Effects of commercial harvest on shovelnose sturgeon populations in the upper Mississippi River

Abstract

Shovelnose sturgeon Scaphirhynchus platorynchus have become an increasingly important commercial species in the upper Mississippi River (UMR) due to collapsing foreign sturgeon populations and bans on imported caviar. In response to concerns about the sustainability of the shovelnose sturgeon fishery in the UMR, we began this study to describe shovelnose sturgeon population demographics and evaluate the influence of commercial harvest on shovelnose sturgeon populations in the UMR. A total of 1,682 shovelnose sturgeon were collected from eight study pools of the UMR in 2006 and 2007 (i.e., Pools 4, 7, 9, 11, 13, 14, 16 and 18). Shovelnose sturgeon from upstream pools generally had greater lengths, weights, and ages than shovelnose sturgeon from downstream pools. Additionally, mortality estimates were also lower in upstream pools (i.e., Pools 4, 7, 9, and 11) compared to downstream pools (i.e., Pools 13, 14, 16, and 18). Analyses indicated that decreased growth of shovelnose sturgeon may be a consequence of commercial harvest in the UMR. Modeling of potential management scenarios suggest a 27-inch minimum length limit is necessary to prevent growth and recruitment overfishing of shovelnose sturgeon in the UMR.

Measurement error in shovelnose sturgeon: evidence from field observation and controlled experiment data

“…Fork length measures from the tip of the snout to the center of the fork in the tail. As is the case in this study, primitive fishes with heterocercal tails are generally measured with fork length (Baker et al 2008;Koch et al 2009). However, with any of these measures of length it may be possible to obtain erroneous length measures.…”

Commercial Fisheries of the Upper Mississippi River: A Century of Sustained Harvest

“…For instance, various authors have evaluated different aspects of the commercial fishery for catfishes (Pitlo 1997;Slipke et al 2002;Krogman et al 2011). Similarly, members of the suborder Acipenseroidei have been the focus of research varying from descriptions of the commercial harvest of Paddlefish Polyodon spathula (Quist et al 2009) to assessments of the effects of commercial harvest on Shovelnose Sturgeon Scaphirhynchus platorynchus (Koch et al 2009b). Although previous work on select species in the UMR is valuable for management, a comprehensive description of commercial fisheries in the UMR is needed.…”

“…Following implementation of the length limit in 1985, recruitment improved and commercial harvest of catfish in pools 9-19 increased (Pitlo 1997;Slipke et al 2002). Similarly, collapse of sturgeon populations in Europe in the 1990s raised concerns about potential increases in commercial harvest of Shovelnose Sturgeon in the UMR to support the caviar market (Koch et al 2009b). Accordingly, Iowa, Wisconsin, and Illinois proactively implemented length restrictions for commercial fisheries in UMR border waters.…”

“…In addition, the Iowa Department of Natural Resources partnered with Iowa State University researchers to undertake a study evaluating the influence of commercial harvest on populations of Shovelnose Sturgeon in the UMR. The study resulted in a suggested 685 mm minimum length limit to avoid growth and recruitment overfishing of Shovelnose Sturgeon in the UMR (Koch et al 2009b). Bowfin are also targeted in commercial fisheries for sale in the caviar market (Koch et al 2009a); however, the Bowfin market has remained relatively small in the UMR.…”

Reproductive traits of shovelnose sturgeon Scaphirhynchus platorynchus (Rafinesque, 1820) in the lower Platte River, Nebraska

“…Specific life-cycle stages of shovelnose sturgeon in various river systems have been investigated (e.g. Colombo et al, 2007;Koch et al, 2009;Tripp et al, 2009). The capture of shovelnose sturgeon in spawning condition indicates that they likely spawn in late April to June when water levels rise and temperatures reach 16.9-20.5°C (Dryer and Sandvol, 1993;Keenlyne, 1997;Tripp et al, 2009).…”