Objective Dams impede fish movement and can isolate riverine populations into defined areas. The Alabama River is divided into four major sections by three lock-and-dam structures. Here, we used otolith microchemistry and genetic techniques to quantify potential movements and population connectivity among these river sections for two fish species (Freshwater Drum Aplodinotus grunniens and White Crappie Pomoxis annularis) that differ in life expectancies, spawning strategies, and swimming abilities.Methods We collected water samples throughout the study area to quantify spatial variation in trace element ratios, and we collected fish from the four river sections defined by the three lock-and-dam structures to quantify spatial variation in their otolith trace element ratios and their population genetic structure.Results Trace element ratios (Mg:Ca, Mn:Ca, Sr:Ca, and Ba:Ca) in water samples collected throughout the study area varied spatially but were temporally consistent. Broad patterns in water chemistry were reflected in element : Ca ratios in otolith whole transects (i.e., across entire life), edges (reflecting time of capture), and cores (reflecting early life). Correlations between otolith edge and season-specific water Sr:Ca ratios from the areas where fish were collected were significant for both species, while the associations between otolith edges and water were mostly nonsignificant for Mg:Ca, Mn:Ca, and Ba:Ca ratios. Linear discriminant analyses were used to determine how accurately the multivariate element signatures in otolith edges could classify fish back to the river sections from which they were collected, resulting in mixed accuracies between species. Genetic structure was present in both species but was weaker in Freshwater Drum than in White Crappie, indicating that barriers have had a greater influence on White Crappie genomics than on Freshwater Drum genomics. Overall, there was little support for either species showing substantive movement past the lock-and-dam structures.Conclusions Our results based on both otolith microchemistry and genetics suggest that movement of these species past dams is very limited. Individuals of both species generally appear to remain in areas near where they hatched; although movements among habitats may occur, both upstream and downstream dam passage events appear rare. Efforts at increasing connectivity, if successful in attracting and moving fish, would increase opportunities for movement, thus increasing gene flow beyond its highly restricted current state. Dams can alter the ability of fish to move in rivers. We studied the effects of dams on movement of Freshwater Drum and White Crappie and found that both their ear stone chemical composition and their genetic structure supported limited movement past lock-and-dam structures.

Objective The Paddlefish Polyodon spathula rostrum aids in finding zooplankton prey, increases feeding efficiency, and provides lift and stability during swimming. This structure can sometimes be damaged or even completely missing, with little known about the effects of rostrum injury or loss on growth, survival, and swimming capability. Our objectives were to (1) determine the proportion of Paddlefish with a damaged rostrum in the Alabama River and assess how this proportion varied based on location along the river, fish length, and sex; (2) quantify the relationship between Paddlefish rostrum damage and body condition or gonad development; and (3) investigate the correlation between Paddlefish rostrum injury and dam passage rate at Claiborne Lock and Dam.Methods We collected Paddlefish (n = 409) from throughout the Alabama River and quantified rostrum injuries for each. Gonad weights (from 309 fish) and rostrum weights (from 93 fish) were quantified, and a subset of 100 fish was implanted with combined acoustic and radio transmitters and tracked via both stationary acoustic and radio receivers.Results The highest percentage of Paddlefish with rostrum damage occurred in the lower two sections of the Alabama River (lower Alabama River and Claiborne Lake), whereas lower percentages were observed in the upper two sections (William "Bill" Dannelly Reservoir and Jones Bluff Reservoir). Female Paddlefish had significantly better rostrum condition scores than males, and rostrum condition did not vary as a function of fish length. Males with rostrum damage had significantly lower body condition than males without damage, whereas there was no significant effect in females. Upstream passage rates past Claiborne Lock and Dam did not differ between individuals with rostrum damage and those without rostrum damage, and a calculated rostrum damage score did not differ significantly between fish that passed the dam and those that did not pass.Conclusions Although the occurrence of damaged rostra varied among dam sites and the body condition of males varied slightly (albeit significantly), the body condition of females and passage by fish with damaged versus undamaged rostra did not differ. As such, the overall effects of rostrum damage did not appear to be detrimental given the parameters that we measured for damaged individuals. The Paddlefish rostrum or "paddle" helps them swim using less energy, improves feeding by funneling water into the mouth, and aids in finding food. Tracking migrating Paddlefish with damaged rostrum in the Alabama River below and just above the lowermost dam, Claiborne Lock and Dam, showed that damage to the rostrum did not reduce the chance that Paddlefish could make it across the spillway to continue their spawning migration. Whether or not this kind of damage causes reduced long-term survival or reduced reproduction is yet to be determined.

Predicting effects of rising temperatures on the health and physiology of aquatic organisms is receiving increasing attention, particularly in arid regions with limited freshwater habitat. One approach to estimating energetic health of aquatic ectotherms is scope for growth (SFG)—the net energy available for reproduction and growth after meeting basic maintenance costs. We examined the relationships between temperature, clearance rates, respiration rates, and other physiological parameters to estimate SFG of Popenaias popeii—a federally endangered mussel native to the semi-arid Rio Grande basin of the southwestern USA and Mexico. Scope for growth followed a three-phase pattern with values remaining stable but negative from 16 to 24°C, increasing and becoming positive from 24 to 28°C, and decreasing back down to negative values from 28 to 32°C. In New Mexico’s Black River, a last stronghold for P. popeii, seasonal thermal regimes show that maximum investment in growth and reproduction likely occurs from May to October, when positive SFG values are most common. Within this critical period, mid-summer increases from 28 to 32°C may temporarily dampen or eliminate growth and reproduction in P. popeii as SFG decreases from peak to negative values. Management of flow to minimize thermal stress during mid-summer appears critical to maximizing growth and reproduction of remaining populations.

Assessing the status of several migratory fishes in the Mobile River Basin, Alabama, has been complicated due to a general lack of historical data on their life history, habitat requirements, and distributions. Whether distributions were restricted by natural or man-made barriers to migration is difficult to answer because few scientific collections were made before dams were built, and the earliest dams were built at the largest biogeographic barrier in the basin: the geological fall line. Therefore, we used what information was available, including anecdotal information, primarily records from archived newspapers and government reports, to describe the ranges of six migratory species prior to the construction of dams in the Mobile Basin. We describe the complicated history of Alabama Shad Alosa alabamae and show that range declines may have been masked by the stocking of American Shad Alosa sapidissima in the late 19th century. We show that Gulf Sturgeon Acipenser oxyrinchus desotoi probably migrated well above the fall line in the Coosa River, and may have been sympatric with Lake Sturgeon Acipenser fulvescens. We found no records of Alabama Sturgeon Scaphirhynchus suttkusi above the fall line. American Eel Anguilla rostrata migrated above the fall line in every Mobile Basin river before dams were built. Finally, Paddlefish Polyodon spathula may have once occurred above the fall line in at least two rivers, but they persist today in impounded reaches in the coastal plain, unlike some other species. We hope that future work will continue to consider archival sources of information to re-trace the histories of imperilled species.

Objective: Movement of fish past dams can be facilitated by dedicated fish passage structures, navigational locks, and crested spillways, with the efficacy of a passage structure depending strongly on the nature of the system (height of the dam, flow rate, etc.) and the fish's behavior and swimming capability. However, once the fish have passed a dam, whether by using a mitigation structure or due to active translocation, they encounter a different habitat upstream versus in the tailrace, potentially affecting their ability to continue their upstream migration. Methods: Here, we had two objectives. First, we determined whether Paddlefish Polyodon spathula that successfully passed a structure continued their upstream migration in the Alabama River. Because assuring passage by tagged fish required that we move the fish past the dam, our second objective was to determine whether translocated fish exhibited fallback behavior (downstream drift or movement postrelease that would compromise their continued migration). We used both active and passive telemetry methods to quantify the postpassage movements of tagged and translocated Paddlefish. Result: Fish that were translocated above Claiborne Lock and Dam (CLD) exhibited upriver movements once translocated, and they exhibited no fallback (i.e., down-stream movement with delayed or no continuation upstream). Timing of movement relative to spawning periods did not influence initial fish movement or the likelihood of reaching the next upstream dam (Millers Ferry Lock and Dam [MFLD]; similar to 100 river kilometers upstream) within the first 30 days of observation, but more fish that were tagged and released during the early prespawn period made it to within 4.83 km of MFLD (the location of our closest receiver below MFLD) relative to fish from the prespawn or spawning period. Fish that were released above CLD had a lower probability of being subsequently detected downstream of their release sites compared to fish that were released below CLD. Conclusion: Our findings support that Paddlefish will continue their upstream migration once they have passed a structure, despite changes in habitat.

........................................................................................................................................ ii Acknowledgments ........................................................................................................................ iii List of Tables ................................................................................................................................ v List of Figures .............................................................................................................................. vi Chapter I: Evaluation of a shoreline rotenone application to control Largemouth Bass Micropterus salmoides recruitment in small impoundments ........................................................

Freshwater ecosystems are undergoing rapid thermal shifts, making it increasingly important to understand species -specific responses to these changes. Traditional techniques for determining a species' thermal tolerance are often lethal and time consuming. Using the enzyme activity associated with the electron transport system (ETS; hereafter referred to as enzyme assay) may provide a non -lethal, rapid, and efficient alternative to traditional techniques for some species. We used largemouth bass Micropterus salmoides (Lacepede, 1802) to test the efficacy of using an enzyme assay to determine thermal tolerance and respiratory exploitation in response to variable acclimation temperatures. Three tissue types were dissected from fish acclimated to 20, 25, or 30 ?C and used in ETS assays at temperatures ranging from 7.5 to 40 ?C. While there were significant differences among tissue types and acclimation temperatures, maximal enzyme activity occurred from 25.23 to 31.91 ?C. Fish lost equilibrium at 39-42 ?C in traditional CTmax trials, significantly higher than the upper optimum range determined via enzyme assays. The ratio of enzyme activity to measured whole organism respiration rate decreased with increasing water temperature, with the largest changes occurring at the upper optimum thermal range determined by enzyme assays. Our results indicate that ETS analysis may prove useful for obtaining biologically relevant thermal tolerances.

Objective: Altered temperature and dissolved oxygen (DO) regimes in the tailwaters below dams can cause stress to fish. Despite their widespread distribution in rivers across North America, Freshwater Drum Aplodinotus grunniens have received little attention relative to the effects of these potential stressors. Quantifying fish swimming performance and kinematics in simulated tailwater conditions can help to determine how riverine species are affected by dam water releases, with the ultimate goal of identifying improved management strategies for these systems. Methods: We quantified Freshwater Drum swimming performance and kinematics by measuring critical swimming speed (in both relative [RUcrit; body lengths/s] and absolute [AU(crit); cm/s] units), tailbeat frequency, tailbeat amplitude, and Strouhal's number under all combinations of low-DO (4 mg/L), normoxic (9 mg/L), and high-DO (14 mg/L) conditions at low (10 degrees C), intermediate (20 degrees C), and warm (30 degrees C) water temperatures using both 90- and 850-L swim flumes. Result: Dissolved oxygen at these concentrations did not affect swimming performance. The effect of temperature on swimming performance depended on fish size; RUcrit, AU(crit), and tailbeat frequency decreased with fish length but increased with temperature. In contrast, tailbeat amplitude increased with fish length but did not differ across temperatures. Conclusion: These results suggest that acute low- and high-DO exposure within the tested range may not affect swimming performance or kinematics. However, the influence of temperature on Freshwater Drum swimming performance suggests that the ability of fish to hold position in a tailrace or to successfully pass upstream of a dam may vary seasonally and may depend on the depth from which water is released from a reservoir, as release depth determines the water temperature.

ObjectiveWe used two approaches, fish hard-part microchemistry and genetics, to quantify effects of low-use lock-and-dam structures on riverine fish movement. Each approach varied in temporal scope, with microchemistry addressing effects within a lifetime and genetics addressing effects across generations.MethodsWater samples and individuals of two species (Paddlefish Polyodon spathula and Smallmouth Buffalo Ictiobus bubalus) were collected from four river sections that were separated by three low-use lock-and-dam structures on the Alabama River. Quarterly water samples were collected from 15 sites during 2017-2018, and concentrations of Sr, Ba, Mn, Mg, and Ca were quantified using mass spectrometry.ResultWater elemental signatures were spatially variable but temporally consistent. The Sr:Ca ratios in fish hard parts differed significantly among river sections for both species. Additionally, discriminant function analyses classified fish to their river capture section with accuracy between 55% and 74% for Paddlefish (errors nearly always assigned individuals to adjacent river sections) and 37-47% for Smallmouth Buffalo. Population genetic analyses included fish from each river section, as well as from Alabama River tributaries and a neighboring watershed. Genotyping-by-sequence techniques identified 1,889 and 3,737 single nucleotide polymorphisms postfiltering in Paddlefish and Smallmouth Buffalo, respectively, which we used to estimate population diversity indices and conduct differentiation analyses. Analysis of molecular variance, discriminant analysis of principal components, Bayesian clustering, and pairwise comparisons of F-ST values indicated no strong evidence for genetic divergence in either species among river sections.ConclusionWithin-lifespan results based on hard-part microchemistry suggested a potential for population isolation. However, longer-term genetic effects were not apparent, possibly because the life span of these large and relatively long-lived species means that few generations have passed since dam construction, and there could be sufficient mixing or population connectivity to prevent genetic divergence across river sections, particularly at the most downstream structure.

Enhancements to acoustic telemetry technology now allow for tracking aquatic animal movements at multiple spatial and temporal scales. While large acoustic arrays allow for broad-scale tracking of movement and migrations at scales of thousands of km across multiple years, more focused smaller arrays offer the potential to quantify fine-scale movement across shorter time frames. Investigators seeking to quantify movement at multiple scales may require a double-tagging approach if their telemetry systems and tag capabilities are different (e.g., 69 kHz for broad-scale, and 307 kHz for sub-meter fine-scale). We tested multiple double-tagging approaches (InnovaSea-Vemco V9 and HTI-495LY tags) for American shad Alosa sapidissima during three individual tank survival experiments including: 1) two free-floating acoustic tags and a dart tag, 2) two acoustic tags attached to one another and a dart tag, and 3) two acoustic tags attached to one another with no dart tag and revised handling and tagging techniques to reduce stress. In each experiment, we used a mixed effects Cox's proportional hazard model to test for differences in relative survival between groups (double acoustic tagged and control fish). At the completion of each experiment, all fish were X-rayed to evaluate tag placement in the body cavity. During the first experiment, American shad that received two free-floating tags and a dart tag had significantly lower relative survival compared to control fish after three weeks. The second experiment with treatment fish receiving two attached tags and a dart tag still had lower survival compared to control fish, but the magnitude of survival differences between treatment and control was lower compared to experiment one. In the third experiment, when two attached tags were used, dart tags were eliminated, and changes to fish handling and tagging techniques were implemented (new tagging apparatus, addition of lubricant, and different fish orientation) survival was equal among treatment and control fish. X-ray images showed distinct differences in post-mortem tag positioning between the first experiment (misaligned tags) compared to the second and third experiments (tags horizontally aligned within intestinal tract). American shad are generally difficult to study experimentally and sensitive to collection, handling, and surgical implantation. Our study showed strong evidence that attaching two acoustic tags to one another to create a single, larger tag improved survival and reduced internal tag misalignment. Fine- and broad-scale acoustic telemetry studies can be achieved with aquatic animals, but care must be taken with all species, and particularly those susceptible to handing stress to minimize tagging effects (e.g., mortality, altered movement behaviors, and tag burden).

Dams alter many aspects of riverine environments and can have broad effects on aquatic organisms and habitats both upstream and downstream. While dams and associated reservoirs can provide many services to people (hydropower, recreation, flood control, and navigation), they can also negatively affect riverine ecosystems. In particular, hydropeaking dams affect downstream fish habitats by increasing variability in discharge and temperature. To assess the effects of Harris Dam on the Tallapoosa River, AL, operating under an adaptive management plan implemented in 2005, we sampled fish for community analyses from four sites on the river: three in the regulated reach downstream of the dam, and one unregulated site upstream. Fish were collected every other month using boat/barge electrofishing. We used Shannon's H, nonmetric multidimensional scaling (NMDS), a multiresponse permutation procedure (MRPP), and indicator species analysis to quantify patterns in fish assemblage structure and determine how assemblages varied among sites. NMDS and MRPP indicated significant fish assemblage differences among sites, with the tailrace fish assemblage being distinct from the other downstream sites and sites becoming more similar to the upstream, unregulated site (relative to fish assemblages) with distance downstream of the tailrace. The tailrace fish assemblage included higher proportions of rheophilic species that may be better suited to variable and/or high flows. Altered fish assemblages demonstrated continued effects of Harris Dam on the downstream aquatic systems, particularly close to the dam. These effects may indicate that further mitigation should be considered depending on conservation and management goals.

Impacts of low-head, run-of-the-river dams on migratory fish movements depend on the structure of the dam, river hydrology, and the ability of fish to navigate the tailrace environment. Here, we present results from a 3-year movement study in which telemetered Paddlefish Polyodon spathula and Smallmouth Buffalo Ictiobus bubalus were tracked as they approached and sometimes migrated past Claiborne Lock and Dam (CLD), a low-use low-head lock-and-dam structure on the Alabama River. A spillway portion of the dam is periodically inundated during early spring, dependent on precipitation and releases from the next upstream dam. Our goals were to (1) quantify dam passage rates for both species, (2) assess the importance of factors affecting passage success, and (3) quantify space use patterns in the tailrace. Both species exhibited annual upstream migrations during the study period. Correlation of daily average river position versus the CLD hydrograph showed that movements by both species appeared to be related to flow variation. Passage efficiency (range = 10.7-30.2%) varied between species and among years, with tailrace gauge height being the most important factor affecting passage success for both species. Using an acoustic positioning system in the tailrace, we quantified space use by individuals of both species. Time spent in the tailrace (mean = 3.9 continuous days; range = 0-94 continuous days) did not differ between individuals that passed and those that did not pass. Fine-scale position estimates showed that space use differed between species, across gauge heights, and between individuals that passed and those that did not pass. Differential space use may be due to the species' habitat preferences or swimming abilities. Our findings provide information to inform potential design of mitigation structures, and they also identify the need for additional work required to more fully understand the mechanisms of passage success versus failure for these and other native potamodromous species.

Management of fish populations for conservation in thermally variable systems requires an understanding of the fish's underlying physiology and responses to thermal stress. Physiological research at the organismal level provides information on the overall effects of stressors such as extreme temperature fluctuations. While experiments with whole organisms provide information as to the overall effects of temperature fluctuations, biochemical assays of thermal stress provide direct results of exposure that are both sensitive and specific. Electron transport system (ETS; Complex III) assays quantify a rate-limiting step of respiratory enzymes. Parameters that can be estimated via this approach include optimum thermal temperature (Topt ) and optimal breadth of thermal performance (Tbreadth ), which can both be related to organismal-level temperature thresholds. We exposed enzymes of seven fish species (native fish chosen to represent a typical community in Alabama streams) to temperatures in the range 11-44°C. The resultant enzymatic thermal performance curves showed that Topt , the lower temperature for enzyme optimal thermal performance (Tlow ), the upper temperature for enzyme optimal thermal performance (Tup ), and Tbreadth differed among species. Relationships between enzymatic activity and temperature for all fish followed a pattern of steadily increasing enzyme activity to Topt before gradually decreasing with increasing temperature. A comparison of our enzyme optimum and upper-temperature limit results versus published critical thermal maxima values supports that ETS Complex III assays may be useful for assessing organismal-level thermal tolerance.

Grove L, Stell EG, Grove LJW, Wright RA, DeVries DR. 2022. Influence of blueback herring, Alosa aestivalis, on zooplankton in a southeastern US reservoir. Lake Reserv Manage. XX:XXX-XXX. Forage fishes like blueback herring (Alosa aestivalis) have been widely introduced, sometimes without careful consideration of potential ecological consequences. We compared biotic and abiotic factors before and after blueback herring introduction into Lewis Smith Lake, Alabama (United States), and tested for diet overlap among planktivorous species to quantify their potential ecological influences. Abiotic and biotic factors varied among regions of the lake, consistent with differences in agricultural practices and nutrient input within each region. Secchi depth increased and zooplankton density decreased, while chlorophyll a remained unchanged relative to before blueback herring introduction. Juvenile and adult blueback herring and threadfin shad (Dorosoma petenense) consumed the same zooplankton taxa; however, blueback herring consumed significantly larger individuals and significantly greater numbers of zooplankton than threadfin shad. Blueback herring also selectively consumed larger zooplankton than the average size in the reservoir population, while threadfin shad did not. Threadfin shad and blueback herring positively selected Bosmina and cyclopoid copepods. The taxonomic overlap and size selectivity in prey choice suggest that if blueback herring reduce larger zooplankton, threadfin shad and blueback herring diets are likely to increasingly overlap. Because of their differences in feeding strategies (i.e., related to zooplankton size differences) and habitat preferences, current evidence for potential competitive interactions between these planktivores appears limited; however, longer term concerns are that blueback herring could eventually reduce larger zooplankton to the extent where they would increasingly compete with threadfin shad as the most abundant forage fish in Lewis Smith Lake.

The introduction of additional forage fish species to enhance sport fisheries is a common management strategy in lakes and reservoirs. However, illegal introductions occur without consideration of all potential ecological consequences. Introduction of Blueback Herring Alosa aestivalis as a forage fish to enhance recreational fisheries has been controversial, with several illegal introductions documented in the southeastern United States. We quantified the caloric density of introduced Blueback Herring and native Threadfin Shad Dorosoma petenense in Lewis Smith Lake, Alabama, to determine their potential values as prey to piscivorous fish. Caloric density estimates were then incorporated into bioenergetics simulations for Largemouth Bass Micropterus salmoides, Alabama Bass Micropterus henshalli, and Striped Bass Morone saxatilis to estimate their growth potential given different diet compositions. Piscivore diet composition from before the introduction of Blueback Herring was also incorporated into bioenergetics simulations for comparison with post-introduction scenarios. Caloric density of Blueback Herring was higher than that of Threadfin Shad across all seasons, and consequently, bioenergetics simulations predicted increased growth potential for Largemouth Bass, Alabama Bass, and Striped Bass with increased proportions of Blueback Herring in their diets. The simulated growth effect of shifting consumption from Threadfin Shad to Blueback Herring was smaller for Largemouth Bass versus Striped Bass because Striped Bass were far more piscivorous than Largemouth Bass, with Alabama Bass intermediate. Simulated pre-Blueback Herring piscivore diets resulted in less growth relative to what was observed for all post-introduction simulations. Although Blueback Herring had higher caloric density values than Threadfin Shad, overall ecological impacts of their introduction are not yet fully understood and could likely also include negative impacts on these piscivores. As such, our findings represent one aspect of the overall, potentially complex effect of introduced Blueback Herring as an additional forage fish for piscivores.

Estuaries present a set of unique challenges for freshwater fish. In addition to basic physiological challenges, the influx of salinity can affect prey availability and can influence resource consumption. Diets of coastal Largemouth Bass Micropterus salmoides were surveyed from three sites in the Mobile Bay estuary, Alabama, USA, from April 2011 to April 2015. A large proportion of Largemouth Bass consumed blue crabs Callinectes sapidus (proportion occurrence [PO]=0.38) and mud crabs Panopeus spp. (PO=0.24). Largemouth Bass also consumed grass shrimp Palaemonetes spp. (PO=0.16), Gulf Menhaden Brevoortia patronus (PO=0.14), and mysid shrimp Mysidopsis spp. (PO=0.12). Prey diversity was greater at the lower estuary site (Fowl River) than at the sites in the upper estuary (Bay Minette and D'Olive Bay). A principal components analysis based on the biomass diet data revealed that invertebrates were the most important prey resource for coastal Largemouth Bass, with finfishes playing a secondary role. Seasonal inputs of estuarine fish species, such as Gulf Menhaden, represented an important prey resource in the diets of Largemouth Bass during both spring and summer.

Organisms that live in coastal estuaries often experience significant seasonal and annual fluctuations in salinity that they must either endure or move to avoid. Largemouth Bass Micropterus salmoides is a freshwater fish that lives in coastal estuaries and does not migrate/move to avoid seasonal salinity increases. Additionally, estuarine Largemouth Bass exhibit growth rates, condition factors, and life history strategies that differ from their inland counterparts. These differences suggest the potential for physiological adaptations to tolerate and even thrive in estuarine environments. We compared swimming performance (quantified as critical swimming speed, Ucrit) of Largemouth Bass (280–404 mm total length) from an Alabama estuarine population versus an inland population at 0, 4, 8, and 12 ppt salinities to test for physiological performance-based adaptation to tolerate elevated salinities. Ucrit values did not differ between inland and estuarine Largemouth Bass nor were there any salinity effects. Although inland and estuarine Largemouth Bass may possess different physiological mechanisms for tolerating salinity, those mechanisms did not affect swimming performance.

Many applications of otolith chemistry use the ratios of strontium (Sr) and barium (Ba) to calcium (Ca) as indicators of salinity exposure, because typically, as salinity increases, Sr concentration increases and Ba concentration decreases. However, these relationships are nonlinear, can be confounded by temperature, and investigations of salinity and temperature effects on otolith chemistry produce varied results. To determine the relationships of temperature and salinity on Sr:Ca and Ba:Ca in otoliths, we used free ranging Gulf Killifish (Fundulus grandis) in the northern Gulf of Mexico. This species is ideal because it is euryhaline and exhibits limited movements. Otolith edge Sr:Ca and Ba:Ca ratios were related to the previous 30-day mean salinity and temperature experienced by fish. The best model to describe otolith Sr:Ca was one that included a positive asymptotic relationship for both salinity and temperature. However, the salinity asymptotic maximum was reached at 10 psu and changes in otolith Sr:Ca above 10 psu were indicative of temperature changes. Otolith Ba:Ca exhibited an exponential decreasing relationship with salinity, and an exponential increasing relationship with temperature, and these two models combined best explained otolith Ba:Ca. Above 10 psu, the modeled Ba:Ca ratio continued to decrease demonstrating that this ratio may be indicative of salinity changes beyond this value. Therefore, using both Sr:Ca and Ba:Ca could be beneficial in reconstructing fish environmental histories. Temperature effects on otolith element ratios could confound past salinity reconstructions as well and must be a result of endogenous processes, given that no relationship between temperature and water chemistry existed.

Roberts CM, DeVries DR, Wright RA. 2018. Introduced yellow perch in two Southeastern US reservoirs: ecological interactions with resident fishes. Lake Reserv Manage. 34:141153.Yellow perch (Perca flavescens) has been introduced into Southeastern US drainages outside its native range; unfortunately, the effects of these introductions at the edge of their distribution on resident fishes have not been well documented. To determine the potential interactions between introduced yellow perch and resident fishes, we quantified diets of multiple life stages over 2 yr in 2 Alabama reservoirs. Temporal and spatial co-occurrence between larval yellow perch and native fishes was limited, and diet overlap was generally low at all life stages. Juvenile yellow perch were consumed by Micropterus spp. in both lakes during spring, suggesting some potential benefit for native piscivores. We suggest minimal negative effects of yellow perch on native fishes in these Southeastern US systems due to their generalist diet, early spawning period, and cool water temperature requirements. In addition, yellow perch may represent an alternative prey resource for piscivores.

Abstract As part of a study of aquatic faunal community changes along riverine-lacustrine transition zones upstream of Lewis Smith Reservoir in northwest Alabama, USA, we collected crayfish from 60 sites in the Sipsey Fork, Brushy Creek, and selected tributaries (Black Warrior River system). After finding two unexpected and possibly-introduced crayfish species, we expanded our investigation of crayfish distributions to include crayfish obtained from stomachs of black bass (Micropterus spp.) caught at seven sites in the reservoir. To explore what crayfish species were in the drainage historically, we examined museum databases as well as stomach and intestinal contents of a variety of preserved fishes that were caught in the Sipsey Fork and Brushy Creek drainages upstream of the reservoir in the early 1990’s. Of the seven crayfish species collected, one, Orconectes (Procericambarus) sp. nr ronaldi, was not previously reported from Alabama, and another, O. lancifer, was not reported from the Black Warrior River system prior to the study. Three are known or possibly introduced species. Upstream of the reservoir, the native species Cambarus obstipus, C. striatus, and O. validus were common. The same three species were found in fish collected in the 1990’s. Orconectes perfectus was found only in the reservoir but may be native to the drainage. Orconectes lancifer was in the reservoir and in stream reaches influenced by the reservoir. Evidence points to O. lancifer being introduced in the drainage, but this is uncertain. Orconectes sp. nr ronaldi was found in a relatively small portion of Brushy Creek and its tributaries, in both flowing and impounded habitats, and may be introduced. Orconectes virilis is introduced in Alabama and was found only in stomachs of fish collected in the reservoir.