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Our objectives were to determine the general water column habitat use of Kootenai River white sturgeon Acipenser transmontanus during the prespawn and spawning periods and to determine the degree of their benthic existence. Depth-sensitive radio transmitters were attached to five male and four female white sturgeon and were periodically monitored day and night from April through June 2001. A total of 297 radio contacts were made, of which 209 included the depth of the river. One fish was not used for statistical analysis because its behavior was often modified by the presence of our boat. Of the 209 contacts, 75% (156) were made within the bottom one-third of the water column. Mean depth of the fish during the daytime prespawn and daytime spawning period was different (9.7 and 6.5 m, respectively), and the distribution between these two periods was significantly different. Some of the variation was likely due to the deeper habitat of the daytime prespawn staging reach compared with that of the daytime spawning period location (12.6 and 7.7 m, respectively). White sturgeon used a variety of locations throughout the water column, were closer to the river bottom during the spawning period, and were much more mobile during the spawning period than we previously believed. We were also able to chart some white sturgeon as they gradually cruised the contour of the river bottom several meters from the substrate yet paused momentarily. Although depth-sensitive transmitters were well suited to further defining some white sturgeon behavioral characteristics, they lacked the precision to achieve instantaneous locations.

We compared two external transmitter styles on two size‐classes of bluegills Lepomis macrochirus (laterally compressed) and yellow perch Perca flavescens (fusiform) to determine the effects of (1) even distribution of transmitter weight and (2) transmitter weights above and below the recommended 2% of fish body weight. Fish were collected, acclimated for 3 weeks before transmitter attachment, measured for length and weight, Floy tagged, and randomly assigned to treatments (single‐sided transmitter, saddle transmitter, and control). Weight and length of individual fish were recorded every 5 d through day 20 and every 10 d through day 40. On day 40, we classified tag migration, wound redness, and organosomatic indices. Saddle transmitters required the longest handling time of all treatments and did not outperform single‐sided transmitters. On day 40, only small yellow perch had gained more weight with saddle transmitters than with single‐sided transmitters. Transmitters that exceeded 2% of fish weight slowed bluegill growth, whereas transmitters that were less than 2% of fish weight negatively affected yellow perch growth. Our results suggest that even the distribution of external transmitter weight may be less important than the method of attachment and transmitter weight. Development of improved attachment methods for saddle transmitters may prove beneficial for use in long‐term studies of small, fusiform fish.

We evaluated the effects of four absorbable suture strand diameters (numbers 3/0, 0, 1, and 2 [from smallest to largest diameter]) on the short‐term retention of externally attached dummy radio transmitters by juvenile lake sturgeon Acipenser fulvescens (fork‐length range, 257–293 mm; wet‐weight range, 100–132 g). Four lake sturgeon were contained in each of 10 aquaria, and one fish in each tank was assigned to each of the four suture treatment groups. Transmitter retention was positively related to suture strand diameter, the mean retention duration for number 2 sutures being nearly twice as long (21 d) as that of number 3/0 sutures (11.8 d). The smallest suture (number 3/0) also exhibited the fewest number of days to transmitter loss (25% loss, 9 d; 50% loss, 11 d; and 75% loss, 14 d). In contrast, the largest suture (number 2) had the greatest number of days to transmitter loss (25% loss, 16 d; 50% loss, 21 d; and 75% loss, 26 d). Based on the diameter of sutures examined in this study, we recommend number 2 absorbable sutures for externally affixing radio transmitters to ensure adequate retention of short‐term tags using this novel attachment approach for telemetry studies involving juvenile lake sturgeon.

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