Assessing the performance of ICES elasmobranch harvest control rules through Management Strategy Evaluation: the data-limited case of Raja clavata in the North Sea.

Jordan Moss

In 2012, ICES set out a tier-based system to define the Management Plan (MP) for a specific stock, based on the data available (ICES, 2012). Due to the distinctive life history (Holden, 1974 & 1977; Camhi et al., 1998) and the high number of data-limited stocks (ICES, 2019a), that characterise elasmobranchs in the North-East Atlantic, this paper aims to investigate if the current data-limited ICES MP is effective compared to feasible alternatives. This was done using the North Sea Raja clavata stock. A data-limited Management Strategy Evaluation (MSE) framework was used to simulate the stock under 34 MPs, this was tested under 2 recruitment models and 3 observational scenarios. Currently, an index of vulnerable abundance is used to calculate the Harvest Control Rule for the ICES MP, the MSE simulation conducted, suggested that by switching to an index of spawning abundance, the yields could be improved with minimal increase in conservation risk to the stock. A future alternative could be the MP based on a Delay-Difference model; however, this would require fine-tuning. Sensitivity analysis suggested error in the Index and the risk of hyperstability to the index were to areas to ensure the reliability of data in the future.