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# Harbour porpoises detected a net but still approached it closely
- URL: https://intelligence.wildlandseco.com/2026-10-15-harbour-porpoise-gillnet-detection-versus-avoidance/
- Published: 2026-10-15T17:50:13.000Z
- Updated: 2026-10-15T17:50:13.000Z
- Description: Drone and acoustic observations challenge the assumption that bycatch is simply a sensory detection failure.
- Author: Benjamin Worlund
- Tags: harbour porpoise, gillnet bycatch, animal behavior, Oceans, Wildlife, Methods, #ecological-intelligence, #brief-2026-10-15, #global-radar, #peer-reviewed, #geo-europe

Evidence

Peer-reviewed

Geography

Harbour porpoise experimental observations; northern European waters

System

Coastal fisheries; marine mammal bycatch behavior

## WHAT THE EVIDENCE SAYS

In a field experiment using a dummy bottom-set gillnet, researchers filmed and recorded harbour porpoises approaching the net with and without an acoustic alerting device. Animals often crossed above the float line and avoided direct contact at observed distances of roughly 0.8–16.4 m; speed, breathing and echolocation changed little.

## WHY IT MATTERS / OUR READ

Bycatch prevention may need to improve how animals choose evasive paths, rather than only making a net detectable. An audible signal is not evidence that a dangerous encounter has been prevented.

## CAVEATS / UNCERTAINTY

A dummy net under observation is not an operational catch trial. The experiment did not measure real-world bycatch reduction or all commercial net configurations.

## SOURCE

Journal of Applied Ecology · harbour porpoise field experiment  
[View original evidence ↗](https://doi.org/10.1111/1365-2664.70592?ref=intelligence.wildlandseco.com)

From the Morning Brief · 2026-10-15

[Read the full Morning Brief →](https://intelligence.wildlandseco.com/morning-brief-2026-10-15/)