Impacts of artificial structures on the freshwater pearl mussel Margaritifera margaritifera in the River Dee, Scotland

Understanding linkages among fluvial geomorphology, habitat, and aquatic biota is critical for effective stream ecosystem conservation. However, composite effects of hydrogeomorphic adjustment and condition, which collectively represent channel stability, on freshwater mussel and stream fish assemblages remain unresolved. Associations between stream hydrogeomorphic characteristics (channel geometry, substrate composition, stream flow) and mussel and stream fish assemblages were explored at 20 study reaches characterized by riffle–pool interfaces (RPIs) in Ohio, USA. At a coarse resolution using categorical classifications of equilibrium (i.e. stable) vs. adjusting (i.e. unstable) RPIs, overall fish and darter density was greater at adjusting RPIs (P = 0.048 and P = 0.024, respectively). Conversely, fish species richness was 1.2× greater at equilibrium than adjusting RPIs (P = 0.047). Analysis of quantitative hydrogeomorphic data collected with fine‐resolution surveys showed that hydrogeomorphic parameters explained from 20% (darter assemblage evenness) to 55% (density of mussels known to use darters as hosts) of the variation observed in all assemblages. Drainage area was significant in most models with variable influence: R2 = 0.10 for darter species richness to R2 = 0.41 for Simpson's diversity index of mussels with darter hosts. Other important predictor variables included embeddedness, velocity, shear stress, roughness, channel dimensions, and sediment size. Whereas coarse‐level fluvial geomorphic classifications may be meaningful for fish, they appear less so for mussels. Fine‐resolution quantitative hydrogeomorphic variables provided substantially more information for both assemblages, although hydrogeomorphology–fish and hydrogeomorphology–mussel relationships were not consistent. Some of the strongest relationships related to mussels that use darters as hosts, suggesting that these species are particularly sensitive to hydrogeomorphic conditions. Collectively, these results indicate that fluvial geomorphic condition and characteristics can simultaneously influence co‐dependent stream biota. Stream conservation and management plans that include explicit hydrogeomorphic surveys may appreciably benefit cohabitating freshwater fish and mussel assemblages. Copyright © 2014 John Wiley & Sons, Ltd.

Section: Discussionmentioning

confidence: 99%

Associations between stream hydrogeomorphology and co‐dependent mussel–fish assemblages: evidence from an Ohio, USA river system

Bey

Sullivan

2014

“…Impoundments, pearl fishing, acidification, eutrophication, siltation, degraded water quality, exotic species, and altered fluvial regimes may all have played roles in the FPM decline (Williams et al , ; Young et al , ; Strayer et al , ), although the exact cause is often unclear. General habitat changes have also been suggested as a reason for declining populations (Ross, ; Cooksley et al , ). Björk () demonstrated a significant decline in an FPM population after forest cover in the catchment changed from deciduous to coniferous.…”

Section: Introductionmentioning

confidence: 99%

Predicting population status of freshwater pearl mussel (Margaritifera margaritifera, L.) in central Sweden using instream and riparian zone land‐use data

Degerman

Andersson

Söderberg

et al. 2013

1. The freshwater pearl mussel Margaritifera margaritifera (L.) has become scarce and threatened throughout most of its distribution range, and is consequently listed as 'endangered' by the IUCN. It has been suggested and used as an indicator species and even as an umbrella species. Despite this, few studies have examined factors affecting its catchment-level population status.2. This work tested the hypothesis that it is possible to predict freshwater pearl mussel population viability (reproducing/not reproducing) and population status in central Sweden from a combination of geospatial data describing riparian land-cover and use, water chemistry data, and electrofishing data describing the abundance of the host fish species (brown trout, Salmo trutta) in 56 streams.3. Mussel population viability was best predicted by total phosphorus. Using higher-resolution data (six classes) on mussel population status, host fish abundance (0+ trout) was the best predictor. At abundances below 5 0+ trout per 100 m 2 and above a concentration of 8 mg L -1 total phosphorus, only three viable populations existed.4. Geospatial data could be used to predict levels of total phosphorus and thereby indirectly to predict mussel viability. Geospatial data could not be used to predict abundance of 0+ trout, which is thought to depend more on instream factors. This study demonstrates that geospatial data on riparian land-use and cover can be a useful tool for screening waters potentially harbouring non-reproducing mussel populations.

“…The sources of pressures that lead to these declines generally come from the catchment into the river (Moorkens, ), with soil disturbance and the addition of artificial fertilizer increasing the sources, and drainage increasing the pathways of fine sediment and nutrients into the rivers. Physical changes to the river can also affect mussel habitat, such as bank protection structures, bridges, and direct damage from dredging (Cooksley et al ., ), all of which change the hydromorphological function of the habitat. Changes in flows at an ecologically relevant level are a key component of freshwater habitat and species decline (Bunn and Arthington, ; Dyson et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Assessing near‐bed velocity in a recruiting population of the endangered freshwater pearl mussel (Margaritifera margaritifera) in Ireland

Moorkens¹,

Killeen²

2014

Stream bed and mid‐column velocities, depth, redox, and mussel densities were measured in 76 quadrats across five transects in Margaritifera margaritifera habitat supporting high densities of adult mussels and evidence of recent juvenile recruitment.At relatively low flow (Q85), the near‐bed velocities over the mussel habitat remained high, with optimal habitat having stream velocities of 0.27–0.31 m s−1.The average near‐bed velocity for mussel densities greater than 20 m−2 was 0.3 m s−1, with a range from 0.18 m s−1 for mussel densities lower than 10 m−2, to 0.3 m s−1 for mussel densities greater than 50 m−2.The average velocity at 60% depth for mussel densities greater than 20 m−2 was 0.37 m s−1, with a range from 0.21 m s−1 for mussel densities lower than 10 m−2, to 0.39 m s−1 for mussel densities greater than 50 m−2.Percentage redox losses from open water to water at 5 cm substrate depth were an average of 18% for mussel densities of 1–10 m−2 to 13% at mussel densities >100 m−2.The conclusion from this study is that relatively high velocities are present at relatively low flows in sustainable Margaritifera habitat, suggesting that this species is adapted to a combination of stable substrate conditions that are kept clean through high water velocities with low fine sediment infiltration, rather than habitat that is subject to regular fine sediment infiltration followed by substrate cleansing. Copyright © 2014 John Wiley & Sons, Ltd.