Weaning of the sole (Solea solea) before metamorphosis

AquacukUe, 26 (1981/1982) 359-368 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

359

WEANING OF THE SOLE (SOLEA SOLEA) BEFORE METAMORPHOSIS

FRANCOIS-JOEL

GATESOUPE and PIERRE LUQUET

Institut National de la Recherche Agronomique - INRA, Centre de Recherches Hydrobiologiques, Laboratoire de Nutrition des Poissons, Saint-Phe-sur-Nivelle 64310 Ascain (France) (Accepted

16 April 1981)

ABSTRACT Gatesoupe, F. J. and Luquet, P., 1982. Weaning of the sole (Solea solea) before metamorphosis. Aquaculture, 26: 359-368. Sole larvae were given live Artemia nauplii only during their first few days of life. They were then fed on artificial diet, semi-moist and crumbly in form, Good results were obtained without supply of frozen nauplii (15 and 28% survivors from hatching up to day 70, respectively for two lots abruptly weaned from day 10 or 11, with 50 and 90 mg as the final mean weight, and a supply of 1980 or 2660 live nauplii per 70-day-old fish). Gradual weaning was also tried, supplying frozen nauplii for the first 5 days of inert feeding. The best weaning was found to be the latter one, i.e. with frozen nauplii being given from day 11 to day 15. This produced 49% survivors from hatching up to day 50. A total of 2800 live nauplii were required per sole at this stage. But the growth rate, 27 mg as the mean weight by day 50, was unsatisfactory. In addition, the pigmentation of sole from the three tested batches of eggs was observed. The proportion of normally pigmented sole at the end of the experiments was between 13 and 70%. The differences between lots from the same spawning were found to be significant. This would indicate that unchecked rearing conditions might produce the very high level of pigmentary anomalies generally observed in the rearing of flatfish.

INTRODUCTION

The weaning of sole has been achieved during the first months after hatching by several researchers (Metailler and Girin, 1976; Bromley, 1977; Fuchs, 1979). When sole are fed on live prey, their daily food requirement increases quickly. In Fuchs’ experiments (1979) 2400 nauplii of Artemia salina were needed per larva from hatching up to day 15 (i.e. 3400 nauplii per metamorphosed sole, on the basis of 70% survival); from day 16 up to day 25, the date of the earliest weaning by this author, 15000 nauplii were needed per sole, i.e. five times the amount needed for the first fortnight. Girin (1979a) estimated the dry weight cost of Artemia nauplii at 220 US dollars/kg. Earlier weaning would be valuable in view of this high cost. Thus we tried to feed sole larvae on a prepared diet from their first days, with either sudden or gradual weaning. In the latter

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360

case, frozen nauplii were given simultaneously with the prepared diet, during the weaning period. MATERIALANDMETHODS

General rearing conditions The technique has been described by Girin (1979b). Two units with conebottomed cylindrical 60 1 tanks were kept at two different temperatures (19 and 17 + 1°C) for larval rearing, until metamorphosis. Sole were transferred into square 50 1 tanks, 15-20 days after hatching. The temperature of this unthermostated unit ranged from 15 to 20°C. When inert food was given, the cylindrical tanks were cleaned every 3 days, whereas the square tanks were cleaned daily. Food and feeding Artemia nauplii were the live prey provided. Frozen nauplii have been used in some experiments to facilitate transition to a prepared diet. In these experiments, frozen nauplii were distributed twice a day simultaneously with artificial food, according to the experimental design described by Girin (1979b, pp. 28-29), but only for the 4 or 5 days of weaning. The daily amount was 10 g/ tank (i.e. about 0.6 X lo6 frozen nauplii) irrespective of the number of larvae. The artificial food was semi-moist and crumbly in form (about 33% moisture), suitable for the weaning of sole according to Bromley’s experiments (1977). Crumbs were prepared weekly: the unpulverized foodstuffs (cod-meal and freeze-dried Artemia) were ground finely and mixed with the other dry powders. Cod liver oil was added. Separately, fresh egg-yolk was mixed with methionine and choline. Red Carophyll (a, Hoffmann-La Roche) (10% hydrosoluble canthaxantin), melted in hot water, was added after cooling. This liquid mixture was poured into the powder. It was then kneaded until an homogenous paste was obtained. Afterwards it was ground into crumbs and screened through 630 pm. The fraction retained on the sieve was ground again. The crumbs were stored at 4°C and used for one week. The distribution was automatic and continuous. The components of this diet (see Table I) were chosen in order to be stable in water and full of nutritional quality. Stability in water was obtained by the binding properties of casein, yolk, gluten and algin. Nutrients were as concentrated as possible, in order to palliate the risk of underfeeding. The fat level was about 20% on a dry weight basis, according to Kudoh (1977) who recommended fatty diets for fish larvae. Polyunsaturated long chain fatty acids were provided in cod liver oil. With such a fat level, the proteins amounted only to 48%. If Artemia salina were taken as a reference, as Van der Wind (1979), the protein level of the diet might seem low (58% protein in Artemiu, analyzed by Gallagher and Brown (1975)) but the amino-acid composition

of the diet

100

33.1 11 9.9 11 2.2 6.6 5 17.8 0.6 2.2 0.6

._

(1971);

***Gallagher

48

Crude protein (g/100 g dry weight) from Anonymous

8.1 5.7 7.7 4.3 1.3 6.8 3.8 5.1 5.1 6.0 2.8 5.5 4.5 8.1 19.4 4.3 8.3 5.1

and Brown (1975).

58

8.0 5.3 7.6 4.6 1.0 5.4 2.7 4.9 4.7 4.5 1.8 6.5 6.9 9.2 14.2 5.3 5.2 4.8

____ diet* * Artemia* ** _~_~~___ _.

~_.___. ~~ g/100 g protein

Leucine Isoleucine Lysine Threonine Tryptophan Valine Methionine Methionine + cystine Phenylalanine Tyrosine Histidine Arginine Aianine Aspartic acid Glutamic acid Glycine Proline Serine

Amino-acids

**Computed

___

g/l00 g dry weight

*Gatesoupe and Luquet (1981);

Total

w_--__I Casein Wheat gluten Artemia (freeze-dried) Cod meal Sodium alginate Premix* Cod liver oil Fresh egg-yolk DL-Methionine Choline chloride Canthaxantin (10%)

Feedstuffs

Composition

TABLE I

362

was quite similar (Table I). Vitamins were largely present in the diet as well as canthaxantin, the main carotenoid of Artemia salina (Czygan, 1968). Nine per cent of freeze-dried Artemia were added also as an attractant, although there was no evidence of its usefulness (Girin, 197913). Morphological criteria On day 10 and day 20, samples of 20 fish were taken from each lot, and their morphological stages were described, according to Fuchs’ classification (1978). Samples were then taken every 10 days, but only for weighing. At the end of the experiment, a larger sample was taken (200 fish or the whole lot if survivors numbered less than 200), and the dorsal pigmentation was observed. Several classes of abnormal pigmentation were described in flatfish (e.g. De Veen, 1969). Albinism, either total or partial, was the only anomaly easily observed on 50-70 days old sole. Thus we compared the number of normally pigmented fish and their mean weight with those of the albinos. Indeed, in the artificial propagation of plaice, Shelbourne (1964) found between 40 and 80% of abnormally pigmented fish. This proportion correlated with fish size and rearing conditions, while Riley (1966) found a correlation with the feeding level. Experimental design Experiment 1 Three lots of 2500 larvae (0.46 mg and 3.0 mm) were reared at 17 f 1°C. Live nauplii were given up to day 6,9 or 10, to lots A, B and C respectively. They were then fed on crumbs. The experiment ended on day 70. Experiment 2 Three lots of 8000 hatching larvae (0.50 mg and 3.3 mm) were reared at 19 + 1°C. Such a population density (130 larvae/We) was tested in the hope of reducing the overdistribution, unavoidable with inert foods. Lot D was fed on live nauplii up to day 7; after this, frozen nauplii were given simultaneously with crumbs up to day 11. Lots E and F were fed on live nauplii up to day 9 or 11 respectively; after this, crumbs were the only food provided. The experiment ended on day 60. Experiment 3 Five lots of 3500 larvae were studied. Their weight at hatching was particularly low: 0.29 mg for 3.3 mm, i.e. a condition factor of 0.81 (compared with 1.70 and 1.39 for the other experiments). Two lots were reared in the 17°C unit: lot G was fed on crumbs from the beginning, with a supply of frozen nauplii for the first four days; lot I was fed on live nauplii up to day 7, followed by frozen nauplii with crumbs up to day 12. Three other lots were reared in the 19°C unit; lot H was fed on live nauplii for 4 days; lot J replicated the food

363

procedure for lot I; lot K was fed on live nauplii up to day 10 and frozen nauplii up to day 15. The experiment ended on day 50. The differences in growth rates were tested by the Kruskall-Wallis analysis of variance. The condition factors were computed, according to Girin (1979b), as being the ratio between weight and cube length, expressed as percentage. RESULTS AND DISCUSSION

Lots A, G and H were eliminated at day 20. Indeed, their results were quite poor: metamorphosis still uncompleted (Table II), mean weight between 3.0 and 3.6 mg (Table III) and survival rate between 6 and 21% (Tables IV and V). Sole seemed thus hardly weanable before day 8. Considering that later weaning provided better results without any marked trend among the treatments, it did not seem to matter whether the nauplii given between day 8 and day 10 or 13 were live or frozen. However, lots B and C, though reared in the same conditions, presented very different results, both in growth and survival rates (51 mg and 15% survivors by day 70 for lot B, versus 89 mg and 28% for lot C). Some improvements should be needed in order to ensure more stable results. In particular, the temperature of the unit for metamorphosed sole should be kept at 20°C. However, the best survival rate was obtained by lot K with the latest weaning, i.e. from day 11, with 5 days of feeding on frozen nauplii (68% of survivors by day 20,49% by day 50). But the mean weight of this lot was only 27 mg by day 50. Such a growth rate should be improved; for TABLE II Development stages* at day 10 and day 20 __..__~ ._ _-..--_.~---~-____~2

3

C

DEF

GHIJK _~

1 19 20

1 1 18 20

1 6 13 20

8 12 20

10 8 3 21

17 4 21

20 20

4 16 20

11 10 21

5 13 2 20

-

-

-

-

-

-

-

4 1 11 5 19 20 20 __.__*According to Fuchs (1978).

21 21

3 2 16 21

2 17 19

1 2 17 20

1 4 7 5 3 20

2 7 7 4 20

2 4 9 5 20

1 2 17 20

2 2 16 20

Experiment

1

Lot

A

B

10th day Number of larvae At the stage 0, At the stage 0, At the stage OP Total

2 18 20

20th day Number of soles At the stage 0, At the stage 0,

-

At the stage OP At the stage P, At the stage P, Total

-__

0.46 1.86 4.57 11.0 19.0 28.7 42.9 51.4

0 10 20 30 40 50 60 70

0.46 2.79 3.27 -

B

mean weight

III

DayA

1

Growth:

TABLE

0.46 2.97 6.39 17.8 24.7 65.8 91.5 89.3

C

<0.001***
(P)

x2 probability

(mg) and x2 probability

0.50 2.96 4.38 13.9 24.1 28.5 25.6

D

2

0.50 3.01 5.39 11.8 17.4 18.6 29.2

E


(P)

x2 probability

and Wallis test

0.50 1.46 4.90 15.1 18.7 34.4 30.6

F

of the Kruskall

0.29 0.97 3.63 -

___-

G

3

0.29 0.74 3.04 -

N

0.29 1.64 4.37 9.6 16.1 20.8

I

-

0.29 1.29 4.85 10.6 17.8 21.5

J

0.29 1.66 4.49 14.0 20.7 26.9

K

--I_


(0

x’ probability

365 TABLE

IV

Food and survival up to the day of transfer first experiments

from larval tanks and up to the end of the two

2

Experiment

1

Lots

A

________

Larval

rearing

nauplii

Day of transfer Number of survivors Per 100 hatching larvae Total nauplii per sole Live nauplii per sole Day of end of experiment Number of survivors Per 100 hatching larvae Per 100 transferred sole Biomass estimate (g) Total nauplii per survivor Live nauplii per survivor

TABLE

C

D

E

__ -. F

temperature

(“C) Day of weaning Number of days with frozen

B

17 10

17 7

17 11

19 8

19 10

19 12

15 1920 24

15 1163 15

1493 1493

1746 521

1376 1376

19 1160 15 1552 1552

70 706 28 75 63.0 1984 1984

60 895 11 47 22.9 3746 1118

60 184 2 16 5.4 8697 8697

60 184 2 16 5.6 9784 9784

4

20 521 21

16 1120 45

345 345

893 893

20

70 376 15 34 19.3 2660 2660

16 938 38

V

Food and survival up to the day of transfer third experiment Lots Larval rearing temperature (“C) Day of weaning Number of days with frozen nauplii Day of transfer Number of survivors Per 100 hatching larvae Total nauplii per sole Live nauplii per sole Day of end of experiment Number of survivors Per 100 hatching larvae Per 100 transferred sole Biomass estimate (g) Total nauplii per survivor Live nauplii per survivor

from larval tanks,

G

H 17

and up to the end of the

I

J

K

4

19 4 4

17 8 5

19 8 5

19 11 5

20 720 21 3268 -

20 202 6 11846 198

19 743 21 4768 808

19 1913 56 1956 458

19 2385 68 1988 755

20

20

50 1013 29 52 21.8 3694 865

50 1698 49 71 45.7 2792 1060

50 170 5 23 3.5 20839 3531

mean weight (mg) Normally pigmented fish Albinos Mann-Whitney test (standard normal deviate) -__-_ 54.5 44.1 2.253* ---

92.2 84.9 1.232

__

E

_-..__

25.8 25.4 0.181

31.4 27.0 1.779

47 49 <0.001***

70 =0.04*

% normally pigmented fish x2-test probability (P) 60

D

B

Lot

C

2

Pigmentation at the end of the experiments ~_ ~..., ._~~~ 1 Experiment

TABLE VI

31.8 30.4 0.289

13

F

24.5 20.1 1.146

15 <0.001***

I

3

17.8 26.6 5.976***

57

J

-

i___-

24.1 33.2 4.140***

69

K

_____.~_._.._

367

instance with more attractive food; Bromley (1977) and Fuchs (1979) recommended the addition of mollusc flesh, which would be especially easy with semi-moist diet. The number of live nauplii required per metamorphosed sole were low: between 345 and 1552. So the amount of frozen nauplii used for gradual weaning must be taken into account. For instance, in experiment 3, about 1732 to 17308 frozen nauplii were required per 70day-old fish, i.e. between 62 and 83% of the total amount of the nauplii. Thus, sudden weaning would seem more advisable. Besides, the very high level of fish density used in experiment 2 was unprofitable, since it yielded no more fish than with lower density levels (1200 to 1900 metamorphosed sole for lots D, E and F, versus 200 to 2400 for the other lots). In addition, the proportion of impaired pigmentation (Table VI) varied from 30 to 80% at the end of the experiments, and was significantly different between lots from same spawning. It seems that certain rearing conditions might produce these differences, as found by Shelbourne (1964) with plaice. On the other hand, a relation between weight and pigmentation did not appear within each lot, though the proportion of anomalies was the lowest in the best lots (30-40s for lots B, C, J and K). CONCLUSION

Fuchs (1979) obtained 400 mg as the mean weight of sole, 60 days old, weaned by day 25, with 40% survival from this date (30% from hatching). This survival rate might be expected with weaning prior to metamorphosis, but one would expect the growth rate to be five to ten times lower, and the amount of live nauplii to be more than 12 times lower. The amount of frozen nauplii required for weaning by day 25 was also quite high. Hence there is a choice to be made between these two ways of weaning: if the best growth rate is considered more important than a low food cost for the present day production of young sole, (i.e. if they must be weaned after day 25), it is important to carry out further experiments in order to improve the growth rate of sole weaned before metamorphosis. ACKNOWLEDGEMENTS

This study was supported by the CNEXO (contract number 79-6056). The experiments were performed at the “Centre Oceanologique de Bretagne”, and some of them with the aid of the facilities at the “Laboratoire National de Pathologie des Animaux Aquatiques”, with the kind permission of Dr G. Tixerand. The Kruskall-Wallis test computing was programmed by Dr G. Conan.

368 REFERENCES Anonymous, 1971. Table de composition des mat&es premieres. Comite d’Etude international. Protector. Societe Internationale d’Etude et de Zootechnie appliquhe, Luxembourg, 27 pp. Bromley, P.J., 1977. Methods of weaning juvenile hatchery reared sole (Solen soleo (L)) from live food to prepared diets. Aquaculture, 12 (4): 337-347. Czygan, F.C., 1968. On the metabolism of carotenoids in the crustacean Artemia salina. Z. Naturforsch., B, 23 (10): 1367-1368. De Veen, J.F., 1969. Abnormal pigmentation as a possible tool in the study of the populations of the plaice (Pleuronectesplatesso L.). J. Cons. Int. Explor. Mer, 32 (3): 344-383 Fuchs, J., 1978. Influence de la photoperiode sur la croissance et la survie de la larve et du juvenile de sole (Solea solea) en Blevage. Aquaculture, 15 (1): 63-74. Fuchs, J., 1979. Techniques d’elevage larvaire et production intensive de juveniles chez la sole (Solea solea). These 38 cycle, Univ. Aix-Marseille II, 238 pp. roneo. Gallagher, M. and Brown, W.D., 1975. Composition of San Francisco Bay shrimp Artemia salina. J. Agric. Food Chem., 23, 630-632. Gatesoupe, F.J. and Luquet, P., 1981. Practical diet for mass culture of the rotifer Brachionusplicatilis: application to larval rearing of sea bass, Dicentrarchus labrax. Aquaculture, 22: 149-163. Girin, M., 1979a. Some solutions to the problem of producing juvenile marine finfish for aquaculture. Conf. Aquac. on cultivation of fish fry and its live food. Szymbark, Poland, 23-28 Sept. 1977. European Mariculture Society, Special Publication, No. 4, pp. 199209. Girin, M., 1979b. Methodes de production des juveniles chez trois especes de poissons marins: le Bar, la Sole et le Turbot. Publ. CNEXO (France) (Rapp. Sci. Tech.), 39: 202 PP. Kudoh, S., 1977. Lipid metabolism of larval fish. Proc. Japan-Sov. Jt. Symp. Aquacult., 1976,5, pp. 85-89. Metailler, R. and Girin, M., 1976. Croissance de jeunes soles (Solea solea) nkes en laboratoire et condition&es a l’aliment compose. I.C.E.S. 2nd Mariculture Working group. Hamburg, May 1976.12 pp., Mimeographed. Paris, J. and Quignard, J.P., 1968. Quelques cas d’ambicoloration et d’albinisme chez Solea udgaris Quensel. Rev. Trav. Inst. P&h. Marit., 32 (4): 507-510. Riley, J.D., 1966. Marine fish culture in Britain. VII. Plaice (Pleuronectesplotessa L.) postlarval feeding on Artemiu salina nauplii and the effects of varying feeding levels. J. Cons. Perm. Int. Explor. Mer, 30 (2): 204-221. Shelbourne, J.E., 1964. The artificial propagation of marine fish. Adv. Mar. Biol., 2: l-83. Van der Wind, J.J., 1979. Feeds and feeding in fry fingerling culture. EIFAC workshop on Mass Rearing of Fry and Fingerlings of Fresh Water Fishes. The Hague, 8-11 May. FAO/EIFAC Tech. Pap. No. 35, Suppl. 1, pp. 94-102.