The ecological relevance of critical thermal maxima methodology for fishes.

Critical thermal maxima methodology (CTM) has been used to infer acute upper thermal tolerance in fishes since the 1950s, yet its ecological relevance remains debated. In this study, the authors synthesize evidence to identify methodological concerns and common misconceptions that have limited the interpretation of critical thermal maximum (CT ; value for an individual fish during one trial) in ecological and evolutionary studies of fishes. They identified limitations of, and opportunities for, using CT as a metric in experiments, focusing on rates of thermal ramping, acclimation regimes, thermal safety margins, methodological endpoints, links to performance traits and repeatability.

Looking where it's hard to see: a case study documenting rare Eucyclogobius newberryi presence in a California lagoon.

Environmental DNA (eDNA) analysis is increasingly used for biomonitoring and research of fish populations and communities by environmental resource managers and academic researchers. Although managers are much interested in expanding the use of eDNA as a survey technique, they are sceptical about both its utility (given that information is often limited to presence/absence of a species) and feasibility (given the need for proper laboratory facilities for sample processing). Nonetheless, under the right circumstances, eDNA analysis is cost-effective compared to many traditional aquatic survey methods and does not disturb habitat or harm the animals being surveyed.

Maxed Out: Optimizing Accuracy, Precision, and Power for Field Measures of Maximum Metabolic Rate in Fishes.

Both laboratory and field respirometry are rapidly growing techniques to determine animal performance thresholds. However, replicating protocols to estimate maximum metabolic rate (MMR) between species, populations, and individuals can be difficult, especially in the field. We therefore evaluated seven different exercise treatments-four laboratory methods involving a swim tunnel (critical swim speed [], postswim fatigue, maximum swim speed [], and postswim fatigue) and three field-based chasing methods (3-min chase with 1-min air exposure, 3-min chase with no air exposure, and chase to exhaustion)-in adult coho salmon () as a case study to determine best general practices for measuring and quantifying MMR in fish.

Measuring global fish species richness with eDNA metabarcoding.

Despite mounting threats to global freshwater and marine biodiversity, including climate change, habitat alteration, overharvesting and pollution, we struggle to know which species are present below the water's surface that are suffering from these stressors. However, the idea that a water sample containing environmental DNA (eDNA) can be screened using high-throughput sequencing and bioinformatics to reveal the identity of aquatic species is a revolutionary advance for studying the patterns of species extirpation, invasive species establishment and the dynamics of species richness. To date, many of the critical tests of fisheries diversity using this metabarcoding approach have been conducted in lower diversity systems (<40 fish species), but in this issue of Molecular Ecology Resources, Cilleros et al.