Grapevine Reservoir - 2003 Survey Report

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Prepared by Raphael Brock and Thomas Hungerford
Inland Fisheries Division
District 2-D, Fort Worth, Texas

This is the authors' summary from a 23-page report. For a copy of the complete report, use the download link in the sidebar.

Grapevine Reservoir was surveyed using electrofishing from 2000-2003, trap netting in 2003, and gill netting in 2004. This report summarizes the results of the surveys and contains a management plan for the reservoir based on those findings.

Reservoir Description

Grapevine Reservoir is a 6,684-acre impoundment constructed on Denton Creek, a tributary of the Trinity River by the U.S. Army Corps of Engineers in 1952 to provide flood control, municipal and industrial water, and recreation. Grapevine Reservoir is surrounded by urban development and is 20 miles northwest of Dallas, Texas in Tarrant County. The reservoir contains 188,550 acre-feet of water at conservation elevation (535 ft. mean sea level) and has an average depth of 25.5 feet and a maximum depth of 65.0 feet. Angler and boat access is adequate. There is one handicap specific facility on the reservoir. At the time of sampling the fishery habitat was primarily rocky and gravel shorelines. A 14- to 18-inch slot-length limit was implemented for largemouth bass on September 1, 1994. Grapevine Reservoir has been part of the TPWD Habitat Improvement Initiative since 1997; however, because of water level fluctuations there has been limited success. A creel survey was conducted on Grapevine Reservoir from June 1, 2003 to May 31, 2004.

Fish Community

• Prey species: The electrofishing catch rates of gizzard shad were very high from 2000-2003 averaging 386.6/hour, and ranged from 620.0/hour in 2001 to 287.3/hour in 2002. This average catch rate was higher than the district average of 274.0/hour. The threadfin shad electrofishing catch rates averaged 198.2/hour from 2000-2003, and ranged from 348.7/hour in 2000 to 128.0/hour in 2001. The average was slightly below the district average of 205.0/hour. Bluegill and longear sunfish are the two principal sunfishes in Grapevine and their average electrofishing catch rates from 2000-2003 were 194.7 and 78.5/hour, respectively. The average catch rate for bluegill was above the district average of 158.0/hour, while the average catch rate of longear sunfish was below the district average of 88.0/hour.
• Catfishes: The 2004 gill netting catch rate for blue catfish of 3.9/net night was the highest catch rate ever sampled on Grapevine Reservoir. It was also higher than the district average of 1.6/net night. This could be an indication that the population is increasing as it has in other district reservoirs. There is no record of blue catfish being stocked into Grapevine Reservoir. The gill netting catch rate for channel catfish in 2004 was 5.0/net night which was slightly higher than previous years, and lower than the district average of 5.7/net night. Based on creel survey statistics, 24% of anglers fishing Grapevine are targeting catfish. Statistics for individual species were not collected because of the creel survey design. The species of fish being sought was recorded only as catfishes and not broken into either blue catfish or channel catfish.
• White bass: The white bass gill netting catch rate for 2004 of 2.3/net night was lower than previous surveys catch rates and below the district average of 8.2/net night. Creel survey statistics revealed 17% of anglers are targeting white bass.
• Black basses: The electrofishing catch rates for spotted bass from 2000-2003 averaged 25.5/hour, which was slightly higher than the district average of 24.0/hour. Catch rates ranged from 34.0/hour in 2003 to 16.7/hour in 2000. Several fish 12 inches and greater were sampled during the past 4-year sample period. The largemouth bass electrofishing catch rates were highly variable from 2000-2003 and averaged 125.0/hour, which was near the district average of 129.0/hour. The largemouth bass catch rates ranged from 208.0/hour in 2001 to 78.0/hour in 2002. Largemouth bass in Grapevine Reservoir continue to grow slower than the district average. Electrophoresis indicated that the percentage of the Florida largemouth bass (FLMB) alleles present in the bass sample from Grapevine has steadily decreased from 34.2 in 1999, 27.3 in 2002, to 20.3 in 2003. Largemouth bass are the most targeted fish species by anglers fishing Grapevine Reservoir. Creel survey statistics revealed that 43% of the anglers fishing Grapevine Reservoir were targeting largemouth bass. Harvest length frequency indicates anglers are harvesting fish below 14 inches. During creel surveys, anglers were asked questions regarding their opinion of the effectiveness of the slot length limit. Seventy percent of largemouth bass anglers believed the slot length limit was benefiting the largemouth bass population and wanted the regulation maintained. Statistical analyses were conducted (a = 0.05) on catch rates, growth rates and relative weights to determine if the slot length limit has significantly improved the largemouth bass population. Because the electrofishing sampling design changed from fixed stations to random stations in 1996, analysis of catch rates could not be conducted. The average catch rate of largemouth bass 14-inches and above has remained relatively stable but has increased slightly from 12.3/hour, pre-slot limit regulation, to 14.3 fish/hour after regulation implementation. The average catch rate of largemouth bass below 14-inches has decreased from 170.5/hour, pre-slot limit regulation, to 114.0/hour after regulation implementation. This decrease could have been caused by angler harvest as indicated in the harvest length frequency of angler catches measured during creel surveys. The decrease in catch rates of fish below 14-inches could have also been caused by other factors such as low water levels which limited recruitment. Pre-slot limit average lengths at age of capture for ages 1, 2, 3, and 4 were 10.1, 12.8, 15.0, and 16.7 inches respectively. After slot limit implementation, average lengths at age of capture for ages 1, 2, 3, and 4 are 10.5, 13.4, 15.5, and 17.0 inches. Although growth rates increased after slot limit implementation, these increases were not significantly higher (p<0.24). Average relative weight values of fish below and above 14 inches has increased significantly after slot length limit implementation (p=0.005 below; p=0.032 above). Smallmouth bass fingerlings (183,186) were stocked in the spring of 1999, and were sampled in fall 1999 electrofishing samples at a rate of 3.0/hour. They ranged in size from 4 to 7 inches in total length. No other smallmouth bass have been captured during electrofishing. However, a new lake record for smallmouth bass weighing 4.0 pounds was caught in 2003.
• White crappie: The trap netting catch rate for white crappie in 2003 was 24.4/net night, which was much higher than the previous year’s samples and higher than the district average of 17.8/net night. Based on current age and growth statistics, it takes 2+ years for crappie to reach legal size. Creel survey statistics revealed 10% of anglers fishing Grapevine Reservoir were targeting white crappie.

Management Strategies

• Based on current information Grapevine Reservoir should continue to be managed with existing fish harvest regulations. Based on angler opinion, the current 14- to 18-inch slot-length limit for largemouth bass should be maintained. Questions relating to angler opinion of the slot length limit asked during creel surveys revealed 70% of largemouth bass anglers believed the slot length limit regulation is benefiting the largemouth bass population and wanted the slot length limit maintained. Statistical analyses revealed improvement in relative weight but not growth rates. CPUE data could not be analyzed. The slot length limit does not appear to be hindering the population. However, during years of low water levels, if recruitment is low, harvest of fish below 14 inches could be harmful to the population.
• Future consideration should be given to changing the regulation to the statewide 14-inch minimum length limit. Changing the regulation could result in economic benefits as a result of increased tournament activity. Tournament activity could be significant with the close proximity of Bass Pro Shops and the Gaylord Resort Hotel.
• Electrophoresis samples reveal FLMB alleles are approaching 20%. Electrophoresis will be conducted annually to determine if alleles decrease below 20%, at which point Florida largemouth bass will be requested for stocking at a rate of 25/acre. Smallmouth bass will continue to be requested for stocking at a rate of 15/acre.
• Vegetation plots planted during the TPWD Habitat Improvement Initiative will continue to be monitored in cooperation with the Lewisville Aquatic Ecosystem Research Facility.

Performance Report as required by Federal Aid in Sport Fish Restoration Act Texas Federal Aid Project F-30-R-29 Statewide Freshwater Fisheries Monitoring and Management Program