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11-08-2010, 03:12 PM #1
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Movements of male sockeye salmon, Oncorhynchus nerka, on spawning grounds: effects of
By Harry B. Rich Jr., Stephanie M. Carlson, Brandon E. Chasco, Kimberly C. Briggs, Thomas P. Quinn
Animal Behaviour, Volume 71, Issue 4, April 2006, Pages 971-981, ISSN 0003-3472, DOI: 10.1016/j.anbehav.2005.10.004.
Philopatry or homing isolates breeding groups and therefore strongly affects population structure within a species. In salmonid fish, the movements of males among nesting females may control gene flow, and therefore affect fine-scale population structure, within and among breeding grounds. In this study, we recorded the daily movements of male sockeye salmon from three populations during the breeding period. We modelled daily movement using an exponential function and then added additional parameters to explore the extent to which movement varied between streams, between years within streams as salmon density varied, and between males of different ages/sizes. This approach revealed that: (1) in all three streams, male movement decreased as a function of time on the breeding grounds and was limited in most cases, (2) movement patterns, particularly initial exploratory movement, differed between streams, (3) movement patterns differed between years within a stream but were unrelated to density, and (4) there was little effect of age/size on movement; the small observed effect was due to differences in exploratory movement, not sustained differences over the entire breeding season. Overall, the restricted movements by males on the breeding grounds indicated that salmon populations can be structured on fine spatial scales as a result of limited gene flow within seasons if homing to precise natal locations also occurs.