Ecological performance of native and invasive benthic freshwater fishes under elevated temperature
Creators: name: Ricciardi, Anthony
name: Hutchings, Megan
name: Hill, Jaclyn
name: Windle, Matthew
Publisher: name: Zenodo
Year: 2025
Subjects: Climate change
Critical thermal maximum
functional response
Invasive species
temperature tolerance

description: Climate warming of freshwater ecosystems is altering the performance and trophic interactions of native and non-native species. We compared the feeding efficiency and thermal tolerance of the Eurasian round goby (Neogobius melanostomus) and a trophically analogous native species, logperch (Percina caprodes), under current and projected mean summer surface temperatures for the nearshore lower Great Lakes (18°C and 25°C, respectively). At both temperatures, we quantified the functional response ratio (FRR) of these fishes—the ratio of their attack rate and prey handling time, which can predict trophic impacts in the field. At 18°C, juvenile logperch had a higher FRR than juvenile round gobies; however, adult round gobies had a higher FRR than logperch at either temperature, indicating a greater potential for trophic impacts. At 25°C, adult round gobies and logperch increased their prey consumption and FRR. Following acclimation to 18°C and 25°C, juvenile logperch exhibited a greater thermal acclimation capacity than the round goby. These results underscore the need for risk assessment to account for varied responses by native and non-native species to shifting thermal contexts.
description: Funding provided by: Natural Sciences and Engineering Research CouncilROR ID: https://ror.org/01h531d29Award Number:
description: Quantifying Habitat Temperatures

Water temperature data for the upper St. Lawrence River were obtained from Melocheville, Quebec (45.319° N, 73.927° W), and Maitland, Ontario (44.635° N, 75.613° W),  and used as approximations for collection sites at Beauharnois and Morrisburg, respectively. Data from Melocheville was obtained in the summer of 2020 from Reid and Ricciardi (2022) using a temperature logger that recorded water temperatures once per hour. Water temperature data from Maitland was retrieved during the summer of 2022 from the St. Lawrence River Institute using a temperature logger that recorded water temperatures at 15-minute intervals. For each location, mean daily temperatures were calculated for each 24-hour period from 16 July to 30 September 2022. The mean daily temperatures of Melocheville and Maitland were 22.3±0.30°C (17.2–34.0°C, min-max) and 22.6±0.23°C (16.0–27.3°C, min-max), respectively (Fig. 2). The number of days ≥25°C were 6 for Melocheville and 2 for Maitland.

Comparative Functional Responses

We examined the comparative FR of juvenile logperch and both adult and juvenile round gobies at two acclimation temperatures, 18°C and 25°C, which were selected to represent mean maximum nearshore surface water temperatures at present and in the latter half of this century, respectively, for nearshore lakes Erie and Ontario (Trumpickas et al., 2009, 2015). Both species and life stages were provided with a 2-week temperature acclimation before FR trials began, with the exception of logperch acclimated to 18°C. Logperch were provided with an additional 14 days of acclimation at 18°C to stabilize water quality (Yao et al., 2020; Saeed et al., 2022). At the start of FR trials, individuals were isolated in a 10-gallon aquarium (50 × 19 × 25 cm) and left to acclimate for a 24-hour period, during which they were starved to standardize hunger levels (Mofu et al., 2019a; Reid & Ricciardi, 2022). The sides of aquaria were covered with an opaque barrier to prevent external visual stimuli from affecting prey consumption (Murray et al., 2013). Each experimental aquarium was maintained at the corresponding acclimation temperature (± 0.5°C). Aquaria also contained an air stone for oxygenation and a shelter (PVC pipe) as refuge to reduce stress.

Prey items used in the FR trials were chironomid (Chironomus sp.) larvae, which are typically found in habitats occupied by logperch and round gobies and are a common component of their diets (French & Jude, 2001; Kornis et al., 2012). Hikari chironomid larvae (previously frozen and subsequently thawed for experiments) were distributed in seven densities (n=2, 4, 8, 16, 32, 64, and 140 larvae for logperch and juvenile round gobies; n=2, 4, 8, 16, 32, 64, 180 larvae for adult round gobies) with four replicates per density. Within each series of 18ºC and 25 ºC temperature experiments, following the 24-hour trial acclimation period, each individual fish was used in one feeding trial (i.e., at one prey density assigned at random) and allowed to feed for three hours (Mofu et al., 2019a; Mofu et al., 2019b). The use of lower prey densities enables us to distinguish between Type II and Type III functional responses (Juliano, 2001). At the end of each FR trial, individuals were removed from their experimental tank, weighed, and measured for total length. The remaining chironomid larvae were collected and counted to identify the number of prey eaten (Mofu et al., 2019a). Control trials without fish were conducted at each prey density to confirm that the observed depletion of prey from the experimental tanks was a direct result of predation.

Critical Thermal Maximum

CTmax was measured in a 38-L aquarium (50 × 19 × 25 cm) at acclimation temperatures of 18°C and 25°C. Individuals were acclimated to each temperature treatment for 4–6 weeks prior to trials. A total of 12 logperch and 12 juvenile round gobies were tested per acclimation temperature, while 10 adult round gobies were tested at 18°C and 9 individuals were tested at 25°C (McDonnell & Chapman, 2015; Reid & Ricciardi, 2022). Size-matching based on total length was conducted within all groups and between logperch and juvenile round gobies. The experimental aquarium was equipped with an aerator for oxygenation, and an isolating breeding box containing gravel and a PVC shelter to decrease stress and offer refugia. For logperch and juvenile round gobies, two individuals from the same rearing tank were placed in separate chambers of the breeding box (25 × 14 × 15 cm) divided using an opaque barrier. Adult round gobies were tested in their own individual breeding box (26 × 15 × 16 cm). Logperch used in CTmax trials were the same individuals used for FR trials. CTmax trials were conducted after completing FR experiments and each fish was given a minimum of seven days between experimental trials for recovery (Reid & Ricciardi, 2022). Fish were not reused among CTmax experiments.

Prior to the start of each trial, fish were starved for a 24-hr period (McDonnell & Chapman, 2015; Wells et al., 2016). The experimental aquarium was maintained at the corresponding acclimation temperature (± 0.5°C). Fish were placed in the breeding box and left to acclimate for two hours while the CTmax apparatus circulated water so individuals could recover from handling stress and acclimate to trial conditions (Potts et al., 2021; Reid & Ricciardi, 2022). Water temperature within the experimental aquarium was controlled by a heating immersion circulator (Julabo CORIOTM, Seelbach, Germany). At the start of each trial, the water temperature was increased at a fixed rate of 0.3°C/min (Becker & Genoway, 1979) and monitored and recorded for the duration of each trial. Fish were exposed to increasing water temperature until they displayed a loss of equilibrium (Becker & Genoway, 1979), at which point the end temperature (CTmax) was recorded. Loss of equilibrium for round gobies was determined manually since this species lacks a swim bladder (Kornis & Vander Zanden, 2010). When individuals began to show signs of increased breathing rates and reduced movement, a probe was used to gently turn the fish over (Matern, 2001). If fish were unable to re-orient themselves after five seconds, they were considered to have lost equilibrium (Carline & Machung, 2001). Immediately following loss of equilibrium, fish were transferred into a recovery aquarium, containing an aerator, and monitored. Once recovered, the total length and weight were recorded, and any mortality was noted.

A time-stamped webcam monitored fish behaviour during trials to reduce disturbance. The footage was reviewed to confirm the onset of behavioural thresholds; CTmax and agitation temperature (Tag). Tag was identified as the temperature at which a fish swims agitatedly around the breeding box for a period longer than 40 seconds, indicating the onset of avoidance behaviour before CTmax is reached (McDonnell & Chapman, 2015; Potts et al., 2021). This avoidance behaviour is indicative of the threshold at which fish seek out a cooler environment (McDonnell & Chapman, 2015; Wells et al., 2016). Additional metrics were derived using CTmax and Tag values and compared between acclimation treatments. First, the thermal agitation window (Taw) was calculated by subtracting Tag from CTmax (Wells et al., 2016). The acclimation agitation window (Aaw) was calculated by subtracting the acclimation temperature from Tag (McDonnell et al., 2021). The modified thermal safety margin (TSM) was calculated by subtracting the acclimation temperature from CTmax (McArley et al., 2017; McDonnell et al., 2021). Lastly, the acclimation response ratio (ARR), a metric for quantifying thermal plasticity, was calculated as the change in CTmax per degree change in the acclimation temperature (Tacc) for both acclimation treatments (Claussen, 1977).