Scientists and volunteers are preparing to survey the sea off Scotland's west coast for minke whales.
Minke whales are still commercially hunted
Sightings of the mammal were significantly down last year, possibly due to a shortage of sprats on which they feed.
Sea Watch Foundation said overall sightings had dropped from 286 in 2004 to 150 in 2005.
The marine charity is to begin monitoring for minke whales over the next few weeks.
Sea Watch research director Dr Peter Evans said there had been a couple of sightings already.
He said: "Sightings of minke whales are more common from May to October when herring, sprats, sand eels and other fish upon which they depend are concentrated in shallower coastal waters.
"We will be carefully monitoring reports over the next few weeks to see whether they return and there have been a couple of sightings but difficult to say yet what this means for the summer season."
Dr Evans added: "Last year, there was a shortage of sprats.
"We are not sure why, but it may have been related to oceanographic changes.
"We suspect that the minke whales shifted their distribution since minkes had a good summer further south in the Irish Sea as well as off eastern Scotland."
The charity's national whale and dolphin watch this year will be held from 12 to 20 August.