Mottled sculpin in a dynamic landscape: Linking environmental heterogeneity, individual behaviors, and population dynamics in a southern Appalachian stream

Stream ecosystems are characterized by a high degree of spatial and temporal heterogeneity. I examined the effects of environmental heterogeneity on the foraging behaviors and population dynamics of a predatory benthic stream fish, the mottled sculpin (Cottus bairdi), in a southern Appalachian stream. Specifically, my research addressed two primary objectives: (1) to characterize the individual level response of mottled sculpin to prey patch dynamics; and (2) to link individual sculpin behaviors to sculpin population dynamics in a dynamic landscape. To characterize the individual level responses of mottled sculpin to resource heterogeneity, I compared the movement and foraging behaviors of sculpin with those expected of an organism foraging optimally in a patchy landscape. I obtained the following results from these analyses: (1) mottled sculpin exhibited two distinct movement behaviors, area restricted movements within resource patches (i.e., patch use) and directional movements between patches (i.e., patch abandonment); (2) adult sculpin focused their foraging activities within patches of high prey density and high prey colonization rates; (3) adult sculpin abandoned patches in response to a patch “giving up density” that was significantly lower than the average density of resources within patches available in the landscape; and (4) size-dependent social interactions among sculpin inhibited the ability of juvenile sculpin to utilize prey patches efficiently. To link individual sculpin behaviors to sculpin population dynamics in this system, I conducted an individual mark-recapture study of sculpin populations over a four-year period. I used these data to characterize habitat selection by individual sculpin and to characterize the spatio-temporal dynamics of sculpin populations. Habitat selection by sculpin was consistent with an “Ideal Despotic” model of habitat selection. Furthermore, habitat selection by sculpin and habitat-dependent survivorship of juveniles provided a mechanistic explanation for the relatively high spatial and temporal stability of sculpin populations observed in this system. Overall, the results of my research indicate that environmental heterogeneity in a southern Appalachian stream has important consequences for sculpin behaviors, demography, and population dynamics. Additional studies such as mine should enable researchers to elucidate the mechanistic linkages between environmental heterogeneity, individual behaviors, and population dynamics for stream fishes in other systems.