Mauritius - Lost Anchor
Part of the regional summary: Mauritius
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Southern Mauritius (NOAA CRW virtual station)A low-relief boulder field off Coin de Mire in northern Mauritius, where most surfaces are turf and coralline crust rather than living coral. It is punctuated by a stand of large sea fans and a lone healthy staghorn thicket on sand, with a whitemouth moray and a probable camouflaged octopus among the sightings.
Un champ de blocs à faible relief au large du Coin de Mire, dans le nord de Maurice, où la plupart des surfaces portent du gazon algal et des croûtes corallines plutôt que du corail vivant. Il est ponctué d'un ensemble de grandes gorgones et d'un unique massif d'acropores branchus en bonne santé sur le sable ; une murène à bouche blanche et un poulpe probablement camouflé comptent parmi les observations.
Traduction par IA de ce résumé ; la version anglaise fait foi.
Seven independent survey stations shown with the program’s logo — click one to see how far it is from this site.
One other CRD dive site with its own page within 5 km shown in orange — click a marker to open its page.
12 of the 45 photographs on this page are shown beside the text that discusses them under "Site description" below.
Site description
General benthic features
Lost Anchor (Coin de Mire) is a low-relief boulder field: turf- and coralline-encrusted boulders and dead reef framework cut by sand and rubble channels, with manually scored point-count cover of 11% hard coral (e.g., Image 4, Image 5, Image 9, Image 17).
Live colonies are mostly small lavender branching colonies and massive dome-shaped colonies, punctuated by a stand of large gorgonian sea fans and a lone healthy staghorn thicket on sand (e.g., Image 1, Image 2, Image 3, Image 13).
Coral cover
- Reference: Mayfield et al. (2026, Platax), Table 3 (manuscript in preparation)
- CoralNet submission package
- Coral cover: 11% — Anderson Mayfield's manual point count of the photographs (Mayfield et al. 2026 Platax Table 3).
Stressors
No widespread bleaching was evident. A few colonies were bleached, and Anderson's own point annotations label them bleached hard coral: two small branching colonies, white over most of their branches beside pigmented neighbors (e.g., Image 8, Image 12), and a massive colony with inflated, uniformly gray-white polyps (e.g., Image 38).
Several soft corals with white stalks and white, translucent polyps were also bleached (photo not shown; Anderson's annotations label them bleached invertebrates). No crown-of-thorns starfish (COTS) or other corallivores were evident.
Fish and other fauna
Notable sightings included a whitemouth moray, a probable camouflaged octopus, Diadema-type urchins, and dense clouds of chromis and damselfish; no widespread bleaching was evident (e.g., Image 16).
Comparisons with other data
University of Mauritius and WCS Kenya (via MERMAID) surveyed a nearby station (Coin de Mire) in 2019, 0.27 km from the pin. Within 5 km, seven independent stations recorded hard coral cover between 1999 and 2019: two by benthic survey, station-year means of 46–89%, and five by MERMAID bleaching-protocol quadrats, station-year means of 10–98%; the nearest, WCS Kenya / University of Mauritius via MERMAID (quadrats) at Coin de Mire, 0.27 km away, read 10% in 2019.
CV model comparison
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That convention would raise every Mauritius site by 0–3.7 pp. The Claude row is the manuscript's Claude (with image context) value, scored on the same frames as the manual count; one of its five sets of context images had been seen before, so it is not fully blind. Anemone Garden is anemone habitat rather than coral reef; its manual value stands but carries no error term. CoralSCOP (SAM-based mask-sum), edited photos: n/a — no edited copies exist; all 347 Mauritius photographs are unedited.| Method | Hard coral cover (%) | Photos (n) ± SE |
|---|---|---|
| Manual (reference) | 11.0 | |
| CoralNet | 10.0 | n = 39 |
| Coralscapes v1 | 11.9 | |
| CoralSCOP | 20.5 | n = 39 |
| DINOv3 | 20.3 | n = 39 |
| Claude (context) | 9.2 | n = 39 |
The four computer-vision methods disagree by 11.3 pp (9.2–20.5%) and read on both sides of the manual point count (11.0%); the headline is the manual point count because a person's point count of the site's photographs is the reference the models are measured against.
The Coralscapes v1 row is shown for reference only, outside this comparison.
See a more detailed, stand-alone version of this table.
Independent surveys nearby
| Agency / program | Year(s) | Stations / distance | Link |
|---|---|---|---|
| Reef Check | 1999 | 1 station, 3.06 km | Records ↓ |
| Surveyor not identified (2016 Indian Ocean bleaching survey) | 2016 | 1 station, 3.59 km | Records ↓ |
| WCS Kenya / University of Mauritius via MERMAID (MERMAID bleaching-protocol quadrats) | 2019 | 3 stations, 0.27–4.19 km | Records ↓ |
| WCS via MERMAID (MERMAID bleaching-protocol quadrats) | 2016 | 2 stations, 3.64–4.86 km | Records ↓ |
Coral Reef DiagnosticsYear-average (illustrative only, programs differ; quadrats left out)Within 5 km, 7 independent survey stations recorded hard coral cover in 8 surveys between 1999 and 2019. The most recent nearby survey is from 2019, so these values predate recent heat stress. This site's own estimate (11%) sits 1 point above the one survey station up to 2 km away with MERMAID bleaching-protocol quadrats (10%); the methods differ, so the comparison is context, not a like-for-like test.
Collected by other programs using different methods (Reef Check uses point-intercept transects; MERMAID is a data platform: each MERMAID row names the organization that did the survey, and its method is in the row's hover text), so these are context for the figures above, not a like-for-like comparison. Where a station was surveyed more than once, the cell shows either the range of its values or, as a single value, the mean of surveys made in one year. Station names are not dive-site names. Values above 70% are marked “best patch”: surveys often target the densest coral on a reef, so these may overstate the site as a whole.
| Agency | Site / location | Date | Hard coral cover (%) | Distance | Link |
|---|---|---|---|---|---|
| Reef Check | Island Reef, Anse La Raie | 1999 | 46% | 3.06 km | — |
| Surveyor not identified (2016 Indian Ocean bleaching survey) | ALR/ALBC (Mauritius) | 2016 | 89% best patch | 3.59 km | — |
| WCS via MERMAID (MERMAID bleaching-protocol quadrats) | ALR/ALLC | 2016 | 98% best patch | 3.64 km | Briand J, Darling E. 2016. 2016 bleaching surveys. MERMAID |
| WCS via MERMAID (MERMAID bleaching-protocol quadrats) | Bain Boeuf | 2016 | 71% best patch | 4.86 km | Briand J, Darling E. 2016. 2016 bleaching surveys. MERMAID |
| WCS Kenya / University of Mauritius via MERMAID (MERMAID bleaching-protocol quadrats) | Coin de Mire | 2019 | 10% | 0.27 km | Darling E, McClanahan T, Muthiga N. 2019. Mauritius 2019-2020. MERMAID |
| WCS Kenya / University of Mauritius via MERMAID (MERMAID bleaching-protocol quadrats) | Anse le Raie | 2019 | 50% | 3.64 km | Darling E, McClanahan T, Muthiga N. 2019. Mauritius 2019-2020. MERMAID |
| WCS Kenya / University of Mauritius via MERMAID (MERMAID bleaching-protocol quadrats) | Anse le Raie - Backreef | 2019 | 38% (2 surveys) | 4.19 km | Darling E, McClanahan T, Muthiga N. 2019. Mauritius 2019-2020. MERMAID |
Data & links
- CoralNet image repository for this region ↗
- Photo portfolio ↗
- Coral Reef Diagnostics page for this area ↗
All images from Coral Reef Diagnostics. Data are from Coral Reef Diagnostics and the organizations named in the data sources above.
© Coral Reef Diagnostics.