Integrating Sublethal Copper Neurotoxicity in Coho Salmon Across Scales of Biological Complexity

Many metals are neurotoxic to aquatic animals.  Copper is a common aquatic pollutant resulting from mining, industrial, agricultural, and urban land uses. Outside of mine drainage, concentrations in waters receiving runoff enriched in copper are usually <100 ppb, and commonly <10 ppb.  Dissolved copper in the low parts per billion range is neurotoxic to the peripheral sensory system of fish, including mechanosensation and olfaction.  Salmonids use olfactory cues to inform many behaviors critical to their fitness including establishing social dominance hierarchies, evading predators, navigating to spawning sites, and reproductive priming.  Ultrastructural damage to mechanosensory and olfactory sensory neurons are well-documented effects in fish of acute exposure to dissolved copper. We have studied in detail the effect of dissolved copper exposure on loss of olfactory ability and loss of antipredation behavior in juvenile coho salmon. Neurophysiological inhibition of olfactory response to odors occurs at copper concentrations as low as 2 ppb above background.  Loss of olfactory-dependent antipredation behavior is highly correlated with the loss of olfactory ability. This talk will review copper neurotoxicity in fishes, focusing on effects in salmonids, and present the latest research linking copper exposure to reduced survival of juvenile salmonids in predation encounters.