Recent interest in the restoration of lake sturgeon Acipenser fulvescens and in the development of new culture techniques has led to many new management programs designed to stabilize and enhance existing wild populations. The spread of pathogens affecting both wild and propagated sturgeon is a major concern for restoration programs. In 1999, two methods of egg de‐adhesion were used on two separate groups of lake sturgeon eggs prior to disinfection with 100 mg/L of iodine for 10 min. The de‐adhesion of eggs with urea−NaCl–tannic acid solutions produced hatch and 14‐d‐posthatch survival rates of 77.2% and 71.0%, respectively. These results were compared with those for eggs treated with Fuller's Earth (control), which had survival rates of 88.0% and 86.0%, respectively, at hatch and 14 d. In 2000, we compared three methods of de‐adhesion: (1) a solution of distilled water (jelly inhibitor) and iodine, (2) a solution of urea, NaCl, and tannic acid, and (3) a solution of Fuller's Earth and iodine. With all three methods, eggs were disinfected with a 50‐mg/L buffered iodine solution for 30 min during or immediately following de‐adhesion. Survival to hatchout for the distilled water, urea−NaCl−tannic acid, and Fuller's Earth methods was 95.3, 99.6, and 97.7%, respectively. Survival to 14 d posthatch was 76.8, 84.2, and 85.6%, respectively, for the three methods. Iodine disinfection during the de‐adhesion and water absorption processes does not appear to be toxic to lake sturgeon eggs. Topical iodine disinfection of lake sturgeon eggs immediately (<10 min) following fertilization increased the exposure of both the internal and external portions of the egg to the iodine during the hydration of the egg envelope.

We developed an index of egg and larval maturation for Lake Sturgeon Acipenser fulvescens to incrementally chart development over time. To evaluate the relationship between temperature and development rate, eggs and larvae from the Wolf River were incubated at four constant water temperatures. The time required for neural tube closure, hatch, and exogenous feeding were monitored. The number of hours from incubation to each development stage and mean water temperature were related by predictive exponential regression equations for neural tube closure (R2 = 0.96), start hatch (R2 = 0.97), end hatch (R2 = 0.97), and exogenous feeding (R2 = 0.99). Calculated hourly development was used to create an index capable of predicting specific daily development. Daily development from incubation to exogenous feeding ranged from 2.0% to 8.3% at 10°C to 19.9°C. This index was used to predict the rate of development of sturgeon eggs and larvae from the St. Lawrence River reared in water with varying temperatures. All development stages occurred within 24 h of the time predicted by the index. This index may be used to accurately predict and manipulate the progress of development and assist with the culture and management of Lake Sturgeon populations.

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The authors would like to thank the staff of the Genoa National Fish Hatchery for the many hours dedicated to propagating the seven species of mussels and for their expert advice, which was integral to the study design and execution. The Wisconsin Department of Natural Resources assisted in the permitting required for the study, and the La Crosse Regional Airport (La Crosse, Wisconsin) allowed us to conduct study operations on their property. The authors thank Mr. Hugh McMath (USGS), who assisted in study conduct as well as data and sample collection. We also thank Mr. Mark Gaikowski (USGS) for his assistance in study design and data analysis.

This study evaluated the relationship between temperature and growth rate of juvenile Lake Sturgeon Acipenser fulvescens and determined optimal temperature for growth based on weight gain and length increase. Four temperature regimes (12.0 ± 0.5, 17.0 ± 0.3, 21.6 ± 0.4, and 26.8 ± 0.6°C [mean ± SD]) were tested in triplicate to determine specific growth rates and daily length increases. In addition to growth rate, consumption rates were also assessed by recording the grams of feed offered to fish and the amount uneaten to ensure all fish were fed to satiation. Lake Sturgeon consumed 2.76, 9.63, 13.69, and 14.22% body weight/d, respectively, and grew at a specific growth rate of 0.50, 1.42, 2.01, and 1.75 mm/d, respectively. Fish consumed more food with increasing water temperature; however, daily length increase declined at 26.8°C. This study may be used to construct growth models for production programs, project size at stocking, and project feed rates based on water temperature.