A new method to map freshwater mussel habitats was developed and tested in theBigSouthForkNationalRiverand Recreation Area (BISO). The procedure involved using an Underwater Video Mapping System (UVMS) to record river substrate information in conjunction with Global Positioning System (GPS) to create
geo-referenced video footage. Simultaneously, the river surface features were
video-recorded using a similar geo-referenced video mapping system. Images from both videos were evaluated and used to produce habitat classifications in a Geographic Information System (GIS) format. The focus of the project was on mapping attributes in the river that are significant to freshwater mussel habitats. These attributes characterize river sections as either favorable or unfavorable to freshwater mussel populations. The attributes specifically selected were based on the habitat suitability needs of five federally endangered species of mussels that exist in BISO. By developing a GIS map of the habitat attributes, biologists knowledgeable in the needs of both adult and juvenile mussels of various species can identify locations suitable for augmenting mussel populations and habitat health.
This project was conducted in 2004 and involved mapping river habitat in over 27.8 km (17.3 mi) of river in BISO. There are 182.2 km (113.2 mi) of river within BISO, so this assessment encompasses 15 % of the river mileage within the park. Most previous mussel studies have not evaluated long segments of river habitat. This work provides continuous mapping of several contiguous kilometers of river.
The findings were stored in a GIS format and used to identify locations for possible re-introduction and management of mussels. Three sections of river in BISO were evaluated. The river segments were chosen to represent river conditions found in different parts of the park. The three sections studied were the Clear Fork Section in the southwest corner of BISO (in TN), Alum Ford Section at the northern park border (in KY), and the Leatherwood Ford Section in the middle of the park (in TN).
In-stream physical habitat characteristics were captured by video cameras at the water surface and underwater. The images were then classified into habitat categories that are either favorable or unfavorable to the mussel populations. Applying UVMS technology was a unique way to gather habitat attributes and create maps. Five primary habitat attributes were evaluated. These attributes were: flow characteristics of the river (pool, run, and riffle), river depth, substrate classification, embeddedness of the substrate, and the presence of coal contamination.
The UVMS above-water camera system was very successful in evaluating the flow characteristics of the river (distinguishing between pool, run, and riffle) in the three study sections in BISO. The UVMS underwater video footage was used to classify substrate characteristics. The evaluation for the presence of coal deposits indicated the Clear Fork Section did not have coal deposits in the video footage, whereas the Leatherwood Ford and Alum Ford sections had a significant amount of coal in the river.
The UVMS was successful at locating areas of possible habitat for the five mussel species of interest. These areas are mostly in clusters along the river. There is significant overlap in the suitable habitat areas identified among the five species, largely because several of the species prefer similar habitat attributes. Four of the species require riffles for optimal habitat, and the flow characteristics in the Clear Fork and Leatherwood Ford sections provided this type of habitat. The other species was a pool-loving species, which had more optimal habitat in the pool segments in the Leatherwood Ford Section. The Alum Ford Section did not have any suitable mussel habitat because the impounded river forms a reservoir. The intermittent substrate classification points on the lake bottom showed continuous silt, which does not provide suitable habitat for any of the five species of endangered mussels.
Out of the total 1,207 sites evaluated for habitat suitability, the majority were unsuitable as mussel habitat. The total number of suitable habitat sites identified per species ranged from 109 to 548 (this is the combined total for optimum, suboptimum and marginally suitable habitat). Mussels are very specific in terms of the habitat they thrive in, so a method to systematically identify these locations is a valuable tool.
Overall very few areas of optimal habitat were identified. For the four species that thrive in riffle habitats, two (or less) optimal habitat sites were identified per species. The fifth species, the Cumberland Elktoe, thrives in pools. Over the length of the mapped rivers there was considerably more length of pool than riffle, so there were more opportunities for desirable habitat for this pool-loving species; 19 optimal habitat sites were identified. When the habitat criteria were expanded to encompass suboptimal and marginal criteria, the number of suitable habitat sites increased dramatically for all of the species. For each of the four riffle-loving species the expanded criteria identified suitable habitat in approximately 10% of the classified points. For the pool-loving Cumberland Elktoe, the expanded criteria identified suitable habitat in almost 50% of the classified points