Fig 1.
The box identifies the area where dams regulate water movements from Namakan Lake into Rainy Lake. These dams also determine water levels in Lake Kabetogama and Sand Point Lake, which both flow into Namakan Lake. Lake Vermilion is upstream of the Namakan complex and its water levels are not influenced by water level management at these dams. Rainy Lake eventually drains into the Lake of the Woods, but water level changes at these dams do not have an influence on water level in the Lake of the Woods.
Fig 2.
Box and whisker plots showing median Walleye catch per gillnet set (CPUE) in study lakes from 1990–1999 and from 2006–2014.
Boxes encompass the first and third quartile. The lines (whiskers) show the largest or smallest observation that falls within 1.5 times the box size. Observations that fall outside the lines are shown individually. Lake Kabetogama, Namakan Lake, Rainy Lake and Sand Point Lake were all impacted by a water level management change that occurred in 2000. Lake of the Woods and Lake Vermilion were unaffected by the 2000 water level management change. The vertical dashed line separates the Pre-2000 and Post-2005 years.
Table 1.
The difference in mean catch per gill-net set before Pre-2000 and Post-2005 six northern Minnesota lakes.
Means from the Pre-2000 and Post-2005 period are calculated using a hierarchical model that accounts for non-random spatial dispersion of fish (Poisson-lognormal). Differences with 95% credible intervals that do not overlap zero are highlighted with bold text. Positive differences indicate an increase in catch per gill-net set.
Fig 3.
Box and whisker plots showing median Northern Pike catch per gillnet set (CPUE) in study lakes from 1990–1999 and from 2006–2014.
Boxes encompass the first and third quartile. The lines (whiskers) show the largest or smallest observation that falls within 1.5 times the box size. Observations that fall outside the lines are shown individually. Lake Kabetogama, Namakan Lake, Rainy Lake and Sand Point Lake were all impacted by a water level management change that occurred in 2000. Lake of the Woods and Lake Vermilion were unaffected by the 2000 water level management change. The vertical dashed line separates the Pre-2000 and Post-2005 years.
Fig 4.
Box and whisker plots showing median Yellow Perch catch per gillnet set (CPUE) in study lakes from 1990–1999 and from 2006–2014.
Boxes encompass the first and third quartile. The lines (whiskers) show the largest or smallest observation that falls within 1.5 times the box size. Observations that fall outside the lines are shown individually. Lake Kabetogama, Namakan Lake, Rainy Lake and Sand Point Lake were all impacted by a water level management change that occurred in 2000. Lake of the Woods and Lake Vermilion were unaffected by the 2000 water level management change. The vertical dashed line separates the Pre-2000 and Post-2005 years.