In June – during their Autumn tigerfish season– Mavungana Flyfishing in association with the Rivers of Life Institute at the University of Mpumalanga, Ezemvelo KZN Wildlife and Pongola Game Reserve launched a groundbreaking tigerfish tagging project in Lake Jozini, Pongola.
The Mavungana Flyfishing team invested heavily in the research and tagging equipment and the guides tagged 42 fish. For them, and for the likes of Adam Wyness – a Post Doctoral Researcher on the ‘Rivers of Life’ programme – the results will prove invaluable to assist with future conservation efforts of this special fishery.
A REMARKABLE RECAPTURE
Now Adam, who is from Aberdeen (in the UK not the Eastern Cape, bru) has done a lot of rock-n-surf fishing over the years (you know, cod and stuff) but has never gotten into flyfishing. After the initial tagging stint in June, he was well and truly intrigued and got himself a 7WT rod and practiced a bit. He couldn’t wait to get some proper coaching and guiding and try get a tiger on fly during the team’s return in early spring…
For his first session, he was up on the bow and Jonathan Boulton instructed him to drop the fly (a black-over-copper clouser) over the side and strip off several yards of line. Adam dutifully did this – and, while he was at it and staring at Jono – the line ripped out of his hand.
You can guess the rest of the story, but I’m going to tell you anyway:
He grabbed the line and set the hook = fish on! “The fish jumped around as tigers of this class do,” Jono explains, adding that usually, with a fish of this size, the guides would just grab the leader and shake it off for the quickest release possible.
For some reason, Jono grabbed the landing net and netted the fish. “Lying in the net, on its side and just looked like a regular 1kg tigerfish,” Jono says. “Then it flipped in the net and there on the side was this tag…. I went off my nut – screaming and hollering! So anyway a recapture, I couldn’t believe it — we quickly set about taking all the measurements,” Jono says.
‘THEY AREN’T BASS’
According to Jono, the recaptured fish was a male and was caught some three kilometres from where it was initially tagged. “This is unusual because a lot of people – including some of the scientists involved in the study – feel that juvenile tigerfish may be fairly residential, hanging around in one bay, maybe even one set of drowned acacia trees, which I called bullshit on a long time ago,” Jono says.
Now, what they team is puzzling over is wheter a juvenile like that travels two to three kilometres once a week, or every night.. “They are definitely not bass!”
The other thing that is interesting is that this male had lost some condition over the winter, down on the girth a little bit. “Based on girth and the weight, it had lost a noticeable amount of condition which is what one would expect for the winter when the water cools down and the fish’s metabolism slows down,” Jono says.
THE IMPORTANCE OF THE FINDINGS
“Lake Jozini holds a phenomenal population of tigerfish,” Adam says. “It is one of the last strongholds in South Africa for them. They are a species under threat from multiple stressors including water quality, quantity, and barriers to their movement. Pongola is very special as the majority of the shoreline is protected and within reserves, and you can really see this, with very good water quality, and pristine habitats that ensure a very healthy population of tigerfish. However we still do not know enough about the species or the dam to be able to tell how threatened the population is,” he says.
According to Adam, the motivation behind the tagging project is to firstly see growth rates of the individuals. “We take the same measurements when they are tagged as when they are recaptured, and we know the timing of bot captures, so we can measure how much the individual has grown.”
“The second motivation is the movement: For example if a large female fish is tagged in the main dam, but recaptured in the riverine section during spring, we can start to determine if they move into the river areas to spawn. Alternatively, if the fish are recaptured very close to where they are tagged, we can see if they are more resident to an area similar to species like bass.”
Obviously to have the first recapture already is spectacularly lucky but very importantly it confirms that they survive well after the initial tagging and release, and that this tag at least was not removed by other fish – Adam Wyness
ONCE A TIGER, ALWAYS A TIGER
There have been a few previous studies (not many), such as in Shroda dam in Mapungupwe. In that study, there were very low recapture rates (less than 10%), and in some of those recaptures, tags had been bitten off by other individuals. “This was also shown to occur when fish were tagged and put into observation tanks,” Adam says, referring to a study by Prof Gert Steyn at UJ (then RAU). “Our thoughts currently is because this is indeed a predatory instinct, as the tags often resemble parasites such as leeches.”
The study is very much in its infancy and the team is working hard to gather more info through recaptures. If you catch a tagged fish in Lake Jozini, take a photo, record the tag number and as much information as possible on its length, weight and location, and report it to riversoflife.co.za.
To learn more about the tigerfish of Pongola, read ‘Homegrown Honeys’ here.