PARENT SESSION
Contributed Oral Session 22: Fish Habitat Structure and Movement
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 514 A, Level 5, Palais des congrès de Montréal

Choosing to be lazy: Movement and gene flow in an actively sedentary stream fish, Cottus bairdi.

Lamphere, Bradley^*,1, ¹ UNC- Chapel Hill, Chapel Hill, NC

ABSTRACT- The cues to and extent of individual movements constitute vital determinants of population dynamics, but the difficulty of observing long moves in the field has limited ecological studies of mobile species. Nonmigratory stream fish often exhibit relatively restricted movement, making them a useful model taxon for studies of mobility. I used observational, experimental, and genetic approaches to assess movement in the mottled sculpin, Cottus bairdi, a stream fish with notably restricted dispersal, over multiple spatial and temporal scales. Observational and experimental data demonstrated that C. bairdi use conspecific density as a direct cue to reach-scale (20-160 m) movement, even though C. bairdi use prey density as the proximal cue to fine-scale (<2 m) moves. Mark-recapture surveys showed that C. bairdi moved substantial distances (>20 m) more often than previous work indicated and that the correlates of movement changed seasonally. C. bairdi moved to sites with high conspecific density in summer and away from them in the spring breeding season. Field manipulations of C. bairdi density confirmed that C. bairdi used conspecific density as a direct cue to aggregate in summer. The aggregation probably resulted from C. bairdi using conspecifics as indicators of good foraging habitat, a process known as habitat copying. Microsatellite DNA samples from C. bairdi over 5.3 km of stream length showed strong isolation-by-distance, with significant differences between locations less than 1 km apart. However, the gene flow inferred from the genetic data still exceeded that implied by the mark-recapture data. Thus, these data strongly indicate that, while C. bairdi are exceptionally sedentary under most circumstances, they can respond to movement cues over significant distances and in a complex manner. Together with existing fine-grained data, the direct and indirect measures of movement in this study form a multi-scale view of movement from the patch to the population scale.

Key words: movement, Cottus bairdi, genetics, stream fish