Stomach contents of 551 young pike (11–152 millimeters in length), 345 small yellow perch, and 431 other fish representing 18 species were examined. All specimens were collected from an area widely used by spawning pike from Houghton Lake, Michigan. Organisms utilized for food by young pike included Entomostraca, insects (chiefly Chironomidae), tadpoles, minnows, darters, and other pike. As pike increased in size they passed through a definite feeding succession of Entomostraca to insects to vertebrates (chiefly fish). Cannibalism occurred, as shown by the fact that 13.3 percent of 354 pike 21 millimeters or more in total length had eaten other pike. Smallest pike found to be cannibals were 21 millimeters long. Competition between young pike and most other species of fish for invertebrate food was evident. The yellow perch was the most important fish predator of young pike. Competition for food, predation, and cannibalism undoubtedly were important factors in the high mortality of young pike in their first few weeks of life.

Male northern pike made up 65 per cent of the 378 adults taken in the upstream weir of the ditches tributary to the north bay of Houghton Lake in April, 1939. An estimated additional 50 fish moved upstream before the weir was installed. The males averaged 21.2 inches, total length, while the females averaged 23.5 inches. In 1940, 58 per cent of the 118 adults were males. Twenty-eight additional spawners (13 males and 15 females) captured outside the experimental area were later added to the 118 fish. The males of the 1940 run averaged 19.8 inches in total length as compared with 23.2 inches for the females. Most of the spawners appeared in the weir between 6:00 p.m. and 9:00 a.m. The average number of days that the adult northern pike spent in the ditches i• 1939 was 18.25 (range of 6 to 50 days). In 1940 the average number of days spent in the ditches was 23.9 days (range of 4 to 90 days). The numbers of young northern pike (aside from an insignificant few that were preserved) that entered the downstream weir from the spawning grounds to Houghton Lake were: 1939---7,239; 1940--1,495. These young were the offspring of 125 potential female spawners in 1939, and of 65 in 1940. The average length of the young increased at a rate of at least 1.8 millimeters per day during the 82 days after the first hatch was observed in 1939, and at least 1.3 millimeters per day during the first 8,5 days after the first hatch was observed in 1940. Obscr•atio•s on the Northern Pike 151 DRAINAGE DITCHES ROADS DITCH NUMSER.• NORTH P* AY HOUGHTON LAF. E LOCATION OF WEIRS ]•'igure l.--Diagram of Peterson's drainage ditch system (diagrammatic) many marsh areas of varying sizes that border on the ditches are flooded. These areas often are used by spawning northern pike, although most of the spawning takes place in the ditches themselves. Most of the ditches become completely dry in late summer. DESCRIPTION O1•' FISH WEIRSWeirs used to capture young and adult northern pike were installed in Ditch I, approximately 75 feet from the lake (Fig. 1). The maximum depth at this location was 15 inches and the width was 7 feet. The upstream and downstream weirs used to take the adult fish each consisted of three wings. The wings were constructed of plaster lath, 4 feet long, and 5-foot lengths of 1-by 2-inch slats driven into the bottom, 1 inch apart. A barrier of similar eontruetion placed perpendicular to the ditch banks 15 feet from the apex of the V formed by the two wings completed the "pot" in which the fish were impounded. The apex of. the V headed into the current to catch fish going upstream; the form of the weir was reversed when the fish began to move downstream.All northern pike fingerlings that migrated from the ditches to Houghton Lake were captured in a V-shaped weir whose wings were made by placing window screen (12 meshes to the inch) over wooden •152American Fisheries Society

No abstract

No abstract

The fish population of Deep Lake (Oakland County, Michigan) was killed by poisoning with rotenone. It is believed that almost all of the fish 1 year old and over were recovered. An unknown number of the young‐of‐the‐year may not have been found, although a special effort was made to recover as many of these small fish as possible. A total of 27,329 fish weighing 562.7 pounds, was recovered, or 38.0 pounds per acre. Bluegills were the most abundant species. Legal game fish made up 3.2 percent of the number and 56.1 percent of the weight of all fish recovered. Data are presented on the length, weight, and numbers of fish by age groups and year classes for the individual species. Comparison is made between the total fish population (in pounds per acre of lake surface) of Deep Lake and other natural lakes in Michigan, Wisconsin, Florida, and Nova Scotia.