Movement and mortality of invasive suckermouth armored catfish during a spearfishing control experiment

Abstract

Control of non-native, invasive species in groundwater-dependent ecosystems that are also inhabited by regionally endemic or at-risk species represents a key challenge in aquatic invasive species management. Non-native suckermouth armored catfish (SAC; family Loricariidae) have invaded freshwater ecosystems on a global scale, including the groundwater-dependent upper San Marcos River in Texas, USA. We used passive integrated transponder tags to follow the movements and fates of 65 fish in a 1.6 km spring-fed reach of the upper San Macros River to assess the efficacy of a community-based spearfishing bounty hunt for controlling SAC. We found the weekly probability of SAC survival was negatively correlated with the number of fish removed as a part of the bounty hunt each week (P = 0.003, R ² = 0.86), while the probability of SAC being speared and reported was positively correlated with the number of fish removed (P = 0.011, R ² = 0.53). The majority of SAC used < 25 m² of river over a nine-week tracking period, but the area of river fish used correlated positively with the number of relocations (P < 0.001, R ² = 0.36) as might be expected for a population that disperses through diffusive spread. These findings collectively suggest local-scale suppression of the SAC population is possible through community engagement in spearfishing, but over longer time periods immigration might offset some of the removal success. This conclusion provides an explanation for the pattern in which long-term spearfishing tournaments have reduced biomass but ultimately not resulted in eradication of the population.

Supplementary information: The online version contains supplementary material available at 10.1007/s10530-022-02834-2.

Keywords: Efficacy of population suppression; Mark–recapture; Movement ecology; Survival analysis; Telemetry.

Fig. 1

Study area map illustrating a the location of the San Marcos River in the US and Texas, b the upper San Marcos River with four scanning locations where searches for tagged fish occurred, including c Spring Lake Dam, d Sewell Park, e City Park, and f Rio Vista Park. Red lines in c–f represent the banks that were scanned for suckermouth armored catfish during nine relocation attempts

Fig. 2

Underwater tracking relocations of tagged suckermouth armored catfish in the San Marcos River, Texas, USA. Focal sampling sites from upstream to downstream include a Spring Lake Dam, b Sewell Park, c City Park, and d Rio Vista Park. Relocations are shown as cross symbols (+) and the relative density of relocations is shown as a heat map ranging from high (red) to low (blue) densities of points. Some points fall outside the polygon of the river but represent locations of fish within the water. Photographs of bank alterations at focal sampling sites are shown from the perspective of the red arrows in the heat maps (photographs by AAH)

Fig. 3

a Frequency histogram comparison for sizes of all fish tagged (dark gray, n = 115) and fish relocated at least once (light gray, n = 65), b frequency histogram of the area used (m²) by the 65 relocated fish, and c relationship between number of relocations and area used by the 65 relocated fish tracked in the upper San Marcos River, Texas, USA. The relationship in panel c is summarized with a generalized linear regression model (black line) and 95% confidence interval (gray shaded area)

Fig. 4

Relationship between the number of fish speared during weekly bounty hunt periods versus a the probability that a fish survived a given week and b the probability that a fish was speared and reported based on the tag recovery model by Brownie et al. (1985). Points represent weekly time points between August 30, 2020 and December 5, 2020, black lines are fitted values from a generalized linear model, and gray shaded areas represent 95% confidence intervals