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Season	Key biological events
March–April	Smelt migrate upstream to spawn around Putney – Battersea; Dace mass-spawn in Wandsworth; First elvers (~65 mm) arrive.
May	Dace larvae (~9 mm) drift downstream; Flounder post-larvae (>8 mm) appear in multiple waves; Smelt fry (~18 mm) present; Bream recruitment begins.
June	Sand smelt spawn in the Greenwich area; Common goby fry (>7–9 mm) appear; First bass fry waves (>12 mm) enter the estuary.
July–August	Continued waves of bass fry; High abundance of juvenile goby, flounder, and bass throughout mid–upper estuary.
September	Thin-lipped grey mullet fry (>15–20 mm) arrive; Juvenile bass, smelt, goby and flounder penetrate upriver to Chiswick–Richmond.
October–Winter	Progressive downstream migration of estuarine and marine species; Freshwater species move downstream as temperatures drop; Adult marine species exit to the North Sea.

Area	Species
Richmond	Bream, Perch, Roach, Bass fry, Flounder, Goby
Brentford	Bream, Perch
Putney – Battersea	Dace, Smelt
Chelsea creek	Roach
Greenwich	Sand smelt
Upper Thames (general)	Goby, Flounder, Smelt fry, Bass fry
Dock basins	Smelt

Area	Species	Why this area matters
Richmond – Brentford	Dace, roach, perch, bream; juvenile goby; bass fry; flounder	Primary nursery zone for freshwater and euryhaline juveniles; shallow margins and low salinity provide refuge and feeding habitat.
Putney – Battersea	Dace, Smelt	Confirmed major spawning corridor: dace (April) and smelt (March–April); crucial upstream migration route.
Greenwich	Sand smelt, smelt fry	Likely spawning area for sand smelt.
West Thurrock & below	Sole, plaice, dab, juvenile bass	Major flatfish nursery and important marine–estuarine interface; high abundance of juvenile marine fishes.
Gravesend & below	Adult smelt; marine juveniles	Primary entry corridor for marine species; starting point of smelt upstream spawning migration.
Dock basins	Smelt; mixed freshwater & estuarine species	Provide refuge habitats with stable temperatures and reduced flow; important overwintering and nursery areas.
Soft marginal vegetation	Roundfish fry: dace, smelt, bass	Essential microhabitat for fry using selective tidal stream transport; supports feeding and shelter; increasingly rare.
Continuous tidal foreshore	Dace fry, smelt larvae, bass fry	Required for uninterrupted fry migrations; heavily reduced (<1% of natural bank remains) due to encroachment and hard engineering.