| Evil minions | |
My research and teaching has benefitted greatly through collaborations with a long list of energetic, enterprising, and often entertaining undergraduate and graduate students. The following either completed a research project in my lab or made significant progress towards doing so. |
|
Behavioral interactions between the endangered Okaloosa and introduced brown darters in northwest Florida Jon arrived at Tulane University with a burning desire to expand his collection of figurines, but I encouraged him to follow a darker path. His research focused on evaluating the strength of behavioral interactions between endangered Okaloosa darters and brown darters that co-occur in a number of streams on and around Eglin Air Force Base in northwest Florida. Jon |
|
Habitat use and foraging ecology of largemouth bass and other predatory fishes in the lower St. Johns River, Florida Mark |
|
Ecological determinants of mosquito populations following Hurricane Katrina Kevin |
|
Survival of the finless: effects of fin clipping on brown darters
Caroline |
|
Habitat selection by the Florida blenny (Chasmodes saburrae) Seagrass beds are often comprised of several plant species growing adjacent to one another. Many mobile organisms occupying these seagrass beds are distributed non-randomly, suggesting a preference for one habitat type over another. For example, the Florida blenny (Chasmodes saburrae) is more abundant in turtlegrass than in adjacent shoalgrass in the northeastern Gulf of Mexico. I performed field surveys and behavioral experiments to test for behavioral preferences and to evaluate the role that predators play in shaping habitat use by the Florida blenny. Field surveys were inconclusive, probably because this species is patchily distributed. Behavioral choice experiments indicated that blennies preferred turtlegrass over shoalgrass, even in the absence of predators or food resources. Predation experiments did not demonstrate differential survival of blennies in turtlegrass and shoalgrass, because the gag grouper I used were not aggressive predators. However, blennies greatly increased their use of refuges within behavioral tanks when predators were present. Therefore, it appears that blennies are sensitive to the risk of predation and patterns of habitat use observed in the field may in part reflect avoidance of abundant predators in seagrass beds. Rachel |
|
Effects of habitat complexity on predator foraging efficiency I performed a laboratory experiment to determine whether a suite of common wetland invertebrate predators would prey upon the locally abundant least killifish (Heterandria formosa) and whether increasing plant density would facilitate prey capture rates. Creeping water bugs (Naucoridae), giant water bugs (Belostomatidae), and crayfish fed upon least killifish to some degree, whereas dragonfly larvae (Aeschnidae) were voracious predators of least killifish. Density of simulated Ludwigia plants had little effect on foraging rate. Although there was little evidence for plant facilitation of invertebrate foraging success, it appears that increasing plant density does not adversely affect these predators as much as it does fish Marisa |
|
Habitat selection and reproductive life history of pipefishes at Seahorse Key, Florida. I examined habitat use and aspects of reproductive life history of pipefishes (Family Syngnathidae) in adjacent beds of shoalgrass (Halodule wrightii) and turtlegrass (Thalassia testudinum) at Seahorse Key, Florida during July 2001. Gulf pipefish (Syngnathus scovelli) and dusky pipefish (S. floridae) were strongly affected by zonation along Seahorse Key -- no pipefishes were collected from over sand, pipefishes were rarely collected from beds of shoalgrass, and high numbers of pipefishes were collected from beds of turtlegrass. Gulf pipefish were significantly more abundant that dusky pipefish. I wanted to test the differences in habitat preference with a controlled laboratory experiment to see if habitat choice reflected a preference for shoalgrass over turtlegrass, or if differences reflected greater survival in one seagrass over another. Laboratory behavioral experiments indicated that pipefishes showed a preference for habitat, and these preferences change with age. Adult pipefishes showed a strong preference for turtlegrass, whereas smaller pipefishes showed a preference for shoalgrass. I also used field collections of abundant Gulf pipefish to test predictions about reproductive life history in a system where males carry and nourish developing embryos in an abdominal brood pouch. The sex ratio of adult Gulf pipefish was highly skewed towards males, perhaps reflecting skewed production of male embryos. There was no relationship between the size of brooding males and the number or total mass of offspring in a clutch. However, there was a significant negative relationship between number of offspring and individual mass of offspring, indicating a tradeoff between these key life history traits. Gianna |
|
Marking studies of brown darters and endangered Okaloosa darters Visible implant elastomer (VIE) is a recently developed internal mark that has been used on a variety of fishes, although little research has focused on small-sized species. My research assessed the utility of using VIE to mark brown darters ( Etheostoma edwini ) and endangered Okaloosa darters ( E. okaloosae ). In the laboratory, 96% of brown darters retained their marks after one month and no fish died as a result of the marking procedure. Visually oriented largemouth bass ( Micropterus salmoides ) attacked brown darters with a yellow mark more often than fish with red or clear marks. However, mark color had no effect on number of brown darters eaten by largemouth bass. In the field, I marked Okaloosa darters to evaluate movement patterns after 24 hours and one month. Okaloosa darters showed relatively uniform movement upstream and downstream of the release point and very few fish switched sides. There was little difference in distance moved after one month, suggesting that Okaloosa darters have relatively small home ranges. Recapture rates differed little after a month, suggesting mortality was low. These low movement and mortality rates are striking because Hurricane Ivan hit the study area between censuses. This study demonstrates that VIE marks are useful for studying small-sized fishes, including many of the species that are imperiled due to habitat loss, sedimentation, and other threats to streams in North America. Dan defended in May 2005 and is currently a graduate student at Auburn University. |
|
Reproductive
life history of the blackbanded darter, Percina nigrofasciata,
Blackbanded darters, Percina nigrofasciata, were collected from Ten Mile and West Turkey Creeks in Okaloosa County, Florida, over a three-year period to study variation in reproductive life history traits. Fish were measured and gonad development and clutch parameters were evaluated. Males were more abundant and larger than females. Males and females were reproductively active year round, and female gonosomatic index peaked during the spring. Reproductive activity was similar among years. The smallest reproductively active female and male were 24.7 and 28.6 mm, respectively. Clutch size ranged from 4 to 78 eggs, and averaged 26.7 eggs per female. Clutches containing ripe eggs were the same size as clutches containing mature eggs, which indicates that eggs are released in a single spawning event. Larger females produced more eggs than smaller females, but mass and diameter of individual eggs was not related to female size. No relationships were found between diameter or mass of eggs and size of clutch, indicating the absence of a trade-off between these life history traits. Significant differences in life history traits were not apparent between the two creeks. Duration of breeding season was significantly longer than previously reported for a population in Alabama, indicating that geographic variation exists in this species and warrants further study. Myra |
|
Summer patterns of microhabitat use by
blackbanded darters in Northwest Florida Blackbanded darters ( Percina nigrofasciata ) are small benthic fish found in streams of the Gulf and southern Atlantic Coastal Plains. Blackbanded darters are common in streams draining Eglin Air Force Base (Niceville, Florida), where they co-occur with and may adversely affect the endangered Okaloosa darter ( Etheostoma okaloosae ). To begin evaluating possible interactions between these species, I quantified abundance of blackbanded darters and examined their patterns of microhabitat use during the summer of 2002. Fish were counted in 20-m stream sections while snorkeling and their positions were marked with size-coded survey flags. I then determined the substrate type, bottom flow, midwater flow, canopy cover, distance to bank, distance to open sand, and depth for each fish. Additional data on habitat availability and water quality were collected at the same time by researchers studying Okaloosa darters. Blackbanded darters preferred streams that were deep, fast, wide, and covered by a well-developed canopy. Fish were typically found on or near patches of sand. Patterns of microhabitat use varied among size classes and may reflect differences in vulnerability to predators. Larger fish occupied deeper and faster flowing water than small fish. Similarly, larger fish were more likely to occupy open sand and stray further away from abundant cover along stream margins, where small blackbanded darters were more likely to co-occur with Okaloosa darters were positively correlated, indicating that these species have similar habitat preferences. Additional research on feeding habits and behavior is needed to further address interactions between blackbanded and Okaloosa darters. Melissa |
|
The effects of paddlefishophilia on survival of paddlefish Mary was greatly enamored with paddlefish, so we decided to order a large batch of paddlefish larvae in order to study the effects of salinity on early development and survival. This was an ill-fated decision because a) our lab was set up to support research on small and hardy estuarine fishes and b) we must have been shipped a cohort of offspring that were not interested in becoming part of Mary's study. Suffice it to say that we quickly acquired a large collection of preserved specimens for the Jacksonville University teaching collection. Mary worked on a number of other projects at Jacksonville University, graduated, got married and now teaches biology, marine science, and environmental science courses at Berea High School in Ohio. Visit Mary's website. |
|
Physical structure and zonation of seagrass beds of Seahorse Key, Florida I quantified the physical structure and zonation of seagrass beds of Seahorse Key, Florida. I used a 1-m2 quadrat to visually estimate the relative abundance of bare sand, shoal grass (Halodule wrightii), and turtle grass (Thalassia testudinum) along transects perpendicular to the shoreline. I measured the average length, density, and biomass of stems collected from within 452-cm2 quadrats. Depth increased with distance away from the shoreline, although the slope of the shoreline and associated tidal influence varied among transects. Zonation was apparent along this depth gradient, with bottom substrate shifting predictably from bands of bare sand (40 m wide), to shoal grass (26 m wide), and then to turtle grass (>300 m wide). Habitat structure varied appreciably among these zones, with sand providing no structure, shoal grass providing high densities of relatively short blades, and turtle grass supporting lower densities of longer blades. Plant biomass, another measure of habitat complexity, also increased away from the shoreline. Zonation of habitats, which likely reflects differences in tidal exposure and biological interactions among plant species, provides a diversity of habitats for coastal fishes and invertebrates. Kristen |
|
Foraging efficiency of largemouth bass
in introduced and native species of submerged aquatic vegetation. Eurasian water milfoil (Myriophyllum spicatum) was introduced to North America before 1900 and has subsequently spread throughout much of eastern North America, including the Lake Pontchartrain estuary in Louisiana. When an exotic species of vegetation is introduced to an aquatic ecosystem, changes in fish and invertebrate community structure are often observed, although the actual mechanisms of change remain unclear. One possible mechanism that could contribute to changes in fish community structure is the morphology of the introduced species. The growth form of the invading plant could adversely affect foraging efficiency of some predators, and thereby alter food web structure. For example, M. spicatum is structurally complex with leaves that emerge from the stem in whorls. In contrast, native tapegrass (Vallisneria americana) has simple, flat blades. In this laboratory study, I tested the hypothesis that the foraging efficiency of juvenile largemouth bass (Micropterus salmoides) would be lower in M. spicatum than in V. americana. Also, I examined the effect of plant stem density on foraging efficiency of juvenile largemouth bass. During the first five minutes, plant type (M. spicatum or V. americana) had no effect on forage rates of juvenile largemouth bass. Forage rates were much lower in habitats with low stem density, possibly because there was not enough cover for risk-sensitive, juvenile largemouth bass to forage freely. After six hours, forage rates in habitats with high stem density were similar for both plant types, whereas forage rates in habitats with low stem density were significantly lower in V. americana than in M. spicatum. Since juvenile largemouth bass prefer to occupy higher densities of submerged aquatic vegetation than lower densities, these findings could be a reflection of their habitat preference. It appears that the structurally complex whorls of introduced M. spicatum begin to allow for the successful detection and capture of prey by juvenile largemouth bass at lower stem densities than native V. americana. Cerinda |
|
Life history characteristics of the blackbanded darter
Bridget |
|
Effects of predators on habitat use of pinfish, Lagodon rhomboides
Paula completed her MS in Fisheries at the University of Florida and then later switched gears by obtaining a degree in personal counseling. She is living happily ever after in Hogtown, Florida. |
|
Ontogeny of habitat selection by pink shrimp I performed field and laboratory studies to determine whether pink shrimp (Farfantepenaeus duoarum) discriminate among adjacent species of seagrass, whether habitat preferences vary during ontogeny, and what mechanisms account for any patterns of habitat selection. Juvenile pink shrimp were consistently more abundant and smaller in size in beds of shoalgrass than in adjacent beds of turtlegrass. Field observations indicated that the abundance and size of potential predators was greater in turtlegrass, so I hypothesized that smaller shrimp preferred shoalgrass to minimize risk of predation. Initial experiments in small behavioral tanks produced results similar to field patterns, whereas experiments in larger tanks provided equivocal results. Tracking individual shrimp was problematic in the larger tanks. Overall, it appears that there is a change in habitat preference with increasing size of juvenile shrimp. Future experiments should use improved marking techniques to better track shrimp during experiments. Simone |
|
Fish community structure within seagrass beds of Seahorse Key, Florida I compared assemblages of fishes within bare sand, shoalgrass (Halodule wrightii), and turtlegrass (Thalassia testudinum) surrounding Seahorse Key, Florida to determine the relative importance of these habitats. Otter trawls and throw traps were used to sample fishes in the three habitats at three different sites along the southern edge of the island. Fishes were preserved in the field, and later identified and measured in the laboratory. Percent composition, species evenness, species richness, total fishes, mean densities, and mean standard lengths were calculated for each habitat and location. Estimates of fish size and abundance depended upon type of sampling gear, with trawls providing better estimates for larger epibenthic fishes and throw traps providing better estimates for smaller benthic fishes. Gobiosoma robustum, Lagodon rhomboides, and Eucinostomus spp. were numerically dominant. Turtlegrass supported more species than shoalgrass, and sand supported very few species. Fishes were virtually absent from sand, benthic fishes were equally abundant in the two seagrass habitats, and pelagic fishes were more abundant in turtlegrass than in shoalgrass. The average size of fishes also differed among seagrass habitats, with turtlegrass supporting larger fishes than shoalgrass. Overall, it appears that the composition of fish assemblages varies considerably among adjacent seagrass habitats and that bare sand does not support a significant number of fishes. Courtney |
|
Habitat selection, predation, parasitism,
and distribution of grass shrimp along an estuarine gradient Heather earned a BS in Marine Science from Jacksonville University and her MS in Biological Sciences at Georgia Southern University. At JU, she was part of a core group of hard-working young marine biologists who helped me be quite productive. At Georgia Southern, she examined how patterns of habitat use by four species of grass shrimp vary along an estuarine gradient. Heather used laboratory behavioral experiments to determine underlying mechanisms responsible for patterns of habitat use observed in the field. Finally, Heather used laboratory foraging experiments to determine whether parasites increased the vulnerability of grass shrimp to piscine predators. Heather |
|
Habitat use by the brittlestar Ophioderma brevispinum in seagrass beds of Seahorse Key, Florida I examined patterns and mechanisms of habitat selection by the brittlestar Ophioderma brevispinum in grassbeds adjacent to Seahorse Key, Florida. I quantified the density of brittlestars in adjacent beds of shoalgrass (Halodule wrightii), turtlegrass (Thalassia testudinum), and algae-filled patches within beds of turtlegrass. Boat propellers, foraging activities of stingrays and horseshoe crabs, and other minor disturbances generate these patches. Rather than being distributed randomly among habitats, brittlestars were significantly more abundant in beds of turtlegrass and algae-filled patches contained therein. I collected few brittlestars from shoalgrass and none from barren sand. I then performed behavioral experiments in the laboratory to identify behavioral mechanisms underlying observed patterns of habitat use in the field. In the absence of predators and food resources, brittlestars were offered a choice of equal-sized patches of bare sand, turtlegrass, drift algae, and a mixture of turtlegrass and drift algae. Significantly more brittlestars selected vegetated habitats than bare sand. Also, brittlestars tended to be more active at night than during the day. Brittlestars used the three vegetated patches equally, suggesting that shade effects were more important than structure per se. To test this hypothesis, I offered brittlestars a choice of shaded and non-shaded patches of barren sand. During the day brittlestars tended to associate with shaded patches, whereas there was no preference at night. Based on field and laboratory studies, it appears that the brittlestar O. brevispinum has a strong preference for the cover provided by dense beds of turtlegrass and drift algae-filled patches contained therein. Small-scale disturbances such as stingray foraging and propeller scars appear to pose little threat to brittlestars, whereas large-scale loss of turtlegrass beds in the Gulf of Mexico will likely adversely affect population dynamics and distribution of brittlestars such as O. brevispinum. Orlena |
|
Field
and laboratory studies of the life history and burrowing behavior of
two Everglades crayfishes Peggy has completed her doctorate and is now living happily ever after. |
|
Habitat use and ecology of grass shrimp in Mississipi River delta
Susan has finished her MST and is now a high school teacher at The Young Women's Leadership School of East Harlem. She brings a group of students down each spring in order to collaborate on some muddy, odoriferous, and fun project. |
|
Effect of predation on habitat selection
byjuvenile pink shrimp, Farfantepenaeus duoarum. I studied abundance and distribution of juvenile pink shrimp (Farfantepenaeus duoarum) within seagrass meadows of Seahorse Key, Florida during summer 2004. I collected pink shrimp from adjacent beds of shoalgrass ( Halodule wrightii ) and turtlegrass ( Thalassia testudinum ) using a 1-m 2 throw trap. Shoalgrass contained higher densities of small juvenile pink shrimp, whereas lower densities of large juvenile pink shrimp. This pattern of ontogenetic shift in habitat use had been observed in four previous years of sampling at Seahorse Key. Previous research found that larger-sized juvenile pink shrimp showed a preference for turtlegrass, suggesting that size-based patterns of habitat use observed in the field reflect active habitat selection rather than differential mortality. I followed up on this research by testing the hypothesis that habitat selection by juvenile pink shrimp is motivated in part by predation – larger juvenile pink shrimp living among the short, thin blades of shoalgrass are more vulnerable to fishes and other predators than similar sized pink shrimp living among the long, thick blades of turtlegrass. Laboratory predation experiments indicated that predation rates on small juvenile pink shrimp did not differ between turtlegrass and shoalgrass, whereas predation rates on large juvenile pink shrimp was higher in shoalgrass. My results indicate that pink shrimp undergo a shift in habitat preference during their ontogeny and that this shift is motivated in part by risk of predation. A recruitment bottleneck may occur when the relative distribution and abundance of shoalgrass and turtlegrass change drastically – which has been documented in Florida Bay and other critical nursery areas in Florida. Lauren |
