PNNL

Abstract

When fishes undertake juvenile migration, mortality experienced along the route is a major determinant of population success. Use of electronic telemetry tags to assess survival in small, slender bodied taxa has proven elusive in the absence of suitable micro-transmitters. We conducted a field study and model analysis of survival estimation in seaward migrating juvenile sea lamprey (Petromyzon marinus) using a new micro-acoustic telemetry tag. Data were generated from an array of eight receivers across a coastal riverine-wetland-lake complex for 56 migrants. Consistent with adult landward migratory behavior, juveniles initiated seaward movement near nautical twilight and were more likely to move on nights of high river discharge, resulting in a protracted migratory period. Estimated survival was highest in the riverine reach, appearing to decline through the river-wetland complex before falling precipitously in the drowned rivermouth lake. However, the high transmission frequency and short battery life likely resulted in missed detections in the lower reaches. Simulation models suggest remedies to the tradeoff between battery life and detection probability may be managed by increasing sample size, spatially stratifying release locations, and use of survival estimation models that explicitly account for spatially and temporally varying survival rates. We offer practical recommendations for use of the ELAT transmitter in field studies with small anguilliform fishes.