Alligator Gar - Scientific Research

Population Assessments and Dynamic Rates

• Binion, G. R., Daugherty, D. J., and K. A. Bodine. 2015. Population Dynamics of Alligator Gar in Choke Canyon Reservoir, Texas: Implications for Management. Journal of the Southeastern Association of Fish and Wildlife Agencies 2:57-63.
  • Population estimated at 5437 Alligator Gar (≥ 43 inches); age range 0-27 years
  • Harvest estimated to be < 3% annually
  • Bow anglers harvest 1 fish for every 50-100 hours of effort
• Buckmeier, D. L., N. G. Smith, J. W. Schlechte, A. M. Ferrara, and K. Kirkland. 2016. Characteristics and Conservation of a Trophy Alligator Gar Population in the Middle Trinity River, Texas. Journal of the Southeastern Association of Fish and Wildlife Agencies 3:33-38.
  • Population estimated at 8365 Alligator Gar (≥ 42 inches); age range 1-53 years
  • Harvest estimated to be 2-4% annually
  • Total mortality (with harvest) estimated to be 8.5% annually
• Daugherty, D. J., J. W. Schlechte, and D. L. McDonald. 2017. Alligator Gar in Texas coastal bays: long-term trends and environmental influences. Transactions of the American Fisheries Society. DOI: 10.1080/00028487.2017.1348986
  • Over 28,000 Alligator Gar collected in Texas bays from 1975-2012 from CF gill nets
  • Fish collected at a range of salinities to over 35 ppt
  • Abundance was similar or greater than Bull Sharks

Reproduction

• Buckmeier, D. L., N. G. Smith, D. J. Daugherty, and D. L. Bennett. 2017. Reproductive ecology of Alligator Gar: identification of environmental drivers of recruitment success. Journal of the Southeastern Association of Fish and Wildlife Agencies 4:8-17.
  • Years of successful reproduction correlated with years suitable spawning habitats were available. Suitable habitat = spring-summer floods that inundated floodplain habitats > 1 m deep for at least 5d, have water temperatures 68-86F, and provide access to open canopy areas with shallow flooded herbaceous vegetation.
  • Strong reproduction only occurred in about 30% of the years, and the two strongest year classes comprised about 50% of the population occurring in years with extensive June and July flooding.
• Robertson, C. R., K. Aziz, D. L. Buckmeier, N. G. Smith, and N. Raphelt. In press. Development of a flow-specific floodplain inundation model to assess Alligator Gar recruitment success. Transactions of the American Fisheries Society.
  • Created a stage specific, high resolution floodplain inundation model and overlaid land use and vegetation data layers to identify and quantify suitable Alligator Gar spawning habitat.
  • Availability of spawning habitat was correlated with reproductive success.

Movements, Habitat Use, and Population Structure

• Buckmeier, D. L., N. G. Smith, and D. J. Daugherty. 2013. Alligator gar movement and macrohabitat use in the lower Trinity River, Texas. Transactions of the American Fisheries Society 142:1025-1035.
  • While several Alligator Gar used more than 100 km of the river, most had home ranges less than 60 river km.
  • Fish showed high site fidelity, particularly to specific main-channel pools, but during high flows, sought refuge.
  • Did not represent single, panmictic population suggesting local management could be appropriate.
• Daugherty, D. J., K. L. Pangle, W. Karel, F. Baker, C. R. Robertson, D. L. Buckmeier, N. G. Smith, and N. Boyd. 2017. Population structure of Alligator Gar in a Gulf Coast river: insights from otolith microchemistry and genetic analyses.  North American Journal of Fisheries Management 37:337-348.
  • River-resident, transient, and bay-resident life histories were identified. Along the river length, these formed a gradient where use of bay habitats increased toward the coast.
  • 74% of the fish in the upper river had remained in the river their entire life.
  • Findings suggest local-scale management could be appropriate.

Management

• Bohn, S., B. R. Kreiser, D. J. Daugherty, and K. A. Bodine. 2017. Natural hybridization of Lepisosteids: implications for managing the Alligator Gar. North American Journal of Fisheries Management 37:405-413.
  • Confirmed wild hybridization between Alligator Gar and Longnose and Spotted Gar in multiple Texas waters.
  • In general, morphology is an intermediate of the two parent species.
• Smith, N. G., D. J. Daugherty, J. W. Schlechte, and D. L. Buckmeier. 2017. Modeling the responses of Alligator Gar populations to harvest under various length-based regulations: Implications for conservation and management. Transactions of the American Fisheries Society. DOI: 10.1080/00028487.2017.1341853
  • Population models indicate Alligator Gar are extremely sensitive to harvest.
  • With no length restrictions, harvest of 6.5% per year could result in recruitment overfishing.
  • Length limits allowed for greater protection and in some cases, higher harvest of specific size classes.

Anglers

• Bennett, D. L., R. A. Ott, and C. C. Bonds. 2015. Surveys of Texas Bowanglers, with Implications for Managing Alligator Gar. Journal of the Southeastern Association of Fish and Wildlife Agencies 2:8-14.
  • Bow anglers fish an average of 47 days each year, predominantly in reservoirs.
  • 57% harvested at least one gar in the past year, although about 85% harvested 5 or less (range 0-40).
  • More bow anglers felt the 1/day regulation was too restrictive than not restrictive enough.

Data Collection

• Buckmeier, D. L., N. G. Smith, and K. S. Reeves. 2012. Utility of alligator gar age estimates from otoliths, pectoral fin rays, and scales. Transactions of the American Fisheries Society 141:1510-1519.
  • Developed and validated a method to estimate age of Alligator Gar from otoliths. Non-lethal methods were not reliable.
  • Technique allows estimation of dynamic rates including longevity, growth, and understanding environmental variables associated with successful reproduction.
• Buckmeier, D. L., R. Snow, N. G. Smith, and C. Porter. 2017. Are age estimates for Longnose Gar and Spotted Gar Accurate? An evaluation of sagittal otoliths, pectoral fin rays, and branchiostegal rays. Transactions of the American Fisheries Society.  DOI: 10.1080/00028487.2017.1320306
  • Developed and partially validated a method to estimate age of Longnose and Spotted Gar from otoliths. Non-lethal methods were not reliable.
• Sakaris, P, C., D. L. Buckmeier, and N. G. Smith. 2014. Validation of daily ring deposition in the otoliths of age-0 Alligator Gar. North American Journal of Fisheries Management 34:1140-1144.
  • Developed and validated a method to estimate daily age of age-0 Alligator Gar from otoliths.
  • Technique can be used to estimate hatch dates and conditions associated with successful spawning.
• Fleming, B. P., D. J. Daugherty, N. G. Smith, and R. K. Betsill. In press. Efficacy of low-cost, side-scan sonar for surveying Alligator Gar. Transactions of the American Fisheries Society.
  • Developed and demonstrated that consumer grade side-scan sonar can be used to quantify adult Alligator Gar.
  • Provides non-invasive alternative to traditional sampling (gill nets).
• Schlechte, J. W., K. A. Bodine, D. J. Daugherty, and G. R. Binion. 2016. Size selectivity of multifilament gill nets for sampling Alligator Gar: modeling the effects on population metrics. North American Journal of Fisheries Management 36:630-638.
  • Using selectivity curves, designed an experimental gill net to collect a representative sample of Alligator Gar from 1200 to 2100 mm.
• Bodine, K. A., D. J. Daugherty, J. W. Schlechte, and G. R. Binion. 2015. A Strategy for Increasing Gill-net Catch Rates and Minimizing Sampling Mortality of Alligator Gar. North American Journal of Fisheries Management 35:611-615.
  • Developed an “aggressive-predator” sampling strategy to increase catch rates of Alligator Gar in gill nets by eightfold.
  • Strategy also reduced mortalities.
• McDonald, D. L., J. D. Anderson, C. Hurley, B. W. Bumguardner, and C. R. Robertson. 2013. Sexual dimorphism in Alligator Gar.  North American Journal of Fisheries Management 33:811-816.
  • An initial attempt to use morphology to differentiate sexes of Alligator Gar.
• McDonald, D. L., J. W. Schlechte, and D. J. Daugherty. 2017. Comparison of two biometric methods for nonlethal sex determination of Alligator Gar. Transactions of the American Fisheries Society. DOI: 10.1080/00028487.2017.1370014
  • Refined non-lethal approach using discriminant function analysis to identify sex of Alligator Gar.
  • 84% accuracy for males and 89% for females.
  • A phone app has also been developed to speed up field identification.
• Buckmeier, D. L., and K. S. Reeves. 2012. Retention of passive integrated transponder, T-bar anchor, and coded-wire tags in Lepisosteids. North American Journal of Fisheries Management. 
  • Evaluated various tag types for identifying Alligator Gar.
  • PIT and coded-wire tags had the best and longest retention. T-bar tags were effective for about 500 days.