It was stated somewhere that one of the searches was bloodhounds.
ETA: Found it. This indicates 3 dog searches total, 2 with bloodhounds..
Here it is:
http://www.websleuths.com/forums/showpost.php?p=9830539&postcount=661
From dragracerz on Thurs, 9/12:
"The initial dog search revealed the the scent went from the car to the water, nothing else, but that places Bryce at Castaic
Another dog search with bloodhounds on Tuesday showed Bryce by the waters edge but going along the shore towards the dam
Yesterdays bloodhound search picked up scents possibly leading out of the park so it is hopeful that he is trying to still get home to Laguna however might be impaired due to a head injury.
I think the search of the water itself is over and LE has concluded that he is NOT in the lake but also thinking he might be trying to head towards Laguna"