Stock assessment methods used for cephalopod fisheries

Abstract

Cephalopods are of increasing importance as a fishery resource and many species are taken in directed and bycatch fisheries around the world. Owing to the short life-cycles and variable growth rates of most cephalopods, stocks may be highly volatile, both highly susceptible to recruitment overfishing and, conversely, capable of rapid recovery.Many species have protracted spawning seasons so that multiple microcohorts may be present in the population at any one time.Many assessment methods have been applied to cephalopod stocks, including stock recruitment relationships (e.g. the Japanese Todarodes pacificus stock), recruitment indices (e.g. Saharan Bank cephalopod stocks), swept-area biomass estimates (e.g.Northwest Atlantic stocks of the squids Loligo pealei and Illex illecebrosus), production models (e.g, Saharan Bank cephalopod stocks), cohort analysis (e.g. Illex argentinus in the Falkland islands), yield-per-recruit models (e.g. Northwest Atlantic squid stocks), length-based cohort analysis (e.g. Dosidicus gigas in the Gulf of California), and depletion estimates of stock size (e.g. Illex argentinus in the Falkland islands).Despite the widespread application of assessment methods, few stocks are rigorously managed, and the best example of a regulated fishery is the Falkland islands squid fishery. In contrast, although a number of assessment methods are used in the Japanese Todarodes fishery, management activities arc designed to ensure harmonious operation of the industry rather than maintain stock size. Fisheries for Loligo forbesi and Loligo vulgaris in the Northeast Atlantic arc mainly based on by-catches, although there is some directed fishing, particularly artisanal jig fishing in coastal waters. There is currently no assessment and minimal management for these species, and available management options are constrained by the nature of the fishery and the generally poor quality of available data.

Use of acoustic telemetry for spatial management of southern calamary Sepioteuthis australis, a highly mobile inshore squid species

“…The short life cycle of cephalopods, often unpredictable biomass, and vulnerability to overfishing results in limited management options, constrained by the nature of the fisheries and poor quality of data (Pierce & Guerra 1994). In addition, although there is growing support for the use of closed areas or seasons in the management of squid fisheries (e.g.…”

You are what you eat: describing the foraging ecology of southern elephant seals (Mirounga leonina) using blubber fatty acids

“…Mirounga leonina is known to be an important consumer of squid Santos et al 2001;Hindell et al 2003), and many of the known squid species have rather small, but developing, fishing industries (Gonzalez et al 1997). Most cephalopods have short life cycles and rapid growth rates, so they may be highly susceptible to overfishing, but also capable of rapid recovery (Pierce & Guerra 1994). In comparison, many fishes that have been exploited in recent times are characteristically long-lived animals that recover poorly from exploitation (e.g.…”

Exploitation patterns of <i>Octopus vulgaris</i> in two Mediterranean areas

“…Despite these recent advances there is still much to be investigated in order to improve the quality and quantity of the information concerning all aspects of cephalopod studies, from biology to management of their fisheries (cf. Pierce and Guerra, 1994;Caddy, 1997).…”