Introduced Suckermouth Armored Catfish (SAC; family Loricariidae) have invaded freshwater ecosystems globally. In the San Marcos River, Texas, control of invasive SAC includes spearfishing through public tournaments and contracted spearfishing, yet the effectiveness of these control efforts is unquantified. We used a recently developed length-based Bayesian biomass estimation method to assess spearfishing mortality relative to natural mortality and existing biomass relative to an unexploited population. During 2014-2018, 6,046 SAC were removed and measured (total length, cm) from the San Marcos River through spearfishing. Using the length-based Bayesian biomass, we found fishing pressure increased mortality 1.50-to 1.75-fold relative to natural mortality, and that relative biomass during 2016-2018 was significantly below the threshold at which stock depletion occurs. Our application of fishery stock assessment provides quantitative benchmarks for invasive species control and can be applied to other invaded systems where control methods are unassessed but length data from removed individuals are available.

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Aquifers and spring complexes within the arid and semi‐arid karst Edwards Plateau region of Texas are evolutionary refugia supporting a large number of endemic flora and fauna. Spring fishes, many of which are endemic, are associated with the spring complexes, whereas river fishes generally avoid spring complexes. Purposes of this study were to experimentally test affinities of spring fishes and river fishes for spring complexes and rivers among six independent spring‐river systems of the Edwards Plateau and to quantitate relationship among spring fishes, river fishes and spring flow magnitude within spring complexes. We found that spring fishes did not exclusively use spring complexes but were more abundant in spring complexes than rivers and that species richness, relative abundance, and density of spring fishes were directly related to spring flow magnitude. Patterns in affinities for river fishes were less distinct. Quantitation of fish–habitat relationships will assist efforts in conserving aquatic resources within the Edwards Plateau and provides predictive models to assess biological integrity of other spring complexes. In addition, consistency in distributional patterns of spring and river fishes provides a framework for testing underlying processes of species segregation and diversification, establishes boundaries of aquatic evolutionary refugia, and expands the value of evolutionary refugia from historical refugia to contemporary and future refugia for Edwards Plateau aquatic biota.

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