Assessment of dreissenid biodeposits as a potential food resource for invasive Asian carp

Abstract

This is the first attempt to outline the occurrence of selected invasive alien vertebrates in Greece, since up to now, there are no "official" or scientific reports except from sporadic sightings and anecdotal stories. Records on the occurrence of: Lithobates catesbeianus, Trachemys scripta (T. s. elegans and T. s. scripta), Neovison vison, Myocastor coypus, Nyctereutes procyonoides and Ondatra zibethicus were requested through a pan-Hellenic survey. According to the results, the coypu (Myocastor coypus) appears to be the most widely distributed of all species, having conquered practically all wetlands of Western and Central Greece with populations exceeding, in most cases, 20 individuals each. On the contrary, there is merely one unconfirmed record of the raccoon dog (Nyctereutes procyonoides) while there were no sightings at all for the muskrat (Ondatra zibethicus). The American mink (Neovison vison) was recorded in the northwestern part of Greece. Regarding the alien herpetofauna, the bullfrog (Lithobates catesbeianus) seems to be still confined in Crete where it was originally introduced, while the red-eared slider (Trachemys scripta) appears mostly in Crete, Attiki prefecture, and a few more places, showing most probably an underestimated distribution.

Lake Michigan's suitability for bigheaded carp: The importance of diet flexibility and subsurface habitat

“…Furthermore, Anderson et al. () demonstrated that BHC mitigated their weight loss and, in some cases, even gained weight when feeding only on dreissenid biodeposits. This suggests that the beneficial effect of supplementing model diets with detritus simulated by our model was reasonable given that BHC would have access to additional prey resources and a greater abundance of biodeposits in Lake Michigan than the rations fed to them by Anderson et al.…”

“…For both surface and whole water column scenarios, we ran simulations under three different diets: (1) phytoplankton only; (2) phytoplankton and zooplankton; and (3) phytoplankton, zooplankton, and detritus. We used prey energy density values of 2,600 J/g wet mass, 2,512 J/g wet mass, and 127.3 J/g wet mass for phytoplankton, zooplankton, and detritus, respectively (Anderson et al., , , ). We attributed the energy density of dreissenid mussel biodeposits to all Lake Michigan detritus—assuming that this is the most prevalent detrital food source in the lake (Madenjian, ).…”

“…Anderson et al. () reported the caloric quality of biodeposits ( ED Det ) as 979 J/g. However, the poor nutritional and energetic quality of organic detritus often reduces the amount of energy a fish can assimilate, i.e.…”

“…We accounted for this by adjusting ED Det by an assimilation efficiency coefficient of 0.13, which we derived by back‐calculating the assimilated energy density from the growth of juvenile BHC at the given food rations reported by Anderson et al. (). For each feeding scenario, we identified all cells containing suitable habitat and then calculated the volume‐weighted GRP average within all of those cells to determine the overall quality of suitable habitat.…”

“…() found that suitable habitat for BHC growth in Lake Michigan is limited to a few productive, nearshore areas, but they did not account for the fishes’ flexible diet or evaluate habitat beneath the surface (>1 m). While BHC typically feed on phytoplankton or zooplankton, they are also opportunistic feeders that are capable of surviving on diets dominated by organic detritus and bacteria (Anderson, Chapman, & Hayer, ; Chen, ; Kolar et al., ). Therefore, understanding how a BHC's diet plasticity influences their growth potential is an important next step for advancing our understanding of establishment risk.…”