Strategies for rehabilitation of lake trout in the Great Lakes: Proceedings of conference on lake trout research, August 1983
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Dieldrin and DDT: accumulation from water and food by lake trout (Salvelinus namaycush) in the laboratory
In the laboratory we measured the amounts of dieldrin and p,p'DDT accumulated by fish from contaminated water and food to determine how fish from Lake Michigan accumulate high concentrations of these insecticides from an environment where the concentrations in water are generally less than 0.01 ppb. Eight groups of yearling lake trout (Salvelinus namaycush) were exposed to different combinations of dieldrin and p,p'DDT in water and food. Concentrations of dieldrin and p,p'DDT ranged from 0.006 to 0.010 ppb in water and from 1,700 to 2,300 ppb in food (Oregon moist pellets). After 152 days of exposure to insecticides in water, fish had accumulated an average of 478 ppb dieldrin or 352 ppb p,p'DDT. Fish exposed to dieldrin and p,p'DDT in food accumulated 470 and 648 ppb, respectively. However, it was difficult to determine exactly how much of either insecticide was accumulated from the food because trace amounts (0.003-0.004 ppb) had leached from food or feces. After exposure to the insecticide was terminated, fish eliminated dieldrin at a much faster rate than p,p'DDT. In fish exposed to a combination of dieldrin and p,p'DDT in water and then held for 125 days in uncontaminated water, the total amount of dieldrin (I?g) declined 89%, but the total amount of p,p'DDT remained unchanged. We used data from this study to estimate how much p,p'DDT adult Lake Michigan coho salmon (Oncorhynchus kisutch) accumulated from water and from food during a 104-day period (May-August 1968). The estimates suggest that during these months coho salmon accumulated most of the body burden of p,p'DDT from food.
Proceedings of the Conference on Great Lakes Resea↗
Seasonal population characteristics of the opossum shrimp, Mysis relicta, in southeastern Lake Michigan, 1970-71
This study of depth distribution, abundance, growth, reproduction and standing crop of the opossum shrimp, Mysis relicta, in southeastern Lake Michigan was based on monthly samples collected from August 1970 through July 1971 (except February and March). Population density was usually low at 10-20 fathoms, moderate at 25-30 fathoms and relatively high at 35 fathoms and deeper. Abundance was highest in midsummer and lowest in December. Free-living mysids were 3-25 mm long. Average growth rate was 1 mm per month. At maximum lengths, females were longer than males. Weight increased as approximately the cube of the length. The population consisted mostly of juveniles during summer and autumn and subadults and adults in winter and spring. Sizable numbers of adults apparently moved to relatively shallow water (10-35 fathoms) in winter, where they bred and released their young. In deeper water (40 fathoms or more), some reproduction occurred throughout the year. Most recruitment was in April and May. Standing crop ranged as high as 50 kg per hectare. Mysis apparently has a one-year life cycle in southeastern Lake Michigan.
Proceedings of the 15th Conference on Great Lakes ↗
Introduction to the Proceedings of the 1994 International Conference on Restoration of Lake Trout in the Laurentian Great Lakes
Lake trout (Salvelinus namaycush) restoration in the Great Lakes began in the 1950s when stocking of artificially propagated lake trout was coupled with the first attempts at sea lamprey (Petromyzon marinus) control. A major milestone in the restoration process was recorded when a selective sea lamprey larvicide was identified in 1958 (Applegate et al. 1958) and then applied broad scale in Lake Superior in 1958-60 (Applegate et al. 1961). Other milestones include the expansion of the sea lamprey control programs into Lakes Michigan and Huron in 1960 (sustained usage in Lake Huron began in 1966, Smith and Tibbles 1980), Lake Ontario in 1971-72 (Elrod et al. 1995), and Lake Erie in 1986 (Cornelius et al. 1995). Following the collapse of lake trout in the Great Lakes and the implementation of massive stocking of hatchery-reared fish and effective sea lamprey control, the first documented evidence of nearshore natural reproduction of lake trout was in Lake Superior in 1965 (Dryer and King 1968), in Lake Michigan in 1980 (Jude et al. 1981), in Lake Huron in 1981-82 (Nester and Poe 1984), and in Lake Ontario in 1986 (Marsden et al. 1988).
Journal of Great Lakes Research↗