Shelter preferences of juvenile European lobster: mussel shell aggregations as settlement habitat

Habitat and shelter selection are critical behavioural processes influencing survival, growth and fitness across animal taxa. Understanding these processes provides key insights into how animals interact with their environment, respond to risks and maximize fitness. In benthic marine species, early life stages often face intense predation risk, making the choice of an appropriate refuge especially relevant. We investigated shelter-seeking behaviour in early benthic phase European lobster, Homarus gammarus, under controlled laboratory conditions, testing individuals in isolation to examine intrinsic shelter selection patterns without social interactions. Naïve stage VI juveniles were presented with mussel shell aggregations, stones representing natural cobble habitats and artificial polyvinyl chloride pipes as potential refuges. Initial shelter selection showed no significant deviation from random distribution, but extended observation periods revealed distinct temporal patterns in shelter use. Although juveniles readily occupied available shelters, monitoring after initial selection showed shelter-switching behaviour, particularly overnight, with transitions predominantly towards mussel shell aggregations. Across repeated trials, shelter-seeking efficiency improved, with decreased exploration times and reduced exploratory behaviours. Mussel shells emerged as the preferred shelter type, showing the highest retention rates and receiving the most transitions from other shelter types. This refinement in shelter selection suggests an innate preference for structurally complex refuges during the early benthic phase. These findings provide insights for optimizing restoration strategies, particularly in the context of restorative aquaculture where mussel farming areas could provide suitable release habitats. However, field validation remains essential for understanding how these behaviours translate to naturalconditions where predation pressure would influence shelter-seeking strategies. • Juveniles conceal rapidly but refine shelter selection through experience. • Shelter-switching occurred primarily at night when initial refuges were suboptimal. • Shelter-seeking efficiency and directness increased significantly with experience. • Mussel shells were consistently preferred over both stone and artificial refuges. • Mussel shell habitats show potential for lobster restoration strategies.