Sexual dimorphism, resource partitioning and intraspecific aggression in Caprella californica Stimpson

The Caprellidae are a specialized suborder of Amphipoda, which are highly modified for a semisessile life. Caprellids exhibit direct development and brood their young. The suborder is exclusively marine and commonly found on filamentous algae, sea grasses and fouling communities. Most published works on caprellids have been primarily concern~d with systematics (Caine, 1974; Dougherty, 1943; Laubitz, 1970, 1972; McCain, 1968, 1975), although a few recent studies have dealt with ecology and ethology (Bynum, 1978; Caine, 1977; Keith, 1969, 1971; Lewbel, 1978; Saunders, 1966). This study examines·spatial and temporal variations in distribution, abundance and population structure as well as describing intraspecific aggressive behavior of Caprella californica Stimpson. ~- californica is dioecious and has marked sexual dimorphism in both its size and secondary sex characteristics. It is found from San Diego to the South China Sea (Laubitz, 1970), and is the dominant caprellid in the Zostera marina beds of the local bays and is a major diet item for many of the eel grass associated fishes. There is a preponderance of females in the population as well as a size-specific distribution of the proportion of the sexes