Maximum Sustainable Yield (MSY) Proxies for Data-Limited Stocks for Key Stone Species and Species Sensitive to the Impacts of Fishing

Many of the stocks which are caught by the Irish commercial fishing fleets are considered to be data-limited or are not assessed at all. These include a number of key stone species (like sprat, gurnards, saithe, pollack, ling) and species sensitive to the impacts of fishing (like rays and skates, john dory, brill and turbot). For these stocks, the fishing mortality is unknown and MSY reference points are not established. This lack of quantifiable targets is an impediment to the implementation of the Common Fisheries Policy (CFP) as well as the Marine Strategy Framework Directive (MSFD).

There are a number of reasons why stocks are considered to be data limited: in some cases the available data is truly limited (e.g. non-TAC species or small stocks for which the value of the landings is small compared to the cost of sampling). In other cases there may be a substantial amount of data available, but not in a form that allows traditional analytical assessments of the status of the stock.

Below are some example species covering a broad spectrum of characteristics:

Most of these species are caught in a mixed fishery. Some species cannot be aged and for others the value of the landings is too low to justify a sampling programme to support age-based assessments. Nevertheless, apart from catch data, some additional data exists for most of these stocks (e.g. commercial LPUE and survey data). The project will evaluate whether including these additional sources of data improves or actually deteriorates our understanding of the state of the stock, compared to the information that is available from the time series of landings or catches alone. For other stocks, that are almost data-rich but for which no appropriate assessment models exists, the project will develop assessment methods that make optimal use of the available data. Each data source will be assessed for bias and precision and the contribution it makes to the assessment model.

There are also a large number of stocks in the ICES area for which reliable analytical assessments exist and for which the state of the stock is well known (e.g. Celtic Sea haddock, Irish Sea Nephrops). These stocks can be used to simulate data-limited situations and evaluate the performance of data-limited assessment models. In addition to this, models will be tested with fully simulated fish stocks and fisheries.

Simulated fish stocks and fisheries will also be used for a cost-benefit analysis of including various sources of data. This will answer the question of when the cost of collecting additional data would offset the yield and conservation benefits. For example: how many years would it take for an ageing programme to be financially viable under a range of stock scenarios.

The overall aim of the project is to develop and test a range of assessment models and methods to establish MSY reference points (or proxy MSY reference points) across the spectrum of data-limited stocks.