Abstract
AbstractKey life‐cycle transitions, such as metamorphosis or migration, can be altered by a variety of external factors, such as climate variation, strong species interactions, and management intervention, or modulated by density dependence. Given that these life‐history transitions can influence population dynamics, understanding the simultaneous effects of intrinsic and extrinsic controls on life‐history expression is particularly relevant for species of management or conservation importance. Here, we examined how life histories of steelhead (Oncorhynchus mykiss) are affected by weather, pink salmon abundance (Oncorhynchus gorbuscha), experimental nutrient addition, and density‐dependent processes. We tested for impacts on the size of steelhead smolts (juveniles migrating to the sea), as well as their age and abundance across four decades in the Keogh River, British Columbia, Canada. Larger steelhead smolts were associated with warmer years and artificial nutrient addition. In addition, higher pink salmon abundance and artificial nutrient addition correlated with juvenile steelhead migrating at younger ages. While density dependence appeared to be the primary factor regulating the abundance of steelhead smolts, nutrient addition and temperature were positively and negatively associated with smolt production, respectively, prior to 1991, and pink salmon spawning abundance was positively associated with smolt production after 1990. Thus, this study provides evidence that the temporal dynamics of one species of salmon is linked to the juvenile life history of co‐occurring steelhead. A complex interplay of species interactions, nutrient subsidies, density dependence, and climatic variation can control the life‐history expression of species with complex life cycles.
Highlights
Life-history transitions of organisms with complex life cycles may be influenced by multiple factors such as weather, species interactions, and management intervention (Benard 2004)
We examined steelhead smolt size, age, and abundance and tested how these response variables may be influenced by six potential predictor variables: pink salmon spawner abundance, artificial nutrient addition, density dependence, temperature, summer precipitation, and winter precipitation
The spikes in the proportion of age-2 steelhead smolts coincide with years when nutrients were added to the whole river (Fig. 1c, d)
Summary
Life-history transitions of organisms with complex life cycles may be influenced by multiple factors such as weather, species interactions, and management intervention (Benard 2004). Such shifts in life-history transitions can connect the conditions in the first part of the life cycle to the part. Pacific salmonids are a management-relevant system for examining the simultaneous effects of intrinsic (i.e., density dependence) and extrinsic factors (e.g., climate, species interactions, and management actions) on life-history expression. The age and size of individuals undergoing the smoltification process can vary within and across populations (Groot and Margolis 1991, Quinn 2005), and life-history expression may respond to shifts in climate conditions (Crozier et al 2008). Life-history variation in salmon may be strongly influenced by environmental conditions and density dependence
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
