Dr Victor Luca, Scientist
Published in the Beacon 28-Oct-20
The views I have expressed here are solely my own and do not express the views or opinions of any organization I am associated with.
Since the arrival of Tangata Whenua up to the present day, our part of the world has always depended on fishing. But when will the music stop and the party end?
Myself and my family have been fishing the coast off our town for half a century now and I have seen at first hand the dwindling of fish stocks. The lifestyle and living of many in our area to some extent has always depended on the abundance of marine life off our coast. So it is natural to ask if we are treating this once bountiful fishery as we ought.
According to Fisheries New Zealand, snapper (Chrysophrys auratus) mature in three to four years when they are 20 to 28 cm long. To reach the current legal limit of 35 cm will obviously take more than five years. Snapper can live for over 60 years and grow up to 105 cm in length. They release numerous batches of eggs throughout spring and summer. Snapper is our major fishery by far with snapper accounting for more than 70% of all finfish harvested.
In the good old days we used to catch heaps of snapper off Ohope. The photo (Figure 1) is of one of our snapper catches dating back to about 1973. That’s me on the left, brother Enrico with the goofy hat on the right, and Gino at the back. There are several hundred kilograms of snapper in the photo and they were caught in a short time. It was not so unusual back in the day to come back with this much fish in a single short expedition. There were no legal limits for recreational fishermen back then. The size of the boat imposed a hard physical limit. You could only bring home what you could fit on the boat. In those days we didn’t even have reliable depth sounders like we have now and so finding fish was a matter of pot luck.
Figure 1. The good old days of fishing off Ohope. Circa 1973.
Toward the end of the eighties I do not remember ever being able to make these types of catches any longer and I challenge anyone to argue otherwise.
The observations I have made over a half a century are obviously qualitative. Many readers of this column that have been fishing our waters for as long as I have will doubtless make their own observations. All I know is that we used to catch heaps and that we no longer catch what we used to by any stretch. It just could not be sustained.
NZ Fisheries, which is part of the Ministry of Primary Industries (MPI) together with the National Institute of Water and Atmosphere Research (NIWA) are in charge of quantifying fish stocks and monitoring the sustainability of all 642 or so fish stocks in NZ waters. These folk undertake a huge amount of scientific work involving monitoring the fishery over time and analyzing data statistically to come up with estimates of fish numbers that they consider consistence and credible. These are not easy measurements to make and the data have significant uncertainty attached to them.
Data on the amount of snapper biomass in thousands of tons over time are shown in Figure 2. The reader can see that between about 1970 and 1985 the amount of snapper biomass (the fish stocks) fell off a cliff. To protect the fishers the Quota Management System (QMS) was introduced in 1986. Recreational fishing of snapper accounts for about 36% of the current quota.
The data bears out my qualitative observations that fish stocks have dwindled strongly since the seventies. The data show that there has possibly been something of a modest resurgence in snapper biomass since the introduction of the QMS. But the upswing in the nineties was weak and the margins of uncertainty are generous (shaded area). The data indicates that the snapper stock is only just above the so-called soft limit of 20%. This means that the stock is 20% of what it would be if it were not fished at all. Currently, commercial fishermen are taking right up to the allowable quote.
Meanwhile, another favorite species, the Tarakihi, is in a bit of trouble. The latest stock assessment for Tarakihi indicates that the stock is at 17% of unfished levels. In other words it has fallen below the soft limit as determined by the Harvest Strategy Standard.
New Zealand has 98 species (or species groups) divided into 642 separate fish stocks under the QMS.
Figure 2. NIWA data on fish stocks over time. https://niwa.co.nz/fisheries/snapper-stock-status.
The SNA 1 stock extends over a large area of the north-eastern coast from North Cape to Cape Runaway in the Bay of Plenty.
The number of fish at any given time will depend on their numbers, their reproduction rate, their death rate and the rate at which we take fish away through commercial and recreational fishing.
So far I have only looked at some of these factors and only for snapper which is probably the most important and valuable fishery in our area (SNA1). In recent years the total commercial catch of snapper has been around 7,000 tonnes with 70% of this catch coming from the SNA 1 area that includes our waters. Recreational fishing is also an important component of the total catch in SNA 1 and has been estimated to be about 30% of the total catch. The bag limit has been reduced and the minimum legal size has been increased for recreational fishers since the first introduction of the QMS.
Now let’s focus on fishing activities starting with recreational. NZ Marine reports a yearly compilation of the numbers of boat trailers registered in different regions of NZ. These data are shown in Figure 3. In 2015 there were about 170,000 boat trailers registered in NZ. We are adding an average of about 8,000 new boat trailer registrations throughout NZ per year. This suggests that we presently have 210,000 boat trailers registered in the country. If our district is representative, then we could expect about four trailer boats for every 100 of us. On that basis I estimate that in the Whakatāne District there are well over 1000 trailer boats.
As can be seen from Figure 3, the number of new boats being registered every year has been steadily increasing from about 5,000 in 2010 to just over 9,000 in 2019. That is, the rate of boat addition has almost doubled in 10 years.
Figure 3. New boat trailer registration trends by region. Source: NZ Marine Industry Association News, Autumn 2020 issue.
Given the increase in recreational boat numbers it would not surprise me if in the next few years NIWA and MPI revise their numbers and report further declines in fish stocks and especially as regards our most important fish stock, snapper. The next thing that will happen is a reduction in the quota from the present value of seven to five such as is the case in Australia. Remember that when the QMS was first introduced in 1986 to arrest the slide, the bag limit for snapper was 30, and the Minimum Legal Size (MLS) was 25 cm. Today, the bag limit is seven and MLS 35 cm respectively.
So far, scientific assessment of fish stocks by NIWA and MPI suggests that only 27 fish stocks of the 169 that are monitored have “sustainability concerns”. I believe that given the uncertainties inherent in the methodology used to assess the stocks, and the dominance of optimism, we will find more of these stocks in trouble sometime soon, especially the most important.
Given that our society is obsessed with growth - population growth & economic growth – and that the Earth’s resources are finite, I simply do not believe that this situation can be sustained. We can’t keep exploiting resources faster than nature can replenish them.