Aquaculture, 27 (1982) 121-127 121 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

THE DIETARY VALUE FOR SEA-BASS LARVAE (DICENTRARCHUS LABRAX’) OF THE ROTIFER BRACHIONUS PLICATILIS FED WITH OR WITHOUT A LABORATORY-CULTURED ALGA

FRANCOIS-JOEL GATESOUPE* and JEAN H. ROBIN**

*Znstitut National de la Recherche Agronomique, Centre de Recherches Hydrobiologiques, Labomtoire de Nutrition des Poissons, Saint-Pee-sur-Niuelle, 64310 Ascain (France)

**Centre National pour I’Exploitation des Ow.?ans, Departement de Biologie, Aquaculture et P&hes, Centre Oceanologique de Bretagne, B.P. 337, 29273 Brest Cedex (Fmnce)

(Accepted 26 May 1981)

ABSTRACT

Gatesoupe, F.J. and Robin, J.H., 1982. The dietary value for sea-bass larvae (Dicentrarchus lubrax) of the rotifer Brachionusplicatilis fed with or without a laboratory-cultured alga. Aquaculture, 27: 121-127.

Rotifers were fed on a laboratory-cultured alga, Platymonas (= Tetraselmis) suecica, and/or a diet composed of commercial single-cell proteins. They were given to sea-bass larvae up to day 15-20 after hatching, while Artemia nauplii were supplied from day 9-13. At day 21., the survival rate of fish obtained with rotifers fed on compound diet ranged be- tween 32 and 82%, and their mean weight between 5.0 and 7.8 mg. When rotifers were fed either only on algae or on a mixture of 33% algae and 67% compound diet, the growth and survival rates of sea-bass were not clearly different to those obtained with rotifers fed on compound diet. No significant difference was observed when these rotifers were enriched with nutrients just before distributing them to fish. However, these rates appeared to be quite high in comparison to those obtained by several other authors. We can therefore re- commend rotifers fed on compound diet as being, even without enrichment, convenient and low-cost food for sea-bass larvae.

INTRODIJCTION

In a previous study (Gatesoupe and Luquet, 1981), the rotifer Bmchionus plicatilis fed on 75% compound diet and 25% algae (Platymonas (= Tetraselmis) suecica) was found suitable for rearing sea-bass (Dicentrarchus la&war) larvae. These rotifers could also be enriched with nutrients before leading them to fish larvae, to offset any possible decrease in their dietary value. Rotifer mass culture was then achieved by using a compound diet as the only food (Gate- soupe and Robin, 1981). It remained to be seen whether such compound diet- fed rotifers were suitable for fish larvae, in comparison with rotifers totally or partly fed on algae, while estimating the expediency of an enrichment before distribution.

0044-8486/82/000~0000/$02.75 o 1982 Elsevier Scientific Publishing Company

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MATERIAL AND METHODS

General rearing conditions

The technique was described by Girin (1979). Two rearing units were used: one was an open system composed of 250 1 cylindrical tanks with hemispheric bottoms; the temperature was maintained at 20 + 1°C. The other one was a recirculating system composed of 150 1 cone-bottomed cylindrical tanks, the temperature of which was kept at 19 + 1°C.

Food and enrichment of rotifers

Rotifers were produced according to the technique described previously (Gatesoupe and Robin, 1981). The composition of their diet is reported in Table I. This compound diet was given either as the only food or in a mixture of 67% diet and 33% algae. Other rotifers were fed only on algae.

The technique for enrichment has already been described (Gatesoupe and Luquet, 1981). The mixture of nutrients used here was slightly different (Table I). Furthermore, the rotifers were not filtered and they were distributed within their enriching medium. Taking into account the shortness of the gut passage time of rotifers (Starkweather and Gilbert, 1977), their distribution was ex- tended for about 6 h: after 0.5 h of enrichment, the rotifers were put with their medium into 10 1 containers; they were then drawn by a drop by drop water supply through the overflow into larval rearing tanks. Enrichment medium is very polluting and the water of these tanks, turbid for several hours everyday, was not recirculated. Enrichment mix was used in the proportion of 1.5 g/lo6 rotifers, added to 0.5 g red Carophyll@’ /lo6 rotifers (canthaxanthin at 10% from Hoffman-La Roche).

TABLE I

Composition of mixed diets (in g/100 g dry weight)

Diet for rotifers Enrichment mix

Spray-dried spirulina IFP yeast Corn starch Cod liver oil D-glucosamine hydrochloride Choline chloride Vitamin premix* Ca HPO, Fe SO, - 7H,O

40 40

9.9 4 0.5 2 3 0.5 0.1

Fish autolysate “Peptonal” 73 Cod liver oil 10 Vitamin premix (*) 10 Choline chloride 4 DL-methionine 2 Ca HPO, 0.8 Fe SO, * 7H,O 0.2

100

*Gatesoupe and Luquet (1981).

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Experimental design

Seven experiments comprised of two to four lots were carried out with sea- bass larvae. The only common factor in all the experiments was the treatment with algae,-fed rotifers. We would have preferred one experiment consisting of several replicates for each treatment and using the same batch of eggs, but it was not feasible because of the number of larvae or tanks simultaneously avail- able. Table II gives the details of treatments and food sequences. Each lot is figured by the order number of its batch and one or several initials according to its food: A for algae-fed rotifers, D for rotifers fed on compound diet, AD for rotifers fed on 33% algae and 67% compound diet. DE or ADE means that the rotifers were also enriched. Experiment 1 or 2 was composed of treatments A and D, experiment 3 or 4, of treatment A, D, DE and AD. In experiments 5 and 6, there were three treatments, A, DE and ADE. Experiment 7 included only treatments A and DE. These treatments were never replicated within the same experiment. The mean weight of hatching larvae ranged between 0.27 and 0.38 mg, varying with the batch of eggs. The initial density of larvae was between 4:3 and 55 fish/l, according to the experiment. Rotifers were given from day 4 or 5 after hatching, up to a date between day 15 and day 20, i.e. when they were no longer consumed. The date of the initial feeding of Artemiu nauplii was between day 9 and day 13. Twenty fish were sampled at days 0,

TABLE II

Design of ssea-bass experiments

’ Experiment 1 2 3 4 5 6 7

Recirculating system + + + - + + Tank volume (1) 150 150 150 250 150 150 250 Initial fish density/l 43 43 53 52 55 48 44 Initial mean weight (mg) 0.33 0.32 0.32 0.27 0.38 0.30 0.32 Initial mean length (mm) 4.2 4.0 4.0 3.9 3.5 3.0 4.0

Treatment of rotifers* Algae-fed (A) + + + + + + + Diet-fed (D) + + + + - - Diet-fed, then enriched (DE) - - + + + + + 67% diet-fed (AD) - - + + - - - 67% diet-fed, then enriched (ADE) - - - - + + -

Feeding on rotifers Initial day Last day

Feeding on Artemiu Initial day Last day

4 4 4 4 4 5 4 16 17 18 15 18 20 17

10 9 10 10 12 13 9 21 21 21 21 21 21 21

*One lot per treatment in each experiment.

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10 and 15, and 50 fish at day 21, in order to analyse growth. Weight and length data were compared between lots within each date and each experiment by the test of Kruskall and Wallis; when a difference was significant, each lot was com- pared to each other by the simultaneous test procedure of Dwass. These tests were reported by Sokal and Rohlf (1969, pp. 395-397).

RESULTS

If we compare sea-bass mean weight obtained with treatment D to that obtained with treatment A (Table III), we notice that it was significantly lower three times out of four, by day 10, then twice out of four times by day 15, and only once on day 21, whereas it was never significantly higher. Inversely, sea-bass mean weight obtained with treatment DE was never significantly lower than that obtained with treatment A, while it was significantly higher twice out of five times by day 15 and only once on days 10 and 21. The final mean weight ranged between 4.5 and 8.6 mg for treatment A, between 5.0 and 7.8

TABLE III

Mean weight (mg) of sea-bass and statistical significance

Day Experiment A

- 10 1 0.998 2 1.11s 3 0.60b 4 0.65sb 5 0.4ob 6 0.65sb 7 0.95

D DE

0.51b - 0.72b - 0.40c 0.62abc 0.58b 0.7Sa - 0.64a - 0.72a - 0.82

AD ADE x * Probability (Kruskall-Wailis test)

- - 6 x 1O-5 *** - - 3 x 10-a** 0.84s 8 x lo-‘*** 0.61ab - 3 x 1o-1* - 0.48sb 2 x 1o-2* - 0.49b 8 x 1O-3** - - 4 x 10-l

15 1 3.37a 2.81b - - - 3 x 10-s** 2 3.12 2.97 - - - 9 x 10“ 3 2.84a 1.95b

;:;“2:: 2.91a - 6 X 1O-3**

4 1.9ga 1.73ab 1.31u - 2 x 1o-2* 5 1.84 - 1.75 - 1.81 9 x 10-l 6 0.94b - 1.64a - 1.16b 5 x 10-s*** 7 1.99b - 2.808 - - 2 x lo-‘*

21 1 8.57.= 6.24b - - - 5 x lo-‘*** 2 7.68 7.80 - - - 7 x 10-l 3 6.43 5.34 5.87 6.18 - 5 x lo-’ 4 5.0g=b 5.02sb 5.7aa 4.34b - 8 x lo-$*** 5 4.61a - 5.388 - 3.45b 4 x 10-h*** 6 4.48 - 3.93 - 4.68 2 x 10-l 7 7.67 - 7.88 - - 3 x 10-l

a, b and c indicate into what partition the means are broken up within each experiment by the simultaneous test procedure of Dwass.

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mg for treatment D, and between 3.9 and 7.9 mg for treatment DE. Compar- ison between the sea-bass mean lengths of treatments A and D (Table IV) would give a result similar to that of the comparison between their mean weights, whereas there was no clear similarity between the lengths of sea-bass receiving treatments A and DE. Survival (Table V) was generally better with

TABLE IV

Mean length! (mm) of sea-bass and statistical significance

Day Experiment A D DE AD ADE x1 Probability (Kruskall-Wailis test)

10

i5

21

1 6.4s 2 6.5~ 3 5.3b 4 5.7ab 5 5.0 6 5.2ab 7 6.4

1 9.4s 2 8.9 3 9.1a 4 8.1a 5 7.8 6 6.3b 7 8.0b

1 12.4’ 2 12.3 3 12.1s 4 11.1sh 5 10.28 6 10.2 7 12.3

5.3b 5.8b 4.9b

5.6ab -

9.ob 9.3 8.0b 7.1b= -

11.6b 12.2 11.2c 11.oab - - -

- - 5.4b

6.la 5.5 5.6a 6.2

- -

8.7ab 7.3b 7.3 7.6’ 9.0a

-

11.4bc 11.6’ 10.7s 10.0 12.3

- -

63 5.5b - - -

- -

, 9.5a 6.4’ - - -

- -

12.0sh 10.7b -

- 7 x 10-s*** - 2 x 1o-z* - 5 x lo-‘*** - 4 x 1o-1* 5.1 1 x 10-l 5.0b 7 x 10-a** - 4 x 10-l

- 1 x lo-‘* - 9 x 10-l - 3 x lo-3** - 6 X 1O-5*** 7.3 7 x 10-l 6.5b 3 x 10-s*** - 2 x 10-l*

- 5 x 10-s*** - #1 - 2 x lo-‘***. - 8 x 1O-s*** 9.4b 4 x 10-s***

10.3 5 x 10-l - 8 x 10-l

a, b and c indicate into what partition the means are broken up within each experiment by the simultaneous test procedure of Dwass.

TABLE V

Survival of sea-bass (number of 21-day-old fish per 100 hatching larvae)

Experiment A D DE AD ADE

1 65 87 - - - 2 33 46 - - - 3 48 32 71 52 - 4 57 77 79 64 - 5 37 - 35 - 25 6 26 - 43 - 31 7 44 - 56 - -

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treatments D or DE than with treatment A, except in two cases (lots 3D and 5DE). The final percentage of survivors varied from 26 -65% for treatment A, from 32 to 87 for treatment D, and from 35 to 79 for treatment DE. Treat- ments AD and ADE, duplicated only, did not lead to trends clearly different from the others.

DISCUSSION AND CONCLUSIONS

At day 10, the mean weight of sea-bass which were given algae-fed rotifers was generally higher than that obtained with rotifers fed on compound diet, but not higher than that obtained when these compound diet-fed rotifers were also enriched. This difference tended to wear off by days 15 and 21 after hatching, while the amount of ingested Artemia increased. One can see by referring to Table VI that the amount of Artemia supplied from day 9-13 up to day 20 was important with regard of the total supply of rotifers. The effect of possible deficiencies in the dietary value of rotifers thus disappeared during this second step of the food sequence, probably owing to the high dietary value of Artemia. Moreover, if the mean weight of sea-bass obtained with com- pound diet-fed rotifers is compared to that obtained by other authors (Table VII), it appears low at day 10 (0.4-0.7 mg against 0.5-1.1 mg), but higher by day 15 (2 or 3 mg against 1-2 mg) and day 21 (5-8 mg against 3--4 mg).

The growth performances presented here are excellent. Survival rates are likewise good, with a slight superiority when rotifers, either enriched or not, were fed on compound diet. Consequently, we can recommend compound diet- fed rotifers as convenient and cheap food for sea-bass larvae, without requiring any enrichment of their dietary value or a supply of laboratory-cultured algae.

TABLE VI

Amounts of 10’ live food organisms per 21-day-old sea-bass

Prey (X 10”) Experiment A D DE AD ADE

Rotifers 1 2 3 4 5 6 7

Artemia 1 2 3 4 5 6 7

2.4 1.8 - - - 3.3 2.3 - - - 2.5 3.9 1.7 2.3 - 2.2 1.6 1.6 2.0 - 3.1 - 3.0 - 4.1 5.4 - 3.3 - 4.6 3.5 - 3.4 - -

2.9 2.2 - - - 4.2 3.0 - - - 2..9 4.3 2.2 2.6 - 2.2 1.6 1.7 2.0 - 1.5 - 1.7 - 1.4 1.8 - 1.1 - 1.5 2.7 - 2.7 - -

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TABLE VII

Growth and X !rurvival of sea-bass obtained by several authors in comparison with those of the present study

Day 0 Day 10 Day 15 Day 20121 Survival % ~~~ (day ZO/Zl) mg mm mg mm mg mm mg mm

Barnabe (1976 I MeatI _ 5-5-6- 8 38 (15-24°C)

Barshona-Fernandes Minimum 0.3 5 0.7 6 1.3 7 3.4 9 21 and Girin (197’7) (WC) Maximum 0.5 5 1.1 7 2.2 8 4.1 10 62 Girin (1979) Mean 0.4 3 0.5 6 1.5 7 3.0 9 48 (18°C) Maximum 0.5 4 0.6 6 1.8 8 3.6 9 90

Present study Minimum 0.3 3 0.4 5 0.9 6 3.5 9 21 (19-20°C) Mean 0.3 4 0.7 6 2.1 8 5.7 11 49

Maximum 0.4 4 1.1 7 3.4 10 8.6 12 87

ACKNOWLEDGEMENTS

This study was supported by the CNEXO (Contract number 79 6056), and performed at the “Centre Oceanologique de Bretagne”, Brest, France. We thank Dr. D. Ballerini (Institut Francais du P&role, Rueil-Malmaison) for supplying IFP yeast. The figures were prepared by Mrs S. Gros. The Kruskall- Wallis test computing was programmed by Dr G. Conan. The authors would also like to thank Drs. J. Guillaume and P. Luquet for their helpful suggestions during the preparation of the manuscript.

REFERENCES

Barahona-Fernandes, M.H. and Girin, M., 1977. Effect of different food levels on the growth and survival of laboratory-reared Sea-bass larvae (Dicentmrchus labrex (L.)). 3rd Work. Group Maricult. ICES. Brest, France, May 10-13, 1977. Publ. CNEXO, Actes Colloq., 4: 69-84.

Barnabi, G., 1976. Contribution 1 la connaissance de la biologie du Loup, Dicentrarchus labrax (L.) (Poisson Serranidae). These de Doctorat d’Etat. Universite des Sciences et Techniques du Languedoc, Montpellier, 426 p. roneo.

Gatesoupe, F.J. and Luquet, P., 1981. Practical diet for mass culture of the rotifer Brachioms plicatilis: application on larval rearing of Sea-bass, Dicentrarchus labrax. Aquaculture, 22: 149-163.

Gatesoupe, F.J. and Robin, J., 1981. Commercial single-cell proteins either as sole food source or in’formulated diets for intensive and continuous production of rotifers (Brachionus plicatilis). Aquaculture, 25: l-15.

Girin, M., 1979. Methodes de production des juveniles chez trois poissons marins, le Bar, la Sole et le Turbot. Rapports Scientifiques et Techniques, Publ. 39, CNEXO (France), 202 pp.

Sokal, R.R. and Rohlf, F.J., 1969. Biometry. W.H. Freeman and Co., San Francisco, CA, 776 pp.

Starkweath’er, P.L. and Gilbert, J.J., 1977. Radiotracer determination of feeding in Brachiorw calyciflorus: the importance of gut passage times. Arch. Hydrobiol. Beih., Ergebn. Limnol., 8: 261-263.