Tagging large trout in the canals in the South Island of New Zealand... 

“He’s tagged! That’s a tag!”

After what had been an unusually slow morning of fishing at the canals, Lance’s excitement cut through the stillness and jolted me into action. I sprinted over to the ute, grabbed the landing net, and proceeded to run back towards the hooked fish, juggling both the net and my camera while trying to film the experience for my YouTube channel. I’ve fished with Lance Gill (better known as @fishthedriftnz) a lot over the past few years, especially around the canals, but this was the first time I had witnessed a tagged trout, so we were feeling the pressure to land this remarkable fish.

If you haven’t heard about Fish and Game’s tagging programme, let me briefly introduce the project. When sustained heavy rain fills Lake Tekapo beyond a level where excess water can be managed through the Tekapo Canal, water is then spilt into the dry riverbed of the Tekapo River. Once lake levels return to a manageable level the spillway is turned off, leaving the normally dry riverbed with several small pools that typically contain a fair few fish. Fish and Game have made use of this opportunity by salvaging the stranded fish, embedding a tag near the trout’s dorsal fin, and then releasing them back into the Tekapo Canal. These tags then allow Fish and Game to conduct research on the natural growth rates of trout that make their way from Lake Tekapo into the Tekapo canal, by comparing the data recorded when the fish was tagged, and the measurements provided by anglers that catch one of these fish. Since the start of the tagging programme, around 200 trout have been caught by anglers, but only half of these have had the key measurements recorded by the angler.

By the time I reached Lance with the net, the stunning brown trout was approaching the bank, but it still appeared intent on peeling line. The fish managed a couple more runs before being coerced back towards the bank. Waiting for the perfect moment to strike, I finally scooped the net under the trout – we had landed it! After admiring the trout’s beautiful colours and markings, we recorded the tag number: 0795, the weight: 12lb, and the overall length: 710mm. Fish and Game informed us that the fish was tagged 1026 days (2.8 years) earlier when it was 392mm long with an estimated weight of 1.4lb. Since it was last measured, it had grown in length by 318mm and put on 10.6lb, which is an average yearly growth rate of 3.8lb.

When interviewing Fish and Game Officer Rhys Adams for the YouTube episode, he said, “When you compare it to some of the other results we’ve had, it’s stock standard for the canals. But when you look at the growth potential that this tagging study has shown us, some of these fish are growing up to 14lb per year.”

Whether they’re able to maintain that growth rate over time remains to be seen, but it’s exciting to be learning more about this unique fishery as new data is received. For the seasoned canal angler, the limited number of tagged trout provides an exciting, new challenge to accomplish, particularly given the scarcity of these fish. If you’re lucky enough to catch one, be sure to support the research project by reporting your catch to Fish and Game ([email protected], or 03 615 8400). The key data to supply is the tag number, the date caught, weight, length, location, and any photos of the fish that you can provide is a bonus.

Watch our full canal adventure and the interview with Fish and Game on YouTube – Episode 72 of The Angler’s Logbook.

August 2023 - James Flett
New Zealand Fishing News Magazine.
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