The behavioral response of the territorial damselfish Pacific gregory Stegastes fasciolatus to nests built within their territories by the sergeant major damselfish Abudefduf vaigiensis was studied on the northern coast of Taiwan in the summer of 1986. In one instance where 24 A. vaigiensis nests were built on a reef area already occupied by 27 territorial S. fasciolatus, 75% of S. fasciolatus individuals were observed to take eggs from these new nests when the opportunity was available. The number of eggs consumed did not correlate significantly with the standard length of the predator. On the average, a S. fasciolatus individual consumed 1,100 eggs (SO = 370, n = 11) daily. The high incidence of egg predation suggests that eggs can be an important food item for these original territory-holders; when A. vaigiensis outcompete S. fasciolatus for a substrate for nesting, they have also made this otherwise unavailable food resource available to the latter fish.
Competition, Damselfish, Egg, Nest, Predation
