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). Received May 12, 2010; accepted December 30, 2010

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

Muskellunge are commonly stocked to maintain populations throughout much of North America. Poststocking survival is variable, and many jurisdictions are experimenting with stocking Muskellunge at advanced life stages (e.g., yearlings) or sizes to promote more consistent recruitment within populations. Yet, little is known about short-term poststocking behavior or survival of Muskellunge in natural lakes or if stocking larger fish results in improved poststocking survival. Radiotelemetry was used to evaluate the behavior and survival of large (mean of 418 mm; standard error of 3.4) spring-stocked yearling Muskellunge in two northern Iowa natural lakes of varying biotic and abiotic complexity. Hatchery-reared Muskellunge were fitted with radio transmitters (n = 10–15 fish/lake), stocked in each lake with conspecifics, and tracked either daily or weekly up to 112 days poststocking. Telemetry data were used to evaluate dispersal and movement, depth and vegetation use, proximity to shore, and survival. In both lakes, fish dispersed rapidly from each stocking site. Movement among lakes was similar and peaked during the first week poststocking and declined thereafter. Muskellunge were frequently located in offshore habitats in both lakes, but both depth and vegetation use varied among lakes and weeks poststocking, with Muskellunge found in deeper, more vegetated habitats in the larger, more complex natural lake. Muskellunge in both systems had high poststocking survival (86.7–90.0%). The results of this study provide managers with more information regarding yearling Muskellunge poststocking behavior and survival and indicate that larger fish may be a suitable alternative for fisheries where high poststocking mortality may be acting as a bottleneck for maintaining quality Muskellunge fisheries.

In 2010, Northwest Marine Technology introduced a more rigid visible implant alphanumeric (VIA) tag that substantially improved the tag loading and injecting process. To achieve these improvements, VIA tag size and composition was modified, thereby potentially influencing previously examined VIA tag retention rates on Walleye Sander vitreus. Effects of total length (TL), sex, and days post-tagging on retention of VIA tags injected underneath the lower mandible of adult Walleye were evaluated from 2012 to 2016. Walleye (n = 2455) collected from natural lakes in Iowa were measured, sexed, and injected with identical VIA tags on each side (left and right) of the lower mandible. Of 366 Walleye recaptured up to four years post-tagging, 241 had both tags; the remaining fish had retained only one tag. Overall, tag retention adjusted for fish that lost both tags (n = 14) was 80% (607 of 760). Retention of VIA tags was not influenced by sex, TL at time of marking, or number of days post-tagging and did not substantially differ from previously examined large-format VIA retention rates. In studies requiring high tag retention in Walleyes, VIA tags injected into the clear tissue underneath the mandible should be avoided.

Muskellunge (Esox masquinongy) is the largest and most prized game fish in North America. However, little is known about Muskellunge genetic diversity in Iowa’s propagation program. We used Whole-Genome Sequencing of 12 brooding individuals from Iowa and publicly available RAD-seq of 625 individuals from the St. Lawrence River in Canada to study the genetic differences between populations, analyze signatures of selection, and evaluate the levels of genetic diversity in both populations. Given that there is no reference genome available, reads were aligned to the genome of Pike (Esox lucius). Variant calling produced 7,886,471 biallelic variants for the Iowa population and 16,867 high-quality SNPs that overlap with the Canadian samples. Principal component analysis (PCA) and Admixture analyses showed a large genetic difference between Canadian and Iowan populations. Window-based pooled heterozygosity found 6 highly heterozygous windows in the Iowa population and Fst between populations found 14 windows with fixation statistic (Fst) values larger than 0.9. Canadian inbreeding rate (Froh = 0.32) appears to be higher due to the inbreeding of Iowa population (Froh = 0.03), presumably due to isolation of subpopulations. Although inbreeding does not seem to be an immediate concern for Muskellunge in Iowa, the Canadian population seems to have a high rate of inbreeding. Finally, this approach can be used to assess the long-term viability of the current management practices of Muskellunge populations across North America.