Graduate Student Symposium

11th Annual Graduate Student Symposium
March 31-April 1 , 2008
ABSTRACTS
Graduate Student Symposium Organizing Committee:

Abstracts & Program: Jenney Kellogg, Dana Bigham, Felipe Carvalho. Audiovisual: Matt Lauretta, Nate Johnson, Patrick O’Rouke. Food: Kerry Weber, Paula Viveros, Emily Mitchem. Facilities: Aaron Bunch, Towns Burgess, Eric Cassiano,Jared Flowers, John Hargrove, Eric Thomas Dr. Debra J. Murie and Dr. Shirley Baker (Faculty Coordinators)

THE SEAHORSE SOUND SURVEY. Paul Anderson [William J. Lindberg]

A survey of public aquaria characterized the range of ambient noise to which seahorses (chosen as a representative marine ornamental aquarium fish) are exposed in captivity. The survey kit included a questionnaire, a hydrophone and digital recorder, a digital camera, and instruction manual. Nine public aquarium facilities nationwide participated in the survey, returning data on 42 seahorse aquaria. Within the low frequency range (<1000 Hz), total power of ambient noise profiles in the middle of the water column ranged from 113.3 to 139.9 dBrms SPL (re: 1 μPa), with a mean of 123.1 + 0.8 dB. At the tank bottom, total power ranged from 119.3 to 143.0 dB, with a mean of 130.7 + 1.1 dB. Among tank design specifications characterized from questionnaire data, I executed a MANOVA with Tukey’s Test comparisons to demonstrate that glass tanks were significantly louder than acrylic and concrete tanks, but not fiberglass tanks, at the middle of the water column. Noise profiles in both tank positions were also significantly louder in bare-bottom tanks than in tanks with a gravel substrate or plenum. The ranges of ambient noise reported here encompass values reported elsewhere from aquaculture facilities, and encompass levels shown to elicit a chronic stress response in the lined seahorse (Hippocampus erectus). Aquarists are thus advised to consider soundproofing recommendations in tank design.

POTENTITAL IMPACTS OF NON-NATIVE FISH IN NORTH MESOAMERICAN LAKES. Christian Barrientos [Jeffrey Hill]

Mesoamerica is a sub-tropical region that contains important natural resources shared among countries in the area. For example, Guatemala’s geographic attributes includes many inland water systems, including three major lakes with areas over 100 km2, which provide freshwater supply, transportation, tourism and fisheries. Despite the fact that these water bodies are under management, the natural resources such as fisheries have declined and still are under several threats, including overfishing, habitat destruction, pollution and the introduction of exotic species. The impact of exotic species on the native icthyofauna has not been quantified, although qualitative reports describe declines in species richness and abundance of native fish in those lakes. To investigate the state of a native fish community after the introduction of exotic species, we propose to: (1) identify establishment status of introduced species, (2) compare fish-community composition in Mesoamerican lakes, (3) identify importance of exotic species in fisheries, (4) compare reproduction of native and exotic species in different seasons, (5) use an ecomorphological approach to compare food resource use and overlap of natives versus exotic species, and (6) compare trophic level ecological effects of exotic species present in Mesoamerican Lakes.

EFFECTS OF CURRENT VELOCITY ON THE GRAZING RATES OF AN HERBIVOROUS SNAIL, Elimia floridensis Jess Beasley [Thomas K. Frazer/Craig Osenberg]

Current velocity is often considered the “master variable” in lotic systems. Variations in current velocity have profound effects on nutrient and gaseous exchange processes, sediment sorting, and patterns of distribution and abundance of both flora and fauna. While current velocity is known to alter grazer behavior, few studies have investigated the effect of current velocity on periphyton-grazer interactions, and of these studies, the majority have tended to use only two (or three) current velocity treatments. Because effects of current on grazer behavior are likely to be non-linear, these existing data are limited in their applicability. My study will use a flow tank to assess how the grazing rate of a herbivorous snail, Elimia floridensis, changes in response to current velocity. Grazing rates will be assessed on two substrates (ceramic tiles and artificial plants) at eight different velocities. Grazing rates will be assessed by comparing chlorophyll content as well as the ash free dry mass (AFDM) of periphyton remaining on grazed substrates with ungrazed substrates maintained under the same conditions but without snails. This work will be a facet of a larger integrated project, in which multiple flow-mediated effects are explored to more fully understand the processes that regulate algal dynamics in lotic environments

GAG GROUPER HABITAT, MOVEMENT, AND FITNESS Zy Biesinger [Ben Bolker/William Lindberg]

Gag Grouper, Mycteroperca microlepis, is an important grouper in the southeastern Unites States. Juveniles establish residency on sparsely distributed physical shelters then forage across the surrounding landscape. A more complete knowledge of how juveniles use this patchy reef habitat, and the consequences to demographic parameters, is important for understanding potential effects on population dynamics. Habitat selection theory gives the expectation that gag space use is affected by the amount and spatial arrangement of different habitat types in the landscape, and that differences in space use affect individual fitness. I plan to explore how landscape characteristics (e.g. fractional cover of different habitat types) affect movement decisions (e.g. home range size), which in turn affect individual fitness (e.g. size and weight). I will overlay high-resolution habitat maps with 3-D movement paths of acoustically tagged individuals to explore the relationship between landscape and movement. Using size and relative weight as proxies, I will connect the landscape-movement interaction to expected fitness.

A STATE-WIDE ASSESSMENT OF THE TOXIC ALGAL (MICROCYSTIN) THREAT IN FLORIDA LAKES Dana Bigham [Daniel E. Canfield, Jr.]

A bi-monthly (January- December) survey of microcystin in 187 Florida lakes was completed in 2006. Average mean microcystin concentrations (µg/L) ranged from non-detectable to 12 µg/L, with 29 % of the lakes containing detectable microcystin (≥ 0.10 µg/L). Only 8 % of the lakes had average microcystin concentrations above the World Health Organization’s (WHO) drinking water standard of 1.0 µg/. None of the lakes had average microcystin concentrations above WHO’s recreational standard of 20 µg/L. At any time throughout the year, microcystin concentrations were measured at levels above 1.0 µg/L, but microcystin concentrations significantly increased starting in May/June with the highest concentrations occurring during September through December. As expected, microcystin concentrations were found to increase with cyanobacterial biomass and lake trophic status. A monthly study of six hypereutrophic lakes (Harris Chain of Lakes) completed in 2006 found 57 % of the samples contained detectable microcystin and 40% of the samples (216 water samples) were above 1.0 µg/L. None of the samples exceeded the recreational standard. Consequently, microcystin does not seem to pose a great threat to Floridians at this time as lakes are typically not used for drinking water and the recreational standard is seldom exceeded.

FISH COMMUNITY COMPOSITION IN TUSSOCK-FORMING AQUATIC MACROPHYTES AT TWO SOUTH FLORIDA LAKES Aaron J. Bunch [Micheal S. Allen]

Stabilization of lake levels in Florida lakes can exacerbate the formation of dense vegetation mats (i.e., tussocks) in littoral zones. Anoxia and hyperthermia associated with tussocks can provide quality habitat for small-bodied fishes utilizing the oxygen-rich surface layer, but reduce habitat for species that depend on oxygen within the water column. We sampled tussock-forming macrophyte species (i.e., cattail Typha spp., pickerelweed Pontedaria cordata, and torpedograss Panicum repens) at varying coverage levels (i.e., percent area coverage; 50-64%, 65-79%, and 80-95%) using enclosure samplers (i.e., block net, Wegener ring, and throw trap) dosed with rotenone at Lakes Istokpoga (2006) and Kissimmee (2007). Fish densities (number/m2) shifted with macrophyte types for various fish groups. For example, stress-tolerant fish, comprised mostly of poeciliids and cyprinodontids, were found at higher densities in torpedograss than other macrophytes. Conversely, stress-moderate fish were most abundant in cattail and had the lowest density in torpedograss. Aquatic macrophyte structural complexity, which affects prey abundance and predator avoidance likely drive differences in fish densities in this study. It is important to evaluate differences in fish densities between macrophyte species and coverage levels in order to make informed management decisions.

The Importance of Floodplain Connectivity to Fish Populations in the Apalachicola River, Florida: Insights from Home Ranges and Habitat Use Towns Burgess [William E. Pine III]

Lotic fishes are widely believed to use aquatic floodplain systems as spawning and rearing habitats. The perception that floodplain habitats are important for fish recruitment has led to river restoration projects that focus on restoring altered rivers to natural flow patterns, including seasonal inundation of floodplains. Few studies have documented the home ranges of lotic fishes to assess the use of floodplain habitats, and fewer studies have linked the spatial and temporal uses of floodplain habitats with spawning events. I used telemetered fishes from five species to examine movement patterns in the mainstem of the Apalachicola River, FL and two tributary floodplain habitats over two years. My preliminary findings suggest that floodplain or mainstem habitat use was associated with the timing of flow events. By conducting kernel home range analysis, I also found that individual fish of some species display resident or migratory habitat use behaviors. The results from this study have management implications pertaining to the establishment of an appropriate flow regime for this river system and to direct future habitat restoration projects that may be beneficial to fish populations related to species home range, timing of spawning, and spawning habitat utilization.

IS A PLANT A PLANT? FISH/HABITAT RELATIONSHIPS IN FLORIDA SPRING-FED COASTAL RIVERS
Edward V. Camp [William E. Pine III/ Thomas K. Frazer]

Florida’s spring-fed coastal rivers have been identified as areas of high conservation importance in the Florida Comprehensive Wildlife Strategy. The aquatic vegetative community of two rivers, Chassahowitzka and Homossassa, has changed dramatically over the past 50 years, potentially altering the systems’ biotic community. I propose to study the species composition, density, and size structure of the small bodied fishes and macroinvertebrate assemblages among different aquatic vegetation types. Primary focus will be on comparisons between rooted macrophytes (ex. Vallisneria americana) and filamentous algae (ex. Cladophora sp.). Preliminary results indicate that species composition is similar but that densities vary drastically between these two types of structure. In general, filamentous algae contain greater densities of small fish and invertebrates than do rooted macrophytes. However all plant types exhibit high seasonal variability in densities of small fish and invertebrates. I plan to determine the mechanisms responsible for these observed differences by examining growth and mortality patterns of representative fish and invertebrate species. These findings will be used to investigate the role of habitat specific population dynamics in ecosystems which are perceived to have changed.

FISHERIES, MIGRATORY MOVEMENTS, AND REPRODUCTION OF BLUE AND SHORTFIN MAKO SHARKS IN THE SOUTHWEST ATLANTIC OCEAN.
Felipe Carvalho [Debra J. Murie]

Although pelagic sharks are caught with a variety of fishing gears in the Atlantic Ocean, pelagic longline fisheries targeting tunas and swordfish account for the majority of shark catches. In light of increased fishing pressure, enlightened international management is required for these highly migratory shark species. Such management is hindered by limited species-specific knowledge about the biology and fishery parameters of key pelagic species. We propose to study the two shark species most often caught by the Brazilian longline fleet in the southwest Atlantic Ocean: the blue shark (Prionace glauca) and the shortfin mako (Isurus oxyrinchus). We will analyze the influence of the operational (e.g. fishing strategy) and environmental (e.g. sea surface temperature) factors in the catch rates of blue and shortfin mako sharks to identify the spatial distribution of adult versus juvenile catch rates. Migratory movements of these far-ranging sharks will be studied using PSAT tags employing satellite technology. Although blue shark reproductive biology is relatively well known, we will fill the void in knowledge of the reproductive biology of shortfin mako. Information on the catch rates, movements, and reproductive biology will allow an integrated analysis in future stock assessments of blue and shortfin mako sharks.

Evaluation of the effects of feeding the calanoid copepod, Pseudodiaptomus pelagicus, to larval marine finfish species. Eric J. Cassiano [Cortney Ohs/Denise Petty]

Historically one of the major bottlenecks to marine fish production has been low survival during the larval phase. Rotifers (Brachionus spp.) and Artemia spp., the traditional live feeds during this phase, have proven to be nutritionally and mechanically unsuitable for many species. The lack of success through the hatchery phase has hindered the commercial production of many finfish species. Recently, the use of copepods as a primary or supplemental live feed has been evaluated with many species and shown to greatly increase growth, survival, and resistance to stress. In this study, I will examine the effects of feeding live calanoid copepods, Pseudodiaptomus pelagicus, to larval marine fish species. Through a series of experimental trials I will define the best feeding regime by evaluating treatment objectives that include how long to feed copepods, and the density and stage of copepods to feed during periods of the larval cycle.

Department of Fisheries and Aquatic Sciences, 7922 NW 71st St., Gainesville, FL 32653
UF PO: 110600 Phone: 352/392-9617 Fax: 352/392-3672 (SUNCOM 622-3672)

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