Selection of Artificial Spawning Sites by the Spotfin Shiner (Notropis spilopterus)

Abstract

In 1975 experiments were conducted in the Susquehanna River, near Berwick, Pennsylvania, to investigate spawning-site selection of the spotfin shiner (Notropis spilopterus), a crevice spawner. Results of experiment A revealed that visual cues and water currents were important in spawning-site selection. Spotfins deposited 43.638 eggs on black discs and only 2 eggs on clear discs; 87% of the eggs were in horizontal crevices and the remainder in vertical crevices paralleling (7%) and perpendicular (6%) to the current. Fish spawned over the entire disc in slow currents but avoided strong currents (0.57 m/s) by spawning on the downstream side of the discs. Nearly 90% of the eggs were deposited in crevices 1.5 and 3.0 mm wide, the two smallest sizes. In angular crevices 15–90° from horizontal, fish deposited 74% of 8,358 eggs in the 15° crevice and 24% in the 30° crevice.In experiment B, a stack of black acrylic plates was placed near the river surface, at midwater, and near the bottom; in July fish deposited 91% of 13.088 eggs in the bottom stack. By mid-August stack usage had changed and 80% of 11,456 eggs were in the surface stack; the others were in the midwater stack. Rate of egg deposition on acrylic plates between July 10 and August 20 peaked in early August.In experiment C, 95% of 46,328 eggs were placed in crevices between blue (55%) and black (40%) plates; other colors were green (4%), red (1%), and white, yellow, and orange (< 1%). Fish usually spawned on the plates between 0600 and 1000; spawning did not occur at night.The spotfin has potential as a bioassay organism because of its wide distribution, the ease with which large numbers of its eggs can be collected, its extended breeding season, and the simplicity of rearing the young.