Book Review: Fragile Giants: A Natural History of the Loess Hills

The Loess Hills, which are a special feature of the eastern bank of the Missouri River in Iowa and northern Missouri, have been cited by Dean Roosa, Iowa\u27s State Ecologist, as a world treasure and ... our best-kept secret. These Hills are mounds of finely ground soil, glacial flour, deposited by dust storms after the glaciers receded 31 to 12 thousand years ago. Loess is rather widely distributed in Iowa, but the extensive deposits (often over 200 feet deep) on and against the eastern wall of the valley left a rolling, wave-like, terrain which on erosion leaves vertical banks of compacted soil. Cornelia Mutel of the University of Iowa has compiled a comprehensive introduction to this unique Iowa treasure. The characteristic features of the Hills and their flora and fauna are illustrated with drawings and photographs (5 maps, 77 figures, and 8 colored photographs)

Use of Gill Nets in Studying Fish Populations, Clear Lake, Iowa

Gill nets are among the most effective gear for collecting many species of lake fishes. In scientific investigations we usually use gill nets with several sizes of mesh to sample fish of various sizes. The standard experimental gill net usually consists of 25-foot lengths of the following stretch measure mesh sizes: 1.5, 2, 2.5, 3, and 4 inches. These nets will catch, with little size selection, walleyes and suckers from 6 to 23 inches, and yellow perch, yellow bass, white \u27bass, and bullheads from 4.5 inches to their maximum sizes

Measurements of Boating and Fishing, Clear Lake, Summer 1968

Between June 29 and July 24, 1968, counts of boats and fishermen on Clear Lake were made at scheduled times. The peak count was 258 boats between 2 and 3 P.M. on a Sunday, about 1 boat per 14 acres. The total per week came to 5747 boat hours, with about 35% of it on weekends. Boat usage declined earlier in the evening on Sundays than on other days. Power boats constituted about 45% of the total boat hours, and fishing boats about 25%. Water skiers were most active in afternoon and evening, and most of the sailboating occurred on Sundays. Fishing effort per week was estimated at 8121 man-hours, and the weekly catch at 3135 fish, including 1932 bullheads and 491 walleyes

Seasonal Variation in Weight-Length Relationships of Largemouth Bass in a 3-Hectare Reservoir

Lengths and weights of age 0, I, and II largemouth bass were collected during two growing seasons to evaluate seasonal trends in weight-length relationships. Average K(TL) declined significantly between August 1971 and April 1972, but significant growth in length occurred during the interval. In 1972, K(TL) increased from April to July and remained high into November. Condition was better in 1972 than in 1971 when the population density was greater. Monthly estimates of the coefficient of condition, K(TL), and weight-length regressions were both required to interpret seasonal changes. Weight-length regressions calculated over longer collection periods in which K(TL) changed significantly generally did not represent the populations. Average K(TL) provided meaningful comparisons of condition only when monthly weight-length regressions indicated isometric growth

Standing Crops of Fish in Iowa Ponds

The fish populations of 42 Iowa ponds have been estimated for various reasons in the last 10 years by the Iowa Cooperative Fisheries Research Unit (Table 1). Although the data on some of the ponds have already been published (Fessler, 1950; Fredin, 1950; Carlander, 1951, 1952; Ruhr, 1952; Lawrence, 1952), it seems desirable to summarize the results. Most of the estimates were made by the marking and recapture technique. The pond was seined with a 50 to 70 foot seine and all fish were marked by clipping off a fin and were returned to the pond, until about one-third of the fish taken in the seine hauls have already been marked. In ponds under 1/2 acre, 2 or 3 good seine hauls were usually sufficient. Further seining was then delayed until at least the next day to permit the marked fish to redistribute themselves

The Iowa Cooperative Fisheries Research Program

The Iowa State Conservation Commission and Iowa State College cooperate in a program of research, extension and education in the field of fishery management. This cooperative program, initiated in 1941, was patterned after that of the earlier established Cooperative Wildlife Research Unit (Scott, 1939). The research work is carried on by the permanent staff at the college and by graduate students some of whom are on fellowship appointments. The problems being investigated include those deemed most important in the management of Iowa\u27s fishery resources and include work on streams, natural lakes, reservoirs, artificial inpoundments, and farm ponds

Observations on Fishery Management in Africa

Fisheries personnel in Liberia, Nigeria, Ghana, Sudan, Uganda and Egypt were visited in March and April 1965. Harvest of fish from the sea, lakes and rivers is being improved through improved boats, motors, and docking marketing facilities. High dams on the Nile and Volta Rivers are providing new fishery resources which will require research and development of new techniques. Flooded vegetation has caused oxygen depletion in the Volta Reservoir. The dams will also interfere with spawning of fish and clams downstream, and the Nile dam has already reduced the catch of sardines in the Mediterranean. Fish culture is hindered by lack of experience and research and by shortage of supplemental foods. Africanization of the fisheries departments has often displaced trained biologists before their counterparts could be trained. Attention is being given in each country to the training of fisheries personnel, but outside help will be needed for many years

An Unusually Large Population of Fish in a Gravel Pit Lake

Lakes in gravel pits are usually relatively unproductive but Ruth\u27s Lake near Marshalltown was found to have a larger fish population than has been reported for any other water, except for carp ponds where the fish are artificially fed. When this lake was treated with rotenone, over 1200 pounds of fish per acre, were collected, compared to the 100 to 400 pounds per acre found in most lakes and ponds (Carlander, 1950)

Water Hyacinth and Overfishing Problems on an Indonesian Lake

Water hyacinths, Eichhornia crassipes, and floating grass islands have been a serious problem for more than 50 years on Rawa Pening, a 2500-ha lake in central Java. Fish harvest increased with control of the plants in 1932-42 and 1951-56 but decreased as plants again increased in abundance. Control measures since 1962 have maintained open water but have not eliminated the problem. Hydrilla verticillata becomes abundant as the surface is cleared of water hyacinths. Hydrilla shelters Macrobrachium shrimp and other aquatic organisms, important to fish, and also is harvested for pig food. Annual fish yield dropped from about 530 kg/ha in 1972 to 178 in 1975 and to 18 kg/ha in 1978. Most species of fish averaged smaller in 1978 than in 1975. Overfishing is indicated, but the low catches are probably the result of other factors also