Island summary of 4 dive sites. Figures are averages across the sites that report them (n = sites with a value); each site's own page has its individual values. Part of the Fiji - Northern Lau (Vanua Balavu / Cicia / Nayau) regional summary.
Heat-stress figures: NOAA Coral Reef Watch — Fiji 5-km virtual station. Each pill links its source record and carries the values behind it.
Island summary
Nayau's northwest fore-reef slopes, surveyed in June 2013, held 44-52% coral on large Acropora build-ups, with Drupella snails on several colonies and an old anchor chain colonized by small corals.
Heat stress
sea surface temperature (SST) (left axis)DHW under 2DHW 2–3DHW 3–5DHW 5–8DHW 8–10DHW over 10 (🔥 above 12)
Daily SST (line) and weekly maximum Degree Heating Weeks (bars), Jan 2023–Oct 2026, NOAA Coral Reef Watch 5-km Fiji virtual station. Dashed line: bleaching threshold (maximum monthly mean 28.4°C + 1°C). DHW ≥ 4: bleaching likely; ≥ 8: severe bleaching and mortality likely. A bar is drawn only where DHW exceeds zero, so a stretch with no bar is accumulated heat stress of zero, not missing data — the SST line runs the full period.
4 sites in this region — click a marker to open that site.
Overview
Nayau is a small island in the Lau group of eastern Fiji. Four Global Reef Expedition stations were logged on its northwest side on 16 June 2013: three transect stations (FJNA38, FJNA39, FJNA40) and a 2 m snorkel site about 0.85 km away (FJNA38SN), which has no cover record. Maximum dive depths were 16.2 m at FJNA39 (Living Oceans Foundation (LOF) team log), 21.3 m at FJNA40, and 31.1 m at FJNA38, while the survey notes describe the setting as shallow fore-reef slopes.
Coral cover was high at all three transect stations, from 44% at FJNA40 to 52% at FJNA39, with FJNA38 at 48%. Algae covered 33% (FJNA39) to 39% (FJNA40) of the benthos. The survey team's notes for the northwest side describe large Acropora build-ups with rubble piled at their bases and Tydemania macroalgae creeping up their sides, and large plating Diploastrea prominent at 15 m. FJNA39 is a classic spur-and-groove reef with well-developed coral on the spur tops and grooves scoured and filled with rubble, and the FJNA38 frames show coralline-sheeted framework carrying many small colonies rather than a few large ones. An old anchor chain at FJNA38 has been colonized by small Pocillopora.
The survey notes record coral-eating Drupella snails on several Acropora colonies. At FJNA40 Anderson photographed a bleached pocilloporid and a second one with pale, partly bleached tissue. No crown-of-thorns is recorded for Nayau's own stations, and none carries a station-level Coral Health Index; Anderson's sampling sheet records four of the seven colonies sampled at FJNA38 as 1–10% pale or bleached, and the photographs of a tagged probe colony there (tag 092) show its upper branches partly bleached (photos not shown).
Highlights
Cover from 44% (FJNA40) to 52% on a classic spur-and-groove reef with well-developed coral on the spur tops (FJNA39).
Large Acropora build-ups with rubble piled at their bases and Tydemania macroalgae creeping up their sides, as the survey notes record for all three Nayau stations.photo: Fiji - Nayau (FJNA38)
An old anchor chain lying across the pavement, with small Pocillopora colonies established on link after link (FJNA38).
Drupella snails on several Acropora colonies, as the survey notes record for Nayau's northwest side (station not stated).
Notable observations
Fiji - Nayau (FJNA40): Bleaching: a bushy pocilloporid Anderson recorded as bleached, uniformly cream-white, and a second pocilloporid with pale, partly bleached tissue between still-brown polyps (single colonies, no extent inferred). The survey team's notes for Nayau's northwest side record Drupella snails on several Acropora colonies (station not stated). No crown-of-thorns starfish recorded.
Fiji - Nayau (FJNA38): Debris: an old anchor chain lying across the pavement has been colonized by small Pocillopora.
1 of these 1 values rests on 10–19 photographs (*)
Claude (Anthropic), blind point count
28%*
—
1
1 of these 1 values rests on 10–19 photographs (*)
In-water diver transect (line/point intercept)
44%
—
1
—
The mean is an UNWEIGHTED mean of the dive site values — each dive site counts once, whatever its photo count — which is the convention of the published tables and of every other figure on this page. Each value is the one printed on that dive site's own page; a page that prints no value for a method (fewer than 10 photographs) is left out of that method's mean.
This table pools only the one dive site in this unit that has a method comparison; the table for all 10 dive sites is on the Fiji - Lau page.
Deviation from the reference
Over the dive sites where an independent reference exists, Claude (Anthropic), blind point count has a mean absolute deviation of 16.0 pp from it across 1 dive site. Not in this ranking: CoralSCOP (edited), which measures coral area rather than points. A mean absolute deviation is not an accuracy score: a model with a consistent offset is correctable, while one with the same deviation scattered in both directions is not.
By dive site
Dive site
CoralSCOP (edited)
Claude
Diver transect
FJNA40
31%*
n=15
28%*
n=15
44%
n under each value is the number of photographs that method scored at that dive site. ⚠ marks a cell that is not an independent check. * marks a value resting on only 10–19 photographs, which is less certain.
Reference: LOF Global Reef Expedition in-water transects (mean of all the station's transects, Living Oceans Foundation per-transect benthic data). Denominator: line/point intercept along the transect; not a photo-point denominator. Source: LOF Global Reef Expedition 2013, per-transect benthic data ('GRE data-full benthic'): the mean of all of each station's transects For all 10 dive sites in the comparison: The transect is THE coral-cover value at every site; the Claude photo estimate is a methods comparison only, never averaged with the transect and never a headline. Site-level only: the photos come from the survey dives, not from the transect points. Few usable habitat photos exist for Fiji: only 10 sites have 10 or more, and 9 of them have fewer than 20 (low-n), so these are not confident site estimates. Accuracy, Claude vs transect, 10 sites: mean difference -5.4 pp (95% CI -12.7 to +1.9), mean absolute difference 10.3 pp, r 0.35. Claude reads lower than the transect at most sites and does not track it from site to site. This is a methods comparison, not a ranking.
photo: Fiji - Nayau (FJNA38)
© Coral Reef Diagnostics.