Movement and Survival of Black River Strain Walleye Sander vitreus in Southern Missouri Rivers
ABSTRACT: Limited research has been conducted on Black River strain (BRS) walleye Sander vitreus that occur in south-eastern Missouri rivers. In an effort to provide additional insight on stocking contribution to existing stocks and movement of juvenile and adult walleye in these systems, multiple evaluations were conducted examining stocking mortality, juvenile movement using biotelemetry, adult movement and exploitation using reward tags, and stocking contribution using chemically marked otoliths. Survival of walleye fingerlings 48-h post stock-ing was extremely high (range = 92-100%) during net-pen studies conducted in 2005, 2006, and 2007. In preparation for a biotelemetry study utilizing juvenile BRS walleye, a preliminary evaluation of walleye sur-vival and tag expulsion rates was conducted using internal and externally-attached dummy tags. Internal radio tags were deemed the best option for tracking juvenile walleye movement due to high survival (100%) and low tag loss rates (10%) during the preliminary evaluation period. Beginning 13 April 2007, 15 juvenile walleye implanted with radio telemetry tags were stocked into both the Current and Black rivers and subsequently tracked for 17 weeks. On three different occasions during the 17-week study, diel tracking was also conducted on a sub-sample of walleye in each river. Final displacement from stocking location, total movement, and the rate (km/day) of movement of juvenile walleye were greater in the Current River than in the Black River. Movement in the Current River was generally upstream whereas upstream movement on the Black River was restricted by Clearwater Lake dam. Diel tracking sessions showed the majority of movement in both rivers occurred during nocturnal hours with very little movement occurring during diurnal hours. Walleye utilized significantly deeper depths in the Current River than in the Black River and the relative proportions of the types of structure with which walleye associated were also significantly different between the two rivers. However, walleye in both rivers generally utilized deep areas where structure provided a break in the swift current. Overall, 36.7 percent of radio-tagged walleye expired during the 17-week study, with a majority (33.3%) of the mortality in the Black River caused by great blue herons Ardea Herodias. The nocturnal move-ment patterns of BRS walleye within the large, shallow pool below Clearwater Lake dam provided effective foraging opportunities for great blue herons. Since 1991, reward tagging projects have been conducted on adult walleye in the study rivers thereby providing managers information on adult walleye movement, exploi-tation, and longevity. Some reward-tagged walleye exhibited extreme movement patterns and many remained in the systems for several years after initial tagging. Some past attempts have been made using oxytetracycline (OTC) to examine the contribution of stocked walleye to the fishery. The small sample of otoliths analyzed for OTC marks suggests that stocking contribution is relatively high in the Black River. Fishery managers now have a better understanding of the movement patterns and population dynamics of BRS walleye in these rivers allowing them to better manage this unique fishery.