The name of Thau :
 
Historians don’t agree on the origin of the word, never the less one option comes from the Celtic “Taur” meaning mountain. Actually Tauri Stagnum appears in writings, and could designate “the pond by the mountain”.
A Latin origin could be Taurus Palus evoking the similarity between the unleashed lagoon in bad weather and a raging bull.
The lagoon became Tau in the Middle Ages and is now written “Thau”.
 
 
 
 Dates and figures:
 
The Thau lagoon is about 20 km long with a surface off 7.200 hectares. The average depth is 4.5m but the central navigation channel can be 10 meters.
Near Bouzigues a 30 meters deep gap produces hot spring water feeding the Balaruc spa and emerging with a flow of 300litres/sec which represents 9 500.000m3 per year, (to be compared with 48 000.000m3 of water supplied from direct rain and an estimated 30 000.000m3 from rivers).
 
The sea and the lagoon were in pre-historic time 2m under current level (sign that the climate at the time was colder than now).
 
During the Gallo-Roman period (100 B.C. till 200 A.D.) fishing and trade of fish and oysters, and from around year 50 – hydrotherapy - made Thau an important economic and social center.
 
An attempt to raise oysters in Sète’s channels took place from about 1875, but the polluted water of the city and the risks of typhoid put an end to the experiment in 1907. The parks were moved to Bouzigues the following year with the success we still know today.
Around 600 oyster farmers and their 2.700 tables produce an annual 13.000 tons of oysters which is 8.5% of the French production.
An oyster-table is a platform made of metal or wood measuring 50 meters on 12 meters resting on about thirty railroad-rails fixed to the bottom of the lagoon, exceeding one meter fifty above surface.
 
A part from oysters the lagoon produces:
Mussels
Sea-breams (July to October)
Mullets
Sea-perch (in winter)
Eels (from October to February)
 
The lagoon also hosts the most important Sea-Horse colony in Europe.
http://fr.euronews.com/2011/11/30/biologie-marine-des-hippocampes-reintroduits-dans-l-etang-de-thau/