A major aspect of the presentation was based on the fact that that the cod populations off Canada have not recovered despite years of essentially no fishing effort.
Dr Rothschild suspects that we should look causes other than "overfishing" for species biomass fluctuations.
He demonstrated that stocks have fluctuated dramatically over centuries and that predator prey relations do not explain everything because sometimes the fluctuations in predator and prey stocks are correlated and sometimes not.
He presented a hypothesis for the Canada cod example based on ice melt fluctuations in the Labrador Sea. Measurements indicate that the cod off Canada recently are putting on weight about half as fast per year as healthy cod. They are starving.
Read the entire blog at Cape Ann Online.