DFO Seminar: Why is northern cod biomass very low and Barents Sea cod biomass very high? The roles of scientific advice, management decisions and climate variability.
ABSTRACT:In the early 1980s, the northern (2J3KL) cod stock off southern Labrador and
eastern Newfoundland was productive and recovering from the severe overfishing of the
1960s-1970s, whereas the Barents Sea cod stock north of Norway and northwestern
Russia was declining to an all-time low. The two stocks were at similar levels of total
biomass at that time. By the late 1980s, management of both stocks was in crisis. For
northern cod, the crisis resulted from recognition of scientific overestimation of stock size,
whereas for Barents Sea cod, the crisis was ecological, stemming from a collapse of the
capelin stock. In the early 1990s, the northern cod stock collapsed, whereas the Barents
Sea cod stock rebounded strongly. Since the early 1990s, the northern cod stock has
experienced low productivity, whereas the Barents Sea stock has been highly productive,
despite fishery removals that were much too high during some years. In 2010, the northern
cod stock was well below its biomass limit reference point. Total catch was uncertain, but
perhaps about 4,000 t. In contrast, the Barents Sea cod stock was well above its
biomass limit reference point and fished at 610,000 t. (The Barents Sea cod quota was
increased to 703,000 t for 2011.) This talk will compare the dynamics of the two stocks.
Primary focus will be on (i) the extent to which management decisions and climate
variability influenced the divergence in stock trajectories during the early 1990s and (ii)
the contributions of exploitation, predators (seals), prey (capelin) and climate change to
the different levels of productivity since the mid-1990s.
Jan 30th, 2012