Using Lindgren–Pitman Hook Timers to Understand the Dynamics of Trotline Catches in a Large River

Abstract

Trotlines have historically been used by commercial fishers to target ictalurids and have recently been shown to be effective for collecting sturgeons Scaphirhynchus spp. However, little is known about the gear–fish interaction after trotlines are deployed. Therefore, the objectives of this study were to determine whether trotlines equipped with Lindgren-Pitman (LP) hook timers could withstand harsh riverine conditions and whether catch rates, retention rates of hooked fish, capture times of targeted species, and bycatch would be affected. Our results showed no difference between standardized trotlines and trotlines with hook timers and indicated that 31% of pulled hook timers resulted in no fish being collected. Hook timers were activated by 69% of all the fish collected. The majority of fish collected were shovelnose sturgeon S. platorynchus (77%), of which 70% activated the timer. The fork length of the shovelnose sturgeon that did activate the timer (571.0 ± 60.1 mm [mean ± SE]) did not differ from that of fish that did not (542.4 mm). Overall, 43% of the hook timers were activated within the first 2 h of deployment and an additional 19% in the next 2-h period; 54% of the fish were collected prior to sunset. Our study shows that hook timers can be a valuable tool that will aid in the interpretation of trotline catches.

Received March 16, 2011; accepted June 14, 2011

ACKNOWLEDGMENTS

We thank the staff members of the Nebraska Game and Parks Commission Missouri River Program, including Tim Porter, Bill Garvey, Josh Wilhelm, and Jim Brannen for deploying and retrieving this gear. Without their efforts this analysis would not be possible. We acknowledge Marty Hamel, Gerald Mestl, and three anonymous reviewers for their comments on earlier drafts of this manuscript. Finally, we thank the U.S. Army Corps of Engineers for funding this effort, especially Tim Welker and George Williams who coordinate and lead the Pallid Sturgeon Population Assessment Project.