The mating system of Xyrichthys novacula: sperm economy and fertilization success

We determined the fertilization rates achieved by males of the polygynous wrasse Xyrichtys novacula in the northern Mediterranean sea, by collecting all sperms and eggs released in individual spawns from three adjacent male territories that encompassed different numbers of female home ranges. Two males with territories including four and six females respectively, released similar average numbers of sperm/spawn, whereas a male holding at the same time two territories with six females each, released significantly fewer sperm/spawn. Although fertilization rates decreased with absolute numbers of sperm released, the male with the largest harem achieved the highest total daily number of fertilized eggs, as a result of the high number of females in his territory. These results demonstrate a strategy of a male's sperm economy that is in conflict with the female's interests.