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# Six thousand recorder-days reveal overlapping but different whale seasons in the Mascarene waters
- URL: https://intelligence.wildlandseco.com/2026-10-04-mascarene-whale-seasonal-acoustics/
- Published: 2026-10-04T13:59:24.000Z
- Updated: 2026-10-04T13:59:24.000Z
- Description: Passive acoustics found fin, Antarctic blue and Madagascar pygmy blue whale songs across all sampled sites, with strong seasonality and much sparser Antarctic-blue occurrence.
- Author: Benjamin Worlund
- Tags: whales, Passive acoustics, Indian Ocean, seasonality, marine monitoring, migration, Monitoring, #ecological-intelligence, #brief-2026-10-04, #global-radar

Evidence

Peer-reviewed passive-acoustic monitoring study

Geography

Mascarene waters, southwestern Indian Ocean

System

Open-ocean marine mammal habitat

## WHAT THE EVIDENCE SAYS

Sixteen ocean-bottom recorders provided more than 6,000 days of recordings. Fin-whale 20-Hz songs occurred on an average 43% of recording days and could span up to roughly eight months at a site. Antarctic blue-whale songs were detected at all sites but on about 13% of recording days on average, concentrated mainly outside austral spring–summer, with geographic exceptions. Madagascar pygmy blue whales also showed strong seasonal occurrence.

## WHY IT MATTERS / OUR READ

Sparse visual sightings can make a marine corridor look empty. Long-duration passive acoustics reveals when different large whales overlap the same broad seascape and can help time surveys, shipping-risk assessment or other monitoring around actual seasonal presence.

## CAVEATS / UNCERTAINTY

Acoustic presence is not abundance, and calling behavior varies by species, sex, season and context. Recorder placement and detectability also shape apparent occurrence, so silence cannot be treated as confirmed absence.

## SOURCE

ICES Journal of Marine Science — primary study  
[View original evidence ↗](https://doi.org/10.1093/icesjms/fsag192?ref=intelligence.wildlandseco.com)

From the Morning Brief · 2026-10-04

[Read the full Morning Brief →](https://intelligence.wildlandseco.com/morning-brief-2026-10-04/)