You can't study the estuary as one thing. It's three distinct ecological zones, shaped by a single force: salinity.

Suisun Bay in the east is nearly fresh — fed by the Sacramento and San Joaquin rivers. It hosts freshwater species like Threespine Stickleback and Siberian Prawn.

North Bay is the mixing zone — brackish water where freshwater and marine species overlap. The most dynamic habitat, shifting with the tides and seasons.

South Bay is the most saline, connected to the Pacific. Here you find marine species — jellyfish, tunicates, English Sole — alongside estuary residents.

Scientists cover this vast territory through nine sampling networks — circuits that field crews run by research vessel, timed to the tides.

Each circuit is sampled with otter trawls — nets towed behind the boat for 10 minutes, sweeping up fish and invertebrates from the channel bottom. A single quarter produced 244 trawl samples across the Bay.

Shallow stations require spring tides for access. Crews plan around weather, tidal windows, and even submerged hazards — one network lost a propeller to an unmarked rock wall.

The South Bay is home to the largest tidal wetland restoration in the United States — 15,000 acres of former salt ponds being returned to tidal marsh habitat.

The monitoring network is designed to answer a critical question: is restoration working?

By sampling at restored project sites alongside natural reference sites and long-term benchmarks, scientists can directly compare fish communities.

Across the Bay, 17 planned restoration sites mark where the next chapter of recovery will unfold. Baseline monitoring at these locations will begin before construction starts — establishing what's there before transformation.

As data accumulates, each station on this map will grow to reflect what was found there — species abundance, community diversity, seasonal patterns.

The map becomes a living portrait of the estuary's ecological health — showing not just where we look, but what we find.