Cayuga Inlet Fishway (2011)
Operation of the Cayuga Inlet fishway continued in spring 2011. A total of 196 rainbow trout were handled which was lower than the numbers handled during the past few years. The unusually high water levels present in 2011 may have enabled an unusually large portion of the migrating rainbows to jump over the fishway dam, thus reducing the portion collected at the fishway. Thirty-two percent of the rainbow trout handled at the fishway had a hatchery fin-clip. After handling, the rainbows were either released upstream or held for egg collection.
Annual rainbow trout propagation efforts continued with the collection of 153,530 wild and 24,630 hybrid rainbow trout eggs. After collection, the eggs were transported to the Bath Fish Hatchery for hatching and rearing. Approximately 70 female and 50 male rainbows were used for the egg collection. These fish were released upstream after the egg collection, with the exception of 25 rainbows sacrificed for fish health inspections at the Rome Laboratory. Dr. George Ketola, with the U S Geological Survey in Cortland, collected eggs for his ongoing thiamine deficiency research.
Other fish handled
Also handled were 3,777 white suckers and 802 adult sea lampreys on their spawning runs. The suckers were released upstream while the lampreys were killed to prevent them from spawning upstream.
Sea lamprey control evaluation
All rainbow trout handled at the fishway were examined for the presence of sea lamprey wounds. Only five wounds (adult stages I-III) were observed on the 196 rainbow trout examined. No wounds were observed on the 18 rainbow trout in a 500-549 mm (19.7-21.6 inch) index group. The incidence of wounding on these fish was considered low and was indicative of a small adult lamprey population in relation to the combined populations of host species (e.g., lake trout, rainbow trout, brown trout and landlocked salmon).
The figure below shows lamprey wounding rates on the 500-549 mm index group of rainbow trout handled at the fishway since 1980. The dramatic decline in wounding rates shown in this figure was in part the result of the first lampricide treatment in Cayuga Inlet in 1986. This treatment was necessary to kill an excessively large number of juvenile sea lampreys produced during several high water years when large numbers adult lampreys from Cayuga Lake escaped over the fishway dam and spawned upstream. A second lampricide treatment in 1996 was conducted for the same reason. Since 1996, the extent of adult lamprey escapement, spawning and juvenile lamprey production has not been large enough to necessitate another lampricide treatment.
The figure below also shows a lamprey wounding threshold rate of 0.27 wounds/rainbow trout in the 500-549 mm index group handled at the fishway. This threshold rate was developed by Bishop and Chiotti (1996) who found that maintaining a level of lamprey control that kept wounding rates below the threshold rate was conducive to the satisfactory survival and growth of Cayuga Lake salmonids. The figure below clearly shows that lamprey control efforts (e.g., blocking the spawning run at the fishway and lampricide treatments) have kept lamprey wounding rates below the threshold rate.
Brief high water periods in 2007 and 2011 allowed limited numbers of adult lampreys from Cayuga Lake to escape over the fishway dam and spawn upstream in Cayuga Inlet. Preliminary results of recent electrofishing surveys in the Inlet indicate the numbers of juvenile lampreys produced in 2007 and 2011 were likely not large enough to require a lampricide treatment. Electrofishing surveys in Cayuga Inlet will continue in an effort to monitor the distribution and growth of juvenile lampreys produced in 2007 and 2011 and others that may follow.
Bishop, D. L. and T. L. Chiotti. 1996. Evaluation of the Experimental Sea Lamprey Control Program in Cayuga Lake, New York, Final Report. New York State Department of Environmental Conservation, Cortland, New York. 65 pp.