The Atlantic Canada snow crab (Chionoecetes opilio) fishery may have started out as a bycatch fishery over 60 years ago, but today it has become the second most valuable export fishery in Canada. In 2013, The Newfoundland and Labrador snow crab fishery had the honour of becoming the 200th fishery to receive Marine Stewardship Council (MSC) certification. Improving the catchability of snow crab, as for any fishery, has garnered significant interest, though can be challenging to achieve.
At the fourth International Marine Conservation Congress, PHD candidate Khanh Nguyen, who is based at Marine Institute, Memorial University in Newfoundland, described one way snow crab fisheries can increase catchability – and without spending vast amounts of money redesigning gear.
Mr Nguyen’s research has focused on exploiting the snow crab’s biology – specifically its ability to detect and react to lights. A number of marine species are known to be attracted to lights, with some commercial fisheries, such as squid jigging, using lights to lure their prey. Whereas some fisheries use relatively powerful lights, Mr Nguyen’s interest was in the use of low powered, coloured LED lights.
The first phase of the research took place in the laboratory. Focusing on the responses of legally sized male snow crabs (all females caught in this fishery must be returned to the ocean), Mr Nguyen presented the crabs with five different coloured LED lights - blue, green, red, purple, and white – and measured the crab’s movement responses. Whilst red and green LEDs elicited no statistically significant response, 75% of the crabs moved towards white and blue LEDs, whilst 85% moved away from purple LEDs.
Crab pots in Newfoundland, Canada. Credit Derek Keats/Flickr (CC BY 2.0)
The second phase of Mr Nguyen’s research was to take the LEDs out of the laboratory, to see how they performed at sea on inshore fishing vessels. Newfoundland and Labrador snow crab is primarily caught with smaller (under 20 meters) vessels, using baited conical mesh traps stringed together, with soak times typically ranging from 24 – 48 hours. To compare the effect of the low powered LEDs on Catch Per Unit Effort (CUPE), different coloured LEDs were attached to some traps, whilst others had no LEDs to act as a control. As in the laboratory, the snow crabs responded differently to the different lights.
For snow crab fishermen looking to increase their CPUE, the results were clear – white LEDs are the way to go. Compared to no LED light, simply adding a low powered white LED light produced a 77% increase in CPUE.
The improvement of snow crab catchability from LED lights has direct implications for the industry, whose expertise and assistance were central to the success of the field work component of the research. “Fishermen normally spend about 8 -9 trips catching their allocated quota”, Mr Nguyen explained. “Whilst catching with the lights, fishermen need about 5 trips”. The associated decrease in operational costs, such as reduced fuel requirements, could directly translate into improving the financial viability of the snow crab industry, Mr Nguyen added.
With the snow crab fishery providing essential employment in many small fishing communities dotted along the coastline of Newfoundland and Labrador, improvements to the viability of the fishery has benefits beyond the fishers themselves. Certainly it seems that adoption of Mr Nguyen’s research in the commercial Snow crab fishery will happen - he is already receiving calls from snow crab fishers keen to adopt the LED lights in the next fishing season.
This story appeared on The Fish Site.