BAR TODAY || Official Quarterly Publication of the Bureau of Agricultural Research

Abalone: Hungry and ready to get large
by Ma. Lizbeth J. Baroña

January-March 2004
Volume 6 No. 1

If there is one good thing starving does to a living organism, it is the growth spurt once it is given the normal food intake following a moment of starvation. Sometimes, this spurt causes an organism to exceed the normal weight and size it could have gained given normal food intake in a given time.

Numerous studies have been made on compensatory growth in cultured fishes, but there is little or no information on the growth compensation of gastropod mollusks, particularly the abalone.

The question of whether the abalone, (Haliotis asinina) exhibits such tendency, and if it can actually exceed its supposed normal growth after experiencing compensatory growth, is the subject of the study conducted by the Southeast Asian Fisheries Development Center(SEAFDEC) in Tigbauan, Iloilo.

What is "compensatory growth"?
The ability of an animal to show rapid growth when returned to a normal food ration after starvation is called compensatory growth. The growth spurt is caused by increase in food intake, and improved food conversion efficiency.

Compensatory growth is not only affected by starving the animal. This phenomenon is also affected by the food's dietary composition, the animal's reproductive state, or the favorability of the environment. It is also affected by the size and age of the animal in question.

In the case of the abalone, it feeds on algae. Studies have shown that abalones feed on at least two species of microalgae, and that the abalone grows slower when fed with single species diet, than when fed with different algal species. Since abalone depends only on drifting algae carried by currents as food, it is assumed that the mollusk has, at some point, experienced sporadic starvation. The ability of the abalone to control its appetite and growth as a response to changes in the availability of food has never been documented.

Can the abalone bounce back?
Thirty abalones were stocked in each of 12 plastic baskets with holes. These baskets were suspended in a 6-ton capacity cement tank, which was continuously supplied with seawater.

Before conducting the experiment, the animals were conditioned by feeding them fresh seaweeds for 10 days. Three feeding schemes were used with three replicates each. The first scheme, is continuous feeding throughout the 200-day trial period (control group), the second was 5-day starvation and 5-day re-feeding, and the third scheme was a 10-day starvation followed by 10-day re-feeding. The second and third schemes were done over 140 days. After this cycle, the animals were fed continuously for the remaining 60 days of the trial period.

During the trial period, the starved abalones consumed 160 to 170 grams of food, as compared to those that are fed continuously, which consumed 307 grams. But after the starved abalones were fed ad libitum for 60 days, the starved grouped showed significant increase in daily intake, amounting to 8.5 to 9.7 g per day. This increase in intake, was greater than the daily intake of the control group, which was at 3.8g per day. The total seaweed consumed by the starved abalones ranged from 533g to 610g each. This was higher than the amount consumed by the control group, which was at 239g per abalone. It was observed, though, that the abalones on the control group showed a decreasing growth rate from the 140th day up to the 200th. The abalones in the second and third treatments' total weight gain was 392g to 465g, which has no significant difference from the control.

The results showed that abalones did exhibit compensatory growth. And the fact that abalones depend mainly on drifting macroalgae by water currents, the animal experiences slow growth, but are able to catch up with their growth when fed again continuously.

As to the question with what extent of starving induces compensatory growth, the scientists believed that the five-day starving period in the second feeding scheme, has been sufficient to cause the abalone to catch-up on growth when fed regularly.

The results also showed that a complete or partial recovery from food deprivation also depends on the age of the animal. A previous study showed that larger animals have greater ability to store energy than smaller ones, thus having higher resistance to starvation.

This study offered implications especially on open sea cage culture, or sea ranching of abalone where feeding is far apart. The animals can compensate for the weight not achieved during food deprivation once they are fed sufficiently.

Source: Effects of alternate starvation and re-feeding cycles on food consumption and compensatory growth of abalone, Haliotis asinine (Linnaeus), Armando C. Fermin, South East Asian Development Center Aquaculture Department (SEAFDEC/AQD), Tigabauan, Iloilo, Philippines.