While catch levels overall can appear relatively stable, a number of species have undergone such regional declines that their fisheries have collapsed. Alfonsino fisheries off the Azores and Corner Rise seamounts in the 1970s by the former Soviet Union lasted only a few years, and a spawning location for blue ling in the North Atlantic yielded 8000 t in one year before ceasing as catches dropped rapidly [80]. In the western North Atlantic, the three species of wolffish, and cusk, have reported declines in stock size of over 90% within the time period of three generations, and 38% of deep-sea bottom fish species in that area could be ‘‘at-risk’’ based on the extent of population declines in surveys [29].
Yet off New Zealand, oreo fisheries have had relatively stable landings for an extended period, and current stock status for both major commercial species is estimated to be around 50% of unfished levels [36]. Hence, fisheries can be sustained where life history characteristics are known and appropriate management is applied to limit catches and/or effort levels.