SETTING CATCH LEVELS
The stock assessment team works to provide the information and advice needed to make appropriate decisions about catch limits for different fish stocks. This work is done in conjunction with fisheries scientists and stakeholders from other research organisations.
New Zealand manages most fish stocks for Maximum Sustainable Yield (MSY). This means finding the delicate balance between taking what we’d like now, and leaving enough fish in the water to grow and breed for the future.
Ideally, we need to know what proportion of each fish stock is being caught each year. Knowing how quickly different species grow and reproduce, and how long they live, helps us work out sustainable catch levels. This requires careful monitoring of stocks, to ensure that catch levels are sustainable.
Commercial fishers must report their catches to the Ministry of Fisheries. This information can be used to work out trends in catch rates, and in some cases gives an idea of abundance. When there are more fish around, people usually find it easier to catch the same amount of fish from one year to the next. When there are fewer fish, it is usually harder to catch that same amount. However, this catch/effort information is not always enough, and in some fisheries it is misleading.
So in most important fisheries, we also gather information about length and age of fish caught. Some of this comes from Ministry of Fisheries’ observers on board fishing vessels; some is gathered by the industry’s own data collection programmes.
Combined, all this information on catch/effort, and size and age of catch will often tell us how sustainable a particular catch level is.
Where even more detailed information is needed, this can be collected through surveys by research or fishing vessels, or by tagging studies. However, these methods tend to be used only in the more valuable commercial fisheries.
Where we have little information, it is hard to gauge how close a fish stock is to our target level. In these cases, the government is obliged to act cautiously, and set the catch at a safe level.
Sometimes, when we have little information the government may arrange to raise commercial catch levels slightly for a time, if quota owners agree to gather extra catch/effort data. Once this is analysed, the government decides whether to keep catches at the new level, increase them further, or reduce them.
Recreational fishers sometimes want different things from a fishery than commercial fishers. In particular, they often want to be able to catch bigger fish more easily. This may mean reducing catches, so that more fish can grow bigger. However, lowering catch limits simply for the sake of catching bigger fish might not always be what commercial fishers want.
When catch levels need adjusting, the government seeks advice from Ministry of Fisheries’ scientists and managers, as well as from fisheries scientists from other research organisations, commercial and non-commercial fishers, environmental interests, and the wider public.
Fisheries management in New Zealand is not perfect. Some of our fish stocks have been over-fished.
However we do have major, ongoing programmes to research and monitor most of our important species. These include hake, hoki, ling, orange roughy, deep sea (oreo) dories, paua, rock lobsters, snapper, and southern blue whiting. We are now working to increase our knowledge of inshore and pelagic fisheries.
As stock assessment is expensive work, and research funds are limited, the stock assessment team continually works to get the best value from the available resources.