We compared the removal and processing times required when scales, sagittal otoliths, and dorsal spines were used as age estimation structures for 160 walleyes Stizostedion vitreum collected from six water bodies in South Dakota. Removal and processing times were calculated by 10 fish groups. Dorsal spines required the least amount of time for removal, followed by scales and otoliths. Whole-view otoliths required no further manipulation prior to estimating age, while the sectioning of dorsal spines and scale pressing required 12.5 and 16.6 min of additional processing time, respectively. Dorsal spines and scales also required significantly more time to read than otoliths. In terms of total processing time, whole-view otoliths proved the most time-efficient approach for estimating the age of walleyes. Scales were slightly more time-efficient than dorsal-spine sections, and sectioning otoliths would add additional processing time. Sectioning may not have been necessary in this evaluation because ages estimated by an experienced viewer from the sectioned otoliths agreed with ages estimated from whole-view otoliths 98% of the time (although reader inexperience could result in lower rates of agreement). The relative precision between readers was approximately five times greater with whole-view otoliths than with scales or spines. Reader agreement rates associated with whole-view otoliths were also significantly higher than rates for scales or spines. Based on our findings, otoliths provide the most time-efficient and precise approach for estimating the age of walleyes.Sagittal otoliths provide a more accurate (Erickson 1983;Heidinger andClodfelter 1987) and precise (Campbell andBabaluk 1979;Belanger and Hogler 1982;Marwitz and Hubert 1995;Kocovsky and Carline 2000) approach to walleye Stizostedion vitreum age estimation than scales, especially when dealing with older individuals. Conversely, many agencies continue to use scales for estimating the age of walleyes during routine management surveys; they frequently state that scales require less time to remove and process and do not require fish sacrifice. Dorsal-spine sections

Accurate age estimates are critical for understanding life histories of fishes and developing management strategies for fish populations. However, validation of age estimates requires known-age fish, which are often lacking. We used known-age (ages 1–25) muskellunge (Esox masquinongy) to determine the precision and accuracy of age estimates from fin rays. We also determined whether fin location (anal or pelvic), fin ray number, and preparation methods affected accuracy and precision. Lastly, we determined whether von Bertalanffy growth parameters estimated from fin ray ages were similar to parameters estimated from known ages. Precision and accuracy of age estimates from anal and pelvic rays were similar and estimates were relatively precise (coefficient of variation = 8.5%) and accurate (mean absolute difference from known age = 0.85 years) for ages 4–15, but ages were overestimated for younger fish and underestimated for older fish. Growth models based on estimated age were similar to models based on known age. Anal and pelvic rays offer a nonlethal alternative for age estimation of muskellunge ages 4–15 and for producing reliable estimates of growth.

Stocking Walleye Sander vitreus is a common management tool to augment populations where natural reproduction is limited. Some hatcheries have progressively raised larger fingerling Walleye to improve poststocking survival; however, little is known about the poststocking survival and behavior of large fingerling Walleye. We sought to evaluate the poststocking daily apparent survival, depth use, dispersal, and home range size of large fingerling Walleye (>200 mm TL) in three Iowa, USA, lakes. Walleye (209–265 mm; n = 15 per lake [45 fish total]) were implanted with radio tags, stocked on October 26–30, 2017, and tracked until May 30, 2018. Cormack–Jolly–Seber recapture models estimated that Walleye apparent survival increased with days poststocking and fish length, resulting in 76% (95% CI = 44–89%) cumulative survival by May. Walleye in Brushy Creek Lake were located in deeper water (mean ± SE = 5.1 ± 0.2 m) than those in Big Creek Lake (3.3 ± 0.2 m) or East Okoboji Lake (1.7 ± 0.1 m), but depth use did not vary with days poststocking. Walleye dispersed an average of 1,355 ± 234 m within 13 d across all lakes, with home range size being larger in Big Creek Lake (mean ± SE = 67.9 ± 21.7 ha) than in Brushy Creek Lake (15.5 ± 15.7 ha) or East Okoboji Lake (31.0 ± 14.0 ha). Our results indicate that Walleye poststocking survival is high overall, with most mortality occurring within 20 d as Walleye are dispersing, suggesting that managers should focus on improving survival during this critical period to improve stocking success.

We evaluated the effects of fish length, fish sex, and number of days posttagging on retention of large‐format, soft visible implant (VI) alphanumeric tags that were injected underneath the clear tissue on the lower mandible of Walleyes Sander vitreus. We also evaluated whether the direction of insertion or the application of surgical‐grade tissue adhesive to the tag incision site would affect tag retention. Adult Walleyes were collected with gill nets from natural lakes in Iowa during spring and then were transported to a hatchery, where they were measured, sexed, and tagged. One worker injected 752 Walleyes (mean TL = 21.8 in; SE = 0.16) with two identical VI tags; each side (left and right) of the lower mandible received one tag. Incisions were dried with a cloth, and tissue adhesive was applied to one of the two tag injection sites. Walleyes were released back into the lake and were recaptured with gill nets and by anglers. Of the 129 Walleyes recaptured up to 5 years posttagging, 80 fish (62%) had retained both tags and the remaining 49 fish had retained one of the tags. Retention adjusted for fish that lost both tags (n = 8; probability = 0.09) was 58% (80 of 137). Tag retention was significantly related to fish size at the time of tagging, as smaller fish lost more tags. Consequently, males (mean TL = 20.5 in; SE = 0.39) were more likely to lose tags than females (mean TL = 24.3 in; SE = 0.26). Insertion direction, adhesive application, or the number of days posttagging at recapture did not influence VI tag retention. We recommend that in studies requiring high tag retention in Walleyes, the injection of large‐format, soft VI tags into the clear tissue underneath the mandible should not be considered. Received February 16, 2012; accepted October 3, 2012

We evaluated the effect of length and depth of capture of saugers Sander canadensis on winter hooking mortality below Lock and Dam 3 of the Mississippi River (i.e., Pool 4) by catching saugers using the most common recreational fishing gear in these fisheries (jig and plastic, jig and minnow, and jigging spoons) and holding the fish for 72 h in a net-pen. Sauger winter hooking mortality was 26.4% and increased with depth of capture. Thirty-three percent (56 of 172) of the saugers caught at depths of 9 to 24 m died, compared with only 2% (1 of 41) of those caught at depths of 9 m or less. There was no relationship between fish length and mortality; however, fish caught at depths of 12 m or less were significantly larger. We applied our hooking mortality estimates (26.4%) to a concurrent creel census and estimated that 2,500-2,900 kg of saugers were lost each year to winter hooking mortality. The percentage of total angling mortality (harvest and hooking) resulting from catch and release each winter was 30.5% (2,515 kg/8,256 kg) in 2005-2006 and 33.0% (2,812 kg/8,529 kg) in 2006-2007. Based on the historical abundance and annual mortality estimates available for Pool 4 saugers, winter hooking mortality did not substantially reduce the population. However, anglers may reduce winter catch-and-release hooking mortality by fishing in shallower water (<9 m).