Habitat affinity and density‐dependent movement as indicators of fish habitat restoration efficacy

Abstract

Conceptual and methodological tools from behavioral ecology can inform studies of habitat quality, and their potential for evaluating habitat restoration in conservation efforts is explored here. Such approaches provide mechanistic detail in understanding the relationship between organisms and their habitats and are thus more informative than correlations between density and habitat characteristics. Several Pacific salmon species have been the target of habitat restoration efforts for the past 2-3 decades, but most post-restoration effectiveness studies have been limited to correlative data described above. In mark-recapture assays from four different study years, the affinity of sub-yearling Chinook salmon (Oncorhynchus tschawytscha) and steelhead (O. mykiss) for stream pools restored with or created by engineered log structures was greater than that for pools without restoration, though with high interannual variability. From corresponding distribution and density data, it was clear that habitat affinity data are not always concordant with single observations of density. The same was true of the correlation between either affinity or density and physical characteristics of pools, although depth and current velocity had some explanatory power for both responses in Chinook. Movement into pools by Chinook during the assays indicated that restored pools can support more immigrants at a given density than can unrestored pools; however, no such pattern emerged for steelhead. Variation among individuals in body condition has implications for population-wide fitness, and such low variation was correlated with stronger affinity for pools in Chinook regardless of restoration status. This suggests that pools may mediate habitat-related trade-offs and that restoring them might have a positive effect on fitness. Thus affinity, immigration, and condition data give much-needed mechanistic indication of habitat selection for restored habitat via an apparent capacity increase and those potential fitness benefits. This is stronger support for restoration effectiveness than density differences alone because density data (1) may simply indicate redistribution of fish from poor to good habitats and (2) are not adequate to show correlations between restoration and positive change in traits correlated with fitness.

Trends in Geographic Sensitivity of Marine Fishes Over Decades in the North Sea

“…The AAM affects growth rate and generation time and determines proliferation capability (Lester et al, 2004;Minte-Vera et al, 2016;Honsey et al, 2017). The HA influences species' site (in) fidelity, mobility and habitat requirements and thus the emigration of species (Carrasco et al, 2017;Sequeira et al, 2018;Polivka, 2020). Species with larger DRs and LRs are expected to physiologically tolerate a wider range of climate variation, which ultimately aids in establishment and colonization (Sunday et al, 2011).…”

“…Moreover, traits corresponding to dispersal ability would enable species to colonize newly suitable environments (Guha et al, 2013;McCauley et al, 2015). Despite traits being valuable evidencebased tools for conservation and management (Estrada et al, 2016;MacLean and Beissinger, 2017;Sequeira et al, 2018;Polivka, 2020), empirical evidence on the links between species' traits and long-term geographical interactions in specific areas remains limited.…”

Summer stream habitat preferences of Nunavik anadromous Arctic char (Salvelinus alpinus) fry and parr

“…The present study aims to describe habitat use and attempts to model habitat preferences of Arctic char fry and parr at three different spatial scales in Nunavik (Canada) river systems. As the fitness of population is correlated to the size of fish and its variability is linked to habitat affinity (Polivka 2020), the relationship between the size of juveniles and specific habitats was also investigated.…”

Nowhere to hide: The importance of instream cover for stream‐living Coastal Cutthroat Trout during seasonal low flow

“…To evaluate the selection of stream features providing concealment, we used a resource selection approach (Manly et al, 2002;Polivka, 2020). In addition to cover itself, we evaluated how selection of cover may be conditioned on availability of deep water for potential refuge, which could influence the importance of cover to fish (Power, 1984(Power, , 1987.…”

“…Although it is difficult to identify the exact purpose of an expressed behaviour (Rosenblueth et al, 1943), it is useful to identify behavioural responses because of their implications for individual fitness and population processes. Accordingly, a better understanding of individual behaviour can help to identify details of how species can respond to changing environmental conditions (Beever et al, 2017;Berger-Tal et al, 2011) and how restoration of instream cover influences fish (Polivka, 2020).…”