Growth model selection for the jumbo squid Dosidicus gigas from the Gulf of California, Mexico

Abstract

We analyzed mantle length and age data of the whole ontogenic cycle of the jumbo squid Dosidicus gigas in the Gulf of California, Mexico, to describe its growth pattern. Several individual growth models that included asymptotic and non-asymptotic patterns were fitted to the data, and Akaike’s information criterion and multimodel inference were used to identify the model that best fit the data. The length-at-age data were divided into males and females (recruits and adults) for analysis separately and then combined to assess the overall growth pattern. The Schnute general model (ρ≠0, η≠0, where ρis the constant relative rate of the relative growth rate, ηis the incremental relative rate of the relative growth rate) was the function that best described the growth of females, males and both sexes of D. gigas together. For females, the Akaike difference and Akaike weight were 0 and 0.91, respectively; for males, the Akaike difference was also 0, but the Akaike weight was 0.39, showing that alternative growth models could explain the individual growth; these growth models were the Gompertz (L0, length at time zero), Gompertz (L∞, asymptotic length) and Schnute (ρ≠0, η = 0) models. We estimated the age and mantle length at which the growth rate changes for both sexes, estimating an age of 162.36 d (separately, 167.51 d for females and 158.98 d for males), and a length of 299.52mm for the growth inflection point (separately, 312.84 mm for females and 292.86 mm for males). Once D. gigas reaches this point, the species exhibits more gradual growth until reaching an asymptotic mantle length of 859.45 mm (for females, 904.80 mm, and for males, 828.49 mm). A comparison of the growth patterns of D. gigas reported in the Eastern Pacific indicated nonasymptotic growth of this species in the Humboldt Current and Costa Rica Dome; in contrast, asymptotic growth was identified for the western coast of Baja California and Gulf of California. The reason for this difference is unclear, and this issue will be a topic of future studies.