A novel nest-trap for ecological and behavioural studies of cavity-nesting fishes

We developed an artificial nesting cavity to study the reproductive success of the naked goby, Gobiosoma bosci (Lacepede), in the field. The nest-trap not only served as a spawning site, but also acted as a trap to retrieve the eggs and the parent guarding the nest. Each nest-trap consisted of a piece of PVC pipe 50 or 60 mm in length, 12 multiplied by 5 or 19 multiplied by 0 mm inner diameter, and capped on each end. A 9 multiplied by 1-mm hole was drilled in the centre of one cap and six 3 multiplied by 3-mm holes were drilled in a ring in the other cap. The larger opening provided an entrance for the gobies; the six smaller holes were designed to enhance water exchange through the nest-trap. Each piece of pipe was cut in half length-wise to facilitate examination of the contents after the nest-trap was opened.