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Adrian, D. J., T. A. Ferro, H. T. Keppner, 1994. Annual and Seasonal Variations in Veliger Density in the Upper Niagara River. AquaTech Environmental, Inc. Proceedings of The Fourth International Zebra Mussel Conference, Madison, Wisconsin, March 1994 Annual and Seasonal Variations in Veliger Density in the Upper Niagara RiverAbstract Generally, veliger density fluctuated in magnitude and spawning duration throughout the three year period. For this analysis, spawning season is defined to be when veliger density exceeded 5,000/m3. Spawning season occurred early in 1991 and was brief, starting in July and concluding in early September. The 1991 season was characterized by relatively high densities occurring over a short period of time. The spawning seasons in 1992 and 1993 were much longer than 1991. In 1992, spawning was observed by mid-July and concluded in November. Two peaks of 20,000/m3 were observed, one in August, the other in September 1992. Between December 1992 and March 1993, viable veligers were observed from the water column where temperature was less than 0.50C. The spawning season of 1993 did not occur until September. The season was characterized by moderate to high densities with a single high peak density of 57,000/m3. The 1993 spawning season was relatively late in the year compared to the 1992 and 1991 seasons. This paper will incorporate the three year data set and will summarize inter annual variations of veliger density in the upper Niagara River. Other environmental parameters such as water temperature and storm events, were monitored and will be included in the summary. Entire Paper |