Population Assessment Methods for Freshwater Fisheries

Accurate estimation of fish populations underpins the sustainable management of rivers, lakes and reservoirs worldwide. Techniques range from direct approaches, such as mark–recapture and depletion sampling, to indirect indices, such as catch per unit effort (CPUE) and hydroacoustic surveys. Emerging methods, including environmental DNA (eDNA) analysis and telemetry, allow non-invasive detection and fine-scale movement tracking. Statistical and mechanistic frameworks integrate these diverse data streams: hierarchical models correct for imperfect detectability and seasonal variability, while size- or age-structured models—such as integral projection models—exploit growth and survival information to forecast population dynamics. Each approach carries trade-offs in precision, cost and logistical complexity; for example, hydroacoustics can rapidly survey large volumes but may struggle in structurally complex habitats, whereas mark–recapture yields robust estimates for closed systems but demands extensive field effort. Hybrid strategies increasingly combine survey indices with spatial habitat models and environmental covariates to improve predictive capacity. Across temperate and tropical regions, practitioners tailor method selection to species life histories, habitat characteristics and management objectives, whether for threatened species assessment, invasive species control or sport-fishery quotas.

Research from Nature Portfolio

No recent Nature Portfolio content available.

Population Assessment Methods for Freshwater Fisheries publication trend

The graph below shows the total number of articles in population assessment methods for freshwater fisheries across all publications each year (not limited to Nature Index journals).

Technical terms

Catch per unit effort (CPUE): Index of relative abundance calculated as the number of fish caught per unit of sampling effort, such as hours of electrofishing or net sets.

Detectability: Probability of capturing or detecting an individual fish during a survey, influenced by environmental conditions, gear efficiency and fish behaviour.

Integral projection model (IPM): A demographic model that projects growth, survival and reproduction continuously across individual sizes, enabling fine-scale predictions of population change.

Hyperstability: A sampling artefact in which catch rates remain stable or even increase as true population density declines, often due to behavioural aggregation or gear saturation.

Mark–recapture: A method in which individuals are captured, uniquely marked, released and later re-captured to estimate total population size based on the proportion of marked fish recaptured.

References

1. An integral projection model for gizzard shad (Dorosoma cepedianum) utilizing density-dependent age-0 survival. Ecological Modelling (2023).
2. Hyperstability in Electrofishing Catch Rates of Common Carp and Bigmouth Buffalo. North American Journal of Fisheries Management (2022).
3. Intra‐Annual Variability of Common Carp and Bigmouth Buffalo Electrofishing Data in Shallow Lakes. North American Journal of Fisheries Management (2023).