Climate‐induced seasonal changes in smallmouth bass growth rate potential at the southern range extent

Abstract

Temperature increases due to climate change over the coming century will likely affect smallmouth bass (Micropterus dolomieu) growth in lotic systems at the southern extent of their native range. However, the thermal response of a stream to warming climate conditions could be affected by the flow regime of each stream, mitigating the effects on smallmouth bass populations. We developed bioenergetics models to compare change in smallmouth bass growth rate potential (GRP) from present to future projected monthly stream temperatures across two flow regimes: runoff and groundwater-dominated. Seasonal differences in GRP between stream types were then compared. The models were developed for fourteen streams within the Ozark-Ouachita Interior Highlands in Arkansas, Oklahoma and Missouri, USA, which contain smallmouth bass. In our simulations, smallmouth bass mean GRP during summer months decreased by 0.005 g g −1 day −1 in runoff streams and 0.002 g g −1 day −1 in groundwater streams by the end of century. Mean GRP during winter, fall and early spring increased under future climate conditions within both stream types (e.g., 0.00019 g g −1 day −1 in runoff and 0.0014 g g −1 day −1 in groundwater streams in spring months). We found significant differences in change in GRP between runoff and groundwater streams in three seasons in end-ofcentury simulations (spring, summer and fall). Potential differences in stream temperature across flow regimes could be an important habitat component to consider when investigating effects of climate change as fishes from various flow regimes that are relatively close geographically could be affected differently by warming climate conditions. K E Y W O R D Sbioenergetics, climate change, growth rate potential, smallmouth bass, water temperature 1

Coldwater Periods in Warmwater Streams: Microhabitat Shifts from Autumn to Winter by Smallmouth Bass

“…Although we found that the selection of warmer waters during autumn is important to Smallmouth Bass, we acknowledge that cooler water facilitated by groundwater features is important during the warmer seasons (Brewer 2013b; Middaugh et al. ) and may also be important at other latitudes during winter or in especially cold years at this latitude (e.g., Westhoff et al. ).…”

Forecasting effects of angler harvest and climate change on smallmouth bass abundance at the southern edge of their range

“…Our simulations indicate that increases in drought frequency could strongly affect abundance of smallmouth bass in the Buffalo River. Previous work has documented a decline in body condition of smallmouth bass during summer months in some streams in the Ozark region, including the upper Buffalo River [ 50 ], and it is likely that increasing stream temperature due to climate change will decrease growth potential of smallmouth bass during summer months [ 28 ]. Drought conditions can stress fish and result in population declines [ 51 ].…”

“…We also assume that relationships between May temperature and June discharge and smallmouth bass recruitment will be the same in the future as during the period that data was collected. The Buffalo River is a runoff stream and other stream types, such as intermittent or groundwater dominated, could have different responses to climate change than runoff streams (e.g., temperature, [ 28 ]). Another simplifying assumption occurs in the way we model harvest mortality.…”

“…Precipitation patterns are likely to change seasonally and a decrease in precipitation is anticipated in the summer months [ 1 ], potentially leading to more severe and longer drought conditions [ 26 ]. At this southern range extent, smallmouth bass populations may be vulnerable to population declines due to climate change as summer temperatures will likely reach levels that will affect growth and survivorship [ 27 ]-[ 28 ], especially during summer drought conditions which are common in Arkansas streams and rivers [ 29 ]-[ 30 ]. Smallmouth bass are at risk of being outcompeted in some lotic habitats by largemouth bass and spotted bass, which both have a competitive advantage over smallmouth bass at higher temperatures [ 31 ].…”

Population Characteristics of Ozark Bass (<i>Ambloplites constellatus</i>) in the Upper White River Basin of Northern Arkansas

“…Climate change models for the southeastern United States predict an increase in the number and duration of droughts, greater mean annual air temperature, as well as an increased frequency of heavy rain events with shorter durations in the future [9]. The impacts of a potentially changing climate on Ozark bass populations are unknown at this time, but studies have suggested other sport fish may expand their habitat range and exhibit changes in growth rate potential [10].…”