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Project Work Plan

Greater Everglades Science Program: Place-Based Studies

Project Work Plan FY 2003


Project Title: Influence of Hydrology on Life-History Parameters of Common Freshwater Fishes from Southern Florida
Project start date: October, 1999 Project end date: December 2004
Project Funding: PBS
Principal Investigator: William F. Loftus
Email address: bill_loftus@usgs.gov
Phone: 305-242-7835 Fax: 305-242-7836
Mail address: USGS, Everglades National Park Field Station, 40001 State Road 9336, Homestead, FL 33034

Project Summary: In the effort to restore the Everglades, fishes have been recognized as good indicators of restoration success. Our long-term fish database in the Everglades has been used to document the effects of water management in southern Florida (Loftus et al. 1990, Loftus et al. 1992, Loftus and Eklund 1994, Trexler and Loftus 2001, and Trexler et al. 2001) and was used in the ATLSS fish simulation model (DeAngelis et al. 1997) developed to evaluate future restoration scenarios and estimate historical fish communities. However, much life-history data in the model had to be estimated because no data were available. Similarly, no empirical data fro fish densities or life histories were available from the Big Cypress.

In this program, comprised of two study tasks, we intend to remedy these data gaps through a combination of new studies and through the analysis of previously and newly collected specimens to study recruitment, age, and growth in representative species of large- and small-bodied fishes. These studies will describe community composition and function of these most numerous vertebrates in the poorly studied Big Cypress ecosystem, and will allow us to test hypotheses about the role of hydropattern in the life-histories of the fishes. In the process, the analyses will result in improvements to the ATLSS fish model, and help to explain patterns of community change observed in the long-term fish database, giving us more confidence in the tools used to restore this internationally recognized ecosystem.

Project Objectives and Strategy: In the Everglades and Big Cypress wetlands, natural environmental conditions regularly vary on seasonal, annual, or multi-annual time-scales, to which the wetland fishes respond by shifts in relative abundance and standing stocks (Roman et al. 1994; Trexler et al. 1996). Human activities have affected the natural variability by altering the seasonality and areal extent of flooding in the wetlands, by drainage, or by over-inundation (Gunderson and Loftus 1993). The human-induced changes have resulted in loss of diversity, changes in composition and abundance, and possible alterations in energy-flow pathways (Loftus et al. 1990). Although these changes in population size and community structure are ultimately related to marsh hydrology, proximate factors that explain some of this variation probably include inherent reproductive adaptations to ambient conditions, such as the seasonality of recruitment, the age/size at first reproduction, growth rates, and other important life-history parameters.

Fishes are essential to the successful functioning of wetlands in southern Florida through their roles as prey and predators. Any changes that reduce the population sizes, community composition, or availability of aquatic animals will affect all facets of the ecology of these wetlands. Therefore, the multi-agency groups responsible for guiding Everglades restoration have recognized fishes as a key indicator group by which to measure restoration success. Communities of small-bodied fishes have been studied in EVER since 1977 by using throw traps in spikerush marshes at many Everglades sites (Loftus and Eklund 1994, Trexler et al. 1996, and Trexler et al. 2001). The data analyses allow evaluation of seasonal and long-term dynamics, shifts in relative abundance and size-structure, and produce correlations of fish abundance to water depth, hydroperiod, and plant community structure.

Despite an increasing emphasis on fish studies, important gaps in baseline knowledge remain. Life-history parameters of important fish species remain to be studied at sites along hydroperiod gradients and across ecosystem boundaries. Some life-history characteristics are known to be rather plastic in response to the environment. We intend to study the effect of hydroperiod on recruitment, size/age structure, growth, and fecundity, which, in turn, determine fish population dynamics. At present, data on fish reproduction, age and growth, and other life-history characteristics are confined to a few species from a limited area of long-hydroperiod marsh in central Shark River Slough in Everglades National Park. As we continue the analysis and synthesis of data from the long-term fish collections, life-history information will help explain patterns of fluctuations in the time series. Accurate life-history data are also very important in building credible simulation models like ATLSS. Without empirical life-history data from a range of environments, the model will be simplistic and inadequate.

Similarly, there exist almost no empirical data for the composition and dynamics of fish communities in the Big Cypress ecosystem. That ecosystem retains much of its historical character as it has been less altered hydrologically than much of the Everglades system. However it has been logged and has had water flows diverted by canal and levee systems and by off-road- vehicle use. Important ecosystem characteristics differ between the Everglades and Big Cypress systems, making it imperative to study its communities as part of the overall south Florida restoration process.

General Project Hypothesis: Hydroperiods of wetlands affect the community dynamics and structure, growth patterns, and reproductive output of south Florida fishes. We have demonstrated that hydroperiod affects the density of fish populations in the Everglades and we postulate that the same relationship will hold true for the Big Cypress communities. We are also testing the idea that life-history effects will be manifested by differences in the size-to-age relationship, life expectancy, and fecundity of female fishes in long- versus short-hydroperiod sites.

Our work plan includes gathering data to test for these hypothesized differences in community parameters and in population life histories. We are also working with five species of large-bodied fishes collected at a southern Everglades canal site that provides access to the marsh in the wet season and refuge from drying the rest of the year. Our data will demonstrate this seasonal use of canals in the Everglades system and the relation of reproductive phenology and growth to that seasonal pattern.

Potential Impacts and Major Products: We are using a system of empirical data collection and simulation modeling to apply information on fish-community patterns in guiding the restoration process. We are describing the functional responses of present-day community density and standing stock to environmental conditions across the landscape. The empirical data also help to build simulation models with which to estimate fish-community parameters under modeled pre-management conditions, allowing us to establish restoration targets. By applying the fish models to restoration alternatives and predicting fish-community responses, we can choose the alternatives that result in biotic characteristics that approximate historical conditions. The iterative process of evaluating and testing the fish-community simulation model in ATLSS also helps identify important data gaps to guide future research. One of the most obvious gaps is the absence of good life-history data, critical to model performance, for most of the fishes. The benefits to restoration would arise by having more confidence in improved tools, like the ATLSS models, that are used to evaluate alternatives for ecological effects of CERP, the C-111 Project, and Modified Water Deliveries Plan to Shark Slough. A number of Performance Measures and Success Criteria have been developed to assess restoration actions. These Measures are referable to the Conceptual Models developed for the restoration to illustrate the stressors and response variables in each major habitat that would be affected by restoration actions.

Sampling in BICY will provide the first spatially extensive baseline ecological data for the aquatic fauna there. Sampling will occur at fixed, long-term sites before restoration begins, so that monitoring of faunal changes at those sites can continue through the restoration process. Hopefully, after this project ends, the study sites will be incorporated into a long-term monitoring program for BICY by the NPS Preserve staff during the entire restoration process.

The application of the life-history data to modeling and to interpretation of the data time-series, these data represent new information about the adaptations of many of these species in wetland habitats that form the southern extent of their geographic ranges. These also represent the first life-history data for some of the most abundant introduced species in Florida, and may identify vulnerable life stages for controlling these species. The publications resulting from this work will be scientifically significant for those reasons.

Total Time Frame:

Time Frame FY03 FY04 FY05 FY06
Task 1
Fish Inventory Design X
Pilot Study for Long-term collections
  Sampling design X
  Sampling methods X
Field Collections
  Marshes/swamps X X X
  Ponds/strands X X X
Lab Processing
  Fishes X X X
Annual reports X X X
Final Reports X X
Task 2
Field Collections X
Lab Processing X
Data Analysis X X
Report Writing X X

Dr. Joel Trexler
Dept. of Biological Sciences
Florida International University
Miami, FL 33199
305-348-1986 (Fax)

Dr. Jerry Lorenz, Director
Audubon Society's Tavernier Science Center
115 Indian Mound Trail
Tavernier, FL 33070
(305) 852-5092
(305) 852-8012 fax

Clients: National Park Service


Title of Task 1: " Inventory of Freshwater Fish Species within the Big Cypress National Preserve, with emphasis on methods testing to design a long-term aquatic biota sampling program"

Task Funding: PBS and matched NPS I&M funding to National Audubon Society
Task Leaders: Dr. William F. Loftus and Dr. Jerome Lorenz
Phone: 305-242-7835 Fax: 305-242-7836 and Phone: 305-852-5092 Fax: 305-852-8012
Task Status (proposed or active): PBS - proposed; National Audubon - active.
Task priority:

Time Frame for Task 1:

Task 1 Time Frame FY03 FY04 FY05 FY06
Inventory Design X
Pilot Studies
  Sampling design X
  Sampling methods X
Field Collections
  Marshes/swamps X X X
  Ponds/strands X X X
Lab Processing
  Fishes X X X
Report Writing
  Annual reports X X X
  Final Inventory Report X
  Final Sampling Report X

Task Personnel: Loftus, Lorenz, and two junior-level biologists

Task Summary and Objectives: The goal of this project in FY03 is to inventory the freshwater fish in the Big Cypress National Preserve, and simultaneously test sampling methods and designs for a long-term aquatic biota research program for the Preserve. A major ecosystem of the South Florida area, the Big Cypress Swamp, is poorly understood in biological terms. The Department of Interior is responsible for management of most of this system, which is part of the Everglades Restoration Program (CERP). We propose to describe large and small fish and macro-invertebrate ecology in representative habitats of the Swamp in a multiyear study to provide basic inventory information on Swamp communities and ecological data for use in simulation models. The models will be used to plan and evaluate restoration actions during CERP. Presently, inappropriate data from the Everglades are used in the Swamp model.

The Big Cypress Swamp ecosystem covers a major area of southwestern Florida, yet has been poorly studied compared with the Everglades. The Department of Interior is responsible for management of the Big Cypress National Preserve (BICY), which comprises a large area of this system, and several smaller National Wildlife Refuges. Human-induced changes have affected the natural variability of environmental conditions through the construction of canals and levees that can either act to drain or flood wetlands (Gunderson and Loftus 1993). Levees act as barriers to animal movement among habitats, probably preventing mixing of populations and access to refuges. Canals are conduits for movements by animals, serve as artificial refuges for native and introduced large-bodied fishes, and may be sinks for small fishes and invertebrates produced by adjacent wetlands. The Big Cypress Swamp landscape has been affected by all of these anthropogenic activities, yet their effects are unclear because of the lack of study. However there can be little doubt that the standing stocks of aquatic animals and their population sizes have been affected negatively by those activities.

Fishes are essential to the successful functioning of wetlands in southern Florida through their roles as prey and predators. Any changes that reduce the population sizes, community composition, or availability of aquatic animals will affect all facets of the ecology of these wetlands. Communities of small-bodied fishes have been studied in EVER since 1977 by using throw traps in spikerush marshes at many Everglades sites (Loftus and Eklund 1994, Trexler et al. 1996). The data analyses allow evaluation of seasonal and long-term dynamics, shifts in relative abundance and size-structure, and produce correlations of fish abundance to water depth, hydroperiod, and plant community structure.

Several programs to restore lost structure and function to the south Florida landscape are now being planned. To have the ability to detect changes in natural and artificial habitats resulting from these restoration programs, baseline data on the constituent aquatic communities and their ecology are needed before and after the restoration actions. Baseline data collections are also needed to document animal community composition, ecology, and dynamics, because those animals support many of the predatory species, especially alligators and wading birds. Fishes and aquatic invertebrates can serve as indicators of the health of these wetlands. The data collected here will provide important inventory information about the aquatic animals that inhabit the system, and will also examine the relationships of the animals with the hydrological regimes.

This project has several objectives, the foremost of which is to begin a program of aquatic study in a large and relatively neglected ecosystem. Future studies should investigate the differences between aquatic animal communities in the Big Cypress and Everglades systems as a construct around which to test ideas. In this project, the main objectives are:

  • Work with partners from National Audubon Society (NAS) and clients from the National Park Service to inventory the freshwater fishes of the Big Cypress National Preserve (BICY).
  • Document the distribution, composition, and habitat use by native and introduced fishes
  • Perform a pilot study in the first year to design a spatially explicit and temporally varied, quantitative sampling program for aquatic animals in BICY. Implement this study in the second project year. This will complement the existing program in the Everglades ecosystem.

NPS has funded NAS as a CESU-partner to perform an inventory of freshwater fishes of BICY. However, the funding level is barely adequate to meet the inventory needs. We propose to partner with NAS to support a more rigorously scientific fish inventory of BICY that will serve as the basis for a long-term program of research. BICY will be affected by CERP activities and will need baseline data on fish fauna as will as long-term study of community structure and function. Those data will provide the necessary to understand the effects of CERP on park fauna.

The NAS and USGS project leaders will plan and direct the project. USGS will also provide some sampling gear, such as electrofishing equipment, to successfully complete the project.

Duever et al. (1979) identified 10 broadly defined habitat types within BICY based on dominant vegetation type; five of these habitats are considered freshwater: cypress forests, mixed swamp forests, mixed pine and cypress prairies, herbaceous prairies, and deep water sloughs and ponds. A sixth habitat (coastal marshes) is predominantly freshwater but is periodically inundated with marine waters. Although not considered by Duever et al. (1979), canals are also a significant part of the BICY landscape and can be considered as a separate freshwater habitat type. All seven habitats will be sampled in relation to habitat abundance with BICY. Sampling effort will be two-tiered. The first tier will include sites readily accessible via roadways or levees. These sites will be subjected to repeated sampling on a seasonal or quarterly basis, depending on hydrologic variability. The second tier will include more remote areas that cannot be accessed by automobile. These sites will be sampled less frequently. Selection of these sites will be determined based on the abundance of the given habitat type and possibility of access. Sampling of these areas will be done using BICY's helicopter and swamp buggy, and we plan to purchase an all-terrain vehicles, and use USGS airboats. NAS will provide a 4-wheel drive truck for the study. Special effort will be made to sample short hydroperiod wetlands during periods of flooding and to sample sub-habitats with conditions that make them unique or rare within BICY. Fieldwork will consist of a minimum of 9 field weeks or 45 field days.

Traditional fisheries collection techniques will be used throughout BICY to assess the composition of the freshwater ichthyofauna. Examples of collection techniques to be used are passive fish traps (e.g. minnow traps), pull seines, experimental gill nets, throw traps, cast nets, block nets, angling, visual surveys, electrofishing, and rotenone application (within enclosures or in small isolated water bodies). A combination of several of these techniques will used at each sampling location so as to reduce gear bias thereby promoting a more accurate census of the fish community. The habitat type and on-site conditions will determine which techniques will be used. Attention will be paid to sampling effort such that quantitative abundances of species can be made (i.e., catch per unit effort or catch per unit area). This is a particularly important part of the gear-testing phase of the first project year that will allow us to select the most appropriate gear for the long-term sampling study in FY04. Application of the proposed techniques is dependent upon BICY issuing the appropriate permits for such activities.

Potential Design and Methods for sampling study

To collect data on aquatic animal community composition and dynamics in the Big Cypress Swamp, we will use the sampling protocol established in the cooperative program for the Everglades, to the extent possible to allow comparability of data. Linkages between the data collection in the Big Cypress Swamp and adjacent regions should produce system-wide tracking of aquatic animal communities, and will utilize the different habitat conditions in the regional compartments to assess animal responses.

Naturally, the habitat differences in the Big Cypress Swamp will require the use and testing of different methods. To examine seasonal habitat use by the aquatic animals, we intend to include a gradient from shallow marsh/swamp habitats to deeper pool/strand habitats at each sampling location. We anticipate sampling five times per year in February (winter), April (dry season), July (summer), October (wet season), and December (transition between wet and dry). This schedule uses the successful elements from the Everglades program-sampling regime to this study to reduce the amount of method development. In shallow habitats, the throw trap and minnow-trap arrays will be used to collect fishes and invertebrates. In deep strands, we plan to use a boat-mounted electrofisher to sample larger species. Specimens will be preserved and returned to the laboratory for identification and enumeration. The specimens will be saved as vouchers and for processing for life-history data. Large-bodied species will mainly be field-processed and returned alive, except for voucher and life-history samples. Correlative hydrological data will be gathered as discontinuous data from local staff gauges, and as continuous daily data from recording stations. Ancillary habitat data on vegetation cover and local water depths will be taken. During the dry season, it will be necessary to reach sample sites by hiring or borrowing a swamp buggy and/or helicopter, and by purchasing ATV's. In wet periods, a USGS airboat and van will be used for transport.

The pilot study must address questions at two scales: at the local scale of sampling plots in evaluating the best methods for collecting animals. The second level is at the landscape scale, to determine the sampling design. Because the habitats in the Swamp include forested wetlands, there will be an element of sampling method testing in that habitat. The literature contains methodologies developed for other forested wetlands in the southeast US, but these must be evaluated under local conditions. The large size of the Swamp and its diversity of habitats will make stratification of sampling effort necessary to adequately describe the functional responses of the fishes to environmental conditions, especially hydrology and stochastic disturbances. The pilot data will be evaluated with the help of the FCSC statistician before settling on a final design for the project. The project should cover the major habitat types in the ecosystem, but the actual number of sites will depend on the effort needed to sampling them and the resources available. The collection effort should be supported for a minimum of four years to try to sample during a range of climatic conditions.

Planned Outreach: A Fact Sheet to describe the project will be written in the first project year. We plan to make presentations at the Big Cypress National Preserve and at regional scientific meetings. Our Everglades database is being used to develop the fish simulation model used in evaluating restoration scenarios and reconstructing historical communities. There are no such quantitative data for the Big Cypress Swamp ecosystem. That lack of baseline data limits the assessment of future restoration actions in that system. The lack of information also affects the ability to judge whether restoration actions meet Performance Measure Success criteria, in part because there are no baseline data for aquatic communities in this region. The data will improve the fish model, which now inappropriately applies Everglades information to the Big Cypress landscape model. Data specific to this federally managed ecosystem will provide confidence and credibility in the tools used in restoring this region.

Title of Task 2: Life-History Characteristics of Common Everglades Fishes
Task Leader: William F. Loftus

Phone: 305-242-7835
Fax: 305-242-7836

Project co-chief: Leo G. Nico
Region/Division/Team/Section: Eastern region, BRD, FCSC, Non-indigenous Species Branch

Email: leo_nico@usgs.gov

Phone: 352-378-8181

Fax: 352-378-4956

Mail address: 7920 NW 71st St., Gainesville, FL 32653

Task Funding: PBS
Task Status (proposed or active): Active

Task priority:

Time Frame for Task 2:

Task Personnel: Loftus, Nico, and Trexler

Task Summary and Objectives: In the final year of this task, we will complete the laboratory analysis of additional and existing samples to assess the biology of the flagfish (Jordanella floridae) and bluefin killifish (Lucania goodei). The life-histories of the flagfish and bluefin killifish will be characterized from existing samples collected at two sites in Everglades National Park that represent different hydroperiod conditions. The analysis of previously collected samples of other large- and small-bodied species will be completed and the results written for publication Because we were unable to collect adequate samples of yellow bullhead catfish (Ameiurus natalis) from the canal sites, we plan to work with our cooperator, Dr. Trexler, to collect samples from marsh habitats for analysis. Dr. Trexler has an ongoing sampling program in the Everglades marsh during which he can collect the samples we need to finish this study component. He can collect samples five times during the year to provide samples from different seasons.

Age-Size relationship: Small fishes collected the hydroperiod study sites in the Everglades marsh are being analyzed for otolith annular counts. The number of fish examined has been determined by the pilot study and is consistent with standard methods for this kind of work. Maximum life expectancy is being estimated by the estimating the ages of large specimens of the two species from our collections. In the large-fish segment, we are analyzing the results of our work with Florida gar and warmouth sunfish, while completing the work begun with spotted tilapia aging. Statistical analysis of the data has begun now that all data have been collected and error-checked. We have done preliminary work with yellow bullhead aging to determine the best tissue for this purpose and we proceed with this work once we have specimens in hand.

Reproductive Biology. Our estimates of reproductive phenology and fecundity in egg-laying fishes have required the dissection of female fish to determine the number and developmental stage of ova. In addition, we have been recording the weight of female fish and of their ovaries for calculations of reproductive allocation. Female flagfish are batch spawners that produce a brood of eggs in discrete spawning events, while bluefin killifish are fractional spawners that release a small number of eggs on a routine basis. These two different modes of reproduction have posed challenges to life-history description. The time interval between breeding bouts and the relationship between egg counts from preserved females and actual number of eggs laid must be determined for flagfish. For bluefin killifish, we must estimate the daily egg production, and the distribution of female reproductive lifespans. To satisfactorily obtain these parameters for these two fishes, we have reared these fishes in mesocosm tanks and aquaria, and harvested eggs from nests (flagfish) or artificial spawning substrates (bluefin killifish

In the large-fish segment, we will complete analysis of reproduction in Florida gar and other large-bodied species by dissection, gonadal examination, and preparation of a gonadal-somatic index for each species. We have also performed a literature review to determine reproductive parameters from other populations of these species. We will perform reproductive analyses with yellow bullheads once we receive specimens.

Planned Outreach: At the end of the project task, we shall produce manuscripts destined for publication on the reproduction and phenology of large-bodied fishes associated with canals, and the same for the small-bodied marsh fishes. We plan separate publications resulting from this study that will report the age and growth data for the large- and small-bodied fishes in canals and marshes, with relation to habitat seasonality. We will compare our results to the patterns reported for these species in other southeastern US waters, and to patterns identified for fishes that inhabit other seasonal wetlands.

Two FIU graduate students will produce Master's Theses, based on this work, one of which is nearly completed. We will produce an update of our project Fact Sheet. We, and the graduate students, plan to attend meetings of scientific professional societies to present results of the study. We will also participate in relevant local and regional meeting related to Everglades restoration. Team leaders for RESTORE are anticipating these data to refine Performance Measures during the restoration effort. We are working closely with them to make our data and insight s available, even before the final products are ready. We plan to deliver a seminar at Everglades National Park to inform clients of research results and implications. We will also attend meetings of the Greater Everglades Restoration Science Forum.

Literature Cited

Carlson, J. E. and M. J. Duever. 1977. Seasonal fish population fluctuations in a South Florida swamp. Proceedings of the Southeastern Association of Fish and Wildlife Agencies 31:603-611.

DeAngelis, D. L., W. F. Loftus, J. C. Trexler, and R. E. Ulanowicz. 1997. Modeling fish dynamics and effects of stress in a hydrologically pulsed ecosystem. Journal of Aquatic Ecosystem Stress and Recovery 6: 1-13.

Duever, M. J., J. E. Carlson, J. F. Meeder, L. C. Duever, L. H. Gunderson, L. A. Riopelle, T. R. Alexander, R. F. Myers, and D. P. Spangler. 1979. Resource inventory and analysis of the Big Cypress National Preserve. Final Report to the U.S. Dept. of Interior, National Park Service from the Center for Wetlands, University of Florida-Gainesville, and the National Audubon Society, Naples, Florida.

Gunderson, L. H. and W. F. Loftus. 1993. The Everglades. Pp. 199-255 IN W. H. Martin, S. G. Boyce, and A. C. Echternacht (Editors). Biodiversity of the Southeastern United States. John Wiley and Sons, New York.

Loftus, W. F., J. D. Chapman, and R. Conrow. 1990. Hydroperiod effects on Everglades marsh food webs, with relation to marsh restoration efforts, Pages 1-22 IN G. Larson and M. Soukup (Editors). Fisheries and Coastal Wetlands Research. Proceedings of the 1986 Conference on Science in National Parks, US NPS and The George Wright Society. Volume 6.

Loftus, W.F., R.A. Johnson, and G.H. Anderson. 1992. Ecological impacts of the reduction of ground water levels in short-hydroperiod marshes of the Everglades, Pp. 199-207 IN J.A. Stanford and J.J. Simons (Editors). Proceedings of the First International Conference on Ground Water Ecology. American Water Resources Association, Bethesda, Maryland, 420 pp.

Loftus, W. F. and A. M. Eklund. 1994. Long-term dynamics of an Everglades fish community. Chapter 19, pp. 461-483 IN S. Davis and J.C. Ogden (Editors). Everglades: the System and its Restoration. St. Lucie Press, Delray Beach, Florida.

Roman, C. T., N. G. Aumen, J. C. Trexler, R. J. Fennema, W. F. Loftus, and M. A. Soukup. 1994. Hurricane Andrew's impact on freshwater resources. Bioscience 44:247-255.

Trexler, J. C., W. F. Loftus, and O. L. Bass, Jr. 1996. Documenting the effects of Hurricane Andrew on Everglades aquatic communities, Part I. Pages 6-136 IN J. C. Trexler, L. Richardson, and K. Spitze (Editors). Effects of Hurricane Andrew in the structure and function of Everglades aquatic communities. Final contract report CA5280-3-9014 to Everglades National Park.

Trexler, J. C. and W. F. Loftus. 2001. Analysis of relationships of Everglades fish with hydrology using long-term databases from Everglades National Park. Final report to Everglades National Park under FIU Cooperative Agreement CA5280-8-9003. 101 pages.

Trexler, J. C., W. F. Loftus, F. Jordan, J. H. Chick, K. L. Kandl, T. C. McElroy, and O. L. Bass, Jr. 2001. Ecological scale and its implications for freshwater fishes in the Florida Everglades. Pages 153-181 IN J. W. Porter and K. G. Porter (Editors). The Everglades, Florida Bay, and coral reefs of the Florida Keys: an ecosystem sourcebook. CRC Press, Boca Raton, Florida.

Turner, A. M., J. C. Trexler, F. Jordan, S. J. Slack, P. Geddes, J. Chick, and W. F. Loftus. 1999. Targeting ecosystem features for conservation: standing crops in the Florida Everglades. Conservation Biology 13: 898-911.

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