Long‐term persistence, density dependence and effects of climate change on rosyside dace (Cyprinidae)

Abstract

Summary We used long‐term population data for rosyside dace (Clinostomus funduloides), a numerically dominant member of a stochastically organised fish assemblage, to evaluate the relative importance of density‐dependent and density‐independent processes to population persistence. We also evaluated the potential impacts of global climate change (GCC) on this species and predicted how directional environmental changes will affect dace. We sampled two 30 m permanent sites in spring and autumn in the Coweeta catchment for rosyside dace density using three‐pass electrofishing between 1984 and 1995, and a single 100 m site from 1991 to 2003. Habitat availability and flow variation data for this 20‐year period demonstrated that two droughts (1985–1988 and 1999–2002) produced smaller wetted areas, lower mean, maximum and minimum flows, fewer high flow events and greater amounts of depositional substrata in the sites. Droughts produced significant increases in abundance, and significant decreases in standard length and mass of rosyside dace. Increases in abundance were mainly due to increased survival/immigration of young‐of‐the‐year (YOY). Model selection analysis using multiple single and multivariable models indicated that density dependence in various forms possessed substantial explanatory power with respect to long‐term variation in the per‐capita rate of increase (r) in all sites and seasons. Density‐dependent effects on r were stronger in autumn than spring, whereas negative density‐independent models (flow variation) had the greatest explanatory power in spring. Results for growth data were similar to those for rosyside dace density and confirm density dependence likely through intraspecific competition for food or foraging sites leading to reduced growth at higher densities. These data support the hypothesis that species may persist in stochastic animal assemblages via strong intraspecific density dependence. Greater flow variability or increased high flows produced by GCC may destabilise this population leading to reduced compensation and possibly eventual extinction.

Native brook trout and invasive rainbow trout respond differently to seasonal weather variation: Spawning timing matters

“…Flow‐driven control of trout populations will thus become more important under such climate conditions. For the Southern Appalachian Region, there is increasing evidence that variation in precipitation (Angert et al., ; Groisman et al., ; Laseter, Ford, Vose, & Swift, ), stream flow (Grossman, Sundin, & Ratajczak, ) and air temperatures is increasing (Ford, Laseter, Swank, & Vose, ), as are mean air temperatures (Ford et al., ). We also found that adult abundance of RBT is more responsive to seasonal weather variation than BKT adults.…”

“…() provided a graphical model that predicted GCC could tip Southern Appalachian stream fish populations from density‐dependent regulation to density‐independent control if the frequency of extreme events increases. The increases in variability and magnitude already are occurring (Grossman et al., ), and may ultimately lead to reduced compensatory responses by populations to deleterious environmental variation (e.g. floods and droughts) (Bassar, Letcher, Nislow, & Whiteley, ).…”

“…The observed range of each covariate is shown and represents annual mean values averaged across sites (Table S1) Brook trout Rainbow trout (Bassar, Letcher, Nislow, & Whiteley, 2016). Long-term studies of stream fish populations in the Southern Appalachians show that density-dependent regulation is common in these fishes including Southern BKT (Grossman et al, 2006(Grossman et al, , 2010(Grossman et al, , 2016, although density-independent influences such as flow variation also are present. Consequently, a shift in population control, and ultimately assemblage structure, produced by GCC is not an unlikely possibility.…”

Seasonal streamflow extremes are key drivers of Brook Trout young‐of‐the‐year abundance

“…For aquatic as well as terrestrial species, temporal variation in average annual and seasonal weather has been linked to changes in population abundance (Pardikes et al 2015, Kanno et al 2017, vital rates (Dybala et al 2013, Abadi et al 2017, and population dynamics (Seegrist and Gard 1972, Fern andez-Chac on et al 2011, Grossman et al 2016, Cleasby et al 2017. However, responses of animal populations may be more closely related to short-duration, high-magnitude extreme events or disturbances which exceed a biological threshold above or below which animals have reduced fitness (i.e., survival and reproductive success; Resh et al 1988, Lake 2003, Roland and Matter 2013, Childress and Letcher 2017.…”

Population dynamics of brown trout (Salmo trutta) in Spruce Creek Pennsylvania: A quarter‐century perspective

“…We used a multiple hypothesis testing procedure (Grossman, Sundin, & Ratajczak, ; Grossman et al., ) to examine the ability of multiple density‐dependent and density‐independent factors to represent the information content present in per‐capita rate of increase r = ln(density t 1 /density t ) data for the population (age 1 and adult densities combined), age 1 and adult age classes separately, annual growth data (both mean total length [mm] and mean mass [g]) and annual survival data. In brief, we constructed a set of biologically realistic linear regression models (Appendix S1) that included one or more of the following predictor variables: (1) population density, (2) age 1 density, (3) adult density, and (4) seasonal values on principle components one and two for each year for both temperature and flow data (see Grossman et al., , ). We also constructed a global model that included a majority of variables used in each analysis.…”