Red shiners Notropis lutrensis (weight, about 1 g each) from the selenium‐affected areas of Belews Lake, North Carolina, a cooling reservoir for an electric power plant, were fed to striped bass Morone saxatilis (about 250 g each) in a laboratory experiment. Consumption of red shiners (whole‐body selenium concentration, 9.6 μg Se/g wet weight) by striped bass was followed by modified behavior, little increase in weight, a reduced condition factor (105·weight/length3), an elevated selenium concentration in muscle (3.8 ug Se/g wet weight), histological damage to the liver and trunk kidney, and the death of all fish within 78 d. Striped bass fed a comparable, uncontaminated diet of golden shiners Notemigonus crysoleucas (about 1 g each) gained weight, increased their condition factor, had muscle selenium concentrations averaging 1.1 μg Se/g wet weight, and exhibited no histological abnormalities or reduced survival during the 80‐d experiment. Toxicity and death induced by selenium‐contaminated prey fish may contribute to the absence of piscivorous game fish in selenium‐affected regions of Belews Lake.

The morphological development of the gill apparatus in 11- to 180-day old smallmouth bass (Micropterus dolomieui) is described as seen by scanning electron microscopy. Filament protrusions without lamellae developed on the midregion of the gill arches in yolk-sac fry. Filament development progressed from the midregion of the gill arch toward the insertions. Secondary lamellae were first observed 15 days after egg fertilization when the fry became free swimming. Lamellae first appeared on filaments proximal to the gill arch and advanced distally. Proliferation of filaments and lamellae continued through at least the first 90 days of life. Filaments on the medial hemibranch of a holobranch were longer than those on the lateral hemibranch for at least the first 90 days. Filaments were alternately arranged between two hemibranchs of a holobranch. Substantial differences existed between gill developmental stage at hatching in smallmouth bass and that previously reported for salmonids. The dynamic nature of the developing gill indicated that quantitative descriptions of filament length, lamellar number and area, and total gill surface area requires examination of specimens at numerous different ages. This is the first morphological description of developing gills in a teleost fish based on observations by scanning electron microscopy.

This study assessed the feasibility of three sonar technologies to estimate eel abundance, determine distribution, and describe approach behavior to advance strategies for providing safe downstream passage of out-migrating American Eels at hydroelectric facilities on the St. Lawrence River. A Simrad EK60 split-beam echosounder (120 kHz), Sound Metrics ARIS Explorer multibeam sonar (1100/1800 kHz), and Mesotech M3 multi-mode multibeam sonar (500 kHz) were deployed at Iroquois Dam for experimentally testing their capabilities in detecting and identifying known numbers and sizes of live adult eels tethered to surface floats released upstream of the sonar beams and allowed to swim through at known locations and times. In addition, sonars collected data continuously to monitor wild, out-migrating eels during July 15-22 and September 17-19, 2015. Results highlight several challenges in acoustically monitoring eels in a large, fast-moving river with a few orders of magnitude higher abundance of other targets that can lead to a high false positive error rate. The ARIS multibeam sonar, operating with 48 beams, holds the most promise for correctly identifying eels out to 16-20 m in range, but the M3 multibeam sonar has some value for tracking previously identified targets over larger areas.

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