1. Effects of low flow on Fountain Darter fecundity

2. Background Fountain Darters (Schenck and Whiteside 1977) 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)?

4. Background

5. Background

6. Spring-associated fishes spawning Photoperiod initiates Photoperiod initiates Temperature stops Temperature stops Plenty of unexplained variation Plenty of unexplained variation

7. Questions? Effects of low flow on Fountain Darter reproduction? 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

9. Reproduction: Reproduction: –Related to flow? –Related to vegetative structure?

10. Methodology Fish will be collected: Fish will be collected: –monthly from Jan – Aug (Dec) –from 4 locations (5 to 120 cfs) –from three vegetation types (tall, short, no)

11. Methodology Laboratory: Laboratory: –Fish measured (wt, eviscerated wt, TL) –Ovary status (I, D, M, S) –Oocytes status D. C. Heins, Tulane U.

12. Analyses and Outcomes ANOVA (cfs, vegetation type) ANOVA (cfs, vegetation type) –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

14. Effects of predation on fountain darter population size at various flow rates

15. Piscivorous fishes: Predation varies (Schlosser and Ebel 1989) : 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) 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

16. San Marcos River (BIO-West 2006) <100 cfs San Marcos River (BIO-West 2006) <100 cfs – consumption not detected <<100 cfs <<100 cfs Increase predation likely, decimation of potential and confirmed fish predators? Increase predation likely, decimation of potential and confirmed fish predators?

17. Trophic cascade: Trophic cascade: Rahel and Stein 1988, Taylor and Soucek 2010, Thomas 2011

18. Questions? Numbers of darters consumed by…? Numbers of darters consumed by…? –Crayfish only –Largemouth Bass only –Crayfish & bass Does vegetation mediate the response?

19. Methods Laboratory setting (FAB) Laboratory setting (FAB) Phase 1: Observational studies Phase 1: Observational studies –Numbers of prey and predators, amount of vegetation, exposure time

20. Methods Phase 2: Phase 2: –Predictions:  Consumption (crayfish) > Consumption (bass) > Consumption (bass x crayfish)  Consumption (bare) > Consumption (vegetation)

21. 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 2: veg/bare

22. Experimental design Replication: 3 Replication: 3 2-factor ANOVA (α = 0.05) with Fisher’s LSD 2-factor ANOVA (α = 0.05) with Fisher’s LSD