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 m 2 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.

No abstract

Deterministic fitness, stochasticity, speciation, and dispersal regulate biotic communities within streams at local, regional, and continental scales (Vellend 2010). Anthropogenic modifications to streams often disrupt these regulatory processes and contribute to the current state of crisis facing freshwater biodiversity (Dudgeon et al. 2006). Reductions in the abundance and distribution of freshwater fishes are particularly notable (Helfman 2007). In North America, nearly 40% of freshwater and diadromous fishes are imperiled (i.e., at risk of population decline or extinction; Jelks et al. 2008); in the southwestern USA, >50% of stream

An experiment is described which studies the dynamical behavior of a soft spring. This experiment has proved valuable as a project in a junior or senior physics laboratory. The results demonstrate the inadequacy of both the elementary formula for the period and the modified formula containing a correction term for the mass of the spring. A simple theoretical model is presented which yields results in agreement with experiment. The analysis uses mathematics that the students have been learning in parallel courses. The simplicity of the experiment serves to highlight the interplay of physics and mathematics. Most physics departments already have the elementary equipment needed.

No abstract