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Distribution of Freshwater Mussel Populations in Relationship to Crossing Structures. Final rept.
| 题名： | Distribution of Freshwater Mussel Populations in Relationship to Crossing Structures. Final rept. |
| 作者： | ANDERSEN, E. F.; BOGAN, A. E.; EADS, C. B.; LEVINE, J. F.; RUSSELL, P. P. |
| 关键词： | *Shellfish-; *Mussels-; *Natural-resources-conservation; *North-Carolina; *Bridges-; *Culverts-.;Aquatic-biology; Environmental-quality; Scour-; Neuse-river-basin; Cape-Fear-river-basin. |
| 摘要： | The goals of this study were to evaluate the potential impact of road crossings on freshwater mussels in North Carolina and determine the factors that contribute to any impact. We visually surveyed mussels in the 300-meter reaches upstream and downstream of 80 road crossings in the upper Neuse and Cape Fear River Basins. We characterized the habitat at each site by estimating the percentage of riffle, run, and pool in 25-meter increments, and we used standardized criteria to score stream habitat quality. Aquatic insect samples were collected at 44 sites and diversity and tolerance values were compared upstream and downstream of the road. No differences between upstream and downstream were found using aquatic insects. Bank stability scores were highest near the crossing structures, especially within 50-75 meters upstream, but overall bank stability decreased with distance from the bridge downstream. Upstream bank stability scores were significantly higher than downstream bank stability scores (p-value > 0.05) and the most downstream 100-meter reach had the lowest scores. There was a possible trend of decreased pool habitat within 100 meters upstream and downstream of road crossings as pool habitat seemed to decrease with decreasing distance from the road (p = 0.099). These results may be indicators that some road crossings are altering stream habitat for some distance upstream and downstream of the road. Overall, several analyses show decreased relative abundance of the most common mussel species, Elliptio complanata, in the 50 meters immediately downstream of the road. Also, mean length of E. complanata was lower downstream than upstream (p < 0.05). No evidence of effects on other species was found, but no definitive conclusions can be made due to the rarity of these other species. We attribute declines in abundance just downstream of crossings to channel constriction in some bridge and culvert designs as well as the effects of recent construction. |
| 报告类型： | 科技报告 |
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