a) Extensive lagoon farming

In Europe, this is the most ancient technique, exploiting the migratory behaviour of some species which pass their juvenile stages in coastal lagoons where they grow to sexual maturity and then leave for the sea to reproduce. After some years, (depending on the species and local ecology) the mature fish migrate and are harvested at the confluent of the lagoon with the open sea by fixed capture devices.  Fishing with mobile gear is also a common practice in many lagoons.  Production levels are subject to the natural trophic levels of the lagoons.

This technique, once largely employed in southern Europe, typically concerns eel, seabass, seabrearn and mullet. Additional, less frequently utilised species are sole, turbot, sandsmelt and crabs. It is gradually diminishing in importance due to poor yields which render this practice less and less economically viable.

(b) Extensive carp and catfish farming

Both carp and catfish are easy-to-farm warm water species which are usually raised in earth ponds. Production is achieved essentially from the natural and renewable resources of the pond.  Water quality and flow requirements of these species are modest; juvenile production is usually carried out in the same ponds, where the adult spawning process occurs naturally. The rearing technique is based on the optimisation of the pond's trophic chain in order to achieve the maximum fish yield.

This type of carp farming dates back to the Middle Ages in Europe.

(c) Extensive mussel farming

The rearing of mussels is always done in extensive conditions.  The young mussels are collected from the sea and can be cultured  using a number of different techniques:

1. ‘Bouchot' culture - which uses a series of wooden poles as  supports, onto which the mussels are transplanted for on-growing
2. Suspended rope culture - where ropes, covered with mussel seeds kept in place by nylon nets, are suspended either from rafts, wooden frames or from Iong lines of floating plastic buoys.
3. Bottom culture - which depends on the harvesting of young  mussels and spreading them out on specially prepared protected  growing plots.

A substantial portion of the EC production is grown on suspended  ropes, a technique which can be extended further offshore and which,  although quite sensitive to plankton blooms,  is the only one which could further increase production,  since both the ‘bouchot' and the bottom culture techniques are faced  with growing coastal pollution, bird predation and land use  constraints.

(d) Extensive oyster farming

Although practised by the ancient Romans, oyster culture was rediscovered in France during the 17th century and modern techniques were developed in the 19th century. Oyster larvae are free-swimming and become young oysters by settling beyond the low tide mark or in the intertidal zone. Small wild oysters are collected on solid supports from which they can be removed easily 6-8 months later. During their second  year oysters are spread in the intertidal range

1. either directly on the ground (bottom culture ),
2. or in bags on trestles,
3. or suspended from long-line floats (in the Mediterranean).

Normally, harvesting takes place during the third year.

In France, a special treatment known as 'affinage' may be applied  for the supply of top quality oysters: prior to selling these are  placed in former salt marshes which have been converted into ponds  (called 'claires' )

(e) Extensive clam farming

The farming of the Manila clam starts with a hatchery phase, followed by a nursery phase in tanks, small ponds or special 'boxes'. Juveniles are released into controlled marine areas (lagoons, salt pans, large ponds or ‘parks' in the open sea), often using protection to reduce predation and escape.

Manila clam culture has also lead to additional activity, in that the natural reproduction of animals released for farming has created wild populations in areas that were previously non-producing; these are currently exploited using traditional fishing methods. This is an example of 'culture-based fisheries'. This situation led to some concern over competition with the European species and the risk of diseases being spread. To date, however, there is no clear evidence that Manila clam plays a role in the observed reduction of the European clam yield. This reduction is probably due to fisheries over-exploitation.