摘要:

Populations of young brown trout, Salmo trutta L., (from 66 to 111 millimeters in total length) were sampled during late August to November at known intervals after they had been planted in two streams. The stomach contents of 75 were analyzed. Two days after planting, 16 out of 26 stomachs contained some food; 82 per cent by volume was of aquatic origin. Only insects were eaten, and of these Ephemeroptera and Diptera were most important. After 16 days each of 20 stomachs contained food. Aquatic food still predominated (86 per cent), and a large part (93 per cent) was insect. Ephemeroptera and Diptera were still most important, although beetles (Coleoptera) were present to the extent of 21 per cent by volume. Earthworms, Arachnida, and isopods also were eaten. After 42 days, 10 trout were obtained. Aquatic organisms still made up a large part (79 per cent) of the stomach contents. Insects still predominated (86 per cent), and, while mayflies (Ephemeroptera) were still most important, Diptera, Orthoptera, Hemiptera and Plecoptera were well represented. The remains of a fish was found in one stomach.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1941)71[106:AFORPY]2.0.CO;2

出版商:Taylor & Francis Group    

年代:1942

数据来源: Taylor

摘要:

A heavy loss of fish occurred during April 1940, in the south end of Lake Waubesa, Wisconsin, and in the Yahara River below the lake. The fish affected were mainly black crappies, although bluegills, northern pike, yellow pikeperch, common suckers, and carp, were killed to a lesser extent. A heavy algal bloom composed principally of Chlamydomonas was concentrated in the area of fish loss and was accompanied by an extremely high (30–32 p.p.m.) oxygen content in the surface water.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1941)71[112:ASMOFA]2.0.CO;2

出版商:Taylor & Francis Group    

年代:1942

数据来源: Taylor

摘要:

An attempt was made to substantiate the repeated assertions of the commercial fishermen on the Great Lakes and of others that there was a direct causal relationship between the plantings of whitefish fry and subsequent catch. The records of whitefish fry plantings in Lake Erie during the years, 1920–1937, were correlated with those of catch during the period, 1923–1940. No causal relationship could be demonstrated between the two sets of data. Whitefish production in Lake Erie is not dependent on or noticeably affected by the planting of fry.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1941)71[118:RBTPOF]2.0.CO;2

出版商:Taylor & Francis Group    

年代:1942

数据来源: Taylor

摘要:

A quantitative method is presented for estimating the intensity of infestation of the ectoparasite Gyrodactylus on goldfish. When infested fish are immersed in solutions of cresol the Gyrodactylus leave the fish and drift about in the liquid. The number of organisms in the solution may then be counted by standard methods. A series of experiments was performed to determine the variability in counts of parasites as it might be influenced by the use of several different fish, by different workers making the counts, by variations in the time interval between the immersion and counting, and by the concentration of the cresol. From experimental evidence obtained, it was concluded that considerable variability was associated with the counts made from different fish. Counts made by different workers and counts made after various immersion times, did not vary significantly. Concentrations of 1:4,000 to 1:6,666 (parts cresol: parts water) appeared to be satisfactory for use with Gyrodactylus. The method described is suitable for use with modern experimental designs and provides a quantitative “yardstick” for judging the effectiveness of various treatments for controlling ectoparasites on fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1941)71[122:AMOMTN]2.0.CO;2

出版商:Taylor & Francis Group    

年代:1942

数据来源: Taylor

摘要:

The forms of the growth curves of rock bass from four lakes in northeastern Wisconsin with medium-hard to hard water bore a general resemblance to each other, but differed sharply from the curve for rock bass from a lake with extremely soft water. With the exception of a slight increase in growth in the third year of life the annual increments of length of the rock bass of Nebish Lake (4.0 p.p.m. of bound CO2) tended to decrease consistently beyond the first year. The good first-year growth in length of rock bass of Allequash, Silver, and Trout Lakes (16.8, 15.0, and 18.7 p.p.m., respectively, of bound CO2) was followed by poor growth in the second, third, and fourth years of life. This poor growth was followed in turn by good growth in the fifth and sixth years. The annual increments of length tended to decline beyond the sixth year of life. The growth of rock bass of Muskellunge Lake (10.0 p.p.m. of bound CO2) declined sharply in the second year of life. The annual increments of length were fairly constant in the second to seventh years, inclusive, but declined beyond the seventh year. In each lake the males grew more rapidly than the females.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1941)71[131:GOTRBA]2.0.CO;2

出版商:Taylor & Francis Group    

年代:1942

数据来源: Taylor

摘要:

The production of the shad fishery of the Chesapeake Bay has fallen in recent years to approximately one-seventh of its former level. Artificial propagation has not stemmed depletion. Hydrographic, pollution, biological, and statistical studies have eliminated the various causes held by the fishermen to be responsible for this decline except for a single item—overfishing, with the consequent excessive drain on the broad reserve. Researches of the Fish and Wildlife Service of the U. S. Department of the Interior and of the Chesapeake Biological Laboratory indicate that not more than 60 per cent of the spawners should be taken by the fishery (regardless of year class) if an ample brood stock is to be maintained. However, a further reduction of fishing intensity may be necessary in the Chesapeake Bay to rehabilitate the present brood reserve. Actually the annual catch of shad is far in excess of the 60-per-cent level. Tagging records and scale studies show the catch to be approximately 90 per cent of the entire population. In an attempt to reduce the fishing intensity legislation recently was enacted in Maryland.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1941)71[144:COFIIM]2.0.CO;2

出版商:Taylor & Francis Group    

年代:1942

数据来源: Taylor

摘要:

Male northern pike made up 65 per cent of the 378 adults taken in the upstream weir of the ditches tributary to the north bay of Houghton Lake in April, 1939. An estimated additional 50 fish moved upstream before the weir was installed. The males averaged 21.2 inches, total length, while the females averaged 23.5 inches. In 1940, 58 per cent of the 118 adults were males. Twenty-eight additional spawners (13 males and 15 females) captured outside the experimental area were later added to the 118 fish. The males of the 1940 run averaged 19.8 inches in total length as compared with 23.2 inches for the females. Most of the spawners appeared in the weir between 6:00 p.m. and 9:00 a.m. The average number of days that the adult northern pike spent in the ditches in 1939 was 18.25 (range of 6 to 50 days). In 1940 the average number of days spent in the ditches was 23.9 days (range of 4 to 90 days).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1941)71[149:OOTLHO]2.0.CO;2

出版商:Taylor & Francis Group    

年代:1942

数据来源: Taylor

摘要:

A study was made of two experimental fish ponds located at the Agricultural Experiment Station at Auburn, Alabama. Bottom samples were taken from June to November, 1940, in a 1.5-acre fertilized pond and in a 1.8 acre unfertilized pond. Two methods of sampling were used, the Petersen dredge method and the stove-pipe method. The latter method consistently gave a better quantitative sample than the former. The fertilized pond produced 382.9 pounds of fish per acre; the unfertilized pond produced 147.1 pounds per acre. The area of the fertilized pond was reduced two-thirds of its original size during the fall drought, causing a tremendous concentration of bottom organisms. The weight of bottom organisms in the fertilized pond during a 5-month period was 68.27 milligrams of dry organic matter per square foot, and for the unfertilized pond the average was 19.62 milligrams. The plankton samples for the same period contained an average weight of 5.81 milligrams per liter in the fertilized pond, and an average of 2.54 milligrams per liter in the unfertilized pond. Routine stomach analyses of bluegills from both ponds showed that the fish in the fertilized pond had plenty of insects throughout the period, and that in the unfertilized pond they had sufficient insects in June only. The fertilizer more than doubled the weight of fish, plankton and bottom organisms in the fertilized pond as compared with those in the unfertilized pond.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1941)71[165:BOIFAU]2.0.CO;2

出版商:Taylor & Francis Group    

年代:1942

数据来源: Taylor

摘要:

At Skaneateles Lake, New York, the main body of migrating rainbow trout entered Grout Brook, a tributary stream, in April, 1941, at high water when the maximum temperature entered an observed range of 42° to 55° F. The attendant increased flow of water which resulted from rain and melting snow might have affected the migration. Thunderstorms seemed to have a depressing effect upon the numbers of fish entering the counting trap. The migration was of uniform intensity during any period of the day or night.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1941)71[180:TSMORT]2.0.CO;2

出版商:Taylor & Francis Group    

年代:1942

数据来源: Taylor

摘要:

Population studies were made of five representative lakes in the Ocala National Forest, Florida, which ranged from immature to very mature in ecological age and development. The largemouth black bass made up a constant proportion of the total weight of the fish population. There was a direct relation between the number of pounds of fish per acre and the degree of ecological maturity of the lake. The number of largemouth black bass was from 12 to 27 per acre, which was less than one-third of the number stocked 3 years previously.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1941)71[184:FPOFFL]2.0.CO;2

出版商:Taylor & Francis Group    

年代:1942

数据来源: Taylor