Characteristics of Riverine Broadcast Spawning Pygmy Whitefısh (Prosopium coulterii)

Abstract This study characterized spatial and temporal patterns associated with riverine broadcast spawning pygmy whitefish (Prosopium coulterii) in tributaries of Chester Morse Lake (CML), near Seattle, Washington, from 2001 to 2012. In most years, fish spawned in a narrow linear reach of riverine habitat from 2.0 to 3.0 km upstream of CML within a two week period. Individual characteristics of spawning pygmy whitefish were investigated through the use of mark-recapture efforts and a PIT (passive integrated transponder) tag antenna array. During the latter years of the study (2006–2011), a total of 3,012 fish were captured and PIT tagged. Returning female pygmy whitefish spent less time in the river (mean 2.4 days, SD 3.1) than males (mean 5.9 days, SD 2.4). In addition, 91% of all movements occurred between 1700 and 0700 during nighttime hours suggesting that spawning pygmy whitefish are most active under the cover of darkness. Thirteen fish returned for a fifth spawning migration and one individual was...