After what can only be described as a bumper autumn and winter season in the Hauraki Gulf and along the north-eastern coastline, our thoughts now turn to the mass influx of snapper to our fertile waters.
Huge schools of snapper will be moving from the more uniform temperature of the deep water off our coast, into the gulf and other prime spawning areas as the water temperature slowly increases. It is spawning time again.
The oceans of the world heat and cool more slowly than the land, so our ‘maritime season’ lags behind. I find it to be about a month or so later than traditional season timing.
There are other factors, too, that affect the water temperature and therefore the annual migration to prime spawning areas. Just look at the effect of the cold December and January we experienced on the inshore fishery this year. A huge number of snapper didn’t make the final push into the harbours and bays, preferring to stay in a more stable water temperature of the middle gulf and out off the coast in 40m-plus.
It is also believed that when we have a cooler ‘spawning season,’ snapper spawn more erratically, with poorer results than during a more stable and warmer season.
As spring progresses this year, so will the movement of snapper into the gulf and along the coast, normally becoming evident in September and October, with spawning peaking in December and January. Snapper are group spawners, and these large schools gather in the gulf, off estuaries and bays, to complete the spawning process, which is commonly believed to proceed once the water temperature rises to around 18°C.
When spawning takes place, the schools rise and fall in the warm water, releasing large numbers of eggs and sperm. There have been observations made of this process, including those of schools drifting about just below the surface, rolling over on their sides to release their gametes (a specialized sex cell that fuses with another). The whole school spawns at the same time, and being serial spawners, individual fish will do the ‘wild thing’ several times in one season.
It is a possible that much of this activity takes place at night. Sound familiar? Observations, however, have been rare, and much is still to be learnt about this process. Aquarium observations have in some cases shown the female followed by three or more males, nudging and fin-nipping each other, as she swims vertically to the surface, where the fish release eggs and sperm. On other occasions it was a one-on-one affair.
The eggs are spherical in shape and very small, about 1mm in diameter. They are externally fertilized and float near or on the surface for a day or two before hatching.
Spawning success is less related to the number of parent fish than to the conditions at spawning time and during the months following. Warm summer-to-autumn temperatures appear to allow greater survival of eggs, larvae and juveniles. After a series of warm years the fishable stock will increase, with a time lag of four to five years (the time from spawning to full recruitment as adults). After cool years the stock level will decline.
It is also believed that larvae and very young fish are presumably mid-water or bottom dwelling. None have been taken in surface plankton hauls over known spawning grounds.
At several months old, these infant fish are around 2cm in length and perfect miniatures of adult fish. All are female. After about a year they are only 10cm long, and it takes a few more years before they reach the stage where a sex change takes place, with about half becoming males.
Growth rates are measured by counting scale rings, with each ring showing a winter where growth almost stops, or by counting annual rings in the ear bones (otoliths). Our average school fish are 4 to 10 years old, with the larger specimens reaching 60 years old.
A growth rate indictor would be something like this: Growth: 1 year = 10cm; 2 years = 16cm; 3 years = 21cm; 4 years = 30cm; 5 years = 33cm (@ 0.5kg); 6 years = 35cm; then about 1cm per year.
Snapper are widely distributed, but the Hauraki Gulf has the highest concentrations of school fish and is therefore their main spawning ground. Being a pretty constant depth, providing a stable water temperature, having good food sources and being relatively sheltered, make it the perfect breeding ground and hatchery, as well as a great commercial and recreational fishery.
Over 30,000 tonnes of commercially caught snapper are landed annually, destined for the local market and export markets like China and Japan, where the fish is known as ‘tai,’ which means ‘good fortune’. Snapper is used in Japan as a celebratory meal and can be air-freighted to the dinner table within a few hours of being caught. Longline-caught fish are preferred for the export markets, but the current financial environment has led to the demise of many longliners, so seine and trawled fish dominate the markets now.
The Ministry of Fisheries tells us that more than 840 tonnes of snapper and 20 tonnes of kahawai were harvested by recreational fishers in the Hauraki Gulf over the 2003-2004 season, accounting for around 35-40% of New Zealand’s total recreational snapper catch.
It has been estimated that recreational fishers take about 3500 tonnes per year.
Recognising these fish is quite simple: dull-pink snapper for schooling fish caught far offshore above muddy ground; deep pink snapper found more closely inshore; and brown or dark red reef snapper which spend much of their lives on coastal reefs. We all recognise the ‘old moochers’ that have developed a hump on their head.
But what is the significance of us as recreational fishers catching these spawning fish? Let’s face it: they are prolific in the gulf and other spawning areas during the spring and summer months, and the word spreads like wildfire when it’s ‘going off’.
There is, of course, an increase in fishing pressure on the snapper population during this time, but there is also a much larger snapper population in the spawning areas, too. You could say this counter-balances the situation. The effect, however, of taking spawning fish out of the loop, is that there is going to be fewer fish spawning. No secret there.
Now comes the tricky bit. There are fewer large snapper around than there are school fish at this time, and the bulk of the spawning activity comes from these school fish. These are the fish (due to their large numbers) that provide the biggest contribution to the procreation of the species. They – again due to their large number – are the most frequently caught. Is this yet another counter-balance?
I see it like this: we, as anglers, have a set of rules laid out for us by the Ministry of Fisheries, based on science (complete or otherwise), sustainable yield and known biomass statistics. Commercial fishers are governed by similar rules in the Quota Management System to ensure that a species is not overfished. However, as recreational fishers we are not in a situation where we must catch our full quota to remain a viable enterprise. We can make some choices for ethical reasons or just so we can say we did our part to conserve the fishery. The old saying ‘limit your catch not catch your limit’ is ringing in my head, but as I say, the rules are in place, and I can understand that if a group or individual only fishes a few times a year, he/they may want to get value from a charter or simply a return for the petrol they put in their own boat by taking a limit bag. A far more serious threat comes in the form of black market fish selling, high-grading and, as seen on Coastwatch, blatant overfishing.
In all cases, remember the 1mm egg that, in 10 years, may have made it to your dinner plate. Fish responsibly and enjoy your sport.
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This article is reproduced with permission of
New Zealand Fishing News
Oct 2007 - by Damian Clayton
RE-PUBLISHING ELSEWHERE IS PROHIBITED |
