Emergency action for calculating stock size and reference points in case of massive data deficiency (39782)

The project is a timely response to the foreseeable consequences of the covid-19 pandemic on the assessment community’s ability to conduct the required assessments of key stocks, and the subsequent calculation of quantities used by managers.

The covid-19 pandemic must be expected to cause two things to occur that will severely impact the yearly assessment process:
a) Data sources which routinely are used in the assessment models will be missing or be incomplete. This could be the case for both data from the scientific surveys and from the fishing fleets.
b) The fishing pattern (and thereby the population development) will be different, because of lack of demand and thereby falling prices on landed fish.

It will therefore – already from next year 2021 – be necessary for the assessment models to be able to handle missing and incomplete data on a scale not seen before. This must be done in a statistically rigours way to limit the problem to simply having less information. Various ad hoc schemes (e.g. duplicating information from other years, or simply not using any data from 2020) will likely make the problem worse. Such approaches are problematic under normal circumstances, but even more so in 2021, because the stock development in 2020 must be expected to be different (due to b)).

The solution is to properly treat the missing observations as missing in the assessment model, which means assigning random effects and integrating over these. Current fisheries management depends on reference points in determining the status of a stock and, in turn, the exploitation opportunities. However, reference points are estimated from data through an assessment model. Therefore, reference point estimates are inherently uncertain.
Currently, this uncertainty is not accounted for in fisheries management. Another purpose of this project is to improve the current methods for estimating reference points as well as the subsequent advice and management by quantifying and accounting for this uncertainty.

The project will analyse and develop the methods and principles behind reference point estimation as well as their implementation in operational assessment models and multiannual plans through harvest control rules used, for instance, for stock rebuilding.  

Funding
The project is funded by the European Maritime and Fisheries Fund and the Danish Fisheries Agency. 

Research area: Marine Living Resources