Nighttime release of acoustically tagged VAMP fish

May 6 marked the fifth release of acoustically tagged VAMP fish. The USFWS transported the juvenile Chinook to containers at Durham Ferry the day prior to release so they would have adequate time to acclimate to the water temperature, and recover from the surgical implantation of acoustic transmitters. After dark, three USFWS biologists slowly transported the containers into moderate current, where the fish were released.

The HTI acoustic transmitters weigh 0.65 grams. The tags transmit acoustic wave signals that are picked up by hydrophones downstream for about a month, until the batteries die.