The bloody-red shrimp (Hemimysis anomala, hereafter BRS) is one of the most recent of a string of aquatic invertebrates native to the Ponto-Caspian region of Eurasia to become established in waterways throughout the Great Lakes and Hudson River (New York, USA) basins. BRS are voracious predators of zooplankton and have decimated cladoceran prey populations, in particular, in some invaded systems in Europe. They also represent an abundant, high-calorie option for nearshore fish in invaded North American waterways, representing a potentially important energy subsidy or alternative food source for nearshore fish. Our collaborative team of research scientists, high school students, and undergraduate interns use a multifaceted approach to (1) quantify the potential predation of both native and naturalized fish species on BRS prey through controlled feeding experiments, (2) improve early detection and BRS range expansion estimates by conducting targeted scientific and citizen science-based surveys, and (3) document the behavioral interactions and spatial overlap of BRS with fish predators through a combination of SCUBA and remotely operated vehicle (ROV) videography.
Results/Conclusions
Fish feeding experiments performed at various BRS densities under natural twilight conditions revealed that all fish predators were capable of feeding on BRS, but that feeding rates varied by both type of predator as well as substrate. When the number of BRS consumed out of an available 60 individual prey items were compared in open aquaria, we report the following hierarchy of number of prey consumed: alewife > yellow perch > goby > trout > pumpkinseed. In BRS-preferred (rounded cobble) substrate conditions, the rankings shifted strongly in favor of round gobies (goby > alewife > trout > perch > pumpkinseed.) Plankton net survey work confirmed that BRS is utilizing canals as important vectors of spread throughout New York State’s Finger Lakes and other inland lakes and that the species has become firmly established in the Hudson River via the Erie Canal. Citizen scientists utilized economical plankton nets and experimental light traps to help spread awareness of the BRS invasion and contribute to early detection efforts. SCUBA and ROV monitoring helped to reveal subtle microhabitat characteristics, including the size and dimensions of interstitial space, to better predict viable habitat conditions for successful BRS establishment. These in situ observations were paired with laboratory habitat choice experiments performed under different light and substrate conditions that revealed strong preferences for rocky habitats with tight interstitial spaces versus sandy or mussel-colonized habitats.