The use of nature‐like fishways to increase ecosystem connectivity has increased in recent years, but their effectiveness has rarely been evaluated. A rock ramp was constructed in the Shiawassee River in 2009, and post‐construction effects (2011–2012) were evaluated on the summer fish assemblage by comparing fish assemblage composition to a nearby free‐flowing river and a nearby river with a dam. Patterns of fish species richness, mean catch‐per‐unit‐effort and proportional abundance in reaches upstream and downstream of the rock ramp, dam and comparable sites in the free‐flowing river were evaluated. Overall, species richness by site and proportional abundance in the rock‐ramp river were more similar to the free‐flowing river, while species richness by reach was more similar to the dammed river. These findings suggest that the rock ramp has improved connectivity for the summer fish assemblage, but has not fully restored conditions to the level observed in a free‐flowing river.
Dams across the Great Lakes basin are nearing or beyond their original design life, posing both challenges and opportunities to natural resource managers. Ageing dams can be repaired to preserve function and maintain safety, removed to promote full connectivity or retrofitted with a fish passage structure to increase connectivity without reservoir loss. The success of rock ramp structures is not well documented, especially for cool‐ and warm‐water fishes in the Great Lakes basin. The success of a recently built (2009) rock ramp for increasing upstream fish passage on the Shiawassee River in Michigan, USA, was evaluated. While there was evidence of limited fish passage during the study period (2011–2016), catches of spring migratory fishes, fish eggs and larvae were significantly higher below the rock ramp than above, indicating the dam with rock ramp fish pass continues to limit upstream migration. Overall connectivity appears improved relative to a reference, dammed river, but falls short of full connectivity.
When considering the scale of the rock massif to solve a specific rock problem, it is necessary to consider the structure of the massif within this scale (volume). If the structure is homogeneous within the scale of the massif, the solution can use existing ideas about the properties of rocks in the massif and the scale effect. A homogeneous massif can be composed of micro-heterogeneous "mother" elements. In this case, consideration of rock strength characteristics is associated with statistical characteristics considered in laboratory tests of rock properties. This mathematical apparatus can be important during the selection of rock massif that could be appropriative enough for location of fallout shelters for protection of civilian population against the effects of Nuclear Weapons.
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