Blue Grenadier


Latin name: Macruronus novaezelandiae


Common names: Cod, Hoki

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Wild Caught

Region:
Commonwealth waters

Key Facts

  • Blue grenadier are caught using trawls in a Commonwealth managed fishery in Australia. Fisheries scientists have assessed that the stock caught in Australia is healthy.
  • Some of the area of seabed covered by the fishery has been mapped, and trawling grounds overlap with high-risk habitats, including areas of sensitive corals and sponges.
  • Historical high impacts on fragile marine habitats have been addressed through the closure of some trawling areas.
  • The fishery catches some threatened species such as Australian fur seals, shortfin mako sharks and seabirds, although industry has been proactive in trying to reduce mortalities of these vulnerable species.
  • All trawl vessels now must have seabird management plans in place to reduce seabird deaths, although the effectiveness of new measures will become clear in coming years.
  • The fishery discards up to half of its catch. The ecological impacts of this discarding have not been fully quantified.

More information

  • Commonwealth Southern and Eastern Scalefish and Shark Fishery (Commonwealth Trawl Sector) (1,312t in 2016-17)

Blue grenadier is caught in a trawl fishery managed by the Commonwealth Government. Fisheries scientists have assessed that the stock caught in Australia is healthy.

Blue grenadier are caught using otter trawls. Some of the area where fishing occurs has been well mapped in order to identify the distribution of sensitive sea floor species. Trawling sometimes takes place on areas of seafloor that support sponges, hard corals and bryozoans (small invertebrates that form colonies similar to coral reefs), but it is unclear how much trawling activity is resulting in damage to habitats and associated species. Some areas of marine habitat are protected in marine parks and through other spatial closures. It is likely the fishery has had a high impact on the marine environment in the past, but spatial closures and reductions in the amount of fishing over the past two decades has reduced that impact.

Protected species caught in this fishery include Australian fur seals, seabirds (including albatross and shearwaters) and shortfin mako sharks. Inconsistencies between logbook reporting and independent observers have been a problem in the past, and the fishing industry has been addressing these inconsistencies through training schemes.

There is some independent monitoring of the fishery that catches blue grenadier. While reporting of endangered wildlife deaths has improved in recent years, a comparison between observer recorded deaths and fishery logbook records is needed in order to provide confidence in reporting.

Seal Excluder Devices (SEDs), which act as escape hatches for seals that enter trawl nets, are mandatory. All trawl boats must have a seabird management plan in place to guide how each boat aims to reduce interactions with seabirds while actively fishing. Many of the solutions to seabird interactions have been fishing industry-led innovations. Initial evidence seems to indicate that some innovations could reduce the impact of fishing on endangered seabirds, however these have only recently been applied to fishing vessels and their effectiveness remains unquantified at present.

Blue grenadier is caught alongside unwanted fish that are then discarded. The amount of fish discarded has not been quantified, but it has been estimated that around half of the weight of the total catch in the otter trawl fishery may be discarded, with many of these fish dying during the process. The cumulative ecosystem impacts of discarding fish have not yet been quantified.

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Wild Caught

Region:
New Zealand

Key Facts

  • Stocks of blue grenadier are healthy in NZ, but threatened species bycatch and habitat damage are key concerns.
  • Catches of seabirds (including albatross, shearwaters and petrels) increased to the highest in a decade in 2014-15. Salvin’s and white-capped albatross are being caught at levels that could cause further population declines. Use of mitigation devices that reduce seabird interactions are in place, although it is unclear if devices are proving successful.
  • Trawling is conducted in areas that are not well mapped. Trawlers catch sensitive bottom-dwelling species that have a long recovery time, such as hard corals and sea fans.

More information

  • New Zealand Hoki Fishery (136,719t caught in 2015-16; 9,994t imported into Australia in 2016)

Blue grenadier is managed as two separate stocks in New Zealand fisheries. The Hoki fishery has recovered from historic overfishing, and stocks have been stable above sustainable levels for several years.

There are significant concerns over threatened species bycatch and habitat damage in this fishery. The New Zealand blue grenadier fishery catches a number of endangered seabird species, including white-capped, Buller’s and Salvin’s albatross, petrels and shearwaters. Risk assessments have identified that Salvin’s albatross is at risk of further population decline and white-capped albatross are in decline as a result of fishing activities.Seabird bycatch has not declined over the last decade, with recorded seabird captures in 2014-15 the highest in that period. Use of mitigation devices that reduce seabird interactions are in place; bycatch of seabirds has declined from 2015, but continues to be unacceptably high and likely resulting in the ongoing decline of threatened and protected seabirds.

In addition to seabirds, the fishery also captures seven species of deepwater sharks (known as dogfish). The biology of these species are poorly known, but are potentially vulnerable to overfishing due to their slow growth rates and low reproductive output.

Blue grenadier is trawled both on and above the seafloor over a large area of NZ’s oceans. Seabed mapping of the trawled area is limited, but sensitive seafloor-dwelling species (corals and sea fans) have been identified in both mapped areas and in trawl nets, which means that fishing activity is directly threatening these long-lived and sensitive species. There are few areas protected within hoki trawl depths, although Marine Protected Area Network planning is underway in NZ, which should protect sensitive marine habitat.