17 Feb 2026

Fish eDNA levels rise with biomass in tanks, but not in a straight line

Sensors, imaging and electronic skin
AI illustration · Illustrative scene, not a photograph of the specific device or experiment.

What was demonstrated

In controlled flow-through tanks, researchers added fish two at a time every 48 hours, rising from 2 to 12 fish per tank. The trials used three freshwater species (Squalius lucumonis, Lepomis gibbosus and Pseudorasbora parva), with three tanks per species, and ran in 2024. Each 2 L water sample was filtered and its eDNA measured by real-time qPCR with triplicate reactions. Generalised additive mixed models (GAMMs) found monotonic nonlinear relationships between eDNA concentration and biomass in all three species. Two species levelled off at intermediate biomass. Biomass partial R-squared values were 0.420 (L. gibbosus), 0.623 (P. parva) and 0.613 (S. lucumonis).

Why it matters

Surveys that use eDNA to estimate how much animal biomass is present may need models that curve, not simple straight-line calibrations. The result suggests eDNA may indicate relative biomass in controlled settings, but it does not show that the same relationship holds in rivers, lakes or ponds.

Caveats

  • Each species was tested on its own, and the trials did not feed the fish. Multi-species communities and natural waters were not tested.
  • The authors acknowledge suboptimal qPCR efficiencies (73.1% to 78.1%). They say the high R-squared values still confirmed strong internal consistency.
  • The authors attribute replicate variability to differences in eDNA shedding rates between and within individual fish, and say shedding-related factors cannot be ruled out. They stress that replication is needed.
  • The authors note that log transformations, often used to linearise such relationships, may mask the nonlinear pattern reported here. They call for validation in natural systems.

Technology profiles

Sources

  1. peer reviewed paper
    Controlled Experiments Reveal Moderate, Nonlinear Relationships Between eDNA Concentration and Fish Biomass in Three Freshwater Species of Monitoring Relevance
    Lorenzo Talarico, Gerardo Petrosino, Anna Rita Rossi et al.. Ecology and Evolution, 17 Feb 2026. DOI: 10.1002/ece3.73129.
  2. peer reviewed paper
    Controlled Experiments Reveal Moderate, Nonlinear Relationships Between eDNA Concentration and Fish Biomass in Three Freshwater Species of Monitoring Relevance (open-access full text)
    Lorenzo Talarico, Gerardo Petrosino, Anna Rita Rossi et al.. PubMed Central, 17 Feb 2026. DOI: 10.1002/ece3.73129.

Last reviewed 21 Oct 2026.