Marine Megafauna Foundation — Whale Shark Shipping Risk

Whale Shark Shipping Risk

Marine Megafauna Foundation · prototype v1

This map shows live cargo-and-tanker traffic against 96 whale shark hotspots: the 74 IUCN-recognised Important Shark and Ray Areas (ISRAs) where whale sharks (Rhincodon typus) aggregate, feed, give birth, or transit, plus 22 additional Womersley aggregation sites that fall outside the ISRA network (the ISRA programme has not yet workshopped the North American Atlantic, African Atlantic, or North American Pacific regions). Sharks and ships sharing the same patch of ocean is the dominant unrecognised driver of whale shark mortality worldwide; this map exists to make that overlap visible in real time.

Hotspot polygons

Polygons are sourced from the IUCN Shark Specialist Group's Important Shark and Ray Areas portal. Coverage spans nine published regions (Western Indian Ocean, Asia, Central & South American Pacific, Australia/Oceania, European Atlantic, South American Atlantic, plus zero-whale-shark regions for completeness). The North American Atlantic, African Atlantic, and North American Pacific regions are not yet workshopped by the ISRA programme. Each polygon's popup links to its full IUCN factsheet — click any hotspot to see it.

Vessel positions

Live AIS positions arrive from aisstream.io via a same-origin Cloudflare proxy. Only AIS Class A vessels are shown — that's cargo, tankers, passenger ferries, fishing vessels above ~300 GT, towing, HSC, and large pleasure craft. Smaller Class B traffic (recreational, small fishing) is not transmitted with enough fidelity to be useful. Vessels at port or anchor (speed below 1 knot) are filtered out. Coverage is global. Vessel-day accumulation (the 30 d / 365 d counts in each hotspot card) is narrowed to the ISRA buffer bboxes server-side to stay within the Durable Object request budget; the live map shows every vessel aisstream reports anywhere on Earth.

The 10 km buffer

Each hotspot is rendered with a 10 km dashed buffer ring. A vessel inside the polygon is an immediate strike risk; a vessel inside the buffer ring is a near-zone risk. The 10 km value is MMF's working choice and is more conservative than Womersley et al. (2022)'s 100 km radius used in the original collision-risk modelling.

Key papers

Womersley et al. (2022). Global collision-risk hotspots of marine traffic and the world's largest fish, the whale shark.

Proc. Natl. Acad. Sci. USA 119: e2117440119. doi:10.1073/pnas.2117440119 · The foundational paper. 348 tracked whale sharks vs. global AIS traffic; 92% horizontal-space overlap with persistent large-vessel traffic.

Womersley et al. (2024). Identifying priority sites for whale shark ship collision management globally.

Sci. Total Environ. 934: 172776. doi:10.1016/j.scitotenv.2024.172776 · The priority-sites paper. Identifies the constellation of ~50 highest-risk aggregation sites that informed v1's polygon scope. The red core-habitat and orange 100 km buffer-zone layers rendered on the map above are from this paper's supplementary data (Tables S7 / S8).

IUCN Red List — Rhincodon typus. Global whale shark distribution.

iucnredlist.org/species/19488/2365291 · The light-blue ocean tint on the map approximates the species' global range, derived from the IUCN Red List assessment.

Womersley et al. (2024). Climate-driven global redistribution of an ocean giant predicts increased threat from shipping.

Nat. Clim. Change 14: 1–10. doi:10.1038/s41558-024-02129-5 · Projects how warming oceans push whale sharks into busier shipping lanes by 2100.

Vessel-day accumulation

The 30 d and 365 d counts in each hotspot card are unique vessel-days — one row per ship per UTC day per hotspot. A ship sitting inside a polygon for 8 hours counts as one vessel-day; a ship visiting the same hotspot on two consecutive days counts as two. Accumulated server-side by a Cloudflare Durable Object holding a persistent connection to aisstream. The sidebar list re-ranks by 30-day vessel-day pressure once data is available, falling back to the live snapshot in the meantime.

Bootstrap period: the 30 d window fills in over the first 30 days from launch; the 365 d window over the first year. Hotspot cards show "X days of data so far" until the windows are complete.

Prototype — not for partner circulation without board endorsement. Built by Marine Megafauna Foundation. Polygon data © IUCN SSC Shark Specialist Group; basemap © OpenStreetMap contributors / CARTO.