By Scotty Kyle
If we are passionate about fish and fishing, we have to accept that some management is always necessary. Except for a very few isolated localities, which most of us will never see, fishermen can’t simply catch and kill fish of any size at any time by any method and in any numbers.
Without sensible management, most fisheries will collapse; even those in the open ocean. We hear that 90% of the large fish in the oceans have already been caught and I suspect this may be near the mark. We all know of extremely important and sometimes very long-standing fisheries, from the Grand Banks cod fishery to many sturgeon fisheries, that have completely collapsed. If there had been realistic management in place, most of these tragedies could have been avoided.
Fisheries must be managed scientifically by competent, objective, qualified people. Scientists and managers of fisheries are like farmers: they have to exercise total control and decide who can fish, how they fish, when they fish and how many of what size fish they can kill, for each species. Common sense and fairness, however, must be important components of any legislation, and norms and standards should be enforced fairly and consistently. The rules should optimize fishing opportunities, while protecting biodiversity and threatened species and guiding anglers to reduce unnecessary fish injury and mortality.
Management decisions must be based on accurate information and, as we all know, trying to work out what is going on below the water surface is no simple task. Some fish grow extremely rapidly. For instance, a dolphinfish (Coryphaena hippurus) can attain 5 kilograms in under a year and die before reaching five years old. Others, such as a Patagonian toothfish (Dissostichus eleginoides), grow extremely slowly, but can live for more than 50 years. Some species undergo essential annual migrations while others remain loyal to a very small territory all their lives. But management of fisheries is about humans as much as it is about fish, and if there are diverse types of users (traditional, commercial, recreational, etc) competing for multiple species, things can become very complex indeed.
Fish tagging can be an important tool, which helps scientists and managers obtain critical insights into fish populations. Through marking and recovering fish we can work out estimates of capture and growth rates, indications of residency and movement, and sometimes even make new discoveries. Here is one example of how fish tagging was used for these purposes.
I was appointed by the provincial conservation body in KwaZulu-Natal, South Africa, to investigate and make recommendations on a fishery that ticked almost all the boxes for complexity and conflict. Situated on the border between South Africa and Mozambique, on the Indian Ocean, the Kosi Bay estuarine system had been home to a traditional fishery, using simple traps made of branches, for several hundred years. The local people relied on this for their food and wellbeing.
A small recreational fishery had recently developed, and relatively affluent people had begun to access the area with modern boats and expensive equipment and were perceived to be catching many fish. The government saw tourism as the best way to uplift the local people and economy resulting in me being employed to investigate the situation. I was to establish if there were adequate fish stocks for the new fishery or if there would be serious competition leading to open conflict. If stocks were found to be adequate, then I had to recommend new management guidelines.
I registered my work as a PhD with the University of KwaZulu Natal, in order to get proper guidance and quickly realised that, apart from a species list, very little was known about Kosi Bay fish. I spent a lot of time interacting with academics, recreational anglers and local people to cover this gap. I suggested that we employ a team of local people and, together, try to work out what was going on. Out of the discussions it became clear that we had to monitor all fishing catches, to establish catch numbers, mass and species compositions for all the fishery components. Then we had to work out how to determine what proportion of the fish were being caught in each fishery, estimate the overall fish populations as well as establish growth rates and movement.
The mark and recapture (tagging) of fish was the obvious tool to assist with all this information. Firstly, we had to find a suitable fish species to tag. This species had to be large and robust enough to take a tag without dying. It also had to be caught in all the major fishery components to allow for estimates of capture rates for each. We then had to capture, tag and release an adequate number and ensure that there was a good tagged-fish information recovery system so that the capture of tagged fish was reported. We would also opportunistically tag other suitable species to give insights into the ecology of all the species.
The fish in the system ranged from the local freshwater tilapia (Oreochromis mossambicus), which grew to about one kilogram, to the fabled, mighty giant trevally (Caranx ignobilis), that can exceed 40 kilograms.
I worked closely with the local authorities so that what I was doing was known by everyone. After meeting with the local Traditional Authority, I held meetings to explain my work and select candidates for the monitoring work. I then asked for a community meeting on the edge of the lakes with the local Paramount Chief to “bless” the work.
After I had explained what we would be doing, and the Chief had publicly endorsed it, I tagged a fish, and gave it to him to release back into the lake. I said that the Chief had now put a reward onto the fish and it was up to his people now to try and catch it, bring it to me and obtain their reward. All went fairly well and we ended up with the traditional fishing area fully monitored by local fishermen.
We monitored all trap catches and other legal local fishing for a period of five years. The recreational anglers mostly stayed at and launched their boats from a government campsite and their catches were monitored by ensuring completion of “catch cards” after each fishing outing plus “ad hoc” checks. Between monitoring all catches and giving a reward for all tags recovered with useful information, we managed to get information on most of the recaptured tagged fish. At the outset we had no idea of total and relative catches, species composition or any indication of fish population size or movement patterns. The monitoring process was carefully administered and checked scientifically and the overall results were useful, clear and satisfactory.
During the study period results showed that the recreational fishers caught approximately 1% of the fish per annum while the traps caught about 4%. The species caught almost all spawned in the ocean, entered the estuarine system as very small fish, grew to maturity in the lakes then emigrated to the ocean to spawn. This meant that the recreational fishers had the first chance to catch adult fish, but left 99 % (approximately) to migrate through the fish trap area where the locals fished. The locals, in turn, further reduced the numbers but, even allowing for inaccuracies, it was probable that “man” only decreased the numbers reaching the spawning grounds by under 10%. Generally, this kind of offtake is regarded as sustainable and should allow good recruitment.
Other important information we obtained was estimates of fish population size. As we knew the total recreational catch and it was roughly 1% of the population, we simply multiplied the total monitored catch by 100 to create a “first estimate” of the size of the population for each species for which we had adequate information.
We also inadvertently discovered that one species, wandering seabream (Acanthopagrus vagus), changed sex during its life cycle. We tagged some fish during a spawning run and what had been an obvious male was recovered, later and larger, as a functioning female. This was exciting, new information and it is now clear, after much further research, that in this family (the Sparidae), which includes various species of porgies, sea breams, sheepsheads, etc., many species are sequential hermaphrodites – changing sex, either from male to female or female to male during their life cycles. This, in turn, had important implications when drawing up fishery management rules as the last thing you want is to focus all fishing pressure on the large egg-laying individuals.
As a result of this and other similar studies, new legislation was brought out that was often species specific. Slow growing species might have a zero bag limit as they were unable to sustain extra, man induced, fishing mortality. Species that required some protection were given a low daily bag limit while abundant, fast-growing species were given greater bag limits. One species, the spotted grunter (Pomadasys commersonni), matured at about 35 cm. and the size limit was made 40 cm. so that fish could only be legally killed after they had had at least one chance to spawn. Fish found to be highly territorial generally required more protection than migratory fish.
People fishing for recreation could be encouraged to release fish, while those fishing for food had to kill them, but could be guided away from immature or threatened species. In South Africa, Marine Protected areas are zoned for activities and, where angling is permitted, limits are tighter than outside reserves and some species, such as sharks, are simply “off limits”.
The results of good science and sensible management should be an “optimal” situation where the wishes and needs of humans are balanced with the requirements of the environment and species like fish. Sadly, all too often and because politicians are involved, decisions are made to “over protect” fish, to appeal to some voters, or to “over exploit” to appeal to others. Rarely is it that truly objective decisions can be made and, when obvious species like game and birds are involved, a bad decision can be recognised and possibly changed. When fish are involved, however, it usually takes a collapse of stock before anyone registers that there is a serious problem.
Fish “mark and recapture” that informs wise fishery management can result in wins for the environment, fish and fishers, but we need to know about and have confidence in, the tools used. All too often, however, decisions are made on economic, social, ethical or political grounds and sound fisheries science is sidelined. Once a fisheries collapse has happened scientists and managers are expected to repair the damage, but a manager’s true worth is in helping to avoid the tragedy of fish stock collapse and working towards optimal fisheries management.
Next time you go out fishing, you might be requested to participate in an activity similar to those described above. I hope this blog helped you understand how important it is to accurately fill and submit catch cards, return or report on tags found on the fish you’ve caught, and of course follow all rules and regulations. Even though they may seem obscure and irrelevant on the surface, they are usually the result of hard work and have a solid scientific foundation. And all this activity has only one goal: preservation of that, which we all love – fish and fishing opportunities.
