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Territorial Behavior and Population Dynamics of a Pomacentrid Fish, the Garibaldi, Hypsypops rubicunda
Author(s) -
Clarke Thomas A.
Publication year - 1970
Publication title -
ecological monographs
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.254
H-Index - 156
eISSN - 1557-7015
pISSN - 0012-9615
DOI - 10.2307/1942295
Subject(s) - intraspecific competition , ecology , nest (protein structural motif) , biology , population , predation , dominance (genetics) , spawn (biology) , population density , demography , biochemistry , sociology , gene
The garibaldi, Hypsypops rubicunda, is a California pomacentrid fish inhabiting the rocky subtidal between 0 and 25 m. Garibaldi feed almost exclusively on benthic organisms. Adults defend a territory which includes a shelter hole, grazing area, and for some males, a nest site. The territory is defended all year and against some other species as well as other garibaldi. The nest site is a small patch of red algae cultured by the male. The same site is used over a period of several years by the same male and probably by his successors. The female is allowed in the territory only to spawn; the eggs are guarded by the male. The young receive no parental care; they disperse into the plankton and settle out in shallow water. Age estimates from scales indicate that garibaldi assume adult coloration and mature at age 5 or 6 years and may live 13 or more years. Garibaldi have no obvious important predators or diseases. From age structures of several populations the mortality rate is estimated at about 9% of the adult population per year. In most cases potential recruitment more than balances mortality, indicating that population density is limited by some resource in the area and regulated by some form of intraspecific competition. Density and dispersion of both fish and resources (food, shelter, and nest sites), sex ratio, and age structure were determined in several study areas. From these data and a series of repopulation experiments, the most likely limiting and regulating factors are proposed. Density of adult garibaldi can be limited by supply of resources for survival or, where these are abundant, by minimal space requirements of nesting males. Exclusion by territory defense helps regulate density to limits set by food, space, etc. There is no evidence of feedback between density and the density limiting or regulating effects of territorial behavior. Territorial behavior seems to have evolved as a means of increasing reproductive success. Population effects, though beneficial, are probably incidental. There is no support for the hypothesis that territorial behavior in the garibaldi has evolved because it limits or regulates density.