Presented by
A. El-Turky
MBRC/LIBFISH Aqua Component Group
1. OBJECTIVES
Work involving Trachinotus sp. has been undertaken by the Aqua component team with the following objectives in view:
Explore the occurrence of wild fry along the coast;
Explore the possible use of local species for further practical use in aquaculture; and
Facilitate training of MBRC staff in aquaculture techniques such as fry handling, keeping, and feeding.
2. ACTIVITIES
2.1 Capture and Stocking
On the first week of October the LIBFISH/MBRC Aqua Group started collecting Trachinotus sp. fry along the MBRC beach, using a 10 meter-long / 10 mm mesh seine net. About 200 animals were collected and transported to the MBRC aquarium service room inside plastic bags where they have been stocked into two 1 m3 fiberglass tanks for a two-week acclimatisation period. Seawater is replaced once every day and there is constant aeration.
2.2 Initial Mortality
It is usual when wild fish are caught and stocked in tanks for at least a few of them die due to stress, injuries, and/or feeding problems. In the present instance only about ten fish died during the first week of captivity, mainly because of presence of parasites (Crustacea Isopodae) and consequent wounds inside their mouths.
Parasites are quite common and the fishes have been preventively treated with potassium permanganate (20 mg/liter sea water during one hour). The treatment was not effective for adult Isopodida and it appeared that longer treatment with a higher concentration of the chemical is harmful for the fry.
2.3 Feeding
Four specimens of Trachinotus sp. were preserved with formaline immediately after capture in order to study their stomach content and get information on their natural diet. It was evident that most of the ingested food was composed of small crustacea with a few small snails.
During the acclimatisation period, fry were fed on live Artemia sp. and Daphnia sp. as well as with minced fish. After three weeks, they received pellets twice a day (starter for sea-bream). The quantity of pellets given to the fish is calculated according to the manufacturer's table and water temperature
2.4 Grading
After a one month period of acclimatisation the animals were graded into four size classes. Each class was stocked into a separate 1 m3 fiberglass tank with open sea water circuit and permanent aeration. Further monitoring of the performance of the respective classes is now underway-
3. PRELIMINARY OBSERVATIONS
Trachinotus fry kept in captivity seem to have a rapid growth rate. In another two months, the trial work should yield some indications of whether this species may hold possibilities for aquaculture purposes.
Whatever the eventual outcome, the activity is already serving to provide an opportunity for members of the Aqua group to familiarise themselves with fry keeping techniques.
