Marine Fish Hatchery Research Articles

Rearing of Fabrea salina Henneguy (Ciliophora, Heterotrichida) with three unicellular feeds

The growth rate of the ciliate Fabrea salina was studied in batch cultures in the presence of three feeds, tested separately from each other: the Prymnesiophyceae, Isochrysis galbana obtained from pure culture, the Chlorophyceae Dunaliella salina, and the commercially available yeast Saccharomyces cerevisiae. F. salina, and D. salina were harvested below the surface from the first evaporation pond and the crystallizer pond, respectively in multi-pond salterns (Sfax, Tunisia). The highest density of Fabrea was recorded with I. galbana (26 ind ml −1). However, the greatest length (243 μm) was recorded with Fabrea fed with D. salina. The lowest density, length and biovolume values were recorded with Fabrea fed with S. cerevisiae. The ANOVA test showed that density ( F = 18 , d.f. = 57 ), length ( F = 33 , d.f. = 57 ), and biovolume ( F = 19 , d.f. = 57 ) of Fabrea fed with yeast were significantly different ( p < 0.001 ) from those when Fabrea was fed with D. salina and I. galbana. The ciliate Fabrea encountered in the Sfax saltern (Tunisia) might be a valuable food source for Tunisian marine fish hatcheries. To cite this article: W. Guermazi et al., C. R. Biologies 331 (2008).

The Fatty Acid Profile of the Marine Cephalopod Loligo vulgaris

Squids and their by-products are widely used as pre-spawning feeds in marine fish hatcheries. Therefore, we studied the fatty acid composition of mantle tissue, arms, fins, and gonads of the marine cephalopod, Loligo vulgaris, from a broodstock nutrition point of view. Docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids represented nearly half (&gt;45%) of the total fatty acids, with DHA the most abundant fatty acid in all investigated tissues. The fatty acid profile of the gonads differed significantly from those of the mantle, arms, and fins; EPA was present in a sig- nificantly higher proportion (20%), perhaps indicating its important role in reproduction. Results indicate that Loligo vulgaris and its by-products can be an important nutritional component of broodstock feeds, serving as a major source of DHA and EPA.

Quantitative study, identification and antibiotics sensitivity of someVibrionaceae associated to a marine fish hatchery

This study characterises the bacteria associated with a marine hatchery in Tunisian coastal marine waters. Presumptive vibrios (TCBS agar) and heterotrophic aerobic microflora (CFU) were studied at different stages within the hatchery: seawater, batches of algal cultures, rotifers andArtemia culture tanks. The bacterial strains were isolated on TCBS Agar plates and described using different bacteriological tests (standardised micromethods “API 20 E Strips”, exoenzymes production, growth at different temperatures, pH and salinity, vibriostatic agent O/129 and antibiotics susceptibility). Two dominant genera of bacteria were found (Vibrio andAeromonas) associated with some strains of thePseudomonadaceae family.Vibrio alginolyticus was the dominant bacteria (75% of total isolates) found in rotifers (Brachionus plicatilis) andArtemia cultures (Artemia salina). In larvae rearing tanks, an increase ofVibrionaceae was noted after larvae were fed withArtemia. Most of the studied bacteria used the skin mucus ofSparus aurata larvae as their sole source of carbon. All theV. alginolyticus strains were β-haemolytic, hydrolyse the DNA and were susceptible to several tested antibiotics.

Activity of bronopol (Pyceze®) against bacteria cultured from eggs of halibut, Hippoglossus hippoglossus and cod, Gadus morhua

Bronopol (2-bromo-2-nitro-1,3 propanediol) is a broad spectrum bactericide that is the active ingredient of Pyceze®. To assess the potential of Pyceze® for use in marine fish hatcheries we have determined the Minimum Inhibitory Concentration (MIC) of bronopol for 13 bacteria isolated from eggs of halibut ( Hippoglossus hippoglossus) and Atlantic cod ( Gadus morhua), and Escherichia coli, Staphylococcus aureus and Vibrio anguillarum as control bacteria. Six Vibrio and Moritella spp. had MIC ranging from 1–2 to 8 μg ml − 1 bronopol (mean MIC approximately 3 μg ml − 1 ), but other bacteria tested ( Tenacibacter ovolyticus, Pseudomonas sp., Pseudoalteromonas spp., Colwellia sp., Photobacterium phosphoreum and a Cytophaga/ Flexibacter sp.) were more resistant with MIC in the range 8–16 to 32–64 (mean MIC approximately 25 μg ml − 1 ). E. coli and S. aureus both had MIC of 32 μg ml − 1 . Although the MIC of bronopol for T. ovolyticus was 16–32 μg ml − 1 , a concentration of 100 μg ml − 1 bronopol had no detectable killing effect on this organism within 1 h but at 200 μg ml − 1 bronopol 90% of T. ovolyticus were killed within 30 min and > 99.99% within 2 h.

Microbiology of summer flounder Paralichthys dentatus fingerling production at a marine fish hatchery

The microbiology of summer flounder, Paralichthys dentatus, fingerling production was monitored over the course of 10 production cycles during 1996–1999 at a commercial marine fish hatchery. Samples of the rearing water, fish larvae and live feed were analyzed to quantify the total heterotrophic bacteria (marine agar) and total presumptive vibrios. Selected bacterial isolates were characterized to the group or species level. The tank water was compared between two larviculture methods to see if greenwater densities or the timing of fish movements could affect the tank microbiology. The extensive use of phytoplankton as rotifer enrichment and as greenwater reduced the incidence of vibrios as a percentage of total heterotrophs in the rotifers and water. Rinsed enriched Artemia had high levels of vibrios, and the fish larvae experienced increased mortality during the period of Artemia feeding although known bacterial fish pathogens were not detected at significant levels. The microbiota of the rearing water and fish intestine were similar to that of the live feed being utilized at the time of the sampling. A succession of bacterial phenotypes was observed in the rearing water and the fish intestine from day 1 to day 90 post-hatch, and the fish larvae showed evidence of the development of a stable indigenous microbiota during and after metamorphosis. Acinetobacter, Agrobacterium, Flavobacterium, Moraxella and Pseudomonas were the dominant bacterial groups in phytoplankton, rotifers and the early larval fish and tanks. However, Artemia and older larval stages and tanks showed a shift towards the microbiota with higher levels of Vibrio and Enterobacter. Bacillus was detected in juvenile fish but not in larval stages. The results provide a database for analyzing the role of the microbiota in health and disease of summer flounder and suggest that this microbiota may be amenable to probiotic type manipulations.

Larviculture of marine finfish in Europe

European larviculture techniques for commercially farmed marine finfish species are reviewed with reference to recent developments in the fields of health management, larval nutrition and system operation. Specific rearing methods and critical aspects of production are described for sea bream Sparus aurata, sea bass Dicentrarchus labrax, turbot Scophthalmus maximus, and Atlantic halibut Hippoglossus hippoglossus. The European industry is dominated by rapidly expanding production of juvenile sea bream and sea bass (approximately 450 million fry in 1999). These species are mainly reared intensively in green water, using Brachionus and Artemia as prey, although hyper-intensive clear water techniques and extensive/semi-intensive rearing methods are also used. Large “industrial” hatcheries, incorporating system automation and standardized operating procedures, now account for a high proportion of total European sea bass and sea bream production. Intensive larviculture techniques are also now prevalent for the production of turbot and Atlantic halibut in Europe, although several key operators retain the use of extensively reared zooplankton, owing to pigmentation abnormalities associated with Brachionus and Artemia prey. Output of these flatfish species is relatively low and rising slowly (circa 5 million and 750,000 fry, respectively, in 1999). Future development of the European marine fish hatchery sector is considered in terms of increasing output levels and production efficiency for existing farmed species and adapting hatchery facilities and techniques to enable species diversification.

Effect of Dietary Essential Fatty Acids and Vitamins on Egg Quality in Turbot Broodstocks

Varying egg quality is one of the main factors interfering with the reliable performance of marine fish hatcheries. As larval performance during the first period largely depends on the availability of essential nutrients, the endogenous provision of these nutrients through the egg stages, and possibly parental diet, might be an important tool in improving hatchery output. Therefore, several feeding experiments were conducted on turbot (Scophthalmus maximus) broodstock reared under production conditions at two commercial facilities in France: France Turbot (FT) and Sepia Conseil (SC). Diets varied mainly in essential fatty acids (ω-3 HUFA), Vitamins C and E, and were fed for 2–3 months prior to the reproductive season. Egg quality parameters, i.e. fertilization and hatching rate, egg and oil droplet diameter, and biochemical composition, were monitored for each female during its total reproductive phase. Egg size during the reproductive cycle showed a low variability among females receiving the same treatment, but became significantly smaller as the season progressed. The same occurred for the oil globule in the non-vitamin supplemented groups, whereas it significantly increased in the vitamin-supplemented groups. However, these observations could not be correlated with any of the hatching or fertilization characteristics. The egg dimensions also varied as a function of the diet supplied, i.e. high HUFA levels in the broodstock diet resulted in a significant increase of egg diameter, oil globule diameter as well as fertilization rate. Interestingly, the control groups, with the lowest fertilization rate, had the highest hatching percentage, significantly higher than the HUFA/non-vitamin enriched groups. Using non-selected sources of trash fish as a food source at SC resulted in low levels of ascorbic acid (AA) in the eggs compared to the administration of an optimal quality batch of mackerel at FT. Enrichment of the trash fish with ascorbate-2–polyphosphate (ApP) resulted in a tripling of the AA content. Extra enrichment of the FT control diet did not further increase the levels in the eggs, suggesting that a saturation level was obtained. The major fatty acids in turbot eggs as well as freshly hatched larva are 16:0, 18:1ω-9, 20:5ω-3 and 22:6ω-3, but no obvious changes in their pattern could be detected for the different broodstock treatments. However, the level of 20:4ω-6 was significantly higher in the control group of FT, and showed a high correlation with the hatching percentage of the eggs obtained from the various broodstock treatments.

Vibrios associated with routine productions of Brachionus plicatilis

Surveys for bacteriological analysis were carried out in 1990–1991 in two different marine fish hatcheries located in Greece and northern Spain. Samples were taken from 12 different routine productions of Brachionus plicatilis before and during enrichment. Isolates were characterized by whole cell fatty acid methyl ester analysis and by BIOLOG metabolic fingerprinting. Vibrio anguillarum and/or Vibrio alginolyticus were dominant Vibrio species in the rotifer samples taken after enrichment and rinsing, before being delivered to the fish larvae. None of the Vibrio anguillarum strains belonged to the pathogenic serotypes for juvenile and adult fish.

Variability of the Microbial Environment of Rotifer Brahionis plicatilis and Avtemia Production Systems

AbstractSamplings were organized in three marine fish hatcheries. Samples were taken at different steps during the production of algae, rotifers and Artemia. There were 233 dominant colony types isolated for further characterization. The isolates were compared to each other and to reference strains of Phorobacrerium, Vibrio and Alreromonas, using cellular fatty acid fingerprints. Fatty acid profiles of the isolates were grouped using principal component analysis. The isolates fell into at least ten major groups, of which two correspond to the genera Vibrio and to Alteromonas, respectively. Some groups seem to be restricted to a particular type of live food or isolation site. Although 43% of the isolates belong to Vibrio, only a minority of them could be readily assigned to known species.

A simple semi flow-through culture technique for the controlled super-intensive production of Artemia juveniles and adults

A simple semi flow-through Artemia culture unit is described for possible integration in marine fish and shellfish hatcheries as source of a cheap nursery diet. The system does not require the use of feeding pumps and involves minimal care. Food preparation and addition to the feeding tank is reduced to one or two manipulations per day during the meta-nauplius stages (day 1–3) and the juvenile stages (day 4–14), respectively. Biomass productions are superior to those reported for stagnant culture systems and are comparable to those demonstrated for flow-through culture units. This simple rearing technique offers the possibility of producing brine shrimp populations with a uniform size. Furthermore, by varying the feeding regime with the Artemia density at the start of the culture, specific Artemia prey sizes corresponding to the daily physical requirements in shrimp and fish hatcheries can be obtained.

Preliminary trials with an ultraviolet liquid sterilizer

The effects of a new ultraviolet liquid sterilizer were tested in fresh- and seawater aquaculture installations. Ultraviolet treatment reduced the population of aquatic microorganisms. The mortality rate of experimentally wounded fish kept in sea water treated with ultraviolet radiation was significantly lower than that of controls. A further comparison was made between ultraviolet and chemical treatment of wounded fish. Ultraviolet radiation reduced bacterial population in a marine fish hatchery, but the larval mortality did not decline, probably because of other environmental factors. The use of ultraviolet sterilizers in fish culture is discussed.

European Fish in New Zealand Waters

A VERY useful account of the Marine Biological Station and Fish Hatchery at Portobello in New Zealand has been prepared by the Hon. G. M. Thomson and the late Mr. Thos. Anderton, and is published as Bulletin No. 2 of the Board of Science and Art of the Dominion. There is an appreciative note about Mr. Anderton, a man of great practical ability, who began life as a mercantile marine officer and then became a marine zoologist: he organised the Portobello Station with conspicuous success. The work of this institution is remarkable for the very original experiments carried out in connexion with it, having in view the naturalisation of European fishes and other marine edible animals in New Zealand waters. These attempts are well known in a general way, but it is well to have detailed records of their methods and results.