Nondaily growth increments in the commercial species, Octopus berrima, and the importance of age validation

Abstract

Abstract Age data are crucial for understanding and managing target species in commercial and recreational fisheries. Octopus catches are increasing worldwide, yet ageing methods are still in their infancy. Octopus age is estimated by counting growth increments in stylets and beaks. These increments have been validated as daily in some species or assumed to be daily in other species. Here, we conducted an age validation study on both the stylets and beaks of a commercial octopus species (Octopus berrima). Subsequently, we compared and assessed the readability of growth increments in beaks and stylets of wild-caught O. berrima. We found that increment periodicity was nondaily for both structures, with increment periodicity also varying between structures (0.75 increments per day for stylets and 0.53 increments per day for beak). This study highlights the importance of validating increment periodicity for different octopus species and for both stylets and beaks to obtain accurate age and growth data. Without accurate age data, a species may be incorrectly managed with the potential for negative effects on the sustainability of wild populations.