Stock assessment and management of cephalopods: advances and challenges for short-lived fishery resources

Abstract

Cephalopods have become an important global food source, but their sustainable management is challenged by unique life history characteristics associated with short lifespans and semelparous reproduction, high natural mortality rates, rapid and often nonasymptotic growth, and complex population structures. Weak stock-recruitment relationships together with the time-consuming work required for age validation and high-volume annual age determinations make traditional age-based modelling impractical. We propose that the best method for cephalopod assessment involves innovative depletion models, fitted with in-season data on catch numbers and fishing effort, to produce realistic estimates of stock biomass. A “fast lane” assessment approach is suggested that includes high-frequency data collection for separate, in-season stock assessments of each cohort to ensure sustainable exploitation of these short-lived resources. However, most cephalopod fisheries are data-poor and/or lack the infrastructure and resources needed to apply depletion methods; therefore, we also present alternative assessment methods that have been recently applied worldwide. We also offer suggestions for further research on the remaining challenges of cephalopod stock assessment and management.

Incorporating evolutionary based tools in cephalopod fisheries management

“…Consequently, for a majority of commercially important invertebrates, accurate data on abundance, population structure and connectivity is lacking, and their stocks are neither effectively assessed nor managed (Anderson et al 2011;Eddy et al 2017). Cephalopods are a clear example of invertebrates whose stocks are often inadequately assessed or managed (Arkhipkin et al 2020), despite their global abundance and landings increasing since 1950s, peaking at 4.9 million tons in 2014, and declining to approx. 3.6 million tons in 2017 and 2018 (FAO 2020, Fig.…”

“…In this review we discuss the benefits of incorporating novel evolutionary genomic tools to inform stock assessment and management of cephalopod fisheries, with special consideration to some of their specific life history traits (Arkhipkin et al 2020) and unresolved complex interactions of environmental and fishery pressures with their population structure and dynamic. We further suggest that the common octopus (Octopus vulgaris Cuvier 1797) (Box 1) would be a suitable model for evolutionary-based cephalopod management.…”

“…However, other studies implied that the overexploitation of cephalopod stocks may already be underway in several regions (Anderson et al 2011;Rodhouse et al 2014;Meissa and Gascuel 2015;Sauer et al 2019). Maintaining the cephalopods fisheries at sustainable levels particularly grows in importance in the light of their high trophic positions, implying that their population collapse might have the ecosystemwide consequences (Arkhipkin et al 2020).…”

“…Patagonian longfin squid (Doryteuthis gahi) and Argentine shortfin squid (Illex argentinus) in the Falkland Islands area are among some of the prominent examples of regulated cephalopod fisheries (Payne et al 2006;Arkhipkin et al 2015). Their stock management relies on pre-recruit surveys and inseason depletion-based assessments to meet targeted spawning stock biomass (Agnew et al 2005;Arkhipkin et al 2020). However, this approach demands the use of special equipment for preseason assessments, and extensive daily data collection during season to appraise and forecast stock population dynamics (Rodhouse et al 2014;Arkhipkin et al 2020).…”

“…Their stock management relies on pre-recruit surveys and inseason depletion-based assessments to meet targeted spawning stock biomass (Agnew et al 2005;Arkhipkin et al 2020). However, this approach demands the use of special equipment for preseason assessments, and extensive daily data collection during season to appraise and forecast stock population dynamics (Rodhouse et al 2014;Arkhipkin et al 2020). For many other cephalopod stocks assessments are conducted within the scope of traditional age-based or stock-recruitment models, which rely on the estimates of spawning stock biomass, size-at-maturation, and fishing mortality.…”