R. Weldon Larimore

Destruction and Re-establishment of Stream Fish and Invertebrates Affected by Drought

Abstract In 1953 and 1954 a severe drought virtually destroyed the fish and invertebrate populations in Smiths Branch, a small warm-water stream in Vermilion County, Illinois, and presented an opportunity to study the adaptations, survival, and repopulation of aquatic organisms exposed to the critical conditions associated with low water levels. The fish population in Smiths Branch was first studied in 1951. In the fall of 1953, the flow was discontinuous, most of the pools dried up, and the few remaining pools were treated with rotenone to eliminate the surviving fish. After that time, the fish population was studied through the use of an electric seine, minnow seine, rotenone, and night observation. The invertebrate population was studied in a series of bottom samples. Discontinuous flow reduced the aquatic habitat and exposed the fish and invertebrates to desiccation, stagnation, and predation. Stagnation was most detrimental during early fall months, in association with leaf accumulations and drastic ...

Establishment of Invertebrate Communities on Log Substrates in the Kaskaskia River, Illinois

Development of invertebrate communities on log substrates was investigated in three habitats. In slowly moving, shallow water, standing crops (weights) of colonizing invertebrates followed a sigmoid growth curve during a 6—week exposure period. Initial colonization was rapid, followed by 2 weeks of slow growth, a rapid increase during the next 2 weeks, and then a leveling off at 1,650 mg/m2 during the final week. Numbers followed a similar pattern of growth, attaining a high of approximately 100,000/m2 by the end of the 5th week. Chironomid larvae colonized first and in the greatest numbers, followed sequentially be sessile rotifers and oligochaetes. These three organisms had the greatest influence on standing crops and total numbers. In a riffle, colonization was also rapid: 569 mg and 8,830 individuals per m2 at the end of four weeks . The riffle community was dominated by Taeniopteryx nivalis, hydropsychid larvae, chironomid larvae, and simuliid larvae. In a pool, the standing crop was largest on logs at an intermediate depth, next largest near the surface, and smallest near the bottom. The oligochaete, Aeolosoma sp., attained their largest population on logs at the greatest depth, chironomid larvae and taeniopterygid naiads attained their largest population at or above the intermediate depth. Communities on naturally occurring logs contained more planaria and insects of the families Hydropsychidae, Heptageniidae, and Elmidae than on the experimental logs in slowly moving, shallow water. Communities on the introduced logs did not reach a climax stage during the experimental period because organisms, organic detritus, and slit were constantly accumulating or sloughing off, the substrate was slowly decomposing, and changes were occurring seasonally in the chemical and physical condition of the water, all of which modified the habitat and influenced community development.

Effects of Temperature Acclimation on the Swimming Ability of Smallmouth Bass Fry

Abstract Entire year classes of smallmouth bass are frequently lost in midwestern streams during floods that occur when the fry are less than 25 mm long. Since changes in air and water temperatures often accompany these floods, the effects of temperature on swimming ability of fry 20–25 mm in length were measured in the laboratory and related to floodwater conditions. Groups of fry were acclimated to temperatures of 5, 10, 15, 20, 25, 30, and 35 C and tested for swimming ability at each of these temperatures. The maximum swimming speed for fish acclimated to a particular temperature increased with successively higher test temperatures, to a level above which swimming ability declined rapidly. Swimming speeds attained were progressively higher for each higher level of acclimation with the exception of those from the upper extreme of 35 C. The best swimming performance was at a temperature above the acclimation temperature for all fry except those acclimated to 30 and 35 C and these fry failed to swim above...

Electric Seine as a Fish-Sampling Gear in Streams

Abstract We describe the basic design, construction, and electric field of a 9.14-m-long, AC electric seine powered by a 1,500-W generator. We determined this seines efficiency with respect to species number and abundance of various fish taxa in streams of 3–10 m in mean width. The electric seine was fished between block nets and was followed by a rotenone treatment whose efficiency was determined through the recapture of marked fish. We repeated this calibration procedure with a 6.1-m-long, 6.4-mm-mesh minnow seine and a pulsed-DC backpack electrofishing unit at sites with physical conditions similar to those of the electric seine sites. The electric seine method was more efficient for estimating species number and the abundance of common fish taxa. We recommend the electric seine, used in a prescribed manner, for most fish-sampling situations in wadeable streams.

Assessing Habitats Used by Warmwater Stream Fishes

Abstract Five methods were developed for locating and identifying an undisturbed, free-swimming, stream fish. These methods used (1) color-coded tags, (2) fixed electrodes, (3) optical measurements, (4) night collections, and (5) radiotelemetry. They permitted observations of most kinds of fishes, at any time of day or night, during any season (including under ice), and from streams of different sizes. Although no one method was equally useful in all situations, the methods were evaluated according to their effectiveness in determining habitat preferences of different fish species under various stream conditions. The importance of precision in locating a fish and its habitat was emphasized by our finding significant differences in physical measurements over extremely small areas.

Stream Drift as an Indication of Water Quality

Abstract Stream drift and benthos were collected from five stream locations having different levels of domestic and industrial pollution. The drift organisms from 100 m3 of water during the diel period of peak drifting was compared with the benthos from 1 m2 of stream bottom. Numbers and weights of both drift and benthos followed similar quantitative relations with water quality, generally increasing with water degradation. The relative abundance of benthos greatly exceeded that of the drift at the most polluted station where tubificids, which infrequently drift, were abundant. A greater variety of organisms occurred in the drift than in the benthos. Drifting organisms came from a wider spectrum of habitats and were collected with less effort than benthic organisms but did not always include certain benthic forms that seldom leave the stream bottom.

Minnow Productivity in a Small Illinois Stream

Abstract As a means of evaluating the effects of harvesting minnows in a small stream, a study was made of the minnow population in a section of Jordan Creek in east-central Illinois. Nine collections of minnows were made with an electric fish shocker from August 1950 through October 1953. These collections represented a large proportion of the existing population. The yields for the corresponding months of each of the succeeding years increased progressively. The minnow population as a whole exhibited annual cycles of abundance and of average weights of individual fish. Each species responded differently to various environmental factors and to the continuous cropping. Shocking, which is a more effective method of harvesting minnows than is seining, did not reduce the minnow population in the study section of Jordan Creek longer than a few months. The natural fluctuations of the minnow population made it difficult to measure the effects of cropping with the electric shocker.

A Marginal-Dot System of Indexing Reference Cards

money. The punch-card system of indexing by notching out combinations of holes in a prepunched card seems to fulfill these requirements. It can be used to index a wide variety of information (Casey and Perry, 1951), including vertebrate ecology (Adams, 1955). Many people have hesitated to use the punchcard system, or have tired of using it, because of the burden of handling every card in the file in order to select any one card. The effort seems especially excessive in selecting references to a particular author, for this system lacks the convenience of having all reference cards arranged alphabetically by authors, or requires additional coding and sorting to group the cards according to author