Abstract

We highlight the uncertainty that exists around estimating productivity and survival for one population of threatened steelhead Oncorhynchus mykiss (anadromous Rainbow Trout) with the goal of strengthening our understanding of the well-documented poor marine survival of Puget Sound steelhead. We evaluated how sensitive estimates of productivity and survival were to the uncertainty associated with smolt trap enumerations, redd survey methodology, estimates of fish per redd, and estimates of smolt production by resident Rainbow Trout in order to clarify causes of poor steelhead survival in this area. We show that from 2004 to 2014, estimates of both freshwater productivity and marine survival were highly sensitive to estimates of fish per redd used to expand redd counts, as well as error around smolt abundance estimates. Regardless, uncertainty associated with these inputs did not explain the low survival and high productivity observed for Nisqually River steelhead relative to other populations. In addition, we identified progeny from anadromous mothers upstream of what was previously considered a barrier, and we also documented that a proportion of steelhead smolts (N = 4/43) originated from resident mothers (Rainbow Trout). While these results indicated an underestimation in the total number of steelhead redds counted each year and an overestimation of steelhead progeny enumerated at smolt traps, they had little impact on estimates of survival and productivity. Results from the current study support previous work reporting poor marine survival for populations of Puget Sound steelhead and highlight the sympatric relationship between resident and anadromous life histories of O. mykiss. Overall, our study supports a management strategy that protects both the anadromous and fluvial forms of O. mykiss, prioritizes habitat improvements that promote freshwater productivity, and increases research focused on identifying causes of poor marine survival.

Published in

Transactions of the American Fisheries Society
2021, Volume: 150, number: 2, pages: 160-174
Publisher: WILEY

SLU Authors

• Losee, James

  • Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

Ensure availability and sustainable management of water and sanitation for all


UKÄ Subject classification

Fish and Aquacultural Science


Publication identifier

DOI: https://doi.org/10.1002/tafs.10275

Permanent link to this page (URI)

https://res.slu.se/id/publ/110523