Crawling in crustaceans: Scientists study link between warmer ocean, booming lobster population
DFO scientists find warmer lab waters mean larger population, but don't know if that's also true in the wild
Federal scientists are exploring connections between a warming Atlantic ocean and record lobster landings off southwestern Nova Scotia and in the Bay of Fundy.
Adam Cook, lead lobster research scientist for the Department of Fisheries and Oceans, said those locations have seen the greatest temperature increases too.
He said there's clearly a relationship between temperatures and population but other factors are also involved in the remarkable rise in lobster landings, including a decrease in ground fish predators over the same period.
In the lab, warmer temps produce more eggs
With a decade-long rise in temperatures, including record highs in 2012 and 2016, researchers at DFO laboratories in Nova Scotia and New Brunswick are now studying the impact of warmer temperatures on egg production, egg quality and moult timing.
"We are seeing often increased egg-development rates, perhaps increased moulting that allows animals to grow faster," said Cook.
Economic analysis from the federal government reveals the economic clout of the lobster fishery in southwestern Nova Scotia. Preliminary estimates for 2015-16 show landings nearing 40,000 tonnes and worth more than $500 million.
For lobster fishing area 34 — Shelburne to Digby — landing estimates show 28,467 tonnes, worth $417 million. Landings by weight there have nearly tripled in the past 20 years. In area 33 — Halifax to Shelburne — estimates suggest 9,800 tonnes were landed, worth $147 million.
Over the past 20 years the increase is even more dramatic, with landings up five-fold.
Why science is cool on drawing conclusions
In the lab, researchers are noting increases in lobster production with higher temperatures. But Cook said experiments in the lab do not replicate conditions in the wild.
"They have the opportunity to go out and choose what temperatures they live in," said Cook.
He said even in areas of higher temperatures, there are pockets of warmer water and colder water which can be relatively close together.
All signs remain positive for Nova Scotia's lobster population. The most recent 2016 DFO stock assessment for offshore lobster populations in Browns Bank and Georges Bank was presented last week.
"Things are great out there. We're seeing high abundance levels," said Cook.
The 2016 stock assessment for inshore areas in southwestern Nova Scotia lacks catch information, but the environmental survey data is positive.
"We are also seeing some of the highest levels of landings. Our trawl surveys are still showing high levels."
Cook said what's happening is unusual. In recent decades, the lobster populations have hit a plateau, and then grown again. This growth spurt doesn't seem likely to end in the next two or three years.