Size matters? Species‐ and size‐specific fish predation on recently established invasive quagga mussels Dreissena rostriformis bugensis Andrusov 1897 in a large, deep oligotrophic lake

Abstract

Since its first appearance in Lake Constance in 2016 the invasive quagga mussel Dreissena rostriformis bugensis has come to dominate the mussel community and now occurs in hyperabundant densities over the whole lake bottom. A lake‐wide field study was conducted between 2019 and 2020 to obtain a systematic insight into the importance of this novel source of potential prey for the native fish community. In total 664 fish of 20 different species were caught and their digestive tracts were analysed. Meanwhile, quagga mussels were sampled to assess their calorific energy value by size and season. Regressions of septum length on maximum valve length were used to evaluate size‐specific mussel consumption by the three dominant quagga‐eating fish species. The study shows that nearly all benthivorous fish are able to forage efficiently on quaggas. However, in the case of one keystone species with very high commercial interest, the benthic whitefish Coregonus spp., quagga consumption is more limited as only individuals larger than 35 cm consumed quaggas in relevant amounts. The energy content of quagga mussels is positively size dependent with seasonal effect and elevated values during summer for medium‐ and large‐sized mussels. Even at its peak, the calorific value of quaggas by weight is much lower than that of endemic aquatic invertebrates, while single mass is high. Future implications for fish stocks, food web integrity and possible fishery management options are discussed.

Supporting Evidence for the “Ten-Year Fishing Ban”: Different Modes of Fishing and Pollution Induce a Fish Diversity Decline between the Pearl River and Its Estuary

“…To compare the fish biodiversity, the method of stable isotopes of carbon and nitrogen was applied to understand the biogeochemical processes associated with fish population dynamics and habitat degradation processes. , The stoichiometric variations of isotopic stable carbon and nitrogen can reflect the nutrient cycling rates and energy flows levels, and thus manifest the variations in the structure and function of aquatic ecosystems. − During the process of element transfer and energy flow, both intra- and inter-species changes in the keystone species of the fish community can irreversibly lead to ecosystem stability and fishery resource sustainability collapse, − thereby disrupting trophic levels of aquatic organism regulation. ,− Furthermore, a reconstruction of the food web can display fish interactions clearly by using carbon and nitrogen isotope technology and further provides benefits for evaluating the impacts of human activities on fish biodiversity alterations. , …”

An abundant future for quagga mussels in deep European lakes

“…Food webs are further altered by reducing the resource availability for planktivorous organisms including larval fish with cascading effects throughout the food web (Cunningham and Dunlop 2023). But, quagga mussels themselves can be an important albeit lower-quality food source for some fish (Pothoven and Madenjian 2008, Baer et al 2022a, 2022b, Karatayev and Burlakova 2022a, 2022b. For instance, in Lake Constance, benthic whitefish (Coregonus macrophthalmus), roach (Rutilus rutilus) and tench (Tinca tinca) are all capable of high levels of quagga consumption (Baer et al 2022a(Baer et al , 2022b.…”

“…Quaggas may exacerbate or mitigate the effects of three-spined sticklebacks on pelagic fisheries, but at the moment, such anticipated effects are speculative. Interactions between quagga and other neobiota may increase fishery productivity (Madenjian et al 2015, Karatayev and Burlakova 2022a, 2022b. For instance, round gobies (Neogobius melanostomus) consume quagga mussels (Wilson et al 2006, Kornis et al 2012 and are in turn an important food source for commercially and recreationally valuable fish species including lake trout, burbot, yellow perch, smallmouth bass, lake sturgeon, and walleye (Karatayev and Burlakova 2022a).…”

“…But, quagga mussels themselves can be an important albeit lower-quality food source for some fish (Pothoven and Madenjian 2008, Baer et al 2022a, 2022b, Karatayev and Burlakova 2022a, 2022b. For instance, in Lake Constance, benthic whitefish (Coregonus macrophthalmus), roach (Rutilus rutilus) and tench (Tinca tinca) are all capable of high levels of quagga consumption (Baer et al 2022a(Baer et al , 2022b. Waterfowl populations may also feed heavily on quaggas that grow in shallow areas of lakes (Molloy et al 1997, Petrie andKnapton 1999).…”