Samples from seven locations at depths to 21 m, collected over periods of up to 8 years, were used to describe the nearshore distribution and abundance of burbot Lota Iota and deepwater sculpin Myoxocephalus thompsoni larvae in Lake Michigan. Based upon power-plant-entrainment samples and field collections, burbot larvae (3.0-7.5 mm) occurred from late March to mid-June, most abundantly in April and May, and most often at water temperatures of 6-12 C. Larvae were collected from the 0.5-to 13.5-m depth strata as far lakeward as the 2 l-m bottom contour, the limit of offshore sampling. In eastern Lake Michigan, highest densities (up to 843 larvae/ 1,000 m a) were at the 1-m contour; in Green Bay, up to 24,000 larvae/l,000 m a were detected near the Bark River. High densities of burbot larvae at bottom depths 3 m and less indicated inshore spawning and river spawning at some sites. Deepwater sculpin larvae first occurred in early February and were common in March and April entrainment samples. Larvae (8.0-22.0 mm) were in nearshore waters usually through May at depth strata of 0.5 to 17 m as far lakeward as the 18-m bottom contour. Most larvae occurred at water temperatures below 6 C. Field densities were low, 5 to 78 larvae/l,000 m a. Deepwater sculpin larvae were pelagic and were dispersed over great distances by currents.

AND D. B. ROARABAUGH. 1981. Effectiveness of fine mesh cylindrical wedge-wire screens in reducing entrainment of Lake Michigan ichthyoplankton. Can. J. Fish. Aquat. Sci. 38: 120-125.Samples of ichthyoplankton entrained through 2 . 0 -m and 9.5-mm-slot opening cylindrical wedge-wire screens and through an open pipe (control) were collected in June, July, and August 1979, 1067 rn off the southeast shore of Lake Michigan at a depth of 10.7 m. Screens were designed for a Wow rate of 1.9 rn3 min-1 at 15.2 cm s-1 through slot velocity. Ambient camposition and density of ichthyoplankton wete determined by net tows. Rainbow smelt (Osmerus mordax), alewife ( A h a pseudoharengus), and yellow perch (Perca flavescensB larvae were common in both entrainment and tow collections. Eggs were found almost exclusively in entrainment collections. Ambient larval fish densities were about 11 times greater than those found in entrainment collections. Total entrainments through either screen and the open pipe were not statistically significant. Larval avoidance and, to a lesser extent, screen exclusion were responsible for the low entrainment. We estimated that about !XI?$ of native fish larvae at the site avoided pumping. . ROARABAUGH. 1881. Effectiveness of fine mesh cylindrical wedge-wire screens in reducing entrainment of Lake Michigan ichthyoplankton. Can. J. Fish. Aquat. Sci. 38: 120-125. Des echantillons d'ichtyoplancton entrain& h travers des krans cylindriques de fil mdtallique cunkiforme ii ouvertures en fentes de 2,Q I B I~ et 9'5 mrn et ii travers un conduit libse (temoin) ont 6t6 recueillis en juin, juillet et aoGt 1973, h 1067 m au large de la rive sud-est du lac Michigan, A une profondeur de 10'7 m. Les krans ont It6 conGus pour une vitesse d'koulement de 1,9 m3 min-I B une vitesse h travers les fentes de 15'2 crn s-I. Des prises au filet 2i plancton ont servi B ddterminer la composition et la densit6 ambiantes de l'ichtyoplancton. Les larves d'Cperlan arc-en-ciel (Osrnerns moniax), de gaspareau (Alsshi psesidoharengus) et de perckaude (Psrcn flrtvescens) sont communes dans l a collections h la fois par entrainement et par filet. On a trouvC des oeufs presque exclusivement dans Bes collections par entrainement. La densit6 des larves de poissons dans i'envirsnnernent est d'environ 11 fois supkrieure h celle trouvke dans ies collections par entrainement. Ii n'y a pas de difldrence significative d'entrainement total soit travers les ecrans, soit dans le conduit libre. L'dviternent par les larves et, 2i un degrd moatadre, l'exclusion par les Ccrans sont responsables du faible entrainement. Nous estimons qu'environ 90% des larves de poissons indigknes au site kvitent d'stre aspirCes par les pompes.

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