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USGS1948

The value of certain drugs, especially sulfa drugs, in the treatment of furunculosis in brook trout, Salvelinus fontinalis

Furunculosis of salmonoid fishes is a dread epizootic disease caused by a general infection by Bacterium salmonicida. In this experiment, treatment was tried with sulfonamides and another drug, “furacin” or “2–20–99” (new drug). The four treatments first used were: (1) sulfamerazine, (2) sulfathiazole, and (3) furacin, each administered by being mixed with the food; and (4) furacin added to the water of the troughs. For assignment of treatments, the troughs containing fingerling brook trout, approximately 8 months old and running 30 to the pound, were grouped in four blocks of five troughs–three blocks of fingerlings with furunculosis, and one block of fingerlings of similar age and size but free from this disease. In each block, one trough received no medication. The various treatments were assigned to troughs by random selection. The block of healthy fish was to test for possible serious ill effects from any of the treatments, and was located some distance from the infected fish. Treatments were begun August 30, 1945, and those involving sulfamerazine and sulfathiazole were continued through 25 days. The furacin treatments, less promising than the sulfonamide treatments, were replaced by sulfanilamide and sulfadiazine, each in the food, on the sixteenth day. Furacin in the water was not beneficial but furacin in the food had some helpful effect. Results with sulfanilamide and sulfadiazine were not encouraging. Sulfathiazole seems to have been more beneficial than furacin, but decidedly less effective than sulfamerazine. The improvement with sulfamerazine was impressive. Mortality dropped rapidly within a few days, generally was light after a week, and within 2 weeks almost completely stopped. Through 25 days, the loss was 17 percent, as compared with 50 percent among the infected lots not receiving medication. The data indicate that 8 grams of sulfamerazine per day per 100 pounds of fish is sufficient, and that a considerably lower dose is at least beneficial. Until further information is available, 8 grams of sulfamerazine per day per 100 pounds of fish, to be continued for at least 6 days after mortality stops, is recommended.

Transactions of the American Fisheries Society↗

USGS1948

Turbidity as a factor in the decline of Great Lakes fishes with special reference to Lake Erie

Fish live and thrive in water with turbidities that range above 400 p.p.m. and average 200 p.p.m. The waters of the Great Lakes usually are clear except in Lake Erie where the turbidities of the inshore areas averaged 37 p.p.m.; the turbidities of the offshore waters averaged less. Lake Erie waters were no clearer 50 years ago than they are now. In fact, the turbidity values are less now than they were in the earlier years; the annual average of the inshore waters dropped from 44 p.p.m. before 1930 to 32 p.p.m. in 1930 and later, and the April-May values decreased from 72 p.p.m. to 46 p.p.m. Any general decline in the Lake Erie fishes cannot be attributed to increased turbidities. Furthermore, these turbidities averaged well below 100 p.p.m. and, therefore, were too low to affect fishes adversely. Turbidity in the open waters of Lake Erie is primarily the result of wave action induced by winds. River discharge is a minor factor even in the western end of the lake. Other probable factors are plankton, the eastward movement of the water mass, currents, seiches, and possibly bacteria. Wave action is undoubtedly the dominant agency in soil erosion along the shores of all of the Great Lakes. No evidence exists that fluctuations in the abundance of zooplankton, the basic food of fishes, and of the fishes themselves are positively correlated in Lake Erie or that the plankton crop in this lake is ever in short supply. On the contrary, all available evidence shows that Lake Erie is comparatively rich in plankton and that the western end in spite of its turbidity is richer than the eastern. Some factor other than turbidity dominates the basic productivity of western Lake Erie. With respect to turbidity Lake Erie has not become less suitable for fishes. This conclusion also receives support from the study of the fishes themselves. It was demonstrated that the growth of the western Lake Erie fishes compared very favorably with that of fishes in the other Great Lakes or similar waters. It was shown further that the known occurrence of relatively strong year classes in this lake was not consistently associated with low turbidities and conversely that the known low turbidities of the Lake Erie waters were not always accompanied by large year classes. Also, contrary to the “turbidity theory,” certain clean-water varieties, such as the walleye, have increased tremendously in recent years in Lake Erie, whereas the supposedly turbid-water forms, such as the sauger, have decreased in abundance. Reference was made to Doan's work, wherein he attempted to show correlation between turbidity and abundance for several species of Lake Erie fish but failed to do so except for the sauger where he reported a positive correlation. With respect to the productivity of fishes Lake Erie ranks first among the Great Lakes, and the western end in spite of its greater turbidity surpasses the eastern. As judged by certain accepted standards of water suitability, Lake Erie ranks high, and the western end again surpasses the eastern. Finally, it was pointed out that fishes which inhabit the clear waters of the Great Lakes declined as well as those which live in the more turbid waters and that turbidity, therefore, cannot be a factor in the depletion of all Great Lakes fishes. Furthermore, the reduction in abundance repeatedly has been associated with increased fishing intensity. All of the evidence indicates, then, that soil erosion on farms and the turbidity of the water were not major factors, if operative at all, in the decline of Great Lakes fishes and that they did not make Lake Erie unsuitable for fish life.

Transactions of the American Fisheries Society↗

USGS1949

Trends in the lake trout fishery of Lake Huron through 1946

The production of lake trout, Cristivomer namaycush (Walbaum), in the United States waters of Lake Huron was highest in the earliest years for which there are statistical records, averaging 2,362,000 pounds in 1879–1894. The general level of yield was much lower but relatively stable in 1895–1939, during which period the catch averaged 1,685,000 pounds. The most recent years have seen a rapid and calamitous decline in the output; setting a new record low each year, the take decreased from 940,000 pounds in 1940 to only 38,000 pounds in 1946. The production of lake trout in the Canadian waters of Lake Huron was generally low from 1867 up to about 1883, apparently because the fishery was then in the process of development. After 1882 the yield was relatively high for 26 years and then fell away progressively as the following averages of production in pounds for different periods show: (1883–1908) Huron proper–1,749,000, Georgian Bay (including the North Channel)–2,475,000, Canadian total–4,224,000; (1909–1922) Canadian total (no data for regions within the lake)–3,753,000; (1923–1939) Huron proper–1,600,000, Georgian Bay–1,996,000, Canadian total–3,596,000. During more recent years the catch fell from 1,038,000 pounds in 1940 to 29,000 pounds in 1946 in Huron proper, from 1,688,000 to 702,000 pounds in Georgian Bay, and from 2,726,000 to 731,000 pounds in all Canadian waters. The tremendous decreases in production that have occurred in all parts of Lake Huron in recent years are generally believed to have been caused by a reduction in the abundance of lake trout resulting from attacks by the sea lamprey, which has become established and has multiplied rapidly in the upper Great Lakes. Data are available on the production of lake trout in six local regions or statistical districts of the United States waters of Lake Huron (boundaries shown in Fig. 1) in 1891–1908 and on production, fishing intensity, and the abundance of fish on the grounds in 1929–1946. The order of the districts with respect to their percentage contribution to the average annual production was the same in 1891–1908 and 1929–1943. Certain changes occurred, nevertheless, in all percentages. The northern districts (H-1, H-2) which contributed 70.3 percent of the take in 1891–1908 accounted for only 56.2 percent in 1929–1943 whereas the central (H-3, H-4) and southern (H-5, H-6) districts which yielded 18.7 and 11.0 percent, respectively, in the former period contributed 25.5 and 18.3 percent in the latter. The six districts were similar in 1929–1946 in that in all of them (1) most of the years of highest output and of most intensive fishing occurred in the early to middle 1930′s and (2) the earlier high levels were followed by declines that ultimately reduced production and fishing intensity to insignificance. The same (earlier high values followed by a decline) held for the abundance of lake trout in the northerly five districts, but the trends of fluctuation in the abundance in H-6 were opposite those in other areas. On the whole, the abundance of lake trout appeared to have little effect on fishing intensity for the species. Only in H-1 did the two exhibit significant positive correlation whereas in H-6 they showed highly significant negative correlation. Most of the factors that may counteract the expected influence of abundance on fishing intensity (economic conditions, weather, …) cannot be evaluated accurately. It was determined, however, that the collapse of the whitefish fishery in the middle and late 1930′s most probably exerted a significant depressing effect on the intensity of the gill-net fishery for lake trout in those districts (H-1, H-4, H-6) in which the two species are ordinarily captured together. The estimated abundance of lake trout in the United States waters of Lake Huron (all districts combined) had reached an extremely low level in 1946 (24 percent of the 1929–1943 average), and the complete collapse of the fishery in late years is a matter of record. The rate of decline in abundance, however, was much less rapid than the spectacular decreases in production might suggest. Although each year beginning with 1940 saw a new record low yield, the abundance was still 87 percent of average in 1942 and did not drop below 70 percent until 1944. This seeming paradox is explained by the fact that relative to average conditions, fishing intensity in 1941–1946 was lower and was decreasing much more rapidly than was abundance. PDF

Transactions of the American Fisheries Society↗

USGS1949

The age, growth, and distribution of the longjaw cisco, Leucichthys alpenae Koelz, in Lake Michigan

The longjaw (Leucichthys alpenae) was found at all of the 109 stations fished in the open lake during 1930–1932 and at 29 of the 32 stations in Green Bay in 1930 and 1932. Koelz (1929) found the longjaw at 35 localities, 33 of which were different from those fished in 1930–1932. The species was most abundant in water with a depth of less than 70 fathoms, but was found as deep as 97 fathoms. The longjaw was estimated to be about 4 1/3 times as abundant along the east shore of southern Lake Michigan as along the west shore in 1930 and 1931. The abundance along the east shore in 1930–1931 was estimated to be approximately equal to that in northern Lake Michigan in 1932. The best explanation for the relative scarcity of L. alpenae along the west shore is that a more intensive fishery, with smaller sizes of mesh, was operating on a separate population. The length distribution of 6,954 specimens taken in 1930–1932 revealed little difference in frequencies between the sexes, the samples taken in each of the years 1930 and 1931, or the fish taken on the two shores of the southern region. The individuals caught in 1932 from northern Lake Michigan averaged 12.5 inches, total length, and were from 1.0 to 1.3 inches longer than fish taken by the same sizes of mesh from the southern area in 1930–1931. Of the 378 longjaws whose ages were determined, 320 were taken during the summer of 1923 in northeastern Lake Michigan, and 58 were secured off Grand Haven, Michigan, in November 1928. The age groups represented ranged from II to IX. Age-group IV dominated in the 1923 samples making up 53.8 percent of the total, and age-groups III and V with 20.9 and 10.6 percent, respectively, were the next best represented groups. The III group dominated the 1928 collection with 55.2 percent of the total, and age-groups IV and II, that were represented by 31.0 and 12.1 percent, respectively, were the only other well represented groups. The sexes grew at approximately the same rate. A total length of 11.1 inches and a weight of 6.4 ounces were reached at the end of 4 years of growth by the longjaws in northeastern Lake Michigan. The fish from Grand Haven averaged 11.0 inches, total length, and 6.1 ounces at the end of 4 years. Growth in length was most rapid during the first year and decreased continuously thereafter through the fourth year (fifth year in 1928). The increments in length of the 1923 fish during the fourth through the eighth years were approximately the same. Growth in weight of the fish taken in 1923 was computed to be most rapid following the fifth year of life. Growth compensation occurred among the longjaws of Lake Michigan. The major part of the annual growth in length had taken place before June 15, 1923. Although the empirical data on the length-weight relationship of 5,314 fish failed to fall along a simple curve, it is believed that the following equation is the one best suited to computing the weight of the longjaw: W = 0.96288 × 10 −5 L 3.06060 . The coefficient of condition (K) of all longjaws increased as the standard length increased to 194 millimeters. The values then remained high up to 225 millimeters but decreased progressively until the fish reached a length of 265 millimeters. The coefficient changed little at fish lengths of 265 to 284 but began to increase again at 285 millimeters. Condition was best in 1931 and poorest in 1932. The individuals of both sexes were in the poorest condition during some month previous to August each year. Although the females were somewhat heavier in relation to their length than the males in practically all months, the weighted averages of K for all males and all females were almost identical (1.30 for the males and 1.31 for the females). The sex ratio was determined from 7,457 individuals taken in 1930–1932 and 373 of the 1923 and 1928 specimens whose ages were determined. The percentage of females was relatively low in May 1931 and relatively high in October, but in the other months it remained more or less constant. In 1932 the females tended to become relatively less abundant in each month from April through September. There was little difference between the relative abundance of the sexes in 1930 and 1931 (72.4 percent females in 1930 and 67.5 percent in 1931). The consistently slightly higher percentage of females each month in 1932 (average of 80.6) probably represents a difference between populations. The relative abundance of the males decreased as the age increased. A natural differential mortality is suggested as the cause for the more rapid disappearance of the males. Females may contain ripe eggs as early as July 9, and some females may spawn as early as October 16 despite the fact that the spawning season is in November.

Transactions of the American Fisheries Society↗

USGS1949

A definition of depletion of fish stocks

Attention was focused on the need of a common and better understanding of the term depletion as applied to the fisheries in order to eliminate if possible the existing inexactness of thought on the subject. Depletion has been confused at various times with at least ten different ideas associated with it but which, as has has heen pointed out, are not synonymous at all. In defining depletion we must recognize that the term represents a condition and must not he confounded with the cause (overfishing) that leads to this condition or with the symptoms that identify it. Depletion was defined as a reduction, through overfishing, in the level of abundance of the exploitable segment of a stock that prevents the realization of the maximum productive capacity.

Transactions of the American Fisheries Society↗

USGS1946

Relative toxicity of suspension and oil formulations of DDT to native fishes in Back Creek, West Virginia

On July 23, 1947, a 1‐mile section of Back Creek, treated the previous year with a DDT suspension with little damage to fish, was re‐treated with an oil spray at the same rate (1 pound per acre). The oil spray killed about six times as many fish as the suspension formula. Fish began dying within 3 to 4 hours after treatment, whereas several days elapsed before mortality began with the suspension formula in 1946. In addition to larger numbers of the minnow species, some adult game fish were killed. Losses of fish were not as great below the sprayed section as when a suspension formula was used, probably because a good part of the DDT was drifted ashore by breezes or by water currents. Some species of fish such as bluntnose minnows (Hyborhynchus notatus), chub suckers (Erimyzon oblongus), and pickerel (Esox niger), although numerous, were relatively unaffected. Considerable mortality of largemouth bass (Micropterus salmoides) and bluegill sunfish (Lepomis macrochirus) occurred in liveboxes placed in the sprayed section, particularly at the lower stations. Largemouth bass nearly 4 inches long survived at a station where 54.0 percent of the 2‐inch bass were killed. This fact supplied some positive evidence that fish of larger size are better able to withstand DDT.

West Virginia↗

USGS1949

Dosage of sulfamerazine in the treatment of furunculosis in brook trout, Salvelinus fontinalis

To determine the most effective dosage of sulfamerazine in the treatment of furunculosis in brook trout, two experiments were run. In the first experiment, yearlings were used and the daily dosage rates were 4, 8, and 12 grams of sulfamerazine per 100 pounds of fish. In the lots treated with sulfamerazine, mortality was brought under control within 15 days and was less than a quarter as high as in the controls. Results with the 4‐gram rate were nearly as good as with the higher rates. Treatment was continued for 10 days or more after mortality dropped to zero, and recurrences were few. A large number of the dead were checked bacteriologically for furunculosis. In the second experiment fingerlings in an early stage of a furunculosis epizootic were used and the daily dosage rates were 2, 4 and 6 grams per 100 pounds of fish. Losses in the controls were extremely heavy, with only 6‐percent survival. Losses were heavy in all lots, but in those treated at the 4‐gram and 6‐gram rates, survival was 10 times as high as in the controls. Mortality declined sooner with the 6‐gram than with the 4‐gram rate, and recurrence was almost eliminated by treatment, at the higher rate, for 10 days after mortality dropped to zero. Discontinuance of treatment as late as 4 days after the discontinuance of mortality was followed by resumption of mortality at a considerable rate. In the treated lots, late dead were small thin fish which evidently had received little food and drug. Dead fish were “spot‐checked” for furunculosis. The recommended daily dosage rate is 6 grams per 100 pounds of fish, to be continued for 10 days after mortality stops and for a total of at least 3 weeks. Other recommendations include: the early elimination of undersized fish; the prompt removal of dead and dying fish; the maintenance of clean troughs and pools; and strict observation of all sanitary measures practiced in the control of infectious diseases.

Transactions of the American Fisheries Society↗

USGS1947

Results of varying the ratio of largemouth black bass and bluegills in the stocking of experimental farm ponds

During the period 1943 to 1946, several combinations of largemouth black bass (Micropterus salmoides) and bluegill (Lepomis macrochirus) were stocked in ponds on the station grounds at Leetown, West Virginia. These ponds were fertilized with 12–5–5, inorganic fertilizer, but when water blooms failed to control the submerged vegetation, sodium arsenite or copper sulfate was occasionally used for this purpose. Bluegill‐bass ratios varying from 8:1 to 15:1 were used. Inventories of ponds showed that approximately 199 pounds of edible fish per acre could be produced annually in well managed ponds at Leetown regardless of the stocking ratio employed. The average size of bluegills varied inversely with the number stocked. The smallest bluegills, produced in the 15:1 bluegill‐bass ratio, averaged about 5.7 inches in fork length, compared with about 6.5 inches from the 8:1 ratio. Largemouth bass failed to make good growth in the 15:1 ratio, averaging only 9.3 inches compared with 10.2 inches in the 8:1 ratio. The fact that in two ponds 71 percent of the largemouth black bass in the original stocking were removed during a brief period suggests that good pond management may include removal of the fish in the same ratio as the original stocking, to assure maintenance of a balance of species.

Transactions of the American Fisheries Society↗

USGS1949

Age and growth of the lake whitefish, Coregonus clupeaformis (Mitchill), in Lake Erie

Although the whitefish has by no means ranked first from the standpoint of production, it has always been an important commercial species in Lake Erie. Trends in the output of whitefish have differed in the United States and Canadian waters of the lake. The 1893–1946 average annual yield of 1,201,000 pounds in the United States was only 38.3 percent of the 1879–1890 mean of 3,133,000 pounds, whereas in Canada the more recent (1907–1946) average annual take of 1,397,000 pounds has been 5.48 times the 1871–1906 mean of 255,000 pounds. The United States fishery was centered in the western part of Lake Erie (61.5 percent of the production in Michigan and Ohio) before 1921 and in the eastern part (62.6 percent in Pennsylvania and New York) in 1921–1946. The eastern part of Lake Erie (east of Port Burwell) dominated the Canadian production in 1900–1909 (65.4 percent) and in 1922–1946 (57.2 percent) but the western end was the more productive in 1871–1899 (79.8 percent) and 1910–1921 (69.7 percent). Ages were determined and individual growth histories calculated from the examination and measurement of the scales of 3,399 Lake Erie whitefish captured off four ports (Sandusky, Lorain, and Conneaut, Ohio, and Erie, Pennsylvania) over the period, 1927–1930. The number of specimens used for the investigation of other phases of the life history varied according to the amount of data available or required. Age-group III was typically (but not invariably) dominant in random samples from gear employed for the commercial production of whitefish (trap nets, pound nets, and large-mesh gill nets). The same age group also dominated most samples of the marketable catch (that is, whitefish that equalled or exceeded the minimum legal weight of 1 3/4 pounds) taken in late summer, autumn, and early winter. Age-group IV, however, was strongest among marketable fish from trap nets in early July although the III group was dominant in the random samples from the same nets. Apparently the members of a year class normally dominate the commercial catch about one year but this year extends over parts of two years of life (latter part of the fourth and early part of the fifth). The oldest whitefish in the collections were in the seventeenth year (age-group XVI). The year classes of 1922 and 1926 were much stronger than average whereas the 1923 year class seems to have been exceptionally weak. No correlation was detected between limnological-meteorological conditions and the strength of the year classes. Whitefish collected off different ports exhibited differences of growth rate that were at times rather large. The distorting effects of such factors as selection on the basis of maturity, annual fluctuations in growth rate (in combination with differences in the year of capture), and gear selection were held to be sufficiently great, however, to render doubtful the real biological significance of the observed variations in growth. Consequently the data for all samples were combined to obtain general growth curves. Female whitefish averaged longer and heavier than male fish of corresponding age. The advantage of the females with respect to calculated lengths tended to increase during the first three years of life and thereafter remained nearly constant at about one-half inch total length (10 millimeters of standard length). The advantages of the females with respect to weight increased consistently from 0.01 pound at the end of the first year to 0.36 pound at the end of the eighth, dropped to 0.32 pound in the ninth year, and increased again to a maximum of 0.47 pound at the end of 12 years. The maximum growth in length (sexes combined) occurred in the first year of life (calculated growth of 6.9 inches, total length). From this value the calculated annual increments declined rapidly to 0.7 inch in the seventh year. The later increments varied irregularly, ranging from 0.7 inch in the eighth and ninth years down to only 0.3 inch in the fifteenth and sixteenth years. The Lake Erie whitefish was a foot long in a little less than 2 years, 18 inches in about 4 years, and 2 feet in slightly under 12 years. At the end of 16 years the calculated length was 25.6 inches. The calculated annual increments of growth in weight increased from 0.10 pound in the first year to a maximum of 0.76 pound in the third. In the succeeding years the increment decreased consistently to 0.33 pound in the twelfth year. The values in the thirteenth to sixteenth years varied irregularly, ranging from 0.22 to 0.34 pound. The minimum legal weight of 1 3/4 pounds was attained toward the middle of the fourth growing season. The Lake Erie whitefish reached the weight of 4 pounds in between 7 and 8 years, and of 6 pounds in about 13 years. At the end of 16 years the calculated weight was 6.87 pounds. Analyses of the annual increments of length revealed that the growth of whitefish captured from the spawning run off Sandusky and Lorain rose from 3.2 percent above the 1924–1930 mean in 1924 to a peak of 15.0 percent above average in 1927 and then declined to a minimum of 25.0 percent below average in 1930. There is evidence that these annual fluctuations in growth rate were correlated negatively with fluctuations in the turbidity of the water off Erie, Pennsylvania (to our best knowledge the whitefish spends the summer months in the eastern part of the lake), in certain months (especially May and June) and/or correlated positively with the amount of rainfall in July and August at the same locality. Comparisons with data on the growth of the Lake Huron whitefish revealed that Lake Erie fish were the longer during the first 5 years of life and the shorter at the end of the sixth and later years. The Lake Huron whitefish did not, however, gain the advantage in weight until the seventh year. Whitefish grew much more slowly in both length and weight in Lake Ontario than in either Lake Huron or Lake Erie. The weight of the Lake Erie whitefish increased to the 3.1523 power of the length. Agreement between empirical weights and those computed from the length-weight equation was reasonably good at lengths represented by fair numbers of fish. The total length corresponding to the minimum legal weight of 1 3/4 pounds was calculated as 16.9 inches. The rather limited data on the monthly fluctuations in condition indicated that the coefficient K of immature fish declined continuously from August to December. A similar though less pronounced decline of K of mature fish occurred from August to October. At spawning in November and December, female whitefish lost an additional 11 percent of their body weight. No loss of weight at spawning could be demonstrated for the males. The available records indicated the relative abundance of the sexes to be approximately equal in samples collected in the summer and early autumn. Males were strongly predominant (78.6 percent), however, in spawning-run samples. In these collections the percentage of males decreased markedly with increase in age. No trend could be detected in the variation of the sex ratio within the spawning season over the period of time (nearly 4 weeks) for which there were records. Although exceptional individuals of either sex may mature at the end of 2 years of life (age-group I) male whitefish do not mature in appreciable numbers until the end of the third year (age-group II) or females until the end of the fourth (age-group III). Apparently most or all males are mature as age-group III, but there is evidence that considerable numbers of females (possibly a majority) are first mature as members of the IV group (end of fifth year of life). Whether Lake Erie whitefish are ever immature as the V group or older is not known. Spawning commenced during the second week of November and was continuing actively at the time of collection of the last samples at the end of the first week of December

Transactions of the American Fisheries Society↗

USGS1949

Response of brook, rainbow, and brown trout to various dosages of sulfamerazine

During experiments in 1945 and 1946 in which sulfamerazine in the food was found to be effective in the treatment of furunculosis in brook trout (Salvelinus fontinalis), it was observed that fish grew faster on untreated food and that when the dosage rate was heavy they did not eat all the food and showed a dislike for it. To determine the effect of sulfamerazine treatment on growth and to learn whether the drug injures various trout species, brook trout and rainbow trout (Salmo gairdnerii) were tested in 1946 and brown trout (Salmo trutta) in 1947. The daily dosage rates chosen were 0, 5, 10, and 15 grams of the drug per 100 pounds of fish (0, 11, 22, 33 grams per 100 kilograms). It was observed from this experiment that: (1) sulfamerazine was not lethal; (2) the drug had no apparent injurious effect; (3) retardation of growth was caused by reduced consumption of food containing the drug; (4) there was great variation among the three species of trout in their response to sulfamerazine, e.g., the growth of rainbow trout was not affected, growth of brook trout was reduced by heavier dosage rates, and growth of brown trout was stopped by 5‐gram or greater dosage rates; (5) hemoglobin and number of erythrocytes increased in brown trout treated with sulfamerazine in the food; (6) a very small dosage, begun in time, appears to be sufficient to control furunculosis in brown trout.

Transactions of the American Fisheries Society↗

USGS1950

A nomograph for the computation of the growth of fish from scale measurements

Directions are given for the construction and operation of a nomograph that can be employed for the computation of the growth of fish from scale measurements regardless of the nature of the body-scale relationship, so long as that relationship is known. The essential feature of the nomograph that makes rapid calculations possible is a ruler on which the graduations are in terms of length with the distance of each length graduation from the O graduation equal to the corresponding theoretical scale measurement. The chief advantage of the nomograph lies in the fact that the calculation of the lengths for all years of life of an individual fish requires only one setting of the single movable part.

Transactions of the American Fisheries Society↗

USGS1950

Various sulfonamide treatments of furunculosis in brook trout, Salvelinus fontinalis

Sulfamerazine, sulfamethazine, sulfathiazole, and sulfamerazine alternated at 4‐day intervals with sulfathiazole, were compared in the treatment of furunculosis among yearling and fingerling brook trout at the Leetown Station of the U. S. Fish and Wildlife Service, Kearneysville, West Virginia, in 1947. The daily dosage rates were: for sulfamerazine and sulfamethazine, 6 grams per 100 pounds of fish (13.2 grams per 100 kilograms); for sulfathiazole, 12 grams per 100 pounds. The drugs were mixed thoroughly with the food. The courses of the epizootics were very different in the two age groups. With yearlings, mortalities were as follows: controls, 100 percent; sulfathiazole, 75 percent; sulfamethazine, 62 percent; sulfamerazine‐sulfathiazole, 43 percent; sulfamerazine, 29 percent. With fingerlings, treatment was initiated sooner after the onset of the disease. Although mortality was finally heavy in the fingerling control, sulfonamide therapy was very much more effective and losses correspondingly less severe. Mortalities were as follows: controls, 90 percent; sulfathiazole, 11 percent; sulfamerazine, 8 percent; sulfamerazine‐sulfathiazole, 6 percent; sulfamethazine, 5 percent. Sulfathiazole was markedly inferior to sulfamerazine. Sulfamethazine showed sufficient promise to warrant further trial. Sulfamerazine still seems the best for an acute infection and the drug most suitable for the treatment of furunculosis in brook trout. Important was the revelation of the extreme difference in the courses of the epizootics and the apparent correlation of effectiveness of treatment with the type of epizootic. However, prompt initiation of treatment may largely explain the great effectiveness of the various drugs with the fingerlings.

West Virginia↗

USGS1950

A contribution to the etiology of ulcer disease of trout

During the fall of 1947 and the late summer of 1948, outbreaks of ulcer disease occurred among brook trout fingerlings at the Leetown station and other hatcheries. From the ulcers, blood, and kidneys of the diseased trout were isolated bacteria which could be successfully cultivated only on media to which blood or fish‐tissue extract had been added. Some characteristics of these bacteria are described. In a series of inoculation experiments, brook, brown, and rainbow trout were infected with pure cultures of the isolated bacteria. When the trout used for these tests were free from a latent infection of B. salmonicida, ulcer disease could be reproduced and the bacteria reisolated in pure culture from the inoculated fish. On the basis of the information on hand, it is believed that the isolated bacteria belong to the genus Hemophilus.

Transactions of the American Fisheries Society↗

USGS1951

Tissue levels of various sulfonamides in trout

Studies were made on the tissue levels of sulfonamides in trout. The tissue concentrations of sulfamerazine were determined in brook trout given various doses of this drug. It has been found also that there exists a relationship between the rate of feeding, depending on the size of trout, and the tissue concentration of sulfamerazine. The level of sulfamerazine rose much faster and higher in blood and liver than in kidney and muscle. However, after the treatment was discontinued sulfamerazine level in all tissues dropped within 3 days to about 1 milligram percent. From the tested sulfonamides, sulfanilamide was absorbed fastest and produced highest tissue concentration. Sulfamerazine and sulfamethazine gave similar tissue levels, but the tissue concentration rose faster with sulfamerazine. Sulfadiazine and sulfaguanidine reached lower tissue levels. The tissue level of sulfathiazole was less than 1 milligram percent and sulfathalidine and sulfaquinoxaline were not absorbed from the intestine at all.

Transactions of the American Fisheries Society↗

USGS1951

Status of the lake trout fishery in Lake Superior

The production of lake trout in the United States waters of Lake Superior was low (only 1,465,000 pounds) in 1879, the first year for which there is a record. Expansion of the fishery must have started soon thereafter, for the take was 3,488,000 pounds in 1885, the next year for which we have statistics, and averaged 3,416,000 pounds in 1885–1892. The years after 1892 can be divided readily into three general periods with average yields as follows: 1893–1907–4,599,000 pounds; 1908–1925–2,168,000 pounds; 1926–1949–3,049,000 pounds. A take of 3 million pounds can be held as “normal” in the modern fishery. During the three periods just listed the percentage contributions of the individual states to the United States total (as computed from the averages for individual periods) ranged from 65.1 to 71.5 for Michigan, 17.5 to 25.6 for Wisconsin, and from 9.3 to 11.0 for Minnesota. In the Canadian (Province of Ontario) waters of Lake Superior the average annual output of lake trout rose from 309,000 pounds in 1871–1882 to 900,000 pounds in 1883–1893, 1,567,000 pounds in 1894–1903, and 2,189,000 pounds in 1904–1918. This last period of relatively high yield was followed by two intervals of successively lower average catches–1,691,000 pounds in 1919–1929 and 1,395,000 pounds in 1930–1949. For the combined United States and Canadian waters of Lake Superior the general trends in the production of lake trout can be described by the following averages: 1879–1,653,000 pounds: 1885–1892–4,325,000 pounds; 1893–1907–6,236,000 pounds; 1908–1949–4,403,000 pounds. The short‐term fluctuations of production during the more recent years give evidence of periodicity in the output of lake trout in Michigan, Ontario, and in the entire lake. Furthermore, these periodic fluctuations tended to be similar in Michigan and Ontario waters. The coefficient of correlation (r) between production in Michigan and Ontario in 1920–1949 (after elimination of trend in the statistics for both areas) had the significant value of 0.456. This correlation suggests that Michigan and Ontario fishermen exploit a common stock or stocks subject to similar fluctuations. Statistics on the production of lake trout in 5 of the 6 statistical districts of the State of Michigan waters of Lake Superior (see Fig. 2 for boundaries of the districts) in 1885 suggest that in most areas the fishery was then in the process of development. Even in 1891–1908 when the general level of production was high, there is evidence that during certain periods the catch in some areas was influenced strongly by factors (such as accessibility to market) other than the natural productivity of the waters. Comparisons of the average annual output of lake trout in the individual districts in 1891–1908 and 1929–1943 (the base period for our modern statistical analysis) reveal an enormous decrease in the Whitefish Bay region (S‐6) from 916,000 pounds in 1891–1908 to only 177,000 pounds in 1929–1943, a substantial drop (from 655,000 pounds to 385,000 pounds) in the Marquette‐Munising area (S‐4), and a small decrease (from 141,000 pounds to 138,000 pounds) in the Black River‐Ontonagon district (S‐2). Among the remaining districts the average yearly take increased from 322,000 pounds in 1891–1908 to 354,000 pounds in 1929–1943 at Isle Royal (S‐1), from 428,000 pounds to 501,000 pounds in the Grand Marais district (S‐5), and from 422,000 pounds to 506,000 pounds in the Keweenaw area (S‐3). These changes in the catch resulted in a westward shifting of production centers. Districts S‐1, S‐2, and S‐3 which together contributed only 30.7 percent of the 1891–1908 catch accounted for 48.4 percent of the take in 1929–1943. The 1929–1949 production in all districts exhibited periodic fluctuations that were characterized by peaks in the middle 1930ˈs and middle 1940ˈs. The indices of abundance or availability as computed from records of the catch of lake trout per unit of fishing effort showed periodic fluctuations in all districts of the State of Michigan waters similar to those of production (the peaks and the intervening minima fell a little earlier in the curves of abundance than in the production curves). For the combined districts the abundance of lake trout, expressed as a percentage of the 1929–1943 mean, stood at 108 in 1929, dropped to 100 in 1931, rose to a 21‐year high of 137 in 1934, decreased to 80 in 1940, increased again to 107 in 1944 and then fell to the 21‐year low of 65 in 1949 (this last decline was interrupted by a small increase in 1947). The 1929–1949 fluctuations in abundance were similar in the 5 mainland districts (S‐2 through S‐6). The coefficients of correlation (r) were significant for all 10 pairings and those for the 4 easterly districts (S‐3 through S‐6) were extremely high (p < 0.001 for all 6 values). Thus we have evidence that the fishermen along the mainland exploit common stocks or stocks in which the factors controlling availability are the same or subject to closely similar fluctuations. The fluctuations in abundance in S‐1 were correlated significantly (p < 0.05) with those in S‐2 but otherwise appeared to be independent of conditions along the mainland. The distinctly cyclic fluctuations that characterized the statistics on production and abundance were much less apparent in the 1929–1949 data on fishing intensity in the State of Michigan districts. In districts S‐3, S‐4, and S‐5 a possible tendency toward a cyclic fluctuation seems to have been obscured by a long‐term upward trend that was becoming stronger toward the end of the 21‐year period. For the combined districts the level of fishing pressure was consistently high after 1943. Over the 6‐year period, 1944–1949, fishing intensity expressed as a percentage of the 1929–1943 mean averaged 142; for the most recent 4 years, 1946–1949 the average intensity index was 151. On the whole, the 1929–1949 production of lake trout in the State of Michigan waters of Lake Superior was unreliable as an indicator of changes in abundance. The coefficient of correlation between the fluctuations of catch and abundance was, to be sure, positive and significant in S‐1 (p < 0.05) and S‐6 (p < 0.01), but in the remaining districts and for the combined districts the values of the coefficient were far below the level of significance. The failure of production to serve better as an indicator of changes in abundance can be attributed to the negative correlation that existed between abundance and fishing intensity (values of r highly significant in every district but S‐6 and for the combined districts). The relationship suggests that fishermen have increased their fishing pressure in order to maintain their production during the recent years of declining abundance. The condition of the lake trout fishery of the State of Michigan waters of Lake Superior must be termed unhealthy and the outlook for the future is not good. Production in 1949 stood at 106 percent of the 1929–1943 mean, but this level of yield was made possible only by fishing intensity that was 162 percent of average; the abundance index in 1949 was only 65. Certainly the stocks of lake trout are in a poor state to withstand the threatened inroads of sea lampreys which have been taken from all parts of Lake Superior and are known to have established spawning runs at least as far west as the Keweenaw Peninsula.

Michigan, Minnesota, Wisconsin↗

USGS1952

Further studies on factors determining tissue levels of sulfamerazine in trout

There is considerable variation in the tissue level of sulfamerazine among individual trout in a treated population. This fact may be the reason why prolonged sulfonamide therapy sometimes fails to free all trout from Bacterium salmonicida. The quantity of food given with a standard dosage of sulfamerazine has a pronounced effect on the tissue concentration of sulfamerazine; the concentration increased when the quantity of food decreased. It appears therefore, that trout should be fed at a rate very closely adjusted to their optimum feeding requirements for the best practical results. The start of treatment with high initial doses of sulfamerazine had no effect on the tissue concentration sustained by the maintenance dosage. The relative distribution of sulfamerazine in various organs and tissues of rainbow trout was about the same as in brown and brook trout. The only difference noticed was the lack of peak levels of short duration between the 8 and 10 days of treatment, which is characteristic for brook and brown trout.

Transactions of the American Fisheries Society↗

USGS1952

Movements of yellow perch marked in southern Green Bay, Lake Michigan, in 1950

To obtain information on the post-spawning movements of yellow perch that spawn in southern Green Bay, Lake Michigan, 4,172 fish caught in drop nets were marked by tagging with monel-metal strap tags attached to the right operculum and 24,799 were marked by clipping off the second or membranous dorsal fin. Marking was done during the period from May 3 to 17, 1950, at six main stations, all located in the southern end of Green Bay. The average length of the tagged perch was 7.3 inches and all fell within the range 5.5–14.4 inches. Most (90.9 percent) of the fish were below the minimum legal length of 8.0 inches. The follow-up procedure consisted of informing commercial and sports fishermen of the program and enlisting their cooperation in watching for marked fish; accounts of the investigation were released through newspapers and descriptive posters were distributed. The personnel connected with the investigation examined catches frequently. The large majority (101 or 79.5 percent) of the 127 tagged perch recaptured in the experimental nets during the marking operations were retaken at the tagging station at which they were released. Of the 108 tagged perch captured by commercial fishermen and anglers following the opening of the season on May 20, 96 were taken by drop nets, 6 by gill nets, and 6 by hook and line. The mean lengths for the three groups were 7.7, 7.1, and 9.25 inches, respectively. All recoveries were made in the Wisconsin waters of Green Bay. Most of the “open-season” recoveries (86 fish; 79.6 percent) were made during the period May 20-May 31. Recaptures during subsequent months were: June–14; July–7; August–none; September–1. Of the 86 perch recaptured May 20–31, 70 were retaken inside and 16 outside the tagging area. The majority (14 of 22) of those recovered after May 31 were retaken outside the tagging area. The average length of the 20 tagged yellow perch recaptured by drop nets (data restricted to fish from a single type of net to avoid bias from gear selectivity) outside the tagging area (8.42 inches) was 0.96 inch greater than the mean length (7.46 inches) of the 76 fish retaken inside the area. This statistically highly significant difference lends support to the belief of commercial fishermen that the larger of the yellow perch that spawn in southern Green Bay move out soon after spawning. The percentage of recapture of tagged perch increased sharply with increase in the size of the fish. Not one of 169 tagged fish less than 6.5 inches long was recovered. The rates of recapture at greater lengths were: 6.5 to 8.9 inches–2.5 percent; 9.0 to 9.9 inches–11.4 percent; 10.0 to 14.4 inches–16.7 percent. Among the several factors suggested in explanation of this relationship, the most important appear to be the lesser ability of the smaller fish to survive the rigors of handling and tagging, greater loss of tags from the smaller fish, and the greater likelihood of overlooking the smaller of the tagged fish in the sorting of the catch. The factors just mentioned and the lack of knowledge of the efficiency of measures taken to obtain records of recoveries preclude the 2.6-percent return of all tagged fish from being accepted as an approximation of the rate of recapture. Neither should the 6.6-percent return of tagged fish of legal size (8 inches and longer) be taken as an estimate of the rate of exploitation. Although 465 fin-clipped perch were recovered in the experimental nets during the marking operations, only 68 of 24,799 fish so marked were recovered after the fishing season opened. All but one of these 68 were retaken near the point of marking. The difficulty of detecting a perch with a missing membranous dorsal is believed to be a major cause of the poor returns from fin-clipped fish. These investigations have demonstrated that for studying migration of yellow perch, tagging is superior to fin-clipping as a method of marking. The technique of the tagging, however, needs to be improved, and better means must be found to trace tagged fish of small size. Furthermore certain small regions in the bay not at present open to commercial fishing must be explored in order to obtain more comprehensive information as to migration.

Transactions of the American Fisheries Society↗

USGS1951

Downstream movement of recently transformed sea lampreys, Petromyzon marinus, in Carp Lake River, Michigan

In order to obtain more precise information concerning the downstream movement of recently transformed sea lampreys, a trapping device was operated in the Carp Lake River, Emmet County, Michigan, from October, 1948, to July, 1951. The period of downstream migration typically extends from the latter part of October to the middle of April. It varies, however, from year to year with climatic conditions. A few migrants usually appear every day during this period but a sudden increase in water level is characteristically accompanied by a surge in downstream movement of newly transformed sea lampreys. This phenomenon is realized principally during the spring floods and often concurrently with autumn rains and mid-winter thaws. A total of 7,969 downstream migrants were taken in the 1948–49 season; 16,235 in 1949–50, and 15,103 in 1950–51. Measurements of representative samples from the total catch of sea lamprey migrants of the 1948–49 and 1949–50 seasons revealed a range in length of 95 to 190 millimeters and an average length of 145 millimeters (3.7 to 7.5 inches; mean –5.7 inches).

Transactions of the American Fisheries Society↗