Harvesting systems eel

Eel culture generally involves partial harvesting, grading and stocking at regular time intervals. Due to the intense nature of many culture systems, harvesting techniques are usually relatively simple, though care is needed to minimize the stress induced by harvesting. Normally, feeding is suspended the day before harvesting. When the eels reach a marketable size, harvesting is carried out with a scoop net in the feeding area, when the eels congregate at the usual feeding time. During harvesting, oxygen levels are kept high by admitting freshwater into the culture system or by direct oxygenation (Pillay 1995).

During the summer in Japan, when water conditions are poor and the eels do not group together, a seine net is used to herd the eels towards the inlet area of the pond, where they are harvested using small dip nets. This seining procedure is successively repeated to oxygenate the pond. In winter, eels are harvested by draining the ponds on warmer days. Generally, harvesting takes place in the morning because the eels follow the water flow and do not burrow into the bottom. If they do, a T-shaped wooden scraper can be used to harvest them. If a large number of eels should remain in the pond, the pond can be refilled and drained during the night, causing the eels disturbed by drainage to exit (Pillay 1995). After harvesting, eels may be placed in cages and sprayed with well water at a low temperature (about 15°C) for a short time before shipping for consumption (Kobayashi et al. 1999).

In Australia, eels are harvested from 150 g to a few kilograms in size, depending on the target market. Harvesting may be carried out by draining the pond using a net attached to the outlet pipe, using a seine net, or using a scoop net at feeding time. The eels are sorted into different sizes using a grading tray. They are then placed into holding tanks for several days without feed to purge their stomachs. Chilling and packing into strong plastic bags with just enough water to ensure that their skin remains moist follows. Eels can breathe through their skin, so the bags are filled with oxygen for transportation to market (www.dpi.qld.gov.au/fishweb).