The project as a whole consists of a number of sub-projects which are: a) Is female coloration a signal of quality? b) Do males conduct post-spawning mate choice through differential filial cannibalism? c)Do female preferences for male size change throughout the season? d)Do female common gobies compete for access to high-quality males? e)Are male reproductive decisions influenced by prior expectation of female quality? f)How is male-male competition over nest sites influenced by resource holding potential and resource value? g)How do parasites influence mate preferences in two-spotted gobies?