Todd A. Phillips

Feeding Frequency Effects on Water Quality and Growth of Walleye Fingerlings in Intensive Culture

Abstract Two experiments were conducted to determine the effects of feeding frequency on water quality and the growth of fingerling walleyes Stizostedion vitreum raised in intensive culture. Walleyes were fed 9 or 90 feedings/d for 63 d in experiment 1 (E1) and 3 or 30 feedings/d for 56 d in experiment 2 (E2). In both experiments, the means of daily measurements of dissolved oxygen were significantly higher and means of total ammonia nitrogen (NH3-N) were significantly lower in the treatment receiving the greater number of feedings per day. Final means of fish length and weight, coefficients of variability of length and weight, growth rates, and food conversions (feed fed/weight gained) did not differ significantly between feeding frequency treatments in either E1 or E2. The length-frequency distributions in both feeding trials were normal, and there were no significant differences in normality, kurtosis, or skewness between feeding frequencies. The results demonstrate that multiple feedings per day can b...

Effect of prairie grass on the dissipation, movement, and bioavailability of selected herbicides in prepared soil columns.

Phytoremediation of pesticide-contaminated sites using a prairie grass mixture (big bluestem, yellow indiangrass, and switch grass) has been suggested as a low-cost in situ remediation strategy. In this study, the proposed phytoremediation technique was applied to artificially prepared soil columns that were fortified with high concentrations of four herbicides (atrazine, alachlor, metolachlor, and pendimethalin). The fate and toxicity of the herbicides were compared with results from soil columns lacking vegetation. After either 150 or 240 d of phytoremediation, soils were watered with 7.5 cm of water, and leachate was collected. Columns were then divided into three sections (top, middle, bottom). For each section of the column, chemical analysis (ethyl acetate and water extractions), earthworm accumulation tests, and lettuce seedling growth tests were performed. The leachate was chemically analyzed and tested for chronic toxicity to algae. Atrazine and alachlor degraded rapidly in the column, and the total amount recoverable was less than 2% of applied. After 250 d, vegetation reduced the total recoverable amounts of metolachlor and pendimethalin by 78 and 39%, respectively. Metolachlor was the only compound found in leachate, and the amounts recovered were reduced 5- to 20-fold by vegetation. Vegetation decreased the bioavailability of pendimethalin as measured by 8-d, earthworm bioaccumulation factors (BAFs) and lettuce seedling growth assays. Decreases in mobility and bioavailability indicate that this technique may stabilize pesticide residues in addition to increasing dissipation rates.

Gill Development of Larval Walleyes

Abstract We describe the development of gill filaments and secondary lamellae of larval walleyes Stizostedion vitreum from hatching to 21 d posthatch. The number of gill filaments was counted on the second gill arch of 20 fish at 7, 14, and 21 d posthatch and on the gill arch of 5 fish on all other days. The length of gill filaments and number of secondary lamellae per gill filament were determined for the first, third, fifth, and seventh gill filaments on the most ventral part of the gill arch. Gill filaments were first observed at 3 d posthatch (47 temperature units, TU, °C), and the first secondary lamellae were observed at 10 d posthatch (163 TU). Results indicated strong positive relationships between cumulative temperature units posthatch and number of gill filaments, length of gill filaments, and number of secondary lamellae per gill filament. There were strong positive relationships between total length of the fish and number of gill filaments, between total length of the fish and length of gill f...