Temporary Allee effects among non-stationary recruitment dynamics in depleted gadid and flatfish populations

We investigated whether low-abundance recruitment dynamics can change in time between compensation and depensation, the latter implying the presence of the Allee effect. For this, we studied the stock-recruitment time series of 17 gadid and flatfish populations in the RAM Legacy Stock Assessment Database using a Bayesian change point model. The recruitment dynamics were represented with the sigmoidal Beverton-Holt and the Saila-Lorda stock-recruitment models, and the parameters of the models were allowed to shift at a priori unknown change points.

Methods
The stock-recruitment data were extracted from the RAM Legacy Stock Assessment Database. The data set contains the spawning stock biomass (SSB) and recruit time series of the studied populations.  

The S-R models were fitted to the data with the Bayesian online change point detection method (BOCPD), combined with simulation-based filtering. The data were divided into segments by calculating their most likely segmentation (MLS). The methods are described more in detail in the supplementary material of the article.