To assess fish use of native (e.g., cattails, Typha latifolia) and invasive (Phragmites australis) macrophytes in the Old Woman Creek (OWC) coastal wetland. This assessment will consider both species composition and abundance, and will focus on sportfish forage species (e.g., Lepomis spp., gizzard shad).
To compare fish use of Phragmites in sprayed (with herbicide) and unsprayed areas of the estuary.

Old Woman Creek plays an important role in the functioning of the Lake Erie ecosystem. This shallow, 'freshwater estuary' provides habitat and nursery grounds for a variety of fish species, including many that are of tremendous importance to the forage base for Lake Erie sportfish. Over the past several decades, Phragmites australis has rapidly invaded OWC (and other Great Lakes coastal marshes), and the influence of this invasion on the fish species that depend on OWC resources for spawning and nursery habitat is largely unknown. Fish may use macrophyte beds for spawning, foraging, and as a refuge from predation (among other reasons), and thus the potential negative implications for the invasion of Phragmites include reductions both in foraging ability and productivity (Caffrey 1996; Warren et al. 2001). Previous investigations in coastal marshes have indeed suggested that Phragmites invasions can have a significant impact on ecosystem composition and function. For example, Phragmites invasion in a coastal Connecticut marsh caused a significant decline in the diversity of bird and angiosperm tree species (see citations in Warren et al. 2001). Investigations into the influence of Phragmites on fish populations and communities in coastal habitats have produced variable results (Weinstein and Balletto 1999; Able et al. 2001; Warren et al. 2001). Despite relatively good data on faunal responses to Phragmites invasions in coastal marshes, data on freshwater systems are scarce. I will examine the influence of Phragmites on fish diversity and abundance by comparing fish use of Phragmites and the native macrophyte Typha latifolia.

Because of the potential concern associated with Phragmites invasion and dominance of OWC, it is important to assess the influence of Phragmites control efforts on fish habitat. Glypro®, a glyphosate herbicide, will be applied to Phragmites stands in early summer 2003. This herbicide has been shown to be effective at removing monocotyledonous aquatic plants, and the influence of a single application may be fairly protracted (Caffrey 1996; Warren et al. 2001). Because this application will occur during peak spawning and larval periods for many species in OWC, it will be important to assess the influence of this application on fish habitat. Although the toxicity of Glypro® to aquatic organisms is apparently low (see citations in Caffrey 1996), the habitat alterations could be quite dramatic, and information about fish abundance and composition post-application will be useful in the assessment of fish production for both OWC and the Lake Erie ecosystem. A second objective of this investigation, therefore, is to examine the influence of Glypro® treatment and any associated decrease in Phragmites density on fish abundance and distribution in OWC.

Although the primary objectives of this investigation are to examine fish use of native and invasive macrophytes in OWC, the implications are somewhat more broad. Because OWC is an important nursery area and sanctuary for fish in the Lake Erie ecosystem, the impacts of a Phragmites invasion on OWC have ramifications for the entire lake community. In particular, forage species may be affected by this Phragmites invasion, which could influence the productive walleye (Stizostedion vitreum) and yellow perch (Perca flavescens) fisheries in Lake Erie. Results of this investigation should provide a foundation for future investigations into the effects of invasive plant species and water level fluctuations in OWC and their impact on forage fish and sportfish species in Lake Erie.

Larval and juvenile fish will be collected during summer of 2003 in stands of Phragmites and Typha. Collection methods will include light traps, trap nets, and minnow traps, and replicate samples will be taken in stands of both plant types. Samples will be taken in Phragmites beds in areas that are sprayed with Glypro® (the glyphosate herbicide), and in areas that remain unsprayed. Density and species compositions of fish will be determined from the samples, and comparisons will be made both between plant types, and within Phragmites between sprayed and unsprayed areas. Identification and enumeration of fish will take place during the fall and winter of 2003-2004. Results of this investigation will provide data upon which to build a larger investigation that considers the influence of changing water levels in Lake Erie (and, consequently, in OWC) and the influence of these changes on fish, invertebrates, and their interactions.

Sampling was completed in September. A total of 4 sampling trips were made during July - September. The limited water availability prevented additional sampling, i.e., water levels were too low to collect fish until late July and after mid-September. The water level at the mouth of the creek (connection to Lake Erie) has a tremendous influence on water levels within the estuary; when the mouth is closed, water levels can rise and fish collection is possible in the plant beds. When the mouth opens, however, water level drops and levels remain insufficient for fish collection within the macrophytes. Because spraying of the herbicide occurred in early July, sample collection occurred at a time appropriate to address the objectives.

The most successful sampling gear, by far, was the minnow trap. Throw trap collections were limited and light traps caught very few fish. Interestingly, the light traps were successful in capturing a significant number of large and highly mobile invertebrates. The most abundant fish species collected was the green sunfish (Lepomis cyanellus n=204), followed by bluegill (Lepomis macrochirus n=40), carp (Cyprinus carpio n=39), white sucker (Catostomus commersoni n=4), spottail shiner (Notropis hudsonius n=2), johnny darter (Etheostoma nigrum n=1), and yellow bullhead (Ameiurus natalis n=1). Most fish were caught on the 8/2/2003 sampling date (87 total, 4 species), followed by the 7/19/2003 date (38 fish, 4 species), the 9/14/2003 date (37 fish, 3 species), and the 8/20 date (30 fish, 3 species). Green sunfish appeared to move into the estuary in early August and dominated the fish collections after that period.

Plant type had no influence on the number, species, or size of fish collected. Combining all dates, there was no difference (F = 0.21, P = 0.81) in mean number of individuals collected in the unsprayed Phragmites (UP; mean ± 1S.E.; 18 ± 7.3), the sprayed Phragmites (SP; 27 ± 17), and the Typha (T; 29 ± 13). Similarly, there was no difference (F = 0.27, P = 0.77) in mean number of species collected in UP, SP, and T (across the sampling dates, the mean was 2 species for each plant type). Finally, mean length of collected fish did not differ (F = 0.09, P = 0.91) among UP (38.6 ± 5.77 mm, total length), SP (40.1 ± 4.37 mm, total length), and T (41.6 ± 4.42 mm total length). These results suggest that fish use of the invasive Phragmites is similar to that of the native Typha. Further, it appears that the spaying of Phragmites with Glypro™ herbicide does not have an adverse affect on fish diversity or abundance.

Although this small investigation can not provide definitive answers to these important questions, this investigation should provide a foundation upon which future studies can build. We will continue to synthesize these data with invertebrate data collected by Dr. Joe Holomuzki and Amy Kulesza. Additional collections in 2004 will augment this data set and a manuscript containing all data will be prepared in 2004-2005 to present a community/ecosystem-level perspective on the Phragmites invasion into the OWC estuary.