GCPLCC Instream Flow Project DRAFT Regional Flow-Ecology Hypotheses: Examples and Format October 19, 2012

Categories of Flow-Ecology Hypotheses Biotic Interactions – Species – Guild – Community Water quality – DO – Temperature Physical Habitat -Availability Energy Supply - OM Transport

GCPLCC Regional Flow-Ecology Hypotheses Subsistence Flows Ecoregion: Coastal River Class: small, low gradient, warm streams and rivers Subsistence Flow Hypothesis #1: Dissolved oxygen and temperature are adversely affected by reduced magnitude of subsistence flows Effected species: All fish, mussels, and other riverine species sensitive to and unable to avoid low oxygen and high temperatures Water Quality Parameter Altered subsistence flow – magnitude Source: Sabine-Neches BBEST Biological Overlay Appendix XIII Dissolved Oxygen Temperature

GCPLCC Regional Flow-Ecology Hypotheses Subsistence Flows Ecoregion: Coastal River Class: small, low gradient, warm streams and rivers Subsistence Flow Hypothesis #1: Dissolved oxygen and temperature are adversely affected by reduced magnitude of subsistence flows Effected species: All fish, mussels, and other riverine species sensitive to and unable to avoid low oxygen and high temperatures Altered Water Quality Parameter Altered subsistence flow – magnitude Source: Sabine-Neches BBEST Biological Overlay Appendix XIII Dissolved Oxygen Temperature Alternate Graphical F-EH Format

GCPLCC Regional Flow-Ecology Hypotheses Subsistence Flows Ecoregion: All River Class: headwaters, streams, and small rivers Subsistence Flow Hypothesis #2: Extended periods of subsistence flows strands fish in pools and other isolated bodies of water (e.g., oxbows) where they become concentrated and predation increases. Effected species: Channel and blue catfish, small mouth buffalo, gar, and other large and small fish Abundance Altered subsistence flow – duration Source: Sabine-Neches BBEST Biological Overlay Appendix XIII Predatory species Prey

GCPLCC Regional Flow-Ecology Hypotheses Base Flows Ecoregion: All River Class: All Base Flow Hypothesis #1: Sediments become more stable during periods of extended base flow, which is beneficial for many mussel species. (Vaughn and Taylor 1999, Strayer 2008) Base Flow Hypothesis #2: Mussels feed on higher densities of water-column food resources during periods of extended base flow (Rypel et al. 2009) Effected species: All mussel species (e.g., Quadrula fragosa (Winged mapleleaf), Leptodea leptodon (Scaleshell) # of mussel species Altered base flow – duration Source: Sabine-Neches BBEST Biological Overlay Appendix XIII

GCPLCC Regional Flow-Ecology Hypotheses Base Flows Ecoregion: All River Class: headwaters, streams, and small rivers Base Flow Hypothesis #3: Sight-oriented predatory fish can exploit prey populations that are at high densities and in clear water during extended periods of base flows, especially during summer and fall. Effected species: Sight-oriented predatory fish and their prey Abundance Altered base flow – duration Source: Sabine-Neches BBEST Biological Overlay Appendix XIII Predatory fish species Prey

GCPLCC Regional Flow-Ecology Hypotheses Base Flows Ecoregion: River Class: headwater, streams, and small rivers, moderate gradient Base Flow Hypothesis #4: Reduced base flow exposes riffles reducing the extent of available habitat and the abundance of riffle-obligate species. Effected species: All riffle-obligate species (e.g., Etheostoma spectabile (Orangethroat darter)) Abundance of riffle-obligate species Altered base flow – magnitude Source: TNC-OK

GCPLCC Regional Flow-Ecology Hypotheses High Flow Pulses Ecoregion: River Class: High Flow Pulse Hypothesis #1:. Effected species: Parameter Altered High Flow Pulses– duration Source: Parameter #1 Parameter #2

GCPLCC Regional Flow-Ecology Hypotheses Overbanking Flows Ecoregion: River Class: Overbanking Flow Hypothesis #1:. Effected species: Parameter Altered Overbanking Flow– duration Source: Parameter #1 Parameter #2