Detecting the presence of depensation in collapsed fisheries: The case of the Northern cod stock

- Classic models cannot describe the observed species' lack of recovery under moratoria.
- We provide a stochastic model to detect depensation in collapsed fisheries.
- Demographic uncertainty and depensation cause the lack of recovery of Northern cod.
- Reference points based on the assumption of compensation might be non-conservative.

Motivated by the evidence that many collapsed stocks have failed to recover despite the fact that fishing mortality has been reduced, or even when a moratorium is in effect, we develop a methodological approach using splines to analyze the stochastic population dynamics of fish stocks at low stock levels. Considering the aggregate Northern cod stock by way of illustration, we find that the species' lack of recovery, despite the moratorium which still remains in force, is consistent with the hypothesis of depensatory population dynamics at low population sizes, as opposed to the compensation estimated by the conventional regression methods used in classic bioeconomic models.