Fishing: Snapper recovery not that simple

It's snapper spawning season.

Fish heavy with roe are coming into the inner areas of the Hauraki Gulf, Waitemata and other harbours and close-in off the west coast beaches.

On the Auckland and Northland east coast it's easy to find schools of fish and when they rise slightly off the bottom, it's a sign they are feeding. The bite-time sometimes remains short and they will go on-and-off the bite at various times for unknown reasons. Berley is a must.

The fish being caught around Auckland are almost universally in the 1kg to 2kg range, 37cm to 45cm in length, fat and in good condition.

These fish will be aged from eight years to 15 years, says fisheries scientist Bruce Hartill of the National Institute of Water and Atmospheric Research.

Niwa has been conducting boat ramp and aerial surveys of the recreational catch for the several years to determine the size of the amateur take. The east coast surveys finish this weekend and the focus will then be on the west coast.

Different methods are required given the predominance of kite and electric conduit fishing off the long black sand beaches plus the impact of the weather (the offshore easterly wind always encourages major effort on that coast).

The snapper fishery on the west coast, area SNA8, is accepted to be under threat. So when easterlies blew in recent weeks and trailer boats launched in numbers, only to find pair trawlers working the spawning schools, there was much debate: should those fish not be left to spawn and would not a closed season during spawning mean faster recovery of the fishery?

It's not that simple, says Ministry of Fisheries scientist Dave Allen. The main impact on snapper growth to adulthood is environmental: the water temperature needs to be constant and around 18C or higher, there must be plenty of plankton, and the presence and number of predators can have a major impact.

"One hundred million eggs as against 120 million is nothing," Allen said. "The key thing is how many eggs survive. Most mortality occurs in the first days after hatching when the fish are 2mm in size. At 2cm, they are floating in plankton schools for possibly a month before graduating to juvenile stage and are also extremely vulnerable.

"It doesn't matter when you take the fish, it's the amount you take. If there was a problem with taking spawning fish we would see a problem with recruitment [to adult stage] but what we see is a wide variation in recruitment, so other factors are at work."

The west coast snapper are the fastest-growing around New Zealand, reaching the legal size of 27cm within three years, probably due to the safe havens of the big harbours plus the abundant food those harbours produce. Bay of Plenty snapper grow second-fastest to reach legal size in four years. Hauraki Gulf fish take an average five to six years but as many as nine.

The variation is due to the variety of habitats off the east coast, and genetics.

Among the schools of pan-size fish are some bigger brothers, says Eugyn de Bruyn of Sea Genie charters, whose customers have been cleaning up in the Rakino Channel and off Waiheke in the past week.

"Every second trip someone lands a fish in the 5kg to 6kg range," he said. "If you target them with whole strips of kahawai or butterflied mackerel you'll get some good hits."

John Moran has had success using flasher or dropper rigs with no sinker. Instead of lead on the loop at the bottom, Moran attaches another large hook with a heavy bait attached to give weight. It's heavy enough to allow casting away from the boat but instead of sitting in one spot on the bottom as it would with lead attached, it will drift across the bottom in the flow of the berley trail.

Some anglers have been doing well on the john dory, either targeting them with jigs or by putting down live baits on mid-water reefs. It seems there is an explosion in the dory population.

There are lots of kahawai in the Gulf, from 10cm up to ocean-going. They are feeding on anchovies and if surface-schooling will often chase but not hit pilchards and larger lures thrown at them.

The Manukau Harbour has been slow this week. There are schools of large trevally about but the snapper and gurnard fishing has been ordinary.