Effects of environmental factors on walleye and sauger recruitment in Pool 13, upper Mississippi River

摘要

I measured the abundance of walleyes Stizostedion vitreum and saugers S. canadense in the spring as larvae and in the Call as age 0 to determine which factors limited reproductive success in Pool 13 of the upper Mississippi River. Catches of larval walleyes and saugers in conical and rectangular drift nets during 1993-2000 were significantly higher in night samples than day samples but were similar at the surface and at the bottom. The fall abundance of age-0 walleyes and saugers in four to eight nights of sampling at fixed sites in lock and dam tailwaters during 1992-1999 was not correlated with the spring abundance of larval walleyes and Saugers. However, the fall abundance of age-0 walleyes and saugers was highly correlated with the rate of water warming (degreesF/d) between April 15 and May 5. Age-0 walleye and sauger abundance was not correlated with river discharge during the April spawning period. Strong walleye and sauger year-classes were produced in 1992, 1994, and 1997 in Pool 13, The age-0 abundance of walleyes and saugers from Pools 5, 8, 10, 11, 14, and 15 shows that strong year-classes were also produced in 1992, 1994, and 1997 in those pools. I conclude that environmental effects on recruitment were systemic on the upper Mississippi River.