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.

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.

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.

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 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.

Human growth hormone like peptides were present in Penaeus indicus as two molecular forms: one with a molecular weight about 25 kDa which is similar to that of the vertebrate growth hormone and a smaller form of 2 kDa. Quantitative variations of hGH-like peptides in different larval stages of three species of Penaeids (Penaeus vannamei, P. stylirostris, P. indicus) suggest a possible involvement of hGH-like peptides in the development. Human growth hormone (hGH) supplementation in the diet of Penaeus vannamei larvae seems to have a positive effect on the size and on the quality of the animals estimated by their resistance to salinity stress.

Adenylate Energy Charge (AEC) values of Crassostrea gigas (9 and 18 months old) cultured in ponds in Marennes-Oléron Bay (Atlantic coast, France) are reported. Two ponds were loaded with two different initial oyster biomasses in order to obtain different food conditions. The growth of oysters was different in the two ponds which corroborated the effectiveness of attaining different food conditions. AEC level was different depending on the pond and was therefore related to food availability per unit oyster biomass. Well-fed oysters exhibited greater AEC values than poorly-fed oysters, throughout the study. Information on nutritional situations for wild or cultured populations can therefore be obtained by AEC. In each pond, the seasonal AEC variations were similar for both age-groups and were characterized by a minimum value in summer and a maximum value in winter. The influence of reproduction on these variations cannot be ruled out as for all the batches maturation processes were evidenced. Research will be done on a temperature effect to try to distinguish these seasonal variations. A strong correlation between adenylate energy charge (AEC) and guanylate energy charge (GEC) was demonstrated; it was similar for both ponds. The levels of nucleotide concentration were relatively stable during the survey except in September and December for oysters in the low density pond. Among nucleotides, adenylate pool represented the major part (80%). A decrease in the total concentration of adenylates was observed in August. The best growth correlated with the lowest adenylate percentage and a better GTP/ATP ratio, suggesting that this ratio could be a useful index for growth.