Mound-building and Feeding Behavior of the Twostripe Goby, Valenciennea helsdingenii, in the South Red Sea

Abstract

The twostripe goby, Valenciennea helsdingenii, lives in pairs that cooperate in building large mounds, up to 60 cm diameter, over their burrows. In 10-min observations (N=81), their activities were recorded by SCUBA divers (directly or on video) from 17 April to 6 May 1994 in the Jabal Zuqar and Hanish Islands, Yemen, in the south Red Sea. A pair of gobies moved up to 90 pieces of rubble in 10 min (0–45, $\overline x$ 8.4 pieces per fish per 10-min observation). Pairs generally stayed close together and alternated in ‘feeding’, one watching while the other grabbed a mouthful of sand most of which filtered out the gill openings. A pair fed up to 259 times in one 10-min observation period with an average rate of 3.7 (range 0–13) times per fish per minute. The feeding rate was lower at dusk when the pair's main activity was carrying sand and rubble that closed the entrance of their burrow before plunging through this soft new barrier to retire inside for the night. They emerged from their burrow about 40 min after sunrise. Half of one medium-size mound was taken apart and consisted of 4062 pieces of coral rubble and shells. The hypothesis that building large mounds may be related to dominance and competition for mates, as in some cichlid fishes, does not apply to the isolated, stable pairs of V. helsdingenii.