Little is known about the dispersal of Shortnose Sturgeon Acipenser brevirostrum larvae in the wild. In the Saint John River, New Brunswick, we captured a total of 2,251, 460, 2,100, and 2,083 larvae in 2008–2011, respectively; abundance estimates ranged between 21,000 (2009) and 244,687 larvae (2008). A substantial reduction in larval numbers (49–76%) was recorded over the 4.5‐km distance between the two sampling transects deployed in 2008–2010. We found no consistent pattern of larval distribution across the channel, but we recorded a consistent, significant preference for nighttime (dusk to dawn) over daytime dispersal. Generalized linear models were used to examine the timing and extent of larval migration in the Saint John River during the study period. Logistic models incorporating water temperature and Mactaquac Dam discharge provided good predictions of the timing of larval migration. The probability of larval presence was highest when water temperature reached 15°C. At this temperature, larvae were predicted to disperse when nighttime total dam discharge was 20 106 to 30 106 m3. The extent of larval migration was described using negative binomial models, which indicated that dam discharge and transect location significantly influenced the number of drifting larvae. However, data variability was high, reducing predictive capability. Our findings include the first report of Shortnose Sturgeon larval abundances in the Saint John River. The predictions of timing and extent of drift provide information for future sampling and conservation efforts during this vulnerable period as well as insight into the relationships between environmental variables and larval drift in this protected species.

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Timing of spawning and hatching of shortnose sturgeon, Acipenser brevirostrum , in the Saint John River, New Brunswick, Canada, was estimated using inverse prediction. We examined egg incubation periods at 5, 9, and 13 °C to back-calculate spawning dates. No larvae hatched at 5 °C. At 9 and 13 °C, hatching began after 18 and 8 days post fertilization, respectively. Lengths of yolk-sac larvae reared in the laboratory at 13–21 °C were used to develop a temperature-mediated Gompertz growth model. The inverted Gompertz model, predicting larval age from larval size and water temperature, was applied to 671, 164, and 746 larvae captured in the wild in 2008, 2009, and 2010, respectively. Estimated hatching distributions peaked in late May, and mean spawning events were predicted to occur in late April – early May (9 °C scenario) and middle to late May (13 °C scenario). Larval ages at the two sampling transects, 4.5 km apart, were similar, while catch per unit effort was lower downstream, indicating mortality during dispersal. Inverse prediction of larval ages provides fast and cost-effective estimates of the timing of spawning, hatching, and larval migration in the wild.

Monitoring of 10 and 12 commercial potato, Solanum tuberosum L., fields in 2004 and 2005, respectively, confirmed for a low-density population of Colorado potato beetle, Leptinotarsa decemlineata (Say), that potato fields nearest to the previous year's potato fields are significantly more colonized by this beetle than more distant fields. This pattern is partially explained by the presence of a reservoir of colonizers estimated at 35% of the season-long colonizing population in 2004 and 2005. These beetles, which emerged before potato plants broke the ground, were ready to establish themselves on nearby potato plants. The colonizing Colorado potato beetles dispersed within the maximum range of 1.5 km over a season, and the colonization risk for the new crop decreased with distance from the previous year's crop. There was no evidence that rotation distance delayed colonization. In terms of pest management, although the findings confirm that only long 1.5-km rotations can prevent Colorado potato beetle colonization, they also demonstrate that short rotations of 100 m or more can make substantial contributions to pest management programs for low-density beetle populations.