Tidal energy projects could adversely affect marine life, a Scottish expert will tell a world conference.
Tidal energy extraction could change underwater environments
Professor Ian Bryden will also warn against over-stating the power capacity available from tidal and wave energy.
Professor Bryden, of the Robert Gordon University in Aberdeen, will present findings of research at the World Renewable Energy Congress in the US.
He believes the resource has potential but has urged caution over its development and impact.
The congress, to be held in Denver at the end of August, will bring together international experts in all aspects of renewable energy.
Professor Bryden is a director of the Aberdeen Renewable Energy Group and a member of the Forum for Renewable Energy Development in Scotland.
He will tell delegates that the variable nature of tides must be taken into account when choosing a site for development.
The professor has warned that tidal energy extraction could change the "underlying hydraulic characteristics of tidal environments".
He said: "If you go above the guidelines that we are suggesting then you would produce a local slowing of the tidal flow which could have an influence on marine life - sea birds, marine mammals, fish - we don't at this stage know how severe that impact would be.
"This should not prevent tidal current development but we must apply sensitivity, based upon detailed understanding of tidal physics, when tidal energy developments are planned."
Professor Bryden is a supporter of renewable energy and believes the tidal resource, especially in the UK, is "massive" and likely to play a major part in the development of new energy industries and targets for renewables.
But he added: "There is little to be gained, however, by neglecting the very real constraints which must limit development.
"Developers must base their plans on realistic resource estimates, if costly mistakes are to be prevented."
Earlier this month, a new centre to harness wave and tidal energy in Scotland was officially opened in Orkney.
The £5.5m European Marine Energy Centre in Stromness is pioneering the testing of marine power devices.
Ministers are committed to 10% of electricity being generated from renewable sources by 2010, with that figure doubling to 20% by 2020.