Linking the performance of a data-limited empirical catch rule to life-history traits

Abstract

Worldwide, the majorities of fish stocks are data-limited and lack fully quantitative stock assessments. Within ICES, such data-limited stocks are currently managed by setting total allowable catch without the use of target reference points. To ensure that such advice is precautionary, we used management strategy evaluation to evaluate an empirical rule that bases catch advice on recent catches, information from a biomass survey index, catch length frequencies, and MSY reference point proxies. Twenty-nine fish stocks were simulated covering a wide range of life histories. The performance of the rule varied substantially between stocks, and the risk of breaching limit reference points was inversely correlated to the von Bertalanffy growth parameter k. Stocks with k>0.32 year−1 had a high probability of stock collapse. A time series cluster analysis revealed four types of dynamics, i.e. groups with similar terminal spawning stock biomass (collapsed, BMSY, 2BMSY, 3BMSY). It was shown that a single generic catch rule cannot be applied across all life histories, and management should instead be linked to life-history traits, and in particular, the nature of the time series of stock metrics. The lessons learnt can help future work to shape scientific research into data-limited fisheries management and to ensure that fisheries are MSY compliant and precautionary.

Implementing the precautionary approach into fisheries management: Making the case for probability-based harvest control rules

“…Thorson et al 2014) and as assumed in almost all MSEs (e.g. Carruthers et al 2014; Fischer et al 2020; Wiedenmann et al 2017), the results confirm findings of previous studies that for stocks with strongly fluctuating populations size, fishing at F MSY is neither precautionary nor does it result in the highest yield (e.g. Lande et al 2001).…”

Adapting Simple Index-Based Catch Rules for Data-Limited Stocks to Short-Lived Fish Stocks’ Characteristics

“…Birthdate was assumed on 1st January, which implies that age 0 group only lasts for 6 months in the population, becoming afterward age 1. The operating model for each type of stock was based on their life-history parameters (Jardim et al, 2015;Kell et al, 2017;Fischer et al, 2020). Growth was based on the von Bertalanffy growth model and lengths were converted to weight-at-age using a length-weight model.…”

“…Generic harvest control rules are usually evaluated for generic stocks (Geromont and Butterworth, 2014;Carruthers et al, 2016) or for specific species (Jardim et al, 2015;Fischer et al, 2020). Often, different species representing contrasting life-traits are selected (Carruthers et al, 2014;Wetzel and Punt, 2015;Walsh et al, 2018).…”

“…For Carruthers et al (2014) butterfish proved to be the most challenging stock due to its short life-span and highly variable recruitment. In a recent paper Fischer et al (2020) evaluated the performance of the empirical harvest control rule for ICES category 3 stocks for 29 stocks with contrasting life-history parameters. They concluded that the rule performed worse for the more productive stocks (growth parameter of the von Bertalanffy model, k, larger than 0.32 year −1 ).…”

“…Additionally, we evaluate the inclusion of a biomass safeguard level in the rules. We consider two types of short-lived small pelagic fish, anchovy-like and sprat/sardine-like, which are simulated based on their life history characteristics (Jardim et al, 2015;Fischer et al, 2020) under different exploitation levels. Finally, we test the sensitivity of the results to the precision of the biomass index and to the productivity of the stock and the variability of the recruitment, by changing the steepness and the process error of the stock-recruitment model, respectively.…”