Social spacing in the temperate marine goby Coryphopterus nicholsi

Coryphopterus nicholsi is a temperate marine goby that occupies rock rubble in protected subtidal areas along the Pacific coast of NOrth America. In field populations, fish of all sizes and both sexes are found in the same habitat. All observed fish over 25 mm standard length defended space during both the reproductive and the non-reproductive seasons, with territory size being directly correlated with fish size. There was peripheral overlap of territories, particularly between adjacent adult conspecifics of different size classes, but also with smaller fish that had territories centered in the interstices of larger territories. However, zones of overlap were used at different times by space-sharing fish so that defended areas remained temporally discrete. Access to areas of overlap appeared to be determined by dominance rank. More dominant (usually larger) fish used areas of overlap at will; the defense and use of shared areas by less dominant fish was contingent upon the absence of larger fish. Social organization in C. nicholsi appears to be defined by a combination of territorial behavior and dominance relationships among adjacent individuals, permitting the coexistence of all members of the population under circumstances of limited habitat availability.