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Recent changes in the deep-water fish populations of Lake Michigan

The deep-water fish fauna of Lake Michigan consisted of lake trout (Salvelinus namaycush), burbot (Lota lota maculosa), seven species of chubs or deep-water ciscoes (Leucichthys spp.), and the deep-water sculpin (Myoxocephalus quadricornis). Other species occupied the deep-water zone but were not typically part of the fauna. Lake trout, burbot, and a well established commercial fishery held the chub population in somewhat of a balance until the sea lamprey (Petromyzon marinus) destroyed the lake trout and burbot. Released from predation, one species of chub (L. hoyi) increased until its abundance in 1955 was 347 percent of that in 1930–1933. It is the smallest and most slowly growing of the chubs in the lake. Other chubs were reduced in abundance (1954–1955 abundance only 37 percent of that of 1930–1932) by an increased fishing pressure and by sea lamprey predation which shifted to them when lake trout and burbot became practically extinct. Selective destruction of the large chubs reduced the average length by 1.5 and 2.2 inches in the northern and southern portions of the lake, respectively, and practically eliminated two largest species (L. johannae and L. nigripinnis). Chubs over 10 inches long made up 72 percent of the catches in 1930–1932, but only 21.5 percent in 1954–1955.

Transactions of the American Fisheries Society

Limnological surveys of the Great Lakes--early and recent

Early explorations on the Great Lakes were concerned largely with things easily collected or observed—common organisms, water levels, surface temperatures … Even when more scientific studies were undertaken, they were at first scattered and small-scale. Effective surveys became possible only through inter-agency cooperation which permits a pooling of facilities, staff, and equipment. Expansion of limnological research on the Great Lakes has been rapid in later years and the outlook for the future is good.

Transactions of the American Fisheries Society

Experimental induction of blue-sac disease

Blue‐sac disease, an abnormal condition of sac fry, has been recognized for nearly 90 years. At least 23 postulated causes have been advanced, but reports of consistently reproducible results have not been found in literature. Methods whereby blue‐sac disease was induced at will are described. Closed‐system incubation, whereby metabolic wastes accumulated, resulted in incidences of blue‐sac disease roughly proportional to the period of holding and to ammonia concentrations which developed. Blue‐sac disease was also induced by adding synthetic nitrogen compounds to water used for incubating eggs and fry.

Transactions of the American Fisheries Society

Fishery management problems and possibilities on large southeastern reservoirs

Principal problems concerning the fisheries of large reservoirs in the Southeast are: inefficient and highly selective exploitation of fish stocks, and protection and reclamation of damaged or threatened fisheries in tailwaters and tributary streams. Seven mainstream reservoirs on which data are available support an average angling pressure of 4.9 trips per acre per year and an average catch of 16 pounds of sport fish and 6 pounds of food fish. Commercial take is 7 pounds per acre. The rate of catch of sport fish, based upon tag returns, is only 3 percent. Sixteen storage reservoirs support an average angling pressure of 5.0 trips per acre per year and an average catch of 13 pounds of sport fish and 1 pound of food fish. Commercial catch is of no significance. Average rate of catch of sport fish is 17 percent of the catchable population. Fish population studies indicate that there are twice as many sport fish and four times as many food fish in mainstream than there are in storage reservoirs. Some reservoirs produce harmful effects downstream. Discharges of cold water may seriously reduce fishery values in tailwaters and downstream impoundments. Furthermore, migration of non-sport fish from reservoirs into tributary streams may reduce fishery values there. In recognition of these problems, the development and application of sound management procedures may be accomplished by controlling species composition and availability of fish through water level control, timber clearing, application of selective toxicants, commercial fishing, introduction of new fish species, and the management of tailwaters and tributaries. Extended research and interagency cooperation are necessary to properly develop and apply sound management. Promotion of angling and regulation of the fishery may best be realized by providing adequate fishing facilities, elimination of certain restricted areas, and in some cases revision of laws and regulations. Biologists must not only meet the present demands for improved sport fishing but must also balance fish yield by increasing the use of food fish by sport and commercial operations.

Transactions of the American Fisheries Society

Some problems of private trout hatchery operators

Disease, nutritional, and environmental problems in commercial production of trout are discussed, including mortality and age of spawners, copepod and gyrodactylid infections, suitable water temperatures, diseases (especially red mouth and back peel) and inspection of fish. It is concluded that experiences with hatchery procedures have varied greatly and often the commercial trout producer must adjust methods to fit his particular needs and conditions.

Transactions of the American Fisheries Society

Suggestions for reduction of natural mortality in fish populations

Illness, in fish as well as in other animals, when caused by an infectious disease, is often not the result of infection with pathogens alone. In many cases the pathogens and hosts can exist side by side without development of disease symptoms. Such symptoms, with resulting illness or death, appear only when the balance of mutual tolerance between the host and the pathogen is shifted in favor of the pathogen. Factors of several different kinds may render a host susceptible to disease; such things as poor nutrition, unfavorable physical conditions in the environment and the hereditary make‐up of the fish itself. Drugs may allow temporary control of infectious diseases but for the long‐range control it is better to increase the resistance of the host. Some suggestions are given, based largely on experience with disease control in hatcheries and fish farms, for minimizing natural mortality of fish from infectious diseases.

Transactions of the American Fisheries Society

Relationship between Secchi disc readings and light penetration in Lake Huron

Fifty-seven paired photometer and Secchi disc measurements made at 18 stations in Saginaw Bay and Lake Huron support the view that a counter-clockwise current usually occurs in the Bay with more transparent Lake Huron water flowing in along the northwest shore and less transparent Bay water flowing out along the southeast shore. The average percentage transmission of surface light intensity, at the Secchi disc depth, was 14.7 percent. Discrepancies in the relationship of disc readings to percentage transmission of surface light are related to the condition of the sky and sea. It is suggested that these discrepancies can best be explained on the basis of the spectral sensitivity of the human eye and its response to surface glare.

Transactions of the American Fisheries Society

Test of 34 therapeutic agents for control of kidney disease in trout

Sixteen strains of fish kidney disease bacterium were tested in vitro to determine their reaction to 34 therapeutic agents. On the basis of the results obtained ten of the drugs were employed in experimental therapy of kidney disease in eastern brook trout (Salvelinus fontinalis). Erythromycin at the rate of 100 milligrams per kilogram of fish per day (4.5 grams per 100 pounds of fish) for 21 days gave the best results. Other drugs gave only temporary benefit if any.

Transactions of the American Fisheries Society

Infectious nature of pancreatic necrosis

To determine if pancreatic necrosis is a communicable disease of trout, lots of eyed brook trout eggs were obtained from four hatcheries. Pancreatic necrosis appeared spontaneously in trout from one of these hatcheries and the other strains were exposed to infection by suspension prepared from diseased fish. In all cases, typical pancreatic necrosis appeared in fish exposed to infection and the control fish remained healthy. Disease was more acute in fry fed brine shrimp nauplii than in those fed beef liver. Mortality data suggest that susceptibility to pancreatic necrosis decreases with the increased age of trout. No treatment for the disease is known, but sanitary measures were effective in preventing its spread.

Transactions of the American Fisheries Society

Effects of certain chemicals on mucus-producing cells of Petromyzon marinus

Tissue samples that contained slime-secreting cells were taken from the gills and epidermis of larval lampreys that had been poisoned by several compounds. Histochemical treatment of these pathological tissues helped delineate the fate of these mucus-producing areas of the ammocetes. It was shown that the slime-secreting cells, located at the tips of the gill filaments, lining the gill chamber, and scattered throughout the epidermis reacted differently to the same toxicant. The secretory cells of the gills were, without exception, the most sensitive to chemical attack.

Transactions of the American Fisheries Society

Studies on the life cycle of Apatemon gracilis pellucidus (Yamag)

A tetracotyliform metacercaria was found in the musculature of the brook stickleback (Eucalia inconstans). It is characterized by a tail‐like appendage on the cyst. The adult was reared in newly hatched chicks, and proved to be Apatemon gracilis pellucidus (Yamaguti, 1933). Attempts to infect snails, Physa, Stagnicola and Helisoma, were unsuccessful.

Transactions of the American Fisheries Society

A Virus-like disease of chinook salmon

Consideration is given to a recurring disease of early feeding chinook salmon fingerlings at the Coleman, California, Federal Fish Cultural Station. The infection becomes manifest in the early spring months at low water temperatures and abates as the water temperature rises. Bacteriological studies have failed to yield the presence of a disease agent, either by cultural or staining procedures. The disease has been successfully transmitted from infected fish to healthy fish by the injection of bacteria-free filtrates prepared from diseased fish tissue. The causative agent is therefore believed to be a virus-like entity.

Transactions of the American Fisheries Society

The bottom fauna of Lake Huron

The examination of 63 bottom samples, collected in Lake Huron in 1952 and 1956, revealed that Pontoporeia affinis was the dominant organism in both deep and shallow water. The next most abundant organisms in deep water were oligochaetes, fingernail clams, and midge larvae. Midge larvae were more numerous than either oligochaetes or fingernail clams in shallow water. The nmnber of organisms per square meter was similar to that determined from a similar study on Lake Michigan.

Transactions of the American Fisheries Society

The stoneroller, Campostoma anomalum (Rafinesque), in Great Smoky Mountains National Park

The stoneroller (Campostoma anomalum) is one of the more important fish in Great Smoky Mountains National Park because of its abundance and habits. Although esteemed locally as a food and a bait fish, the stoneroller is exploited but little since the fishing regulations which govern the utilization of game fishes afford it a large measure of protection. Distribution is controlled by gradient with an upper limit of 4.4 percent. Stonerollers limit reproduction of rainbow trout (Salmo gairdneri) by destroying trout redds. Artificial reduction of stoneroller populations is not considered a necessary management procedure.

North Carolina, Tennessee

Chemical and histological studies of wild and hatchery salmon in fresh water

In a study of coho salmon ( Oncorhynchus kisutch ), the gross chemical and histological changes occurring over a 14-month period spent in fresh water were determined. The determinations were made at 3-month intervals on: 1) hatchery-reared fish, 2) fish hatchery-reared for 3, 6, 9, and 12 months and then planted in a controlled stream for the remainder of the period; and 3) an indigenous group of wild fish in this stream. Wild fish showed high incidence of tissue damage from spinose hairs of the moth larva, Halisidota argentata. Hatchery fish were similarly affected with the severity and incidence of lesions varying directly with the time of exposure of the larvae in the wild environment. Both groups of fish were heavily parasitized by sporozoan organisms in the kidney and spinal cord. Kidney disease appeared in both wild and planted hatchery fish. The gross chemical composition of hatchery fish transformed rapidly after planting to that of the wild fish. Although the initial rate of fat loss is essentially constant for all hatchery groups after planting, fish that were hatchery reared for 9 to 12 months did not complete the transformation to the wild-type body composition by the time of downstream migration at 14 months.

Transactions of the American Fisheries Society

A bacterial disease of yellow perch ( Peres flavescens )

On May 26, 1959, two of the authors' investigated a fish kill at Dailey Lake, Park County, Montana. They observed about a half-dozen live, weakly swimming yellow perch ( Perca flavescens ), in addition to thousand of dead perch along the shoreline. It was learned from local residents that mortalities had begun to appear some 2 weeks earlier. At that time the time the authorities had diagnosed the condition as a winterkill, since ice had only recently disappeared from the lake. Although a number of other species inhabit Dailey Lake, including rainbow trout (S almo gairdner i), brown trout ( S. trutta ), kokanee ( Oncorhynchus nerka ), black crappie ( Pomoxis nigromaculatus ), largemouth bass ( Micropterus salmoides ), longnose suckers ( Catostomus catostomus ), rainbow x cutthroat hybrids, only one other species was represented in the kill. This consisted of one black crappie. Examination of the freshly dead perch revealed the presence of multiple petechiae, which were visible externally as well as in the dorsal musculature. The peritoneal cavity showed evidence of inflammation and contained a bloody ascitic fluid. A number of the dead fish were placed on ice and shipped to the Western Fish Disease Laboratory in Seattle for bacteriological studies.

Montana

Age and growth of the whitefish Coregonus clupeaformis, of Munising Bay, Lake Superior

This study is based on a sample of 415 whitefish collected in 1953 from an unexploited population in Munising Bay, Lake Superior. Gill-net and trawl catches had different length-frequency distributions and age compositions, but estimates of growth from the two catches were very similar. The body-scale relation is a straight line with an intercept of 1.5 inches. Weight of Munising Bay whitefish captured in June increased as the 3.17 power of the length. Growth in length and weight of Munising Bay whitefish was the slowest yet reported from Great Lakes waters. Munising Bay whitefish required nearly 8 years to reach a length of 10 inches and a full 13 years to reach 15 inches. Slightly more than 8 years were required to reach a weight of 8 ounces and a little less than 14 years to reach 1 pound. The sex ratio of the Munising Bay whitefish exhibited no systematic change with an increase in age. The entire sample for which ages were determined contained 52 percent males. Munising Bay whitefish matured at much shorter lengths but at a greater age than reported for other Great Lakes whitefish populations. The smallest mature males were in the 11.5- to 11.9-inch length interval (age-group VII) and all males longer than 14.4 inches (age-group XII) were mature. The first mature females appeared at 12.0-12.4 inches (age-group X) and all females longer than 14.9 inches (age-group XII) were mature. The more rapidly growing individuals matured earlier than the slow-growing ones.

Transactions of the American Fisheries Society