Nesting behavior of the icefish Chaenocephalus aceratus at Bouvetoya Island, Southern Ocean

We describe in situ observations on nesting by the Scotia Sea (or blackfin) icefish Chaenocephalus aceratus (Lonnberg) that constitute the first substantive evidence of egg brooding and parental care by species of the family Channichthyidae. At Boutetoya Island six fish, all apparently male, were observed guarding egg nests at depths of 141-148 m during an ROV deployment. Eggs were laid as aggregated, round masses (similar to 20-25 cm diameter) in shallow, circular depressions (similar to 1-m diameter, similar to 20-cm depth) that were probably excavated by the parent(s) to protect the nests. The fish guardians remained tenaciously in contact with the eggs despite disturbances caused by the ROV, reacting to this threat with stress and defense behaviors. Because brooding fishes are more susceptible to the population impacts from trawl fisheries, we argue that this life history should be kept in mind in designing management schemes.