Fishing: Warm weather a good start for snapper eggs

By Geoff Thomas

There is a lot of egg laying going on at present in the waters around the North Island.

For this is the spawning season for snapper, and hopefully enough of the many millions of pinhead-sized eggs deposited into the water column will survive and produce fish which anglers can catch in about five years.

Scientists believe the annual ritual is sparked by water temperatures, and since the sea around our coast had been several degrees warmer than normal over the past winter the spawning should be well underway.

The Hauraki Gulf is the main spawning area for the fish which congregate in large schools in 20-30 metres of water between Bream Bay and the Firth of Thames. As each female deposits about two million eggs a male will contribute the milt which hopefully will mix with and fertilise the eggs. These will hatch in about 48 hours, and the half-millimetre long larvae carry a yolk sac which provides nourishment for the first 24 hours. After that they are on their own in a hazardous environment.

Many anglers argue that fishing should be restricted when snapper are spawning to ensure stocks can build up, but scientists maintain that it is not the harvesting of adult fish which affects population growth but the water conditions which the tiny snapper larvae encounter after they hatch. The most favourable conditions are stable spring weather and warm temperatures which produce a good supply of the phytoplankton the tiny snapper need to survive. In a cold stormy environment, such as that associated with the El Nino weather pattern between 1994 and 1997, survival of the larvae is not as good.

Last year saw a change to the reverse pattern of weather with the La Nina phenomenon bringing warm, wet northerly and easterly conditions and it appears to be continuing this summer.

The larval snapper join hatchlings of other species including crayfish, which float around in the water column and are eaten by other fish in huge numbers.

After about a month the survivors develop into miniature versions of the familiar snapper shape about 15mm long. But life is still perilous, and the tiny fish are snapped up in the millions, with an estimated one in a thousand from the original eggs surviving through the five to seven years it takes for a baby snapper to grow to the legal size of 27cm in the gulf.

The gulf's population of snapper is the main contributor to the stocks on the east coast of the North Island, north of East Cape. This region holds the largest snapper population in the country, and is called Snapper Area One by the Ministry of Fisheries, which estimates the annual recruitment to that population is eight to 10 million.

On the west coast the environment is richer and babies hatched in the Manukau and Kaipara Harbours can grow to the 25cm legal minimum length for anglers to catch in only three years.

At this time of year anglers may find a congregation of fish appearing as a pyramid shaped mark on the screen of an electronic fish finder.

They can experience some fast fishing as the snapper attack jigs or baits. It may be an aggressive reflex as a result of the spawning activity, or it may be that in crowded conditions the fish compete for food.

But it is important to kill no more fish than are wanted for the table, because if every female taken would have contributed an average of two million eggs and the survival rate is indeed one in a thousand, this represents 2,000 catchable fish in five years.