How Long Does It Take For Scallops To Grow

Scallop seed are initially raised in suspended cultivation, in pearl and lantern nets suspended from long-lines. Pearl nets are generally used for small (10-30 mm shell height) scallops and lantern nets for larger animals. At first the pearl nets can be stocked at 50-80 scallops per net, reducing to 20-30 as they grow. From 30-60 scallops can be put into each compartment of a lantern net initially (at 30-40 mm) but this should be reduced to no more than 10-15 per compartment at 60-80 mm.

Some companies have developed plastic mesh cages that can be stocked with bivalve molluscs, including scallops, and suspended in stacks from long-lines. However, it is very costly to use these suspended cultivation methods to raise scallops to market size. This is mainly due to the cost of the large number of nets or cages needed, to avoid crowding, which can lead to mortality, and maintenance and labour charges over a long grow-out period, usually about 4 years.

Growth rates of scallops in suspended cultivation, provided that they have plenty of space to themselves, are similar to those for animals on the seabed. However, studies have shown that wave action, and thus movement in the nets, can be a stress factor as the scallops grow.

How Long Does It Take For Scallops To Grow

There can also be problems with fouling of the nets and bio-fouling of the shells with suspended cultivation methods. Shell bio-fouling is a major drawback of the ear-hanging cultivation technique, and can result in mortality. Nevertheless, cultivators on sites where there is little or no barnacle fouling may find the ear-hanging method worthwhile.

The above considerations have generally led farmers in the UK to cultivate scallops on the seabed, once they have reached a size (usually about 50-60 mm) at which they are less susceptible to predators such as crabs and starfish. Obviously this can only be done at sites where the substrate is suitable.

However, at sites where growth rates are good the seed will reach the size at which they may be planted out on the bottom by the end of their first year. Some studies have shown that scallops kept in suspended cultures have thinner, more easily broken shells which could make them more liable to be predated by crabs when put onto the bottom, compared with wild scallops. These differences become more apparent with increasing size of animals. This emphasises the need to plant out the seed onto the bottom as soon as practical.

Transferring scallops to the seabed also helps to keep the shell clean from fouling organisms, due to the abrasive action of the sediment. Scallops seeded onto the seabed will disperse naturally. Early experiments in a Scottish sea loch showed that most scallops remain within 30 metres of the point of their release, finding a density of less than one scallop per square metre. Some French and Norwegian studies have been based on reseeding at 1-2 scallops per square metre, although at sheltered sites with suitable substrate it may be possible to on-grow scallops at much higher densities than this.

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