International Journal of Marine Science 2016, Vol.6, No.25, 1-8
2
seaweed growing areas include Gulf of Mannar, Gulf of Kutch, Palk Bay, Lakshadweep and Andaman and
Nicobar islands.
Lobophora variegata
is a species of small thalloid brown alga which grows intertidally or
in shallow water in
tropical and warm temperate seas. There is interest in the use of seaweeds in the development of low-cost, highly
nutritive diets for human and animal nutrition, especially animal nutrition since sea vegetables are able to
accelerate the growth of oysters, tilapia, salmon, trout, etc., all of great commercial interest (Fleming
et al
., 1996).
At present seaweeds with elevated protein content and production rates are receiving increasing attention as novel
feeds with potential nutritional benefits (Buschmann
et al
., 2001) and as possible ingredient in fish diets (Wahbeh,
1997).
Lates calcarifer
(Bloch), commonly known as Giant Seaperch or Asian seabass is an economically important food
fish in the tropical and subtropical regions in the Asia–Pacific. It is a euryhaline, carnivorous and originating in
seawater (Harpaz
et al
., 2005). Because of its relatively high market value it has become an attractive commodity
of both large and small-scale aquaculture enterprises. Fish meals which are extensively used in feed for fish and
other animals may lead to the continuous exploitation of these natural resources which in turn will become
environmentally and economically unsustainable. To date, very little attention has been paid to the nutritional
value of algae as a potential substitute of protein and other ingredients in fish feed (Sorensen and Denstadli, 2008).
This experiment was undertaken with an aim to evaluate the brown seaweed
Lobophora variegata
as dietary
ingredient in partial replacement of fish protein on growth performance, body composition and survival of Asian
seabass
Lates calcarifer
juveniles.
2 Materials and Methods
2.1 Fish and experimental conditions
A total of 200 seabass
Lates calcarifer
juveniles were procured from Rajiv Gandhi Centre for Aquaculture
(RGCA), Sirkazhi, Nagapattinam district, Tamil Nadu, with proper aeration and then transferred to the laboratory
for further study. The juveniles were stocked in ground water and the water samples were collected from culture
tanks prior to the feeding experiment and analyzed for different parameters (pH, 7.5; temperature, 25°C, dissolved
oxygen, 3.5 mg/L)
according to APHA (2005).
2.2 Experimental diets
The dried seaweed (
Lobophora variegata
) powder was procured from Centre for Advanced Study in Botany,
University of Madras, Chennai, India. The feed ingredients such as soya bean, coconut oil cake, ground nut oil
cake, tapioca flour, dry fish meal, green gram and egg were purchased from merchants; vitamin mix and cod liver
oil were obtained from medical shops at Trichy. Along with these, the dried seaweed
Lobophora variegata
powder
was added in feed mix in known ratio and diets were formulated as shown in Table 1. Feed ingredients were
mixed well and brought into colloidal form. These feed mix paste were made into a pellet using a manual
pelletizer. Finally these pellets were dried in hot air oven at 27
°
C for 48 hrs.
2.3 Water stability test
Feed pellets (5 gm) were placed in fibre-reinforced plastic (FRP) tank filled with 30L filtered freshwater and
aerated for 1, 2 and 4 hrs. After each respective hour, pellets were taken out from tanks and dried. The dried feed
pellets were weighed and water stability of the feed was estimated using the following formula.
% water stability =100×(Final dry weight)/ Initial dry weight
2.4 Maintenance of fishes
During acclimatization, fishes were fed with boiled egg albumin and control feed without seaweed. Water was
routinely changed every-day in order to maintain a healthy environment for the fish apart from providing artificial
aeration. This ensured sufficient oxygen supply for the fish and an environment devoid of accumulated metabolic
wastes.
