Keeping tabs on giant tuna
The Ministry of Fisheries and gamefish charter vessel operators are monitoring the bluefin tuna fishery off the West Coast.
The giants of the tuna world - which can grow to 350 kilograms or more - are the subject of a three-pronged research effort to help New Zealand to make the best possible management decisions.
- Between 2007 and 2010, charter boat operators chasing bluefin off the West Coast over the winter voluntarily recorded the number and weight of fish their anglers caught and landed. The system complimented the New Zealand Cooperative Tagging programme. From 1 November 2010 mandatory catch reporting is in place and voluntary catch reporting of bluefin will no longer be encouraged.
- The New Zealand Cooperative Tagging Programme is a cooperative project between the Ministry of Fisheries, the New Zealand Sport Fishing Council and the most important constituent those anglers who tag and release gamefish. These data provide an estimate of the number of fish that are released alive by game fishers (see below). Recaptures provide information on movement, time at liberty, displacement rates, and growth rates. The programme encourages a conservation ethic that is particularly applicable to Pacific bluefin.
- Meanwhile scientists have been tracking the movements of some individual Pacific bluefin by satellite as they migrate vast distances around the Pacific. Researchers planted hi-tech tags on 23 fish over the winter of 2008. The devices can collect and store months of data on location, depth, water and body temperature before they pop off and rise to the surface to beam it to researchers. The Ministry of Fisheries is among the sponsors of this project.
For game fishers this is a large and powerful fish, and the chase and capture often a once in a lifetime achievement. But fish that are tagged and released confer the same bragging rights as landed fish and the fish may return and provide the same opportunity for other anglers.
Retaining fish can be wasteful and is often in quantities well in excess of the angler’s needs or ability to consume. Because the flesh of fish caught during the season when the recreational fishery occurs is of poor quality, it’s really only good for smoking.
So tagging and releasing is something the Ministry wants to encourage with the added bonus that recaptures will add to our knowledge. This programme ultimately depends on anglers sending in Gamefish Tag Reports to record the fish they tag and release.
Reporting catches reinforces amateur fishing charter vessel operators’ and Government interest in making a long term management commitment to bluefin tuna. These records are important for documenting New Zealand’s ability to monitor its bluefin fishery prior to more active international management controls. These assist in achieving an objective to develop a viable and sustainable world class game fishery for bluefin tuna in New Zealand waters.
Results to date
|
Pacific bluefin tuna |
Southern bluefin tuna |
|
|
|
|
2007 |
|
Landed |
Released |
Landed |
Released |
| Number |
44 |
87 |
35 |
20 |
| Kilograms |
11,361 |
22,464 |
4,025 |
2,171 |
|
2008 |
|
Landed |
Released |
Landed |
Released |
| Number |
59* |
145# |
3* |
0# |
| Kilograms |
16,845* |
36,162# |
400* |
0# |
|
2009 |
|
Landed |
Released |
Landed |
Released |
| Number |
17* |
42# |
1* |
0# |
| Kilograms |
4,913* |
11,264# |
130* |
0# |
|
2010 |
|
Landed |
Released |
Landed |
Released |
| Number |
13 |
17 |
2 |
0 |
| Kilograms |
1,683 |
4,250 |
250 |
0 |
* Landed data compiled from Voluntary Reporting Forms
# Released data compiled from Gamefish Tag Reports and is provisional
These data suggest a substantial decline since 2008 in the numbers of landed and released fish. Amateur fishing charter vessel operators surveyed dispute that this is due to a reduced availability of fish. Instead they note:
- the number of vessels and the number of trips have more than halved - due to the economic recession
- some charter vessel operators are said to have withheld from voluntary reporting their 2010 catches in protest at the imposition of mandatory reporting
|
Background
Meetings held in Auckland and Westport during August 2008 have set the scene to improve the monitoring of bluefin catches
Download report of meeting (PDF 83KB)
At West Port Charter boat operators agreed to furnish records of landed (retained fish) on forms to be circulated by the Ministry of Fisheries. The Ministry will estimate released fish from Gamefish Tag Reports.
Download 2008 letter to monitor bluefin catches (PDF 56KB)
This letter was sent to those charter operators planning to fish the West Coast bluefin tuna season during the winter of 2007 (also published in the September/October 2007 edition of New Zealand Professional Skipper magazine - the official journal of the maritime transport industry).
Download Pro-Skipper Letter 1 (PDF 38KB)
This article describes the differences between the bluefin species, how they breed and live and early results of the monitoring programme (also published in the November/December 2007 edition of New Zealand Professional Skipper magazine).
Download Pro-Skipper Letter 2 (PDF 101KB)
This article describes tagging studies on Pacific bluefin tuna and the nature of the New Zealand ‘stock’.
Download Pacific Bluefin Tuna Extract (PDF 59KB)
This article describes the management of Southern bluefin tuna in a New Zealand context.
Download Southern Bluefin Tuna Extract (PDF 42KB)