

In South Africa, data collected from tagged fish goes through ORI. Their Cooperative Fish Tagging Project (CFTP), which has been running for over 40 years, encourages the sharing of fish and catch data.

Bruce says, “Fish are normally tagged with a unique number so that the same individual can be recognised if it is recaptured and its movement between two points in time can be recorded as tagging location and recapture location. Similarly, if the fish’s length is measured at tagging and again at recapture, we can learn how much it has grown over time.”

“There are obviously more complicated types of tags available such as acoustic, archival and satellite tags which each provide different measures and data respectively,” he says.

So, why bother? “Well, there are several scientific reasons for tagging fish” says Bruce. “We can conduct population assessments (normally done within closed systems like in dams or lakes); assess fishing mortality rates (i.e. the recapture rate can be linked to the fishing mortality rate under certain conditions); but most often tagging is used to determine movement patterns and growth rates of any particular species.”

Tagging is mostly done by fisheries scientists, but volunteer anglers who are interested in contributing to research can get involved and make a difference because it enables more fish to be tagged over a wider area at considerably lower cost. It also encourages catch-and-release and has had positive impacts on the pro-conservation behaviour of anglers.

So as you sit there in your toit Teesavs giving the horizon your best thousand-mile stare, consider adding a lab coat to your ensemble because this is what is referred to as “citizen science”.

 “Such tagging is normally done under the auspices of an established tagging project where the species tagged, the size of fish tagged, the type of tags used, the best practice for hooking, landing, handling, tagging and releasing fish is carefully specified in accordance with an animal ethics policy,” says Bruce, “and the data is strictly recorded and stored.” The key term there is “carefully specified”, because we have seen on numerous occasions wannabee fish taggers invoking the spirit of The Simpsons’ Ralph “I’m helping” Wiggums and then getting it wrong.

Find out more about fish tagging, science, and how you can get involved by reading the full article in issue 51 below. It’s free bru!