. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. BEHAVIOR OF WEAKLY ELECTRIC FISHKS 201 prised the river bottom. An area near the right bank was studied most inten- sively. Varying sized spotches in Figure 1 appearing to be bushes growing along the right bank of the river were in fact large and small trees standing in water 6 m deep. River depth near the ship was determined with a portable Bendix echo sounder. By local report, the river undergoes a depth change of about 6 m an- nually, and much of the study area was usually above water during the dry season. During the stu
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. BEHAVIOR OF WEAKLY ELECTRIC FISHKS 201 prised the river bottom. An area near the right bank was studied most inten- sively. Varying sized spotches in Figure 1 appearing to be bushes growing along the right bank of the river were in fact large and small trees standing in water 6 m deep. River depth near the ship was determined with a portable Bendix echo sounder. By local report, the river undergoes a depth change of about 6 m an- nually, and much of the study area was usually above water during the dry season. During the study, 4 April to 15 May 1967, the river was approaching flood stage, and the forest surrounding the base camp on the island was covered with water. • * * ** **"•" •••••>•/.--'. •*; /. •• *st%&j?£& %&&%& O '. FIGURE 1. Sketch map of the study area; "helix" denotes the R/V ALPHA HELIX anchored off an island on the right bank of the Rio Negro. The large and small splotches denote large and small submerged trees. Dry areas are shown by solid and dashed lines around the camp area. Heavily dashed arrows indicate continuations of the submerged trees and the island proper. The lightly dotted lines indicate approximate depth contours in meters. The large solid arrows (1-4) denote trawling locations. The thin lines mark locations where transects of activity were made. The boxed letters A and B show the location of marking buoys. Mag- netic north and a scale of distance are noted. METHODS Electrical activity from fishes was detected by recording between two carbon electrodes fixed m apart attached to a 26 m coaxial cable marked in 1 m grada- tions. Signals were amplified by a miniature transistor pre-amplifier and earphone (called "fish detector" henceforth) or recorded on magnetic tape with a Sony portable recorder. To obtain transects of activity wrjwj position, these electrodes were dragged slowly behind
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
