EFFECTS OF LOW FLOW ON FOUNTAIN DARTER REPRODUCTIVE EFFORT

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Agnes Watkins
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2 EFFECTS OF LOW FLOW ON FOUNTAIN DARTER REPRODUCTIVE EFFORT EDWARDS AQUIFER HABITAT CONSERVATION PLAN (HCP) 014 APPLIED RESEARCH Harlan T. Nichols Masters Candidate Aquatic Resources Texas State University Timothy H. Bonner Professor Texas State University Department of Biology Joseph A. Veech Associate Professor Texas State University Department of Biology U.S. Fish & Wildlife Service San Marcos Aquatic Resource Center

3 Study Objectives Assess relationship between: Flow and Fountain Darter reproduction Vegetation and Fountain Darter reproduction Reproduction response variables: GSI (overall, stage specific) Fecundity estimates (count of MR oocytes) Field vs laboratory study

5 Field Methods Sites Low- high cfs environments Sampling No vegetation, short and tall growing macrophytes and algae Sampling Method Dip nets and Seines > 4.00 mm Water quality and habitat parameters quantified

6 Laboratory Analysis GSI = Gonad wt. mg Eviscerated wt. mg *0 Oocyte and Ovary maturation Developed from information specific to Darters Fecundity estimates Mature Ripe oocytes used Advanced stage Reduced variation Finer scale

7 Classification System Latent Early Maturing Late Maturing Spawning Clutch Production Cycle Mature Nichols and Bonner, unpublished data Heins and Baker (1989), Heins et al. (199), Heins (1995) Ripe Mature Ripe

8 Examples of Classification System Latent Early Maturing Late Maturing Mature Mature Ripe Ripe Spawning Mature Ripening Oocyte Ova

9 Methods Classification system was supported through histology Pre-ovulation Ovulation

10 Results 50 Mean Daily Discharge (CFS)

11 Results 0 Spawning Ovaries 80 Approximate annual spawning period Schenck and Whiteside (1977) Percent Late Vitellogenic Ovaries Early Vitellogenic Ovaries Year round spawning is rare (44) F 11, 518 = 1., P <0.01 Latent Ovaries 7 (45) a Spawning period vs reproductive effort GSI-All Ovaries (35) (3) (40) b b b (41) b (45) (41) () (53) (40) c c c (48) c cd cd d

12 Latent Early Late Spawning Results Comal - Upper Spring Run Similar trend among all sites Declining hydrograph Old Chanel exception Trend associated with reproductive season Not proximate flow effect on reproduction GSI-All Ovaries Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Comal - Old Channel Comal - New Channel San Marcos - City Park Percentage (%)

13 Results Reproductive effort not homogenous Control variation in GSI and fecundity Reduced to three periods Jan-Apr, greatest investment Optimal Spawning May- Aug, investment Tailing Sept- Dec, investment Gonadal Recrudescence Mean Daily Discharge (CFS) Fecundity GSI-All Ovaries JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR May Jun Jul Aug Sep Oct Nov Dec

14 Results Optimal Reproductive period Jan-Apr GSI different among flow treatments > in City Park Fecundity differed among flow treatments and vegetation type CTYPK > USR and NCHN > OCHN Higher in tall vegetation GSI Fecundity F 5,73 = 3.71, P <0.01 Interaction = 0.1 P site = 0.03, P veg = 0.05 F 5,73 = 1.7, P <0.01 USR OCHN NCHN CTYPK Interaction = 0.18 P site < 0.01, P veg = 0.03 B C USR OCHN NCHN CTYPK B * A Tall Bare Short Tall a Bare b b Short

15 Results 14 1 F 7,35 = 0., P = 0.9 GSI 8 Tailing reproductive season GSI and Fecundity No significant differences Discharge Vegetation Type Fecundity USR OCHN NCHN CTYPK F 7,35 = 1.8, P = USR OCHN NCHN CTYPK

16 Results 14 1 F 5,51 = 3.39, P = 0.01 Interaction = 0.07 P site < 0.01, P veg = 0.7 Gonadal recrudescence period GSI 8 4 Bare Short Tall GSI s differed among flow treatment, but not vegetation types Fecundity differed among flow treatment and vegetation types USR and bare greater Fecundity Bare Tall * F 5,51 = 5.4, P < 0.01 Short USR OCHN NCHN CTYPK Interaction = 0.4 P site = 0.03, P veg < 0.01 a b b A B AB USR OCHN NCHN CTYPK B

17 Flow environments and Fountain Darter Reproduction Initial predictions not support Reproductive investments and occurrence of spawning ovaries were similar among flow environments (< cfs to 144 cfs) with a few exceptions. Doubtful that differences observed between San Marcos City Park (144 cfs) and Comal River sites (0 cfs) represent a flow-reproduction threshold. Could be related to the site assessing diet differences between sites Responses observed with pulse flow event was noteworthy

18 Vegetation and Fountain Darter Reproduction Reproductive investments and occurrence of spawning ovaries were similar among vegetation treatments (bare, short, tall) with a few exceptions. Optimum spawning period: Fecundity > in tall vegetation Gonadal recrudescence: Fecundity > in no vegetation Upper spring run habitats with no vegetation Lowest cfs environment studied Associated changes in physical environment Not a poor habitat from a reproductive standpoint

19 Conclusions Under the conditions of this study: Clutch Production Cycle Recruitment to maturity

20 References Heins, D. C Techniques for the determination of clutch parameters in darters and minnows: a proposal for standard methods. Technical Paper 1. Online only: Heins, D. C., and J. A. Baker Growth, population structure, and reproduction of the percid fish Percina vigil. Copeia 1989: Heins, D. C., J. A. Baker, and W. P. Dunlap Yolk loading in oocytes of darters and its consequences for life-history study. Copeia 199: Schenck J.R., and B.G. Whiteside Reproduction, Fecundity, Sexual Dimorphism and Sex Ratio of Etheostoma fonticola. American Midland naturalist. 98:

21 Questions?

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