title: Robust estimates of environmental effects on population vital rates: an integrated capture-recapture model of seasonal brook trout growth, survival and movement in a stream network.
abstract: Modelling the effects of environmental change on populations is a key challenge for ecologists, particularly as the pace of change increases. Currently, modelling efforts are limited by difficulties in establishing robust relationships between environmental drivers and population responses. We developed an integrated capture-recapture state-space model to estimate the effects of two key environmental drivers (stream flow and temperature) on demographic rates (body growth, movement and survival) using a long-term (11 years), high-resolution (individually tagged, sampled seasonally) data set of brook trout (Salvelinus fontinalis) from four sites in a stream network. Our integrated model provides an effective context within which to estimate environmental driver effects because it takes full advantage of data by estimating (latent) state values for missing observations, because it propagates uncertainty among model components and because it accounts for the major demographic rates and interactions that contribute to annual survival. We found that stream flow and temperature had strong effects on brook trout demography. Some effects, such as reduction in survival associated with low stream flow and high temperature during the summer season, were consistent across sites and age classes, suggesting that they may serve as robust indicators of vulnerability to environmental change. Other survival effects varied across ages, sites and seasons, indicating that flow and temperature may not be the primary drivers of survival in those cases. Flow and temperature also affected body growth rates; these responses were consistent across sites but differed dramatically between age classes and seasons. Finally, we found that tributary and mainstem sites responded differently to variation in flow and temperature. Annual survival (combination of survival and body growth across seasons) was insensitive to body growth and was most sensitive to flow (positive) and temperature (negative) in the summer and fall. These observations, combined with our ability to estimate the occurrence, magnitude and direction of fish movement between these habitat types, indicated that heterogeneity in response may provide a mechanism providing potential resilience to environmental change. Given that the challenges we faced in our study are likely to be common to many intensive data sets, the integrated modelling approach could be generally applicable and useful.
authors.affiliation: S.O. Conte Anadromous Fish Research Center, US Geological Survey/Leetown Science Center, Turners Falls, MA, 01376, USA.
authors.forename: Benjamin H
authors.initials: BH
authors.lastname: Letcher
authors.affiliation: S.O. Conte Anadromous Fish Research Center, US Geological Survey/Leetown Science Center, Turners Falls, MA, 01376, USA.|Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA, 01003-4210, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Schueller
authors.affiliation: S.O. Conte Anadromous Fish Research Center, US Geological Survey/Leetown Science Center, Turners Falls, MA, 01376, USA.
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Bassar
authors.affiliation: Northern Research Station, USDA Forest Service, University of Massachusetts, Amherst, MA, 01003-4210, USA.
authors.forename: Keith H
authors.initials: KH
authors.lastname: Nislow
authors.affiliation: Northern Research Station, USDA Forest Service, University of Massachusetts, Amherst, MA, 01003-4210, USA.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Coombs
authors.affiliation: S.O. Conte Anadromous Fish Research Center, US Geological Survey/Leetown Science Center, Turners Falls, MA, 01376, USA.|Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA, 01003-4210, USA.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Sakrejda
authors.affiliation: S.O. Conte Anadromous Fish Research Center, US Geological Survey/Leetown Science Center, Turners Falls, MA, 01376, USA.|School of Biology, Biomedical Sciences Research Complex University of St Andrews, St Andrews, Fife KY16 9ST, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Morrissey
authors.affiliation: S.O. Conte Anadromous Fish Research Center, US Geological Survey/Leetown Science Center, Turners Falls, MA, 01376, USA.
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Sigourney
authors.affiliation: Department of Environmental Conservation, University of Massachusetts, Amherst, MA, 01003-4210, USA.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Whiteley
authors.affiliation: S.O. Conte Anadromous Fish Research Center, US Geological Survey/Leetown Science Center, Turners Falls, MA, 01376, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: O'Donnell
authors.affiliation: S.O. Conte Anadromous Fish Research Center, US Geological Survey/Leetown Science Center, Turners Falls, MA, 01376, USA.
authors.forename: Todd L
authors.initials: TL
authors.lastname: Dubreuil
mesh_terms: D000367:Age Factors; D000818:Animals; D003710:Demography; D017753:Ecosystem; D008962:Models, Theoretical; D011157:Population Dynamics; D045483:Rivers; D012621:Seasons; D013696:Temperature; D014337:Trout / Q000254:growth & development / Q000502:physiology*; D014872:Water Movements
keywords: Bayesian modelling; annual survival; capture–mark–recapture; integrated model; movement; sensitivity; stream fish; stream network; survival