A re-appraisal of the potential of the sole, Solea solea (L.), for commercial cultivation

Aquaculture ELSEVIER

Aquaculture

155(I 997) 355-365

A re-appraisal of the potential of the sole, Solea solea CL.1, for commercial cultivation B.R. Howell

*

Abstract Renewed interest in the farming of sole has been stimulated largely by a desire, if not a need, for the existing marine fish farming industry to diversify. Despite the extensive studies of the 1960s and 197Os, commercially viable cultivation techniques for this valuable species were not realised. This species proved relatively easy to rear through the larval stages but the juvenile stages performed poorly on formulated feeds, displaying low growth rates and an apparently high susceptibility to disease. Consequently, effort was directed to other species which did not present such difficulties. Recent research has demonstrated that the technical problems may not be as intractable as was once thought. This paper reviews the results of these studies, which have focused particularly on the problems of providing adequate nourishment to the larvae and juvenile stages. They have demonstrated (a> the ease with which larvae may be reared to the juvenile stages and a link between larval diet quality and juvenile performance, (b) that the reputedly virulent disease, black patch necrosis, may be associated with nutritional deprivation and that juveniles may be grown successfully without a sand substrate, (c) that juveniles can attain a growth rate of over 3 cm per month on natural prey and (d) that diets may be formulated which support survival rates in excess of 90% during weaning and subsequent growth rates approaching those on natural prey. The implications of this work on the prospects for developing commercially viable culture methods is discussed with reference to other important biological characteristics of the species, such as their response to crowding. It is concluded that there are no insuperable problems to the development of cultivation methods for the sole, but further work is required in certain critical areas before economic feasibility can be demonstrated unequivocally. Crown Copyright 0 1997 Published by Elsevier Science B.V. Kr~~oud.s: Sole; Cultivation;

_ Tel.: +44-1492-593883;

Larvae: Juveniles:

Weaning;

fax: +44-1492.592123:

Growth; Crowding

e.mail: b.r.howell@dt’r.maff.gov.uk

0044.8486/97/$17.00 Crown Copyright 0 1997 Published PI1 SOO44-8486(97)OOlO3-8

by Elsevier Science B.V.

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1. Introduction A recent revival of interest in the possibility of farming soles has been stimulated largely by indications of market saturation for established species such as sea bass, Dicentrurchus labrax, and sea bream, Sparus aurata. To diversify their activities, some farms in southern Europe, notably Spain, have established sole broodstocks and in 1994 these were reported to have supported a production of about 600000 juveniles (Anonymous, 1995). In these cases the species was Solea senegalensis which has a more southerly distribution than that of the more commonly studied Solea solea. Although this paper is primarily concerned with the latter species, these two closely related species have a similar biology (Whitehead et al., 1986) and are likely to present comparable problems in culture. The consistently high price attracted by sole in European markets has repeatedly stimulated attempts to develop rearing methods for this species, the earliest dating back to the turn of the century (Fabre-Domergue and Bietrix, 1905). Although these authors met with limited success, farming only became a realistic aspiration following the demonstration that juveniles could be reared in large numbers using Artemia nauplii as food (Shelboume, 1975). This and subsequent work in both the U.K. (for example, see Howell, 1973) and France (for example, see Fuchs, 1982) demonstrated that of the marine fish species for which larvae culture techniques have now been developed, none is more easily reared than the sole. Despite this, commercial farming did not prove feasible mainly because subsequent developmental stages proved difficult to feed. A marked reluctance of small juveniles to accept fish-based formulated feeds was overcome by the inclusion in the feeds of invertebrate tissue (Bromley, 1977) or chemical taste attractants (Mackie et al., 1980) but growth and survival rates were often unacceptably low and the species appeared to be extremely vulnerable to disease. The most devastating of these was a condition known as black patch necrosis (BPN) (McVicar and White, 1979) which it seemed could only be prevented or controlled by the provision of a sand substrate (McVicar and White, 1982). These difficulties were sufficient to divert research effort and commercial investment during the 1980s to other less problematic species such as the sea bass and the turbot (Scophthalmus maximus). Recent research, undertaken as part of an assessment of the feasibility of exploiting hatchery techniques to enhance natural stocks of this species, has indicated that the problems of rearing juvenile sole may not be as intractable as was once thought. This paper reviews the results of this work as part of a wider appraisal of the prospects of developing commercial farming methods for this species. The scope is limited to assessing the technical, rather than the economic, feasibility of farming sole but emphasis is given to those aspects of importance in determining economic viability.

2. Juvenile production This species readily spawns naturally in captivity (Baynes et al., 1994) and supplies of fertilised eggs to support larvae rearing trials are readily secured. A review of egg

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production in captive sole (Baynes et al., 1993) showed that annual egg production ranges widely from about IO-140 eggs g- ’ of female with a tendency for the lower fertility rates to occur when the previous winter water temperatures did not fall below 12°C. Variable fertilisation rates are a common feature of eggs spawned by captive stocks with average fertilisation rates for complete spawning seasons ranging from about 25-80%. This, however, does not impose a significant limitation on rearing operations because fecundity and larval survival are high. Spawning time varies with latitude but can be displaced by several months by manipulating photoperiod and/or temperature profiles, although there is some evidence that manipulated stocks produce fewer and less viable eggs than normal stocks. Rearing the larvae through to metamorphosis similarly presents few problems with survival rates being consistently in excess of 70% in small-scale laboratory systems (for examples see, Howell, 1973; Shelboume, 1975; Fuchs, 1982). A particular advantage of this species is that the larvae can be reared on a diet of freshly-hatched Artemia nauplii without prior enrichment with algae or proprietary ‘booster’ diets. The larvae have also been reared on a diet of rotifers offered either as the exclusive food (Howell, 1973) or in combination with Artemia nauplii (Fuchs, 1982), but in neither study was survival enhanced by the availability of this smaller food organism. The relative ease with which larvae can be reared may reflect in part the consistent quality of the fertilised eggs produced by captive stocks which, because they are the product of natural spawning, are not subject to over-ripening-induced variations in quality evident in fish from which the gametes are manually stripped (for example, see Howell and Scott, 1989). Perhaps of greater significance is the indication that the requirement of sole for dietary (n - 3) HUFA is less stringent than that of many other marine species (Howell and Tzoumas, 1991). These authors concluded that, whereas sole have an essential dietary requirement for 20:5(n - 3), high survival rates may be achieved on diets almost deficient in 22:6(n - 3). Thus, enhancing the lipid content of Artemia is not a prerequisite of high survival in this species if strains rich in 20:5(n - 3) are used. More recent work, however, has indicated that survival rate alone may not be an adequate criterion by which to judge rearing methodology. Howell (1993) found considerable variation in the low-temperature tolerance of reared juvenile sole and subsequently established that this was attributable to the quality of the diet on which the larvae were reared rather than the diet on which the juveniles had been fed for the five months prior to exposure to low temperature (Howell et al., 1995). The important implication of this study is that diet quality during the larval stages may have a lasting effect on the characteristics of the reared fish, although the persistence of these traits has not yet been fully assessed. Quantitative requirements for specific nutrients, particularly lipids, during the larval stages remain unknown but are currently being assessed with regard to their influence on subsequent performance characteristics. These not only include stress tolerance but the success of transfer from live to formulated feeds and growth rates, both of which are influenced by larval diet quality in other species of flatfish (Howell, 1977; Bromley and Howell, 1983).

358

3. Growth potential

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of sole

The potential growth rate of any species can only be assessed fully if optimum conditions, particularly in relation to temperature and food, are known. Comprehensive data are often lacking, but for the sole two studies have sought to quantify the effects of temperature (Irvin, 1973; Fonds, 1975). Both authors used live foods which, though not of the type naturally exploited by the species, would be expected to support growth rates closer to the maximum than those sustained by formulated feeds. Irvin (1973) monitored the growth rate of hatchery-reared juvenile sole of an initial mean total length of about 5 cm at five temperatures ranging from 1 l-27°C for a period of 12 weeks. The fish were fed ad libitum on the oligochaete worm Lumbricillus riualis, which was known to support high growth rates of juvenile plaice, Pleuronectes platessa (Kirk and Howell, 1972). In contrast, Fonds (1975) worked with wild-caught fish of a larger initial size (12-13 cm> and followed their growth for over a year at temperatures ranging from lo-25°C. The fish were fed daily with fresh chopped mussel (Mytilus e&is) or live lugworm (Arenicola marina), although no indication is given of the relative amounts offered or whether the fish were fed to satiation. Irvin’s data showed an approximately linear increase in growth rate (Lr) from 9-3 1 mm/month as temperature (T) increased from 1 l”C-19°C (Fig. 1). This relationship was represented by the equation Lr = 2.7 T - 21.9 (r’ = 0.99; p < 0.01) and is used later to provide a measure of growth potential for comparison with observed growth rates of small fish reared within this temperature range. The fish in Fonds’ experiments grew more slowly than those of Irvin’s, but both experiments showed little increase in

10

15

20 Temperature

25

30

(“C)

Fig. I. The relationship between rate of increase in length and temperature for juvenile sole calculated from the data of Irvin (1973) and Fonds (1975). For Irvin’s data the regression of growth rat? on temperature for temperatures between I I and 19°C is also shown (dotted line).

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3.59

01 0

50

100

150

200

250

300

350

Days Fig. 2. The increase in length of sole fed an ad libitum diet of an oligochaete worm (L. ricdis) (data from Irvin, 1973) at 19°C and sole fed daily on mussel (M. edulis) or lugworm (A. murim) at 20°C (data from Fends. 1975). The horizontal line shows the minimum market size of 240 mm.

growth rates above 20°C and indicated that the optimum temperature for growth may be about 23-25°C. Taking Irvin’s data at 19°C and Fonds’ at 20°C it can be seen that fish of about 5 cm length may attain the minimum market size of 24 cm (125 g> at temperatures close to the optimum in less than 300 days (Fig. 2). It is evident, however, that the growth rates obtained by Irvin were appreciably higher than those of Fonds even for the size range common to both studies. While recognising that a decrease in growth rate with age would be expected, the difference may have been accentuated by either the quality or the availability of the foods used in the two studies. This might suggest that market size may be attained in an even shorter time. The important question in an aquaculture context is whether such high growth rates can be attained on formulated feeds.

4. Use of formulated

feeds

Many studies during the 1970s and 1980s demonstrated that juvenile sole could be weaned from live food to formulated feeds and that success was dependent largely on the inclusion of either invertebrate tissue (see, for example, Bromley, 1977; Metailler et al., 1881) and/or chemical taste attractants (see, for example, Mackie et al., 1980; Metailler et al., 1983). These studies focused primarily on the attractiveness of the diets but there is evidence that further improvements may arise from a consideration of the ability of the fish to utilise the diets. In a recent experiment, Day (in press) found that

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0

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54

HFPC

60

CONTROL

content (%)

Fig. 3. Survival of 3 cm sole following transfer to a formulated feed containing various proportions of HFPC and a control diet in which protein was provided by krill, blood, mussel and polychaete meals Day (in press).

the survival of 3 cm long sole during weaning was directly dependent on the content of hydrolysed fish protein concentrate (HFPC). Despite the inclusion of betaine to improve the attractiveness of the diets, increasing the HFPC content from O-80% resulted in a progressive increase in survival from just over 40% to more than 75% (Fig. 3), a survival rate approaching that on the control diet which consisted of high levels of invertebrate material. It may have been that the leaching of soluble proteins and amino acids from the experimental diets further enhanced their attractiveness but it is also possible that the more readily digested HFPC resulted in higher assimilation rates at a time when ingestion rates may have been relatively low. Similar effects were reported in a recent study of weaning in sea bass larvae (Cahu and Zambonino Infante, 1995). These authors concluded that protein hydrolysates may attenuate the delay in the maturation of intestinal digestion which can be induced during weaning with compound diets. Further weaning trials (unpublished data) were conducted recently at this laboratory using a commercial larvae feed produced by a process of agglomeration (Norwegian Herring Oil and Meal Industry Research Institute (SSF), Fyllingsdalen, Norway). This diet was customised for sole by the inclusion of a feeding attractant (betaine) at 6% of the dry weight and by increasing the level of water-soluble protein to about 30% of the total protein. The diet was readily consumed by 29 mm long sole and mortalities were negligible during the six weeks of the trial. Over this period, the mean length of the fish increased to 59 mm, representing a mean growth rate of 21 mm/month. In Fig. 4, growth during each two-week period is compared with the ‘potential’ growth predicted from the growth/temperature relationship derived from Irvin’s data (see Section 3 and Fig. 1). The percentage of the predicted growth attained was 57, 70 and 80 during the

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65

60

30

L

25

,

0

5

10

15

20

25

30

35

40

45

Days

Fig. 4. Change in mean length of sole following direct transfer from Artemia nauplii to a commercially prepared formulated feed (SSF). The vertical bars represent standard deviation. ‘Potential’ growth for each growth period predicted from data of Irvin (1973) is also shown (broken line).

three growth periods respectively. This progressive increase may have reflected increasing acceptance of the novel diet and/or an increase in the digestive competence of the fish. The importance of this trial is that it demonstrates that young sole can be weaned on to commercially prepared formulated feeds with extremely high survival and that such diets can support growth rates approaching those attainable on live foods.

5. Susceptibility

to disease

By far the most serious disease that has been reported in populations of reared sole is BPN, a condition first described by McVicar and White (1979) and subsequently discovered to be caused by the bacterium Flexibacter maritimus (Bemadet et al., 1990). Outbreaks of this reputedly highly infectious disease devastated stocks and effective prevention and control only appeared possible by the provision of a sand substrate (McVicar and White, 1982). These experiences led to a widely held view that sole was susceptible to disease and could only be successfully cultured on a sand substrate, a requirement many would consider to be a serious impediment to the maintenance of hygienic conditions. Recent work, however, suggests that sole may not be as vulnerable to disease as these experiences suggested. Baynes and Howell (1993) described the occurrence of BPN among fish fed cooked and stored mussel, whereas neighbouring groups fed fresh

362

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155 (19971355-365

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Fig. 5. The survival of groups of sole fed fresh mussel (F), cooked mussel (C) and cooked mussel with one (C + 1) or two (C + 2) feeds per week of fresh mussel. Each line is the mean of two tanks. (Redrawn from Baynes and Howell, 1993).

mussel remained free of disease despite their close proximity and the lack of rigorous precautions to minimise the spread of disease (Fig. 5). None of the groups were provided with a sand substrate. The conclusion from this trial was that a combination of adequate nutrition and the maintenance of hygienic conditions is sufficient to avoid the occurrence of BPN and that the provision of a sand substrate is not a prerequisite for successful culture of sole. This conclusion is supported by the lack of serious disease outbreaks in the recent extensive experimental programmes at the Fisheries Laboratory, Conwy.

6. Crowding

effects

Production, i.e. the weight of fish which can be produced per unit area of the rearing facility in a given time, is an important determinant of economic viability and is a function not only of growth rate but of the density at which the fish are stocked. Thus, tolerance to crowding is an important requirement of fish selected for intensive cultivation. There is some evidence that sole is less well suited to intensive culture conditions than some other species. An experiment in which sole were grown from a mean length of about 5 cm (1.5 g) to over 10 cm (lo- 13 g), under conditions designed to quantify

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363

t \

I

0.50

0

100

200 Stocking

300 density

400

500

(fish rn-‘)

Fig. 6. The relationship between stocking density and growth rate of sole of an initial mean length of about 5 cm grown for 12 weeks on an ad libitum diet of the oligochaete worm L. r;~lis. The line was calculated by linear regression analysis of growth rate (L) on logarithmic values of stocking density (D) and is represented by the equation L = 0.74 - 0.073 log D (r’ = 0.87; p < 0.001). (Data from Howell, 1977).

social rather than water quality effects on growth, demonstrated a significant negative effect of stocking density on growth rate (Howell, 1977). The growth rate of fish stocked at a density of 500 fish rn-’ was about 15% less than those stocked at 17 fish mP2 (Fig. 6). Such a decline in growth rate with increasing stocking density was not observed in a similar experiment with turbot (Howell, 1977), probably reflecting the different feeding behaviour of the two species. In contrast to the turbot, sole take food from the bottom rather than the water column and are adapted to eat small but frequent meals (de Groot. 1969). This type of behaviour provides greater opportunities for interaction between individuals within communal populations than that displayed by the turbot which is readily satiated by a relatively small number of feeding opportunities each day. In the experiment referred to above, although the fish were fed ad libitum on the oligochaete worm, L. ricalis, the thigmotactic behaviour of this organism resulted in the worms being concentrated into a small number of clumps in each tank. This may have provided an opportunity for some of the fish to have dominated the food supply either by active aggression or merely a passive inhibition. This contention is supported by a separate experiment which failed to demonstrate any difference in growth variation between individually and communally held groups of sole (Quiros and Howell, 1993). In this instance the fish were fed on Artemiu nauplii which, because they were evenly distributed within the tanks, could not be dominated by small numbers of individuals. It would appear, therefore, that any tendency for damaging interactions within communal populations could be overcome by the adoption of appropriate feeding strategies.

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B.R.

7. Conclusions This review of the current status of techniques for the cultivation of sole suggests that there are no insuperable technical obstacles to farming the species, although it is recognised that research in certain critical areas is still needed before its potential can be demonstrated convincingly. The principal conclusions are enumerated below. (1) The hatchery production of juveniles in particular is undoubtedly more readily accomplished than for any species currently farmed, although, in common with other marine species, recent research has indicated that the performance characteristics of the juveniles may be improved by further optimisation of larvae diet quality. (2) Trials using live foods have shown that 5 cm long juveniles have the potential to attain the minimum market size of 24 cm (12.5 g) in less than 300 days at temperatures approaching the optimum. (3) Small (3 cm long) juveniles can be weaned with negligible mortalities on to commercially produced artificial diets which can support growth rates up to 80% of that attained on live foods. (4) There is no evidence that the sole is more susceptible to disease than other species. The reputedly virulent disease, BPN, may be linked to nutritional deprivation and fish can be grown successfully without a sand substrate. (5) The mode of feeding of sole may result in levels of interaction between individuals which may depress overall growth rates and increase variability in communal populations. Nevertheless, it is considered that this tendency may be minimised by the adoption of appropriate feeding strategies. Further work is still required in certain critical areas before the full culture potential of this species can be realised. This should include: (1) A further investigation of the link between larval diet quality and the performance characteristics of later developmental stages. (2) The further development of weaning diets particularly for smaller fish. Such studies would benefit from a further investigation of ontogenetic development of digestive competence. (3) Optimisation of on-growing diets particularly in relation to their cost effectiveness. (4) Optimisation of feeding strategies and stock management practices.

References Anonymous, 1995. Report of the Working Group on the Mass Rearing of Juvenile Marine Fish to the Mariculture Committee of ICES. ICES CM. 1995/F:4, 17 pp. Baynes, S.M., Howell, B.R., 1993. Observations on the growth, survival and disease resistance of juvenile common sole, Solea solea CL.), fed Mpilus e&is L. Aqua. Fish. Man. 24, 95-100. Baynes, S.M., Howell, B.R., Beard, T.W., 1993. A review of egg production by captive sole, Solea solea CL.). Aqua. Fish. Man. 24, 171-180. Baynea, S.M., Howell, B.R., Beard, T.W., Hallam, J.D., 1994. A description of spawning behaviour of captive Dover sole, Solea solea CL.). Neth. J. Sea Res. 32, 27 l-275. Bernadet, J.F., Campbell, A.C., Buswell, J.A., 1990. Flexibacrer maririmus is the agent of black patch necrosis in Dover sole in Scotland. Diseases of Aquatic Organisms 8, 233-237. Bromley, P.J., 1977. Methods for weaning juvenile sole from live to prepared feeds, Aquaculture 12, 337-347.

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P.J., Howell, B.R., 1983. Factors influencing the survival and growth of turbot larvae, Scophthnlmus L., during the change from live to compound feeds. Aquaculture 31, 31-40 Cahu, C.L., Zambonino Infante, J.L., 1995. Effect of the molecular form of dietary nitrogen supply in sea bass larvae: response of pancreatic enzymes and intestinal peptidases. Fish Physiol. Biochem. 14, 209-214. Day, O.J., Howell, B.R.. Jones, D.A., in press. The effect of hydrolysed fish protein concentrate on the survival and growth of juvenile Dover sole, Solea soleo CL.), during and after weaning. Aquaculture Research. Fabre-Domergue, P., BiCtrix, E., 1905. Developpement de la sole (Solea ~~ulgaris). Travail du Laboratoire de Zoologie Maritime de Concameau. Vuibert et Nony, Paris, 243 pp. Fonds, M., 1975. The influence of temperature and salinity on growth of young sole Soled solea L. In: Persoone, G., Jaspers, E. (Eds.), 10th European Symposium on Marine Biology, Ostend, Belgium, September 17-23, 1975, Mariculture: vol. 1, pp. 109-125. European Aquaculture Society. Bredene, Belgium. Fuchs, J., 1982. The production of juvenile sole (Solea solea) under intensive conditions. 1. The first month of rearing. Aquaculture 26, 321-337. de Groot, S.J., 1969. Digestive system and sensorial factors in relation to the feeding behaviour of flatfish (Pleuronectiformes). J. Cons. Int. Explor. Mer 32, 3855394. Howell, B.R., 1973. Marine fish culture in Britain VIII. A marine rotifer, Brachionus plicatilis Muller, and the larvae of the mussel, Mytilus rdulis L., as foods for larval flatfish. J. Cons. Int. Explor. Mer 35, l-6. Howell, B.R., 1977. Aspects of the development of cultivation techniques for flatfish. Ph.D. Thesis. University of Liverpool. 105 pp. Howell. B.R., 1993. Fitness of hatchery-reared fish for survival in the sea. Aqua. Fish. Man., 25 (Supplement 11, 3-17. Howell, B.R., Beard, T.W., Hallam, J.D., 1995. The effect of diet quality on the low-temperature tolerance of juvenile sole, Solea solea (L.1. ICES CM 1995/F: 13. Howell, B.R.. Scott, A.P., 1989. Ovulation cycles and post-ovulatory deterioration of eggs of the turbot, Scophthalnus maximus L. Rapp. P.-v. R&m. Cons. Int. Explor. Mer 191, 21-26. Howell, B.R., Tzoumas, T.S., 1991. The nutritional value of Arfemia nauplii for larval sole, Solea solea (L.1, with respect to their (n -31 HUFA content. In: Lavens, P., Sorgeloos, P., Jasper& E., Ollevier, F. (Eds.), Larvi ‘91 Fish and Crustacean Larviculture Symposium, Gent, Belgium. European Aquaculture Society, Special Publication No. 15, pp. 63-65. Irvin. D.N., 1973. The growth and survival of Dover sole, Solea solecl CL.1 (syn. Solea ru@ris Quensel 18061, and some observations on the growth and survival of juvenile plaice, Pleuronecres pluressa L., considered at various temperatures. Ph.D. Thesis, University of Liverpool, U.K., 186 pp. Kirk, R.G., Howell, B.R., 1972. Growth rates and food conversion in young plaice (Pleuronectes plaressa L.1 fed on artificial and natural diets. Aquaculture 1, 29-34. Mackie, A.M., Adron, J.W., Grant, P.T., 1980. Chemical nature of feeding stimulants for juvenile Dover sole, Solea solea. J. Fish Biol. 16, 701-708. McVicar, A.H., White, P.G., 1979. Fin and skin necrosis of cultivated Dover sole, Solea solea. J. Fish Diseases 2, 557-562. McVicar, A.H.. White, P.G., 1982. The prevention and cure of an infectious disease in cultivated juvenile Dover sole, Solea solea CL.). Aquaculture 26, 213-222. MCtailler, R., Menu, B., Moriniere, P., 19X1. Weaning of Dover sole (Solea ~~ulgaris) using artificial diets. J. World Maricul. Sot. 12, 11 1 - 116. Metailler, R., Cadena-Roa, M., Person-Le Ruyet, J., 1983. Attractive chemical substances for the weaning of Dover sole (Solea rxlgaris): qualitative and quantitative approach. J. World Maricul. Sot. 14, 679-684. Quiros, M., Howell, B.R.. 1993. Size variation in cultured sole. In: Carrillo, M., Dahle, L., Morales, J., Sorgeloos, P., Svennig, N., Wyban. J. (Eds.1, World Aquaculture ‘93, Torremolinos, Spain, May 26-28, 1993. European Aquaculture Society, Special Publication No. 19, 441 pp. Shelbourne, J.E.. 1975. Marine fish cultivation: pioneering studies on the culture of the larvae of the plaice (P1euronecte.s platessa L.1 and the sole (Solea solea L.). Ministry of Agriculture, Fisheries and Food, Fishery Investigations, Series II. 27 (9). Her Majesty’s Stationary Office, London, 29 pp. Whitehead, P.J.P., Bauchot, M.-L., Hureau, J., Tortonese, E. (Eds), 1986. Fishes of the North-eastern Atlantic and the Mediterranean. Unesco, Paris, 1473 pp. Bromley,

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