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Leonard S. Joeris

Publications and source records attributed to Leonard S. Joeris.

6 recordsLinked to original sources
USGS2003

A horizontal sampler for collection of water samples near the bottom

The need to obtain adequate water samples immediately above a lake bottom or at a precisely defined depth is not new. The problem is of particular concern in a large section of central Lake Erie, where dissolved oxygen concentration may be reduced to 1 ppm or less in the hypolimnion and where the metalimnion frequently extends to or within 30 or 60 cm of the bottom (Becton 1963; Cam 1962).It is impossible to sample the hypolimnrtic waters satisfactorily with the usual Nanscn, Kemmerer, and Frautschy bottles (Carr 1962). Although the 500-ml sampler described here was designed, constructed, and used extensively and successfully to meet the particular problem in Lake Erie, it should be equally useful in a varirty of situations.

Limnology and Oceanography↗
USGS1965

Automatic feeder for small fish held in tanks

The Northville (Michigan) Biological Station has been a center for study of the developmental morphology of coregonid fishes. This work requires the production of numerous individual series of lake herring, lake whitefish, and several species of chubs from parent fish of positively known identity. The offspring of individual pairs or groups of fish must be held in individual tanks from the time they hatch until they reach maturity. One of the important problems in this project has been the poor growth of most fish. Though some have grown well, their growth has been less than that of the same species in nature, and a few fish from each hatch have grown very slowly. Irregularity of feeding may contribute to the slow growth of laboratory fish. The hatchery caretaker feeds them several times during his 8-hour workday, but they must go without food during the remaining 16 hours. The high metabolic rate of small fish, however, appears to make them strongly inclined toward almost continual feeding. Belief that greater, more regular food consumption would result from a mechanical feeder providing a continuous supply of food over a longer period of the day led to development of the equipment described in this paper.

Progressive Fish-Culturist↗
USGS1963

The movement, heterogeneity, and rate of exploitation of walleyes in northern Green Bay, Lake Michigan, as determined by tagging

The Michigan waters of northern Green Bay are an important center for commercial and sport fishing. This 400-square-mile area has supported a commercial fishery for many years but the development of the intensive sport fishery is more recent, mostly since World War II. The commercial fishery is based on several species, whereas anglers are particularly interested in the walleye, Stizostedion v. vitreum . Broad objectives of tagging studies initiated in September 1957 were to obtain information on the heterogeneity, movement, and exploitation of the walleye population of northern Green Bay. The statistical data on the commercial fishery are very sound but other information on the Green Bay walleye has been sketchy.

Conference Paper↗
USGS1957

Structure and growth of scales of yellow perch of Green Bay

The appearance of the scales of yellow perch differs with the location on the fish's body. Comparison of scales of Green Bay perch taken above and below the lateral line reveals the former to have more sharply defined circuli and to exhibit fewer false annuli and less of the shading that impedes accurate assessment of age. Estimates of age from modes in length-frequency distributions and from scale readings were the same for age-groups O, I, and II. Older age groups could not be detected in length distributions, but the similarity of all annuli makes it acceptable to conclude that the annulus is in fact a year-mark at ages beyond the II group. Scales of yellow perch may exhibit new growth in the latter part of May whereas others may not have started growing even in late July. The time of annulus formation varies with calendar year, with age (new growth starts earlier in the younger fish), and possibly with locality. Ages usually can be read from scales collected during the period of annulus formation, but occasionally difficulties are encountered. For larger yellow perch the relation between fish length and the radius of key scales was described by a straight line with a 2-inch intercept on the length axis when the scales were taken above the lateral line and by a straight line through the origin when the scales came from below the lateral line. Lengths calculated from both relations were inaccurate for small fish. Tables of corrections are given, based on the body-scale curves for small perch. The body-scale relations (determined from the same key scale) were similar for Lake Erie and Saginaw Bay perch but both differed sharply from the relation in the Green Bay populations. Good procedure requires high consistency in the field as to the point on the fish's body from which scale samples are taken and also a careful determination of the body-scale relation in each population studied.

Transactions of the American Fisheries Society↗
USGS1953

Technique for the application of a streamer-type fish tag

Principal features of the technique are: attachment of the plastic tag by means of a nylon-thread loop prepared in advance of field work; use of a curved surgical needle with cutting edge and a split eye for application of the tag. The procedures for splitting the needle's eye and for applying the tag are described and illustrated by a series of photographs.

Transactions of the American Fisheries Society↗