Mainer,
In addition to the BT performing better in less turbid water, similar observations of various other species have also been reported.
Any loss of clarity will work against spotting prey as it shortens visual reach. In theory this will reduce the number of encounters and opportunities for predatory attempts. When loss of clarity is caused by the production of phytoplankton, however, the enhanced food chain can produce more opportunities by supporting greater populations of prey. Muddy water, on the other hand, is a double whammy. It reduces production at the bottom of the food chain and shortens visual reach. So its harder to find the consequent lower populations of prey.
Too much weed coverage can also increase search times. The authors discussion around increased search times in turbid water reducing rest/handling periods makes a lot of sense to me.
