Alligator Reef, Florida Keys • August 14, 2026
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Analysis by FishIntel, built and calibrated by Captain Kit Carson, licensed charter captain, Islamorada, Florida Keys.
Hot late-summer pattern with the Atlantic ridge in control: east to southeast breeze 8-14 kt through the daylight hours and a quick 2 ft chop on the reef, nothing that keeps you home. Water is summer-warm everywhere, averaging 86.7 F across the zone, but a cool slot of 85.2-85.9 F water sitting SE of the reef line and a hard color front off the Upper Keys give us real edges to fish. Best concentration of bait and favorable water is off Molasses to Carysfort, where the Stream is only 2 nm off the reef. This report covers the water within 50 nautical miles of the point you pinned, so it reads where you fish as well as where you launch.
Zone average is 86.7 F, running 85.2 to 88.1 F. The hottest water is inshore on the bay side, 87.4-88.1 F, and the shallow backcountry stations agree, reading 88.9-89.1 F this morning. The fishable structure is ocean side: a cool slot of 85.2-85.9 F runs from about 24.91N, 80.26W northeast through 25.03N, 80.20W, pinched between 87-plus reef water to the west and 86.2-87.3 F water further offshore. That is roughly a 2 F change over 6-10 nm, and the satellite imagery read flags the same break 6-10 miles SE of the reef running NE-SW. The automated break detector came back empty, but the grid gradient is real and it lines up with the color data. Two degrees does not sound like much in August, but it is enough to stack bait on the cool side of the wall.
Average chlorophyll is 0.626 mg/m3. The clean side reads 0.065 mg/m3 at 25.60N, 79.77W, blue Gulf Stream water offshore to the northeast. The green side peaks at 9.719 mg/m3 at 25.60N, 80.27W, with a wall of elevated cells stepping south through 25.48N, 25.35N and 25.23N along 80.27W, down to 25.10N, 80.40W. Front strength is 9.654, a hard green-to-blue change. That line sits on the ocean side of the Upper Keys reef tract, roughly Molasses to Carysfort and just seaward, exactly where you want it. This is not bay turbidity; the bay is west of the islands and this wall is seaward of the reef. Green holds the bait, blue holds the commuters. The layer is about 67 hours old, so expect the line to have shifted a little with the set.
Mean flow across the zone is 0.94 kt setting NE. The real muscle is along the southern boundary of the grid, a band of 2.5-2.6 kt water moving ENE near 23.5-23.7N, the Florida Current core. Between that core and the reef sits a slack, slightly cyclonic trough: the lowest sea-level anomaly in the zone is at 24.13N, 80.63W, south of Alligator, and the height gradient across the zone is sharp enough to mark a genuine shear edge. Per the Key West office, the shoreward edge of the Stream is 7 NM SE of Alligator Reef Light, 7 NM SE of Molasses Reef Light, and only 2 NM SE of Carysfort Reef Light. Read: the Stream is tucked tight against the Upper Keys and set back a touch off Islamorada. Blue water is a short run, and that 2 nm edge off Carysfort puts Stream-side fishing right next to the reef.
SMOS returned 36 points, average 36.5 PSU. The spread is wide: a 32.4 PSU low far to the south at 23.63N, 81.13W, and a 39.9 PSU maximum at 24.88N, 80.13W, about 25 nm east of Alligator Reef Light. Honest read: 39.9 PSU is not physical for this area, that cell is almost certainly land-contaminated, and SMOS is coarse and gappy this close to the reef. Treat the 7.5 PSU gradient as soft corroboration only. It at least agrees there is a water-mass boundary on the ocean side SE of the reef, in the same neighborhood as the temperature slot.
Net primary productivity averages 548.6 mg C/m2/day across the zone, but the hot line off the Upper Keys reef is running far above that: 4523.8 at 25.60N, 80.27W, then 3365.1, 2971, 2283.8 and 2027.3 stepping down the same 80.27W line to 1671.8 at 25.10N, 80.40W. That is up to eight times the zone average. This is the base of the food chain, plankton to forage to gamefish, and it overlays the chlorophyll wall cell for cell, which is why the bait is there. Same caveat as the color layer: about 67 hours old, so the bloom will have drifted with the set, likely a bit east-northeast by now.
East to southeast breeze 8-14 kt through the daylight hours, lightest mid-morning, freshening after 6 PM and topping out near 15 kt late. Long Key was showing ESE at 10 kt gusting 13 mid-morning, right on script. Seas are a mixed short chop: modelled for the zone, total wave height 1.7 ft building to about 2.2 ft by late evening, period 3.5-3.9 seconds, direction 115-122 degrees. It is mostly wind chop on a small ESE swell of about 1.5-1.8 ft at 3-4 seconds. Short period, so it feels busier than the height reads: a quick, slappy 2-footer, more annoying at anchor than dangerous. Center consoles fine all day; smaller skiffs will notice it on the evening run when the breeze fills.
New moon was about a day and a half ago, we are on a 9% waxing crescent, and tides are building toward springs with a 2.7 ft range today. High 11:06 AM at 2.53 ft, low 5:09 PM at -0.18 ft, high again 11:28 PM. The money window is the falling tide from late morning through 5 PM: it pulls shrimp and bait off the patch reefs across the deep edge, and the afternoon major solunar period 2:06-4:06 PM sits inside it. The morning incoming paired with the moonrise minor 8:02-9:32 AM is the second-best window. Dark crescent nights favor the evening reef bite too.
Peak of their April-August season, and the water suits them: the 86.7 F zone average sits inside their 72-88 F tolerance, on the warm side of the 78-84 F sweet spot. Per the thermal guidance, the play is the coolest water in the zone, the 85.2 F slot, so fish the cool side of the breaks. The Bloom Line stacks the color change, the productivity and a 2 nm Stream edge in one place. No weed-line reports in the log today, but the setup is textbook.
86.7 F is inside their 70-88 F range but well above the 74-80 F sweet spot, and this is the thin part of their year; summer fish hold deeper and bite early. The one thing working for you is the Stream tucked 2 nm off Carysfort, putting a real edge in short reach. First light is the whole ballgame.
The 86.7 F surface average is above the 86 F top of their usual range, and December-April is their season here; late summer is the thin stretch. That is a seasonal statement, not a reason to stay home: the only door open is the coolest water in the zone, the 85.2 F slot, where a stray is possible while you mahi fish the break.
86.7 F is inside the 70-87 F band, warm side of the 73-82 F optimum. Blackfin are past their winter-spring peak but live on these edges year-round, and the productivity line off the Upper Keys gives them a reason to be up and feeding early.
Surface temperature does not drive this fish; they are at 1,200-1,800 ft in 40s-50s F water no matter what the SST chart says. What matters is the ride and the drift. Seas of 1.7-2.2 ft are manageable, and the set runs about 1 kt ENE mid-zone building to 2.5 kt plus along the southern core, so plan the drift line before you drop.
86.7 F reef water is inside the broad 65-90 F tolerance for the snapper-grouper crowd, current on the reef is a manageable NE drift around a knot, and the tide program is good: incoming into the 11:06 AM high, then a 2.7 ft fall through the 5:09 PM low that pushes bait off the patches and across the deep edge. The afternoon major period 2:06-4:06 PM lands right in the middle of that fall.
Rank 1, the Bloom Line off Molasses to Carysfort, centered near 25.19N, 80.24W. Four things stack here: the chlorophyll wall swinging from 9.7 to 0.065 mg/m3 across a few miles, the productivity hot line topping 4500 mg C/m2/day, the eastern wall of the cool temperature slot where SST falls from 87-plus inshore to 85.2-86.0 F, and the Gulf Stream itself only 2 nm SE of Carysfort Light. The model's own fishability peak lands at 25.19N, 80.24W with a score of 68, and the imagery read puts the cleanest water just seaward of this line. Green water holds the bait, blue water is close enough for pelagics to commute across, and the break gives everything a wall to hunt. Confidence is tempered only by the 67-hour age of the color data. Rank 2, the break SE of Alligator, centered near 24.87N, 80.45W. The imagery read is explicit that the thermal break, the color change and the sea-level gradient all stack 6-10 miles SE of Alligator Reef, and the SST grid supports it with the 85.3-85.9 F slot sitting between warm reef water and warmer offshore water. The (admittedly noisy) salinity maximum sits just east of it, hinting at a water-mass boundary in the same place. Numeric chlorophyll support is thin this far south, so this zone leans on the imagery read and the SST grid. It is the backyard play out of Islamorada. Rank 3, the southern shear near 24.05N, 80.65W, where the 2.5-2.6 kt ENE core slides past the low sea-level trough at 24.13N, 80.63W. A real current edge with a weak cyclonic twist, but it is 45-plus nm south, rests on one layer, and matters mainly if you are running long for swords or want to work the Stream core.
Reading these charts from the bridge this morning, the SST shows a warm tongue of 31°C+ water hugging the reef line from Alligator out toward Tennessee Reef, with a noticeable thermal break running NE-SW about 6-10 miles southeast of the reef where temps drop into the 29.5-30°C range. That break is fairly sharp and well-oriented — classic edge to work. Further offshore, the SE corner shows the cooler 28.5-29°C signature of the Gulf Stream's inshore edge, and it looks like it's set back a bit today, not pushing hard against the reef, though there's a subtle meander/bulge in the southeast quadrant worth watching. Chlorophyll shows the expected green nearshore band tight to the Keys with a color front roughly paralleling the reef 3-6 miles out, transitioning to cleaner blue water south and east. The cleanest water sits in the SE corner, matching the Stream position. SLA is coarse but tells a clear story: high anomalies (+0.15 to +0.25 m) dominate the western and northern boxes, with a low-pressure trough of cooler, lower water (-0.05 m) across the southern edge — suggesting a weak cyclonic shear zone south of the reef. The convergence to fish: the thermal break, chlorophyll color change, and SLA gradient all stack up 6-10 miles SE of Alligator. That's your edge today.
Oldest layers in the stack are chlorophyll and productivity at about 67 hours; SST is 29 hours old and the buoys are current.
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