A comparative analysis of the ecology and niche partitioning in two species of the fish genus Pholis (Pholididae)
Date
1983
Authors
Hughes, Grant William
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Abstract
The ecological relationship between two syntopic pholidid fishes, Pholis laeta and P. ornata was investigated to determine what factors were involved in the reduction of niche overlap in Saanich Inlet, Vancouver Island, British Columbia. Niche breadths and life histories were also compared. Data were collected by monthly beach seining, intertidal trapping, stomach sample analysis, laboratory activity rhythm recording and laboratory breeding observations.
Both P. laeta and P. ornata occur in the eelgrass beds during the summer months and show niche separation which may facilitate coexistence. Microhabitat use of the eelgrass depths, intertidal habitat use, prey type, and characteristic location of prey taken differ between species in fish of one year and older. Young of the year of both species share similar habitat and food. Food sizes increase with fish size but were similar in both species. Activity patterns were similar in both species. P. ornata average greater diversity of resource use than P. laeta and has a wider niche.
Both species are absent from the eelgrass during the winter months. P. laeta breed in the rocky intertidal and shallow subtidal zone in the absence of P. ornata during this time period. Eggs are guarded by one or both parents and hatch in early spring.
Growth rates of both species are similar although P. laeta live longer than P. ornata and grow to a larger size. Mortality rates are lower in P. laeta which, when combined with increased fecundity due to larger maximum size, may result in the greater abundance of this species compared to P. ornata.