Shelter Preferences of Cultured Marron (Cherax cainii Austin, 2002) Exposed to Two Light Intensities Under Laboratory Conditions

Shelter availability is a critical factor influencing the behaviour, welfare, and productivity of crayfish in aquaculture systems. This study examined the preference for four types of shelters among 0+ marron (Cherax cainii) juveniles under two light intensities: 1200 lux and 20 lux. These four distinct shelters were a sheet composed of radially rounded mesh (A), vertically layered mesh (B), PVC pipe (C), and a two-layered flat sheet on top of two PVC pipes (D). Two sets of experiments, one using a single juvenile and the second using two (paired) juvenile marron in separate tanks under laboratory conditions, were conducted across a triplicated design at the Curtin Aquatic Research Laboratory. Three variables, including shelter preference (%), total resident time (seconds) in shelters, and total search time (seconds) before residing in shelters, were determined through video surveillance. The results demonstrated a consistent selection for the rounded shelter, accounting for 47% and 59% by an individual marron, and 58% and 60% by two marron under 1200 and 20 lux, respectively. Light intensity was a significant factor influencing the total search time, as darker conditions reduced the duration spent by the marron searching for shelters. Agonistic interactions were observed when the second marron was present in the tanks, resulting in a decrease in the marron’s overall search time during their daily activity patterns. However, the total resident time remained unchanged after the marron occupied their preferred shelters, even when social interactions occurred.