The Kermadecs

Fish


Grey drummer. Photo Tom Hitchon.

The Kermadec region supports a unique mix of temperate, subtropical and tropical marine fish species. Many of these are at the northern or southern limits of their ranges, and many use the area as a migratory corridor between tropical waters and mainland New Zealand. The Kermadec Islands also act as stepping stones in dispersing the larvae of tropical and subtropical fishes southwards to northern New Zealand.

A total of about 150 fish species have been reported from the Kermadec region, but as only limited surveys have been undertaken this is likely to be only a tiny proportion of the total fish fauna. The fish fauna at depths greater than 600 m, which make up most of the Kermadec region, is virtually unknown.

Pelagic fish

The pelagic fish communities – living in the main water column in the open ocean – are dominated by large predatory sharks, tunas, billfishes and sea basses. Most are tropical or subtropical species that migrate southward towards mainland New Zealand as the water warms in summer and autumn.

The main shark species are blue shark, mako shark and thresher shark. Mako sharks tagged in New Zealand waters are frequently recaptured in the tropical South Pacific, suggesting regular seasonal migration. Swordfish, great white shark and, probably, tiger shark, whale shark, manta ray and spinetail devilray, migrate through the Kermadec region.

Tuna species also carry out seasonal migrations through the region. Southern bluefin tuna is probably near its northern range limit, whereas the cool-water porbeagle shark is near, or at, the northern limit of its range.

Demersal fish

Demersal – or bottom dwelling – fish communities are also dominated by large predatory fishes, particularly bass and bluenose. Hapuku and northern spiny dogfish are probably at the northern edge of their ranges. The Kermadec spiny dogfish, recently described from three Raoul Island specimens, is considered to be endemic. The Kermadec smooth dogfish, which also occurs at Norfolk Island, appears to be undescribed. An undescribed species of giant stargazer is known from one specimen from the Kermadec Arc and may also be endemic. It is likely that additional endemic species will be discovered in the region during future surveys.

Tropical and subtropical fish

Many tropical or subtropical fishes are at the southern end of their ranges, including moray eels such as Anarchias supremus, which is endemic to the Kermadecs, along with yellow-fronted wrasse, scaly gurnard and ruby snapper. The Kermadec populations of convict grouper and Galápagos shark may be among the last remaining unfished populations of these species worldwide.

Threatened species

Eight fish species that occur in the region are included on the IUCN Red List of Threatened Species, two ranked as Critically Endangered and six as Vulnerable. However, many ray-finned fishes have not yet been evaluated, so the number of globally threatened species here may be higher than the current number suggests.

Harrisson’s dogfish, ranked as Critically Endangered, is known mainly from the eastern coast of Australia, where the population declined by 99% in 20 years as a result of trawl fishing[1]. It has recently been recorded from the Kermadec Ridge[2]. Southern bluefin tuna, also ranked as Critically Endangered, has declined by 92% worldwide since industrial fishing for the species started in 1952[3]. As a result, the Southern Bluefin Tuna Commission cut the permitted global catch level by 20% in 2006.

Six Vulnerable marine fish species are found in the Kermadec region. The great white shark which  has been protected under the New Zealand Wildlife Act 1953 since 2007; basking shark ; whale shark, the world’s largest marine fish – which ranges through warm temperate waters to New Zealand; the Oceanic whitetip shark; giant grouper, the largest reef-dwelling fish in the world; and bigeye tuna, which among the tuna species most threatened by overfishing worldwide.

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[1] Graham et al. 2001

[2] Duffy 2007

[3] Washington Post, 11 November 2007

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