Anti-Bacillus megaterium activity was measured in unfractionated plasma withdrawn from three common US East Coast bivalve molluscs: an oyster Crassostrea virginica and the mussels Geukensia demissa and Mytilus edulis. The activities of the plasma samples from these bivalves were also measured against a C. virginica pathogen Perkinsus marinus. Strong anti-B. megaterium activity was measured in plasma from C. virginica and M. edulis, but was not detected in G. demissa. Bactericidal activity was found in hemocyte extracts from all bivalves in this study, suggesting a cellular origin of cytotoxic humoral factors. Peptides (< 10 kDa) were separated from the plasma samples by ultrafiltration; weak antibacterial peptide activity was quantified in C. virginica peptides, but not in peptides from the mussels. In the case of P. marinus, plasma from M. edulis or G. demissa was boldly cidal as compared to plasma from C. virginica. This difference in activity probably reflects the low pathogenicity of this oyster parasite for the mussel species tested. In summary, the bactericidal activity of plasma proteins from these bivalves showed considerable interspecies variation and did not necessarily correlate directly with antiprotistan activity. When present, antibacterial and antiprotistan activities seemed to be associated with plasma proteins rather than < 10-kDa plasma peptides, with the possible exception of C. virginica anti-B. megaterium activity and the occasionally expressed anti-P. marinus activity of M. edulis peptides. The precise identity of the plasma protein(s) responsible for the antimicrobial activities measured have yet to be determined, but it is likely that agents other than, or in addition to, lysozyme play significant roles in the process.

Among the different stages in the protozoan Perkinsus marinus life cycle, the trophozoite stage is known to be the most infective stage in marine molluscs. To develop a direct method for in vitro studies of P. marinus proliferation under various environmental conditions, monoclonal antibodies (MAbs) specific for this pathogen were produced. Inbred strains of mice BALB/c were immunised with a trophozoite prepared from cloned isolate Perkinsus 1 cultured on JLODRP1 medium. The mouse polyclonal antiserum showing the highest antibody titre for pathogen trophozoites was chosen for lymphocyte hybridisation. The screening of positive hybridoma by indirect enzyme-linked immunosorbent assay (ELISA) revealed two probes (17B2D5 and 19G3H6) detecting P. marinus trophozoites and their protein lysates but also trophozoites from P. atlanticus. These MAbs belonged to the immunoglobulin IgG1 subclass. Their binding specificity was investigated by ELISA and fluorescein (FITC) methods. Both immunoreacted with trophozoite stage as well as hypnospore and zoospore stages of P. marinus, but neither with hemolymph and tissues of oysters, Crassostrea gigas and C. virginica, nor with parasites, Bonamia ostreae and Marteilia refringens. A competitive ELISA method was developed, using 17B2D5 MAb to evaluate parasite multiplication in culture media and to estimate the parasite burdens from infected oysters. This method is sensitive enough to detect 103 trophozoites in 50 μL assay sample.

A tracer (51Cr-EDTA) study was undertaken with juvenile (20 g) freshwater rainbow trout, Oncorhynchus mykiss, using an experimental design that minimized stress effects during feeding and drinking trials. A calculation procedure was developed, where feed intake (pellet number), tracer intake (mL), water in stomach contents (g) and drinking rate (mL·kg–1·h–1) are essential to discriminate between the major stomach water sources prandially and postprandially: water bound in food; initial water absorption of pellets; prandial water intake; postprandial water intake and endogenous stomach secretion. We put forward the hypothesis that intake of dry food with a minor water content (10 %) may impose a demand for water to moisture the feed up to the level in natural feed (75 %) as preparation for gastric emptying, whereafter food is ready to pass from the stomach through the pyloric sphincter. Moisture content of pellets increased from 9.4 to 24.9 % in the pre-meal period. The pellets were ingested with 4.0 to 19.3 μL water per pellet, reflecting high inter-individual variation. Prandially moisture content rose to 52 % and further increased to 56 % in the delay period. Moisture content was ca. 65 %, when pellets began to disintegrate and move through the sphincter in accordance with the hypothesis. Stomach secretion contributed 34–44 % of the stomach water and ingested water 25–35 %. The sampling and calculation procedure gave convincing evidence for the detailed stomach water budget and this individual approach can be very useful in comparisons of artificial and natural diets.

Sturgeon production in Western Europe originating from aquaculture in 1999 was approximately 1300 t revealing an increasing trend. Three species represent 95 % of the annual production: white sturgeon (Acipenser transmontanus) 43 %, Siberian sturgeon (Acipenser baerii) 34 %, and Adriatic sturgeon (Acipenser naccarii) 18 %. The remainder is provided by various species including hybrids. The main countries in decreasing order of production are Italy, France, Spain, Germany and Poland. Fish are fed commercial formulated diet. The most significant changes in the sturgeon industry during recent years have been in the ownership of farms, in the emergence of the pond as a production system, and in the increasing caviar production from farmed sturgeon. In 1999, the production of farmed caviar from France and Italy, originating from Siberian and white sturgeon, respectively was close to 6 t. The number of active sturgeon farms in Western Europe is estimated to be approximately thirty, half of which are hatcheries. This paper presents different strategies and management approaches in sturgeon production and caviar processing. The potential caviar market and its dynamics are assessed and likely changes are discussed. Finally, some of the scientific investigations needed to improve and support this development are highlighted. Five different fields are distinguished: biological reserve, genetics, reproduction, farming, and quality of end products.

Culture of sturgeons in Russia began in the second half of the 19th century. During the first part of the 20th century, a significant research effort was devoted to the control of reproduction and the rearing of larvae mostly for stock enhancement purpose in rivers. Large-scale construction of hatcheries began in the 1950s after the damming of rivers, and by the 1980s over 130 million 1–3-g juveniles per year were being produced from wild broodstock. Presently, the production is 100 million juveniles. Emphasis is now on optimising stocking results through consideration of fish-specific factors (e.g. behaviour, fitness, size, balance between species) as well as environmental variables (food availability, release sites, salinity, precipitation regime). Food fish production of sturgeon (market size is 1.5–2.0 kg is just beginning using captive broodstock and new growing technologies. In 2000, farm production was about 1650 t, which was higher than sturgeon landing from wild fisheries (1500 t declared in 2000).

Cinq mille larves de poisson-spatule Polyodon spathula agées de 3–4 jours, en provenance du Missouri aux États-Unis, ont été introduites dans l’ex-URSS, en 1974 dans le cadre des accords de coopération scientifique entre les deux pays. Cette première tentative n’a été que partiellement réussie ; seuls quelques survivants ont atteint 600–900 g après 2 ans puis la maturité sexuelle et se sont reproduits en 1984 et 1986. L’élevage de cette espèce étant apparu possible, de nouvelles introductions ont eu lieu, l’une en 1976, qui fut sans succès et une autre en 1977, réparties dans deux écloseries (Goreachi Cluch et Krasnodar-Ikreanoe). En 1978, une centaine des spécimens de Goreachi Cluch ont été exportés en Moldavie et élevés en polyculture dans plusieurs piscicultures où la reproduction de trois femelles a été obtenue en 1988 et 1989. Des juvéniles issus de ces reproductions ont été exportés en URSS (Ikreanoe) et en Roumanie et Hongrie. Par ailleurs, la station de recherches de Nucet en Roumanie a importé des larves de poisson-spatule des États-Unis en 1992, 1993 et 1994 (environ 2000 larves à chaque introduction). Dans ces différents pays, des recherches ont été conduites sur cette espèce. Actuellement, la production commerciale a débuté en Russie et Moldavie pour la chair, et il a été montré, dans le cadre d’un projet CE Copernicus, qu’il était possible de produire du caviar. P. spathula peut venir en complément ou en substitution partielle de carpes, en polyculture et a une valeur commerciale plus élevée. Le problème est que la seconde génération présente en Russie, Moldavie, Roumanie, et peut être en Hongrie, est dérivée d’un nombre limité de parents, avec des risques de perte de variabilité génétique.

Paddlefish are endemic to most rivers and tributaries of the Mississippi basin and are found in 22 states of the United States. In 1989, US Fish and Wildlife Service (USFWS) listed paddlefish as a category 2 species because data were lacking on its population status. In 1992, USFWS added paddlefish to the list of Appendix II of the Convention on International trade in Endangered Species of Wild Fauna and Flora (CITES) primarily due to concerns about illegal poaching in the international caviar trade. Therefore, paddlefish aquaculture will provide alternative fish sources for the marketplace in the era of strict federal and state regulations on wild populations. Aquaculture of paddlefish is in a research and developmental phase. Most broodstock are obtained from wild sources, though some mature fish have been developed in captivity. Artificial propagation techniques are resulting in > 80 % egg fertility. Larval paddlefish are initially raised in organically fertilized, zooplankton-rich (i.e. Daphnia sp.) ponds, and then trained on extruded trout/salmon diets until the juvenile fish are > 30 cm in total length. Tank culture is also an alternative for raising juvenile fish. Juvenile paddlefish, a filter feeder that requires zooplankton as its primary food, are being grown in reservoirs and in polyculture with channel catfish (Ictalurus punctatus) in Kentucky, Indiana, Missouri and Alabama. Production yields are 200–400 kg·ha–1 in polyculture and in reservoirs ranching resulted in 55–175 kg·ha–1. Reservoir ranching is ideal for caviar production; whereas, paddlefish (1.5 to 4.0 kg) cultured with catfish is for meat production. A system to produce all-female progeny through artificial propagation with sex-inverted, gynogenetic broodstock and attempting to develop optimal cryopreservation techniques for the milt of these unique broodstock is currently being tested. Value-added products such as hot and cold smoked paddlefish are the major effort being developed for the marketplace. Consumer acceptability of value-added products from paddlefish has been better than channel catfish.