The second in a summer series from NIWA…
Kahawai are an iconic species for recreational fishers. They are fantastic fighters and are found in most coastal waters, harbours, and estuaries around New Zealand, in both the North Island and South Island.
Many New Zealanders will have memories of catching kahawai in the summer with their granddad, in a small boat, with a spinner lure just off the coast, surrounded by a flock of sea birds.
The Bay of Plenty is an ideal habitat for kahawai and has some of the best catch rates. Kahawai are New Zealand’s second most commonly caught recreational species after snapper. They are keen to take the bait.
Kahawai’s scientific name is Arripis trutta and they belong to the family Arripididae. They are noticeable in the water, with speckled grey-blue to blue-green upper bodies.
’They are a solid, powerful, streamlined fish,’ says NIWA fisheries scientist, Bruce Hartill. ’They swim in small groups, and in schools in excess of a million fish, often weighing in excess of 200 tonnes.’
Kahawai can cover vast distances quickly because of their speed. They are fast growing, and are a very reproductively productive species compared to snapper.
They eat other fish, but mainly live on krill. The average size of a kahawai is 40—50 cm and 1—2 kg in weight. Females grow larger (up to 60 cm in length), and can weigh up to 3 kg, often half a kilo heavier than males.
Kahawai become reproductively mature at about 40 cm, at about four years of age. They can live to be 26, but anything over 20 is considered old age.
Kahawai are usually aged using a method similar to how the age of a tree is determined. A thin cross section from the otolith, or ear bone, is made and the rings counted. The number of rings equals the age of the fish.
Fishing for kahawai
The recreational catch limit for kahawai is 20 fish. Kahawai were introduced into the Quota Management System in 2004. The commercial catch limit for the main fishery — between North Cape and East Cape — is 1075 tonnes, out of a national commercial limit of 2728.
The fish in the Hauraki Gulf during summer are usually much smaller and about two to three years of age.
The biggest kahawai ever caught was 79 cm. It was caught by a recreational fisher in the Waitangi Estuary, in Hawke Bay in August 1997.
Kahawai are an oily fish, have a thick fillet, and are delicious smoked. Fisherman tend to bleed the fish as soon as they catch it, otherwise it can have an oily taste.
Kahawai is an important traditional and customary food for MÄori, especially in the East Cape area. MÄori at the Motu River used to bury the fish for up to a year to preserve them.
MÄori used to fish for kahawai with flax nets that could be up to a couple of kilometres long, or with lures which had shiny paua inserts. Some MÄori have expressed concern over the state of their traditional fisheries for kahawai, especially around the river mouths in the eastern Bay of Plenty.
NIWA’s lead researcher for kahawai fisheries, Bruce Hartill, will have a team of interviewers approaching recreational fishers at 21 boat ramps between Maunganui and Ohope during weekends from January to April 2011. The information collected during these interviews is used to monitor changes in the size and age composition of the kahawai population, and the overall state of the fishery.
’It’s a voluntary survey; we interview on average 5000-6000 fishing parties during that period when most boats come in. Most people are really co-operative. NIWA staff will be measuring kahawai, getting head samples, sampling commercial set nets, and purse seines at the same time. We are aiming to measure 1500 kahawai for age and 4500 for length,’ says Hartill.
About Bruce Hartill:
Hartill joined NIWA in 1995. He has been studying recreational fisheries for most of that time. In 2005 Hartill estimated that the recreational catch of kahawai between North Cape and East Cape was 530 tonnes.