Gag Grouper sea surface temperature guide.
Gag grouper move with seasonal SST shifts — deeper offshore in summer heat, closer to shore in winter when surface temperatures drop. The fall transition window when nearshore SST drops below 72°F is the most productive of the year.
SST threshold gauge
The water temperature ranges that determine where gag grouper hold and feed. Hard thresholds (dashed lines) are values outside which fish actively depart or become inactive.
Depth profile & SST reliability
Gag move offshore to deeper, cooler water as inshore SST warms in summer; return to nearer-shore structure in fall and winter when surface temperatures drop.
Current systems & structure
Winter offshore spawning aggregations form in 100–300 feet when SST drops below 70°F. Best targeted on hard live bottom and rocky structure.
Zone-by-zone calendar
For each zone where gag grouper are present, the chart overlays the zone's typical monthly SST range with the species' preferred and optimal ranges. Months where the bands overlap are when fish are in range.
Gulf of Mexico
| Month | Zone SST | Status |
|---|---|---|
| Jan | 60–68°F | Peak |
| Feb | 60–66°F | Peak |
| Mar | 62–70°F | Peak |
| Apr | 70–76°F | Peak |
| Maynow | 74–80°F | Outside |
| Jun | 80–84°F | Outside |
| Jul | 82–86°F | Outside |
| Aug | 82–86°F | Outside |
| Sep | 80–84°F | Outside |
| Oct | 74–80°F | Outside |
| Nov | 68–76°F | Peak |
| Dec | 62–70°F | Peak |
| Month | Zone SST | Status |
|---|---|---|
| Jan | 60–68°F | Peak |
| Feb | 60–66°F | Peak |
| Mar | 64–72°F | Peak |
| Apr | 70–78°F | Peak |
| Maynow | 74–80°F | Outside |
| Jun | 80–84°F | Outside |
| Jul | 82–86°F | Outside |
| Aug | 82–86°F | Outside |
| Sep | 80–84°F | Outside |
| Oct | 72–78°F | Fishable |
| Nov | 66–74°F | Peak |
| Dec | 62–70°F | Peak |
Conservation & regulations
Overfished (Gulf) — recovery progressing. Tight regulation with closed seasons during spawning periods. Federal Gulf and South Atlantic rules differ. Verify current closure and bag limits.
Stock assessment source →Find the temperature transition line between inshore and offshore — gag stage there in fall and spring. Live pinfish, big jigs, and frozen sardines on hard bottom in 100–300 feet.
Sources
SST threshold data is summarized from agency and research sources. Year-to-year ocean conditions vary; verify current SST imagery before each trip.
See live SST for your offshore zone.
Bield: Fish overlays NOAA CoastWatch SST imagery on your chartplotter view, highlights the temperature breaks that match gag grouper thresholds, and alerts you when your home zone hits the 64–72°F window.