GROWTH TEST WITH ARTIFICIAL FOOD

FOR A NON ABALONE ARCHAEGASTEROPOD

(Adam & Amos Abalone Foods - Australia)

For an industrial protection reason, the studying mollusk isn’t name in this paper. Even, the authors and the organism of this experiment have to be anonymous. However, this experiment concerns a study of the growth rate of an archaegasteropod, but this mollusk isn’t an abalone. In this test, the food using by the authors is an abalone artificial food, giving by the Australian society ADAM & AMOS ABALONE FOOD.

A / BIOLOGICAL MATERIAL.

Molluscs, used in this experience, was from the same spawn making in an hatchery. This animals was seriously selected for non having the biggest and the smallest ones. At the beginning, the animals had a shell length average of 31.51 mm (± 2.4 mm) et a body weight average of 6.14 grams (± 1.7 g) for 64 animals. The four groups (16 animals each one) was statistically equals. There’s no mortality during the four months of this experiment.

B / ALIMENTATION.

Four diets was tested, three with artificial foods and one with sponges. For each group, Laminaria digitata was addicted. The alimentation planning is:

Table 1.

The group D was the reference one. The diet sponges/Laminaria was the diet using for animals since three years.

The artificial foods came from the Australian company ADAM & AMOS ABALONE FOODS, whose sent us three samples of their production. The food composition is 80% of plant proteins and 20% of fish meal. The experimenters didn’t know the differences between the samples.

For each alimentation, the remaining granules was systemically retired and new ones was gave to the animals. In general, it was stayed some food except for the group A at the Monday feeding, so after three days. Most of the time, the disappearance of the aliment A was quicker than the two others, but it’s difficult to say if it’s an animal consumption or a degradation in the water.

C / THE STRUCTURE.

The structure was a semi-closed circuit system by chutes, with a capacity of 1.2 m³. The animals was put in baskets of 25 x 25 cm. Shelters increased the total surface, estimated at 4400 cm². The four baskets was in the same circulated water line.

D / WATER CHARACTERISTICS.

Sea water, coming from a boring, was removed each Mondays, Wednesdays and Fridays, 100 liters each time, so less than 10%. This small renewal was enough for the biomass present in the structure.

E / MEASUREMENTS AND CALCULATION METHOD.

Animals was measured each month between September, 18^th, 2000 and January, 23^rd, 2001, so five times during this period. Before each measure, animals are dried on absorbent paper during three or four minutes. Two parameters was calculated : the shell length, measured with a caliper (precision 0.1 mm) and the fresh body weight with a scale SCALTEC (precision 0.01 gram).

For doing some comparisons with the works on abalone, a growth rate calculted with the following formula :

W_f and W_i are final and initial body weight ; t is the experience duration.

Click on Graph to enlarge

Daily body weight progresses are visible in the table 2.

At first, the artificial food gives better results on the growth than the original diet with sponges and algae. The aliment A had the impressive results, then aliments B and C had similar results. Differences between aliment A and sponges diet is really important (multiplication by 2.3).

It exists less references about the growth rates of this animal in the nature, so, it isn’t possible to know if the growths observed during this experiment are the wild growth rates. However, with this aliments, the growth rates are better than the one with algae and sponges. It’s necessary to precise that the sponge growth rate calculated during this four months is normal, compare to the growth rates calculated since three years. Animals used for this experiment, had five years old and had a body weight average around 6 grams at the beginning. In January, they had 12 grams with the aliments B and C, and until 15 grams with aliment A.

Between the three different sorts of aliment, the better growth rate is obtaining with the aliment A, B and C give similar and lower results.

Results, an easy stocking and utilization and its non expensive cost give to this products interesting arguments. Even if it’s calibrating for abalones, this archaegasteropod have a good adaptation to this diet. Many others tests must complete this first approach and perform the growth rate of this animal.