Fish Finder — Astu Neon · Cape Ann to Cape Cod

Live, interactive maps. Pick a layer and area, zoom & pan to re-render at finer detail, type exact color ranges, and click any map to magnify. The Fronts (live) layer pulls the real SST or chlorophyll grid into your browser and computes the breaks / color fronts on the fly.

1 · Interactive satellite viewer

Main view — Sea surface temperature

Compute on

Fronts sensitivity 5 Show breaks only (hide field)

SST — selected area

Break finder. Tight lines = fast temperature change; gold where they hit a bank edge.

Chlorophyll — selected area

Bait & water mass. Blue = clean, green = productive. Fish the color front over structure.

The two panels above show the same area you set in the viewer. Zoom/pan and ranges update everything together. The Fronts (live) layer is computed in your browser from NOAA's MUR SST or VIIRS chlorophyll grid — real edge detection, not a picture. Click any map to magnify.

2 · The grounds

Annotated chart of Cape Ann to Cape Cod bluefin grounds

#	Zone	Why & how to fish it
1	Stellwagen SW Corner 42.12°N, 70.20°W	The classic Massachusetts Bay giant spot. Sand lance stack on the southwest corner where the bank shoals; work the down-current edge on a moving tide and watch for a 0.5–1°C surface break pinned to the contour.
2	Stellwagen NW Corner / Edge 42.58°N, 70.27°W	Northwest corner and the western edge dropping into Stellwagen Basin. Tuna patrol the temperature/color change between greener bank water and the cleaner basin water; troll or jig the edge, not the flat top.
3	Race Point Rip 42.05°N, 70.23°W	Tide-driven rips off the tip of Cape Cod concentrate bait at the surface convergence. A short run; best on a hard tide with a visible rip line, weed, or bird pile.
4	Jeffreys Ledge 42.92°N, 70.30°W	Northern bank holding herring and mackerel. Look for the warm-edge of any slope/shelf water nudging onto the ledge from the east, and for chlorophyll fronts along the ledge's long NE–SW axis.
5	Tillies Bank / Scantum Edge 42.55°N, 69.97°W	Offshore structure between Tillies Bank and the deep Scantum Basin. The bank-to-basin drop is a reliable bait edge; prioritize it when a clean-water tongue and a temperature break overlap on the eastern side of the box.

3 · How to read the maps

Sea surface temperature (SST)

Look for breaks — lines where color changes quickly over a short distance. In this region a break of even half a degree can stack sand lance and herring, and giants patrol the warmer side of that edge. Tight, well-defined breaks that sit on or against a bank contour are worth more than broad, fuzzy gradients.

Chlorophyll / ocean color

This is the water-clarity and bait-productivity layer. Blue (low chlorophyll) is clean offshore water; green/yellow (high chlorophyll) is productive, plankton-rich water that feeds the bait chain. The edge between clean and green water — a color front — is where bait concentrates. The best giant zones are where a color front and a temperature break line up over structure.

Bathymetry / structure

The banks and ledges (Stellwagen, Jeffreys, Tillies, Wildcat Knoll, Fishing Ledge) and the deep basins (Stellwagen Basin, Scantum Basin) are fixed. Bait relates to the shallow structure; current accelerates over and around it, creating the rips and convergences tuna hunt. Always read the SST and color layers in the context of where the bottom rises and falls.

Putting it together

Highest-confidence call = bank or ledge edge + a tight SST break + a chlorophyll color front, all stacked in roughly the same place, with bait and bird life to confirm on arrival. When the three don't align, fish the structure and the cleanest nearby edge, and let surface signs (rips, weed lines, bird piles, whales pushing bait) make the final decision.

4 · Season & timing

Giant bluefin are typically in Massachusetts Bay and over the offshore banks from roughly June into November, with the strongest action late summer into fall as sand lance, herring, mackerel and menhaden build. Early in the run, surface water is cooler and breaks are subtle; by late summer the bay warms and the meaningful edges are often between bank water and any cooler, plankton-rich upwelled water along the structure. Match the SST color range to the season using the controls on the dashboard so a 1°C break doesn't disappear into a washed-out scale.

5 · Data sources

Layer	Product	Link
Sea surface temperature	NASA JPL MUR SST v4.1 (jplMURSST41) — Multi-sensor blended L4 analysis, 0.01° (~1 km), daily.	NOAA source ↗
Ocean color / chlorophyll	NOAA S-NPP VIIRS chlorophyll, weekly composite (noaacwNPPVIIRSchlaWeekly) — Level-3 mapped, ~4 km. Weekly compositing fills cloud gaps that leave single days mostly empty.	NOAA source ↗

6 · Method & honest caveats

This analysis is built from the same categories of satellite data professional services use for this region — blended multi-sensor sea surface temperature and VIIRS ocean-color chlorophyll, read against bathymetry. The maps on the dashboard are rendered live by NOAA CoastWatch ERDDAP each time the page is opened, so they always show the most recent satellite pass available (cloud cover permitting). Two honest caveats: (1) satellite products carry a latency — MUR SST typically runs a few days behind and the VIIRS science-quality chlorophyll runs about two weeks behind real time; check the date printed on each NOAA image. (2) The break and front calls here are read visually from the imagery and from how this region fishes, not computed cell-by-cell from the raw grid, and the chart is a schematic for orientation, not navigation. Treat it as a planning tool to narrow the search, then let conditions on the water make the final decision.