Abstract
Growth of adult chokka squid Loligo reynaudii d’Orbigny was modelled using mantle length and age data derived from samples collected over two years (2003 and 2004) from a single, large cohort of mature and spawning squid. A total of 588 statoliths were examined (310 males, 278 females) from individuals of 71–425 mm mantle length (ML). The maximum size of chokka squid was 425 mm ML for males and 263 mm ML for females. The Francis Growth Model and Linear Growth model were selected for further analysis from six models considered. Males and females attain similar ages, although mantle length-based daily growth rates ranged from 0.75 to 1.02 (0.88 quantile _50) mm/day for males and 0.32–0.45 (0.38 quantile _50) mm/day for females, explaining the sexual dimorphism apparent in the sizes of individuals of this species.
Highlights
The chokka squid (Loligo reynaudii d’Orbigny, 1845) can be considered one of the most comprehensively studied squid species worldwide, relatively few data on growth rates are currently available
This study aimed at providing growth rates of the chokka squid with age estimates derived from statolith daily increment analyses
Separate Francis growth models fitted to size at age data for each sampling year (2003 and 2004) show that the growth of the squid sampled in 2003 appears to be faster than that of those sampled in 2004 (Fig. 5), and that males in both years grew faster in length with increasing age compared to females
Summary
The chokka squid (Loligo reynaudii d’Orbigny, 1845) can be considered one of the most comprehensively studied squid species worldwide, relatively few data on growth rates (absolute or relative) are currently available. Estimates of age and other important parameters such as growth rate, age-at-maturity and life span are crucial in the understanding of the population dynamics of marine organisms (Jackson 1990). Reviews of chokka biology (Sauer et al 2013, van der Vyver et al 2016, Lipiński et al 2016) and recent ageing study (Lipiński et al 2020) provide no estimates of chokka squid growth rates
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