An examination of collection methods, habitat, and population demographics of the shovelnose sturgeon (Scaphirhynchus platorynchus) in Pools 20 and 24 of the Mississippi River.

摘要

Sturgeon populations are threatened worldwide as a result of overharvest and loss of habitat. Shovelnose sturgeon (Scaphirhynchus platorynchus ) are the only commercially harvestable sturgeon species within the Mississippi River, and collapsing sturgeon fisheries worldwide suggest more fishing effort will be directed toward shovelnose sturgeon in this river. Thus, management of Mississippi River sturgeon is crucial, but little information exists on the best methods for capturing shovelnose sturgeon in the Mississippi. Also, information is lacking on the population demographics of these fish. I evaluated several different methods for capturing shovelnose sturgeon in Pools 20 and 24 of the Mississippi River. Gill nets, hobbled gill nets, trotlines (with both "J" hooks and circle hooks), hoop nets, and trammel net drifts were evaluated because they are commercial fishing methods commonly used in the Upper Mississippi River. I captured 2,187 shovelnose sturgeon in 675 different collecting method sets. Hobbled gill nets had the highest catch per unit effort (CPUE) (2.5 fish per hour) and caught the largest fish (mean fork length = 597.8 mm), while hoop nets had the lowest CPUE (0.1 fish per hour) with the smallest fish (mean fork length = 544.5 mm). Although "J" hooks and circle hooks, caught similar sized fish, "J" hooks were found to have significantly higher catch rates (0.06 fish per hour) than circle hooks (0.02 fish per hour). Gill net mesh size did not influence size of captured sturgeon (p 0.001, R2 = 0.0001, N = 1308).;The different collection methods were fished within seven different habitat types in Pools 20 and 24 of the Mississippi River. Diked channel borders had the highest catch rates (3.18 fish per hour) but held smaller fish than all other habitats (mean fork length = 542.8).;This study examined the age, growth, and mortality of shovelnose sturgeon captured in Pool 20. Shovelnose sturgeon from Pool 20 ranged from age 3 to age 13. Fish did not recruit fully to the collection methods until age 6. Relative weights for shovelnose sturgeon in pool 20 were generally low. Catch curve analysis provided an estimated annual total mortality of 47.61%. The von Bertalanffy growth equation showed rapid growth up to age 3, after which growth slowed.;Data from this study will be useful to help identify the most efficient collection method for monitoring shovelnose sturgeon in the Upper Mississippi River and will provide a baseline for future monitoring effort.