Fly fishers say the salmon population at the burn in Moray has been wiped out and could take years to recover.
Analysis suggests low water flow and high temperatures could have caused fish to die in the Spey.
The river's fishery board believes that in excess of 50 salmon and trout have died.
Inverness' Raigmore Hospital also needs more staff to be able to support pregnant women from Moray, the report says.
The 27-year-old who died in the accident on an unclassified road was a man from Sunderland.
The man died at the scene of the one-vehicle collision, between Dallas and Knockando.
It was downgraded in 2018 due to staff shortages, forcing expectant mothers to travel to Aberdeen.
