Natural Mortality Dynamics in Fish Populations

Natural mortality, the rate at which fish perish from non-fishing causes, is a fundamental driver of population dynamics and fisheries sustainability. It encompasses losses due to predation, disease, senescence and environmental stressors, and varies with age, size, habitat and species life-history traits. In many stocks, mortality is density-dependent, rising when populations are abundant and falling at low densities, yet density-independent factors such as temperature extremes or hypoxia can induce abrupt mortality pulses. Accurately quantifying natural mortality is hindered by its invisibility in fishery catches and by the confounding effects of growth variability, ageing error and recruitment fluctuations. As a result, stock assessment models often rely on indirect life-history estimators or tagging and telemetry data to infer mortality rates. Recent advances have improved the integration of mark–recapture and acoustic telemetry observations with growth functions to yield age- and stage-specific mortality profiles. These developments strengthen projections of stock productivity, inform harvest control rules and guide rebuilding strategies for depleted stocks. By illuminating how natural mortality responds to environmental change and anthropogenic pressure, these insights promote adaptive management across marine and freshwater systems worldwide.

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Natural Mortality Dynamics in Fish Populations publication trend

The graph below shows the total number of articles in natural mortality dynamics in fish populations across all publications each year (not limited to Nature Index journals).

Technical terms

Natural mortality (M): The instantaneous rate at which individuals die from non-fishing causes, expressed per year.

Stock assessment model: A quantitative framework that integrates biological and fishery data to estimate population size, productivity and sustainable harvest levels.

Mark–recapture: A method estimating survival by tagging individuals, releasing them and recording subsequent recaptures or detections.

Acoustic telemetry: A tracking technique in which fish carry acoustic transmitters, allowing remote detection of movement and survival.

von Bertalanffy growth function: A mathematical model describing individual length increase over time, often used to infer age and growth-related mortality patterns.

References

1. Informing Management of Atlantic Bluefin Tuna Using Telemetry Data. Frontiers in Marine Science (2022).
2. Times are changing, but has natural mortality? Estimation of mortality rates for tropical tunas in the western and central Pacific Ocean. Fisheries Research (2022).