Fish monitoring requirements of new FERC licenses: are they adequate?

Transcription

1 Fish monitoring requirements of new FERC licenses: are they adequate? Joseph D. Kiernan, Peter B. Moyle and John G. Williams Center for Watershed Sciences University of California, Davis

2 Trends from recently issued FERC licenses How variable are fish populations over time? Lessons from Martis Ck. - 5, 12 and 3 years Conclusions and recommendations Outline:

3 Trends in new FERC licenses 92% of new licenses included a change to the flow regime 67% included post-license fish monitoring Annual sampling first 3-5 years Required sampling effort subsequent sampling at 5 year intervals Term of new license: Mean = 38 yrs (range = 3 to 4 yrs) Total # monitoring yrs: Mean = 7 (range = 1 to 12) Years after new license

4 How useful is periodic monitoring likely to be? Natural variability may mask population changes due to dam operation Coefficient of variation (SD/mean; %) Adult trout density (fish/km) Highly fluctuating Moderately fluctuating Moderately stable Highly stable Sample sites on North Fork Middle Fork Tule River Data from Studley et al. 1995

5 Long-term monitoring of Martis Creek Martis Creek: a 3 year perspective Tributary of Truckee R. 2.9 km segment Martis Dam (USACE; 1972) Pre-dam Q max = 5.9 m 3 /s (1963) Post-dam Q max = 17.3 m 3 /s (26) Martis Dam

6 Martis Creek: a 5 year perspective Sampled Fish assemblage 5 native 2 non-native trout Habitat variables Microhabitat use Discharge (m 3 /s) Food habits Multiple water year types: Normal (1979, ) Dry (1981) Wet (1982, 1983) Water Year

7 Martis Creek: a 5 year perspective Ecology: 66(1), 1985, pp Fish assemblage dominated by native species density and biomass Assemblage persistent and stable over time Density (individuals/1 m 2 ) Proportion of total density 1 Total Assemblage Native Fishes Native fishes

8 Martis Creek: a 5 year perspective Stability maintained by niche diversification Depth Water velocity Substrate size From Moyle and Vondracek 1985

9 Discharge (m 3 /s) Year Proportion of total density 199 Martis Creek: a 12 year perspective 1 Total Assemblage Native Fishes 1 1 Density (individuals/1 m 2 ) no data Severe spring flooding in 1983 reduced recruitment of native sp. Two distinct equilibria: Native fishes 1. native sp. ( ) Strange EM, Moyle PB, Foin TC Environ. Biol. Fish. 36: b t t (1984 9)

10 Martis Creek: a 3 year perspective Daily discharge (m 3 /s) Mean max. daily water temperature ( C) Discharge (m 3 /s) Mean daily discharge WINTER ( ) Water temp ( ) Kiernan and Moyle. Ecol Apps, in revision O N D J F M A M J J A S Month of water year

11 Martis Creek: a 3 year perspective Basic fish assemblage persistent and resilient Multiple stable states Assemblages dominated by: - native sp. ( ) - brown trout ( ) - rainbow trout ( ) Populations highly variable over time and space Density (individuals/1 m 2 ) Proportion of total density 1 Total Assemblage Native Fishes Native fishes

12 Spatial and temporal variability in fish populations 1 A) Brown trout 1 B) Rainbow trout 1 C) Green sunfish Relative abundance (%) Relative abundance (%) Relative abundance (%) Relative abundance (%) D) Paiute sculpin G) Speckled dace E) Tahoe sucker H) Lahontan redside F) Mountain sucker I) Mountain whitefish Year Year Year Sample Site Sample Site Sample site Sample Site

13 Variability in fish populations ( ) 1 Density Biomass 1 1 Highly fluctuating Moderately fluctuating 1 Highly fluctuating Moderately fluctuating Moderately stable Moderately stable Highly stable Highly stable 1 1 Coefficient of variation (%) (%) Lahontan redside Speckled dace Mountain sucker Mountain whitefish Paiute sculpin Tahoe sucker Green sunfish Rainbow trout Brown trout Lahontan redside Speckled dace Mountain sucker Mountain whitefish Paiute sculpin Tahoe sucker Green sunfish Rainbow trout Brown trout Native species Non-native species Native species Non-native species

14 Population changes are asynchronous Solid circles = downturns Open circles = upturns Species WYT = N N D W W W N W N D N D D D N D W N W N W N D N N N N W D N Native Lahontan redside Mountain sucker Mountain whitefish Paiute sculpin Speckled dace Tahoe sucker Alien (non-native) Brown trout Rainbow trout Green sunfish

15 Population changes are asynchronous Solid circles = downturns Open circles = upturns Species WYT = N N D W W W N W N D N D D D N D W N W N W N D N N N N W D N Native Lahontan redside Mountain sucker Mountain whitefish Paiute sculpin Speckled dace Tahoe sucker Alien (non-native) Brown trout Rainbow trout Green sunfish Population increases Population decreases

16 Is streamflow the master variable? Proportion of alien fish (A) r s = -.47, P =.1 (B) Winter (C) Mean annual discharge (m 3 /s) r s = -.39, P =.3 Spring r s = -.5, P = One day max discharge Log 1 (m 3 /s + 1) Winter, P =.31 Spring, P = Frequency of floods (No./season)

17 Variables describing fish abundance Brown trout Drought (-) % gravel (-) Winter floods (-) Rainbow trout % boulder (+) mean depth (-) Green sunfish % sand (+) Drought (-) Lahontan redside % boulder (-) % pool (+) Tahoe sucker % boulder (-) Winter floods (-) % pool (+) Paiute sculpin % sand (-) Speckled dace % boulder (-) max. Depth (+) % gravel (-)

18 Conclusions: Trout populations highly variable CV density = % CV biomass = 7-131% Population responses to streamflow are complex and context dependent Monitoring programs need to capture the range of environmental variability Extremes may be important Performance criteria based exclusively on abundance may lead to erroneous conclusions

19 Questions?