William F. Loftus Jerome Lorenz, 2005, Quantitative Sampling of Freshwater Fish Species within the Big Cypress National Preserve.Online Links:
Quinn, J. F., Jr.; Bogan, A. E.; Coan, E. V.; Hochberg, F. G.; Lyons, W. G.; Mikkelsen, P. M.; Neves, R. J.; Roper, C. F. E.; Rosenberg, G.; Roth, B.; Scheltema, A.; Thompson, F. G.; Vecchione, M.; Williams, J. D.
The diversity of habitat types in Big Cypress presents considerable challenges to the development of a comprehensive sampling regime, as the effectiveness of any given methodology varies between habitats. To compensate for this, numerous techniques were employed during this study. A variety of fish traps have been used extensively, as well as electrofishing gear, gill nets, cast nets, dip nets, and angling.
The location of each sampling site was recorded as universal transverse mercator (UTM) coordinates using a Garmin Etrex Vista GPS.
Project personnel collected and curated representative vouchers for all captured species whenever practical. Specimens too large to effectively preserve have been documented photographically using a digital camera. Vouchers have been collected independently for each habitat type sampled. Additionally, to ensure complete spatial coverage of the preserve, vouchers of each species have been collected from the north, central, and southern regions of Big Cypress. Information regarding each voucher was entered into the project Access database, and each was assigned a unique identifier to link with related sampling information. Voucher collection is an ongoing process and will continue for the duration of the study. Upon completion of this project, vouchers will be transferred to an NPS-identified repository.
Personnel from The National Audubon Society are collaborators in this project.
305 242-7835 (voice)
305 242-7836 (FAX)
bill_loftus@usgs.gov
The goal of this project in 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). To detect changes in natural and artificial habitats resulting from CERP restoration programs, baseline data on constituent aquatic communities and their ecology are needed before and after restoration actions. Fishes and aquatic invertebrates serve as indicators of the health of these wetlands. These organisms are also important because they are major prey for many of the characteristic South Florida predatory species, especially alligators and wading birds. This project will establish a long-term, quantitative monitoring program for prey-base aquatic organisms and is intended to detect changes in aquatic-animal populations resulting from CERP hydrologic alterations.
A variety of fish traps were used extensively as well as electrofishing gear, gill nets, cast nets, dip nets, and angling.
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.
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.
Specific sampling locations will be selected based on consultations with BICY hydrology staff and will be identified in the FY03 annual report (due September 30). Accessibility, and potential accuracy and precision of sampling gear, will be taken into account when selecting study sites. In general, locations for monitoring will be selected based on the potential to gather data for CERP projects that will affect hydrology. We anticipate that the most conspicuous effects will occur along the boarders of the Preserve. In particular, the decompartmentalization of WCA3 Project will alter freshwater flows along the eastern and southern peripheries. The proximal impact of the project will be along the eastern boundary of the Preserve, but the effects will also be transmitted downstream to the ecotonal areas between the freshwater and estuarine areas of the Preserve. Those regions will receive the most sampling attention. However, the western and northern boundaries may also be affected by CERP projects. In particular, the western Preserve may be affected by restoration efforts in the Southern Golden Glades Estates region and the Preserve. Although these effects may not be as pronounced as the eastern and southern areas, there is a possibility for hydrologic changes. Furthermore, it is important to have reference sites as part of a longterm sampling program. Low-impact areas of the Preserve will serve as control sites within our natural experiment so that the magnitude of changes in the high-impact areas may be measured using a BACI design (Before-After-Control-Impact comparisons). Sampling locations in the interior and along the western periphery should be ideal candidates for low-impact sampling sites.
Similar suites of aquatic habitats within these sectors will be routinely sampled. Our preliminary results suggest that cypress sloughs, freshwater prairies and marshes, and ecotonal swamps and marshes may be ideal for monitoring sites. Sampling within these habitat types will be stratified between ephemeral wetlands and deep-water, dry season refugia for aquatic organisms. For example, alligator holes or ditches adjacent to wetlands will be routinely sampled to quantify the seasonal movements of fishes along a depth gradient. The concentration of prey species into these refugia is particularly important to understanding wading-bird foraging patterns within the Big Cypress region.
The habitat being sampled will determine the sampling protocols. We will use the sampling protocol established in the cooperative program for the Everglades, to the extent possible to allow comparability of data (Trexler et al. 2002). This will allow for linkages between the data collection in the Big Cypress Swamp to adjacent regions within the Greater Everglades. The goal would be to produce a system-wide tracking of aquatic animal communities, and will utilize the different habitat conditions in the regional compartments to assess animal responses. However, it must be recognized that habitats within the Preserve are more diverse than in the Everglades and will require that other methods be used in unique habitats. The findings of the first-year pilot study allow us to suggest the following sampling designs for target habitats. However, until monitoring sites are established it must be recognized that our approach must be somewhat plastic so as to adapt to unforeseen inherent idiosyncrasies associated with any sampling site.
In shallow marsh habitats, the throw trap and drift-fence/minnow-trap arrays (Loftus et al. 2002) used in EVER will be used to collect fishes and invertebrates. In forested areas, complex root and stem systems preclude the use of throw traps, so a modified drop trap method will be substituted for throw trapping, however, the drift-fence arrays will still be useful in these areas. In deep strands, alligator holes, and ditches, we plan to use a boat-mounted electrofisher to sample larger species (Nelson and Loftus 1996). 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. We will purchase data-logging water-quality units to record seasonal physico-chemical characteristics of the habitats, such as dissolved oxygen, pH, specific conductance, and temperature. During the dry season, it will be necessary to reach sample sites by hiring or borrowing a swamp buggy and/or helicopter, or by ATV’s. In wet periods, the USGS airboat and a van will be used for transport.
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. The number of monitoring sites established will be ambitious and will cover all suitable habitat types along the Preserve periphery as described above. However, 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 three years to sample across a range of climatic conditions.
Person who carried out this activity:
305 242-7835 (voice)
305 242-7836 (FAX)
bill_loftus@usgs.gov
Loftus, William F., 2000, Inventory of the fishes in Everglades National Park: Florida Scientist v. 63, n.1, Florida Academy of Sciences, Orlando, FL.
Lorenz, J. J. McIvor, C. C.; Powell , G. , 1997, Drop net for quantatatively sampling fishes over wetland surfaces in the dwarf mangrove of the Southern Everglades: Wetlands v. 17, n. 3, Society of Wetlands Scientists, McLean, VA.
Duever, M. J. Carlson, J. E.; Meeder, J. , 1979, Resource inventory and analysis of the Big Cypress National Preserve: Center for Wetlands, UF-Gainesville and National Audabon Society, Naples, FL.
Loftus, W. F. Eklund, A. M., 1994, Long-term dynamics of an Everglades fish community: St. Lucie Press, Delray Beach, FL.
S. Davis and J. C. Ogden, editors
Trexler, J. C. Loftus, W. F., 2001, Analysis of relationships of Everglades fish with hydrology using long-term databases from Everglades National Park: Florida International University, Miami, FL.
Trexler, J. C. Loftus, W. F.; Jordan, F.; , 2001, Ecological scale and its implications for freshwater fishes in the Florida Everglades: CRC Press, Boca Raton, FL.
J. W. Porter and K. G. Porter, editors
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freshwater fish data from Big CypressNnational Preserve
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