We evaluated Wyoming Game and Fish Department (WGFD) file information to determine the species of trout raised, the number of catchable-and subcatchable-size trout stocked, the return rate of stocked fish to the creel, reasons for variability of return rates, and the direct cost associated with stocking trout. About 8.9 million trout were planted yearly from 11 WGFD hatcheries during 1987-1990; 86% were of subcatchable size (<8.25 in) and the rest were of catchable size (^8.25 in). Rainbow trout Oncorhynchus mykiss and cutthroat trout O. clarki were most often stocked. Evaluation showed that return rates (percent of number planted that were caught) to anglers were usually greater for catchable than for subcatchable fish. Catchable trout should be stocked in spring and when fishing pressure is highest for best returns; few catchable trout planted after the fishing season survive to the next season. Return rates of subcatchable trout planted in streams varied due to differences in water quality in the hatchery and receiving water, poststocking competition with other fish, time of stocking, and size of fish stocked. Subcatchable trout should be stocked in streams in spring and only when hatchery and receiving water are of similar quality, water temperature and flows are not limiting, and few competing fish are present. Higher returns in streams also occur as larger fish are stocked. Return rates of subcatchable trout were greater for lakes than for streams. For highest lake returns, subcatchable trout should be stocked in productive waters (indicated by total dissolved solids) where competing planktivores and piscivores that prey on stocked trout are few. The cost of production and distribution was US$0.68/fish for catchable and $0.13/fish for subcatchable trout. Mean cost offish reaching the creel was less for catchable trout (lakes, $2.32; streams, $3.67; 1953-1989) than for subcatchable trout (lakes, $37.44; streams, $6.29; 1953-1988). Research opportunities include developing foresighted management plans based on a combination of biological technology and public desire, evaluating the elimination of subcatchable plantings in streams and alternative management for wild trout, evaluating the transplantation of wild trout or eyed eggs of wild fish as a means of establishing fisheries, evaluating stocking guidelines applicable to various Wyoming conditions, determining the effect on harvest of behavioral differences between hatchery and wild trout, and comparing the genetic backgrounds of hatchery trout to determine their effects on postplanting survival.Anglers in Wyoming believe both that planting in southeastern Wyoming was high because drainhatchery-reared trout is valuable for maintaining ages such as the North Platte River had no native good fishing and that wild trout are important, and trout. More recently, the Wyoming Game and Fish they have a wide variety of perceptions about fish-Department (WGFD) has used hatchery trout to ing (Anderson et al. 1990). Production of hatchery replace wild stocks lost throug...

Electroshocking elicited an immediate increase in plasma corticoid and lactate concentrations and thrombocyte:leucocyte ratio in rainbow trout (Salmo gairdneri). Plasma glucose concentrations increased significantly after 3 h. Plasma protein, calcium, magnesium, and androgen levels were not measurably affected. Plasma lactate returned to preshock levels within 3 h, but corticoid and glucose concentrations remained elevated for at least 6 h. The fish coughed violently or did not resume normal breathing rates for 60 s post shocking. Although breathing frequency did not increase, buccal pressure increased substantially and required at least 1 h to return to preshock levels. Cardiac activity was irregular immediately after shocking, but no predictable alterations in rate were evident thereafter. The height of the T wave in ECGs increased markedly 1–3 min after shocking. The electrophoretic patterns of 13 isoenzymes from liver, white muscle, and plasma did not differ between fish captured by dipnet and those captured by electrofishing.Responses exhibited by fish to shocking are most likely attributable to combined effects of trauma, factors associated with paying off of an oxygen debt, and attributes associated with the general adaptation syndrome of stress. A substantial period of time of more than 6 h is required for fish to return to "normal" preshock conditions.

We evaluated stockings of rainbow trout Oncorhynchus mykiss in Pathfinder and Alcova reservoirs, Wyoming, to determine what combination of strain, season of stocking, and size at stocking maximized angler catch in the presence of walleyes Stizostedion vitreum. Coded wire tags were used to identify individual rainbow trout to stock group. Angler catch of Kamloops rainbow trout and fall rainbow trout in Pathfinder Reservoir exceeded returns of Eagle Lake rainbow trout. Differences in strain performance in Alcova Reservoir were less pronounced. The importance of season of stocking was identified with fall-stocked (August-October) rainbow trout returning to anglers in higher numbers than those stocked during spring (March-June). Size-at-stocking evaluations indicate that large, catchable-size (Ͼ208 mm total length) rainbow trout maximize use of hatchery facilities over stocking greater numbers of small, catchable (178-207 mm) or subcatchable (127-177 mm) sizes. Pond feeding trials conducted with three walleye size-classes and three rainbow trout sizes showed that 127-mm rainbow trout were highly vulnerable to walleyes as small as 330-378 mm. Intermediate-size rainbow trout (178 mm) were not readily consumed by 381-432-mm walleyes, but they were vulnerable to 483-533-mm walleyes. At 229 mm, rainbow trout appeared invulnerable to walleyes in the largest size-class (483-533 mm) we studied. Rainbow trout stocked at large, catchable sizes are probably vulnerable to fewer walleyes compared with small, catchable and subcatchable sizes, allowing greater numbers to survive predation and recruit to the sport fishery.

An average of 8.9 million trout (Oncorhynchus spp., Salmo trutta, Salvelinus spp.) were planted in Wyoming each year from 1987 through 1990; 86% were of subcalchable size (<8.25 in) and 14% were of catchable size (>8.25 in). Of the total fish planted, 1.9 million subcatchable trout and 177,000 catchable trout were planted in streams. Harvest rates of trout stocked in streams was low (average, 5.7%), possibly because of the hatchery conditions under which they were reared. Hatchery-reared trout were raised in conditions far different from those of natural waters: densities hundreds of times those in the wild, nearly constant water flow and water temperature, regular feeding, lack of cover, and absence of predators. Hatchery trout may become disoriented, fail to seek cover, forage inefficiently, and die when planted in streams with competing fish. Evaluating the survival of hatchery trout fed natural food, rearing hatchery trout in simulated natural conditions, raising them at moderate densities, and evaluating costs associated with management of wild and hatchery trout would provide additional means for judging the potential to train hatchery trout to survive in the wild. Such evaluations also would provide more criteria upon which to judge the success of planting hatchery trout.

We developed a standard weight (W s ) equation for lake trout Salvelinus namaycush using the regression-line-percentile technique. Length and weight data from 58 populations of lake trout over most of the species* geographic range were used in development of the equations. In metric units (W St weight in grams; TL, total length in millimeters): logio^= -5.681 + 3.2462 logioTL. In English units (W s , pounds; TL, inches): logioW* = -3.778 + 3.2462 logi 0 TL. A systematic change in relative weight with increasing fish length was not evident.The use of condition indices in assessing the relative plumpness offish in a population is widespread in fisheries management. Recently, the concept of relative weight (W r ) has been applied frequently by fisheries managers (Wege and Anderson 1978) when standard weight (W s ) equations are available for target species (Murphy et al. 1991). Murphy et al. (1990) developed the regressionline-percentile (RLP) technique as a method for deriving standard-weight equations, and they recommended its use as a standardized approach for deriving W s equations. We used the RLP technique to develop a W s equation for lake trout Salvelinus namaycush. This is the first proposed W s equation for a salmonid species that has been developed using the RLP technique.The lake trout is native to North America, its range coinciding with the limits of Pleistocene glaciation (Scott and Crossman 1973). The lake trout is found throughout Canada, and in the United States it is native to several northerly states-Alaska,