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Northern pike (Esox lucius) from eastern Lake Ontario were sampled with gill nets and trap nets in 1972-1973. Fish of age-groups IV, V, and VI were predominant in the catch. Although males were slightly longer after the 1st yr of life, females gained a 25-mm advantage in the 2nd yr and a 30-mm advantage in the 3rd yr. In later years, the increments of growth of males and females were similar. All males were mature after 2 yr and females after 3 yr. The stomachs of northern pike contained only fish; the alewife (Alosa pseudoharengus) was the principal forage species consumed. Electivity indexes for alewives, white perch (Morone americana), and yellow perch (Perca flavescens), the three most common species in the diet, indicated a positive selection for alewives that increased from June to October during a period when the relative abundance of alewives steadily decreased.

The precipitous decline in abundance of walleyes (Stizostedion vitreum vitreum) in western Lake Erie during the 1960s caused major concerns for the future of this resource. Mercury contamination in walleyes in 1970 resulted in a moratorium on commercial fishing in United States and Canadian waters. The opportunity arose for resource agencies to develop a plan for rehabilitation of the walleye stocks, and quota management for walleyes was begun in 1976. After 8 years, the resource had recovered dramatically and the estimated standing stock in 1983 was more than three times that in 1976. In the mid-1970s, however, certain detrimental changes suggested that self-regulatory mechanisms were occurring. The growth rate declined gradually but rather consistently. Growth changes were most evident for young-of-the-year (YOY), yearlings, and 2-year-old fish, which usually constituted more than 80% of the standing stock in 1976-1983. Average lengths of YOY fish in the fall decreased by nearly 50 mm (from abo...

Age and length distributions are given for 6,764 walleyes, Stizostedion v. vitreum (Mitchill), sampled during 1963-1968 from commercial landings of walleyes representing discrete populations in the eastern and western basins of Lake Erie. In the eastern basin, where all catches were made with gill nets, age-groups III and IV predominated in samples from large-mesh nets and age-group I in samples from small-mesh nets. In the western basin, where nearly all walleyes were taken in trap nets, age-groups I and II predominated in 1963-1965, and II and III in 1966-1968 (after the legal commercial size limit was raised from 330 to 394 mm). Study of 5,082 walleyes from the two basins showed that at any given age during the first 3 years of life, females were longer than males and, on the average, fish from the western basin were longer than those from the eastern basin. The greatest difference in growth of fish of the same sex for the two basins was apparent at the end of the first year of life, when fish...

A limited commercial gill-net fishery for walleyes (Stizostedion vitreum vitreum) in New York waters of Lake Erie was established in the 1950's. Since then year class strengths have varied considerably; four have been outstanding—those of 1959, 1962, 1964, and 1971. A rapid rate of rise in water temperature during spawning and incubation was positively correlated with the strength of these year classes. Each time a strong year class appeared, small-mesh gill-net effort was markedly increased, and an average of 46% of the fish of each year class was harvested at age I before they were sexually mature. If the small-mesh gill-net fishery had not been operating, the total annual production by the large-mesh gill-net fishery could have been increased by an average of 35%.

Of 2427 walleyes (Stizostedion vitreum vitreum (Mitchill)) examined from Lake Erie in 1964–66, no females were mature at ages below III and all were mature at age V. All male walleyes from the eastern basin were mature at age II, and those from the western basin at age III. Females from the western basin matured at a shorter length and a younger age than those from the eastern basin. Males from the western basin, on the other hand, matured at a longer length and greater age than those from the eastern basin.Egg production, which was estimated for 60 walleyes from the eastern basin and 78 from the western basin, ranged from 48,000 to 614,000. The number of eggs increased rapidly with increase in total length, but the relation between fecundity and weight was almost linear. Walleyes from the western basin were much more fecund for any given length, weight, or age than those from the eastern basin. Weight was the most accurate indicator of fecundity. The mean diameter of eggs from 32 ripe walleyes was 1.72 mm. Little relation existed between egg diameter and length or age of fish.

A total of 3,998 yearling walleyes, Stizostedion vitreum vitreum (Mitchill), were captured, tagged, and released along the south shore of western Lake Erie to determine their movements and their dispersal from a known nursery area. Four hundred ninety-nine recoveries were made over a period of 3 years. Tagged walleyes traveled primarily north toward the islands in the Western Basin during their first year of liberation, and in succeeding years moved progressively toward the extreme western end of the lake. Some walleyes were recaptured within 6 months in the Detroit River, Lake St. Clair, the St. Clair River, and southern Lake Huron, and the percentage of fish recaptured in these waters north of Lake Erie increased annually. Movement eastward into the Central and Eastern Basins of the lake appeared negligible. The greatest distance traveled by a marked walleye was 236 miles. The average distance traveled by all tagged fish was 25 miles.

(1968). An Improved Girthometer for Studies of Gill Net Selectivity. The Progressive Fish-Culturist: Vol. 30, No. 1, pp. 62-64.