DAO 54:119-126 (2003)  -  doi:10.3354/dao054119

Carriage of potentially fish-pathogenic bacteria in Sparus aurata cultured in Mediterranean fish farms

M. J. Pujalte1,2, A. Sitjà-Bobadilla3, P. Álvarez-Pellitero3, E. Garay1,2,*

1Instituto Cavanilles de Biodiversidad y Biología Evolutiva, and
2Departament de Microbiología i Ecología, Facultad de Biologia, Campus de Burjassot, Universitat de València, 46100 Valencia, Spain
3Instituto de Acuicultura de Torre de la Sal, Consejo Superior de Investigaciones Científicas (CSIC), Torre La Sal, Ribera de Cabanes, 12595 Castellón, Spain
*Corresponding author. Email:

ABSTRACT: A bacteriological survey of gilthead sea bream Sparus aurata from different fish farms and culture systems on the Spanish Mediterranean coast was conducted. Three different studies were performed. Study A included hatchery-reared larvae; Study B, periodic examination of randomly sampled growing fish; and Study C, growing fish sampled only during mortality/morbidity events. In Studies B and C, sea cages, earth ponds and indoor tanks were surveyed, and in both cases diseased (showing clinical signs) and non-diseased fish were included. In Study A, a shift from Vibrio spp. (30 d after hatching) to oxidative species (60 d after hatching) was detected, and no mortality events were registered. The percentage of fish yielding bacterial growth were similar in Studies B and C, reaching 57.4 and 61.3%, respectively. A statistically significant relationship between the bacterial carriage and the type of facility was only found in Study B, showing that fish from sea cages had a higher bacterial occurrence than fish from other facilities. A statistically significant relationship between bacterial carriage and signs of disease was found, although the pattern differed in each study. Thus, in Study B only 36.2% of fish yielding abundant bacterial growth were diseased, versus 68.0% in Study C. In total, 25.0% of the fish examined were diseased. Bacterial species composition was similar in asymptomatic and diseased fish, except for a group of V. ichthyoenteri-like isolates that occurred almost exclusively in asymptomatic fish. Dominant bacterial species were V. harveyi and V. splendidus, followed by V. ichthyoenteri-like isolates, Photobacterium damselae ssp. damselae and V. fisheri. Non-fermenters were less frequent but, among them, unidentified halophilic Cytophaga-Flavobacterium isolates and Pseudoalteromonas haloplanktis were the most abundant. An association of individual species with disease was not clear, which suggests the involvement of mixed infections.

KEY WORDS: Sparus aurata · Vibrio harveyi · Vibrio splendidus · Photobacterium damsela · Pseudoalteromonas haloplanktis · Vibrio ichthyoenteri · Mediterranean aquaculture

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