Hove M.C.,Macalester College |
Hove M.C.,University of Minnesota |
Bury J.A.,University of Minnesota |
Heath D.J.,550 Mormon Coulee Road |
And 5 more authors.
American Midland Naturalist | Year: 2011
We conducted a series of studies to improve our understanding of pistolgrip life history and distribution in Minnesota and Wisconsin. In the St. Croix River, where this species is relatively abundant, we studied animals biweekly from May-Nov. 1997, Apr.-Oct. 1998 and nearly biweekly during May-Jul. 2004-2007 and observed gravid females between late Apr.-Jul. at water temperatures 13-25 AC. Females held mature glochidia in a large mantle magazine that was significantly more inflated at night. Fifty-seven pistolgrip glochidia measured using scanning electron microscopy had an average height and length of 119 ±6 μ and 102 ±4 μ (±1 sd), respectively. Of 65 fish species (18 families) exposed to pistolgrip glochidia only flathead catfish (Pylodictis olivaris) and brown (Ameiurus nebulosus) and yellow (A. natalis) bullheads were suitable hosts, with flathead catfish showing the strongest host response. Glochidia grew 422 ± 17% while attached to fish. Pistolgrip is found in central and southeastern U.S. but is declining in several locations. Surveys conducted between 1980 and 2009 show the geographic range of pistolgrip has decreased in Minnesota and Wisconsin. It is extirpated from the Minnesota River and nearly so in the Mississippi River. However, we see evidence of a recovering population in a once heavily polluted reach of the Mississippi River downstream of Minneapolis-St. Paul. The largest populations are in the lower reaches of the St. Croix (MN, WI), Chippewa, Black, Wolf and Wisconsin rivers (WI). In light of the apparent close association between pistolgrip and flathead catfish, we recommend pistolgrip conservation efforts include sustainable flathead catfish management and habitat improvement to support expansion of remaining pistolgrip populations. © 2011 American Midland Naturalist.
Meerbeek J.R.,801 South Oak Street |
Hoxmeier R.J.H.,801 South Oak Street
North American Journal of Fisheries Management | Year: 2011
We evaluated the effect of length and depth of capture of saugers Sander canadensis on winter hooking mortality below Lock and Dam 3 of the Mississippi River (i.e., Pool 4) by catching saugers using the most common recreational fishing gear in these fisheries (jig and plastic, jig and minnow, and jigging spoons) and holding the fish for 72 h in a net-pen. Sauger winter hooking mortality was 26.4% and increased with depth of capture. Thirty-three percent (56 of 172) of the saugers caught at depths of 9 to 24 m died, compared with only 2% (1 of 41) of those caught at depths of 9 m or less. There was no relationship between fish length and mortality; however, fish caught at depths of 12 m or less were significantly larger. We applied our hooking mortality estimates (26.4%) to a concurrent creel census and estimated that 2,500-2,900 kg of saugers were lost each year to winter hooking mortality. The percentage of total angling mortality (harvest and hooking) resulting from catch and release each winter was 30.5% (2,515 kg/8,256 kg) in 2005-2006 and 33.0% (2,812 kg/8,529 kg) in 2006-2007. Based on the historical abundance and annual mortality estimates available for Pool 4 saugers, winter hooking mortality did not substantially reduce the population. However, anglers may reduce winter catch-and-release hooking mortality by fishing in shallower water (<9 m). © American Fisheries Society 2011.