73 not a grand geopolitical reason for the introduction of this species, it has still had a massive impact on the ecology of the Fox River and shows how individual actions can create change in ecosystems. The Rusty Crayfish is particularly dangerous for ecosystems because of its ability to outcompete and cross breed with other crayfish species. The Rusty Crayfish is more aggressive when feeding and can force other crayfish and crustaceans to abandon their ‘homes’ in search of more food.18 Additionally, the Rusty Crayfish lays hundreds of eggs at a time and frequently feeds on the eggs of other fish, creating an overpopulation under population problem.19 This problem is exacerbated by crossbreeding between the Rusty Crayfish and native crayfish, creating a hybrid population in smaller bodies of water like the Fox River can completely overtake the native populations, leading to further degradation of the ecosystems and making them much harder to contain.20 Similarly, the Round Goby can breed up to six times in a single summer and its aggressive nature has led to food scarcity problems for native species, however its role in the ecosystem is much less straightforward.21 One of the main food sources for Round Goby are Zebra Mussels, which grow in overabundance in the Fox River. By eating the Zebra Mussels, the Goby are creating a positive impact on the ecosystem. Some ecologists argue that efforts to control the population of the Goby should be carefully monitored to ensure that a certain level remains in the waterways to 18 Julian D. Olden, M. Jake Vander Zanden, and Pieter T. Johnson, “Assessing Ecosystem Vulnerability to Invasive Rusty Crayfish (Orconectes Rusticus),” Ecological Applications 21, no. 7 (October 2011): pp. 2587-2599, https://doi.org/10.1890/10-2051.1, 2588. 19 Ibid. 20 Tracy E. Arcella et al., “The Role of Hybridization in a Species Invasion and Extirpation of Resident Fauna: Hybrid Vigor and Breakdown in the Rusty Crayfish, Orconectes Rusticus,” Journal of Crustacean Biology 34, no. 2 (January 2014): pp. 157-164, https://doi.org/10.1163/1937240x-00002204. 21 A.-B. Florin et al., “Local Conditions Affecting Current and Potential Distribution of the Invasive Round Goby – Species Distribution Modelling with Spatial Constraints,” Estuarine, Coastal and Shelf Science 207 (2018): pp. 359-367, https://doi.org/10.1016/j.ecss.2017.10.005.
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