When Do Bluefin Tuna Show Up in Northern California?

Short version: Northern California bluefin are a late summer and fall story in most recent years, and they ride in on warmer, cleaner offshore water. There's no fixed date. The way to know they're in range is to watch the water and the reports, not the calendar.

A newer fishery, and an unpredictable one

For a long time, bluefin were a Southern California and Baja fish, and NorCal boats mostly ran for salmon, rockfish and albacore. In recent years, bluefin have shown up more often off San Francisco, Half Moon Bay and Monterey Bay, and a lot of local crews now plan around a bluefin window.

It isn't the same every year. Some seasons the fish come within easy range for a while; other seasons they barely show or stay far offshore. Treat everything below as a pattern, not a promise.

When they usually show

In most recent years, the best NorCal bluefin fishing has come from late summer into fall, roughly August through October, sometimes running later when the warm water holds. That lines up with the time of year upwelling winds ease off and warmer offshore water can push in toward the coast.

The fish can arrive earlier or later depending on the year, so watch the water through the summer instead of waiting for a date.

The water they come in on

Bluefin tolerate a wide range of temperatures, but off Northern California the fish are usually found in the warmer, cleaner water offshore of the cold upwelled band, commonly around the low to mid 60s Fahrenheit. They're often on or near a break where that warmer blue water meets cooler green water full of bait.

What to look for on the chart:

• Warm water pushing toward the shelf edge. When northwest winds relax, the cold green water along the coast weakens and warmer offshore water can slide in. See West Coast upwelling explained.
• A tight break. Two or three degrees over a short distance is more interesting than a broad, even stretch of warm water. See how to read a temperature break.
• Color. Clean blue water next to green water with bait. See chlorophyll charts explained.
• Bait and birds. Temperature narrows the search. Bait, birds and marks on the sounder confirm it.

How to watch for them

1. Check the chart every few days through the summer. Open Bay Area / Monterey and Northern California and watch where the warm water sits relative to the shelf edge. 2. Watch it move. Step back through recent days. Warm water that's been creeping inshore for a week is a better bet than a one day blip. 3. Check the buoys. Our free Bay Area water temps page shows Half Moon Bay, Monterey and the other NOAA buoys. A warming trend there backs up what the satellite shows. 4. Follow the reports. Landings, forums and charter reports tell you when fish are actually being caught. Line those up with the chart to see what water they were in. 5. Measure the run. Bluefin water can be a long way out. Use the route tool for distance and bearing, and plan fuel with a real reserve and a weather window.

The honest bottom line

NorCal bluefin usually show in late summer and fall, on warmer clean water pushing toward the shelf edge, but every year is different. Watch the water, watch the reports, check the regulations, and go when the edge sets up within your range.

Not for navigation.