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

Paddlefish Polyodon spathula (n ϭ 576) were collected from Kentucky Lake, Kentucky-Tennessee, with experimental gill nets in [2003][2004] to assess population characteristics and the potential for commercial overfishing. Additional data were collected from 1,039 paddlefish caught by commercial gillnetters in this impoundment. Since the most recent study in 1991, size and age structure have been reduced and annual mortality has tripled. In the 1991 study, 37% of the fish collected were older than the maximum age we observed (age 11), and in 2003 annual mortality for paddlefish age 7 and older was high (A ϭ 68%). Natural mortality is presumably low (Ͻ10%) for paddlefish; therefore, exploitation in recent years is high. Estimates of total annual mortality were negatively related to river discharge in the years preceding each estimate. The number of paddlefish harvested since 1999 was also negatively related to river discharge because gill nets cannot be easily deployed when discharge exceeds approximately 850 m 3 /s. Large females spawn annually because all females longer than 1,034 mm eyeϪfork length (EFL) were gravid. No mature females were protected by the current 864-mm minimum EFL limit. At a low natural mortality rate, higher size limits when exploitation was high (40-70%) increased simulated flesh yields by 10-20%. Even at low levels of exploitation (21%), spawning potential ratios (SPRs) under the current 864-mm minimum EFL size limit fell below 20%. If the size limit was raised to 1,016 mm EFL, the population could withstand up to 62% exploitation before the SPR falls below 20%. An analysis of annual mortality caps indicated that the best way to increase the average size of harvested fish is to increase the minimum size limit. Recruitment overfishing probably occurs during drought years; however, variation in river discharge has prevented the population from being exploited at unsustainable rates in the past.

No abstract

SummaryWe quantified the bycatch of pallid sturgeon Scaphirhynchus albus in TennesseeÕs shovelnose sturgeon (Scaphirhynchus platorynchus) fishery by accompanying commercial fishers and monitoring their catch on five dates in spring 2007. Fishers were free to keep or discard any sturgeon they collected in their gillnets and trotlines and we were afforded the opportunity to collect meristic and morphometric data and tissue samples from discarded and harvested specimens. Fishers removed 327 live sturgeon from their gear in our presence, of which 93 were harvested; we also obtained the carcasses of 20 sturgeon that a fisher harvested out of our sight while we were on the water with another fisher. Two of the 113 harvested sturgeon were confirmed pallid sturgeon based on microsatellite DNA analyses. Additionally, fishers gave us five, live pallid sturgeon that they had removed from their gear. If the incidental harvest rate of pallid sturgeon (1.8% of all sturgeon harvested) was similar in the previous two commercial seasons, at least 169 adult pallid sturgeon were harvested by commercial fishers in the Tennessee waters of the Mississippi River in [2005][2006][2007]. If fishers altered their behavior because of our presence (i.e. if they were more conservative in what they harvested), the pallid sturgeon take was probably higher when they fished unaccompanied by observers. While retrieving a gill net set the previous day, a fisher we were accompanying retrieved a gillnet lost 2 days earlier; this ghost net caught 53 sturgeon whereby one fish was harvested but most fish were dead, including one confirmed pallid sturgeon.

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