Funded by the Ministry of Fisheries and NZ Big Game Fishing Council

Researchers Blue Water Marine Research

Tag and release has become an integral part of sport fishing in many parts of the world. The New Zealand programme started from relatively humble beginnings in 1975. Currently about 2000 fish a year have small number plastic streamer attached each year prior to release. The project relies on the cooperation of anglers and a few commercial fishers that release fish, the Ministry of Fisheries who fund data management and reporting, the New Zealand Big Game Fishing Council who purchase and distribute the tags and Blue Water Marine Research who are contracted to manage the database. The project focuses on billfish, sharks and yellowtail kingfish with the aim of gathering information on growth rates, movement patterns and distribution of these large predatory fish.

STRIPED MARLIN

There were 963 striped marlin reported as tagged and released inside New Zealand fisheries waters in the 2006–07 season, an increase on the previous season (922) and about the average of the last 10 years (980). A further 675 striped marlin were reported as landed in gamefish club records. So about 59% of recreationally caught striped marlin were tagged and released in 2006–07. The number of striped marlin landed by fishers and not recorded in 2006–07 is not known, but is thought to be relatively small.

No striped marlin were recaptured during 2006–07. This is the first season since 1992 that no recaptures were made. The recapture rate overall is about 0.5%. Tag shedding seems to be a problem with striped marlin, with few tags remaining in fish for more than a year.

A marlin recaptured last season was at liberty for 374 days just 45 nautical miles from where it was tagged, off Whangaroa. It was recaptured near North Cape in April 2006. The fishes weight was estimated both times, at 95 kg on release, and at 130 kg on recapture. The recapture represented a relatively rare event, however, since it was only the fourth striped marlin in this programme to be recaptured the following season. Three of these recaptures have been in New Zealand and one in early January east of Byron Bay, Australia.

Four tagged striped marlin were recaptured in 2004-05, equalling the total from the previous season. A striped marlin tagged on 9 February 2005 at Cape Brett. Upon recapture off Stevenson Island, Northland on 26 March 2005 after 45 days at liberty, it was 34 nautical miles from its tagging location and weighed 103 kg. The second recaptured fish was tagged off Mayor Island, Bay of Plenty, on 25 February 2005 and also carried NZ Marine Research Foundation satellite tags, which showed it headed northeast for a while and then northwest. The satellite tag (PAT) popped off 200 nautical miles north of North Cape after 22 days on the fish. A tuna longline vessel recaptured this marlin just 23 nautical miles northeast of North Cape on 7 April 2005. This fish had been at liberty for 41 days and was caught 240 n. mile from its release point. However, the satellite track from satellite tag locations indicates this fish travelled at least 600 nautical miles in that time.

The third striped marlin was tagged at the King Bank on 21 March 2005 after 20 minutes on the line. It was caught on a lure from the vessel Primetime and was estimated to weigh 130 kg. It was recaptured on 15 April 2005 also on King Bank. Therefore this fish had been at liberty for 25 days and has stayed in or returned to the area in which it was released.

The fourth striped marlin recaptured this season was caught by a recreational angler on the charter vessel Pursuit at the King Bank, on 26 April 2005. This fish had been tagged 96 days earlier after 30 minutes on the line, off Flat Island, Whangaroa. The fish was estimated at 90 kg on release and had travelled a minimum distance of 100 nautical miles. It was retagged and released with an estimated weight of 120 kg. The tag head was close to coming out of the fish and the skipper was not sure if the tag would have stayed in place much longer.

Overall the recapture rate is 0.5 % and most striped marlin (84%) have been recaptured within 5 months of release.

Figure 1. Long distance striped marlin recaptures. Release locations are around northern New Zealand, recaptures outside New Zealand waters, with days at liberty next to recaptured locations.

Blue marlin recapture
A tagged 150 kg blue marlin was recaptured on 17 October 2005 west of Vanuatu after 743 days at liberty and 240nm from its tagging location. It was originally caught and tagged within the Coral Sea on 5 October 2003 from the New Zealand vessel Striker. This was the sixth tagged blue marlin recaptured from the New Zealand programme. No blue marlin recaptures were reported during the 2004–05 season and the overall recapture rate of blue marlin is now 0.8% for this programme. Compared with the earlier years of the programme, blue marlin have been tagged in greater numbers over the last four seasons, mainly by anglers in the Kingdom of Tonga. Of the 91 blue marlin tagged in the 2004–05 season, 29 were tagged in New Zealand between January and May. The fish tagged in Tonga were generally estimated at 150 kg or less, while in New Zealand they were estimated at 150 kg or more in 2003–04.

New Zealand billfish tags with nylon anchor
The Ministry of Fisheries, through the Gamefish Tagging Programme, has purchased tags with the nylon tag head for use on billfish in New Zealand. Most billfish programmes around the world now use these tags which have improved recapture rates in blue marlin. Worldwide the recapture rate for striped marlin is higher with the stainless steel dart tag, however there may be changes in the fishery over time that account of some of this difference.

Advantages of the new tag are that it has better holding power if applied correctly, the tag will lie flat against the side of the fish and muscle tissue can bond to it. Disadvantages of the plastic tags are that it is more expensive than the current tag, it requires a different applicator tip, it may not be suitable for shark species with tougher skin. The nylon tag head is held on with 24 kg nylon not stainless steel wire.

MAKO SHARKS
There were 150 mako sharks tagged in New Zealand fisheries waters during the 2006–07 season, which is 53% lower than the average number of makos tagged for the 10 previous seasons. According to NZBGFC records, 85% of all mako sharks caught by gamefish club members in 2006–07 were tagged and released. The number of makos released without being tagged is unknown.

Mako sharks are not generally a target species in northern New Zealand but are caught as a bycatch from vessels targeting billfish or tuna. In 2006–07nearly all makos were tagged in the northern half of the North Island. The catch was distributed fairly evenly between the west coast of the North Island, east Northland and the Bay of Plenty.

Most makos were tagged between January and June 2007 with a strong mode in February, when twice as many makos were tagged than in any other month. The size distribution of makos tagged in 2006–07 shows that most were estimated to be 90 kg or less. A few large makos between 200 and 320 kg were also tagged.

Gamefish tags last quite well in mako sharks. There have been numerous long distance and long duration recapture reports from the southwest Pacific. The longest distance recorded was about 3000 nautical miles from New Zealand to the Marquesas Islands and the longest confirmed duration for a mako has been 2384 days (6 years 6 months). Recaptures of makos outside New Zealand fisheries waters show clusters of recaptures around Fiji, New Caledonia, Queensland and New South Wales. To some extent this may reflect the distribution of fishing effort and the likelihood of reporting.

Two mako recaptures were reported during the 2005-06 season. The first was estimated to be 150kg upon release on 4 March 2005. It was recaptured 229 days later in Fiji on 19 October 2005, 1300 nautical miles away from its tagging location. The second mako was tagged on 11 January 2003 and estimated to weigh 140 kg by the skipper of Major Tom 2, and was recaptured 292 days later in the Cook Islands, 1240 nmiles away.

BLUE SHARKS
There were 156 blue sharks tagged in New Zealand fisheries waters during the 2006–07 season. This is the most tagged in the last 5 years. The average for the previous 10 years for this species is 222 per season. Seventy five blue sharks were tagged off Otago Heads, predominantly in. There were two other notable areas, Kaikoura (32) and Castle Point (17) where blue sharks were tagged. The estimated weight of tagged blue sharks in the 2006–07 had a mode at 30 kg and there were some larger sharks also tagged, unlike the previous season.

In the 2006–07 fishing season two blue sharks were recaptured close to their release locations on the west coast of the North Island. A blue shark was recaptured on 20 July 2004 by a longliner in Rarotonga, 840 nmiles from its tagging location at the Banks Penninsula. T had been at liberty for 145 days.

YELLOWFIN TUNA
A 40 kg yellowfin tagged at North Cape in February 2006 was recaptured by a tuna longliner near the Barrier Bank (30 nautical miles north east of Great Barrier) on 18 April 2007. It weighed 48 kg gilled and gutted (~55kg green weight) and had been at liberty for 424 days and was 155 nautical miles from the release location.

Previously a yellowfin tuna was recaptured southeast of Sydney in August 2005 1000 nmiles from its tagging location. This 15 kg fish had been tagged 501 days earlier in March 2003 on the Middlesex Bank, near the Three Kings Islands. Also a yellowfin tagged and released from Major Tom II in March 2003 off the Bay of Islands was recaptured in August 2004 by a Japanese tuna longliner in the mid Tasman Sea, in a similar area to three other yellowfin recaptures. This fish was at liberty for 507 days (1 year 5 months) and was 600 nautical miles from its release point. It was estimated at 25 kg on release and weighed 33 kg (134 cm) on recapture. A second yellowfin tagged from Major Tom II in February 2003, was recaptured in the Fiji area by a tuna longline vessel some time in 2004 (date not supplied). It had moved about 900 nautical miles north. Overall, the recapture rate for yellowfin tuna is 1.1% for this programme.

Figure 2. Yellowfin tuna tag recaptures with days at liberty next to recapture locations.

POSTAL ADDRESS
The New Zealand gamefish tagging programme is funded by the Ministry of Fisheries and the NZ Big Game Fishing Council. All tag cards and recapture information should be handed into your local gamefish club or posted to the Ministry of Fisheries in Auckland. Tag cards issues over five years ago may have an old address. All clubs should use this new address for the tagging programme.

Gamefish Tagging
Ministry of Fisheries
PO Box 19747
Avondale
Auckland