The Use Of Recruitment Time-Series Structure And Environmental Information In Medium-Term Stock Projections

No abstracts are to be cited without prior reference to the author.

Foremost amongst the competing aims for fisheries management is the maintenance of fish stocks for the forseeable future. To this end, it is imperative that managers are equipped with indicators of the expected level and variability of future population levels over the medium-term (typically, a five- to ten-year) time-scale, and that these indicators are sufficiently reliable, realistic and pertinent to the regulatory framework in which the managers operate. We extend the simulation approach currently employed within ICES stock assessment working groups by including characterisations of the time-series structure of residuals to fitted stock-recruitment models. The effect of the imposition of different hypothesised future environmental regimes is also investigated. North Sea cod (Gadus morhua L.) is presented as a germane and timely case study. We use the probability of the spawning stock biomass falling below the precautionary level of biomass, Bpa, as a diagnostic statistic to monitor projected performance. The relevance and utility of these new models for fisheries management is discussed, together with potential implications.