Ageing methodologies of Lake Michigan alewife were evaluated as a precursor to growth and condition investigations of alewife stocks. Four commonly used aging tissues were evaluated including: otoliths, scales, vertebrae, and opercles. Otoliths were significantly more precise than other structures in all analyses. The accuracy of age determinations given by otoliths was corroborated through length frequency analysis. Total processing time was highest for scales. Whole otolith methodology was used to age alewives from Indiana, Michigan, and Wisconsin based on precision, accuracy, and time efficiency. A trend of higher median lengths and weights in young fish from the Green Bay, Wisconsin site was identified. Older fish grew faster in the main-lake sample sites near Pentwater, Michigan and Indiana waters. The Indiana population had the highest condition factor (K), while Wisconsin had the lowest, with Michigan in between. An overall temporal decline in condition of alewife was identified when compared with historical studies. This is a consideration that may influence salmonid stocking decisions because the alewife serves as their primary food. / Department of Biology

Nearshore larval fishes were collected with an oblique trawl tow during day and night from mid-May to August 2010 and 2011 in the Indiana waters of Lake Michigan to determine diel differences in the distribution, depth, and abundance of larval fishes. Alewife, spottail shiner, yellow perch and round goby were the prevailing larval species. Alewives dominated the catch and were in highest abundance near East Chicago. In general, night catch rates were greater when compared to day catch rates, suggesting a diurnal difference in trawl susceptibility. Stratified larval trawling was subsequently conducted during June and July 2011 to detect whether diurnal vertical migration existed, potentially affecting day and night catch rates. Vertical migration was not detected in the stratified larval sampling, eliminating it as a factor in higher nighttime catch rates. Further, the most common fish, alewife, was measured (TL) to determine whether size was a factor in trawl avoidance and to provide information regarding trawl selectivity. Night trawls yielded larger size classes of alewife, potentially explaining higher nighttime catch rates. These data suggests a size bias of our larval trawl exists when comparing day and night samples, as well as the limited efficiency of our trawl to catch larger larval size classes. / Department of Biology

We developed a mixed model to determine whether biotic (alewife, spottail shiner, round goby, yellow perch > age 1 and yellow perch < age 1 abundances) or abiotic (water temperature, water clarity) factors influenced growth rates in the Indiana waters of Lake Michigan during August from 1984 to 2007. This study suggests that young-of-the-year (YOY) yellow perch growth rates in southern Lake Michigan are influenced by temperature, spottail shiner abundance, and round goby abundance. We also collected age-0 yellow perch to identify details of early life history including timing of migration to pelagic waters, timing of return to nearshore waters, and spatial distribution following return to nearshore waters. This study suggests that yellow perch larvae hatch and are in the nearshore waters from June 1 to June 24, return date for demersal YOY yellow perch ranges from July 8 to August 16, with a mean return date of July 25, and spatial distribution of demersal age-0 yellow perch is relatively homogenous in Indiana nearshore waters. / Department of Biology

The goal of this study was to describe the benthic community and the food habits of the round goby Neogobius melanostomus, and to compare these food habits to the available prey observed in southeastern Lake Michigan. Nematodes and chironomid larvae were the most abundant organisms within the benthic samples, composing 22.4% and 17.2% of the total organisms collected respectively. Diet contents were identified, enumerated, and measured volumetrically. Copepods (35.7%) were the most abundant prey consumed, while chironomid larvae accounted for 30.5% of the total prey items. However, by volume, chironomid larvae composed 57.6% of the round goby diet, while zebra mussels Dreissena polymorpha composed 19.3%. The round goby were actively feeding on a variety organisms, but were selecting for certain prey. Diet and benthic community comparisons were also made with previous studies in the Great Lakes, which showed a difference in the dominant prey of the round goby as well as a decline in the abundance of zebra mussels in southeastern Lake Michigan. / Department of Biology

The relationship between yellow perch Perca flavescens abundance and growth rates were evaluated in the Indiana waters of Lake Michigan from 1984 to 2004. Relative abundance values were taken from trawl catch per unit effort (CPUE), while growth rates were determined by back-calculation. Abundance CPUE during the mid 1980's, was approximately one order of magnitude higher when compared to the 1990 to 2004 period. Growth rates were inversely related to relative abundance and were sexually dimorphic, with females growing faster than males. Regression analysis indicated approximately half of this observed variation in growth was due to abundance, and was most apparent with the smaller and younger fish. Both intraspecific competition and physiological changes associated with maturity are plausible explanations for the relationship. / Department of Biology

Snow and lake ice have very high albedos compared to other surfaces found in nature. Surface albedo is an important component of the surface energy budget especially when albedos are high since albedo governs how much shortwave radiation is absorbed or reflected at a surface. In particular, snow and lake ice albedos have been shown to affect the timing of lake ice break-up. Lakes are found throughout the Northern Hemisphere and lake ice has been shown to be sensitive to climatic variability. Therefore, the modelling of lake ice phenology, using lake ice models such as the Canadian Lake Ice Model (CLIMo), is important to the study of climatic variability in the Arctic and sub-Arctic regions and accurate snow and lake ice albedo measurements are required to ensure the accuracy of the simulations. However, snow and lake ice albedo can vary from day-to-day depending on factors such as air temperature, presence of impurities, age, and composition. Some factors are more difficult than others to model (e.g. presence of impurities). It would be more straight forward to just gather field measurements, but such measurements would be costly and lakes can be in remote locations and difficult to access. Instead, CLIMo contains an albedo parameterization scheme that models the evolution of snow and lake ice albedo in its simulations. However, parts of the albedo parameterization are based on sea-ice observations (which inherently have higher albedos due to brine inclusions) and the albedo parameterization does not take ice type (e.g. clear ice or snow ice) into account. Satellite remote sensing via the Moderate Resolution Imaging Spectroradiometer (MODIS) provides methods for retrieving albedo that may help enhance CLIMo’s albedo parameterization. CLIMo’s albedo parameterization as well the MODIS daily albedo products (MOD10A1 and MYD10A1) and 16-day product (MCD43A3) were evaluated against in situ albedo observations made over Malcolm Ramsay Lake near Churchill, Manitoba, during the winter of 2012. It was found that the snow albedo parameterization of CLIMo performs well when compared to average in situ observations, but the bare ice parameterization overestimated bare ice albedo observations. The MODIS albedo products compared well when evaluated against the in situ albedo observations and were able to capture changes in albedo throughout the study period. The MODIS albedo products were also compared against CLIMo’s melting ice parameterization, because the equipment had to be removed from the lake to prevent it from falling into the water during the melt season. Cloud cover interfered with the MODIS observations, but the comparison suggests that MODIS albedo products retrieved higher albedo values than the melting ice parameterization of CLIMo. The MODIS albedo products were then integrated directly into CLIMo in substitution of the albedo parameterization to see if they could enhance break-up date (ice off) simulations. MODIS albedo retrievals (MOD10A1, MYD10A1, and MCD43A3) were collected over Back Bay, Great Slave Lake (GSL) near Yellowknife, Northwest Territories, from 2000-2011. CLIMo was then run with and without the MODIS albedos integrated and compared against MODIS observed break-up dates. Simulations were also run under three difference snow cover scenarios (0%, 68%, and 100% snow cover). It was found that CLIMo without MODIS albedos performed better with the 0% snow cover scenario than with the MODIS albedos integrated in. Both simulations (with and without MODIS albedos) performed well with the snow cover scenarios. The MODIS albedo products slightly improved CLIMo break-up simulations when integrated up to a month in advance of actual lake ice break-up for Back Bay. With the MODIS albedo products integrated into CLIMo, break-up dates were simulated within 3-4 days of MODIS observed break-up. CLIMo without the MODIS albedos still performed very well simulating break-up within 4-5 days of MODIS observed break-up. It is uncertain whether this was a significant improvement or not with such a small study period and with the investigation being conducted at a single site (Back Bay). However, it has been found that CLIMo performs well with the original albedo parameterization and that MODIS albedos could potentially complement lake-wide break-up simulations in future studies.

名古屋大学年代測定総合研究センターシンポジウム報告

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The lake breeze is shown to develop on 30% of all summer days in the Toronto region, similar to other findings in the Great Lakes area. Simulations with the Colorado State University (CSU) model show that under northwest to north gradient flow the lake breeze is characterized by a broad band of westerlies over the lake, while southwesterly gradient flow produces a broad band of easterlies. A nocturnal mesoscale cyclonic eddy is predicted over western Lake Ontario under west and northwest gradient flow conditions. / A statistical model intercomparison of the CSU and Ontario Ministry of Environment models over a 19600 km$ sp2$ domain centred on Pickering, ON revealed the CSU model generally more accurately predicts the temporal and spatial lake breeze characteristics. This is attributed to improved model parameterizations and larger domain size enabling the model to resolve the full-lake scale circulations which develop.