Habitat Considerations for Mussel Reestablishments and Translocations Brett
Habitat Considerations for Mussel Re-establishments and Translocations Brett J. K. Ostby Department of Fisheries and Wildlife Sciences Virginia Tech
Translocation Woes • Stress to mussels in collection and transportation • No or limited consideration for habitat
Overview • Background – – – Literature review Basic concepts Terms • Applying that knowledge – Framework for selecting suitable destination sites – What to measure
Quantifying habitat In the 70 s and 80 s there was a focus on small scales (microhabitat) using basic measurements of flow and substrate • Flow depth and velocity • Substrate particle size And many studies to this day quantify habitat by velocity, depth, and substrate size during low flow conditions with varying success
Why microhabitat? • Understanding habitat at this scale may explain behavior and survival of individuals • Intuitive • Important for fish, why not mussels? • Focus on this scale may be a consequence of fragmentation
Microhabitats Strayer (1981) • Species that coexisted in a site had similar microhabitat associations • Species had broad distributions within a site • Microhabitats occupied by a species varied among sites Random dispersal over diverse microhabitats Microhabitat is not limiting, no selective pressure toward specialization
Microhabitat • Other studies found subtle differences among microhabitat use by species • But many others have failed to detect patterns at small scales
M aj or pr ob le m s • Patterns are rarely clear • The same species appeared to occupy different habitats in different streams • Species appear to have broad overlapping habitat use
Generation of new hypotheses
Generation of new hypotheses • Measuring the wrong components of habitat • Patterns concealed by processes and events at greater temporal and spatial scales which shape habitat at smaller scales and may directly effect abundance and richness • Other biological processes explain abundance and richness – Host fish distribution and abundance (Haag & Warren 1998)
Measuring the Wrong Components of Habitat? Hydraulic stream ecology approach proposed by Statzner et al. (1988) • Reynolds number – Turbulence • Froude number – Gravity vs. inertial force • Shear stress – Force on bed • Stream Power – Describes the erosive capacity of a stream
Hydraulic Stream Ecology – Layzer and Madison (1995) use simple and complex hydraulic parameters to measure a reach below a dam with consideration for temporal context – Found low predictive power for simple parameters; however, shear stress was negatively correlated with mussel abundance at a higher discharge
Hydraulic Stream Ecology • Several recent studies have since applied this approach at the microhabitat and greater scales and have seen patterns, however these patterns differ by stream – – – – Myers-Kinzie (1998) Hardison and Layzer (2001) Krstolic (2001) Gangloff (2003) Stone et al. (2004) Ostby (2005) Adair (2005)
Hardison and Layzer (2001) • Fliesswasserstammtisch (FST) hemispheres used to measure local shear stress near bed flow
Measuring the Wrong Components of Habitat? • Adair (2005) study in the Duck River – Adult and juveniles densities within a reach related to • shear stress (FST) • interstitial water temperature – Substrate permeability also a predictor of juvenile occurrence
Spatial and temporal context Nested Habitat Hierarchy
Spatial and Temporal Scale Landscape Within Reach (Macrohabitat)
Stream Systems • Events and Processes that form and alter stream systems influence habitat at finer scales and affect assemblage patterns and species distributions • Several studies have observe that mussels occupying certain microhabitats were absent in systems where similar microhabitat exist • Strayer (1983) suggested that macrohabitat factors controlled velocity, turbidity, water chemistry, and timing an character of organic input
Stream Systems • One step further. . . Stayer (1983) suggested variation in discharge patterns where the most important limiting factor • Flow regime (Poff et al. 1997) –Magnitude –Frequency –Duration –Timing (predictability) –Rate of change (flashiness)
Flow Regime • Magnitude of discharge describes the volume of water passing a fixed location per unit time • Gangloff (2003) observed that increases in magnitude of flow over the recent past were associate with declines in some streams of the Upper Alabama River basin
Flow Regime • Frequency is how often a flow above a give magnitude recurs and is inversely related to flow magnitude • Hastie et al. (2001) documented the effect of a 100 yr flood on mussel populations in the River Kerry • Found that some mussel beds untouched while other buried or dislodged as channels were scoured and reformed – Refuges?
Flow Regime • Duration or timing of flow events have never been explicitly studied • Nevertheless, the timing or predictability of flows has often been cited as a culprit in the decline of musses below dams • May affect reproductive success, fish assemblages
Flow Regime • Rate of change (flashiness or hydrological variability) appears to have profound effects on species distributions • Di Maio and Corkum (1995) found different assemblage patterns in flashy than in stable streams • Arbuckle (2000) found flashy streams in Iowa had reduced density – Both studies noted that these patterns were related to land use (landscape scale)
Stream Systems • Stream systems can have very different flow regimes controlled by basin topography, climate, and land use • These factors can determine long-term stability of habitat patches used by mussels and obscure patterns at finer scales • Clinch River (Virginia and Tennessee) vs. Eel (Northern California)
Eel • High discharges constrain distribution in the Eel River • Mussels are almost exclusively found in pools, near channel banks in sedge mats where shear stress and flow velocities are considerably lower
Clinch • Mussels beds found in riffles and shoals often in the middle of the river • These habitats have the highest velocities and shear stress values during low flows • Mussels less abundant in pools and deeper runs • Riffles and Shoals more stable habitats?
Stream Systems • Geology, soils, and land use differences among streams also have affects on assemblages via changes to – Flow regime – Sediment regime – Water quality
Stream Segments • Physico-chemical differences among stream segments – Input from tribs • Progression from first-order streams to large rivers – River Continuum Concept – May be complicated by anthropogenic impacts
Stream Segments Riparian Vegetation • Density has been correlated with riparian vegetation type (Leff et al. 1990) • Vegetation type indicative of hydrological variation? • Morris and Corkum (1996, 1999) observed that riparian zones affected growth and species distribution • Forest = species with slow growth • Grasses = species fast growth • Transplants confirmed these patterns • Iowa Streams with forested riparian had higher richness (Arbuckle 2000)
Stream Segments Lithology and Valley Shape • Church (1997) observed that large continuous areas of alluvium (gravel shoals) with little or no bedrock supported mussel beds • Shoals occurred in reaches with braided channels; however, the structures that created these conditions changed with channel lithology and valley morphology (segments) • Of 26 braided reaches, 24 occurred on shale formations, while only two on limestonedolomite
Stream Segments Lithology and Valley Shape • Greatest number of high quality braided reaches occurred over the thicker of two shale formations • The segment of river that flowed through this formation also had a greater valley floor width and the lowest gradient of all formations in the river Allowed the stream to meander • But. . . high quality reaches also existed in the limestone dolomite segments where the stream flowed perpendicular to the underlying bedrock ledges
Reaches • Krstolic (2001) compared hydraulic parameters of riffle complexes among reaches in the Clinch River • She found simple hydraulic measurements varied little among reaches • However, she observed different patterns between high and low quality reaches for shear stress and stream power – High in spring, high in late summer Low Quality – Low in spring, low in late summer – High quality were high in spring, moderate in late summer
Reaches • Stone et al. 2004 saw a contrasting pattern in a southwestern Washington stream, as did Gangloff (2003) in Alabama • Mussel populations higher in low shear stress habitats
Current Paradigms • Flow Regime • Spatial and Temporal Scale – Limiting factors at all scales • Refugia
So many things to consider where do we start? • • • Water quality? Substrate? Flow? Geomorphology? Landscape? Microhabitat?
Translocation Habitat Framework Landscape Reach Within Reach
Landscape • Risk Assessment (Zimmerman 2003, Guyot 2006) – Some variables used • # of mines • Distance to road • % urban land use • Hydrological models
Reaches • Stability – Refuges (Shear stress and channel morphology) – Riparian vegetation – Bank Stability – Visual habitat assessment (Mc. Rae et al. 2004)
Within Reaches • Are low flow conditions relevant? – Most of the time streams experience low flow conditions
Within Reaches • Are low flow conditions relevant? – Flow for biological needs most of the time streams experience low flow condition – Some species have specific habitat needs (Ostby 2005)
Upper Lower Fast-flow Specialist Fast-flow Generalists • Exclusively in fast flows • More likely in fast flows • Narrow range • Wider range
Within Reaches • Are low flow conditions relevant? – Most of the time streams experience low flow conditions – Some species have specific habitat needs (Ostby 2005) – Juvenile habitat? • Interstitial flow • Embeddedness • Fewer clogging fines Sedimentation?
Within Reaches : Embeddedness, interstitial flow, %fines
Within Reaches • Are low flow conditions relevant? – Most of the time streams experience low flow conditions – Some species have specific habitat needs (Ostby 2005) – Juvenile habitat? • Interstitial flow • Embeddedness • Fewer clogging fines Sedimentation? – Small Scale Refugia (Strayer 1999) – Fish Habitat
Within Reaches • Limitations: – Data is limited (Ostby 2005, Adair 2005, Boden & Brown 2002) – Transferability of criteria • Currently testing transferability of criteria to Duck River and assessing value to guide translocation in French Broad
Some Sensible suggestions • Include money for habitat evaluation in projects! • Develop risk assessments • Empirically derived bankfull Shear Stress • Monitor low flow conditions in selected reaches • Faux mussels?
Faux Mussels • Place in potential destination sites to identify locations where suitable low flow conditions and refuges are coincident • Could be a rock with the same density (specific gravity) or buoyant weight
Translocation Habitat Framework Landscape Reach Within Reach Risk Assessment & Prediction models Stability Specific and juvenile needs coincident with stability
Discussion
- Slides: 50