Greater amberjack, Seriola dumerili. (Photo: StockFile)
Parasites cause natural death of greater amberjack in Mediterranean
Thursday, April 11, 2013, 02:30 (GMT + 9)
Scientists from the Institute Cavanilles for Biodiversity and Evolutionary Biology of the Science Park of the University of Valencia for the first time described the natural mortality of fish due to parasites in the Mediterranean Sea.
The team of experts studied the greater amberjack (Seriola dumerili) in the waters of Mallorca, Alicante, Corsica and Sardinia.
This resource has a strong commercial interest in the Balearic Islands, Murcia, Greece and Italy.
The researchers concluded that parasites can cause significant mortality rate in fish communities in their natural ecosystem.
This time, they documented the deadly effect of the Zeuxapta seriolae, a parasite belonging to the monogenetic group on the greater amberjack.
The results of the study were published in the latest issue of the journal Veterinary Parasitology.
The main objective of the research team is to find treatment strategies based on the life cycle of the resource.
The research director, Francisco E. Montero explained that "the analysis of free communities showed a possible natural mortality caused by the massive infection by parasites."
Commonly, in the wild "the parasite-host system is balanced, since the parasite has no interest in killing its host because it would act to its own detriment and it would cause its own disappearance," he added.
But this balance can be altered in some cases. The system can become unbalanced for a while and the effects of the parasite on the hosts may worsen due to increased levels of infection. "This seems to be the case of this newly emerging parasite in the Mediterranean, about 15 years ago," pointed out Montero.
While monogenetic parasites do not affect humans, they slow the fish growth rate, and, under intensive production conditions, they can cause the death of the farmed specimens, stressed Aigües Repullés-Albelda, author of the study.
"The selection of the juvenile specimens of the area with lower incidence of the parasite and at the time of the year under better conditions would contribute to increase the profitability of the operation because they may speed up, in a simple way, the initial infection levels," added the researcher from the University of Valencia.
During the study, the team conducted periodic sampling to 245 fish from different regions of the western Mediterranean.
All the specimens were measured and weighed to estimate their health level. Then, they were analyzed separately and the parasite specimens were identified as well as their development stage.
"One factor that could have favoured the spread of the fish is the water temperature, which has been slightly higher in recent years," Montero noted.
Therefore, the researchers asked Puertos del Estado, an agency under the Ministry of Development, to provide data on water temperature in the main sampling area, and the Directorate General of Fisheries of the Balearic Islands was requested the capture records during recent years.
The experts emphasize the economic impact of this research, given that this kind of parasitic infection is very common in aquaculture.
By Analia Murias