During the 1960s, in the early years of spat collection, the mesh bags were simply discarded onion bags.

The spat collector types include bunches of seaweed (Laminaria) suspended from ropes, simple stretch nets anchored to the bottom, and mesh bags stuffed with monofilament nylon gill netting. The Japanese use a number of different spat collectors for the collection of spat of the Japanese scallop Patinopecten yessoensis (Ito 1991). Similarly in the Philippines, the fibrous husks or coir of coconuts are strung on polypropylene ropes to serve as spat collectors for the green mussel Perna viridis (IIRR 1995). In China, spat collectors consisting of palm fibers attached to ropes are suspended from offshore rafts or longlines to catch settling blue mussel (Mytilus edulis) larvae (Zhang 1984). For the collection of mussels, spat collectors usually consist of a fibrous plant material attached to ropes.

The spat collectors are suspended in the water from a bamboo framework (Figure 44) or floating raft (PHRDC 1991). Of oyster shells strung onto polypropylene ropes, rubber strips cut from used automobile and truck tires, or discarded fiberglass and plastic box strapping material (Figure 43). Spat collectors for tropical mangrove oysters can be made from a variety of inexpensive materials, including rubber strips cut from truck or automobile tires (A), waste plastic box strapping material (B), or oyster shells strung onto polypropylene ropes (C). In the Philippines, spat collectors for mangrove oysters, Crassostrea iredalei, consist Although the traditional tiles have been superseded recently by the use of commercially produced cone-shaped flexible polyethylene spat collectors, the lime, sand, and concrete coating is still used as a settling substrate for oysters. For example, a traditional spat collector for European oysters, Ostrea edulis, in England has been the coating of curved ceramic roofing tiles with a mixture of cement, lime, and sand and then placing them on the estuary bottom (Walne 1979). Spat collectors for various species of bivalves are generally designed from available materials that the shellfish will settle on. Most artisanal aquaculture of bivalves relies on either collecting settling spat on some sort of artificial spat collector that mimics the natural preferred settlement substrate or collecting the bivalves from natural seed grounds and moving them to a protected farm site. Many species of scallops prefer sea grasses as an initial settlement substrate (Marshall 1947), and various species of clams settle and survive in sediments of various consistencies and grain sizes (Pratt 1953). Mussels will settle on hard surfaces, but they appear to aggregately settle in areas with other mussels, possibly on the fibrous byssal threads of other mussels (Bayne 1976). For example, reef-building oysters in temperate zones generally settle on oyster shells and rocks, but the mangrove oysters of the tropics primarily settle on mangrove wood, but they also settle on rocks and other hard objects (Angell 1986). In nature, settling and metamorphosing juvenile bivalves alight on preferred substrates. Drawings by V Encena embryos, and trochophore larvae that last for about 24 hours until they develop into feeding straight-hinge larvae, fully developed veliger larvae, and eventually pediveliger larvae that seek out a preferred substrate for settlement and metamorphosis into juveniles (Figure 42). Pediveligers are also planktonic, but they devlop bottom-seeking behavior and are capable of setting on preferred substrates. The embryonic and larval stages through the umbonate veliger are planktonic and are dispersed by wind and tidal currents. Identification of the various developmental stages of most commercially important bivalve mollusks from egg and sperm through the larval stages can aid in spatfall prediction. The developmental sequence of bivalves includes the nonfeeding fertilized eggs, All aquacultured marine bivalves spawn seasonally, releasing both eggs and sperm into the water, or alternatively the partially developed larvae into the water where they are dispersed by wind and tidal currents (Loosanoff & Davis 1963). Most small-scale aquaculture of bivalves requires the collection of seed or small juveniles, known as spat, as they settle from their planktonic larval stages.

Oyster spat collector