Abstract:We examined survival, competition, and recruitment among cyprinids that were subjected to interspecific and intraspecific competition and chronic heat stress in large, outdoor experimental streams. The study was conducted in 2011 during the hottest summer (also one of the driest summers) recorded in Texas. We measured survival of Red Shiners Cyprinella lutrensis, Blacktail Shiners Cyprinella venusta, and Central Stonerollers Campostoma anomalum stocked at varying densities to examine competitive interactions. … Show more
“…Grossman et al (2006) found that densitydependence models were the best predictors of abundance of insectivorous Mottled Sculpin Cottus bairdii. Dekar et al (2014) used stream mesocosms to evaluate intraspecific competition in omnivorous Blacktail Shiner Cyprinella venusta stocked at varying densities and found that an increase in diet breadth to include lower quality resources occurred in higher density treatments. While these two studies indicate density dependence is possible in nonsalmonid stream fish, it is not clear the degree to which this occurs in fishes from other tropic guilds and the impacts it may have on population regulation.…”
Herbivorous fish can have strong effects on stream ecosystem function by consuming primary producers and excreting limiting nutrients, but it is unclear whether they are resource limited. Thus, understanding factors regulating abundance of these fish might help predict ecosystem function. We used stream mesocosms to test whether populations of central stoneroller Campostoma anomalum exhibit density dependence across a range of typical densities and resource abundance found in Great Plains streams. We predicted that incrementally increasing stocking biomass from 3·7 to 24·9 g·m−2 would reduce standing stocks of resources resulting in lower growth of stocked fish. Fish growth (over 41 days) was compared to initial stocking biomass and primary production as well as standing stocks of algae and invertebrates using regression analysis. Mean growth of individuals was negatively associated with stocking biomass (Rnormaladj2 = 0·55; P = 0·02), as predicted. Contrary to our prediction, increases in fish biomass led to increased primary productivity (Rnormaladj2 = 0·31, P = 0·07), but resulted in no relationship among algal filament lengths (Rnormaladj2 = 0·00; P = 0·34), algal biomass (Rnormaladj2 = 0·12; P = 0·19) or invertebrate biomass (Rnormaladj2 = 0·03; P = 0·30). Thus, density dependence occurred without an apparent reduction in food resources. We hypothesised that stoneroller growth was possibly limited by competition for high‐quality algae or invertebrates, or behavioural interactions causing interference competition.
“…Grossman et al (2006) found that densitydependence models were the best predictors of abundance of insectivorous Mottled Sculpin Cottus bairdii. Dekar et al (2014) used stream mesocosms to evaluate intraspecific competition in omnivorous Blacktail Shiner Cyprinella venusta stocked at varying densities and found that an increase in diet breadth to include lower quality resources occurred in higher density treatments. While these two studies indicate density dependence is possible in nonsalmonid stream fish, it is not clear the degree to which this occurs in fishes from other tropic guilds and the impacts it may have on population regulation.…”
Herbivorous fish can have strong effects on stream ecosystem function by consuming primary producers and excreting limiting nutrients, but it is unclear whether they are resource limited. Thus, understanding factors regulating abundance of these fish might help predict ecosystem function. We used stream mesocosms to test whether populations of central stoneroller Campostoma anomalum exhibit density dependence across a range of typical densities and resource abundance found in Great Plains streams. We predicted that incrementally increasing stocking biomass from 3·7 to 24·9 g·m−2 would reduce standing stocks of resources resulting in lower growth of stocked fish. Fish growth (over 41 days) was compared to initial stocking biomass and primary production as well as standing stocks of algae and invertebrates using regression analysis. Mean growth of individuals was negatively associated with stocking biomass (Rnormaladj2 = 0·55; P = 0·02), as predicted. Contrary to our prediction, increases in fish biomass led to increased primary productivity (Rnormaladj2 = 0·31, P = 0·07), but resulted in no relationship among algal filament lengths (Rnormaladj2 = 0·00; P = 0·34), algal biomass (Rnormaladj2 = 0·12; P = 0·19) or invertebrate biomass (Rnormaladj2 = 0·03; P = 0·30). Thus, density dependence occurred without an apparent reduction in food resources. We hypothesised that stoneroller growth was possibly limited by competition for high‐quality algae or invertebrates, or behavioural interactions causing interference competition.
“…The red shiner is an invasive species that has rapidly expanded its range throughout North America (Mapping the potential distribution of the invasive Red Shiner, Cyprinella lutrensis (Teleostei: Cyprinidae) across waterways of the conterminous United States). Red shiners thrive in waters varying widely in available light spectra, with mean of yearly median habitat turbidity measures ranging from 10 to 140 nephelometric turbidity units (NTU) and withstand temperatures ranging from 0°C-37°C (Dekar et al, 2014; Dugas and Franssen, 2012; Matthews, 1986; Matthews and Hill, 1977). Visual signaling is an important part of the biology of red shiners, with males displaying elaborate nuptial coloration (Dugas and Franssen, 2011).…”
The light environment underwater can vary dramatically over space and time, challenging the visual systems of aquatic organisms. To meet these challenges, many species shift their spectral sensitivities through changes in visual pigment chromophore and opsin expression. The red shiner (Cyprinella lutrensis) is a cyprinid minnow species that has rapidly expanded its range throughout North America and inhabits a wide range of aquatic habitats. We hypothesized that visual system plasticity has contributed to the red shiner's success. We investigated plasticity in chromophore usage and opsin expression by collecting red shiners from three Oklahoma creeks that vary in turbidity throughout the year. We characterized the light environment by spectroradiometry, measured chromophore composition of the eyes with high performance liquid chromatography, characterized CYP27C1 enzyme function through heterologous expression, and examined ocular gene expression by RNA sequencing and de novo transcriptome assembly. We observed significantly higher proportions of the long-wavelength shifted A2 chromophore in the eyes of fish from the turbid site and in samples collected in winter, suggesting that there may be a temperature-dependent trade-off between chromophore-based spectral tuning and chromophore-related noise. Opsin expression varied between turbid and clear creeks, but did not align with light environment as expected, and the magnitude of these differences was limited compared to the differences in chromophore composition. We confirmed that red shiner CYP27C1 catalyzes the conversion of A1 to A2, but the ocular expression of CYP27C1 was not well correlated with A2 levels in the eye, suggesting conversion may be occurring outside of the eye.
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