70 per cent decline in capelin not due to fishing, say scientists
Environmental factors more of an issue than commercial fishing, says DFO
Scientists with the federal Department of Fisheries and Oceans found a lot fewer capelin last year during their survey of the stock — a decline of 70 per cent from the last count, done in 2015.
Scientists blame late spawning for the population drop.
Once the capelin larvae hatch they need tiny copepods for food, and if they hatch after the copepod population spikes, then fewer larvae will survive.
Capelin are described a "lynchpin" species because a healthy population helps other types of fish. Cod and turbot eat them directly, and without lots of capelin those fish will eat commercially valuable crab and shrimp instead.
Last year about 20,000 tonnes of capelin were fished commercially, but scientists at DFO said fishing has little impact on the decline.
"We don't have evidence that the removal from the commercial fishery are driving it," said Fran Mowbray who led the research.
"It seems to be largely environmentally driven."
She said the capelin are only caught a few weeks before they spawn and die so it doesn't have a large effect on the availability of food for other species.
She said it does reduce the number of eggs laid but more eggs doesn't seem to lead to more fish, because a food source for the young fish is often the limiting factor.
A couple of bad years for larvae mean scientists expect stocks to be bad for the next couple years.
Fish kill lot more capelin than people do
Healthier cod and turbot populations are also bad news for capelin.
Mowbray says what humans fish every year is small compared to the amount eaten by fish, birds and whales.
She estimates about one million tonnes of capelin are eaten by fin fish alone every year.
Because the fish only live a few years before they spawn and die, the population size can have bigger swings than other types of fish.
Mowbray pointed out that capelin were at much lower levels in 2010 and the population rebounded.
DFO is unable to accurately estimate the total number of capelin in the water, which scientists call an "absolute abundance estimate," because it doesn't do a survey of the full area using sonar.
Other countries such as Iceland do acoustic surveys allowing them to estimate the full numbers.
Until recently DFO only had one researcher dedicated to capelin, but has hired two more people to improve the science.
As well, the capelin stock assessment will now happen every year instead of every two years.
- A previous version of this article said the capelin survey will now be done every year rather than every two years. This is incorrect. The capelin survey has always been done every year. It's the capelin stock assessment that will now be done every year rather than every two years.Mar 13, 2018 6:27 AM NT
- A previous version of this article said the last capelin survey was done in 2015. This is incorrect. The last survey was done in 2017.Mar 13, 2018 6:29 AM NT