Lake Texoma 2006 Biology gill sampling report
Biologists from Oklahoma and Texas have completed annual gill sampling on Lake Texoma, which has spanned some 20 years.
This annual survey began in 1987, with 30 nets (15 for Oklahoma and 15 for Texas) being set out in February of each year.
Texas Parks and Wildlife Fisheries Biologist, Bruce Hysmith said this years catch of 25 striped bass per net night was second only to the catch of 27 striped bass per net night in 1987.
An estimated 25 percent of the sample population was 20 inches and bigger, which is down from an all time high of 33 percent in 2005.
Since 1987 the average annual catch rate was 19 striped bass per net night and the average number of striped bass 20 inches and bigger was 23 percent.
Hysmith described the process of how biologists sample open water fish like striped bass, white bass and catfish. He said they use gill nets that are 125 feet long and eight feet deep, constructed of monofilament mesh panels.
A float line is placed on top and a lead line on the bottom. The net is made up of five 25-foot panels that vary from one inch mesh to 3 inch mesh. The mesh size increases 1/2 inch every 25 feet.
Hysmith said this is called an experimental gill net, which allows biologists to collect a variety of sizes of fish which provide a good representation of the population being sampled.
The nets are set in open water on the bottom in predetermined locations. The nets are set one day and retrieved the next day after approximately 24 hours. All the fish are removed and identified by species.
Target species such as striped bass, white bass and catfish are measured and weighed with results tabulated on a data sheet. Gizzard shad are counted and measured with results also tabulated on a data sheet. All other fish are counted and released.
Hysmith said, in addition to numbers and sizes of target species, biologists are also interested in their age. For this determination they collect otoliths (ear bones) from these species and store the otoliths along with the fish?s length, weight, species and number in an envelope for further analysis.
Otoliths are bony structures located in the top part of the vertebral column and serve as organs of balance and orientation in the fish. In the lab biologists count the growth rings laid down annually in these otoliths. Each growth ring indicates one year of age. Although growth in fish can vary with respect to individual health, nutrition, water quality and genetics, a 20 inch striped bass in Lake Texoma is around four years old, said Hysmith. Before the otolith we used to use scales to get the same information, but there is too much room for mistakes with scales. We use age when we are dealing with regulations. How long does it take to get to a legal age and the otolith has made it more accurate.
Hysmith said, striped bass have done well over the past 20 years. Despite a few ups and downs, numbers of fish and size structure has remained fairly stable.