Recurrent Die-Offs of Adult Coho Salmon Returning to Spawn in Puget Sound Lowland Urban Streams

Abstract

Several Seattle-area streams in Puget Sound were the focus of habitat restoration projects in the 1990s. Post-project effectiveness monitoring surveys revealed anomalous behaviors among adult coho salmon returning to spawn in restored reaches. These included erratic surface swimming, gaping, fin splaying, and loss of orientation and equilibrium. Affected fish died within hours, and female carcasses generally showed high rates (>90%) of egg retention. Beginning in the fall of 2002, systematic spawner surveys were conducted to 1) assess the severity of the adult die-offs, 2) compare spawner mortality in urban vs. non-urban streams, and 3) identify water quality and spawner condition factors that might be associated with the recurrent fish kills. The forensic investigation focused on conventional water quality parameters (e.g., dissolved oxygen, temperature, ammonia), fish condition, pathogen exposure and disease status, and exposures to metals, polycyclic aromatic hydrocarbons, and current use pesticides. Daily surveys of a representative urban stream (Longfellow Creek) from 2002–2009 revealed premature spawner mortality rates that ranged from 60–100% of each fall run. The comparable rate in a non-urban stream was <1% (Fortson Creek, surveyed in 2002). Conventional water quality, pesticide exposure, disease, and spawner condition showed no relationship to the syndrome. Coho salmon did show evidence of exposure to metals and petroleum hydrocarbons, both of which commonly originate from motor vehicles in urban landscapes. The weight of evidence suggests that freshwater-transitional coho are particularly vulnerable to an as-yet unidentified toxic contaminant (or contaminant mixture) in urban runoff. Stormwater may therefore place important constraints on efforts to conserve and recover coho populations in urban and urbanizing watersheds throughout the western United States.

Sensitivity and specificity of histology for diagnoses of four common pathogens and detection of nontarget pathogens in adult Chinook salmon (Oncorhynchus tshawytscha) in fresh water

“…30,48 Successful studies using histology to survey for pathogens and associated lesions in salmonids have been reported in the Pacific Northwest of the United States 22,28,44 and in British Columbia, Canada. 45 Histological changes were also an endpoint in a recent investigation of cause of mortality in coho salmon (Oncorhynchus kisutch), 46 and a previous study 8 used histology to describe lesions in sockeye salmon (Oncorhynchus nerka) associated with prespawn mortality (PSM). For the past decade, PSM of adult Chinook salmon in the Willamette 482124V DIXXX10.1177/1040638713482124Kent et alSensitivity and specificity of histology with salmon pathogens From the Departments of Microbiology (Kent) and Fisheries and River system, Oregon, has been extremely elevated (≤90% in some cases).…”

Effects of cadmium on olfactory mediated behaviors and molecular biomarkers in coho salmon (Oncorhynchus kisutch)

“…One of the factors implicated in these population declines is inhibition of olfactory processes associated with exposures to waterborne pollutants, including metals (Brown et al, 1994; Domagalski, 1996; Sandahl et al, 2007; Baldwin et al, 2009; Feist et al, 2011; Scholz et al, 2011). The olfactory sensory epithelium is in direct contact with the water column, making it highly sensitive to metal uptake and metal-induced olfactory injury (Julliard et al, 1996; Beyers et al, 2001; Moore et al, 2001; Baldwin et al, 2003; Scott et al, 2003; Carreau et al, 2005; Kalmakov et al, 2009).…”

Local adaptation to cold temperatures by larval coho salmon (Oncorhynchus kisutch) from different populations throughout British Columbia

“…Based on a condition factor of 1.06 g · cm -3 (CF; 100 W · L -3 ), determined from Kitimat River population females (Chapter 3), length was used to calculate an approximate total weight. A CF of 1.06 for mature female coho salmon falls within the range reported by Scholz et al (2011) for spawning female coho salmon in the Puget Sound…”