Are salmonids extra-sensitive to silty water?

Posted on January 5, 2013

In many waterways, loads of fine sediment have increased massively as a result of human disturbance.   High sediment concentrations can have adverse physical, chemical and ecological effects on freshwater ecosystems.  Fish species, especially those at or near the top of the food chain, can be good biological indicators of these impacts.  A group of U.K. researchers has reviewed the direct and indirect impacts of fine sediment on freshwater fish.  Although there are a number of knowledge gaps, it’s been established that short-term effects can include stress responses, reduced feeding, and mortality due to oxygen starvation.  Intermediate-term effects include lowered resistance to toxins and disease, physical damage to gills, interrupted osmoregulation and gas exchange, pH stress, slower growth and development, and reduced survival.  Long-term impacts include population-level effects such as local extinctions.  The vulnerability of fish to high silt loads is highest during the incubation stage when fish embryos are immobile.   Most of the research in this area has been carried out on salmonid species, but it’s been suggested that salmonids could be more vulnerable to the damaging effects of fine sediment than members of other fish families that spawn multiple times, produce larger numbers of eggs with shorter incubation periods, or spawn at times of year when high sediment flows are less common.

Reference: Kemp, P., Sear, D., Collins, A., Naden, P. & Jones, I.   2011.  The impacts of fine sediment on riverine fish.  Hydrological Processes  25, 1800–1821.