Brachionus leydigii (Monogononta: Ploima) reported from the western basin of Lake Erie

Several species of non-indigenous planktonic invertebrates have historically been introduced to the Laurentian Great Lakes. Previous introductions of non-indigenous planktonic invertebrates to the Great Lakes have been crustacean zooplankton, specifically Cladocera and Copepoda. This report documents the first known occurrence of Brachionus leydigii var. tridentatus (Zernov, 1901) in Lake Erie and possibly the first detection of a non-indigenous rotifer species in the Laurentian Great Lakes. The specimen was collected from a U.S. EPA monitoring station in the western basin of Lake Erie on April 4, 2016.     

Testing for hybridization between Nile tilapia (Oreochromis niloticus) and blue spotted tilapia (Oreochromis leucostictus) in the Lake Edward system

Oreochromis is the most important tropical freshwater fish genus for aquaculture purposes, with various introduction and translocation events having played an integral part of its management. Some Oreochromis species such as the Nile tilapia, O. niloticus, are thought to be superior for aquacultural purposes when compared to other species. Hence, understanding the admixed nature of the species within a native system is of key importance for the development of future broodstock. Using a combination of mitochondrial (COI) and nuclear (microsatellites) DNA, we tested for the presence of O. niloticus and O. leucostictus hybrids within the Lake Edward-George system. The present study revealed that, despite their natural overlapping ranges, hybridization between O. niloticus and O. leucostictus appears to be rare within the Lake Edward-George system, suggesting that the native populations of these two species may serve as suitable broodstock to develop future aquaculture strains. Moreover, our study provides the first COI sequences for O. leucostictus from its native range and adds to the growing database of O. niloticus sequences.     

Importance of nonindigenous harpacticoids (Crustacea: Copepoda) decrease with depth in Lake Ontario

Harpacticoid copepods can be a substantial component of the meiobenthic community in lakes and serve an ecological role as detritivores. Here we present the first species-level lake-wide quantitative assessment of the harpacticoid assemblage of Lake Ontario with emphasis on the status of nonindigenous species. Additionally, we provide COI-5P sequences of harpacticoid taxa through Barcode of Life Data System (BOLD). Harpacticoids were collected at depths from 0.1 to 184 m and from a range of substrates from August to September 2018 as part of the Cooperative Science and Monitoring Initiative (CSMI) offshore benthic survey. Twenty-six meiobenthic samples were analyzed using microscopy for community composition analysis of harpacticoids. We found thirteen indigenous and three nonindigenous species of harpacticoid, with the introduced species dominating at shallow depths. The community transitioned from nonindigenous to indigenous species dominance as depth increased. Nonindigenous species accounted for 79% of the community (by abundance) at depths <20 m, 55% from 20 to 40 m, and only 24% at depths >40 m. The nonindigenous species encountered included the first detections of Schizopera borutzkyi (Monchenko, 1967) and Heteropsyllus nunni (Coull, 1975) from Lake Ontario. S. borutzkyi was the most abundant harpacticoid species in the lake, approaching a maximum density of 50,000/m² and a lake-wide average density of 7,900/m². Numerically important indigenous species included Bryocamptus nivalis (Willey, 1925), Canthocamptus robertcokeri (Wilson, 1958), Canthocamptus staphylinoides (Pearse, 1905), and Moraria cristata (Chappuis, 1929). The prevalence of nonindigenous harpacticoids in the meiobenthos of Lake Ontario suggests further investigations of Great Lakes meiofauna communities are warranted.     

Genomics reveals identity,phenology and population demographics of larval ciscoes (Coregonus artedi,C. hoyi,and C. kiyi) in the Apostle Islands,Lake Superior

We demonstrate, for the first time, the ability to reliably assign an assemblage of larval coregonines [Salmonidae Coregoninae] to shallow and multiple deepwater species. Larval coregonines from the Apostle Islands, Lake Superior, were genotyped using restriction site-associated DNA sequencing (RADseq) and were assigned to species using reference genotypes from adult corgonines from the same region. Of the 193 genotyped larvae, 101 were assigned as Coregonus artedi (average assignment probability = 97.6%), 57 were assigned as C. kiyi (average assignment probability = 95.5%), and 28 were assigned as C. hoyi (average assignment probability = 89.0%). Coregonus artedi were collected earliest in the season, followed by C. kiyi and then C. hoyi. Estimates of genetic diversity within each species provide a baseline for future monitoring in the Apostle Islands. Our success with species assignment indicates the promise of leveraging genomic data for larval coregonine identification, which could enable assessing and evaluating early life history dynamics and recruitment processes at the species level to the benefit of ongoing coregonine restoration and management efforts.     

Shifting status and distribution of range margin chorus frog (Pseudacris) populations in eastern Great Lakes watersheds

Contiguous with their range across major rivers into Canada, two different species of chorus frogs are now thought to inhabit the Great Lakes watersheds of New York. Pseudacris triseriata is found along the western Lake Ontario and Lake Erie plains while P. maculata (tentatively a new frog species in NY) inhabits the lowlands of eastern Lake Ontario and the St. Lawrence River. Both species are on their extreme range margins in NY. In 2010 we detected distributional declines of both putative chorus frog species based on a broad survey following standardized occupancy detection protocols. Causes are unclear but could relate to reforestation and urbanization of formerly more extensive agricultural lands, climate change, pathogenic fungal outbreaks and/or the contaminant effects of intensive agriculture. On the other hand, the prior overestimation of ranges because of misidentification may have inflated earlier perceived distributions (positive survey bias) because false positives are problematical for this cryptic frog. At broad geographical scales, chorus frog (meta)populations are highly dynamic and are likely shifting their ranges in response to rapidly changing overall environmental conditions in the northeastern U.S. and Canada.     

Fish and fishing in Lake Peipsi (Estonia/Russia) since 1851: Similarities and differences between historical and modern times

The first survey data on the fisheries in Lake Peipsi were collected by natural scientist Karl Ernst von Baer as a result of the world's first special fishery expedition in 1851–1852. In the current study, all available numerical datasets on fishing in Lake Peipsi from 1851 to 2018 have been drawn together in order to analyse the long-term changes in the lake’s fish assemblages. As the study indicates, the overexploitation, catching of juvenile fish and predator–prey imbalance have been common problems associated with fisheries in Lake Peipsi for the last two centuries. Similar to many inland waterbodies worldwide, total catch of fish from Lake Peipsi has decreased about four times since the mid-19th century, and the catch of lake (dwarf) smelt, a previously dominant species, has periodically fluctuated with long-term gradual reduction. The decline of cool-water fish, such as vendace, burbot and Peipsi whitefish during the last two centuries, and the domination of Eurasian perch, common bream and pike-perch in the catches of the last 20 years mark considerable structural shifts in fish assemblages. Of the multiple stressors (e.g., nutrient enrichment, increased water temperature, overfishing) triggering shifts in fish assemblages, the impact of climate warming, especially extreme weather events such as heatwaves, seems to be the strongest during the last three decades. However, none of the fish species have completely disappeared from the lake during the last century although the share of cool-water fish in the total catch has declined about tenfold since the 1930s.     

Lidar (light detection and ranging) and benthic invertebrate investigations: Migrating tailings threaten Buffalo Reef in Lake Superior

The low turbidity of northern Great Lakes waters allows lidar sufficient penetration to greatly aid environmental studies of coastal environments. On the Keweenaw Peninsula of Lake Superior, Big Traverse Bay provides an excellent example of mine tailings spreading from an old coastal release site. Between 1901 and 1932, two stamp mills (Mohawk and Wolverine) discharged 22.7 million metric tonnes of tailings (stamp sands) off the town of Gay. Along beaches, migrating stamp sands have dammed stream outlets, encroached upon wetlands, and contaminated recreational beaches. The tailings are now threatening benthic environments and critical commercial fish breeding grounds. Buffalo Reef is important for commercial and recreational lake trout and lake whitefish production (32% of the commercial catch in Keweenaw Bay, 22% of southern Lake Superior). Aerial photographs and five lidar over-flights emphasize: 1) the enormous amounts of stamp sands moving along the shoreline, and 2) large amounts migrating underwater across the bay towards Buffalo Reef. Differences between 2008 and 2016 lidar over-flights are used to quantify underwater stamp sand movement. For years, tailings have accumulated in an ancient riverbed cut (“trough”) just north of Buffalo Reef. Stamp sand overflow out of the “trough” is now moving into Buffalo Reef cobble fields, where fish drop eggs. Ponar sediment studies quantify % stamp sand in sand mixtures around Buffalo Reef, copper concentrations, and quantify impacts on benthic invertebrate taxa. Our study emphasizes that when large amounts of mine tailings are discharged into coastal environments, temporal and spatial impacts are progressive, threatening benthic organisms and fish.