Distribution and ecology of Hemimysis anomala, the latest invader of the Great Lakes basin

Abstract

Since 2006, the known distribution of Hemimysis anomala has greatly expanded in the Great Lakes ecosystem, with, to date, 45 sites of occurrence among 91 monitored sites, located in four of the Great Lakes and the upper St. Lawrence River. By means of carbon and nitrogen stable isotopes, a first assessment of the feeding ecology of Hemimysis was completed. The d 13 C values of 18 individuals collected in Lake Erie (Port Mainland) on a single date (Sept. 23, 2008) ranged from -30.2 to -24.5%, indicating that Hemimysis could feed on multiple carbon sources including pelagic and littoral autochthonous and terrestrial carbon. In Lake Erie, variation in d 13 C was related to d 15 N, indicating the importance of food source for determining the trophic position of Hemimysis. The d 15 N signatures of individuals were strongly related to their C/N ratios, suggesting that variations in the nutritional value of Hemimysis may depend on trophic position. Isotopic variation among individuals in Lake Erie was complemented by temporal variation in Lake Ontario. Monthly changes (from June to December 2008) in carbon isotope signatures were observed and related to changes in water temperature, highlighting the variations in the baseline prey signatures that fuel Hemimysis diets. The observed variation in stable isotope signatures occurring among individuals within a localized Hemimysis assemblage and temporally should be considered as a key design feature in further studies attempting to identify the possible effects of Hemimysis on nearshore food webs in the Great Lakes.

First occurrence of the mysid Hemimysis anomala in an inland lake in North America, Oneida Lake, NY

“…We found Hemimysis in adult white perch and yellow perch diets, and they have been reported in diets of alewife, yellow perch, and rock bass in Lake Ontario ). Sizes of Hemimysis in Oneida Lake were similar to sizes reported in Lake Ontario (1.6-8.2 mm; Marty et al, 2010), Lake Michigan (mean sizes 6.9-7.0 mm; Pothoven et al, 2007), and the St. Lawrence River (mean sizes 5.6-7.3 mm; Kestrup and Ricciardi, 2008).…”

Swarms of the Ponto-Caspian mysid Hemimysis anomala in Montreal Harbour, St. Lawrence River, Canada

“…Our finding represents the most downstream location for the reported occurrence and establishment of Hemimysis within the entire Great Lakes -St.Lawrence River basin so far. The fact that the species is now reported in all Great Lakes (except for Lake Superior) after being first detected in 2006 (Marty et al, 2010;Pothoven et al, 2007;Walsh et al, 2010) and the actual evidence for established populations in the Montreal area suggest that the species would probably be found further downstream along the SLR. Due to its ability to survive and reproduce in saline waters up to 18 PSU (Marty, 2008), Hemimysis could also be found in the upper St.Lawrence Estuary.…”

“…The first 100 Hemimysis sorted from each sample were taken for size measurements and sex determination. Using an image-analyzing system integrated to a Leica stereomicroscope, the body length of Hemimysis was measured as the distance from the tip of the rostrum to the end of the last abdominal segment just prior to the telson (Marty et al, 2010). Sex was determined for specimens N 5-6 mm long, based on pleopods morphology, as well as presence-absence of a brood pouch .…”

“…The bloody-red shrimp, Hemimysis anomala, is a brackish-water mysid adapted to freshwater and characterized by a high rate of invasion as shown by its recent spread in western Europe (Minchin and Holmes, 2008) as well as in the Great Lakes basin (Marty et al, 2010;Walsh et al, 2010). Presumably to avoid predation, this macroinvertebrate species forms large and dense swarms (Salemaa and Hietalahti, 1993) which can lead to high variability in the number of organisms over space and time.…”

“…Initially reported both in Lake Michigan and Lake Ontario in 2006 (Marty, 2008;Pothoven et al, 2007), Hemimysis rapidly spread throughout the Laurentian Great Lakes-St.Lawrence River (GL-SLR) basin (Marty et al, 2010). It was first reported in the St.Lawrence River (SLR) in July 2008 (Kestrup and Ricciardi, 2008) as well as in the port of Montreal the same year (de Lafontaine, unpubl.…”