Courtship and spawning competition in pink salmon ( Oncorhynchus gorbuscha )

• Published in: Canadian Journal of Zoology
• Main Authors: Keenleyside, Miles H. A., Dupuis, Hélène M. C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1988
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Oncorhynchus gorbuscha; Pink salmon
• Online Access: http://dx.doi.org/10.1139/z88-037; http://www.nrcresearchpress.com/doi/pdf/10.1139/z88-037

Male pink salmon cluster in groups of up to 10 or more around a female as she prepares the substrate for spawning. The largest male in the group (in length and dorsal hump development) stays closest to the female; the others maintain a size-related hierarchy behind the pair. Position in the group is determined by frequent aggressive interactions among the members. Often a relatively small "outlier" male holds position near the central pair, to one side of the nest. These males are "female-like" in colour and size, and the dorsal hump is small. When the primary male settles into the nest bottom and quivers beside the female, males in the associated group, including the small outlier, dash into the nest. When the female and primary male spawn, some or all of the group males release sperm. Nest-digging females are territorial; they attack other females and small males. Their primary males are aggressive towards other males, but not towards females. They frequently attack the males closest to them in their group, but also attack nongroup males, including other large males who try, usually unsuccessfully, to replace them as the primary male. The phenomena of many males at a single nest, great variability in dorsal hump development, and outlier vs. fighting behaviour are all associated with male competition for access to spawning females.