THE COMPARATIVE ECOLOGY OF THREE SYMPATRIC SPECIES OF CALIFORNIA BLENNIES OF THE GENUS HYPSOBLENNIUS

Three species of the blenniid genus Hypsoblennius, H. gilberti, jenkinsi, and gentilis, coexist in the shallow waters of the San Diegan Warm Temperate Region. Extensive field and laboratory studies were carried out to determine the degree of ecological differenti- ation present in these species. The dominant species, H. gilberti and H. jenkinsi show both behavioral and ecological specializations which are lacking in H. gentilis. These differences include: Habitat preference; H. gilberti inhabits the rocky intertidal and adj acent subtidal cobble; H. jenkinsi is found only subtidally, inhabiting boring clam burrows, Serpulorbis tubes or mussel beds. Adult motility: H. gilberti is a meandering species commonly including a radius as large as 15 m within its home range. Individuals return to "home" pools at low tide and homing has been demonstrated for displacements as great at 45 m. H. jenkinsi is seden- tary rarely wandering more than a meter from its home refuge. Homing was not demon- strated in this species, even for displacements as small as 5 m. Territoriality: Degree of territoriality correlates with movement, the sedentary species is highly territorial while this phenomena is less easily demonstrated in the meandering form. The above differences have been experimentally verified in the laboratory. All species are omnivorous, differences in gut content seem to represent different habitat associations. Reproduction occurs from spring through late summer; the eggs are guarded by the male. Hatching occurs in 4-18 days depending on temperature; the larvae are pelagic for about three months. Adult size differences reflect differing larval and first year growth plus differing longevity; determinate growth has not been demonstrated. Adult size varies between the species and is an important ecological factor. In the small tubiculous species H. jenkinsi, tube size controls fish size (habitat matching) probably through preditor selection. Habitats made up of different tube sizes support populations of significantly different mean fish size. In Newport Bay, population structures are altered by a viral infection, Lymphocystis which reaches epidemic levels during the warm months. The ecological differences between the three species seem to indicate that H. gentilis is the most generalized (primitive) form. The spcializations of its congeners adapt them to coexis- tence with limited competition. H. gentilis unspecialized and unable to compete in Southern California survives here in marginal habitats, particularly areas recently modified by man.