The body responsible for managing Atlantic bluefin tuna has decided not to suspend the fishery in response to concerns over dwindling stocks.
The International Commission for the Conservation of Atlantic Tunas (Iccat) instead decided to lower the annual catch quota by about one third.
Conservation groups said the decision would encourage illegal fishing.
Iccat scientists said recently that bluefin numbers were at about 15% of pre-industrial-fishing levels.
They also said that drastic limits on fishing now would facilitate the growth of a more profitable industry in years to come, as stocks became more plentiful.