Fish and Macroinvertebrate Communities in Tributary Streams of Eastern Lake Erie with and without Round Gobies (Neogobius melanostomus, Pallas 1814)

Round gobies have had significant impacts on benthic fish and invertebrate communities in nearshore habitats of the Great Lakes. As round gobies have become more abundant in lake habitats, there has been an expansion of their populations into tributary streams and rivers. We compared stream invertebrate and fish communities in New York tributaries to Lake Erie with round gobies present and absent. Four of six benthic invertebrate metrics differed between streams with and without round gobies. Streams with round gobies present had reduced Shannon diversity, EPT richness, and EPT/chironomid ratios, and increased macroinvertebrate density relative to streams without round gobies, but there was no difference in non-Diptera density, or total taxa richness. None of the four fish metrics examined differed between streams with and without round gobies. However, darters occurred in all streams lacking round gobies, but did not occur in any streams with round gobies. Comparisons with historical fish and macroinvertebrate distributional data support our suspicion of goby-induced community changes. In these New York streams, round gobies seem to have had significant impacts on invertebrate communities via their consumptive behavior, whereas the impacts on fish communities are less evident. If round gobies continue to expand their distribution inland, the resultant alterations in macroinvertebrate communities may impact the suitability of tributary streams as spawning and nursery habitat for several sport fish species and for energy dynamics in tributary streams.     

First report of tubenose goby (Proterorhinus semilunaris) in the eastern basin of Lake Erie

The tubenose goby (Proterorhinus semilunaris), native to the Ponto-Caspian region, was first discovered in the Laurentian Great Lakes in 1990 after it was introduced through ballast water discharge. Compared with Neogobius melanostomus, another exotic gobiid from the Ponto-Caspian, colonization of the Great Lakes by P. semilunaris has been slow, with reports of the species being largely confined to the Huron-Erie Corridor (HEC) and western portions of Lake Erie and Lake Superior. This is the first report of P. semilunaris in the Great Lakes east of the western basin of Lake Erie. Between 28 June and 27 July, 2012, 176 P. semilunaris were collected from shallow (< 1.2 m) water of Marina Lake, a 40 ha embayment in Presque Isle State Park (Erie, PA). The large number of P. semilunaris collected at the site and the presence of individuals as small as 17 mm total length suggest an established population. However, the mechanism by which P. semilunaris was introduced to Presque Isle Bay is not clear.     

Impacts of the Introduced Round Goby (Apollonia melanostoma) on Dreissenids (Dreissena polymorpha and Dreissena bugensis) and on Macroinvertebrate Community between 2003 and 2006 in the Littoral Zone of Green Bay,Lake Michigan

We show that the invasion of round gobies (Apollonia melanostoma) in Green Bay, Lake Michigan, has changed the benthic food web in fundamental ways related to their impact on invasive dreissenid mussels. Dreissenid mussels are of specific interest because they are one of the primary dietary items for round gobies. In this study, we collected rocks from each of 10 study sites along approximately 60 km of the eastern shoreline of Green Bay, Lake Michigan, to assess a temporal change in macroinvertebrate abundance related to the northward movement of the round goby invasion front from a point about midway along the shoreline in 2003 to the entire coast in 2006. The pattern of macroinvertebrate abundance in 2003 suggested that round gobies had already caused significant decreases in macroinvertebrate abundances south of the invasion front (interpretation of the data could have been compromised by confounding environmental gradients). In subsequent sampling in 2006 macroinvertebrates were picked off of sampled rocks in the field and underwater transects were videotaped to estimate round goby abundance at each site. Round gobies were collected for stomach analysis to assist in determining which invertebrates would likely be impacted by goby predation. Our results indicated that by 2006, round gobies had become abundant at those sites where they were absent in 2003 and zebra mussels (Dreissena polymorpha), quagga mussels (Dreissena bugensis), isopods, amphipods, trichopterans, and gastropods in the newly invaded sites had significantly decreased at the newly invaded sites.     

Density and habitat use by the round goby (Apollonia melanostoma) in the Bay of Quinte,Lake Ontario

We assessed round goby (Apollonia melanostoma) density and size structure in two sections of the Bay of Quinte (Lake Ontario) that had been invaded by this species two years apart. Round goby density was assessed with 50 m linear transects, recorded with an underwater video recording apparatus developed for this study that included a depth sounder for maintaining a fixed distance above the substrate. The highest mean round goby densities were observed in the shallowest depth zone (1.5–3 m) at both sites, but there were differences between the sites in the habitat types where the highest densities occurred and there were no significant density differences among habitat types at either site (rock with sparse vegetation, mud with sparse vegetation, sand/mud with moderate vegetation cover). In the upper bay, mean body length of round gobies declined with depth, whereas in the lower bay, mean round goby length was greatest in the deepest zone. Mean body length of round gobies did not differ significantly by habitat type in either section of the bay.     

Ecology and population status of Trout-perch (Percopsis omiscomaycus) in western Lake Erie

Trout-perch Percopsis omiscomaycus is among the most abundant benthic species in Lake Erie, but comparatively little is known about its ecology. Although others have conducted extensive studies on trout-perch ecology, those efforts predated invasions of white perch Morone americana, Dreissena spp., Bythotrephes longimanus and round goby Neogobius melanostomus, suggesting the need to revisit past work. Trout-perch were sampled with bottom trawls at 56 sites during June and September 2010. We examined diets, fecundity, average annual mortality, sex ratio, and long-term population trends at sites sampled since 1961. Trout-perch abundance fluctuated periodically, with distinct shorter- (4-year) and longer-term (over period of 50 years) fluctuations. Males had higher average annual mortality than females. Both sexes were equally abundant at age 0, but females outnumbered males 4:1 by age 2. Diets of trout-perch were dominated by macroinvertebrates, particularly chironomids and Hexagenia sp. Size distributions of trout-perch eggs varied widely and exhibited multiple modes indicative of protracted batch spawning. A review of the few other studies of trout-perch revealed periodic fluctuations in sex ratio of adults, which in light of our evidence of periodicity in abundance suggests the potential for sex-ratio-mediated intrinsic population regulation. Despite the introduction of numerous invasive species in Lake Erie, trout-perch remain one of the most abundant benthic invertivores and the population is relatively stable.     

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.     

Size-selective predation by round gobies (Neogobius melanostomus) on dreissenid mussels in the field

Although numerous studies have shown that round gobies (Neogobius melanostomus) prey on dreissenid mussels (Dreissena polymorpha and Dreissena bugensis), there is an apparent shortage of detailed field studies on the subject. The 5-month field study described here quantifies predation by round gobies on dreissenids in Presque Isle Bay, Lake Erie. Dreissenids dominated the diet of round gobies, composing 92% of the prey items recovered. Over half of the 3870 valves (1935 mussels) recovered from 155 round gobies were crushed, while the remainder were swallowed whole. Crushed dreissenids were larger than those swallowed whole, and the tendency to crush dreissenids did not vary among three length classes of round goby. Round goby length was positively related to average size of dreissenids consumed, average size of whole and crushed dreissenids, largest whole dreissenid consumed, and largest crushed dreissenid consumed. Indices of selectivity revealed similarly shaped curves for three length classes of round gobies, a shift toward larger dreissenid size classes with an increase in round goby length, and peak preferences for 8-11 mm dreissenids. Factors such as gape limitation, availability and accessibility of differently sized dreissenids, forces generated while removing mussels from the substrate and crushing them, and caloric content of dreissenids all likely play roles in the observed size-selectivity and differential processing of dreissenids. Although factors influencing size-selectivity are not completely understood, the observed preference of round gobies for dreissenids near the size when they are first reproductive could impact the demography of dreissenid populations.     

Distribution and abundance of freshwater polychaetes, Manayunkia speciosa (Polychaeta), in the Great Lakes with a 70-year case history for western Lake Erie

Manayunkia speciosa has been a taxonomic curiosity for 150 years with little interest until 1977 when it was identified as an intermediate host of a fish parasite (Ceratomyxa shasta) responsible for fish mortalities (e.g., chinook salmon). Manayunkia was first reported in the Great Lakes in 1929. Since its discovery, the taxon has been reported in 50% (20 of 40 studies) of benthos studies published between 1960 and 2007. When found, Manayunkia comprised < 1% of benthos in 70% of examined studies. In one extensive study, Manayunkia occurred in only 26% of 378 sampled events (1991–2009). The taxon was found at higher densities in one area of Lake Erie (mean = 3658/m²) and Georgian Bay (1790/m²) than in five other areas (mean = 60 to 553/m²) of the lakes. A 70-year history of Manayunkia in western Lake Erie indicates it was not found in 1930, was most abundant in 1961 (mean = 8039, maximum = 67,748/m²), and decreased in successive periods of 1982 (3529, 49,639/m²), 1993 (1876, 25,332/m²), and 2003 (79, 2583/m²). It occurred at 48% of stations in 1961, 58% in 1982, 52% in 1993, and 6% of stations in 2003. In all years, Manayunkia was distributed primarily near the mouth of the Detroit River. Causes for declines in distribution and abundance are unknown, but may be related to pollution-abatement programs that began in the 1970s, and invasion of dreissenid mussels in the late-1980s which contributed to de-eutrophication of western Lake Erie. At present, importance of the long-term decline of Manayunkia in Lake Erie is unknown.     

Spatial and temporal variation in the distribution of burrowing mayfly nymphs (Ephemeroptera: Hexagenia limbata and H. rigida) in western Lake Erie

In the early 1990s, burrowing mayfly species reappeared in sediments of the western basin of Lake Erie after an absence of over 30 years due to episodic hypoxia at the sediment–water interface. Long-term monitoring of adult mayflies at shoreline areas had revealed that Hexagenia rigida was more abundant than Hexagenia limbata during the initial recolonization period, but was gradually replaced by H. limbata. We hypothesized that this shift in dominance would be confirmed by the distribution and abundance of nymphs. We identified nymphs collected each spring throughout western Lake Erie from 1997 to 2004. The relative abundances of H. rigida and H. limbata nymphs exhibited the same temporal sequence as adults. Furthermore, the number of sites in the western basin in which H. rigida occurred decreased as the occurrence frequency of H. limbata increased. H. limbata were dominant in the basin by 2004. Hexagenia limbata nymphs persisted in the center-most part of the basin, whereas H. rigida did not, possibly due to differences in tolerance to hypoxia. There were no significant differences in body size between the two populations. Differences in dispersal distance from source populations and the timing and success of egg hatching likely accounted for the initial colonizing success of H. rigida, but the differential ability of H. limbata eggs to overwinter in sediments and possible tolerance of nymphs to hypoxia has possibly led to its current dominance in the western basin.     

Changes in the Crustacean Communities of the Central Basin of Lake Erie during the First Full Year of the Bythotrephes longimanus Invasion

The exotic predatory cladoceran Bythotrephes longimanus was first observed in Lake Erie on 19 September, 1985. During the early summer immediately prior to its appearance, the cladoceran community in the central basin of Lake Erie was characterized by large populations of Bosmina longirostris, Eubosmina coregoni, Daphnia mendotae, and Daphnia retrocurva, with the latter three species persisting throughout August and September, along with Diaphanosoma spp. Community composition during early summer 1986 was similar to that of the previous year, but densities of all cladocerans decreased dramatically coincident with the appearance of Bythotrephes in mid-July, and remained suppressed throughout August and September. Only D. mendotae was present in appreciable numbers during this period; from mid-July through the end of August, 86-98% of cladoceran biomass (exclusive of Bythotrephes and Leptodora) was contributed by D. mendotae. Densities of Leptodora and Bythotrephes showed a strikingly inverse relationship, both temporally and spatially, during 1986. Size frequency distributions of D. mendotae exhibited an immediate shift towards extremely large ( > 2.5 mm) individuals coincident with Bythotrephes’ appearance in 1986, suggesting an upper size limit to efficient prey utilization by Bythotrephes. These results suggest that Bythotrephes can have substantial impacts both on cladoceran community composition, and on the size distributions of individual species.     

Seasonal distribution of bloater (Coregonus hoyi) in the waters of Lake Huron surrounding the Bruce Peninsula

Information about bloater (Coregonus hoyi) habitat in Lake Huron was limited to correlations between commercial yield and fishing depth, despite available information from other Great Lakes. We identified seasonal patterns of bloater habitat use in hypolimnetic waters surrounding the Bruce Peninsula, Lake Huron. We applied a delta-lognormal model to fisheries-independent survey data to evaluate whether bloater catch-per-unit-effort was related to depth, temperature, and bathymetric slope. A Bayesian variable selection technique indicated that bloater distribution was most strongly related to bottom depth and water temperature. Our study also reconfirmed a previously-described pattern of seasonal inshore movement during warmer months followed by a return to deeper offshore waters during cooler months. By focusing our sampling within the hypolimnion, we characterized intra-annual patterns of bloater habitat use with respect to a temperature gradient near the minimum thermal requirements reported for this species. Bloater distribution under these thermal conditions has not been previously reported.     

The effect of mayfly (Hexagenia spp.) burrowing activity on sediment oxygen demand in western Lake Erie

Previous studies support the hypothesis that large numbers of infaunal burrow-irrigating organisms in the western basin of Lake Erie may increase significantly the sediment oxygen demand, thus enhancing the rate of hypolimnetic oxygen depletion. We conducted laboratory experiments to quantify burrow oxygen dynamics and increased oxygen demand resulting from burrow irrigation using two different year classes of Hexagenia spp. nymphs from western Lake Erie during summer, 2006. Using oxygen microelectrodes and hot film anemometry, we simultaneously determined oxygen concentrations and burrow water flow velocities. Burrow oxygen depletion rates ranged from 21.7 mg/nymph/mo for 15 mm nymphs at 23 °C to 240.7 mg/nymph/mo for 23 mm nymphs at 13 °C. Sealed microcosm experiments demonstrated that mayflies increase the rate of oxygen depletion by 2–5 times that of controls, depending on size of nymph and water temperature, with colder waters having greater impact. At natural population densities, nymph pumping activity increased total sediment oxygen demand 0.3–2.5 times compared to sediments with no mayflies and accounted for 22–71% of the total sediment oxygen demand. Extrapolating laboratory results to the natural system suggest that Hexagenia spp. populations may exert a significant control on oxygen depletion during intermittent stratification. This finding may help explain some of the fluctuations in Hexagenia spp. population densities in western Lake Erie and suggests that mayflies, by causing their own population collapse irrespective of other environmental conditions, may need longer term averages when used as a bio-indicator of the success of pollution-abatement programs in western Lake Erie and possibly throughout the Great Lakes.     

First documentation of spawning and nest guarding in the laboratory by the invasive fish,the round goby (Neogobius melanostomus)

Although the round goby, Neogobius melanostomus, is widespread in the Great Lakes and has an extended breeding season with a high reproductive rate; its spawning behaviour remains elusive. We present the first reported accounts of spawning by the round goby in the laboratory. By simulating winter conditions and restoring spring conditions, we induced round gobies to spawn in October 2007, March 2008, May 2008, and January 2009. In one case, fanning by the nest-holding male began 10 days before egg deposition and, during this period, the male rubbed secretions along the ceiling of the nest. Males were choosy about which gravid females entered the nest and prevented entry by some females. Spawning involved repeated inversions by females and males releasing gametes on the ceiling of the nest. Males guarded the nest by blocking the entrance, producing agonistic vocalizations and chasing intruders. Inside the nest, eggs were regularly inspected by the males and constantly ventilated using pectoral and caudal fins. Up to three gravid females spawned sequentially in a nest. Peak ventilation occurred after egg deposition and declined with time until the parental male ate the eggs. The decline of parental care and egg cannibalism was likely an artifact of laboratory conditions and small brood size. Our findings offer new information on the reproductive habits of the invasive round goby. Because the reproductive sequence in the laboratory seems easy to disrupt, the procedures may lead to a management tool to control the spread of the species into new areas.     

Impacts of predation by the Eurasian round goby (Neogobius melanostomus) on molluscs in the upper St. Lawrence River

An invasive Eurasian fish, the round goby Neogobius melanostomus, has recently spread from the Great Lakes into the St. Lawrence River. We quantified prey preferences of this benthivore and determined whether its predatory impacts on molluscs in the river are similar to those in the Great Lakes. We measured the size structure of gastropods and dreissenid mussels at 13 St. Lawrence River sites where round goby densities ranged from 0 to 6 m^− 2. For four of these sites, data were available for multiple years before and after invasion. Contrary to studies in the Great Lakes, there were no consistent effects of round goby density on the size structure of dreissenids, although there was an ontogenetic diet shift toward dreissenids. However, the abundance and richness of small gastropods (≤ 14 mm) was negatively correlated with round goby density across all sites, and declined over time at three of four sites sampled before and after invasion. Median gastropod size also declined across sites with increasing round goby density. Gastropods (as well as chironomid larvae, caddisfly larvae, and ostracods) were consistently among the most preferred prey items consumed by gobies, whereas dreissenids (as well as leeches and freshwater mites) were consistently avoided. These results indicate the major role of the round goby in structuring gastropod populations in the St. Lawrence River, and highlight large-scale spatial variation in its predatory impact on dreissenid populations.     

Observations on Twinning in the Sea Lamprey (Petromyzon Marinus) in the Laboratory

Forty-five sets of separate, normal twins were produced from four portions of the eggs from one female sea lamprey (Petromyzon marinus) each fertilized by a different male. The percentage of twinning in the different groups of embryos ranged from 1.0 to 1.7. Although the development of some of the twins was slightly slower than average, that of most was within the normal range for sea lamprey embryos. The twins were smaller than non-twins, and one twin was usually smaller than the other. Although the discovery of Siamese twins in fish is not uncommon, separate, normal twins have seldom been reported.     

Distribution of Larval Yellow Perch (Perca Flavescens) in Nearshore Waters of Southeastern Lake Michigan

Spatial and temporal distribution of larval yellow perch (Perca flavescens) in southeastern Lake Michigan was described from samples collected during 1973–1981 with plankton nets and benthic sleds in water 0.5 to 21 m deep. Yellow perch larvae ≤ 7.5 mm total length were numerous from mid-May to early or mid-July. Larvae taken before mid-June hatched from eggs spawned in inland waters, rather than in Lake Michigan. Those larvae appearing early occurred chiefly in shallow water (≤1.5 m), whereas larvae caught later were chiefly distributed in deeper water (≥ 6 m). Larval perch abundance was similar at all bottom depths ≥ 6 m, was low in surface water during the day, and low near bottom at night. At 0.5- and 1.5-m stations, significantly more larvae were caught at night than during the day.     

Philopatry and vagrancy of white bass (Morone chrysops) spawning in the Sandusky River: Evidence of metapopulation structure in western Lake Erie using otolith chemistry

Although natal homing and philopatry are well studied in anadromous salmon, few studies have investigated philopatric behavior in large, freshwater systems. In western Lake Erie, white bass (Morone chrysops) undergo seasonal spawning migrations from the open-water regions of Lake Erie to nearshore reef complexes and tributaries. The three primary spawning locations in Lake Erie are within 80 km of each other and are not separated by physical barriers. We used naturally occurring differences in otolith strontium concentrations among major spawning locations to address philopatry and vagrancy to the Sandusky River spawning location. Most individuals spawning in the Sandusky River were natal to this river (73%). No statistically significant differences in the extent of homing by sex or age of spawning were found, although a potential pattern of decreased homing with increased age of fish was observed. Given the proportion of vagrant individuals we found spawning in the Sandusky River (27%), it is unlikely that Lake Erie white bass spawning populations are genetically distinct. Furthermore, the white bass population in Lake Erie appears to be structured as a metapopulation, with non-philopatric individuals serving as a link between spawning populations.     

Evaluating the growth potential of sea lampreys (Petromyzon marinus) feeding on siscowet lake trout (Salvelinus namaycush) in Lake Superior

Differences in the preferred thermal habitat of Lake Superior lake trout morphotypes create alternative growth scenarios for parasitic sea lamprey (Petromyzon marinus) attached to lake trout hosts. Siscowet lake trout (Salvelinus namaycush) inhabit deep, consistently cold water (4-6 °C) and are more abundant than lean lake trout (Salvelinus namaycush) which occupy temperatures between 8 and 12 °C during summer thermal stratification. Using bioenergetics models we contrasted the growth potential of sea lampreys attached to siscowet and lean lake trout to determine how host temperature influences the growth and ultimate size of adult sea lamprey. Sea lampreys simulated under the thermal regime of siscowets are capable of reaching sizes within the range of adult sea lamprey sizes observed in Lake Superior tributaries. High lamprey wounding rates on siscowets suggest siscowets are important lamprey hosts. In addition, siscowets have higher survival rates from lamprey attacks than those observed for lean lake trout which raises the prospect that siscowets serve as a buffer to predation on more commercially desirable hosts such as lean lake trout, and could serve to subsidize lamprey growth.     

Progress Toward the Rehabilitation of Lake Trout (Salvelinus namaycush) in South Bay,Lake Huron

Our objective was to evaluate the status of lake trout Salvelinus namaycush rehabilitation in South Bay, Lake Huron. Standardized surveys were conducted to quantify natural recruitment, annual mortality, and the contribution of wild-versus hatchery-origin lake trout. Some indicators suggest a high level of natural recruitment. The spawning population was comprised of multiple ages, and the mean age of spawners (8.4 years for females, 7.9 years for males) was at least 1 year older than the age at 50% maturity (5.8 years). Estimated annual total mortality rates (0.20–0.25) and sea-lamprey induced mortality rates (0.02) were less than maximum allowable values. The proportion of wild-origin fish captured was high among spawners but varied among sampling programs (42% in fall trap nets, 70% in fall gill nets, and 88% in summer gill nets). A strong year class (1997) could be tracked from 2001 to 2005. Few fish were captured from early (< 1996) or later (1999–2002) year classes. Possible explanations for low natural recruitment during these later years include declining spawning habitat quality caused by low water levels and/or invasion of non-native mussels (Dreissena spp.) and/or direct or indirect effects of alewife (Alosa pseudoharengus).     

Trophic ecology of salmonine predators in northern Lake Huron with emphasis on Atlantic salmon (Salmo salar)

Pacific salmon were introduced to the Great Lakes in the 1960s and now support major recreational fishery. Population declines resulting from invasive species have prompted agencies to consider diversifying sport fisheries through stocking. Atlantic salmon are native to Lake Ontario, but a small fishery has developed in northern Lake Huron since the 1990s that appears suited to the Lake Huron food web leading to requests for increased stocking by anglers and consideration by agencies. However, no study has evaluated the trophic ecology of Atlantic salmon in relation to other salmonine predators in northern Lake Huron. In this study, we used stable isotopes of carbon (δ¹³C) and nitrogen (δ¹⁵N), along with mercury (Hg) concentrations to assess resource use, niche overlap, and contaminant accumulation in Atlantic salmon compared to select Lake Huron predators. Atlantic salmon exhibited considerable niche overlap with Chinook and coho salmon but were strongly differentiated from lake trout. In addition, we observed that Atlantic salmon had similar Hg concentrations as coho but were lower than both Chinook salmon and lake trout. Based upon the relationship between fish size, δ¹⁵N, and Hg, Atlantic salmon bioaccumulate Hg similarly to Pacific salmon but likely have lower consumptive demands than Chinook salmon. Continued attention should be placed on understanding how Atlantic salmon fit into the current Lake Huron food web in order to evaluate the long-term efficacy of the Atlantic salmon stocking program.