Information on the size and age of yellowtail kingfish from North Cape to Cape Runaway is being collected to monitor the current state of the stock in northern New Zealand.

Recreational charter and private fishers are being asked to measure their catch and help collect otolith bones for aging.Targeted recreational fishing is the only method that is likely to catch a representative range of all adult kingfish sizes.

Funded by the Ministry of Fisheries
Researchers Blue Water Marine Research, NIWA

Objectives

1. Estimate the age structure of kingfish (Seriola lalandi ) populations in Northland and Hauraki Gulf combined, and Bay of Plenty
2. Calculate total mortality (Z) from the catch curve
3. To compare age structure of kingfish from East Northland/Hauraki Gulf with the age structure of kingfish from the Bay of Plenty
4. To use this new information to monitor the health of kingfish stocks.

Methods

We want to recruit 60 of the top kingfish skippers and fishers to accurately measure all the kingfish they catch over 75 cm. A sample of 1000 lengths is needed from each area from February to July 2010.

Kingfish heads will be collected across the full size range of fish. 250 pairs of otolith or balance bones for each region will be removed and examined under a high powered microscope to count annual growth rings. 

Lengths for all fish will be converted to age using an age-length key and plotted in a catch curve. The total mortality rate can be calculated from the shape of the curve.

Kingfish in Northland are genetically identical to those in the BOP but if the growth rates are different this indicates limited mixing and possibly a need to manage as separate sub-stocks.

Sampling kits

Selected fishers will receive:

• A kingfish sized measuring board
• Training and instruction sheet
• Recording sheet, labels, bags, pencils etc.
• Free gamefish tags for kingfish
• $10 handling fee for each head returned (with size and sex labelled)
• Courier bags for heads and information
• A free newsletter on kingfish research and management
• An entry to a Lucky Draw for a Duel Speedy light tackle fishing reel

Rationale

Yellowtail kingfish is a high value recreational species widely distributed in temperate southern hemisphere and temperate north Pacific waters.  Most of the IGFA world records for southern yellowtail are held by fish caught in New Zealand.  We have a world class fishery.

It is the Ministry’s job to manage and monitor fish stocks.  In 2004 kingfish was placed in the quota management system with a 20% reduction in commercial catch history.  The recreational size limit was increased from 65 to 75 cm fork length, also aimed at reducing catch 20% by weight.

A pilot project in 2003 in the Bay of Plenty showed that the stock could be aged and monitored with this type of project.  This is the first full scale monitoring project on kingfish which should get repeated every five years.

When currently have enough fishers participating and all our equipment deployed.