What’s the score among small fish populations in Georgian Bay’s main basin and Lake Huron’s North Channel? Provincial biologists and fisheries technicians now know: invaders like round goby and brook stickleback are increasing in number, while numbers are down for native species such as walleye, yellow perch, rock bass and minnows, such as emerald and spot-tail shiners.
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| Lake Huron fisheries technicians sort fish collected through small fish survey. Photo: Jason Mortlock/MNR-COA |
This is from a multi-year study of more than 21,000 small fish living near the shore at depths of five metres of water or less.
“Round goby were found in most locations in the main basin of Lake Huron and southern Georgian Bay,” says Stephen Gile from the Upper Great lakes Management Unit. “The goby have also expanded in the northern Bruce Peninsula, in Stokes Bay, and in the North Channel.”
Just as important is what the study revealed about small fish in general. Small fish eat plankton and then become food for larger fish. Their abundance and variety indicate the abundance and variety of all fish in a water body – including the undesirables. During the survey, technicians caught common, rare, native and invasive species: yellow perch, rock bass, spot-tail shiner, fine scale dace, brook stickleback, round goby, northern pike and alewife.
To gather information, fisheries technicians collected fish from the sample locations, day and night, using 30-metre-long seine nets. They also set equally long Nordic nets and 1.5-metre-high fyke nets, as well as minnow traps. Nets were set daily for three weeks in each of the sample basins from July through September.
In total, eight locations were sampled in each basin, with a minimum of nine sites sampled per location. In 179 net lifts, technicians captured 21,436 fish and weighed, measured and took scale samples from 3,621. This near-shore fish survey is part of a series of annual surveys that began in 2003.
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A Mesh of Fish...The Tools of the Technicians
• Fisheries technicians have used a variety of nets in the series of studies beginning in 2003, but from 2006 onward, only fyke nets and gill nets have been used because they proved to be the most effective for capturing the widest range of fish.
• The smallest nets used: minnow traps, also called Gee traps, which are wire mesh enclosures that allow fish to swim into a funnel, through a small opening and into a “basket,” from which they cannot escape.
• Fyke nets are a little more complicated. Fyke nets are enclosures made of synthetic mesh attached to a rectangular frame. The frame forms the opening, which faces shoreward. Depending on water depth, technicians use either a 46-cm- or 91-cm-tall net. A central lead net runs from the mouth of the fyke net to shore. Fish swimming parallel to the shore would meet this mesh wall, turn and then be guided by wing nets on either side down the wall, through the rectangular frame and into the main collection enclosure.
• The 30-metre-long seine nets used in the survey deliver fish by a kind of “C-section.” One technician, positioned on the shoreline, holds the wooden pole to which one end of the seine net (also called “beach seine”) is attached. Meanwhile, another technician wades out in the water, moving in a semi-circle while holding the other end of the seine. The net ends are then brought together, enclosing a C-shaped section of water – and any fish in the area.
• Gill nets, of course, have varying mesh size, designed to allowed smaller fish to pass and larger fish to become trapped when the mesh slips along their heads and holds them behind the gills. The 30-metre long imported Nordic gill nets that were used at first ranged in size from a five to 55 millimetre mesh – but were not used after 2008 in the survey. Technicians discovered that “made-in-Ontario” standard gill nets were just as effective.
• From 2003 to 2009, the variety of nets used in the Lake Huron and North Channel surveys captured almost 90 different fish species, about 60 per cent of the 153 fish species found in Ontario.
Project Partners:
- Aboriginal Youth Work Exchange Program
- Georgian Bay Association
- Ontario Federation of Anglers and Hunters
For more information, contact:
- Stephen Gile or Jeff Spears, Upper Great Lakes Management Unit – Lake Huron, Ontario Ministry of Natural Resources, Owen Sound (519) 371-5791
- Andy McKee, Lake Huron COA Basin Coordinator, Upper Great Lakes Management Unit – Lake Huron, Owen Sound (519) 371-5449