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In order to specify the limits of the high density larval rearing method (80–100 larvae per liter) in clear water with daily total exchange and to control the water quality evolution, the nitrite and total ammonia were measured. Nitrite concentrations in antibiotic treated tanks stayed low (5μg NO2-N/1) but can reached 40μg NO2-N/1 after 41 days in untreated tanks, in spite of daily water exchange. Maximum concentrations of total ammonia were 1.70 ppm N during a 24-hour cycle. In the rearing conditions (pH 7.85 to 8.20, temperature 25 to 28 C) the un-ionized ammonia concentrations were 0.07 to 0.18 ppm N. At those levels, no specific larval stress was noted. The interaction of variations in ammonia and nitrite concentration versus, antibiotics, temperature, light intensity, larval stages, diseases, was studied. Ammonia variations, resulting from the larval metabolism, could be a useful indicator for detecting the beginning of bacterial diseases.

As no indigenous species of commercial penaeid shrimp live in the waters of French Polynesia, the preliminary step in developing shrimp aquaculture was to obtain maturation and spawning in captivity. Five species have been investigated. Wild-caught juveniles from the New Caledonia lagoon (P. merguiensis, P. semisulcatus, M. ensis) and postlarvae from the Galveston NMFS laboratory (P. aztecus) and Fujinaga Institute (P. japonicus) have been used to obtain adult stock. Experiments on larval rearing and growth of these species are in progress. Shrimps are reared in circular tanks of 12 m3 with a continuous water circulation through a coral sand bed. Rate of exchange is from 1 to 3 times a day. Throughout the year water temperature is between 25 and 29 C, salinity around 34.5 ppt, and pH 8.2. Solar energy is reduced by shade covers. Artificial pellets of different composition are given as food. In these conditions we have obtained: 1) about 1,000 spawnings and two generations in captivity from September 1973 to September 1974 with P. merguiensis; 2) spawnings of M. ensis in 1973; 3) four spawnings of P. japonicus in September 1974; 4) about 20 spawnings of P. aztecus, but only after removing one eyestalk; 5) maturation signs in P. semisulcatus but no spawning.

To develop shrimp farming in French Polynesia where no indigenous commercial species of penaeid prawn exists, the first step is to select the right species according to the following criteria: maturation and spawning in captivity, mass production of post-larvae, fast growth at semi-intensive density, acceptability of artificial diet, disease resistance and hardiness. This paper presents the results on P. monodon, Fabricius, the largest Indo-Pacific species. Experiments have been conducted in the “Centre Oceanologique du Pacifique” in Tahiti Island where the environmental conditions are: water temperature range 25–29 C, salinity 35 ppt, pH 8.2. Beginning with 9 females and 4 males from Fiji and New-Caledonia, kept in sand bottom 12 m3 tanks, F1 generation was obtained in November 1975 and F2 generation in August 1976. Maturation is induced after one eye ablation by pinching the eyestalk. From May to July, 6 females from 45 to 130 g gave 18 spawnings which totalized 3.3 times 106 eggs, thus proving it is possible to sustain a commercial operation from captive reared animals. Mass mortalities which occurred during the larval rearing are now under control by use of antifungicides und antibiotics. Protein and energy requirements were studied by means of purified and artificial diets. It has been found that a 40% protein content and 3.3 kcal/g diet gives the best growth performance. An artificial dry pellet has been developed and 25 g mean weight animals have been harvested after 7 months in earth rearing ponds at a density of 10 ind/m2. Among 6 penaeid species under experiment in Tahiti, P. monodon is the most promising for the South Pacific tropical area.

One of the criteria for selecting a shrimp of commercial interest in French Polynesia is the acceptability of artificial diet;. such a criterion has been used to test Penaeus merguiensis. Experiments have been carried out in Centre Oceanologique du Pacifique in Tahiti island where the water temperature range is 25–29°C, salinity 35 ppt, pH. 8.2, and photoperiod constant. Juveniles used in this study are hatched in CNEXO-COP at Vairao. It has been found that a 50–55% protein content diet gives a better growth performance. A carbohydrate such as starch appears more suitable than glucose or glucose plus starch in isonitrogenous purified diets. A vitamin mix rich in vitamin C, choline and inositol provides better results and a mineral mix with 3% magnesium reaches optimum. The major nutritional results for this species are applied to formulation of artificial diets. With the best diet, growth performances are normal: from 2.8 g to 9.0 g in 90 days, with about 60% survival rate at a low density, 20 animals/m2 under strict control. But at another scale, in 400 m2 grow-out tanks, growth was rather low even with an excellent Japanese diet containing 60% protein. Therefore, P. merguiensis does not appear to be a good candidate species for aquafarming in French Polynesia.

Three shrimp species, Penaeus monodon, P. stylirostris (Panama and Mexican strains) and P. vannamei have matured and spawned in captivity at the Centre Oceanologique du Pacifique (COP) laboratory. The shrimp, originally stocked as juveniles or postlarvae, were reared to adult size in tanks and ponds and have completed the cycle: F3 generation for P. monodon, F2 for P. stylirostris (Panama strain) and P. vannamei and F1 for P. stylirostris (Mexican strain). Maturation occurs naturally under our rearing conditions or is induced by unilateral eyestalk ablation. Details are given on mating behavior, ovarian development, number of spawnings, egg viability and maintenance of captive brood stock. Partial results so far obtained for P. monodon and P. stylirostris clearly show a reared brood stock could sustain a commercial hatchery.

First important problems in pathology at the Centre Oceanologique du Pacifique (COP) have been met during larval rearings of penaeid shrimps and Macrobrachium rosenbergii. In penaeids, heavy mortalities during the zoea and mysis stages have led to the diagnosis of two main types of diseases: a bacterial necrosis of the appendages and a fungus disease. Two preventive treatments with antibiotics during the zoea stages and a continuous treatment with a selective herbicide (Treflan) allow a consistent production of 100 post-larvadliter (80% survival from the nauplius stage). With Macrobrachium rosenbergii, during the larval rearing, mortalities of bacterial origin have been recorded in some experiments. The observation of appendage necrosis allows early diagnosis and treatment with antibiotics, Chlorination of the water helps to control the disease. During the growth of penaeids, different diseases have been encountered and are briefly described. “White pleura disease” due to a Vibrio sp. is the only one that has produced important mortalities in P. azetecus, P. merguiensis and P. japonicus but does not seem harmful to P. monodon. These observations are discussed and conclusions about the importance of diseases in crustacean cultures in tropical area are stated.

Tropical species such as P. monodon, P. vannamei, and P. stylirostris were first considered as candidate species for aquaculture in early 1970s or around 25 years ago. At that time, the first nutrition studies began in laboratories using wild stock. Most labs were under pressure to find quick answers to the formulation of shrimp feeds. Feed manufacturers conducted a number of proprietary experiments. Shrimp nutritionists did not link their problems to those encountered with monogastrics and specific problems were faced such as leaching of nutrients, slow feeding response of shrimp, and lack of proper methodology. Even today, despite new advances in New Caledonia with P. stylirostris or in Ecuador with P. vannamei, empiricism is present and formulae calculated with a least cost program do not prove to be fully satisfactory. There is need for a better understanding of shrimp nutrition in the tropical climates. There is still a gap to fill between results of experiments conducted in fully managed water and f...

This paper describes the changes in the total and differential haemocyte counts during the moult cycle of the shrimp, Penaeus stylirostris . Correlative measures of phenoloxidase (PO) activity and resistance to infection against vibriosis were also investigated during the moult cycle. Three types of cells are identified: hyaline cells (HC), which are small with a big nucleus, represent 80% of the total; semi-granular cells (SGC) represent 10–13%; and large granular cells (LGC) represent 4–10% of the total cells, being the largest cells with highly eosinophilic intracytoplasmic granules. Significant variations of total haemocyte count (THC) between intermoult and premoult were recorded; a minimum in the former and a maximum in the latter. The PO activity measured at the same time decreased during the moult cycle but when compared to the THC was higher at intermoult. The variations in PO activity were similar to those of the relative percentage of the LGC, showing its role in the prophenoloxidase system (proPO-system). The resistance to infection was studied by performing an in vitro assay. Experimental infection with a highly pathogenic Vibrio AM23 was carried out by bathing selected shrimps in a concentration of 10 5 cfu ml −1 at intermoult and premoult. The mortality of shrimps in premoult was 48% while in intermoult the mortality was 21%. This indicated that shrimps infected in premoult were more sensitive to vibriosis than in intermoult. Further, the variations of selected parameters (i.e. THC, PO) seem to be consistent with the in vivo response against the highly pathogenic Vibrio AM23.

Apparent digestibility coefficients (ADC) of carbohydrate, protein and lipid were investigated in Penaeus vannamei (18–25 g) with diets containing eight starches of various origin. Test ingredients, included at a level of 35% of diet, were native (NC) or gelatinized (GC) corn starch, waxy corn starch, either native (XC) or gelatinized (GX), high amylose corn starch (AC), potato starch, either native (NP) or gelatinized (GP), and native wheat starch (NW). Experimental diets differed only in the type of starch. Chromic oxide was included as a marker. On each starch sample, water solubility index (WSI) was determined and in vitro digestibility assays were carried out with shrimp digestive gland homogenates in order to evaluate correlations between criteria. In vitro digestibility was estimated as the initial rate of hydrolysis (IRH) in micrograms of reducing units per minute per microgram of substrate in glucose equivalents. Starch ADC ranged from 63.1 (AC) to 95.8% (GX), WSI ranged from 0.06 (NP) to 0.69% (XC) for native starch and from 55 (GX) to 85% (GP) for gelatinized starch, while IRH was between 17 (AC) and 89.10−4 μg min−1 μg−1 (GC). Significant differences (P < 0.05) appeared within each of the parameters depending on the source of dietary starch; in vitro tests were significantly (P < 0.05) correlated with each other as was IRH with starch ADC (y = 8.0 In(104x) + 59.0; R2 = 0.81; x representing IRH). IRH appeared to be more suitable than WSI to predict in vivo digestibility for starch. Protein and lipid ADC which ranged from 94.1 to 97.8% and from 76.6 to 84.8%, respectively, were also significantly affected, thus indicating some associative effects.

Selecting an embryonic developmental stage and a cryoprotective solution was the first step of our investigation on the freezing of banana shrimp, Penaeus indicus , embryos. Among the five developmental stages studied, 4-cell, 16-cell, morula, gastrula, and 5-h embryos, only the latter two were resistant enough to withstand a prolonged contact with cryoprotectants. The main obstacle to cryoprotectant penetration into the embryo was the hatching envelope. Its permeabilization by exposure to a chlorine solution was preferable to a protease-based method. Eleven cryoprotectant additives were tested. Those with molecular weights greater than that of dimethylsulfoxide (Me 2 SO) penetrated the embryos too slowly and were abandoned. The fastest permeations after permeabilization of the hatching membrane were obtained with methanol, Me 2 SO, ethylene glycol, and 1,2-propanediol. Combinations of methanol (4 or 5%) and one of the latter (4 or 5%) were used, giving hatching rates similar to those of the control.

The osmoregulatory capacity (OC) was used to study the effects of hypoxia in Penaeus vannamei. Since OC varied with molt stages with a tendency for animals to show a reduced OC before and after ecdysis, only shrimps at stages C-D0 were consequently used. Hyper-OC and hypo-OC, respectively, measured at low salinity and in seawater, were both depressed after 1–2 days exposure to low oxygen tension (PO2) ranging from 4 to 8 kPa. Low PO2 effect was time-dependent. OC recovered fully after 24 h in an O2 saturated medium. OC measurement is confirmed as a convenient tool to monitor the physiological condition and the effect of stress in crustaceans.

Spermatophore regeneration was studied in Penaeus vannamei to determine its relationship to the intermoult cycle. The spermatophore and sperm mass arrive in the terminal ampulla during the night of moulting. Ecdysis does not induce the release of melanized spermatophores. Sperm quality assessed by the percentage of abnormal sperm was found to be constant during the intermoult cycle. However, spermatophore colour evolves from a translucent state (day 1 to day 6) to a pearly colour (day 6 to day 12) then a white colour (day 10 to day 14). Spermatogenesis is not related to the intermoult cycle and seems to be continuous in captive males.

Shrimp farming has been developed in Tahiti thanks to the domestication of P. stylirostris which was introduced from Mexico and Panama in several times between 1970 and 1980. In order to balance the 25 year erosion of the available genetic variability (due to selection and drift), reintroduction of variability was tried by mating wild Equatorian males with domesticated Tahitian females. Sperm refrigeration was tested and used in order to limit the sanitary risks linked to this importation. Zootechnical and sanitary problems (Taura Syndrom Virus was detected in the quarantine facilities) did not enable to take individuals of the second generation out of the quarantine. Nevertheless this trial enabled to confirm with microsatellites markers the suspected low variability of the Tahitian strain and the interest to use several males to inseminate each female (production of half-sib families), La crevetticulture s’est développée à Tahiti grâce à la domestication de P. stylirostris, espèce introduite du Mexique et du Panama en plusieurs fois entre 1970 et 1980. Afin de compenser l’érosion dont la variabilité génétique de cette espèce a fait l’objet (par sélection et par dérive) en plus de 25 générations de domestication, une tentative de réintroduction de variabilité à été menée à partir de géniteurs mâles sauvages équatoriens croisés avec des femelles domestiquées de Tahiti. Une technique de réfrigération de sperme a été testée à cette occasion afin de limiter les risques sanitaires liés à cette opération. Des problèmes zootechniques et sanitaires (détection du virus du Taura Syndrom en quarantaine) ont empêché la sortie d’individus de seconde génération hors de quarantaine. Néanmoins cette opération a permis de confirmer à l’aide de marqueurs microsatellites la faible variabilité suspectée de la souche tahitienne et l’intérêt d'utiliser plusieurs mâles pour féconder une femelle (production de familles de demi frères).

Shrimp farming has been developed in New-Caledonia thanks to the domestication of P. stylirostris which was introduced from Mexico and Panama in several times between 1970 and 1980. In over than 25 generations the genetic variability initially available was eroded (by selection and drift) which is demonstrated by four microsatellites markers in this study where five populations of New-Caledonia are compared with a Tahitian population (population with low variability but known to be genetically improvable and a priori genetically close to the New-Caledonian populations) and with a wild Equatorial! population (a priori representative of the genetic variability of the species). In the six reared populations the allelic diversity and the heterozygosity level are low (1 to 3 alleles per locus instead of 14 to 25; 10% to 20% heterozygosity instead of 90%). In addition, the Tahitian and Caledonian strains have the same alleles, which suggests (i) that the loss of alleles occured during the common history of these populations at the beginning of their domestication and (ii) that a selective breeding program could generate in New Caledonia a significant (but limited) genetic improvement equivalent to the one obtained in Tahitian experiments. Nevertheless, the very low genetic variability of the New-Caledonian domesticated populations represents a risk to be unable to adapt to an environmental change (controlled or uncontrolled). The results of the present study demonstrate, on objective data, the usefulness of introducing genetic variability in New-Caledonia, but on the condition that it is correctly managed and that all the consequences in terms of risk management are integrated by the institutions in charge of the development of the shrimp farming industry., La crevetticulture s’est développée en Nouvelle-Calédonie grâce à la domestication de P. stylirostris, espèce introduite du Mexique et du Panama via Tahiti, en plusieurs fois entre 1970 et 1980. En plus de 25 générations, la variabilité génétique initialement disponible a subi une érosion (par sélection et par dérive) que quatre marqueurs microsatellites mettent en évidence dans cette étude dans laquelle cinq populations de Nouvelle-Calédonie sont comparées à une population de Tahiti (population peu variable mais reconnue comme génétiquement améliorable, et a priori proche de celle de NC) et à une population sauvage d’Equateur (a priori représentative de la variabilité génétique de l’espèce) : dans les 6 populations d’élevage, la diversité allélique et le niveau d’hétérozygotie s’avèrent très réduits (1 à 3 allèles par locus au lieu de 14 à 25 ; 10% à 20% d’hétérozygotie au lieu de 90%). En outre, les souches Tahitiennes et Calédoniennes disposent des mêmes allèles, ce qui suggère (i) que la perte d’allèles a eu lieu lors de l’histoire commune des ces populations au début de leur domestication et (ii) qu’un programme de sélection mené en Calédonie devrait permettre d’engendrer à terme un progrès significatif mais limité, équivalent à celui réalisé à Tahiti en expérimentation. Néanmoins, la très faible variabilité génétique du cheptel calédonien l’expose au risque de ne pas être capable de s’adapter à un éventuel changement (contrôlé ou non) des conditions d’élevage. Les résultats de cette étude permettent de confirmer, sur des bases objectives, l’utilité de l’introduction de sang neuf en Calédonie, à condition qu’il soit géré convenablement sur la durée et que les responsables du développement de la filière en intègrent toutes les implications en termes de gestion du risque.

Progress report of the different research programs of the tropical aquaculture laboratory of the « Centre Océanologique du Pacifique » (January to December 1998) : - Pearl oyster : Physiology, Ecophysiology, Nutrition - Penaeid shrimp : Ecophysiology, Pathology, Nutrition, Genetics, Cryopreservation, Immunology, Bilan de l'activité des différents programmes de recherche du Laboratoire d'Aquaculture Tropicale du Centre Océanologique du Pacifique au cours de l'année 1998 : - Huître perlière : Physiologie, Ecophysiologie, Bilan énergétique - Crevettes pénéides : Ecophysiologie, Pathologie, Nutrition, Génétique, Cryoconservation, Immunologie

Progress r-eport of the different research programs of the tropical aquaculture Lab. of the «Centre Océanologique du Pacifique « (January to December 1996) : - Penaeid shrimp : Ecophysiology, Pathology, Nutrition, Genetics, Cryopreservation, Development physiology - Pearl oyster : Physiology, Ecophysiology, Nutrition, Bilan de 1 'activité des différents programmes de recherche du laboratoire d'Aquaculture Tropicale du Centre Océanologique du Pacifique au cours de l'année 1996: - Crevettes pénéides Ecophysiologie, Pathologie, Nutrition, Génétique, Cryoconservation, Physiologie du développement - Huître perlière: Physiologie, Ecophysiologie, Bilan énergétique

Progress report of the different laboratories of the "Centre Océanologique du Pacifique" (January to December 1995) : - Peneid shrimp : Ecophysiology, Pathology, Nutrition, Genetics, Cryopreservation, Development physiology - Pearl oyster : Ecophysiology, Nutrition, Bilan de l'activité des différents programmes du laboratoire Aquaculture Tropicale du Centre Océanologique du Pacifique : - Crevettes pénéides Ecophysiologie, Pathologie, . Nutrition, Génétique, Cryoconservation, Physiologie du développement - Huître perlière

National audience

La technique de tri pratiquée avec une maille carrée de 2 mm est bonne et performante par son efficacité et son rendement. Elle est facilement mise en oeuvre sans main-d'oeuvre supplémentaire. Le grossissement des animaux triés montre un effet très positif pour les grandes post- larves avec une réduction de la dispersion et un gain en indice de conversion. Pour les petites post-larves c'est l'inverse avec une augmentation de dispersion et de mortalité dû à une forte présence de queues de lôt.

La capacité de transfert en oxygène dissous de plusieurs systèmes d'aération utilisés dans l'élevage intensif des Crevettes Pénéides a été mesurée selon la méthode standard de Boyd.Les tests se sont déroulés en bassins de 100 m2 dans un premier temps, puis en bassins de 500 et 1400 m2 pour se rapprocher de la géométrie des bassins d'élevage intensif.Les comparaisons ont porté sur les paddle-wheels Nan Rong de 1 et 2 HP, sur le paddle-wheel Giovani Milanese de 3 HP, les Aire 02 de 1 et 2 HP, sur des associations brasseur-aérateur, et enfin sur l'aération par rampe de bullage.Les résultats des mesures ont permis de sélectionner pour leurs bonnes performances les aérateurs de surface les plus utilisés dans le Sud-Est Asiatique les paddle-wheels Nan Rong de 1 et 2 HP, ainsi que leur concurrent américain, l'Aire 02 de 2 HP. Le choix entre ces deux types d'appareil se fera d'après des critères de prix, de facilité d'entretien et de facilité d'utilisation.

Le CAR (Crustacean Algae Replacement) se substitue totalement aux algues pour un dosage et une fréquence de distribution déterminés. Les résultats de survie à Zoé3 restent malgré tout variables. La raison essentielle semble être la qualité bactériologique de l'eau de mer. Les artémias peuvent être remplacés à 50% par du CD3 (Crustacean Diet), ce taux de substitution offre le meilleur compromis survie et qualité des PL.

Deux séries d'expérimentation ont été menées pour tester les performances en nurserie des deux microparticules mises au point dans le groupe IFREMER/FA/SANOFI : l'ACAL et le FRIPPAK FLAKES. Alors qu'en survie et en croissance en taille (longueur totale) aucune différence n'est mise en évidence, l'ACAL permet de produire des prégrossies de poids sec supérieur et nettement plus résistantes aux chocs de salinité que le FRIPPAK.

Ce rapport fait le point sur nos connaissances, et les résultats des expérimentations menées au COP sur les virus des pénéides. Sont également inclus des détails sur les méthodes de diagnostic sur le terrain ainsi que les conseils pour l'expédition de matériel vers les laboratoires de diagnostic.

International audience

In order to improve the formulation of diets fed to reared Penaeus vannamei, the effects of soya bean and fish meals on the growth, survival, and the characteristics of the hepatopancreas and digestive enzymes of the species were studied. Four soya bean meal concentrations (0, 5, 15, 40%), four fish meal concentrations (0, 5, 15, 30%), two forms of soya bean meal and three fish meals of different geographical origin were tested. Experimental conditions were as follows: ten individuals were placed in each tank (0.5 m2 ) and two tanks were subjected to each treatment. Food was given twice a day (08-09.00 h and 19.00 h) at 10% of the initial weight each day. For biochemical analyses, nine individuals per treatment were used for the determination of the hepatosomatic ratio, proteins, proteases, amylases and trypsin. The results show that a high level of soya bean or fish meals in the diet strongly depresses growth without any apparent effect on the digestive enzymes or the hepatopancreas parameters. No effect of soya bean meal type or geographical origin of the fish meal was detected. The results suggest that the incorporation of both soya bean and fish meals in the diet should be restricted to low concentrations and only with the aim of diversifying the protein sources., Afin d'améliorer la formulation des aliments composés destinés à la croissance de Penaeus vannamei, nous avons étudié l'effet de l'incorporation de farine de soja et de farine de poisson sur la croissance, la survie, les caractéristiques de l'hépatopancréas et les enzymes de cette espèce. Quatre concentrations de farine de soja (5, 10, 20, 40%), quatre concentrations de farine de poisson (0, 5, 15, 30%) deux formes de farine de soja et trois farines de poissons différentes suivant leur origine géographique ont été successivement testées. La nourriture (10% du poids initial) a été distribuée deux fois par jour (8-9 h et 19 h). Les rapports hépatosomatiques, les protéines, les protéases, les amylases et la trypsine ont été déterminés sur neuf individus par traitement. Les résultats montrent qu'une forte incorporation de farine de soja ou de farine de poisson a pour effet de diminuer la croissance des animaux. Cette diminution est liée à une baisse de l'ingestibilité des aliments. Les enzymes digestives ne sont pas affectées. Les résultats montrent par ailleurs que l'origine géographique d'une source de poisson et le traitement subi par la farine de soja et la farine de poisson d'autre part, n'affectent pas les performances zootechniques et les enzymes digestives. L'ensemble des résultats permet de conclure que l'incorporation de soja ou de farine de poisson dans l'aliment doit être réalisée à faible taux, et ce, uniquement dans le but de diversifier les sources de protéines.

This study on the larval rearing of Penaeidae shows that during the zoeal stages artificial diets containing animal and plant materials as well as yeasts may be used instead of live unicellular algae. Optimal feeding rates were determined for Penaeus indicus . The prawn larvae showed the best survival and growth rates when fed at a rate of 500 mg per day per 200-l tank with five feeds a day rather than two. Zoeal survival in Penaeus indicus and Penaeus vannamei is the same when they are fed either the artificial diet or live algae, though growth is better in the case of the algal diet. Zoeal survival in Penaeus monodon fed the artificial diet was as high as 85%. However, delays were recorded when compared to the duration of the zoeal stage usually obtained using live algae.

Until recently, mollusc production in French Polynesia was based on fishing to satisfy local consumption of edible bivalves (mainly the oyster Saccostrea cuccullata ) and to export pearl-oyster shells. Because of parasite problems in the local oyster population, a mollusc culture program was initiated. Hatchery techniques were developed for introduced species of edible bivalves, Saccostrea echinata and Perna viridis , and cultivation methods were developed in specially fitted-up areas. Traditional shell production concerning the pearl oyster Pinctada margaritifera was recently reorganized to produce black cultured pearls, causing an increased demand for young, implantable pearl oysters. Hatchery spat production proved to be unsuccessful, and techniques of collection and cultivation in lagoons were set up to supply the pearl-oyster farming industry, and to address the problems of depleted natural stock.

In this study, Penaeus vannamei and Penaeus stylirostris were fed four diets during the ovarian maturation period under controlled conditions. One diet was composed of a variety of natural animal food (molluscs and fish). Three other diets included pellets (88% dry weight) and natural animal food (12% dry weight); two of these three artificial diets contained broken squid or shrimps. For Penaeus vannamei , the best results were obtained with the natural food and with two diets including 88% pellets (spawning index: 2.8 per female per month). For Penaeus stylirostris , two diets composed of 88% pellets were the best (spawning index reached 4.7 per female per month). The results indicate that the variety of natural food which is reported to induce ovarian maturation of penaeid prawns in captivity can be partly replaced by adequately formulated pellets.

The growth response to supplementation of mixed diets with a protein extracted from frozen squid (squid protein fraction: SPF) was tested at levels of 1.5, 3.0, 6.0 and 16.0% in the diet in four species of shrimp: Penaeus stylirostris, P. vannamei, P. monodon and P. indicus. In P. stylirostris and P. vannamei, growth rates were significantly improved by SPF even at the lowest level of supplementation. Improvement was obtained only with 6 and 16 percent in P. monodon, while no significant response was observed in P. indicus. The growth promoting effect of SPF at 16% of the diet could be explained by its nutritional value, particularly by its amino acid content, although all diets were supposed to be well balanced in all known nutrients. However, at lower levels the results obtained seemed to be due to the unknown growth factor (UGF) already mentioned in previous reports.