|Zearaja nasutus (rough skate), Dipturus innominatus (smooth skate)|
|manumanu, pakaurua, uku, waewae, whai (Maori), barndoor skate (New Zealand), suei, gangiei (Japan), gaori (Korea)|
All skates caught in New Zealand are a worst choice seafood and should be avoided. There are no recommended alternatives.
Skates are very closely related to sharks and are members of the cartilaginous fishes group (they have no bones). They are very distinctive, with flattened, wing-like bodies, and occur all around New Zealand from coastal waters to depths of about 200m. There are two species of skate commonly caught in our commercial fisheries: rough skate and smooth. The latter is more common in deeper waters, living longer and growing larger. Smooth skates are much larger than rough skates and are also known as barndoor skates because of their size. Both species are more common around the South Island. They are caught as a bycatch by bottom trawl and on longline across a number of fisheries in multiple management areas, each as a separate quota management species with different quota areas. The largest quota area for both species is the lower half of the South Island including the Chatham Islands (QMA 3). This area accounts for more landings than all other areas combined.
Both skates are primarily caught as bycatch in bottom trawl fisheries. The limited research on skates and absence of basic biological information on each skate species, the unknown sustainability of recent catch levels in some regions (e.g. QMA 3 Chatham Islands) or the total quota area, the lack of a quantitative stock assessment and detailed management plan are of concern. Also of concern are the impacts on deepwater habitats as a result of bottom trawling, and the associated bycatch of marine mammals, seabirds and non-target fish in fisheries where skates are caught as bycatch. While there is no operational plan for skates, in 2013 a revised New Zealand National Plan of Action for the Conservation and Management of Sharks was developed. This included a requirement that fins and bodies must be returned from sea together from 1 October 2014. However, there are no specific conservation actions for skates, nor is there any difference in its management from the status quo. In the initial risk assessment on all chondricthyans (Ford et al, 2015), rough skates are ranked first and smooth skates second most at risk.
Not certified under any scheme.
Exports of around $600,000 in 2008 to Asia and Europe, especially France and Italy. Total shark, ray and skates exports in 2015 was $31.33 million, of which only $373,000 was shark fins, mainly (95%) exported to Singapore. New Zealand is amongst the top 20 global exporters of shark product.
No regional or fishing method difference.
|Annual catch limit:||A total quota of 1,986 tonnes for rough skate and 849 tonnes for smooth skates was set in 2003-04.|
|Recorded catch:||Reported landings of 1,605 tonnes of rough skate and 617 tonnes of smooth skate in 2014-15.|
|Stock trends:||Unknown, but West Coast trawl survey biomass indices declined substantially since 1991 for smooth skate. It also showed a decline in rough skates from 2000 but has since increased marginally.|
|The Ministry of Primary Industries assessment plenary report includes:|| “No estimates of current and reference biomass are available.”
For rough skates: “it is Unknown if recent catch levels or the TACC will cause their populations to decline.”
For smooth skates: “SSK 7 relative biomass estimates from West Coast South Island trawl surveys revealed a strong decline between 1997 and 2009. Since then however estimates have increased with each survey and the 2015 estimate is the highest in the time series. For all other skate QMAs it is Unknown if recent catch levels or the TACC will cause skate populations to decline.” (MPI 2016, p1239 and 1248).
|Distribution:||Both of these endemic species occur all around New Zealand. Rough skate is more common in coastal waters while smooth skate is usually found in deeper waters, both extending to 200m water depth.|
|Maximum age (years):|
|Age at sexual maturity:|
|Ability to recover:||Low|
|Fishing method(s):||Trawling and on lines. Most of the catch is caught as bycatch of inshore bottom trawlers including flatfish (31%), red cod (22%) and barracouta (5%) fisheries. Skates are also caught as bycatch in a range of deepwater bottom trawl fisheries including hoki (10%) and squid (5%). Some are also caught in the ling bottom longline fishery.|
|Habitat damage:||There is considerable damage to seafloor communities when caught by bottom trawl or midwater trawl which touches the bottom. Impacts include habitat modification, loss of biodiversity, loss of benthic productivity and modification of important breeding and juvenile fish habitat|
|Habitat of particular significance:||hasn’t been defined in New Zealand.|
|Bycatch:||As a bycatch of other fisheries, skates are associated with the captures of non-target fish. Inshore fisheries of red cod, flatfish and barracouta catch nearly 60% of these skates. Bycatch in the red cod fishery includes terakihi, stargazer, and red gurnard. Deepwater trawl bycatch species include vulnerable deepwater sharks and other non-target and target fish.|
|Ecological effects:||The combined effects of destroying seafloor habitats and non-target fish bycatch can have considerable ecological implications.|
As a bycatch of other fisheries, skates are associated with the captures of non-target fish, seabirds and marine mammals.
Inshore trawl: Inshore trawl fisheries have an estimated seabird bycatch of 4370 seabirds (this includes cryptic mortality of birds that strike the trawl warps and are not recovered in the nets). Species reported include white-capped albatross, Salvin’s albatross and white-chinned petrels. The flatfish fishery has an estimated 928 annual seabird mortalities, including cryptic mortality. Fur seal captures have also been estimated in the inshore trawl fisheries at about 20 per year. In deepwater, protected species bycatch varies depending on the deepwater fishery (see, for example, hoki).
Hoki trawl: It is estimated that 192 fur seals are captured in the hoki fishery (5-year average). Based on the recent catch spread of hoki the main captures occur in the Cook Strait (54%), off West Coast of the South Island (24%), off east coast of the South Island and Chatham Rise (15%). The hoki fishery catches about half of the estimated fur seals caught by trawling. The sub-Antarctic and Snares Shelf hoki fishery has a low capture rate for nationally critical New Zealand sea lions of about one a year. The trawl fishery also captures about 1420 seabirds a year (5-year average): main species are Salvin’s albatross, southern Buller’s albatross, white-capped albatross, sooty shearwater, white-chinned petrel, and cape petrels. Protected coral species are also reported caught in hoki tows in most quota areas. The corals caught include gorgonian, hydrocorals, black corals (Antipatharia) and stony corals (Scleractinia) – which includes reef-like, tree-like, and solitary small corals.Other bycatch species include vulnerable deepwater sharks (e.g. shovelnose dogfish, seal shark and Baxter’s dogfish). These low productivity species also include threatened basking sharks (observed at one per year, but could be higher), deepsea skates and some other elasmobranchs.
|Management component:||The two species are managed and assessed as separate quota species. Stock structure and movement around the EEZ for both skates is unknown.|
|Quota Management Species:||Yes, since 2003.|
|Management plan:||There is no inshore plan or deepwater plan for skates.|
|Stock assessment:||No quantitative stock assessments.|
|Research:||Research has been limited on both skates and neither has had quantitative assessment undertaken on any stock.|
|Observer coverage:||Coverage is 23% in the target hoki fishery, 52% in squid; 8% in barracouta, and 38% in jack mackerel. The middle depth coverage is unlikely to be spatially or temporally representative of the fishing effort.|