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Salmonids and flows: a perspective on the state of the science and its application


Correspondence: Nigel Milner, APEM Ltd, School of Biological Sciences, Bangor University, Brambell Building, Deiniol Rd, Bangor LL57 2UW, UK (e-mail:


Water flow, volume discharge per unit time, is a master variable influencing much of the river environment and having profound effects on most of the biota, either directly or indirectly. Nevertheless, after decades of research and much accumulated knowledge, there remains much uncertainty about how to set environmental standards for flows that protect ecosystem components, including salmonids. This paper provides an overview of the findings of a conference on Flows and Salmonids. The aim of the conference and the papers that form this special issue is to update this information for salmonids, from which four key points are distilled that might influence future direction. (1) Fish responses to flow are very variable and flow effects are highly confounded with other related variables, which are often the proximate factors and need to be taken into account. (2) Meta-analysis of previous studies has yet to be achieved because a hydromorphological template against which to gather and display such data has not yet been satisfactorily defined. (3) Some deviation from natural conditions may not necessarily be as detrimental for salmonids as sometimes stated. (4) Local investigations of flow impacts and solutions based on local conditions, and bringing in diverse disciplines and stakeholders, appear to offer the most pragmatic and effective approach to defining and implementing protective flows. Adaptive management offers a route for such collaborative studies, and its use is strongly encouraged.