Tools from Behavioral Ecology Increase Explanatory Power for Fish Habitat Selection

Biological interactions have important consequences for habitat selection, but are time-intensive and often left unaddressed. Approaches from behavioral ecology can describe habitat selection in more detail when such responses need to be considered.  In a tidal creek/estuary system, benthic, euryhaline freshwater cottids exploit high productivity in the estuary as juveniles. Use of the estuary by juvenile coastrange sculpin was limited by competition from prickly sculpin and by the Pacific staghorn sculpin, a highly predatory marine, cottid.  The foraging/predation-risk trade-off, a key concept in behavioral ecology explained habitat selection behavior in this study system for both the coastrange sculpin and the sharpnose sculpin.  Predation risk was also a strong factor affecting the distribution of prickly sculpin in the near-shore habitat of an oligotrophic lake in the Cascade Mountains (Washington, USA).  Adult prickly sculpin can be cannibalistic on young of the year and a time series of data showed the consistent reduction in the presence of juveniles with increasing predation risk. A second prediction from behavioral ecology is that the foraging/predation-risk trade-off can have non-lethal effects on individuals.  This is reflected in reduced variability in the energetic condition among individuals in the population as the strength of the trade-off increases. Both study systems above demonstrated this response.  Finally, consideration of growth and behavior has been important in determining the response of juvenile salmonids to in-stream habitat restoration in the Interior Columbia River Basin. Although Chinook salmon and steelhead trout responded numerically to the placement of log or rock structures to augment stream rearing habitat, differences in density between treated and untreated habitats do not guarantee that population productivity has increased. Assays of growth under the difference in density between treated and untreated microhabitats definitively showed that steelhead grew 1.5 times better in treated microhabitats although performance did not always track density.  Mark-recapture analysis of habitat affinity showed that both Chinook salmon and steelhead had greater short-term fidelity to treated microhabitats than to untreated microhabitats. In the case of Chinook salmon, habitat affinity data supported the consistently higher density at treated microhabitats compared to those without structures. Steelhead trout had inconsistent patterns in abundance, but both behavior and growth studies showed a benefit to the selection of microhabitats with structures. Thus, limiting studies to patterns of distribution and relative abundance may be insufficient to determine whether fish show conclusive habitat preferences.