Monday, October 1, 2012



Hi Wyatt,


Your e-mail was forwarded to NYSDEC's Lake Ontario Unit. We share your concern about potential round goby impacts to our sport fish populations. Round gobies are found throughout lakes Erie and Ontario and the St. Lawrence River and have been captured over a broad depth range. Gobies can impact fish populations by acting as both predator and prey. They are egg and fry predators; however, in Lake Ontario dreissenid mussels (i.e. zebra and quagga mussels) represent an important component of round goby diet. At deeper depths our native freshwater invertebrate, Mysis relicta, is also an important component of their diet. Round goby may negatively impact the reproductive success of some fish populations where distributions overlap with spawning and nursery habitat. They are also an abundant alternative prey for many of our fish species including bass, perch, brown trout, lake trout and many other species. Improved condition of several species is attributed to their consumption of gobies. Round goby has become the primary prey of double-crested cormorant colonies in Lake Ontario and the St. Lawrence River.

Brown trout, rainbow trout, Chinook Salmon, coho salmon, and Atlantic salmon spawn in the tributaries where gobies are not present. Among our trout and salmon species, lake trout is the only one with spawning habitat that overlaps with goby distribution. Several factors are likely impacting lake trout reproductive success in Lake Ontario, including poor egg quality due to low thiamine levels, spawning habitat quantity and quality (i.e. impacts to quality due to dreissenid mussels and cladophora, etc.), goby predation, mature lake trout population size, etc. Despite numerous impediments to reproductive success we have documented 15 consecutive year classes of naturally reproduced lake trout in Lake Ontario, most of these occurring since gobies became abundant in the lake.

To date, available data does not indicate that gobies have negatively impacted warm water sport fish at the population level. Gill netting assessments are conducted annually in Lake Erie, Lake Ontario's eastern basin, and the Thousand Island and Lake St. Lawrence areas of the St. Lawrence River to provide us with indices of abundance for some of our warm water fish species including yellow perch, smallmouth bass, and walleye. These surveys also provide us with valuable information of age, growth and condition, and survival of these species.

Your e-mailed mentioned that someone said 'there are areas where there aren't any more perch'. Do you know where he was referring to? This year was atypical for anglers fishing some areas – such as the eastern basin of Lake Ontario. Many anglers reported that the perch were gone and they could not find or catch them. While anglers were reporting this, we were conducting our gillnetting assessment in the same area and catching perch, most of which were caught by nets set in relatively deep water (approximately 60-95'). The relatively warm water in 2012 may have contributed to a change in distribution of perch as compared to previous years. The yellow perch indices of abundance, as determined from gill netting, indicate that populations are similar to (Thousand Islands, St. Lawrence River) or higher than (Lake St. Lawrence in the St. Lawrence River, eastern basin Lake Ontario, and Lake Erie) years prior to the goby invasion. Angler surveys conducted in the St. Lawrence River, Lake Ontario and Lake Erie also suggest improved status of the perch populations in recent years.

The status of smallmouth bass is complex and differs with location. You mention Wolfe Island and the Ducks, both areas are outside of our assessment areas. I spoke with an eastern basin charter captain to find out if he had any insight on those specific areas. Information from him and a couple of other charter captains who fish the Ducks indicated that they experienced continued good fishing quality at the Ducks and kept limits of bass of a variety of sizes (several trips, limiting out nearly every time, bass 12" up to >4lbs) which is consistent with your description of bass still being present. They weren't able to provide much insight for the Wolfe Island area since they rarely fish there. Gill netting assessment data from the St. Lawrence River, Lake Ontario Eastern Basin and Lake Erie indicate that bass recruitment has not declined. Gobies have been abundant in Lake Erie since 2000 and bass recruitment (natural production of bass that survive to older ages) has remained in the range that was observed before goby. To date, there is no evidence that bass recruitment in the eastern basin of Lake Ontario has been negatively impacted since gobies entered the system. Data has shown that most of the annual variability in bass recruitment is attributable to mean summer (June – August) water temperatures in some Province of Ontario waters (including the eastern basin of Lake Ontario) and in Lake Erie (both before and since gobies). Additionally, smallmouth bass growth rate and condition improved in recent years, attributable in part, to a diet shift to round goby. Declining smallmouth bass fishing quality was documented for and appears primarily limited to anglers targeting smallmouth bass along Lake Ontario's south shore. The cause of poor fishing quality on the south shore is not well understood and we cannot determine the exact cause(s) of the decline with available data. Many of the same factors affecting Lake Ontario's southern shore fish populations are also affecting Lake Ontario's Eastern Outlet Basin, the St. Lawrence River and Lake Erie bass populations, including, invasive species (round goby, Viral Hemorrhagic Septicemia virus (VHSv), zebra and quagga mussels, Hemimysis ["bloody red shrimp"], etc.), Cladaphora ("wiches hair"), and nutrient and water clarity changes. Unlike the southern shore, however, these regions have continued to provide quality bass angling and high quality bass.

Again, we share your concerns over potential goby impacts to Lake Ontario's sport fish populations and will continue to evaluate data from our long-term assessment programs to detect changes in recruitment and other population parameters. Please contact me if you have any questions or would like any additional information.



Jana R. Lantry

Aquatic Biologist, Lake Ontario Unit

NYS Department of Environmental Conservation

Cape Vincent Fisheries Station

541 East Broadway

Cape Vincent, NY 13618

Office: 315-654-2147

Fax: 315-654-4118