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To measure lipids in juvenile and adult fishes, we refined three microquantity approaches (microgravimetric, microcolorimetric sulfophosphovanillan (SPV), and Iatroscan thin layer chromatography--flame ionization detection (TLC-FID)) that were originally developed to measure lipids in small aquatic invertebrates. We also evaluated their precision and comparability by quantifying the total lipid content of age-1+ walleye (Sander vitreus), yellow perch (Perca flavescens), and lake whitefish (Coregonus clupeaformis) collected in Lake Erie (US-Canada), Lake Michigan (USA), and Muskegon Lake (Michigan, USA). Our findings demonstrate that (i) microquantity approaches provide estimates of total lipids in juvenile and adult fishes similar to those of more traditional macroquantity approaches, (ii) the microcolorimetric SPV and microgravimetric approaches produce near identical estimates of total lipid content, and (iii) the Iatroscan TLCFID approach underestimates total lipids relative to the other approaches for individuals with high lipid levels. Ultimately, our research makes available additional techniques for measuring total lipid content of fishes that are less expensive than traditional techniques, owing to a reduced need for large quantities of samples and solvents. Afin de doser les lipides dans les poissons juveniles et adultes, nous raffinons trois methodologies microquantitatives (microgravimetrie, microcolorimetrie a sulfophosphovanilline (SPV) et chromatographie sur couche mince Iatroscan couplee a un detecteur a ionisation de flamme (TLC-FID)) mises au point au depart pour mesurer les lipides dans de petits invertebres aquatiques. Nous avons evalue leur precision et les avons comparees entre elles en dosant le contenu en lipids totaux de dores (Sander vitreus), de perchaudes (Perca flavescens) et de grands coregones (Coregonus clupeaformis) d'age 1+ recoltes aux lacs E rie (E.-U.--Canada), Michigan (E.-U.) et Muskegon (Michigan, E.-U.). Nos observations demontrent que (i) les methodes microquantitatives fournissent des estimations des lipides totaux chez les poissons juveniles et adultes semblables a celles des methodologies macroquantitatives plus courantes, (ii) les methodologies microcolorimetriques SPV et microgravimetriques donnent des estimations presque identiques du contenu lipidique total et (iii) la methodologie TLC-FID Iatroscan sous-estime les lipides totaux par comparaison aux autres methodes chez les individus qui ont un fort contenu lipidique. En fin de compte, notre recherche rend disponibles de nouvelles techniques pour mesurer le contenu lipidique total chez les poissons, qui sont moins couteuses que les techniques habituelles, parce qu'elles requierent de moins grandes quantites d'echantillons et de solvants. [Traduit par la Redaction], Introduction Lipids are an integral component of aquatic animals, and their estimation can provide insight into growth strategies, health and condition, and survival potential of aquatic invertebrates and vertebrates alike [...]

Abstract: Benthic surveys were conducted in the southern basin of Lake Michigan and throughout the lake to assess trends in benthic populations, emphasizing recent changes in densities of the benthic [...]

Electron transport system activity (ETS) and respiration rates (R) of the zebra mussel, Dreissena polymorpha, were determined monthly from April to November over 2 years at two sites in Saginaw Bay, Lake Huron. The sites were located in the inner and outer bay and contrastedin food quantity and quality. ETS ranged from 2 to 40 Mug O2 mg DW-1 h-1 over the study period. Both ETSand respiration were strongly related to temperature, and maximum values were found between June and August. ETS also peaked in June/Julywhen assays were conducted at a constant temperature (25 deg. C), indicating other factors besides temperature affected metabolic activity. R:ETS ratios decreased with increased temperature at the inner bay site, but trends were minimal at the outer bay site. In late summer, blooms of the cyanophyte Microcystis occurred in the inner bay, likely depressing filtration rates, and leading to lower respiration rates relative to ETS. ETS activity was consistently higher in the outerbay and was likely a result of higher food quality. Despite these spatial differences, annual mean R:ETS ratios varied only from 0.04 to 0.09 at the two sites over the 2-year period. Based on these values, ETS may be useful as an indicator of long-term metabolic activity in annual energy budgets of D. polymorpha. However, food conditions differentially affect respiration relative to ETS, and variability in this ratio must be considered when interested in shorter time scales. [ABSTRACT FROM AUTHOR]

The amphipod, Diporeia spp., the dominant benthic macroinvertebrate in the Great Lakes offshore waters, has exhibited a substantial decline in recent years. This decline occurred after the invasion and colonization of the lakes by the zebra mussel, Dreissena polymorpha. It has been hypothesized that the decline is a direct result of the competition by the zebra mussel decreasing the amount of food available. This study examined the potential of other stressors, e.g., the presence of toxic materials, as the contributing or main cause of the decline. Bioassays were performed with sediments from stations currently devoid of Diporeia (St. Joseph, MI) and with those still having Diporeia populations. In 28-d mortality bioassays, no mortality was observed with any of the sediments tested. However, in avoidance/preference tests, sediments from St. Joseph, that are now devoid of Diporeia, were avoided compared to sediments from Saugatuck, Grand Haven, and Muskegon, which still have a population. This avoidance was not changed by the addition of either Spirulina Plus or Tetramin flakes to the sediment as a food source but was reversed by a fresh layer of the diatom, Fragillaria crotonensis, on the sediment. These studies suggest that despite the high carbon content of the St. Joseph sediment, the nutritional content of the sediment was limited. [ABSTRACT FROM AUTHOR]