Plans for seven new hydroelectric schemes across Scotland have provoked opposition from anglers, environmentalists and local people.

The conflicts highlight the problems plaguing the expansion of renewable energy, and could make it more difficult for the Scottish government to harness "clean" power to combat global warming.

According to the Tay District Salmon Fisheries Board, a Somerset-based firm called Shawater has submitted planning applications for hydro schemes on the Tay catchment. Four are in Glenlyon on the Innerwick, Invervar, Inverinain and Keltney burns, with three others on the Urlar burn in Aberfeldy, the Inverhaggernie burn near Tyndrum, and the Innerhadden burn by Kinloch Rannoch.

David Summers, of the Fisheries Board, is worried about the impact of the schemes on salmon and trout. "Should all these schemes be built, the steep stream brown trout population in Tayside may suffer a significant loss," he said.

He said that as more steep streams were exploited, he feared developers would turn to streams which were more important to migratory fish like salmon.

The government's conservation agency, Scottish Natural Heritage, said it had objected to the Innerwick and Inverinain schemes. It said it was concerned about the lack of information on risks to the endangered freshwater pearl mussel, and potential damage to a scenic and nature conservation area.

SNH was also examining the proposal for Invervar, which has attracted fierce opposition from local residents.

"We are all in favour of green energy but these ill-conceived schemes will end up costing the earth," said Jamie Grant, of Invervar Community Association. He stressed that hydro developments were needed, but had to be better designed.

"Salmon populations are too vulnerable to start cutting off their breeding grounds with small hydro schemes that make a relatively tiny contribution to the government's renewable target. If these seven schemes are not modified to protect our wild salmon they'll end up giving hydro power in Scotland a bad name."

He was backed by Andrew Thompson, vice-convener of Perth Green Party, who accused developer Shawater of trying to "squeeze a quart into a pint pot".

Thompson added: "There is potential for a less aggressive scheme on the Invervar burn, which would satisfy all interests and can still make a valuable addition to renewable energy supplies, and a significant contribution to the economy of the local estate."

Shawater is currently designing and developing more than 30 small-scale hydro projects in the UK, but managing director Tom Shaw declined to answer questions on the Tayside schemes. He said: "The evidence which addresses your questions is currently before the relevant planning authorities for consideration, submitted in the usual way."

The Scottish Environment Protection Agency (Sepa) confirmed it was currently considering "several applications" for hydro schemes in the Tay catchment.