[en] High variability of the TLD rods masked any small reductions in variability due to improved methods. Because temperature and exposure time are determined by the total change in signal (fade), the 4.6 percent standard error of a packet measurement is often a larger percentage of the absolute difference and consequently increases the minimum detectable differences. Since change in fade rate increases with increasing temperature, some advantage is gained when determining maximum discharge residence time; however, integrated fade in a fluctuating temperature environment is not directly related to true average temperature. By knowing these limitations, the integrated average temperature value, although higher than true average temperature, can still provide useful information about thermal exposure to fish

[en] Although visual observations suggested that fish remained in the discharge for considerable periods, temperature-sensitive tags indicated the majority of fish spend less than 50 hr or 10 percent of the time at discharge temperatures. During 1974 a second fish tagging study was conducted, using temperature-sensitive tags to yield discharge residence times of Lake Michigan salmonids at Point Beach thermal discharge. Preliminary results revealed that many fish tag values were close to Unit I line indicating that calculated maximum discharge residence times for these fish will be nearly 100 percent of the elapsed time

No abstract available

No abstract available

[en] Fin clips observed on fish collected during tagging studies at the Point Beach and Waukegan thermal discharges were recorded and the data were tabulated by species. Using fin clip and fish size, attempts were made to identify probable stocking locations and dates from agency records. Data are presented for lake trout, rainbow trout, brown trout, and Coho salmon. Tables are presented to show probable stocking locations and dates

[en] Fish tagging studies were conducted in the vicinity of Point Beach Nuclear Plant and Waukegan Power Plant to determine whether there were any seasonal or site specific differences in the residence behavior of salmonids at thermal discharges. Results showed that there were differences in the abundance and time of peak abundance of trout and salmon at the two power plant discharges. Certain species reacted differently to the two discharges probably as a result of maturity and water temperature. Salmonids did not appear to remain at either discharge for long periods. Direction of migration was affected by stocking location and water temperature

[en] A pilot study was conducted to identify possible contaminants accumulated by thermal plume-resident fish in Lake Michigan. Brown trout were maintained in tanks receiving intake and discharge (less than or equal to 21⁰C) water from a power plant and were fed a diet of frozen alewife. Fish were sampled over a period of 127 days in order to estimate uptake rates and equilibrium levels for toxic organic and inorganic materials occurring in Lake Michigan fish and water. Experimental fish and natural samples were analyzed to determine the distribution of contaminants in various tissues and the corresponding pollutant levels in similar size brown trout from Lake Michigan. The quantitative analyses for the major organic contaminants are summarized. Without exception, the pyloric caecum of brown trout contained the highest concentration of lipids, PCB's, and chlorinated pesticides. Gill and kidney samples contained lower concentrations of contaminants than the caecum, while liver and muscle values were lowest

[en] Fade characteristics of TLD temperature tags for fishes were evaluated. Maximum possible discharge residence time, which assumes the lowest discharge temperature exposure, was determined by the number of hourly discharge temperatures used to calculate a 1/S value equal to the measured tag value. This procedure was verified using a tag recovered from a fish known to have been confined within the discharge flume of thermal effluents for the entire tag period

[en] A comparison of data on fish mortalities due to impingement at thermal power plant water intakes on Lake Michigan with available estimates of standing crop biomass, commercial and sport fishery catches, and estimated predation mortality is presented. The striking features of these data are the proportions of total mortality due to predation and the lack of accurate basic population statistics such as standing crop biomass and natural mortality for important forage and human food fishes in Lake Michigan. Although this preliminary assessment would indicate that power plant and total impingement losses constitute an insignificant fraction of total forage biomass, the potentially unstable forage-predator ratios and the apparent high degree of annual fluctuations (year-classes) in alewife, smelt, and perch indicate the need for a more detailed assessment of cooling-system related impact on selected populations

[en] A technique has been developed for using pre-irradiated TLD's to measure temperature exposure. This ''thermal dosimetry'' is based on the loss or ''fade'' of stored TL signal at a rate proportional to temperature such that the total accumulated fade provides a measure of the past accumulated temperature exposure. Requirements for the effective use of this technique are discussed in relation to practical experience gained in using CaSO₄:Mn to monitor average environmental water temperatures and the thermal exposure of individual fish