Effects of shelter on the welfare of juvenile Amphioctopus fangsiao: Survival, growth, behavior and physiology

Abstract

Placing shelters in rearing containers is a method of environmental enrichment that can effectively improve the welfare of aquatic animals. However, a set of standard specifications for shelter use is still absent in the artificial culture of Amphioctopus fangsiao. The purpose of this study was to investigate whether shelter type significantly affects the survival, growth performance, behavior, cortisol level, and brain serotonergic system activity of juvenile A. fangsiao. Juveniles (weight 3.72 ± 0.56 g) were reared under different types of shelters for 3 weeks: no shelter (CT), PVC pipe (PP), shell (SH), and PVC corrugated plate (PC). Behavioral and physiological parameters were determined thereafter. In general, octopuses in PP treatment had the highest survival rate (83.3 ± 17.0%). The weight gain (53.40 ± 6.20%) and specific growth rate (2.03 ± 0.19% d−1) of CT octopuses were higher than those of octopuses from other treatments. CT octopuses exhibited the highest levels of aggressive behavior, cortisol, and brain serotonergic system activity, while PC octopuses showed the lowest levels of these stress-related behavioral and physiological indicators. The hepatosomatic index, coefficient of weight variation, and attachment rate did not differ significantly among treatments. Altogether, these results demonstrated for the first time that shelter type had a major impact on octopus survival, growth performance, behavioral phenotype (aggressive behavior), and stress-related physiological processes, and we suggest that using PVC pipes as shelters might be optimal for octopus rearing.