Remoras are commensal fish that attach to sharks, rays, and other large marine animals using a modified dorsal fin. Their welfare intersects with that of their hosts.
In large public aquariums, remoras require access to appropriate host species or surrogate structures to attach to, or they become chronically stressed and inactive. Keeping remoras without suitable hosts deprives them of their fundamental ecological relationship. When shark or ray hosts are kept in captivity, remoras may be at risk of injury from tank walls when the host turns rapidly. Wild remoras occasionally attach to human divers, causing skin abrasion. Their welfare is largely overlooked in both public aquarium and research settings.