Quantifying fish swimming performance and behavior in two diverse environments: a multifaceted approach.

Abstract

In the southeastern United States, low-head dams are common and the effects of these structures on migratory fishes are relatively unknown. Studying how migratory fish behave in habitats altered by dams such as the upstream impoundments that are formed and the downstream tailrace areas is important for understanding and predicting the overall biological and ecological impacts of dams on riverine fish populations and ecosystems. Here I quantified a variety of aspects of behavior, movement, physiology, and hematology of three species of fish in two distinct systems-- a small impoundment that is reflective of upstream habitat created by a dam, and in the tailrace of a dam on the Alabama River. In the small impoundment, I quantified behavior of two species (American paddlefish Polyodon spathula, a riverine fish, and largemouth bass Micropterus salmoides, a lacustrine fish) in an enclosed small impoundment using a combination of acoustic and radio biotelemetry. An array of acoustic receivers allowed me to quantify 2-dimensional movement throughout the impoundment and the radio receiver allowed me to collect data from electromyogram (EMG) tags quantifying fish muscle activity. I found that paddlefish swam constantly throughout the impoundment, and moved faster at night, while largemouth bass were much less active, and showed no diel behavioral pattern. In contrast to my expectations, activity data from the EMG tags were not correlated with 2-dimensional movement calculated from the acoustic tracking data, even when the two data streams were merged at the finest time-scale possible. The EMG data I collected may not be representative of average swim speed, but rather of very fine-scale locomotor activities which are undetectable in the acoustic tracking data. Although these results may not be directly applicable to paddlefish in a riverine setting (e.g., due to effects of flow), they do speak to situations where paddlefish are cultured or are used in a reservoir ranching environment, as well as for lentic habitats such as backwaters where riverine fishes may spend a substantial amount of their lives. The second aspect of my research involved study of the behavior of paddlefish and smallmouth buffalo (Ictiobus bubalus) in the tailrace of a low-head dam on the Alabama River using the same telemetry techniques as in the small impoundment, but at a much larger scale as well as with the addition of quantifying physiological states of fish as they staged and potentially passed the dam during periods of spillway inundation using hematology. In total, 88 of 330 tagged fish passed the dam. I was able to triangulate over 46,000 positions in the tailrace from 35 paddlefish, and 22 smallmouth buffalo. Additionally, EMG transmissions were logged from 180 unique fish in the tailrace, including from 22 individuals during the actual time windows when they passed the dam. I found that paddlefish slightly increased their activity (EMG) above their normal average to pass the dam, while smallmouth buffalo were able to pass with less than average activity. Activity in the tailrace was highest for both species at a gage height of approximately 10.7m. Finally, although paddlefish were able to pass the dam, I measured unprecedentedly high concentrations of cortisol in their plasma. Levels of all blood parameters for smallmouth buffalo were relatively consistent to those measured in other migratory catostomids in tailrace settings. Differences in the passage rates and physiological states of these species could be due to microhabitat preferences in the tailrace, and swimming performance. The results of this riverine portion of my work will provide valuable information for use by the US Army Corps of Engineers and aquatic conservation and/or management organizations in determining and designing species-specific mitigation measures for low-head lock-and-dam structures across a wide array of rivers nationwide.