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November 24, 2020 - Summary of Gill Netting

wayne gustaveson

Staff member
Each year we set gill nets at 4 sites over the length of the lake during the first two weeks of November. We leave nets in the water for 2 nights at each sample site. The net sites include Good Hope Bay (Red Canyon), Rincon, San Juan (Piute Canyon) and Wahweap (Lone Rock). The nets are 100 feet long with 4 different mesh sizes (3/4, 1, 1.5 and 2 inch). Small mesh size catches smaller fish and larger mesh targets larger fish as fish swim into the nets each night. The fish swim into the nets after dark and are caught behind the gills. We collect all fish captured in the the nets and take measurements of length and weight. Then we take scales from bass and stripers to determine age. We examine the stomachs to find out what fish are eating and to determine the sex of each fish. Female fish typically weigh more than males of the same species. From this annual data we have a good idea of population strength, health of fish by species, and it gives us a good idea of how to handle each species with catch limits and harvest. Lake Powell has the most liberal limits in the state as we manage the abundant populations by harvest.

Good Hope is closest to the Colorado River inflow so it is the most prolific net site due to abundant plankton and nutrients in the northern lake. The San Juan is the second most abundant site as the fish respond to nutrients coming down the San Juan river. There are a few more fish caught at the Rincon compared to Wahweap but both have a satisfactory supply of sport fish.

The most commonly caught fish are gizzard shad. These adult forage fish are abundant which is a good thing because, that means there will be a good spawn next year. The young gizzard shad will provide the forage necessary for growth and production of sport fish as the water warms next spring. Threadfin shad are even better forage fish because of their small size which makes them available as forage for all sport fish year round. Their smaller size leads to small survival numbers except in high runoff conditions. We are fortunate to have two forage fish to keep stripers, walleye and bass healthy.

Here is the breakdown of number of fish caught by species. I included 2019 for comparison. Remember that 2019 was a highwater year which lead to great reproduction of most species. The high numbers in 2020 were helped by the high water in the previous year. In 2021, remember the low water year will result in less fish that are not in as good of condition as found in 2020.

SITE 2020LargemouthSmallmouthStriped bassWalleyeCatfish
GOOD HOPE BAY19552811357
SAN JUAN1445702114
SITE 2019LargemouthSmallmouthStriped bassWalleyeCatfish
GOOD HOPE BAY25431776911
SAN JUAN19851081713

Good Hope Bay (November 2-4) always has the most fish in the survey, but 2020 gave us perhaps the biggest year ever in completing the survey. It took all day to weigh and measure the fish. On November 4th we barely made it to Bullfrog Marina in time to get gas. Then we pushed on to the Rincon and reset nets there in the twilight and got to camp after dark. We woke up the next morning ready to sample another gill net site. We were relieved to sample less fish with a smaller crew.
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