MSE testing of factors likely to have an effect on catch surplus calculations through impacting MSY estimates

This work deals with uncertainty on the estimation of MSY considering the most likely factors to affect the stocks subject to Fisheries Partnership Agreements. A Management Strategy Evaluation algoritm was used using three management procedures. The traditional assessment based MSY HCR with a Btrigger and Ftarget, a catch base HCR that keeps catch at the average levels of a specified period, and a survey HCR based on the comparison of the average survey observations on a specified period and historical quantiles. The scenarios simulated try to give insights about factors that could have an impact on the estimation of MSY and indirectly on catch surplus: underestimation of catches, quality of the abundance, lag between assessments, distinct assessment models and over-catch. The results show that all these factors have impact on the estimation of MSY. Catch mis-reporting was not well captured by this MSE. The link between misreporting and implementation error requires more work. Biased survey indices have a huge impact on the estimation of K and, to a smaller extend, r. In the case of underestimation these impacts are larger and result in an unrealistic TAC that may lead to stock collapse. Having assessments at intervals of 3 or 5 years result in delays responding to increases or decreases in biomass. Using a Fox model has the effect of considering the stock to be more productive at lower levels of biomass which results in a higher TAC and lower biomasses.