The present study investigates the relationships between ability variables and progress in learning a complex perceptual motor skill. It represents an extension of previous research in which ability patterns at early and advanced performance levels in psychomotor tasks have been compared with a view to establishing the kinds of abilities and measures most predictive of higher levels of proficiency. These studies have implications for questions concerning the processes involved in learning complex skills as well as for problems in training and test development. A primary purpose of this study, as stated above, was to specify the abilities underlying terminal proficiency on a complex control task and to identify the manner in which the contribution of these abilities to proficiency changes during the course of learning. A battery of reference tests containing both apparatus and printed tests of known factorial structure was administered to 203 subjects. Scores on the reference tests and various learning levels of the tracking task were analyzed through factor analysis techniques. The results show that the kinds of perceptual-motor abilities which previously have been found to be related to performance on laboratory criterion tasks do not account for any substantial amount of the variance in performance with the present task. Initial component and total scores taken from the tracking task itself do not predict advanced proficiency levels. If one must choose between intratask and independent measures, the independent test measures give a better prediction of advanced tracking proficiency.

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Stock assessment from 1986 through 1990 of 15 populations of burbot Lota lota in small to moderate‐size Alaskan lakes is described. Adult (≥450 mm total length) and juvenile (300–449 mm total length) burbot were captured in baited hoop traps set in systematic patterns across lakes when lakes were ice‐free. Mark–recapture experiments were used to estimate abundance, and catch per unit effort was used to index abundance, All 15 populations had been exploited in winter recreational fisheries. Catch rates of burbot just after lakes became ice‐free in the spring and just before their freezing over in the fall were about twice those during the intervening summer. Movements of marked burbot across depth zones were extensive and random; burbot were not concentrated, but were dispersed across lakes. No relationship between catches of juvenile and adult burbot in the same sets was found. Depth preferences of burbot followed their published thermal preferences except that juveniles were concentrated in deeper waters during the first month after lakes opened. Immediate and delayed mortality from decompression of burbot captured deeper than 15 m was indicated. Changes in abundance could be detected with mean catch per unit effort in all lakes. Mean catch per unit effort was mildly density‐dependent; saturation of hoop traps with burbot was postulated as the reason. Suggestions on how to use behavior of burbot in planning stock assessment are given.

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