During high water events, one tracking boat can’t effectively search many parts of the Missouri River for tagged fish. Using two boats spaced equally across the width of the river tracking downstream in parallel, or tandem tracking, is done when water levels rise, or in very complex portions of the river such as the Missouri Recreational River. Two boats tracking in tandem can detect fish effectively across a wider river and search behind wing dikes and sandbars where sturgeon hide during higher flows. Each boat also has multiple hydrophones that point in several directions so that fish can be readily detected wherever they may be hiding.
Since 2009, tandem tracking has become a regular search method utilized by USGS Comprehensive Sturgeon Research Project biologists. Water conditions downstream of the Osage River (approximately 130 miles upstream of the Mississippi River confluence in St. Louis) have been consistently at a level where tandem tracking is necessary to sufficiently search that section of river. Like single boat tracking, crews tandem track at about 6 miles per hour and cover 30-40 river miles a day. Unfortunately, tandem tracking requires double the staff and resources to search the same length of river. While the additional resources may be costly, the information about where sturgeon go during floods or extreme events, is very valuable to decision makers creating habitat for sturgeon along the length of the Lower Missouri River.