Striped marlin are one of a range of large oceanic pelagic species caught by recreational and commercial fishers in New Zealand waters. Generally, striped marlin are most abundant in summer and autumn, and northern New Zealand has a long established recreational target fishery for striped marlin. The largest striped marlin caught on rod and reel all come from New Zealand waters. The International Game Fish Association keeps records and 16 of the 22 striped marlin line class world records are held by anglers in New Zealand, including all the heaviest fish caught on line from 6 kg to 60 kg breaking strain.

Funded by the Ministry of Fisheries
Researchers Blue Water Marine Research
Richard Keller Kopf

Recreational fishing
A sport fishery developed in New Zealand targeting marlin and sharks in the 1920s. International tourists brought heavy tackle and new fishing methods that proved highly successful. The quality of the fishery was praised by best selling author of the time Zane Gray in his book ‘Tales of the Angler’s Eldorado, New Zealand’ and others. Fishing clubs were established, and they weighed and recorded each fish landed. Charter boats were responsible for most of the catch as they had the specialist tackle and experience. Today, many private boats from 5 to 30 m in length participate in the fishery, and there are about 80 charter boats that target striped marlin seasonally.

Gamefish club records provide an almost complete record of striped marlin catch throughout the history of the fishery. Since 1990, 60% of the recreational catch has been tagged and released with only estimated weights available for these fish. The expansion of the areas fished and the number of private fishing vessels targeting marlin has increased along with the proportion of the catch not recorded in club records in recent years.

Striped marlin have been tagged by recreational fishers and a few commercial fishers in New Zealand since 1975. The number of fish tagged and released has increased dramatically since the N.Z. Big Game Fishing Council introduced a voluntary minimum weight of 90 kg for landed striped marlin in 1988. There are about 3 or 4 tagged striped marlin recaptured per year and these have been distributed widely throughout northern New Zealand and the sub-tropical southwest Pacific Ocean, but not beyond.

Commercial fishing
Surface longlining is the main commercial method that catches striped marlin. The Japanese longline fleet moved into the South Pacific in the early 1950s and fishing effort expanded rapidly. Commercial reporting of surface longline landings on New Zealand forms became mandatory in 1980. Since October 1987, commercial fishers have been required to release all marlin (dead or alive), and since that time the number of marlin caught on commercial vessels has not been reliably captured on tuna longline catch and effort reports (TLCERs). Scientific observers record all fish caught and released, but historically observer coverage has been poor in the areas and season when striped marlin are caught. In the wider Pacific, striped marlin is mainly a bycatch, though occasionally a target species, for surface longline vessels and the annual catch is estimated at 15,000 t across the whole Pacific.

New Zealand commercial catches of striped marlin since 1980 peaked in the 1981–82 fishing year (October to September) with 2,843 fish, mainly taken by Japanese surface longline vessels. Catch declined with fishing effort and the moratorium on billfish during the late 1980s and early 1990s. The New Zealand domestic fleet developed in the mid to late 1990s and reported the highest striped marlin bycatch in 1998–99 with 1613 fish (Table 1).

National striped marlin catch
The New Zealand Big Game Fishing Council (NZBGFC) collates recreational striped marlin catch totals for all affiliated clubs. This provides an almost complete estimate of national recreational marlin catch each fishing season (July to June). The peak recreational catch was reported in 1998–99 with 2364 fish, 65% of which were tagged and released (Table 1). The lowest recorded catch since 1980 was in 1986–87 season when 226 fish were landed and 2 tagged. (Table 1).

Table1: Commercial landings and discards (number of fish) of striped marlin in the New Zealand EEZ reported by fishing nation, and recreational landings and number of fish tagged, by fishing year.

Over the last 15 years the New Zealand landed catch has been estimated at between 40 and 95 tonnes with a mean of 62 t per year (Table 2). All this catch comes from recreational fishing club catch records, which list most but not all landings. Commercial discards and fish tagged and released by recreational fishers are estimated to range between 20 and 270 t over the last 15 years with a mean of 115 t. This also is likely to be an underestimate of the total caught, but the mortality associated with these releases is likely to be less than this.

Table 2: Reported total New Zealand landings (commercial and recreational) (t) and commercial landings from the southwest Pacific Ocean (t) of striped marlin from 1991 to 2005.

Longline catch since 1952 around northern New Zealand
Surface longline catch and effort has also been summarised for all fleets between 1952 and 2001 from a subset of Ocean Fisheries Programme data for an area that encompass northern New Zealand (30 to 40 ^oS and 170 ^oE to 175 ^oW) plus the Kermadec Islands (25 to 30 ^oS and 180 to 175 ^oW). This area was selected because it encompassed the main areas that striped marlin were likely to be caught in New Zealand waters. However, this area also includes the waters of East Cape that have been fished extensively for southern bluefin tuna during winter, when striped marlin would not be a likely component of catch. It also includes an area just outside the New Zealand EEZ to the north, where distant water longline vessels are known to operate and catch striped marlin.

Striped marlin landings by surface longline in this “box” around northern New Zealand ranges from 500 to 3,000 fish per year from 1956 until the first full year of the billfish moratorium in 1988 (mean 1,493 fish sd 1,017 fish for that period). An exceptionally high catch of 5,143 striped marlin was reported in 1971.

The reported annual commercial landings of striped marlin for the northern New Zealand box peaked at 400 tonnes (5,143 fish) in 1971 and averaged 115 tonnes per year (sd 80.3 t) between 1956 and 1987. Very few blue or black marlin are reported from this area although they are present in modest numbers in the recreational catch. The large increase in the catch of broadbill swordfish landed since 1980 probably has more to do with changes in retention and marketability of small fish, and targeting by some fishers, rather than changes in availability.