Oman - Cat Island (Muscat)

Setting

Cat Island is a small islet reef off Muscat, where rock outcrops and boulders rise from a bottom of coarse, shelly sand.

General benthic features

The published counts split the bottom almost evenly between hard coral, soft coral, and turf, and the photographs show each of those three habitats in turn. Hard coral was most abundant on the boulder tops and slopes, which were covered in fields of compact, corymbose branching colonies packed shoulder to shoulder under clouds of small fish (e.g., Image 5, Image 20).

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Seen close up, these colonies had short, knobby branches and grew into one another with little bare rock between them (e.g., Image 6).

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On the steeper boulder faces, the same branching colonies covered the rock almost completely, grading into leather corals lower down (e.g., Image 19).

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Soft coral formed its own stands: ruffled, lobed leather corals (some brown, some pale gray) carpeted a whole stretch of slope beside a large boulder (e.g., Image 17).

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Elsewhere, pale gray leather corals grew right alongside the branching field on the same boulders (e.g., Image 18).

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Large massive colonies stood among them, including one with crowded, flower-like corallites flanked by ruffled leather corals (e.g., Image 8).

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A broad, gray-blue plating colony with raised, bumpy corallites lay beside a dark, tightly meandering massive colony, with a bulb-tentacled anemone at its base (e.g., Image 16).

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In another patch, a rust-colored branching colony, a mauve, lumpy plate standing on edge, and a dark meandroid massive colony shared the rock with two long-spined urchins (e.g., Image 9).

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Rock faces and overhangs carried a patchy crust of encrusting organisms, with tan, lobed leather corals at their base (e.g., Image 7).

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Lower down, the rock was thoroughly bored, turfed, and plated in coralline algae; a dark, spiny crown-of-thorns seastar sat partly hidden in a crevice behind a big pale gray-brown leather coral with its polyps out, a smooth tan massive colony sat at the top of the frame, and small tentacled polyp clusters were scattered over the sand veneer (e.g., Image 1).

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The softest, lowest-relief ground was coarse shelly sand and low rubble mounds furred in dark red macroalgae and turf, edged with carpets of tentacled polyps, with a well-camouflaged scorpionfish lying flat in the middle of the sand (e.g., Image 10).

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Corallimorphs formed dense carpets, their striped oral discs packed edge to edge, which is the cover class the point counts flag here (e.g., Image 13).

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Coral cover

• Reference: Mayfield (2025)
• CoralNet submission package
• Published hard coral cover is 25%, from CoralNet point annotation of 81 photographs (Mayfield 2025, Platax, Table 1; 30 points per photo, water and fish excluded).
• The same counts scored soft coral at 22% and turf algae at 25%.
• The published figure carries the provenance of the paper it appears in and is not subject to the CoralSCOP/DINOv3 caveats applied elsewhere on this map.

Stressors

Very little bleaching was observed during these May 2024 surveys (about 0.02% of coral tissue area; Mayfield 2025), which came before the seasonal SST peak; NOAA CRW recorded Alert Level 2 heat stress and bleaching was reported along this coast from July 2024, weeks after the surveys. No bleached tissue, disease, or fresh mortality was seen in any of the frames shown here. A crown-of-thorns seastar was photographed on this dive: a large, orange-spined individual on a coralline-crusted boulder (e.g., Image 21, Image 22, Image 23) and a seastar partly hidden behind a pale leather coral (e.g., Image 1), possibly the same animal.

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No fresh white feeding scars are visible beside it in these frames. Typical recent thermal stress here is a mean annual maximum of 11.0°C-weeks (Degree Heating Weeks, 2021-2025, NOAA CRW; Gulf of Oman virtual station).

Fish and other fauna

The macro life is the draw: a pair of white, orange-spotted dorid nudibranchs with dark mantle margins and open gill plumes crawled over coralline rock (e.g., Image 2).

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The same pair was photographed again crossing a dense carpet of corallimorph polyps (e.g., Image 3).

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A large disc-shaped anemone sat wedged between two boulders (e.g., Image 15).

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A small school of striped fish worked along a rock face (e.g., Image 11).

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Planktivorous damselfish hung in loose clouds above the branching field, an anemonefish patrolled the leather-coral slope, and barred sergeant-type damselfish crossed the boulders. A stingray lay buried in the sand; Anderson photographed it on this dive (e.g., Image 31).

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Comparisons with other data

We found no other surveys confirmed at this site as of 2026. Within 5 km, four Sultan Qaboos University stations recorded station-year means of 4.2–53% hard coral cover in 2025; the nearest, Sultan Qaboos University at CAYC (Deep), 0.45 km away, read 12% in 2025.

Dive record

The site was dived on 21 May 2024.