Steelhead trout and estuary use in Puget Sound

For more information, view the original reports: The role of estuaries in the ecology of adult Pacific salmon and trout in Puget Sound and The role of estuaries in the ecology of juvenile Pacific salmon and trout in Puget Sound.

Overview

Steelhead, the anadromous form of rainbow trout, leave Puget Sound rapidly as smolts (Goetz et al. 2015, Moore et al. 2015) and do not return until they are maturing adults (Myers 2018). 

Adults

Some steelhead arrive in nearshore areas in the winter in a rather advanced state of maturity, migrate upriver, and spawn soon thereafter in winter and spring. These fish are referred to as winter run or ocean-maturing steelhead (Busby et al. 1996), as exemplified by the Skagit and Stillaguamish rivers (Figure 1). This form is the dominant one in Puget Sound rivers, but the alternative form, called summer run or river-maturing also occurs. These summer steelhead fish migrate from the ocean in the late summer, spend the winter in rivers, and then undergo final maturation and spawn in the spring. These variable natural patterns have also been modified by the selective effects of fishing and hatchery operations (Mackey et al. 2001, McLean et al. 2005, McMillan et al. 2022), but steelhead still enter rivers over a broad period. 

It is also important to note that the species is iteroparous (able to reproduce more than once during its lifetime), thus adult use (or at least pass through) estuaries not only on their homeward migration but also as they leave if they survive spawning, and then again on subsequent return migrations if they are fortunate. These downstream migrants may be in estuaries while others are migrating upriver to spawn, or later in the season after all upstream migrants have passed. The proportion of steelhead that successfully return to spawn more than once is low, and especially so for males (Clemens 2015, Copeland et al. 2019). This seems to result from energy depletion during migration and reproduction, and is especially acute for interior, summer-run populations (Penney and Moffitt 2014, Penney et al. 2016). 

Winter run steelhead movements in estuaries have not been studied but work in coastal British Columbia fjords indicated that summer steelhead migrated in open water, very close to the surface, and were much less active at night than during the day (Ruggerone et al. 1990). 

The post-spawning adults, known as kelts, have not been closely studied in Puget Sound but work in the Sacramento River system indicated that some remained in the river system after spawning whereas others went back to sea (Null et al. 2013), and those that entered the ocean were near the surface (Teo et al. 2013), as seems typical of the species (Nielsen et al. 2011). We do not know to what extent steelhead kelts use estuaries in Puget Sound, and this is another area where further work seems needed. Because most of the kelts are females, they are especially important for population health.

Juveniles

Steelhead and cutthroat trout are usually the largest smolts to migrate downstream, and they share similar timing and size but differ entirely in how they behave after reaching estuaries. Wild steelhead smolts from this region typically migrate to sea after two years of rearing in streams at about 160 mm in length, though some variation exists in the age and timing of migration (Hall et al. 2016). Hatchery-produced steelhead are typically released after one year of growth (Busby et al. 1996). As illustrated with data from the Stillaguamish River, their migration peaks in May (Figure 2). Steelhead are produced in the large rivers of the region and small ones as well, but the migration patterns seem similar. Some members of the population (and especially males) may remain in the river and mature as rainbow trout, breeding with either female steelhead or resident females. Given this fact, one might therefore think those going to sea would be half-hearted about it and stay near shore. On the contrary, all evidence indicates that steelhead smolts move directly into open water and rapidly exit Puget Sound for the North Pacific Ocean, where they feed far from shore (Myers 2018) until they return to spawn, typically in the late winter.

Both juveniles and adults demonstrate rapid estuarine transit, though this has been studied more extensively in juveniles. We know this from the comparatively low catches of steelhead smolts in estuaries, and from acoustic tracking studies. Fish with transmitters left rivers and were detected exiting Puget Sound after traveling about 6-8 km/day (Goetz et al. 2015, Moore et al. 2015), and faster between Vancouver Island and the mainland of British Columbia (Melnychuk et al. 2007, Melnychuk et al. 2010). Populations elsewhere such as the Oregon coast (Romer et al. 2013), Columbia River (Daly et al. 2014), and San Francisco Bay (Chapman et al. 2015) also leave their estuaries very rapidly, so this is a general tendency for steelhead. A study of over 1,400 steelhead smolts implanted with sonic tags did not detect delayed migration patterns or extended rearing in Puget Sound (Moore et al. 2015), so extended residency seems to be at most a rare phenomenon in steelhead. Consequently, their reliance on estuaries seems to be minimal.

References

Busby, P. J., T. C. Wainwright, G. J. Bryant, L. J. Lierheimer, R. S. Waples, F. W. Waknitz, and I. V. Lagomarsino. 1996. Status review of west coast steelhead from Washington, Idaho, Oregon and California. National Marine Fisheries Service Seattle.

Chapman, E. D., A. R. Hearn, G. P. Singer, W. N. Brostoff, P. E. LaCivita, and A. P. Klimley. 2015. Movements of steelhead (Oncorhynchus mykiss) smolts migrating through the San Francisco Bay Estuary. Environmental Biology of Fishes 98:1069--1080.

Clemens, B. J. 2015. A survey of steelhead age and iteroparity rates from a volunteer angler program in the Willamette River basin, Oregon. North American Journal of Fisheries Management 35:1046-1054.

Copeland, T., B. J. Bowersox, M. W. Ackerman, and C. Camacho. 2019. Patterns of iteroparity in wild Snake River steelhead. Transactions of the American Fisheries Society 148:926-937.

Daly, E. A., J. A. Scheurer, R. D. Brodeur, L. A. Weitkamp, B. R. Beckman, and J. A. Miller. 2014. Juvenile steelhead distribution, migration, feeding, and growth in the Columbia River estuary, plume, and coastal waters. Marine and Coastal Fisheries 6:62-80.

Goetz, F. A., E. Jeanes, M. E. Moore, and T. P. Quinn. 2015. Comparative migratory behavior and survival of wild and hatchery steelhead (Oncorhynchus mykiss) smolts in riverine, estuarine, and marine habitats of Puget Sound, Washington. Environmental Biology of Fishes 98:357-375.

Hall, J., P. Roni, T. Bennett, J. McMillan, K. Hanson, R. Moses, M. McHenry, G. Pess, and W. Ehinger. 2016. Life history diversity of steelhead in two coastal Washington watersheds. Transactions of the American Fisheries Society 145:990-1005.

Mackey, G., J. E. McLean, and T. P. Quinn. 2001. Comparisons of run timing, spatial distribution, and length of wild and newly established hatchery populations of steelhead in Forks Creek, Washington. North American Journal of Fisheries Management 21:717-724.

McLean, J. E., P. Bentzen, and T. P. Quinn. 2005. Nonrandom, size- and timing-biased breeding in a hatchery population of steelhead trout. Conservation Biology 19:446-454.

McMillan, J. R., M. R. Sloat, M. Liermann, and G. Pess. 2022. Historical records reveal changes to the migration timing and abundance of winter steelhead in Olympic Peninsula rivers, Washington State, USA. North American Journal of Fisheries Management 42:3-23.

Melnychuk, M. C., D. W. Welch, and C. J. Walters. 2010. Spatiotemporal migration patterns of Pacific salmon smolts in rivers and coastal marine waters. PLoS ONE 5:e12916.

Melnychuk, M. C., D. W. Welch, C. J. Walters, and V. Christensen. 2007. Riverine and early ocean migration and mortality patterns of juvenile steelhead trout (Oncorhynchus mykiss) from the Cheakamus River, British Columbia. Hydrobiologia 582:55-65.

Moore, M. E., B. A. Berejikian, F. A. Goetz, A. G. Berger, S. S. Hodgson, E. J. Connor, and T. P. Quinn. 2015. Multi-population analysis of Puget Sound steelhead survival and migration behavior. Marine Ecology Progress Series 537:217-232.

Myers, K. W. 2018. Ocean ecology of steelhead. Pages 779-904 in R. J. Beamish, editor. The Ocean Ecology of Pacific Salmon and Trout. American Fisheries Society, Bethesda.

Nielsen, J. L., S. M. Turner, and C. E. Zimmerman. 2011. Electronic tags and genetics explore variation in migrating steelhead kelts (Oncorhynchus mykiss), Ninilchik River, Alaska. Canadian Journal of Fisheries and Aquatic Sciences 68:1-16.

Null, R. E., K. S. Niemela, and S. F. Hamelberg. 2013. Post-spawn migrations of hatchery-origin Oncorhynchus mykiss kelts in the Central Valley of California. Environmental Biology of Fishes 96:341--353.

Penney, Z. L. and C. M. Moffitt. 2014. Proximate composition and energy density of stream-maturing adult steelhead during upstream migration, sexual maturity, and kelt emigration. Transactions of the American Fisheries Society 143:399-413.

Penney, Z. L., C. M. Moffitt, B. Jones, and B. Marston. 2016. Physiological comparisons of steelhead kelts emigrating from the Situk River, AK and Clearwater River, ID. Environmental Biology of Fishes 99:487--498.

Romer, J. D., C. A. Leblanc, S. Clements, J. A. Ferguson, M. L. Kent, D. Noakes, and C. B. Schreck. 2013. Survival and behavior of juvenile steelhead trout (Oncorhynchus mykiss) in two estuaries in Oregon, USA. Environmental Biology of Fishes 96:849-863.

Ruggerone, G. T., T. P. Quinn, I. A. McGregor, and T. S. Wilkinson. 1990. Horizontal and vertical movements of adult steelhead trout, Oncorhynchus mykiss, in Dean and Fisher channels, British Columbia. Canadian Journal of Fisheries and Aquatic Sciences 47:1963-1969.

Teo, S. L. H., P. T. Sandstrom, E. D. Chapman, R. E. Null, K. Brown, A. P. Klimley, and B. A. Block. 2013. Archival and acoustic tags reveal the post-spawning migrations, diving behavior, and thermal habitat of hatchery-origin Sacramento River steelhead kelts (Oncorhynchus mykiss). Environmental Biology of Fishes 96:175-187.