Effective monitoring of freshwater fish

Abstract

Freshwater ecosystems constitute only a small fraction of the planet's water resources, yet support much of its diversity, with freshwater fish accounting for more species than birds, mammals, amphibians or reptiles. Fresh waters are, however, particularly vulnerable to anthropogenic impacts, including habitat loss, climate and land use change, pollution and biological invasions. This environmental degradation, combined with unprecedented rates of biodiversity change, highlights the importance of robust and replicable programmes to monitor freshwater fish. Such monitoring programmes can have diverse aims, including confirming the presence of a single species (e.g., early detection of alien species), tracking changes in the abundance of threatened species, or documenting long‐term temporal changes in entire communities. Irrespective of their motivation, monitoring programmes are only fit for purpose if they have clearly articulated aims and collect data that can meet those aims. This review, therefore, highlights the importance of identifying the key aims in monitoring programmes and outlines the different methods of sampling freshwater fish that can be used to meet these aims. We emphasize that investigators must address issues around sampling design, statistical power, species’ detectability, taxonomy and ethics in their monitoring programmes. Additionally, programmes must ensure that high‐quality monitoring data are properly curated and deposited in repositories that will endure. Through fostering improved practice in freshwater fish monitoring, this review aims to help programmes improve understanding of the processes that shape the Earth's freshwater ecosystems and help protect these systems in face of rapid environmental change.

Standards for Methods Utilizing Environmental DNA for Detection of Fish Species

“…The promising applications of eDNA for monitoring aquatic biodiversity including fishes or their communities have been extensively reviewed [1,2,5,8,[12][13][14][15][16][17][18][19][20][21][22][23]. With respect to eDNA, fish are currently the most studied group of macro-organisms in aquatic ecosystems [24].…”

Interpretation of interannual variability in long-term aquatic ecological surveys

“…Improved analyses of the drivers of short-term population dynamics would require more exhaustive and specific monitoring methods, involving intensive sampling at a finer temporal scale. Alternative approaches would be to combine LTES with intensive continuous sampling during specific periods corresponding to particular life stages (e.g., fish recruitment), or measure population dynamic through individual tracking using telemetry devices or markrecapture techniques to estimate the probability of detection of species, thereby assessing the observation error of the LTES for a given population (Capra et al 2018;Radinger et al 2019). dots represent a standardized fish density time series.…”

Negative feedback concept in tagging: Ghost tags imperil the long-term monitoring of fishes

“…For instance, fish activity measured by number of detections per time period can be influenced due to a lower probability of detection late in the reproductive season, when expelled PIT tags have accumulated in the environment and prevent detection of tagged fish [18,35]. This is in conflict with the actual purpose of many longterm studies, where the same sampling scheme (and therefore antenna positions) should be maintained to compare data between years [47,48].…”