UBC Theses and Dissertations
Reproductive and natal homing of marine threespine sticklebacks (Gasterosteus aculeatus) Saimoto, Ron Shigeo
Natal and reproductive homing were investigated in marine and anadromous populations of threespine sticklebacks (Gasterosteus aculeatus). Three breeding sites within 1 km2of Pender Harbour, British Columbia, were examined. For the reproductive homing experiment (displacement of adults from a breeding site), female sticklebacks from Oyster Lagoon, Salt Lagoon, and Paq Creek were marked and displaced (.15 - 1.0 km) to three release sites. These displaced females predominately returned to their original breeding sites, although there was some straying. The proportion of marked fish recaptured at their original breeding site ranged from 0.81 to 1.00. The anadromous population (Paq Creek) showed the strongest tendency to return (0.99 - 1.00). Natal homing (return to birth site) was investigated in the Oyster Lagoon population. Young of the year were marked on three different outmigrations (April 1991, August 1991, and April 1992): 0.85 %, 3.5% and 5.2 % respectively, were recaptured as adults during the 1992 breeding season at Oyster Lagoon. Relatively short stays outside the lagoon (2 - 4 months), by juveniles that overwintered in Oyster Lagoon, resulted in strong natal homing and weak straying to adjacent breeding sites; however, straying to Salt Lagoon increased with longer stays outside the lagoon. This suggests an inverse relationship between the length of time spent out of the lagoon and the accuracy of homing. Straying to the anadromous breeding site (Paq Creek) remained low for all lengths of stay in the sea (2 - 16 months). This maintained avoidance of Paq Creek suggests that the marine and anadromous populations may be genetically isolated. The level of straying between Salt and Oyster lagoons probably is sufficient to prevent divergence between these adjacent marine populations. Generally however, this study demonstrates both reproductive and natal homing in threespine sticklebacks and, on a larger geographic scale, this natal homing may be sufficient to allow the evolution of inter-population heterogeneity among marine and anadromous populations.
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