Cost estimates of hatchery production of marine fish fry in the Mediterranean.
EXCERPT : The investment cost of building a hatchery in the Mediterranean will vary among countries and regions. Some projects may require expensive water treatment systems and/or elaborate infrastructures. Most hatcheries are producing fry in intensive systems to maximise on their capital investment and thus it is not surprising that mechanical equipment at 32% and buildings at 27% are the largest segments in the investment costs of a typical hatchery. This can be compared with the proportionate investment costs for a shrimp or prawn hatchery with construction and tanks at 34.1% and 21.2% respectively.
There is considerable variation between investment costs and output possibly due to the different production systems used and the resources available to the investing enterprises. The cost of building a hatchery is also the major contributor to the operating cost as it must be depreciated over its life time. This varies from 0.03 to 0.19 US $ per fry with the depreciation proportion of the operating cost varying from 15% to 50%. Therefore a hatchery's design and construction will greatly affect its final operating cost through its depreciation.
The second largest contributor to the typical hatchery operating cost is labour at 20% followed by fuel and power. The labour proportion is similar to that of a shrimp hatchery. However, the fuel and power portion is largely due to the heating requirements of Mediterranean hatcheries. The main hatchery production season is from October to May with low ambient water temperatures of 8-15C and optimum larval rearing temperatures around 20C.
(Selonda Aquaculture SA, Ag. Panton 9, GR-17672 Kallithea, Athens, Greece)
Experiences in the larval rearing of marine ornamental fish.
The paper examines experiences in the commercial rearing of marine ornamental fish with special emphasis on:
Microbiology and the role of probiotics in Ecuadorian shrimp hatcheries.
Ecuadorian shrimp culture, like similar industries in other countries, has been plagued with disease problems during the hatchery phase. These diseases are primarily microbial and their control is an important concern of hatchery managers and biologists because of their impact on production schedules and economics of both hatchery and farm. A major disease affecting larval rearing occurred in 1989 and developed over the following years to become the primary cause of hatchery mortalities between 1990 and 1992. Locally known as 'bolitas', in reference to the spherical bodies found in the hepatopancreas of affected larvae, this disease causes up to 90% mortality in as little as 12 h.
In an attempt to develop a control program for this disease bacterial analysis of larval rearing tanks was initiated in 1991 using total plate counts on marine and TCBS agars. As a result of this program, it became clear that the bacteria present could be divided into innocuous (Vibrio alginolyticus, Aeromonas spp., Flexibacter spp., and Flavobacter spp.) and possibly pathogenic (Vibrio parahaemolyticus, V. vulnificus, and Corynebacteria spp.) groups. The development of a relative scoring system, termed the log ratio, demonstrated that the development of 'bolitas' in larval and post-larval shrimp is preceeded by an imbalance in the bacterial flora, with a decrease in Vibrio alginolyticus and a rise in Vibrio parahaemolyticus.
On the basis of these observations, Vibrio alginolyticus has been employed as a probiont in many Ecuadorian hatcheries since late 1992. Hatchery down time was reduced from approximately 7 days per month to less than 21 days annually, while production volumes increased by 35% and overall antibiotic use was decreased by 94% between 1991 and 1994. Farm results show that survivals, production, feed conversions and growth rates are not negatively affected by the hatchery use of probiotics, on the contrary they may even be improved by their application. The logical follow-up is currently under development with the hope that through the use of probiotics the current level of survival in Ecuadorian shrimp farms can be restored to pre-Taura syndrome levels.
(Langostinos Ecuatorianos, P.O. Box 9092, Guayaquil, Ecuador)
Vibrio (Listonella) anguillarum infections in marine fish larviculture.
The culture of marine fishes, such as seabass (Dicentrarchus labrax) and seabream (Sparus aurata), is becoming increasingly important in the Mediterranean region. Although the zootechnical procedures are well established for these species, the outcome of a production cycle is still highly unpredictable due to bacterial disease outbreaks. The most critical phase in the production cycle of these species is without doubt the larval life stage. In order to identify the responsible organisms for these mortalities and in order to elucidate the origin of infections in the production cycle, a combined bacteriological and histological analysis was performed on larvae throughout their larval development.
The results of the bacteriological analysis showed that Vibrio anguillarum was present in high numbers, whenever mortality outbreaks occurred and that the presence of this species was linked with the feeding of rotifers to the larvae. In addition histological examination of the fish larvae, sampled in conjunction with the samples for bacteriology, showed infections of virtually all internal organs of the larvae with Gram-negative bacteria. The position of these bacteria in the tissues was remarkable: bacteria were present intracellularly in a typical perinuclear arrangement. By comparing the results of the bacteriological analysis with those of the histology, a good correlation was found between the number of V. anguillarum strains recovered from the sample and the infection level of this sample observed by histology. The identity of the intracellular bacteria, as being V. anguillarum, was confirmed by immuno-histochemistry.
(Laboratory of Ecology and Aquaculture, Zoological Institute, Naamsestraat 59, B-3000 Leuven, Belgium)
