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Over the last few years, there has been an increase in the number of reports of fish being taken by sharks from anglers lines. It appears that this is becoming ever more common, much to the frustration of offshore anglers, particularly off the KZN coast. Speaking to various people about this issue, I found that there appear to be a number of diverse views as to the reason for this increase.

There is also a fair bit of finger pointing between the different user groups of the offshore reefs, and I thought that it would be interesting to do a bit of research and try to get some clarity on the matter.

The purpose of this article is not to find an easy solution, but to stimulate thought and to broaden our thinking as to what the reasons are for this issue, and how we can best deal with it as fishermen.

In the interests of getting a balanced view on the subject, and in order to get opinions from all interested parties, I interviewed dive operators, recreational fishermen, commercial fishermen and scientists from both the KZN Sharks Board and ORI. It was actually quite an interesting project, with some parties agreeing on certain points and having opposing views on others.

What everybody agrees on is that there is a higher incidence of fish being taxed by sharks when fishing offshore reefs than at any time in the past. Old sea dogs say that they have lost more fish to sharks in the last two years than in the last 30 years of fishing. This is a substantial increase and it indicates that something has changed drastically.

Many fishermen feel that there has been a population explosion of sharks, and that this is the reason why we are losing so many fish to them. It is a scientific fact, though, that globally sharks are on the decline, mainly due to shark-finning activities. If there is an increase in certain species of shark off KZN, then that is a localised increase in contrast to the global trend.

What seems to be one of the major factors contributing to the issue is the fact that sharks have learnt that ski boats provide easy meals, and they have adapted their behaviour in order to cash in on this.

The sound of an outboard motor arriving at a reef appears to attract sharks immediately, so that as soon as a fish is hooked and brought near the boat, it will be taken before it can be landed. Some sharks have learnt to station themselves below a drifting or anchored boat and wait for the fish to be tired out by being fought on the line, so that easy meals can be obtained one after another.

Some fishermen feel that the dive industry is to blame for habituating sharks to boats, and teaching them that boats mean free meals, by their habit of chumming for sharks in order to give divers the opportunity to swim with the sharks on certain reefs, such as Aliwal Shoal and Protea Banks. The divers, however, claim that they only use a scent trail to attract sharks, without feeding the actual sharks. They use around 3kg of sardines in a bait stem, sending out a scent trail. Even if the sharks were to eat the 3kg of sardine, it wouldn’t be enough to sustain the number of sharks that are attracted to the scent.

Sharks are being attracted to fishing boats, not necessarily through chumming, but due to a couple of factors. Firstly, those that are bottom fishing are also putting a scent trail into the water with their bait. Secondly, any undersized fish and by-catch that is being released while suffering from barotrauma (bloating), end up floating downcurrent of the boat, effectively creating a chum trail.

Thirdly, the struggles of hooked fish send out panic signals that quickly attract sharks. Sharks are not simply mindless killing machines; they are highly evolved apex predators, with the ability to learn and adapt in order to survive. It appears that some populations of sharks on popular fishing reefs have learnt that fishing boats are a source of easy food.

The reasons that this has become more common recently are probably due to a combination of factors. Firstly, there is more fishing effort currently than ever before. Where thirty years ago a few boats would be launched on weekends, now there are commercial boats, charter boats and recreational boats on the water every day of the week. Sharks and fishermen are competing for the same resource, and as the fish stocks become depleted, so the competition increases.

 Another factor which could con-tribute to the high number of specific species of sharks being so prevalent on our offshore reefs is that the inshore fishery has been severely depleted along the KZN coastline. The amount of subsistence fishing in the surf has increased dramatically over the past few years and this has lead to inshore fish stocks taking a beating. Estuaries, which are nursery grounds for many species of fish, have lost their ability to fulfil this function, mainly due to siltation.

The shark nets in KZN kill many of the larger sharks in the inshore areas and this means that there is less predator pressure on small sharks in these areas. Small sharks feed on the bony fish inshore. With the inshore fishery being depleted due to the above reasons, it is possible that species such as blacktips and duskies are spending more time looking for food over offshore reefs than they did in the past.

Geremy Cliff at the KZN Sharks Board feels that the easy meals that sharks have learnt to obtain from ski boats may also have affected their natural seasonal migration patterns. If food is plentiful and easy to obtain, there may be less incentive for the sharks to move when they normally would have, meaning that there are greater numbers of sharks on local reefs for longer periods. 

Studies have been done in the Breede River, using acoustic tags on sharks, and it is clear that the sharks have learnt to station themselves beneath anchored boats in the river in order to obtain easy meals. It would appear that the signal that triggers this behaviour offshore is the sound of an outboard motor. Sharks have learnt to associate the sound of a motor approaching a reef, then being turned off, with injured and struggling fish.

This appears to be corroborated by the fact that paddle ski fishermen and spearfishermen are not being hassled for their catches to the same degree as ski boat anglers.

Some dive boat operators report that when trying to chum sharks up at dive sites, if they are unsuccessful, they start their motors up and approach the spot again, behaving like fishing boats, and this often brings the sharks in.

Whatever the reasons for the increase in sharks taxing catches, the biggest concern for fishermen is that they are losing a lot of valuable tackle, and also having to put in a lot more effort to land their quotas. The concern of conservationists is that there is a much higher mortality of our linefish than what is being indicated by catch returns.

Some fishermen report landing one in ten fish when anchored above a congregation of geelbek or dusky kob, with the other nine being eaten by sharks. This means, in that situation, that to beach with 100kg of fish, a ton of fish will have been killed – a massive concern when you think that this fishing effort is being done on congregations of spawning adult fish, whose population is already under severe pressure.   

How can we minimise the problem?

There are a few things that we can do to lessen the impact that sharks have on our fishing outings: Fish with heavier tackle; playing fish for longer with light tackle increases the chances of being taxed. If a shark is sitting under the boat taking your fish, then move to another spot.

Revive fish properly before releasing them. In the case of fish suffering from barotrauma, use a weighted release-assist mechanism to get them back down.

If dropping anchor on a spot, wait for 20 minutes before starting to fish. Sharks that have been attracted by the sound of your motors may become bored and move off.

I would strongly discourage the practice of killing sharks in order to take them out of the equation. These apex predators are a very important part of the ecosystem; killing them will not improve the fishing in the long term, and could in fact be disastrous to our fishery.

 

Craig Thomassen is the presenter of Inside Angling, which can be seen on Supersport 6 on Monday nights at 7pm.