. The Canadian field-naturalist. 1980 Jenkins and Jenkins: Greater Redhorse Reproductive Behavior 427 REDHORSE GROUPS, MALES MAIN CURRENTS UPSTREAM POINTS: UPPER LOWER ^ 0 20. Figure 1. Location of Greater Redhorse spawning sites at Fishdam Island. The house, boathouse, and dock spanning the two sections of the island are drawn slightly larger than the scale. Adult male M. valenciennesi congregated in the runs along the outer edges of the upstream points of the island. Spawning occurred by the upper point, and probably the lower, but few observations were made at either point. Redhorses were o
. The Canadian field-naturalist. 1980 Jenkins and Jenkins: Greater Redhorse Reproductive Behavior 427 REDHORSE GROUPS, MALES MAIN CURRENTS UPSTREAM POINTS: UPPER LOWER ^ 0 20. Figure 1. Location of Greater Redhorse spawning sites at Fishdam Island. The house, boathouse, and dock spanning the two sections of the island are drawn slightly larger than the scale. Adult male M. valenciennesi congregated in the runs along the outer edges of the upstream points of the island. Spawning occurred by the upper point, and probably the lower, but few observations were made at either point. Redhorses were often seen just above the house, where the current increased in speed en route to the boathouse, but they were generally swimming well above the bottom, and no spawning was witnessed there. Redhorses generally congregated and often spawned in the intra-island run. There was no evidence of spawning in the deeper, silty and rela- tively sluggish current of the coves. M. J. Bresnahan, a local resident, informed us that "redfin mullet" (probably M. valenciennesi) gather to spawn at numerous other sites of shallow, swift water over gravel and small rubble in the general area of our observations. Particular localities mentioned were Bensons Rift (between Hill and Rabbit islands), Ban- nisters Island (Island 91), and Anchor Island (Island 92). He also said they spawn near the town of Gana- noque, 14 km upstream from the Nidderies. Methods Our observations were made under usually excel- lent conditions for some 30 h during the 1967, 1968, and 1970 redhorse spawning runs, mostly near the end of each run. During some additional 40 h preceding or following redhorse runs, other fishes were observed at the island. The island was also checked for redhorse activity in 1974 and 1975, when it was under new ownership. The large size of, and our close proximity (1-7 m) to, M. valenciennesi usually permitted their study with unaided eyes. Polarizing sunglasses were used when needed to red
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