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Bartram's Bass of the savannah river basin

What are Bartram's Bass?

Bartram's Bass (Micropterus sp. cf. cataractae) are a riverine species of the black bass clade found only in South Carolina and Georgia. Their range extends from below the fall line of the mainstem Savannah River of South Carolina, into many areas of Georgia; also occurring in, but not native to, the Saluda River of the Santee drainage, primarily in the river’s mainstem and tributaries below the Saluda dam, and the Broad River (Bettinger 2015, Freeman et al. 2013, Oswald 2007).

Outline of Savannah River basin

Why should we care about this species?

Bartram's Bass populations are threatened by habitat alteration and hybridization with the nonnative invasive species Alabama Bass (Micropterus henshalli).

Alabama Bass (Micropterus henshalli). This species was introduced into the Savannah River basin in the 1980s by anglers to create a local sport fishery for the species (Oswald 2007). The current Bartram’s Bass populations primarily thrive in tributaries, and it is speculated that their populations have been pushed farther upstream since Alabama Bass have invaded (Oswald et. al. 2015)
There are 6 major dams on the Savannah River. Completed in 1962, the Hartwell dam (above) was constructed for flood control, hydropower and navigation.
Land use of the Savannah River basin obtained by the Georgia Rivers LMER project (2002). Identifying the effects of different land uses on Bartram's Bass populations will help us better manage for their needs in the future.

They are also A LOT of fun to fish for!

Alex Michaeli after angling for Bartram's Bass

What are we doing to help?

Identifying the nesting preferences of this bass to better manage for their populations into the future. Fish species may select specific microhabitat characteristics for spawning which involve water depth, current velocity, and substrate. Knowing what individuals need is key in managing for their populations as a whole.
Assessing the spatial ecology of hybridization to determine what is driving populations of pure and hybrid individuals. This research will help us determine the best places to focus management for this species in the future.

Study Area

Our research focuses on the upper Savannah River basin. In 2017, we selected 19 snorkeling sites in South Carolina (below, right).

Methods to identify nesting preferences

Process of sampling from left to right, continuing down
  • Snorkel 300 meter stretches of river upstream in a zig-zag pattern
  • Mark location of each nest found and complete survey
  • Return to nest and attempt to capture guarding parent
  • Take fin clip, length, and weight of parent
  • Record water velocity, water depth, and collect substrate measurements at each nest
  • Collect eggs for genetic analyses
  • Preserve eggs in 200 proof ethanol

Attempting to capture bass off nest

One nest found in the larval stage

  • Quantifying available microhabitat using habitat transects across river sections at nest locations
Transects across river segments at nest locations to determine habitat availability. Nests are represented by red stars, the transects are represented by the yellow line overlaid.

Results from 2017 season

Chi-squared analyses of substrate use vs. availability. This shows that bass selected for mainly silt and cobble when all substrates were relatively distributed evenly among sample locations.
Velocity and depth used vs. available. A small range of both velocity (<0.5 m/s) and depth (0.5-1.5 m) was used by nesting bass. However, the depths and velocities available were both much more widespread.
Generalized linear mixed model of velocity with a random effect of nest ID. This shows that the velocities utilized for nesting only made up a small amount of those available in the environment.
Generalized linear mixed model of depth with a random effect of nest ID. This shows that bass utilized a wide range of depths compared to those available in their environment.

Major Findings

  • Bartram's Bass utilize a wide range of substrates, but select for silt and cobble most frequently.
Above: cobble nest with eggs, below: silt/detritus nest with larvae
  • Bartram's Bass use a wide range of water depths, between 0.5 and 1.5 meters.
  • Individuals select for slower velocities, typically less than 0.5 meters per second. We believe velocity is the driving factor for substrate use, meaning that bass may nest more frequently over silt and cobble because they are selecting for slow moving water.

Methods to assess spatial ecology of hybridization

  • Over 60 sites were sampled in 2017 using electrofishing and hook & line sampling methods
  • Fin clips were collected from each fish captured
  • Tissue is currently being analysed for genetic determination (pure Bartram's Bass, pure Alabama Bass, or hybrid)
  • Land use and other watershed data will be analyzed with genetic distribution to create a species distribution model
Example of how a species distribution model is formed (Smyth, R. 2014).

Future Work

Genetic analyses are underway to provide species determination for each individual and nest sampled
2018 field season
Complete species distribution model with genetic data and watershed level factors

Other Projects

Diet analyses of Bartram's Bass
Age and growth of Bartram's Bass

Acknowledgements

Thank you to all those who provided support in the field, especially my technicians: David Bell, Alex Michaeli, Wesley Moore, our AFS Hutton Scholar Kristin Abernathy, and my advisor Dr. Brandon Peoples.

From left: Alex Michaeli, Wesley Moore, David Bell
From left: Brandon Peoples, Kristin Abernathy, Emily Judson

Partners

References

Freeman, B., A. Taylor, K.Oswald, J. Wares, M. Freeman, J. Quattro, and J. Leitner. 2013. Shoal Basses, a clade of cryptic identity.

Oswald, K.J. 2007. Phylogeography and contemporary history of Redeye Bass (Micropterus coosae). Ph.D. Dissertation, University of South Carolina.

Oswald, K., J.Leitner, D. Rankin, D. H. Barwick, B. Freeman, T. Greig, M. Bangs, and J. Quattro. 2015. Evolutionary genetic diversification, demography, and conservation of Bartram’s Bass.

Smyth, R. 2014, February 5. Species Distribution Modeling.

Created By
Emily Judson
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