Distribution patterns of the cardinal fish,Apogon imberbis, in shallow marine caves in southern Apulia (SE Italy)

Distribution patterns of the sciaphilic cardinal fish, Apogon imberbis, were investigated by visual census in southern Apulia (SE Italy, Mediterranean Sea) in three shallow marine caves. Sampling was carried out in four periods, from July 2000 to June 2001 and A. imberbis was always found in large numbers inside all three caves. Density values ranged from a few to more than 1800 individuals 100 m‐2. Great numbers of juveniles, about 1 cm long, with a reddish‐transparent livery and grouped in large schools, were found in July 2000 in the three caves. Adult A. imberbis were fairly evenly distributed in time, among caves, as well as within each cave along the axis; recruitment appeared to be the most important process affecting temporal changes in total abundance of A. imberbis. The present study thus showed that marine caves represent important nurseries for recruiting of A. imberbis, as well as the preferred habitat for adults. The fact that A. imberbis may reach such high densities inside marine caves supports the hypothesis that this fish could play a relevant ecological role in the daily transfer of organic matter into these environments, an issue deserving further research.