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Warmwater Surveys Lake Survey Methodology: During the spring and fall seasons, Warmwater Teams conduct standardized surveys of lakes that have been pre-designated under the management plan. The surveys are designed to collect information on the lake's fish community and habitat. Biological information on the fish species residing in the lake is collected using boat electrofishing, gill netting and fyke netting. A map is used to divide shoreline of the lake into consecutively numbered sections of approximately equal length. A random number generator is then used to choose the sampling sites. Random selectivity of the sites ensures statistically valid sampling. Standardized survey methodology allows for comparison between different lakes and years of data collection. The lake surveys are conducted by a 3 person team and usually take 3-5 days. During a typical survey week, a Team will collect information on all fish species and lake habitat including: water chemistry information, percent of aquatic plant coverage, percent development of the shoreline, and public access to lake. Biological information including fish species, length, and weight are recorded, and scales are collected from most species in order to evaluate the age and growth of the fish in the lab. The biological information is used to assess information about the fish community in the lake including: species composition by weight and number, length frequency distribution, and fish condition. Boat Electrofishing: Boat electrofishing is the use of electricity to stun and capture fish. The electrofishing unit used by the WDFW Warmwater Teams, is an electrofishing boat manufactured by Smith-Root, Vancouver, WA. The 16-18 foot flat bottomed boats are manufactured of welded aluminum. They have an electrical generator onboard. Anode and cathode droppers attached to the bow of the boat, touch the surface of the water. Anodes droppers hang from the front of two booms extended out in front of the boat. Cathode droppers are attached to the bow. Once the boat and generator are running, and the activation pedal is depressed, an electrical field is created in front of the boat. A control panel allows the operator to adjust the strength of the electrical field. This allows Biologists to efficiently capture fish, while reducing the chance of injury to fish. During a typical electrofishing survey, the boat is maneuvered through the shallows, following the shoreline of the lake. Electrofishing is usually conducted for 600 seconds of "pedal down" shocking within each randomly chosen section. The surveys are conducted after sunset, as research has shown that nighttime electrofishing is more effective. In a dc field ( the safest type of current for fish and the type that the WDFW uses), a typical reaction of the fish will be to turn towards the anode exhibiting galvanotaxis, (forced swimming with orientation) followed by galvanonarcosis (muscle relaxation). The reactions bring the fish in towards the anode in a stunned state, where they are easily netted off the front of the boat. During a typcial electrofishing survey, stunned fish are netted and placed in a live well on the boat. Biological information is then collected following the completion of each section. Fish are then released back into the lake. Electroshocking is the most effective gear type for collecting bass and many other warmwater fish species. Gill Netting: The Warmwater Teams use monofilament experimental gill nets. The nets are 45.7 m long by 2.4 m deep and are constructed of four different sinking panels with variable sizes of mesh. These experimental nets are used to sample various size of fish and to reduce size selectivity of the sampling gear used in the surveys. Gill nets are set perpendicular to the shore. The nets hang vertically in the water. Foam core line floats the top of the gill net while lead line weights the net to the lake bottom, much like a fence line under water. Fish that swim into the net become entangled in the netting. Gill nets are set overnight and typically fish approximately 12 hours. They are retrieved in the morning. Fish captured are weighed and measured and scales are collected from most species for age and growth calculations in the lab. While some fish die in the nets, others are able to be released unharmed. Gill nets have been found to be more effective in collecting yellow perch, catfish and walleye. Fyke Netting: This net type is constructed of a series of hoops covered in net webbing. There are two internal funnels that prevent the fish from swimming out of the net once they are caught. The end, called the cod end, is where the fish collect. The cod end is tied off and can be easily opened for access to the fish. The Warmwater Teams use fyke nets constructed of a main trap (4.7 m long and 1.2 meters in diameter), a lead net (30.5 m long and 1.2 m deep) which is tied off to the shore, and two wings (7.6 m long and 1.2 m deep) which are set 45 degree angles to the main trap. The lead and wing nets guide fish into the trap. Fyke nets are set overnight and typically fished approximately 12 hours. They are retrieved in the morning. Fish are weighed and measured and scales are collected from most species for age and growth calculations in the lab. Fish caught in the fyke nets are typically released unharmed. Fyke nets have been found to be effective in collecting sunfish and crappie. | ||||||||||||||||
