Spawning habitat segregation of sympatric sockeye and pink salmon

Spatiotemporal distributions and microhabitat use of pink salmon Oncorhynchus gorbuscha and sockeye salmon O. nerka were studied in Lake Creek, southeast Alaska, during three spawning seasons. Sockeye salmon migrated approximately 1 week earlier than pink salmon and spawned 250-350 m upstream from pink salmon. Habitat overlap measured with proportional similarity index monotonically increased with increasing spawner densities. Multidimensional niche spaces measured with water depth, current velocity, and channel gradient at redds were significantly different between pink and sockeye salmon (P < 0.005, Hotelling's T-2-test). However, classification of the redds into individual species was subjected to large error rates; 33% of 70 pink salmon redds and 34% of 125 sockeye salmon redds were misclassified. Competitive inter action between pink and sockeye salmon was not demonstrated.