1. Dam construction threatens global aquatic biodiversity by fragmenting stream networks and altering flow regimes. The negative effects of dams are exacerbated by increased drought periods and associated water withdrawals, especially in semi-arid regions. Stream fishes are particularly threatened owing to their mobile nature and requirement for multiple habitats to complete their life cycles. An understanding of relationships with fragmentation and flow regimes, particularly as coarse-scale (e.g. catchment) constraints on species distributions, is essential for stream fish conservation strategies. Prairie chub (Macrhybopsis australis) is a small-bodied minnow (Cyprinidae) with poorly understood ecology endemic to the North American Great Plains.Suspected declines in abundance and extirpations have resulted in conservation interest for prairie chub at state and federal levels. Prairie chub is thought to share its reproductive strategy with pelagic-broadcast spawning minnows (pelagophils). Freshwater pelagic-broadcast spawning fishes have been disproportionately affected by fragmentation and streamflow alteration globally.3. Relationships of prairie chub occurrence with coarse-scale fragmentation and streamflow metrics were examined in the upper Red River catchment. Occurrence probability was modelled using existing survey data, while accounting for variable detection. The modelled relationships were used to project the distribution of prairie chub in both a wet and dry climatic period.4. The probability of prairie chub occurrence was essentially zero at sites with higher densities of upstream dams, but increased sharply with increases in flow magnitude, downstream open mainstem, and flood duration. The projected distribution of prairie chub was broader than indicated by naïve occurrence, but similar in both climatic periods. The occurrence relationships are consistent with the hypotheses of pelagic broadcast spawning and represent coarse-scale constraints that are useful for identifying areas of the stream network with higher potential for finer-scale prairie chub conservation and recovery efforts. In addition to informing pelagophil conservation, the relationships are also applicable to pelagic-broadcast spawning fishes in marine environments.

Biological invasions are increasing in frequency and the need to mitigate or control their effects is a major challenge to natural resource managers. Failure to control invasive species has been attributed to inadequate policies, resources or scientific knowledge. Often, natural resource managers with limited funds are tasked with the development of an invasive species control program without access to key decision-support information such as whether or not an invasive species will cause damage, and what the extent of that damage may be. Once damages are realized, knowing where to allocate resources and target control efforts is not straightforward. Here we present the history of invasive species policy development and management in a large, multi-jurisdictional and multi-use aquatic ecosystem. We present a science-based decision-support tool for on-the-ground aquatic invasive species (AIS) control to support the development of a sustainable control program. Lastly, we provide a set of recommendations for managers desiring to make an AIS control implementation plan based upon our development of novel invasive species research, policy and management in Lake Tahoe (USA). We find that a sustainable invasive species control program is possible when science, coordination and outreach are integrated.

Knowledge of crayfish species’ life history traits is vital to their conservation and management. Fecundity is one trait that is a likely indicator of extinction risk and potential invasiveness. Fecundity-related data are lacking for the imperiled St. Francis River crayfish (Faxonius quadruncus) that is declining in the presence of the invasive woodland crayfish (Faxonius hylas). We sampled ovigerous females in three populations each of F. quadruncus and invasive F. hylas in Missouri (USA) Ozarks streams during April 2014 to compare fecundity and egg size between the two species. Differences in fecundity-related traits existed among populations of F. quadruncus, but no differences existed between the species. Results for both species were well within the ranges reported for other Faxonius species, but likely reflect small sample sizes rather than the entirety of each species. We also investigated the utility of field versus laboratory fecundity measures and found that field egg counts on live females varied among observers and also underestimated laboratory counts by an average of 22%. We provide a linear equation that can serve as a correction adjustment for field pleopodal fecundity estimates on live females to avoid specimen sacrifice during future monitoring of these species.

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A multiscale perspective is essential for conservation planning of riverine fishes. Coarse-scale habitat (e.g., basis) can influence both finer-scale habitat characteristics (e.g., reaches and microhabitat) and associated species distributions. Finer-scale management and habitat rehabilitation efforts can fail without the consideration of coarser-scale constraints. We provide a conceptual hierarchical framework for multiscale fish conservation strategies in the semiarid Great Plains. The Great Plains stream network is highly fragmented due to dam construction, water withdrawals, and increased drought severity. Our framework uses relationships with basin-scale connectivity and streamflow and reach-scale physicochemical characteristics in the context of aiding species reintroduction and stream habitat improvements.