King Crab Fishery
Surveying the potential of a King Crab fishery
Fisherman Tony Muollo from Deep Blue Seafoods has teamed up with research scientist Reyn Naylor at NIWA to gather more information about King Crabs with a view to seeing if there is a long term viable and sustainable fishery.
The king crabs, Lithodidae, are some of the largest marine crustaceans. They comprise a small group of around 100 species. These species are largely deepwater and more than 60 of them occur in the Pacific Ocean.
King crabs are characterised by their spikes and large size. Some found in New Zealand waters grow as large as 1.2 metres across the legs. King crabs are related to the much smaller hermit crab. They have an excellent sense of smell and can detect food on the sea floor from quite a distance.
Strangely, all king crabs are right clawed (handed). They use one claw for cutting and the other for crushing. Their claws are very powerful and can give a strong nip.
The lifespan of New Zealand king crabs is not yet known, but many species overseas take four to five years to reach maturity and may live for more than ten years.
King crabs taste delicious and are of great commercial value in the Northern Hemisphere. Exploratory fishing for king crabs is currently being undertaken in New Zealand waters.
The king crab has been made famous as “the world’s deadliest catch” by a popular television documentary series about the Alaskan fishery, which targets a similar species to those in New Zealand.
At present they are caught only in small numbers around New Zealand as trawl by-catch. Although the total allowable commercial catch is 90 tonnes, two and a half tonnes were caught in 2009-10 and under one tonne the previous year. The crabs could fetch US$60 (NZ$80) a kilogram in restaurants, which puts them up near lobster in terms of value.
What the research is about is estimating the fishery and then working out how to safely land them, keep them alive and get them to market.
Tony Muollo’s family have been fishing off the coast of Wellington for close to 100 years. They run crayfishing boats and supply crays and wetfish into NZ and international markets.
In the early 1980’s Tony and Carlo Muollo were involved in New Zealand’s fledgling Orange Roughy fishery, specifically fishing the areas off the east coast of the north island down to Kaikoura. It was during these early days that they first noticed the presence of the New Zealand king crab at various locations. The initial specimens were discarded or brought home as curiosities, however, the areas these crabs were caught in were noted for future reference.
Deep Blue Seafoods NZ Ltd starting fishing for king crab to determine if
they could be caught in pots. After an initial setting of approximately six pots in various locations it was determined that these crabs could be caught using pots, but in order to get around the vast amount of gear that had to be set to get a group of individual pots to such an extreme depth, the fishing method had to be modified.
The crabs were held live in crayfish tanks and then cooked to determine if the meat content and taste were satisfactory. Samples of the crab and cooked meat were sent to a few prospective buyers and positive feedback was received from all.
In 2011-12, Deep Blue Seafoods increased the number of pots deployed to 20 and used the “long-lining method”. The crabs caught were distributed live locally. The largest demand was from the Asian community, predominantly in the Auckland area.
Development and management of a sustainable fishery requires assessment of stock status, which involves collating data and information on the species (i.e. stock structure, abundance and productivity) and the fishery (i.e. trends in catch (over space and time), catch-per-unit-effort, catch-at-size (or age) and gear selectivity).
NIWA scientist Reyn Naylor says the state of knowledge about the New Zealand king crab is sparse, largely due to the conservative management quotas and minimal fishery development for this deepwater (1,000 m) species.
Reyn says that in the first phase of a developing fishery it is important to establish whether the fishery is commercially viable. To assess the commercial viability of the king crab fishery in KIC 2, a temporary increase in catch allocation was required and Deep Blue Seafoods successfully applied to the Ministry for Primary Industries (MPI) for a special permit to catch 50 t of king crabs in excess of the TACC in KIC 2 (approved 15th of July 2013).
The application for the special permit outlined research that would be undertaken by Deep Blue Seafoods and NIWA to monitor and assess the fishery as it develops.
The first objective of the research programme was to conduct a review and summarise existing information on the New Zealand king crab that will be relevant to stock assessment and management of the developing fishery.
Gathering information about the crabs is hard because they are so deep (1000m).
To survey the king crab population that Deep Blue is fishing they have set up underwater housing for three cameras on one of the crab pots. The cameras have associated lights and are set to start recording from the time they reach the sea bed and then take short bursts of footage over the next 48 hours.
Reyn says deepwater camera systems have been successfully used to survey marine populations inaccessible by other means and may allow the estimation of a relationship between catch and density. Camera systems have been used to investigate the abundance of deep sea red crabs in the northern United States and king crabs on the Antarctic Peninsula .
Photographic surveys have several advantages over other methods used to estimate abundance. They are non-extractive and do not have the biases associated with potting. Reyn believes they are also likely to provide much more accurate estimates of density than other methods.
The crabs are also being tagged to investigate movement and growth. He says the choice of tag type can be complicated by the fact that crabs moult (shed their shells as they grow) but they have come up with a T-bar tag that seems to stay with the crab.