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Ralph Hile

Publications and source records attributed to Ralph Hile.

At least 37 records · Page 2Linked to original sources
USGS1952

Twenty five years of Federal fishery research on the Great Lakes

The major purpose of this publication is to present an annotated bibliography of papers resulting from Federal investigations on the Great Lakes fish and fisheries since the formal initiation of a continuing research program by the Fish and Wildlife Service. It is believed that this purpose can be served best by prefacing that bibliography with a brief account of the origins of Great Lakes Fishery Investigations, of the circumstances that have guided their course, and of the scientists who have participated in the several studies.

Special Scientific Report - Fisheries↗
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↗
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↗
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&ndash;1894. The general level of yield was much lower but relatively stable in 1895&ndash;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&ndash;1908) Huron proper&ndash;1,749,000, Georgian Bay (including the North Channel)&ndash;2,475,000, Canadian total&ndash;4,224,000; (1909&ndash;1922) Canadian total (no data for regions within the lake)&ndash;3,753,000; (1923&ndash;1939) Huron proper&ndash;1,600,000, Georgian Bay&ndash;1,996,000, Canadian total&ndash;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&ndash;1908 and on production, fishing intensity, and the abundance of fish on the grounds in 1929&ndash;1946. The order of the districts with respect to their percentage contribution to the average annual production was the same in 1891&ndash;1908 and 1929&ndash;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&ndash;1908 accounted for only 56.2 percent in 1929&ndash;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&ndash;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&prime;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, &hellip;) cannot be evaluated accurately. It was determined, however, that the collapse of the whitefish fishery in the middle and late 1930&prime;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&ndash;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&ndash;1946 was lower and was decreasing much more rapidly than was abundance. PDF

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↗
USGS1948

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↗
USGS1947

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&ndash;39 fathoms and were scarce at greater depths (three to four times as abundant, however, at 50&ndash;69 fathoms as at 40&ndash;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&deg;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&ndash;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↗
USGS1947

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↗
USGS1946

The whitefish fishery of Lakes Huron and Michigan with special reference to the deep-trap-net fishery

This study of the whitefish fishery of Lakes Huron and Michigan includes: (1) a review of the available statistics of production, 1879-1942; (2) a detailed analysis of the annual fluctuations in the production and abundance of whitefish and in the intensity of the whitefish fishery in the State of Michigan waters of the lakes, 1929-1942, with special reference to the effects of fishing with deep trap nets; (3) an account of the bathymetric distribution and vertical movements of whitefish and certain other species; and (4) a report of field observations made in 1931 and 1932, as related particularly to the destruction of undersized whitefish by pound nets and deep trap nets. The main body of the manuscript and appendices A, B, and C, completed in March 1942, contain statistics through the year 1939. Since that time, records for the years 1940-1942 have become available. Because these additional data did not alter any of the conclusions of the manuscript but actually strengthened them, it was not deemed justifiable to expend the considerable amount of time and money that would be required to revise the study. The 1940-1942 records are therefore presented in appendix D. From a relatively high production in the earlier years of the period, 1879 to 1942, the yield of whitefish declined to a lower level about which the catch fluctuated until the late 1920's and early 1930's when a general increase in production occurred. This recent increase was higher and the subsequent decline more severe in the Michigan waters of Lake Huron than in other areas.

Lake Huron, Lake Michigan↗
USGS1942

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↗
USGS1941

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↗