## 4 Discussion
It is unknown if sensitive species have been extirpated from OSM and, if conditions improved after restoration, whether source populations would be geographically close enough to recolonize and reflect the higher richness, or if this is an indication of only partial success of the restoration project. Increased biomass is typically viewed as positive but becomes more complex when large invasive species, such as Common Carp, are present. Biomass ranged between 1.07 g/m\({}^{2}\) at OSM_Pre, 2.32 g/m\({}^{2}\) at the Excellent group, and 2.69 g/m\({}^{2}\) at OSM_Post, but the at Excellent sites, biomass was largely driven by large native species rather than Common Carp. The low biomass in OSM_Pre represents a time when Common Carp were absent but larger native fish had not colonized the wetland. Biomass more than doubled after Common Carp were reintroduced to the wetland. Common Carp accounted for 38% of the biomass but only 2.4% of the abundance and had a negative relationship with fish IBI in Durham Region Coastal Wetlands ([PERSON], unpubl. data). [PERSON] et al. [6] reported Common Carp biomass to be as high as 2600 kg/ha, and [PERSON] et al. [37] found that native species account for less than half of the total biomass, in large part because of the influence of Common Carp, in litterful fish assemblages of three Areas of Concern, including the Bay of Quinte. The boat electrofishing protocol used in DRCWMP typically under-represents Common Carp due to its size, speed, and evasive abilities in shallow coastal wetlands with little vegetation cover, yet it still contributes significantly to biomass calculations in this monitoring. To better understand the impact and peak abundance of Common Carp, multiple sampling techniques to better estimate population size and sampling in multiple seasons would be beneficial [19; 20]. Trophic structure has been documented to play an important role in wetland restoration. Certain species, such as Common Carp, or portions of the trophic structure, such as piscivores, have been found to indirectly influence water clarity and vegetation structure, which is largely consistent with our results [5; 9; 34; 40; 41; 42; 43]. The OCM_Post community had few piscivores when compared to the Excellent group, which may have contributed to the high abundance and low diversity of fish species. In the absence of piscivores, an increased abundance of tolerant species, in this situation largely Common Carp, translates to higher levels of benthivory-depleting filter-feeding zooplankton through consumption [5], excess re-suspension of sediment particles damaging the filter apparatus [44], disturbing dormant stages of zooplankton [5], and increasing concentrations of mineral matter in the water column [45]. Fewer zooplankton, especially larger zooplankton, result in a transition to, or maintenance of, a turbid phytoplankton system as fewer organisms are available to control phytoplankton abundance [6; 9; 46; 41]. Following Common Carp removal at OSM (OSM_Pre), an increase in piscivores was expected but not observed. Given upstream water quality could not be improved through restoration, this may have prevented piscivore abundance increases, which led quickly to reverting back to its previous state when Common Carp regained access to the wetland. This underlies the importance of considering physical, chemical, and biological interactions holistically when completing restoration projects. A reference-condition approach (RCA) was applied given the lack of pre-development baseline data for OSM. The restoration trajectory, as measured by the change in distance to the Excellent group centroid, indicates improving fish community health between 2005 and 2009. The change in distance from 2009 to 2010, when Common Carp regained access, is the largest increase in distance (0.98) from the Excellent group centroid, synonymous with poorer fish community health.