This study characterized spatial and temporal patterns associated with riverine broadcast spawning pygmy whitefısh (Prosopium coulterii) in tributaries of Chester Morse Lake (CML), near Seattle, Washington, from 2001 to 2012. In most years, fısh 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 whitefısh 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 fısh were captured and PIT tagged. Returning female pygmy whitefısh 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 whitefısh are most active under the cover of darkness. Thirteen fısh returned for a fıfth spawning migration and one individual was detected six years after initial tagging, demonstrating that pygmy whitefısh spawn in multiple years and that fısh can live to at least age nine in the CML population. These data represent the fırst attempt to investigate return frequency and other reproductive characteristics of riverine spawning pygmy whitefısh throughout their range, and supports the development of practical management techniques for this and similar riverine broadcast spawning species.
Vol. 88 • No. 2
Vol. 88 • No. 2