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Scyphidia micropteri, a new protozoan parasite of largemouth and smallmouth black bass

A small urn‐shaped peritrichous protozoan, apparently an undescribed species, was found on the gills and bodies of largemouth and smallmouth black bass in ponds at Leetown, West Virginia. A heavy mortality among a lot of fingerling largemouth bass probably resulted from suffocation due to the organisms on the gills. Specimens of the parasite, preserved in formalin, measured about 57 microns in length and 24 microns in maximum width. The base of the animal consists of a circular disc about 6 microns in diameter. No evidence was found that the sucker‐like attachment disc penetrated the epidermal cells of the host causing necrotic tissue. The anterior or upper end of the animal has a ciliary disc and two rows of cilia. The body is without cilia and is annulared. The macronucleus is very large, has the shape of an inverted cone and occupies much of the lower half of the body. The small micronucleus apparently lies in the slightly concave surface of the upper part of the macronucleus, although there is doubt on this point. This new species was named Scyphidia micropteri after Micropterus, the generic name of the smallmouth black bass, one of its hosts. The species recently was found by Dr. H. S. Davis on gills of largemouth black bass collected in Radnor Lake, Tennessee, which indicates a wide geographical distribution of the parasite.

Transactions of the American Fisheries Society

Neascus infection of black-head, blunt-nosed, and other forage minnows

Black‐head, blunt‐nosed, and other minnows were found infested with encysted flatworms in ponds at Leetown, West Virginia. The mortality in a 2.2‐acre pond stocked with 100,000 black‐head minnows was about 250 per day during four weeks of observation. Heavy infestations caused sterility in the minnows. The cyst and parasite are described briefly and the probable life cycle given, followed by certain recommendations for the control of the infestation.

Transactions of the American Fisheries Society

Tagging experiments with lake trout, whitefish, and other species of fish from Lake Michigan

A total of 2,902 Lake Michigan fish was tagged and released, 48.8 per cent of which were lake trout and 85 per cent lake trout, lake herring, and whitefish. A total of 388 fish or 13.4 per cent was recaptured. The percentages of returns indicated a tremendous fishing intensity for lake trout, whitefish, and sturgeon. About 81 per cent of the recaptured fish were retaken within a radius of 25 miles from the port of tagging (Port Washington, Wisconsin). Lake trout, rainbow trout, and sturgeon were found to be extensive travelers; lake herring, whitefish, chubs, pilots, and perhaps perch did not migrate so extensively. Lake trout, herring, and whitefish tended to move in a northerly direction, perch in a southerly, and rainbow trout in all easterly, toward the Michigan shore. Sturgeon apparently roam all over the lake. Fifty-three per cent of the recovered lake trout were recaptured within one year of release, 73 per cent within 25 miles from Port Washington. It required three years for the trout to become fairly well scattered throughout the lake. With the attainment of adulthood lake trout moved in all directions from the port of release, although nearly 50 per cent of the adults were retaken within 25 miles from this port. Fish moved across state boundaries. Data are given on the growth and estimated age of the tagged lake trout, rainbow trout, whitefish, and sturgeon. The minimum size limits of lake trout and whitefish on the Great Lakes are economically unsound–they are too low–because they permit the capture of these species at a time of most rapid increase in weight.

Transactions of the American Fisheries Society

An evaluation of trout culture

In an evaluation of the efficiency of trout culture, the author presents a detailed analysis of complete loss records from 288 individual lots of trout at twenty-two hatcheries in the western United States. Summarized data are given to show the percentage loss of eggs, fry, and fingerlings by progressive one-half inch size groups. The accumulative percentage loss is also included to indicate the losses, under average hatchery conditions, between the egg stage and each successive size-group. These data cover the individual species of trout commonly reared in hatcheries; summarized data are given also for all species combined. A brief discussion of hatchery losses, natural losses, and the cost of artificial propagation is included.

Transactions of the American Fisheries Society

Experiments upon the control of Trichodiniasis of salmonid fishes by the prolonged recirculation of formalin solutions

In a search for more effective disinfectants to combat parasitic diseases of hatchery fish, the authors report results from a series of experiments designed to determine the toxicity of varying exposures to concentrations of formalin, sodium p‐phenolsulphonate, ammonium sulphate, and sodium benzoate. Non‐toxic concentrations of these disinfectants were tested, in addition to the usual hatchery methods of salt treatment and hand dipping in copper sulphate and acetic acid solutions, on No. 1 brook trout fingerlings which had been experimentally infected with the protozoan parasite Trichodina sp. (previously known as Cyclochaeta sp.). Of the disinfectants tested, only formalin completely removed all parasites. Salt treatment in a 5 per cent solution, by weight, as well as hand dipping in 1:500 acetic acid, failed to eradicate all parasites present, although a marked reduction in their numbers did occur. The hand dipping in a 1:2,000 copper sulphate solution was found to be without practical value for the removal of parasites. The authors recommend a prolonged treatment for sixty minutes by recirculating a 1:4,000 solution of formalin, or, where circumstances permit, a 120‐ to 150‐minute exposure to a 1:6,000 concentration of formalin, as the most effective, most economical, and least toxic treatments for combating infections of Trichodina sp., and presumably those of other external parasites as well, among hatchery fish.

Transactions of the American Fisheries Society

Age, growth, and production of the yellow perch, Perca flavescens (Mitchill), of Saginaw Bay

Ages were determined and individual growth histories computed from the examination and measurement of scales from 820 yellow perch collected in 1929 and 1930. Calculated lengths greater than 101 millimeters were computed on the assumption (supported by empirical data) that the ratio of body length to scale length is constant. Lengths below 101 millimeters were determined with the aid of an empirical curve of the body-scale relationship of small fish. Yellow perch of age-groups III and IV (in the fourth and fifth years of life) made up the bulk of the collection (78 per cent). Females grew slightly more rapidly than males, but members of both sexes attained the legal length of 8 1/2 inches during the fourth year of life, just as they were entering on the period of most rapid growth in weight. The greatest growth in weight of both sexes occurred in the sixth year of life. In the combined samples of the two years the females exceeded the males in abundance in the ratio, 296:100. The weight of the Saginaw Bay yellow perch was found to increase as the 3.117 power of the length. The relative length of the tail decreased with increase in the length of the fish. The Saginaw Bay yellow perch is now far less abundant than it was in the early years of the fishery. The average annual production of 548,000 pounds over the period, 1917-1938, was only 28 per cent of the earlier (1891-1916) "normal" annual production of 1,961,000 pounds. A detailed analysis of statistical data available for more recent years made possible a description of annual fluctuations in the abundance and production of yellow perch and in the intensity of the yellow perch fishery in Saginaw Bay over the period, 1929-1938.

Transactions of the American Fisheries Society

A new fungus disease of trout

A new species of fungus, for which time name Saprolegnia invaderis is proposed, was found in fingerling trout at the Leetown (West Virginia) hatchery. Infection occurs through the alimentary tract from which the fungus grows out through the body cavity and the abdominal wall to the exterior, where zoospores and chlamydospores are formed. Growth of the hyphae through the abdominal wall occurs only after the death of the host. A short technical description of the parasite is included.

West Virginia

Notes on Costia Necatrix

Costiasis, or the disease produced by the flagellated protozoan ectoparasite, Costia necatrix, is of considerable importance in the artificial propagation of both warm- and cold-water fishes. In spite of its importance, costiasis seldom is accurately diagnosed probably because of the extremely small size and sedentary nature of the causative organism. A general resume of the specific diagnostic characteristics, pathology, and recommended measures for the prevention and control of Costia necatrix are presented. The application of available information concerning the parasite may eliminate effectively the losses of fish in hatcheries occasioned by it.

Transactions of the American Fisheries Society

Relationship between plantings of fry and production of whitefish in Lake Erie

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.

Transactions of the American Fisheries Society

Growth of the rock bass, Ambloplites rupestris (Rafinesque), in five lakes of northeastern Wisconsin

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 CO 2 ) 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 CO 2 ) 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 CO 2 ) 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. The time of attainment of the legal total length of 7 inches in the different lakes ranged from late in the sixth growing season in Nebish and Trout Lakes to the middle of the eighth growing season in Muskellunge Lake. Rock bass of corresponding length from Allequash, Silver, and Trout Lakes were so nearly of the same weight that one curve described the length-weight relationship of the three stocks. Muskellunge Lake rock bass were considerably lighter than fish of the same length from these three lakes, and Nebish Lake rock bass were somewhat lighter than those from Muskellunge Lake.

Transactions of the American Fisheries Society

The age, growth, and bathymetric distribution of Reighard's chub, Leucichthys reighardi koelz, in Lake Michigan

Reighard's chub has come to be one of the most important species of the group since the serious decline in abundance of the larger representatives of the genus Leucichthys in Lake Michigan. An understanding of the biology of as many species of chubs as possible is essential if further depletion and the collapse of the fishery are to be prevented. The age and growth of 331 individuals taken in 1932 were determined. Each of the other phases of the study is based on more than 5,000 specimens collected during the three years, 1930–1932. Reighard's chub occurred most abundantly, when not spawning, in depths of 20 to 60 fathoms where the temperature of the water ranged from 38.8 to 40.6° F. It was taken at all depths where the nets were set from 12 to 97 fathoms, and in water that varied from 34.7 to 50.6° F. The abundance on the east shore was seven times that on the west shore and between two and three times that in the upper part of the lake. The data indicate the existence of separate populations on the two shores. The greater exploitation with smaller meshes in the western part of the lake probably accounts for the relative scarcity in those waters. Ecological factors are considered the probable cause of the lesser abundance in the upper lake. Spawning occurs during May and June at depths of 20 to 79 fathoms, over a wide variety of bottom materials at temperatures of 38.8 to 40.5° F. Age-group IV dominated in the samples of fish whose ages were determined and made up 50.2 per cent of the total. Age-groups V and III were the next largest groups in that order. Growth in length was most rapid during the first year of life. Growth in weight was most rapid during the first three years with the annual increment in weight about the same in each of those years. The sexes grew in both length and weight at approximately the same rate. Growth compensation occurs in the reighardi of Lake Michigan, but the first year differences were not removed entirely by the time of capture in the fifth year. The weight of the fish in the combined samples increased as the 2.468 power of the length. No relationship between condition (K) and rate of growth could be demonstrated. Condition (K) was better in 1931 than in either 1930 or 1932 and usually was better in 1930 than in 1932. The seasonal changes in relative heaviness followed the same general trend irrespective of the sex or stage of maturity of the fish. The females lost 8 per cent of their weight in spawning, but no loss of weight could be demonstrated for the males. The females were always strongly dominant in the samples except during May and June 1931 and May 1932 when the sexes occurred in about equal numbers. The relative abundance of the sexes did not change materially in age-groups II to V. There were no males assigned to age-groups VI and VII.

Transactions of the American Fisheries Society

Scyphidia tholiformis, a peritrichous protozoan found on the gills and external surfaces of Micropterus dolomieu and Micropterus salmoides

Scyphidia tholiformis is an urn‐shaped peritrichous protozoan measuring about 59 microns in length and 35 microns in width. It possesses a double row of cilia about one‐third of the distance from the anterior end of the body and has a large scopula which is variable in shape and provides a large surface for attachment. The macronucleus is long and band‐like, and makes a semicircle beneath the peristome from which it extends into the lower part of the body. The small, ovoid micronucleus is located near the middle of the body. The organism is found on the external body surfaces and the gills of large‐mouth and smallmouth black bass. Its relationship to its host is probably that of an ecto‐commensal, but there is further evidence that these organisms may indirectly cause mortality among bass. The organism is interesting because of the manner in which it becomes dome‐shaped when it leaves its host, causing it to resemble Trichodina. In this form, locomotion is accomplished by means of the central cilia. It reproduces by longitudinal binary fission and cojugation of anisogametes.

Transactions of the American Fisheries Society

Observations on the natural and artificial propagation of the smallmouth black bass, Micropterus dolomieu

Counts of smallmouth black bass nests in the same sections of the South Branch of the Potomac, the Cacapon, and the Shenandoah Rivers are reported over a period of several seasons. The 4‐year record for the South Branch of the Potomac indicates little change in the smallmouth black bass population. The number of nests varied between 50.7 and 73.2 and averaged 58.1 for each mile of stream. The results of fry counts from wild nests showed an average of 2,159 fry in each nest in the South Branch of the Potomac, 2,210 in the Cacapon River, and 1,998 in the Shenandoah River. One important characteristic of natural propagation in these rivers is the simultaneous occurrence of spawning in any section of stream having similar conditions. Evidence is supplied to support the theory that a long, drawn‐out spawning season in artificial ponds is due to annoyance of the brood fish. The importance of attendance by the male fish at the nest is pointed out. Examples in pond culture are given to demonstrate that there are other factors involved in the spawning of smallmouth black bass besides temperature. These factors are annoyance, over‐crowding of the brood fish, and lack of provision for greater individual privacy among the brood bass during their spawning season. In general, productivity of fry apparently increases with age and size of the brood fish.

Maryland

The anaesthesia of fish by high carbon-dioxide concentrations

A practical and economical method for anaesthetizing adult salmon and steelhead trout in the fish trucks used in the Grand Coulee fish salvage program is described. The method consists in generating a predetermined carbon-dioxide concentration in the 1000-gallon tanks of the trucks through the successive addition of predissolved sodium bicarbonate and dilute sulphuric acid in proper quantities. Carbon-dioxide anaesthesia effectively solved the acute problem of species segregation in the fish salvage program and, with minor modifications, could be used with equal success in certain hatchery operations necessitating the handling of large fish.

Transactions of the American Fisheries Society

Distribution, abundance, and spawning season and grounds of the kiyi, Leucichthys kiyi Koelz, in Lake Michigan

From May to November, inclusive, the kiyis of southern Lake Michigan (north to and including localities off Kewaunee, Wisconsin, and Frankfort, Michigan) characteristically inhabit depths of more than 50 fathoms, although small numbers commonly are taken in shallower water (as shallow as 20 29 fathoms). There is evidence that the occasional penetration of relatively large numbers of kiyis into depths of less than 50 fathoms in this area is the result of exceptional hydrographic conditions involving the disturbance of considerable masses of water. In northern Lake Michigan the scattered lifts made in the region south of Manistique, Michigan, from June to September indicated kiyis to be abundant at depths from 40 to 69 fathoms (no lifts from shallower or deeper water). In northeastern Lake Michigan (Manitou, Fox, and Beaver Islands and the region between these islands and the east shore) kiyis were lacking in all lifts from 20–39 fathoms and were scarce at greater depths (three to four times as abundant, however, at 50–69 fathoms as at 40–49 fathoms). The consistency with which kiyis remain in water deeper than 40 or 50 fathoms is difficult to explain on the basis of a preference for cold water (about 4°C.). Water of temperatures only a fraction of a degree warmer than that in the region occupied by most kiyis extended up to depths of less than 30 fathoms. Possibly the bathymetric distribution of the kiyi is related to that of its principal food organisms. It was suggested also that the deeper-water habitat may enable the kiyi to avoid strong currents and that an aversion for currents may account for the scarcity of the species in the hydro-graphically complex northeastern area. Other possible factors are chemical conditions of the water or a preference of kiyis for great pressure and darkness. The abundance of kiyis appeared to be more or less uniform throughout the great central basins of Lake Michigan, except as related to depths of water. The scarcity of this species in the island region of northeastern Lake Michigan provided the only certain example of a regional difference in abundance. The survey of 1930–1932 yielded 89 new locality records for the kiyi in Lake Michigan. These localities, together with those reported previously by Koelz (1929), have been charted in Figure 1. Although the gonads of certain apparently aberrant individuals may ripen as early as mid-July and considerable pre-spawning development of the organs may occur in August, there is no evidence of significant spawning activities of kiyis in southern Lake Michigan before the latter part of September. Spawning continues through at least the first week or two in November and possibly longer. The peak of spawning activity seems to occur in the latter half of October and in early November. The depth of water on known spawning grounds (all in southern Lake Michigan) was 57.5 to 84 fathoms. There is evidence that the kiyi may spawn in more than 90 fathoms. Spawning appears to be widespread throughout waters of suitable depth.

Transactions of the American Fisheries Society

Variations in nitrogen content and fish production in smallmouth black bass ponds

Ammonia, nitrite, nitrate, and organic nitrogen were determined at 10‐day intervals for 24 ponds at Leetown, West Virginia. These ponds were stocked with 15,000 smallmouth black bass fry per acre and all fish reared in them were counted individually and weighed when the ponds were drained after an average season (during 1943) of 105 days. The purpose of the study was to determine what correlations, if any, existed between fish production and the nitrogen content of the water. Correlations between ammonia, nitrite, and nitrate nitrogen and fish production were not evident. Larger quantities of these forms of nitrogen were present during the first half of the pond season than during the latter half. A positive correlation was found between the organic‐nitrogen content of the water and fish production. This form of nitrogen, probably as a result of plant decay, was present in larger quantities during the latter half of the season than during the early season. Ponds which averaged 0.56 and 0.65 pounds of bass per acre per day had average organic‐nitrogen contents of 0.494 and 0.434 p.p.m. Ponds averaging 1.69 and 1.79 pounds of bass per acre per day averaged 0.811 and 0.746 p.p.m. of organic nitrogen, respectively.

Transactions of the American Fisheries Society

Age and growth of the kiyi, Leucichthys kiyi Koelz, in Lake Michigan

Ages were determined and individual growth histories were calculated from the examination and measurement of the scales of 1,649 kiyis captured at seven localities in Lake Michigan in 1931 and 1932. The numbers of individuals employed for the investigation of other phases of the life history (such as length-frequency distributions, length-weight relationship, and sex ratio) varied according to the amount of data available or required. Age-group IV was dominant in the 1931 collections from Racine, Port Washington, and Kewaunee, Wisconsin, and age-group V dominated the 1932 samples from the Fox Islands and from three localities southward of Manistique, Michigan. A trend was noticeable toward an increase in average age from south to north. Among the explanations suggested for the observed differences in age composition were: Variation with latitude in the natural span of life; differences in fishing intensity; fluctuations in the strength of year classes (to account possibly for the shift in the dominant age group from 1931 to 1932). The oldest male kiyi belonged to the VII group and the oldest female was a member of the X group. The possible distorting effects of such factors as gear selection traceable to differences in the mesh sizes of nets fished in 1931 and 1932, selection by nets on the basis of the condition (K) of the fish, and local variations in fishing intensity and hence in the selective destruction of rapidly growing individuals in the fishery were held to be sufficiently great to render doubtful the significance of most of the observed local differences in growth rate. Kiyis from all samples were combined to determine the general growth in length. The growth in weight of the Fox Islands fish, however, was considered separately as these fish were consistently lighter than kiyis of corresponding length from other localities. The Lake Michigan kiyi grows slowly, with the females growing slightly more rapidly than the males. The grand average calculated lengths indicated, for example, that the females did not attain a total length of 10 inches until the fifth year of life or the males until the sixth. Similarly, the calculated weight of 4 ounces was not reached until the fifth or sixth year (with the actual time varying with sex and locality). The season's growth of the kiyi probably begins sometime in May and most or all of the growth is completed by the end of August. The calculated lengths of the age groups exhibited large discrepancies that differed from “Lee's phenomenon” as ordinarily observed in that the data for the later rather than the earlier years of life were affected most severely. Chief among the factors held responsible for these discrepancies were gear selection and the selective destruction of the more rapidly growing individuals in the fishery. Errors inherent in the (direct-proportion) method of computing growth from scale measurements were considered to have been unimportant. The Lake Michigan kiyi exhibits growth compensation–the tendency for the smaller of the young fish to have the more rapid growth in the later years of life. Comparisons with the average lengths and weights of the age groups of the Lake Ontario kiyi given by Pritchard (1931) indicated the Lake Michigan fish to be the larger at the earlier ages (age-groups II and III) and the smaller at the later ages (age-groups IV to VI). The length-frequency distributions of the age groups exhibited extensive overlap. As many as eight age groups were represented in a single centimeter interval of length. The length frequencies and average lengths of all fish collected, arranged according to the mesh sizes of the gill nets by which they were captured, revealed that the selective action of these nets in the taking of kiyis was much more obvious in the numbers of fish in the catch than in their average size. As an illustration, in 1930–1931, the 2 3/4-inch mesh nets took fish that were only 0.1 inch longer than those in 2 1/2-inch meshes but captured less than one fourth as many. Gill nets fished in northern Lake Michigan in 1932 captured kiyis that averaged 0.2 to 0.4 inch longer than those taken in the same meshes in southern Lake Michigan in 1930–1931. Because of the more slender form of kiyis from the northeastern island region of Lake Michigan, data on the general length weight relationship were compiled separately for fish of that area and for those of the great central basins of the lake. In both regions the weight increased to a power slightly greater than the cube of the length. Available information on condition indicated that the coefficient (K) was higher in August and early September than in May, June, and July. Condition declined from early September to October and early November–the latter period the time of most active spawning. Spawning itself was accompanied by an additional loss of about 12 per cent of the body weight of females and of somewhat less than 2 per cent of the weight of males. Analysis of the variations of K within a group that was homogeneous with respect to age, sex, maturity, and time of collection revealed that a net of a particular mesh size tends to take the heavier of the shorter fish and the lighter of the longer fish within its range of effectiveness. Among fish of the same length the values of K tended to increase with increase in the mesh size of the nets employed for their capture. Practically all fish in the samples were mature (only 11 immature in more than 6,000). These “immature” fish were probably “non-functional” since all of them approached or exceeded the average length of the mature kiyis. Females were strongly predominant in the collections at all seasons but were relatively more plentiful during the summer (90 per cent of the total) than during the spawning period (75 per cent). Possible factors contributing to this predominance of females and to the change in the sex ratio at the spawning season were discussed. A decrease in the relative abundance of males with increase in age appears to be characteristic of the kiyi. This decrease indicates a differential mortality of th sexes (greater relative destruction of males in the spawning period when they are unusually abundant or a greater natural mortality rate for the males). Current fishery regulations on mesh size and closed seasons afford the kiyi good protection but offer no guarantee against depletion from too intensive fishing.

Transactions of the American Fisheries Society

Standardization of methods of expressing lengths and weights of fish

Fishery workers in the United States and Canada are unable to think readily in terms of the metric system of weights and measurements. Even long experience does not make it possible to form a clear idea as to the actual size of fish for which lengths and weights are given in metric units, without first converting to the English system. A more general adoption of the English system of weights and measurements in fishery work is recommended. The use of English units exclusively is suggested for articles of a popular or semi-popular nature, but in more formal publications the key information, at least, should be recorded in both systems. In highly technical papers metric units alone may prove satisfactory. Agreement is also lacking as to which length measurement of fish is suited best for uniform adoption. The total length is recommended here for the reason that it is the only measurement that includes all of the fish. This length is defined as the distance from the tip of the head (jaws closed) to the tip of the tail with the lobes compressed so as to give the maximum possible measurement.

Transactions of the American Fisheries Society