Effects of salmon-derived nutrients and habitat characteristics on population densities of stream-resident sculpins

PLoS One. 2015 Jun 1;10(6):e0116090. doi: 10.1371/journal.pone.0116090. eCollection 2015.

Abstract

Movement of nutrients across ecosystem boundaries can have important effects on food webs and population dynamics. An example from the North Pacific Rim is the connection between productive marine ecosystems and freshwaters driven by annual spawning migrations of Pacific salmon (Oncorhynchus spp). While a growing body of research has highlighted the importance of both pulsed nutrient subsidies and disturbance by spawning salmon, their effects on population densities of vertebrate consumers have rarely been tested, especially across streams spanning a wide range of natural variation in salmon densities and habitat characteristics. We studied resident freshwater prickly (Cottus asper), and coastrange sculpins (C. aleuticus) in coastal salmon spawning streams to test whether their population densities are affected by spawning densities of pink and chum salmon (O. gorbuscha and O. keta), as well as habitat characteristics. Coastrange sculpins occurred in the highest densities in streams with high densities of spawning pink and chum salmon. They also were more dense in streams with high pH, large watersheds, less area covered by pools, and lower gradients. In contrast, prickly sculpin densities were higher in streams with more large wood and pools, and less canopy cover, but their densities were not correlated with salmon. These results for coastrange sculpins provide evidence of a numerical population response by freshwater fish to increased availability of salmon subsidies in streams. These results demonstrate complex and context-dependent relationships between spawning Pacific salmon and coastal ecosystems and can inform an ecosystem-based approach to their management and conservation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Ecosystem
  • Fresh Water
  • Population Density
  • Population Dynamics
  • Rivers
  • Salmon / physiology*

Grants and funding

This work was supported by the NSERC Alexander Graham Bell Canada Graduate Scholarship (www.nserc-crsng.gc.ca) and Pacific Century Graduate Scholarship to NRS; and NSERC Discovery and Accelerator Grants to JDR, and the Tom Buell Research Chair partnership between the Pacific Salmon Foundation (www.psf.ca), the BC Leading Edge Fund (www.leefbc.ca), and Simon Fraser University (www.sfu.ca). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.