Recent ecological trends in lower trophic levels of the international section of the St. Lawrence River: a comparison of the 1970s to the 2000s

Low dissolved ions may limit secondary invasion of inland waters by exotic round gobies and dreissenid mussels in North America

“…In previous years (2002)(2003)(2004)(2005) we have measured similar densities upstream near Cape Vincent and in the 1,000 Islands (B. Baldwin unpublished data) and our Lake St. Lawrence densities, converted to wet mass m -2 (using relationships from Baldwin et al 2002), ranged from about 800 to 4,000 g m -2 (mean 1,730 g m -2 ), which overlaps with several dreissenid population estimates downstream near Montreal (Jones and Ricciardi 2005). Farrell et al (2010) found lower benthic invertebrate densities in the upper SLR, likely because of differences in sampling technique, but like us, they found dominance of quagga mussels over zebra mussels.…”

“…Despite this, we feel our goby populations are comparable to other Great Lake locations from which they have spread to inland tributary systems (Irons et al 2006;Krakowiak and Pennuto 2008;Kornis and Vander Zanden 2010;Poos et al 2010). The round goby populations we documented along the riverbed, offshore of the littoral zone, may also be similar to those observed (densities unreported) in profundal zone sites in the upper SLR (Farrell et al 2010). Certainly the lower densities (up to 400 ha -1 or 0.04 m -2 ) they documented in littoral zone sites (using seining techniques) agree with our general observations (while scuba diving) of increasing densities from the shoreline to deeper census sites along the riverbed.…”

“…1) and, with the Lake as a major recreational boating and fishing area, inadvertent human transfer may exist between the lake and a host of inland waters. We also hoped that our data would fill an important regional gap between similar surveys in the uppermost SLR (Farrell et al 2010) and downstream surveys of dreissenids near Montreal (Jones and Ricciardi 2005).…”

Predictive factors and viral genetic diversity for viral hemorrhagic septicemia virus infection in Lake Ontario and the St. Lawrence River

“…In the St. Clair River, Lake St. Clair, and the Detroit River, densities of round goby ranged from 0.3 to 9 fish per m 2 (Ray and Corkum, 2001). In the Thousand Islands region of the St. Lawrence River, round goby densities ranged from 0 to almost 500 fish per standardized seine haul (Farrell et al, 2010). Additional, comprehensive surveillance will be needed in the future not only to monitor changes in VHSV prevalence in the Laurentian Great Lakes but also to continue to determine the role of additional potential predictive factors, especially density and temperature, that may be associated with infection in wild fish.…”

“…It was not possible to measure fish density given the experimental design of this study. However, in the region of the St. Lawrence River downstream of the Thousand Islands (near Ogdensburg), channel current velocities can be up to five times higher than in upstream regions of the St. Lawrence (Farrell et al, 2010), which can lead to decreased fish densities. Within the Thousand Islands region, round goby density tends to decrease downstream (toward Alexandria Bay), although round goby density in Ogdensburg was not measured (Farrell et al, 2010).…”