Navarro Mills Reservoir - 2004 Survey Report

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Prepared by Timothy J. Bister and Richard A. Ott, Jr., PhD
Inland Fisheries Division
District 3-C, Tyler, 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.

Navarro Mills Reservoir was surveyed during the period June 2004 to May 2005 using electrofishing, trap nets, gill nets, littoral zone habitat and vegetation surveys, and an angler access and facilities survey. This report summarizes the results of the surveys and contains a management plan for the reservoir based on those findings.

Reservoir Description

Navarro Mills Reservoir is a 4,336-acre reservoir on Richland Creek, a tributary of the Trinity River. It was constructed by the U.S. Army Corps of Engineers (USACOE) in 1963 to provide flood control and water for municipal and industrial purposes. The quality of vegetative aquatic habitat remains poor. Less than 2% of the reservoir area contains aquatic vegetation. Distribution of hydrilla has increased in recent years, but total coverage is still less than 0.5 surface acres. Hydrilla occurs mainly in the Liberty Hill Park area and could potentially cause problems at the boat ramp and swimming areas. The controlling authority has been notified of the potential problems associated with hydrilla infestation.

Fish Community

• Prey species: The predominant prey species in Navarro Mills Reservoir were gizzard and threadfin shad. Most gizzard shad in 2004 were less than six inches in length and provide appropriate sized prey for most predators. Electrofishing catch rate of gizzard shad was much lower in 2004 (133 fish/hour) compared to the 2000 and 1997 surveys (579 and 335 fish/hour, respectively). Centrarchid species (e.g., bluegill) were not abundant in surveys. This was due to high silt loads, high turbidity, and poor vegetative habitat in this reservoir. All of the sunfish collected were <5 inches and they likely contribute little to the reservoir's recreational fishery.
• Catfishes: The catch rate (CPUE) of channel catfish during spring gill netting was higher in 2005 than in previous surveys. Total CPUE was 10.0 fish/net night and CPUE of stock-size fish was 3.6 fish/net night. Channel catfish recruitment has been consistent in recent surveys and the condition of fish was good. Mean relative weight (Wr) for most inch groups was >90. No age and growth analysis was conducted for channel catfish, but previous surveys indicated that fish reached legal length (12 inches) between age 3 and age 5. Blue catfish were documented in the reservoir for the first time during the 2005 survey. There are no public reservoirs upstream of Navarro Mills Reservoir that have been stocked with blue catfish, but this species is present in the watershed. Only 4 fish were collected during the 2005 survey (0.8 fish/net night). With adequate prey availability, this species has the potential to do well in this system and provide recreational angling opportunities.
• White bass: The white bass population appears to be increasing in Navarro Mills Reservoir. The 2005 gill net survey produced 5.2 fish/net night; over three times higher than surveys conducted in 2001. Fish of legal size (>10 inches) were abundant and comparable to other quality white bass populations (i.e., Cedar Creek Reservoir and Richland Chambers Reservoir). Despite low body condition (mean Wr <90 for many inch groups), growth rates of white bass were good. Individual ages in a sub sample of 13 fish that were between 10.4 and 11.8 were all age 1. The increased white bass population in Navarro Mills Reservoir should improve angling opportunities. No palmetto bass were captured in 2005 surveys. This species, stocked throughout the 1970s, 1980s, and 1990s, failed to create a substantial sport fishery in the reservoir. Management efforts with palmetto bass were discontinued in 1998.
• Black basses: Improvements in the largemouth bass population documented in the 2000 electrofishing survey (Ott and Bister 2001) were not seen during the 2004 survey. Electrofishing CPUE was only 17 fish/hour, which is the lowest CPUE on record. Catch rate of stock-size fish ($8 inches) was 14 fish/hour, which was also very low but similar to 1997 (14 fish/hour) and 1991 (17 fish/hour). The lack of aquatic vegetation, high silt load, and high turbidity are factors that limit largemouth bass recruitment in this reservoir. Florida largemouth bass were stocked in 2002 and 2003 to increase Florida largemouth bass alleles in the population. These fish were stocked to take advantage of improved habitat conditions observed during 2000 surveys (Ott and Bister 2001). No age and growth analysis was conducted during; however, previous surveys have indicated largemouth bass reach legal size (14 inches) between age 2 and age 3.
• Crappie: Fall trap netting in 2004 indicated a high quality white crappie population in Navarro Mills Reservoir. In 1997, 2000, and 2004 surveys, trap net catch rates of stock-size fish ($5 inches) were 15.5, 14.4, and 32.0 fish/net night, respectively. Fish condition was good. Mean Wr values were >95 for most inch groups. Individual ages of a sub-sample of fish from 10.0 to 11.1 inches in length ranged from 1 to 3 with a mean age of 1.2 years. Approximately 43% of the fish sampled were longer than the minimum legal length (10 inches). Few fish were collected below 5 inches, and this may be an indication of a weak 2003 year class. However, a similar situation was seen in 1994 (Ott and Storey 1995) that did not have any lasting impact to this population. Variable year-class strength is common in crappie populations and should not be a concern at this reservoir.

Management Strategies

Based on current information, no changes in the Navarro Mills Reservoir fishing regulations are recommended. The reservoir's lack of aquatic vegetation continues to limit centrarchid populations. Any plan to improve the aquatic vegetation through introduction of desirable aquatic plants, would be difficult to accomplish due to high turbidity levels. Therefore, any improvements would have to occur naturally and likely at a slow rate. During 2008, electrophoresis should be conducted on age-0 largemouth bass to determine if the 2002 and 2003 Florida largemouth bass stockings had any positive effect on population genetics. If the percentage of Florida largemouth bass genetic influence is still below target levels, and aquatic vegetation abundance has improved, additional stocking should be recommended. The quality of the catfish, crappie, and white bass populations should provide excellent angling opportunities and should be publicized to increase utilization of these fisheries.

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