Zoological Studies

Vol. 36 No. 1, 1997

Sympatric Spawning of the Damselfishes Chromis fumea and Pomacentrus coelestis on the Northern Coast of Taiwan

Rong-Quen Jan

Inst.of Zoology, Academia Slnice, Taipei, Taiwan 115

Rong-Quen Jan (1997) The damselfishes Chromis fumea and Pomacentrus coelestis are both free-ranging demersal spawners; they generally do not occupy a permanent substrate. A total of 2149 nests of C. fumea and 890 nests of P. coelestis were found in the study area on the northern coast of Taiwan in the spawning season of 1986. Both species spawned in groups. Sympatrie spawnings, which involved about 1/3 of C. fumea nests and 12.1 % of P. coelestis nests, occurred at some of the spawning  sites. The 2 damselfish species nested mainly on different substrates: C. fumea on open substrate, with P. coelestis in small burrows or depressions excavated beneath boulders. However, interference occurred whenever they spawned sympatrically. When the interactions involved only 1 individual of each species, C. fumea (which is larger in size and built nests first) was able to prevent the competitor from building a nest in the neighboring area by active aggression. In comparison, when the 2 species encountered each other in groups, harassment from P. coetestis was observed to force C. fumea to abandon their nests. P. coelestis Subsequently built nests at the site taken over from the latter fish.

Key words: Nesting substrate, Pomacentridae, Resource partitioning, Spawning season.

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