Triadimefon is a widely used triazole fungicide with one chiral carbon center. In soils, plants, and animals, triadimefon could be metabolized to triadimenol by reduction of the carbonyl group to an alcohol, resulting in the occurrence of a second chiral carbon in triadimenol. The enantioselective degradation of triadimefon and its chiral transformation to triadimenol in two soils, a Baoding alkaline yellow soil and a Wuhan acidic red soil, were investigated. The results showed the occurrence of enantioselectivity with R-(-)-triadimefon preferentially degraded in both soils. Abiotic racemization was observed by incubation of enantiopure triadimefon enantiomers. The racemization was clearly pH dependent and took place much more rapidly in Baoding alkaline soil than in Wuhan acidic soil. Further enantioselective analysis of converted triadimenol showed that triadimenol stereoisomer concentration invariably followed the order 1R,2R>1S,2S>1S,2R>1R,2S in Baoding soil, regardless of racemic triadimefon or single enantiomers initially treated. However, in the case of Wuhan soil, different triadimenol stereoisomer patterns could be produced depending on initial triadimefon composition at the time of application. The abiotic racemization was documented to have a great influence on the chiral profiles of triadimefon and its metabolite triadimenol. The mechanism and structural consideration of the racemization were further discussed, underscoring the importance of considering configurational stability in proper evaluation of environmental fate and risk of chiral pesticides.

Data from Minnesota Department of Natural Resources lake surveys and stocking records were used to examine the effects of stocking programs involving walleye Stizostedion vitreum on the abundance and size of fish in walleye populations and to determine to what extent and under what conditions these effects occurred. We used data from 4,470 surveys in 1,924 lakes and from 20,634 walleye stocking records in 1,716 lakes. The analyses were conducted for various sizes of stocked fish and stocking frequencies and for lake groups with different walleye reproductive status. We reached the following conclusions. (1) Stocking in lakes without natural walleye reproduction increased walleye population abundance, but stocking in lakes where reproduction occurred had no effect on population abundance, (2) In lakes without walleye reproduction, walleye mean weight was reduced by stocking. In lakes with walleye reproduction, fry stocking decreased the mean weight of fish, but fingerling stocking had no effect on weight. The decrease in weight resulting from stocking was greater in lakes without natural walleye reproduction than in lakes with natural reproduction. (3) In situations where stocking affected population abundance or fish size, an increase in stocking frequency had diminishing effects. In general, where total population abundance increased as a result of stocking, the walleye mean weight decreased.

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The success of stocking programs involving walleye Stizostedion vitreum has frequently been judged by the contributions of the stocked walleye to the abundance of year‐classes. But evaluation methods based only on contributions to the year‐class augmented may be biased. We developed a method of estimating walleye year‐class strength based on catch‐at‐age data from routine fish population assessments. We then examined the effect of walleye stocking on the stocked year‐class and other year‐classes by using catch‐at‐age data from walleyes in 200 Minnesota lakes. Although stocking increased the abundance of a year‐class in lakes with natural walleye reproduction, stocking, especially of fingerlings, decreased the abundance of year‐classes 1 year younger and 1 year older than the stocked year‐class. In lakes without natural walleye reproduction, stocking did not affect adjacent year‐classes significantly.