20 November 2013

How (and why) to tag a fish…

Renée Leeuwner

World Fisheries Day is celebrated around the world every day on 21 November by fishing communities. A recent United Nations study reported that more than two-thirds of the world’s fisheries have been overfished or are fully harvested, and more than one-third are in a state of decline due to factors such as the loss of essential fish habitats, pollution and climate change. World Fisheries Day celebrations serve as an important reminder that we must focus on the way the world manages global fisheries to ensure sustainable stocks and healthy ocean ecosystems. One way of better managing fisheries is to have reliable data to work from. Renée Leeuwner, Assistant Communications & Sustainability Manager at the Two Oceans Aquarium, recently found out how this data is collected.

Tag! You’re it!!

Recently, I was introduced to a phenomenal project called the South African National Marine Linefish Tagging Project. This project, run by the Oceanographic Research Institute (ORI) in Durban, has been tagging fish and collecting data since 1984.

Twenty-nine years down the line (excuse the pun), the project has more than 5 200 members and has tagged in excess of 260 000 fish!

A tagged yellowbelly rockcod. Photo by Bruce Mann

Most of the project’s members are anglers, both shore- and offshore-based. Requirements for becoming a member include fishing regularly, living near the coast and a good knowledge of fish species. Anglers join the programme by emailing oritag@ori.org.za or contacting the tagging officer telephonically (031 328 8159 / 079 529 0711).

Once they have been approved and have paid their once-off membership fee of R300, they are issued with a tagging kit and an instructional DVD. The actual fish tags are issued are free of charge and once used, are replaced with a new set. By tagging and releasing the fish they catch, the members use their favourite pastime to contribute to the scientific knowledge of our marine heritage.

Chris Wilkinson with a yellowbelly rockcod. Photo by Jade Maggs

So, why would we want to tag fish? To collect as much data as possible, of course! Tagged fish that are recaptured can provide a wealth of information about a species, from migratory behaviour to growth patterns. For example, a whopping 55 024 galjoen have been tagged to date. And some interesting data? Well, one galjoen travelled more than 1 800km from its original tag location before being recaptured. And we thought they were resident! Another galjoen was recaptured more than 14 years after it was tagged.

The second-most tagged fish is the dusky cob. To date, 14 903 of these fish have been tagged. One individual travelled 1 625 km before being captured for the second time. Another stayed free for almost 12 years before recapture.

A recaptured dusky kob. Photo by Bruce Mann

Why is all of this data important? According to Stuart Dunlop, ORI’s tagging officer: “The information gathered from the ORI Tagging Project is extremely valuable, and is used by scientists and managers around the country for policy- and decision-making on linefish management.”

The data collected has also been used in evaluating the effectiveness of our MPAs (marine protected areas) and their contribution to fish stocks. It turns out that MPAs are extremely valuable in replenishing our fish stocks.

But for Dunlop, one of the most important roles of the tagging project is the one of turning anglers into “citizen scientists” and changing their perceptions of the fish they pursue.

“Despite the large quantity of important data collected by this long-term project, the tagging project has also made a major contribution towards changing the ethic of anglers towards catch and release, which undoubtedly goes far beyond the scientific value of the data collected. Not only do anglers now have a reason to capture and release a fish, they are in actual fact contributing to a better understanding of the biology and ultimately conservation of that species.

“In essence, anglers who are members of the tagging project are citizen scientists. This added bonus goes a long way in improving angler awareness about our marine linefish species, as well as contributing towards sustainable fishing.”

So, if you are an angler and want to contribute to the wellbeing of our marine heritage, why not pop an email to oritag@ori.org.za and join this amazing project? You will be making a positive contribution to our marine environment, simply by doing what you love anyway!

A recaptured speckled snapper. Photo by Bruce Mann
Stuart Dunlop with a black musselcracker

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