Program: Sustainability Theme: Sustainable forest management indicators, targets, and monitoring systems Logging can increase the amount of exposure to solar ultraviolet radiation (UVR) that timberland streams receive both through the thinning of riparian vegetation and by altering the amount of UVR absorbing dissolved organic carbon (DOC) entering streams. Juvenile coho (Oncorhynchus kisutch) are ubiquitous in coastal British Columbia streams and are among the most sensitive fish species to UVR. Studies at the Pacific Biological Station in Nanaimo, BC have documented many direct effects of UVR on juvenile coho such as fin erosion, altered body morphology and incipient cataracts (Bothwell, Holtby and others in prep). While these effects may impact marine survival, they are not easily measured. One exception, however, is the presence of UV-absorbing compounds in the skin (sunscreen substances) which are formed during exposure to UVR. In this project we are developing a bioassay technique for UV exposure of juvenile coho based upon the amount of photo-protective sunscreen compound(s) in their skin. Once the bioassay is calibrated we will be able to determine the amount of UVR exposure of juvenile coho in situ. This technique, applied to diverse stream types and logging scenarios, will allow an assessment of whether or not juvenile coho are subjected to elevated UVR following logging, what logging situations produce greater UVR exposures, and how long UVR impacts might last following logging. Vancouver Island streams with definable gradients of DOC will be used to determine if UVR avoidance behaviour of juvenile coho is effective in preventing excessive exposure following removal of streamside canopy shade. In later stages of this project we will assess how various logging approaches and biogeographic characteristics of watersheds influence the export of DOC and therefore UVR exposure of coho.
Bothwell, Max L., Lynch, Donovan R.. 2007. Does logging elevated ultraviolet radiation exposure of streams impact juvenile coho?. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report