Hypoxia, low dissolved oxygen (DO) concentrations (<2 mg/L), has been a major issue in Lake Erie for decades. While much emphasis has been placed on biological factors, particularly algal blooms, contributing to hypolimnetic oxygen depletion, there has been little focus on the role of weather. For this study, we monitored water temperature and DO concentrations at sites in the western, central, and Sandusky basins in Lake Erie during June and July 2010–2012. We then compared trends in stratification and DO concentrations to weather patterns during that period. We found that during those three years, there was significant variation in weather patterns, particularly decreased ice coverage and increased storm events in 2012. These weather patterns corresponded to 2012 having the warmest water temperatures, some of the lowest DO concentrations, and a deeper and thinner hypolimnion (especially in the central basin) than the previous years. We found a relationship between weather and hypoxia, providing further evidence for why these basins are susceptible to low DO conditions during summer months. The role of weather in hypoxia is another indication that the lake is vulnerable to effects of climate change and should be considered in management strategies.

Sedimentological and geochemical results from Nir’pa Co, an alpine lake on the southeastern Tibetan Plateau, detail late-Holocene Indian summer monsoon (ISM) hydroclimate during the last 3300 years. Constrained by modern calibration, elevated silt and lithics and low sand and clay between 3.3 and 2.4 ka and 1.3 ka and the present indicate two pluvial phases with lake levels near their current overflow elevation. Between 2.4 and 1.3 ka, a sharp increase in sand and corresponding decrease in lithics and silt suggest drier conditions and lower lake levels at Nir’pa Co. Hydroclimate expressions in the sedimentological proxies during the Medieval Climate Anomaly (MCA) and ‘Little Ice Age’ (LIA) are not statistically significant, suggesting that these events were minor compared to the millennial scale variability on which they were superimposed. However, decreasing sand and increasing lithics and silt during the MCA between 950 and 800 cal. yr BP may suggest briefly wetter conditions, while increasing sand and reduced lithics and silt from 500 to 200 cal. yr BP suggest potentially drier conditions during the LIA. Similarities with regional records from lake sediment and ice cores and speleothem records from the central and eastern Tibetan Plateau, India, and the Arabian Sea, suggest generally coherent late-Holocene ISM variability in these regions. Increased late-Holocene ISM intensity occurred during times when Tibetan Plateau surface air temperatures were warmer, Indo-Pacific sea surface temperatures were elevated, and the tropical Pacific was in a La Niña–like mean state. Conversely, aridity between 2.4 and 1.3 ka occurred in concert with cooling on the Tibetan Plateau and in the Indo-Pacific with more El Niño–like conditions in the tropical Pacific. Differences with western Tibetan records may reflect a weakened ISM and stronger westerlies in this region during the late-Holocene.

The round goby, Neogobius melanostomus, is an invasive benthic fish species in the Laurentian Great Lakes that is threatening native fish populations through competition, predation, and trophic dynamic change. This study examined the trophic dynamic plasticity of round goby along a depth gradient based on laboratory and field observations to determine prey species consumed and mussel prey size selection. Prey size selection in the laboratory was assessed by presenting individual round goby with quagga mussels (Dreissena rostriformis bugensis) of various class sizes (i.e., 6.0-9.9 mm, 10.0-12.9 mm, 13.0-15.9 mm, and 16.0-18.9 mm in length). Round goby exhibited a selection preference for small sized quagga mussels, although in individual trial events, mussels were consumed from all four size classes. Prey species consumed from shallow and deep sites in the western basin of Lake Erie were assessed using individual gut contents to calculate measures of prey importance, diversity, and dominance. Based on the Index of Relative Importance (IRI), Cladocera was found to be the most consumed prey item for both males and females and between study sites. Both sexes consumed a variety of prey items although females exhibited greater prey dominance or reliance on one prey item. Round goby individuals at the shallow, natural shoreline site had the highest trophic diversity, while individuals at the deep site exhibited the highest prey dominance. Diet of round goby in the western basin of Lake Erie are mainly dominated by just a few prey items.

Gender relationships between total and standard length (mm) were compared to weight (mg) in the mimic shiner, Notropis volucellus for the western Lake Erie basin in the vicinity of the Bass Islands. Length and weight relationship (n=300), length-frequency distribution, and sex ratios (n=884) from a single date from Gibraltar Island in June 2012 were analyzed for coastal shoreline and tributaries. A strong positive correlation was found between length and weight for both males and females. In females, a significant positive correlation exists between standard length (SL) and body weight (F=671.5, d.f.=135) and between total length (TL) and body weight (F=681.4, d.f.=135). In males, there was also a strong positive correlation between SL and body weight (F=1744.9, d.f.=160) and between TL and body weight (F=1656.6, d.f.=160). Combining data for the two sexes helped determine a strong relationship between SL and body weight (F=1908.3, d.f.=299) and between TL and body weight (F=1885.9, d.f.=299) that was consistent with the results from the individual sexes. The growth patterns of male and female mimic shiner differed significantly for both SL (F=0.76, p>0.05, d.f.=159-134) and TL (F=0.76, p>0.05, d.f.=159-134). Age I females ranged from 29–51 mm TL and Age I males ranged from 30–46 mm TL based on 884 individuals from Gibraltar Island. Age II females ranged from 57–61 mm TL and Age II males ranged from 54–56 mm TL. Mimic shiner exhibit indeterminate growth and gender influences growth patterns. Date of Publication: 5 August 2013 OHIO J SCI 112 (2): 44-50 1Address correspondence to Thomas P. Simon, 2364 E. linden Hill Drive, Bloomington, IN 47401. Email: tsimon@indiana. edu. Wayne Co., Michigan, in 1865 (Cope 1864). Mimic shiner are usually found in streams and rivers, but can also be found in lakes (Trautman 1982; Whittier and others 2000). Their indigenous range spans from the Atlantic Coast to the Great lakes to the Gulf of Mexico, but in recent years they have been introduced to new waterways, such as the Connecticut River, as a result of human activities (Schmidt and Jacobs 2005). Mimic shiner are active insectivores found mostly in the benthic areas of the littoral zone (olmstead and others 1979). Greeley (1929) and Van Meter and Trautman (1970) reported the species as abundant and an important forage species around the islands in lake Erie. Despite the former abundance of mimic shiner in the lake Erie basin, recent estimates suggest that its abundance is declining (ohio DNR 2012). This study investigated the relationship between length and weight in mimic shiner to better understand growth patterns based on gender as it pertains to their life history. In addition, the sex ratio and length frequency distribution was evaluated to predict age structure. Both length-weight relationships and age structure determinations are useful in comparing different populations and determining ecological impacts of this species. lake Erie individuals collected from both coastal shoreline and tributary habitats within the western basin were studied to Cyprinidae are the most abundant and diverse group of freshwater fishes in North America with over 200 species; however, other than taxonomic resolution, limited basic life history information exists for many species (Whittier and others 2000). In North American lakes and rivers, minnows are an important link in the aquatic trophic web (Stewart and Watkinson 2004), yet the difficulty in identification of these small species and their relatively little economic value have made minnows an under-studied group (Whittier and others 2000). Johnson (2009) indicated that minnows are becoming an important constituent of walleye diet in lake Erie, in addition to clupeids and rainbow smelt. To better assess the ecological role of minnows in assimilation of lower trophic levels, a better understanding of the life history, growth, and age structure of these fishes is needed. length-weight relationships are an important aspect of the life-history of a fish, as they can indicate a relationship between growth and maturity. The mimic shiner, Notropis volucellus (Cope 1864) was first described in the Detroit River near Grosse Isle, INTRODUCTION oHIo JouRNAl of SCIENCE 45 S. MIDDlEToN AND oTHERS evaluate length and weight. The aim of the study was to determine whether mimic shiner exhibits indeterminate growth and specifically what correlation exists between two measures of length (i.e., total length [Tl] and standard length [Sl]) and weight based on gender. This information could be used to assess the health and feeding structure of different mimic shiner populations. The study also determined whether mimic shiner growth patterns are influenced by sex, and hypothesized that a difference in growth would occur between males and females. Differences in growth were assessed to find whether there was a significant difference between mimic shiner populations in the western basin associated with lake Erie and its tributary rivers. finally, the growth ranges and age structure of individuals from the Bass Islands were compared to other populations in the Great lakes region. MaTERIaLS aND METHODS