Wednesday, August 4, 2010: 11:10 AM
330, David L Lawrence Convention Center
Background/Question/Methods While it has been demonstrated that riparian corridors are important foraging habitats for many temperate insectivorous bat species, and that aquatic insects can be important prey, more work is needed to explore the link between bats and the benthic macroinvertebrate community within rivers. The purpose of this study is to test the hypothesis that bat foraging activity in rivers is determined primarily by the abundance of prey, which can be predicted by the abundance of benthic macroinvertebrates; further, that fish and bats may interact indirectly by competing for the same food source at different life stages.
Eight study sites in two Connecticut rivers (the Eightmile East and the Coginchaug) were sampled during the summers of 2008 and 2009. Bat activity was measured by overnight passive recording; records were analyzed for echolocation calls. Locations included riffles sampled for benthic macroinvertebrates within reaches sampled for fish. Macroinvertebrate collections were identified to family; richness, abundance and diversity were calculated for aquatic insect taxa (“bat food”). Fish data was collected through electrofishing with identification to species. Other variables measured include total riffle area in the reach, water velocity, and stream canopy cover.
Results/Conclusions For all sites over both years bat call abundance was significantly and positively correlated with “bat food” abundance. A greater variation of bat call abundance was explained by the invertebrates when the samples were temporally constrained as within year or within months. When total riffle area was included in the model more than 90% of the variation in bat call abundance was explained. Fish and invertebrate abundance are positively correlated, more strongly with the entire invertebrate community (vs. the “bat food” component) indicating only a partial overlap of prey between bats and fish. Bat call and fish abundance are weakly positively correlated. Additional results concern the relevance of invertebrate richness and diversity, canopy and water velocity, and the change in bat call abundance from 2008 and 2009.
This study reveals a significant association between bat use of river habitat and the benthic macroinvertebrate community, which is also determined to be associated with habitat quality for fish. This knowledge could be useful for river restoration and protection and for bat conservation efforts, and could utilize existing databases since the benthic macroinvertebrate community is regularly sampled by state and non-profit agencies.
Eight study sites in two Connecticut rivers (the Eightmile East and the Coginchaug) were sampled during the summers of 2008 and 2009. Bat activity was measured by overnight passive recording; records were analyzed for echolocation calls. Locations included riffles sampled for benthic macroinvertebrates within reaches sampled for fish. Macroinvertebrate collections were identified to family; richness, abundance and diversity were calculated for aquatic insect taxa (“bat food”). Fish data was collected through electrofishing with identification to species. Other variables measured include total riffle area in the reach, water velocity, and stream canopy cover.
Results/Conclusions For all sites over both years bat call abundance was significantly and positively correlated with “bat food” abundance. A greater variation of bat call abundance was explained by the invertebrates when the samples were temporally constrained as within year or within months. When total riffle area was included in the model more than 90% of the variation in bat call abundance was explained. Fish and invertebrate abundance are positively correlated, more strongly with the entire invertebrate community (vs. the “bat food” component) indicating only a partial overlap of prey between bats and fish. Bat call and fish abundance are weakly positively correlated. Additional results concern the relevance of invertebrate richness and diversity, canopy and water velocity, and the change in bat call abundance from 2008 and 2009.
This study reveals a significant association between bat use of river habitat and the benthic macroinvertebrate community, which is also determined to be associated with habitat quality for fish. This knowledge could be useful for river restoration and protection and for bat conservation efforts, and could utilize existing databases since the benthic macroinvertebrate community is regularly sampled by state and non-profit agencies.
