This study concerns the dynamics and management of the hairtail fishery (Trichiurus haumela) in the East China Sea. Virtual population analysis was used to assess the historical pattern of stock size and an age-structured production model was developed to simulate the historical and future changes of catch and stock of hairtail under different fishing strategies. The results show that the stock of hairtail has been declining in general since the beginning of the 1960s. In 1981, it was 275.103 metric tons, overfished but not very seriously. Subsequent management measures brought some positive effects to stock and catches and slowed down the decline, but they cannot change the status of overfishing of the stock. The current fishing regime will inevitably lead to more severe depletion of the stock and also decrease the catch in the end. To prevent further deterioration of the stock and maintain catches, any further expansion of fishing effort must be stopped. Alternatively, a longer closed season should be introduced or the age at first capture should be raised.

An ultrasonic tagging program for tuna was conducted in 1988 and 1989 within the Regional TunaProject of the Indian Ocean Commission. Three yellowfin and six skipjack tuna were tagged withtemperature or depth sensitive transmitters in the North-western part of the Mozambique Channel(12°S-44°E) around Anjouan island (Comoros Archipelago) where several fish aggregating devices(FADs) were previously moored. The horizontal and vertical movements observed during 8 tracks (3yellowfin and 5 skipjack tuna) whose duration was between 3 and 24 hours, are analysed in terms ofswimming depth, temperature encountered and position of the tracked tuna relative to the FAD orcoast line. Comparison between recorded depth of tracked tuna and echo sounded fish indicatedtracked tuna were schooling.Two of the 3 tagged yellowfin tuna displayed a behaviour of association with FADs. The optimaldistance between 2 anchored FADs, to avoid adverse interference in the attraction of tuna, is estimatedas 11 nautical miles. A very small percentage of time is spent by yellowfin tuna near the surface. Themean swimming depths encountered in the daytime by yellowfin tuna are much deeper (70-110 m)than they are at night (40-70 m). The relative homogeneity in the observed behaviour of yellowfintuna and the fair general agreement with previous results obtained in the Pacific Ocean, should allowapplication of ultrasonic tagging results to fishing and prospecting purposes in the future.The movements of the 5 tracked skipjack tuna do not indicate a behavioural association withFADs, and do not present marked differences between the swimming depths encountered by nightand during the daytime. The high variability observed in the behaviour of the different trackedskipjack tuna, and the bad agreement with previous results obtained in the Atlantic and in the PacificOceans have to be emphasized. A high turnover of the skipjack tuna concentrated around FADs dueto an intense and pelmanent migratory flow through the area of Comoros Islands could partly explainthese apparent discrepancies.

Cold shocks and hydrostatic pressure shocks, respectively, were applied for the induction of bothtriploidy and tetraploidy in the common carp. Cold shocks of 0-2 °C, lasting 40 minutes and starting 2–5 minutes after the activation of gametes and hydrostatic pressure shocks with 1-3-5 minute exposures at 49.03–56.88 MPa (i. e. 7 116-8 225 psi – pounds per square inch), starting 5 minutes after the activation of gametes gave the best results. The tetraploidy induction by cold shocks or hydrostatic pressure shocks resulted either in negligible (1.54%), or in zero yields, respectively. The applicability of particular types of ploidy manipulation and the standardization of shock initiation were discussed.

A method to assist the reading of calcified structures with digital images is proposed. An a priori growth pattern is introduced in the image processing to take into account both the variability of the ring size and the non-linearity of their growth. The introduction of biological knowledge is performed within a demodulation processing using the reciprocal growth function. The ring number is estimated by spectral analysis. The constraints introduced by the growth model are weak since they are restricted to the definition of L0, in the case of an exponential model, or of L∞ in the case of a Von Bertalanffy model. When applied to larval Dover sole otoliths (Solea solea) results close to the expert's are obtained. In the case of saithe otoliths (Pollachius virens) the mean discrepancy with the expert's, i.e. 1.5 years, can be assigned to the lack of processing of marginal rings and to the inadequacy of the morphogenesis model on which the processing algorithm is based. This approach which is only founded on the dynamic features of the "biological signal", will have to be completed in future work with the introduction of structural information.

Hoplosterum littorale (Hancock, 1828) shows a marked circadian rhythm of food demand. Feeding activity is mainly nocturnal, with two peaks, and is synchronized with the diel light cycle. We tested the effect of infradian (period >28 h) light/dark cycles on this rhythm in fish with demand-feeders: fish subjected to a 13.5 L/22.5 D light/dark cycle for 8 days and a 25.5 L/10.5 D cycle for a further 8 days showed a strictly nocturnal feeding activity, a response that only passively reflected the cyclic alternation of light and dark.

L'étude du déterminisme du pré-recrutement de Pecten maximus (L.) en baie de Saint-Brieuc a été réalisée par captage de post-larves sur des collecteurs artificiels, et par échantillonnage benthique des juvéniles de coquille Saint-Jacques et de la macrofaune épigée et endogée superficielle. Les techniques mises en œuvres fournissent des estimations fiables de l'abondance des pré-recrues et de la force d'une classe d'âge, dès les quatre premiers mois de vie benthique. L'abondance d'une classe d'âge pré-recrutée est déterminée par la fécondité des adultes, l'hydrodynamisme (courants; turbulence à l'interface eau-sédiment), la nature sédimentaire des fonds (degré d'envasement; substrats disponibles), la température hivernale des eaux, l'intensité des interactions biotiques (compétition; prédation), et par les facteurs régulant la croissance du groupe d'âge 0 (la survie lors du 1er hiver est fonction de la taille des juvéniles). Les trois années d'étude montrent l'existence d'une forte variabilité spatio-temporelle intra- et interannuelle des mécanismes régulant l'abondance du pré-recrutement de Pecten maximus.

Rainbow trout were fed two experimental diets differed in lipid content by replacement of crudestarch (lipid-poor diet : 4.2% lipid or lipid or lipid-rich diet : 14.8% lipid) supplemented or not with antibiotics (a combination Flumequine + Gentamycin, 1:4). The apparent digestibility of dry matter, crude protein, lipid, carbohydrate and total energy were measured. Addition of lipid by replacement of crude starch in the fish diet in the absence of antibiotics enhanced significantly (p < 0.01) the apparent digestibility of dry matter, crude protein, carbohydrate and total energy, but did not influence those of lipid. Antibiotics supplementation of the lipid-poor diet (consequently with a high level of carbohydrate) enhanced significantly (p < 0.01) the apparent digestibility of dry matter, crude protein, lipid, and total energy, but not those of carbohydrate. On the other hand the antibiotics-treated lipid-rich diet (consequentlywith a low level of carbohydrate) showed a higher (p < 0.01) digestibility for dry matter, lipid, carbohydrate and total energy, but not for crude protein. The stimulatory effect of antibiotics on nutrient digestibility is discussed.

Il est bien connu des pêcheurs que les monts sous-marins, nombreux dans l'Atlantique tropical est, concentrent parfois de fortes biomasses de thons. Cette association thons et monts sous-marins n'a paradoxalement fait l'objet d'aucun programme de recherches. Le présent article fait un bilan des captures de thons réalisées par les flottilles thonières internationales sur les monts sous-marins connus dans l'Atlantique tropical est durant les années récentes (période 1980 à 1987). La prise annuelle de thons sur certains monts sous-marins peut atteindre plusieurs milliers de tonnes. Les statistiques de pêche thonière montrent que certains monts sous-marins sont riches en thons, alors que d'autres semblent pauvres en permanence, bien qu'ils soient situés dans des zones prospectées par les pêcheurs. Les particularités biologiques de ce type de pêche sont analysées : les captures sont en général plurispécifiques; albacores (Thunnus albacares), listaos (Katsuwonus pelamis) et patudos (Parathunnus obesus) sont pêchés en proportions voisines avec des individus de tailles relativement petites en comparaison des zones voisines. Des hypothèses sont développées sur les causes et sur la dynamique de l'agrégation des thons autour de ces hauts-fonds en utilisant les statistiques de pêche journalières et les résultats de marquages classiques et par marques émettrices réalisés sur un mont sous-marin. Les perspectives de recherches sur l'association sous-marins et thons et sur l'exploitation rationnelle de ces micro-structures sont discutées. Les positions et les profondeurs des monts sous-marins étant actuellement facilement repérées grâce aux satellites à radar altimétrique, la localisation systématique de ces structures est possible et revêt pour les pêcheurs un intérêt potentiel évident pour réduire les temps de prospections des thoniers.

Heat shocks effective for the production of triploid brown trout (Salmo trutta) were optimized: 28 °C shocks lasting 10 to 15 minutes and applied 5 minutes after fertilization induce very high rates of triploidy (close to 100%) without causing much mortality; they can therefore be proposed for mass production of triploid brown trout. Female homogamety in that species is also demonstrated from analysis of gynogenetic progenies and progenies of sex-inverted females. Although the efficiency of masculinizing hormonal treatments requires further improvement, production of all-female sterile populations is now possible in this species promising for European sea-farming.

Une description chronologique du développement embryonnaire et larvaire du poisson-chat africain Heterobranchus longifilis (Clariidae) a été effectuée jusqu'à l'âge de 17 jours. Une comparaison avec le développement ontogénique d'un autre Clariidae, Clarias gariepinus, a été faite. Les deux espèces présentent de grandes similitudes dans leur développement et diffèrent surtout par la genèse de la nageoire dorsale, unique et allongée chez C. gariepinus, plus courte et suivie d'une grande nageoire adipeuse chez H. longifilis. Les limites inférieure et supérieure de tolérance thermique des œufs de H. longifilis ont été déterminées. Elles se situent entre 22 et 24 °C et entre 34 et 35 °C respectivement, aucune éclosion n'étant obtenue à 21 °C comme à 36 °C. L'optimum thermique pour lequel les pourcentages d'éclosion sont les plus élevés se situe entre 25 et 29 °C. Cet intervalle de température est donc recommandé pour l'incubation des œufs dans la pratique piscicole. La durée de l'incubation varie avec la température. L'éclosion des œufs se situe entre 26 à 33 heures et 14 à 18 heures après la fécondation pour des températures d'incubation de 25 et 33 °C respectivement.

Individual (mass) selection for shell height was carried out in the Chilean oyster, Ostrea chilensis. The selection was based on the shell height of oysters, 30 months old, which came from the natural population of the Quempillen River Estuary (Southern Chile). Divergent selection was applied, three selected groups were chosen to mass spawn (high, mean selected, and low). Offspring from the mean selected and low groups were obtained. A statistically significant difference (p < 0.05) was detected in shell height at 30 months between the offspring of the mean selected and low selected group, suggesting the presence of additive gene effects for growth rate. The realized heritability estimate (h2 = 0.34 ± 0.12) for a decrease in the shell height, indicates that selective breeding on this trait can be effective in Ostrea chilensis.

The growth response of diploid (2n) and thermally-induced triploid (3n) coho salmon to injected recombinant porcine somatotropin was examined over a 10 week period. All treatments were under-taken using replicate groups of 25 animals per group. Control 2n and 3n replicate groups grew at identical rates throughout the period of study, although 3n fish exhibited lower condition factors. Recombinant poreine somatotropin treated 2n and 3n fish responded positively to therapy and, by week 4 of the trial, expressed significantly greater increases in both weight and length (p < 0.01) when compared to controls. At the end of the study period, soinatotropin treated animals had gained approximately twice the amount of weight of controls. Food conversion efficiencies were greater in treated salmon, regardless of ploidy state. This relationship also extended to weight and length specific growth rates. The economic benefits of commercial application of recombinant porcine somatotropin therapy to triploid Pacific salmon culture are discussed.

Development of a broodstock of Arctic charr was undertaken in experimental tanks supplied with water pumped from Lake Léman (Geneva) at a depth of 36 metres. Spawners were subjected todifferent thermal regimes to determine the effects of temperature on spawning time and gameteviability. In the tanks, the ovulation occurred spontaneously at the same time as the wild fish in the lake. The timing of ovulation was slowed down at 8 °C and above. At 11 °C, ovulation was inhibited. When the water temperature of the rearing tanks was higher than 5 °C for several weeks prior to spawning, the quality of eggs produced by reared females was poorer than those of wild fish because the process of overripening was very rapid above 5 °C. Provided that spawners were reared at 5 °C and examined twice a week to detect ovulation, 80 to 90 percent survival to the eyed stage could be expected for eggs of reared females. The fertilization rate of eggs produced by spawners transferred from 8 to 5 °C in December was high (78%). When the transfer occurred in January, the viability of ova tended to decrease (63%).

The final phase of spawning migration of eight adult male Atlantic salmon, Sulnio solar L., was analysed by radio-tracking in relation to sea age and size in a spawning tributary of the Kiver Sélune. Four grilse and four multi sea-winter fish, one of which as a previous spawner, were radio-tagged and released. Their fork length ranged from 602 to 882 mm. The daily movement in the first two days alier release and the furthest upstream distance recorded from the trap during the study period were independent of fish length. Maximum amplitude of movement observed over the entire study period was inversely correlated with length. Daily movement decreased in all males during the spawning period and was negatively correlated with the size of fish. Surviving males remained in the vicinity of the spawning grounds after spawning. It was concluded that the length of male seemed to influence its behaviour in the last phase of the spawning migration, enabling a much more successful participation of the larger males in spawning.

L'influence de la période (jour, nuit) et de la fréquence d'alimentation (1 à 4 repas fractionnés ou alimentation continue) a été étudiée sur la croissance et l'efficacité alimentaire chez un silure africain (Heterobranchus longifilis). L'expérience, d'une durée de 56 jours, a été réalisée sur des poissons de 74 g de poids moyen initial. Avec un même taux de rationnement (3 % du poids vif/jour), les poissons nourris la nuit ont une croissance significativement plus élevée que ceux nourris le jour et un nourrissage sur l'ensemble du nycthémère n'apporte pas d'amélioration. Les performances de croissance tendent à augmenter avec l'accroissement de la fréquence d'alimentation quelle que soit la période de nourrissage, et les croissances sont significativement plus élevées avec une alimentation en continu, de 2,36 à 2,64 g.j-1. L'indice de consommation est significativement plus faible pour les poissons nourris en continu que pour ceux recevant une alimentation par repas. Le rapport hépatosomatique est significativement plus élevé chez les poissons nourris la nuit que pour ceux nourris le jour. Par contre, les dépôts de graisse dans la cavité abdominale sont plus importants chez les individus nourris de jour et augmentent avec la fréquence des repas. L'analyse des compositions corporelles globales confirme ces observations. En pratique, il est recommandé de nourrir ce poisson en continu durant la nuit, ce mode d'alimentation conduisant aux meilleures performances de croissance.

The results of preliminary experiments in the development of a hatchery brood stock of whitefish of Lake Geneva, Coregonus shinzi palea Cuv. and Val. (lavaretus), are described. Factors likely to influence the date of spawning and the quality of eggs were studied by reference to the performance of wild spawners from the Lake Geneva. Fish were reared in tanks and the ovulation of females occurred spontaneously at the same spawning time as in wild spawners from the lake. Reared females have produced 30 000 eggs/kg against 45 000 in wild fish. The survival rate of a domestic egg was about 10% less than that of wild females. Since the overripening of the ova was rapid it was necessary to check the ripe females twice a week. The exposure of fish to long days in autumn delayed spawning by two months and permitted the synchronization of hatching under optimal conditions of growth. The ovulations were spread over a period of 3 months when the fish were subjected to long days until spawning. In contrast, termination of the long day regime in December induced a synchronization of the ovulations over just one month.

La notion de qualité des postlarves de crevettes pénéides, qui sous-entend un potentiel de survie, est un paramétre resté longtemps subjectif. Les critères zootechniques et les observations visuelles ne sont pas des paramètres suffisants pour apprécier la condition physiologique des postlarves à la sortie de l'écloserie. La résistance aux chocs de salinité est un critère représentatif de l'état des postlarves. Cette étude a pour but de présenter un modèle de régression non linéaire à deux variables (taille, salinité) de la résistance des postlarves Penaeus vannamei à des chocs de salinité. Entre le 2e et le 20e jour après la métamorphose 5 chocs de salinité. (20, 15, 10, 5 et 2 ‰) sont testés chaque jour, avec respectivement 50 postlarves par salinité. Le taux de survie est enregistré après 2 heures. Parallèlement, la croissance des postlarves en élevage est étudiée par la mesure quotidienne de 30 animaux. La tolérance à la salinité des postlarves P. vannamei augmente avec la taille qui s'accroit d'une façon linéaire.

This paper presents a summary of information on reproduction biology in the scallop, Pecten maximus, which is required for the successful reseeding and intensive aquaculture programs developed in France since 1982. Data are presented on the following subjects: environmental factors that sustain gametogenic activity and the time of year this activity occurs; biochemical changes that are associated with gametogenesis; the consistency of egg quality; and development of a simple test to predict egg quality.

The effects of dietary protein level and water salinity on growth rates, feed utilization and body composition of mullet Liza ramada (synonymous of Mugil capito Cuvier, 1829) fry were investigated. Four isocaloric (18.8 kJ GE/g) diets containing 25, 30, 35 and 40% protein levels were prepared. Each diet was fed to duplicate groups of L. ramada fry (0.13 g mean weight and 24.6 mm mean length) reared at 4 different salinities (0, 12, 24 and 36‰) to satiation, twice a day for 70 days. The fish which were reared at 0 salinity exhibited poor growth and feed conversion concomitant with high mortality rates. At salinities in the range of 12–24‰, the best growth and feed conversion were achieved at 40 and 35%, dietary protein levels, respectively. At full-strength sea water (36‰), optimum fish performance was achieved at 30% dietary protein. At all salinities, protein efficiency ratio (PER) and protein production value (PPV) were negatively correlated with dietary protein level. With the exception of body ash, carcass composition Was significantly affected by dictary treatments. At all salinity levels, body water and protein were positively correlated to dietary protein, while carcass lipid showed a negative correlation. Body ash was higher in the fresh water groups than in those reared in brackish and sea water.

The pattern of ammonia excretion was examined in the Siberian sturgeon, Acipenser baeri, during starvation. For different weight groups (60 g to 2 kg), this excretion decreased rapidly to reach a constant level of 32 mg NH4-N.kg-1.day-1 after 8 days of fast. This minimum is an estimation of the Endogenous Nitrogen Excretion (ENE). No diurnal pattern was observed in the ammonia excretion or oxygen consumption (28.6 ± 3.2 mg O2.kg-1.h-1, mean ± sd) of fasted fish. These data appear to indicate that the basal metabolism is very low in the Siberian sturgeon and that the nycthemeral cycle is only the result of exogenous nutrition.