Health Status of Eel (Anguilla sp.) from Natural and Temporary Rearing.

Abstract

Eel (Anguilla sp.) has been become a high economic valuable fisheries resources which has decreasing stock for the last two decade. The dependence of aquaculture from natural catching of juvenile, because of unknown breeding technique, derived this organism into over fishing for juvenile which is migrate to upstream or the adult which is migrate to deep sea to breed. Influence of pollution and or pathogen infection has been supported the decrease of stock in nature. The health status of this organism, therefore used to analysed population structure and the change of individual and population in order to make some strategy to keep this resources ever last and to develop the best aquaculture technique. The health status are information comprised organism condition linked with immunity of pathogen infection, interaction with other microorganism and influence of nature condition. This information would be useful to know the fitness of organism in their natural live or in artificial nature such as aquaculture. This research has been held to compare the eel health status from natural and temporary rearing during ten days of rearing in fish collector before use to aquaculture. This information would be useful to develop some standard health status of juvenile eel and to create the best temporary rearing method in order to keep the quality of juvenile. Sample were taken from two main rivers in Cilacap Residence (Donan River and Serayu River) where the eel use it as migration route. Sample also taken from bendung gerak Serayu, an artificial dam, which is obstructing the migration of eel. The result shows that although no significant different in condition factor, the temporary rearing has increasing reddish node in the head, body, fins and tail of eel. There are four parasite founded in this research that are Nematode (Procamallanus sp. and Anguillicola sp.) which are infected internal organ of eel and Platyhelminthes (Dactylogyrus sp. and Deropristis sp.) which are infected the gills. Identification of Anguillicola sp. is the first record from Indonesian waters. The bacteria founded in this research are Aeromonas hydrophylla, Pseudomonas luteola, Vibrio fluvialis, Aeromonas sobria and Aeromonas caviae. The highly prevalence of infection coming from genus Aeromonas and has been influenced the haematological condition and histopathology of eel. Decreasing of haematocrit level from 38.27 ± 0.63 in sample from bendung gerak Serayu to 37.54 ± 0.45 (%) and total erythrocyte from 2.47±0.18 to 2.36±0.11 (x106 cell/ml) after ten days temporary rearing in Kebasen shows that this group of bacteria has a very high potent causing anaemia in eel. In the other hand, increasing of total erythrocyte, decreasing of lymphocyte percentage and increasing of monocyte and neutrophil percentage for all observed sample indicated that eel had been developing innate immunity to face of inappropriate condition in temporary rearing. The pathogen disruption has also been detected from histopatologycal disorder such as hyperplasia of gills, necrosis and inflammation of heart and necrosis and lesion of muscle. Infestation of parasite with their hooks and or infiltration bacteria with their virulent factor could damage the cell of eel organ. This disruption shows that temporary rearing has been becoming some factor which is decrease the health status of juvenile eel, and therefore the aquaculturist needs to be more careful ini selecting the juvenile and needs to cooperate with the fisherman and fish collector to make some better technique in temporary rearing.