DREDGES  FISHING

            Various shapes and sizes of dredges are used to collect edible clams.  Most of the dredges, such as bamboo basket rake and iron wire basket rake, are small, and are operated near shore on a small-scale.  However, some iron-frame dredges for collecting blood-cockles (ark-shells) or short-necked clams (undulated surf-clams) are operated by fishing boats on a comparatively large scale.

            According to the fishery statistics from 1993 to 1997, the annual catch of blood-cockles and short-necked clams showed a tendency of decrease, but in 1996 short-necked clams was sudden jump, it may due to many trawlers changed to be dredges in that year. The annual catch of marine shells is shown in the table below.

Table 10.0 Annual production of some marine shell fish 1993-1997  (mt)   
   

FISHING GEAR AND METHODS

Clam dredge

                     The most common types of dredges are the simplest ones; any implement in the fishing household which can serve to dig a hole in the sand or mud on the beach is also a fishing tool.  A piece of wood, a nail, an iron bar, a bamboo stick, a length of wire or a grass-rake, becomes a dredge on a sand-bar and in the shallow water in the tidal zone.  No boat is required for this method of clam-collecting, and most commonly sought specials are Venus-clam and hard clam.

                     Larger dredges are operated from a boat, to collect clams that live in water up to 5 meters deep, such as blood-cockles (ark-shell).  The dredge in this case is an iron basket (60 x 80 x 40 cm) with a bamboo holder (6-7 m long).  Fishing is done in the day-time, near a river-mouth or anywhere with muddy sea bottom.  It is quite popular in Nakhon Si Thammarat and Pattani provinces.

                     Large-scale dredge-fishing operations are carried out from inboard-powered boats with 6-120 h.p. engine.  A boat usually pulls one or two dredges.  These are shaped like a box, with the sieve size from 10 to 20 mm.  The dimensions are : 40 x 60 x 50 cm for blood-cockle dredge, and 130 x 200 x 20 cm for short-necked clam.  Fishing grounds are in muddy sea bed areas and around the river mouth.  Dredges are operated in the day-time, all the year round, with the peak period from September to November.  Most dredge-fishing boats are registered in Trat, Samut Prakan and Surat Thani province.