5. RESEARCH ACTIVITIES

5.1 HATCHERY TO GROW-OUT PHASES

A schematic of fish development of Denise and sea bass is given in Table 2. Experimental design pertaining to availability of animals at particular growth stages for dietary response is based on this schematic.

Table 2

SCHEDULE OF GROWTH OF SPARUS AURATUS AND DICENTRARCHUS LABRAX

This schematic chart of fish development is presented to illustrate major areas of dietary work and evaluation

Notes on Table 2

Sparus auratus:

1. Spawning is over a three-month period, or a total of five months interval from initial spawning to post-hatchery, giving a possible two (or three) hatchery periods (of two months duration) and any combination thereof;

2. Availability of wild fry from Bardawil lagoon along the northern Sinai peninsula will permit an additional supply of animals for the pending post-hatchery period. Data should be obtained on growth comparison/survival with hatchery-raised animals. Increase in survival rate is essential;

3. Size characteristics. Within three months after hatching, animals of 2.5 gramme size are obtainable. By June–July 1976, approximately 5 gramme size fish may be realized. Between this time and August, animals should be between 5 and 10 grammes and of stockable size. Animals should reach 250 gramme size by 10–14 months (or less) and sexual maturity within 20–24 months. A 250 gramme animal is considered a marketable specimen.

Dicentrarchus labrax

1. Approximately three shipments (approx. 20 000 eggs each) are anticipated from the laboratory of Dr. M. Girin in Brest, France. Spawners at Elat are young (two years old) and may not spawn in 1976. If local spawning does occur, it will not be until March (at the earliest) 1976;

2. Several thousand fry will be maintained on an established diet (either Girin's formulation or a local trout chow) and will be stocked in ponds and reservoirs by July–August with the reserve kept for breeding stock. In 1977, bass fry population will be increased to 10–30 000 animals. The 1976 period will be one of adaptation of fry to the Elat facility.

3. Preliminary data, based on size/temperature/related growth of gilthead bream and sea bass suggest different dietary requirements. Furthermore, temperature differences must be anticipated in development of sea bass at Elat and Brest, since animals at Elat are 30–34 grammes in size, while comparable ones at Brest are approximately 20 grammes. It is noted that at Brest, dried (freeze-dried) artemia is provided at 30 days after hatching until adaptation of the fish to an artemia-fortified pelleted food followed by a complete diet in pellet form. The animal may develop to 1 gramme size by 45 days on natural food.

5.2 EXPERIMENTAL DESIGN

Experiments have been outlined for three general periods of growth of Sparus auratus, i.e., hatchery, post-hatchery and grow-out phases. These test comprise diet development and evaluation, leading to development of semi-synthetic formulations and ultimately, a programme of nutritional evaluation

Hatchery Phase:

The sequence of natural foods provided in the 1974–75 season followed a pattern of unicellular alga (Tetraselmis suecica), rotifers (Brachionus plicatilis), harpacticoid copepods, and brine shrimp (Artemia salina). By day 50, larval Denise are able to utilise artificial food (ca 500 mu); by day 60, hatchery period is terminated.

The proposed 1976 hatchery period will involve the following experimental aspects:

1. Repeat of 1975 live or natural food test;

2. Introduction of artificial food to be tested on a basis of:
   1. total replacement, one or two different formulations; and

   2. supplementation, initial and at selected stages in animal growth.

Evaluations will be made at days 0 to 14 of microcapsules (a) containing single cell yeast protein, (b) containing a complete vitamin supplement as a nutrient microparticle vehicle in the less than 100 ma diameter size range. Testing of the capsulated dietary preparations in the Denise hatchery phase comprises an initial effort to use such materials as a replacement for lire food in the less than 100 mu size range. Furthermore, capsules may serve as a supplemental or a complete diet for the various components of the natural system, i.e., rotifers, copepods and artemia. Proposed experimental design should permit analysis of these aspects.

The period from days 14–60 (or earlier) will involve tests of flake/alginate-based particles of variously designed nutritional formulations. Diets will attempt to simulate an artemia-like composition with known artemia flakes as a control. Follow-up tests are planned for the subsequent spawn with overall objectives or analytical criteria as follows:

1. Survival rate as a function of diet;

2. Weight/length gain;

3. Time/growth acceleration;

4. Overall reduction of hatchery time, to permit initial stocking of post-hatchery animals prior to 60 days.

Poet-hatchery Phase:

The time of this phase is from approximately day 60 (or earlier) to day 100–120, in essence, a 40 to 60 day period. Animals will originate from the hatchery mass rearing tank or will be obtained as wild fry. The prime objective is to achieve high survival rate and good acceptability of a properly designed diet. Experimental options are planned as well as others, such as comparison of reared or wild stock on selected high protein (ca 50–60%) diets. Pre-experimental tests will include those of the binder/stability, hard vs. soft particular material, feed presentation form (i.e., large pellets, “cakes”, etc), and keeping quality (shelf life) of the extruded material.

Experimental treatments, based on modification of the grow-out diet tested in 1975, will include use of selected high quality protein concentrates, selected levels of protein/lipids, attractant inclusion and evaluation of feeding stimulus and/or growth factors.

Since this is a critical phase of the life cycle of the animal, and must be optimized to achieve a predictable supply of healthy fry for subsequent stocking, major emphasis will be on percent survival, and growth increment, along with efforts to decrease the overall time interval from post-hatchery to stocking.

Grow-out Phase

Tests in this phase will endeavor to compare 1975 experimental data with that based on modification of the earlier A-2 diet (40% protein with a 20% vitamin premix potency). Modifications will include use of fish oil, changes in vitamin composition/ concentration, reduction in soya flake with appropriate protein replacement (with evaluation of fish solubles as a growth stimulant) and combinations thereof.

A major aspect of the evaluation will be on fine particle composition of the diet as a reflection of stability and digestibility.