An assessment by the Department of Fisheries and Oceans says mackerel are in the "critical zone" where serious harm is occurring and recovery is threatened by overfishing.

Adding to the uncertainty are changing environmental conditions in the Gulf of St. Lawrence where mackerel spawn.

The results may surprise recreational anglers who catch mackerel from wharves throughout Atlantic Canada, but DFO scientist Andrew Smith said those are small groups of fish schooling close to shore.

They do not represent an accurate picture of the overall stock, which has been declining for years, he said.

"We continue to have a very low biomass. We are in the critical zone. We have had two very low years of recruitments in Atlantic mackerel, the two lowest on record," Smith said in an interview from DFO's Maurice Lamontagne Institute in Mont-Joli, Que.