It is recommended to usesexually mature snails, weighing at least 100-125 g, as initial breeding stock.Farming should preferably start at the onset of the wet season, because that isthe time snails normally start to breed.
Until snail farms becomeself-sustaining, farmers may have to collect snails from the wild or buy themcheaply in the peak season and fatten them in captivity in the off season. Inrelatively undisturbed forest areas, snails can be collected on days followingrains.
Snails are active at night andon cloudy or foggy mornings. During the day they tend to keep well hidden, soit is best to collect them at night or early in the morning, when the sun islow and the humidity high.
Farmers purchasing breedingstock from snail gatherers or from the market should expect a fairly high levelof mortality as a result of poor handling and the adjustment to differentfoods.
The most reliable way ofobtaining parental stock is from known breeders, or from agriculturalinstitutes. Such parent snails might be more expensive than snails from othersources, but they are better and safer because they have been properly fed andmanaged from hatching, and have not been damaged during collection andsubsequent handling.
Once the snail farm is established, farmers should select breeding stock from their own snails. Breeding stock must be selected in the wet season preceding aestivation, based on the following attributes:
- Fecundity (expected number of eggs, based onnumbers laid in previous seasons)
- Hatchability (percentage of eggs likely tohatch out of the total
- Establishment rate (percentage of snails likelyto survive after hatching)
- Growth rate
- Shell strength
Simple records kept by snailfarmers can provide the necessary information. As a general rule, the fastestgrowers with the strongest shells should be selected as breeding stock. Thestronger its shell, the better the snail is protected against predators.
Snails selected as breedingstock are placed in hutch boxes or trench pens, which must contain feed andwater troughs.
Some farmers let snails layeggs in the grower pens, and then transfer the eggs to the nursery boxes orpens, but this is not recommended. It may be difficult to locate the eggs, andthe eggs may be physically damaged during the transfer.
A breeding snail may lay oneto three egg masses (clutches) per season. The number of breeding snails placedin a hutch box depends on the fertility of the group and on the number of youngsnails required.
The latter depends on the penspace available. After egg laying, the parent snails should be returned totheir grower pens.
In A. achatina, large differences have been observed in egg production within and between populations. The average size of egg mass produced by the various ecotypes studied in Ghana, for example, ranged from 38 to 563 eggs. Generally, snails lay between 100 and 400 eggs.
The eggs are broadly oval andmeasure about 5 mm long. They are usually laid in round-shaped holes dug 2-5 cmdeep in the soil (figure 20). Occasionally they are laid on the soil surface orat the base of plants. Snail eggs require a certain amount of warmth.
In A. achatina for instance,the baby snails have light-brown shells with black stripes. They should be keptin the boxes and fed on vegetable or fruit leaves (like cocoyam and paw pawleaves), fruits (preferably paw paw), powdered oyster shells and water untilthey are big enough to move to grower pens. Young snails do best if they arekept with snails of the same size.
The eggs of Achatina fulicaare small (4 mm) and are laid in clutches of 10 to 400; usually a parent snaillays several clutches in a year.
Hatchlings remain 5-15 daysunderground before emerging.
The eggs of Archachatinamarginata are quite large (17 × 12 mm) and egg clutches are small (4-18 eggs).A parent snail may produce several clutches a year. The incubation period isaround 4 weeks. Hatchlings remain underground for 2-5 days after hatching.