Investigating Impacts of Low Flow on Fountain Darter Reproduction
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Effects of low flow on Fountain
Effects of low flow on Fountain
Darter fecundity
Darter fecundity
Background
Background
Fountain Darters
Fountain Darters
(Schenck and Whiteside 1977)
(Schenck and Whiteside 1977)
–
Spawn year round based on presence of “ova”
Spawn year round based on presence of “ova”
–
Two peaks: Aug and Jan – Apr
Two peaks: Aug and Jan – Apr
Warmer water temperatures (>23)?
Warmer water temperatures (>23)?
Decreases in flow (<200 cfs)?
Decreases in flow (<200 cfs)?
Background
Background
Background
Background
Spring-associated fishes spawning
Spring-associated fishes spawning
Photoperiod initiates
Photoperiod initiates
Temperature stops
Temperature stops
Plenty of unexplained variation
Plenty of unexplained variation
Questions?
Questions?
Effects of low flow on Fountain Darter
Effects of low flow on Fountain Darter
reproduction?
reproduction?
–
Flow is likely not a proximate cue for
Flow is likely not a proximate cue for
spawning
spawning
–
However, flow is a “master variable”
However, flow is a “master variable”
Physical, chemical, and biological environments
Physical, chemical, and biological environments
Difficult to test in laboratory setting
Difficult to test in laboratory setting
Reproduction:
Reproduction:
–
Related to flow?
Related to flow?
–
Related to vegetative structure?
Related to vegetative structure?
Methodology
Methodology
Fish will be collected:
Fish will be collected:
–
monthly from Jan – Aug (Dec)
monthly from Jan – Aug (Dec)
–
from 4 locations (5 to 120 cfs)
from 4 locations (5 to 120 cfs)
–
from three vegetation types (tall, short, no)
from three vegetation types (tall, short, no)
Methodology
Methodology
Laboratory:
Laboratory:
–
Fish measured (wt, eviscerated wt, TL)
Fish measured (wt, eviscerated wt, TL)
–
Ovary status (I, D, M, S)
Ovary status (I, D, M, S)
–
Oocytes status
Oocytes status
D. C. Heins, Tulane U.
Analyses and Outcomes
Analyses and Outcomes
ANOVA (cfs, vegetation type)
ANOVA (cfs, vegetation type)
–
Covariates: time and potentially other factors
Covariates: time and potentially other factors
Refinement of year-round spawning
Refinement of year-round spawning
Effects along a flow gradient
Effects along a flow gradient
Effects of vegetation
Effects of vegetation
Effects of predation on fountain
Effects of predation on fountain
darter population size at various
darter population size at various
flow rates
flow rates
Piscivorous fishes:
Piscivorous fishes:
Predation varies
Predation varies
(Schlosser and Ebel 1989)
(Schlosser and Ebel 1989)
:
:
–
Temporally, dependent of flow regime
Temporally, dependent of flow regime
–
Spatially, dependent on habitat
Spatially, dependent on habitat
Average flows: predation on Fountain
Average flows: predation on Fountain
Darters is low
Darters is low
(BIO-WEST 2002)
(BIO-WEST 2002)
–
3 darters out of 437 potential predators
3 darters out of 437 potential predators
–
3 darters out of 126 confirmed predators
3 darters out of 126 confirmed predators
San Marcos River
San Marcos River
(BIO-West 2006)
(BIO-West 2006)
<100 cfs
<100 cfs
–
consumption not detected
consumption not detected
<<100 cfs
<<100 cfs
Increase predation likely, decimation of
Increase predation likely, decimation of
potential and confirmed fish predators?
potential and confirmed fish predators?
Trophic cascade:
Trophic cascade:
Rahel and Stein 1988, Taylor and Soucek 2010, Thomas 2011
Questions?
Questions?
Numbers of darters consumed by…?
Numbers of darters consumed by…?
–
Crayfish only
Crayfish only
–
Largemouth Bass only
Largemouth Bass only
–
Crayfish & bass
Crayfish & bass
Does vegetation mediate the response?
Does vegetation mediate the response?
Methods
Methods
Laboratory setting (FAB)
Laboratory setting (FAB)
Phase 1: Observational studies
Phase 1: Observational studies
–
Numbers of prey and predators, amount of
Numbers of prey and predators, amount of
vegetation, exposure time
vegetation, exposure time
Methods
Methods
Phase 2:
Phase 2:
–
Predictions:
Predictions:
Consumption
Consumption
(crayfish)
(crayfish)
> Consumption
> Consumption
(bass)
(bass)
>
>
Consumption
Consumption
(bass x crayfish)
(bass x crayfish)
Consumption
Consumption
(bare)
(bare)
> Consumption
> Consumption
(vegetation)
(vegetation)
Experimental design
Experimental design
Completely randomized design
Completely randomized design
Experimental unit = aquarium with darters
Experimental unit = aquarium with darters
TRT:
TRT:
1: no pred, cray, bass, cray & bass
1: no pred, cray, bass, cray & bass
2: veg/bare
2: veg/bare
Experimental design
Experimental design
Replication: 3
Replication: 3
2-factor ANOVA (
2-factor ANOVA (
α = 0.05) with Fisher’s
α = 0.05) with Fisher’s
LSD
LSD
Research delves into the effects of low flow on Fountain Darter fecundity, highlighting the species' spawning behaviors in response to water flow variations and how it relates to reproductive success. The study aims to refine understanding of year-round spawning patterns, analyze the influence of flow gradients and vegetation types, and evaluate the role of physical, chemical, and biological factors in the reproductive ecology of Fountain Darters.
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Presentation Transcript
Effects of low flow on Fountain Darter fecundity
Background Fountain Darters (Schenck and Whiteside 1977) Spawn year round based on presence of ova Two peaks: Aug and Jan Apr Warmer water temperatures (>23)? Decreases in flow (<200 cfs)?
Spring-associated fishes spawning Photoperiod initiates Temperature stops Plenty of unexplained variation
Questions? Effects of low flow on Fountain Darter reproduction? Flow is likely not a proximate cue for spawning However, flow is a master variable Physical, chemical, and biological environments Difficult to test in laboratory setting
Reproduction: Related to flow? Related to vegetative structure?
Methodology Fish will be collected: monthly from Jan Aug (Dec) from 4 locations (5 to 120 cfs) from three vegetation types (tall, short, no)
Methodology Laboratory: Fish measured (wt, eviscerated wt, TL) Ovary status (I, D, M, S) Oocytes status D. C. Heins, Tulane U.
Analyses and Outcomes ANOVA (cfs, vegetation type) Covariates: time and potentially other factors Refinement of year-round spawning Effects along a flow gradient Effects of vegetation
Effects of predation on fountain darter population size at various flow rates ubparvipinne4.jpg
Piscivorous fishes: Predation varies (Schlosser and Ebel 1989): Temporally, dependent of flow regime Spatially, dependent on habitat Average flows: predation on Fountain Darters is low (BIO-WEST 2002) 3 darters out of 437 potential predators 3 darters out of 126 confirmed predators
San Marcos River (BIO-West 2006) <100 cfs consumption not detected <<100 cfs Increase predation likely, decimation of potential and confirmed fish predators?
Trophic cascade: Rahel and Stein 1988, Taylor and Soucek 2010, Thomas 2011
Questions? Numbers of darters consumed by ? Crayfish only Largemouth Bass only Crayfish & bass Does vegetation mediate the response?
Methods Laboratory setting (FAB) Phase 1: Observational studies Numbers of prey and predators, amount of vegetation, exposure time
Methods Phase 2: Predictions: Consumption (crayfish) > Consumption (bass) > Consumption (bass x crayfish) Consumption (bare) > Consumption (vegetation)
Experimental design Completely randomized design Experimental unit = aquarium with darters TRT: 1: no pred, cray, bass, cray & bass 2: veg/bare
Experimental design Replication: 3 2-factor ANOVA ( = 0.05) with Fisher s LSD
