Tank and cage management
Tanks, raceways and cages are all artificial enclosures that need daily management to work efficiently. The life of the fish contained in these structures is entirely dependent on the lifesupport systems installed (pumps, blowers, water flow and climate control in the case of
tanks and raceways; feeding and water quality in
the case of cages).
Inlets and outlets, water temperature and other water-quality parameters need regular checking.
Maintenance of predator proofing, pumps and plumbing, tunnel plastic coverings, cage integrity, growth recording and size-sorting of
fish are all daily demands on the fish culturist’s time. The more intensive the management and the greater the amount of care in fish
husbandry, the better will be the results in terms of fish yields and quality. Slack management
will result in system failures, which may happen over weekends or at night, when heavy fish mortalities can occur in the absence of anyone to fix the problem.
While a regime of regular fish feeding is indeed essential, there is far more to fish husbandry than just providing the fish with food. It only takes a failed pump to wipe out all the stock
in an intensive system, or a damaged cage to lose most of the stock from cage culture, thus regular servicing and checking of such fish-farm hardware is essential. Where possible, pumps and blowers should have a back-up, or if this is too expensive, stocking rates must be kept at a low-enough level whereby an electrical failure does not cause immediate stock loss.
As a cattle or sheep farmer gathers his herd together to do daily checks, with regular dipping against ticks, so should a fish farmer check the health and growth of his/her stock at regular intervals. This means sampling the ponds with
a throw-net or other least-disturbing collecting method, and checking for health, growth, or any signs of stress. Several times after the initial
stocking, the ponds, tanks or cages may need to be drained and emptied of fish to size-sort them, such that growth of the slower-growing
individuals is not affected by the fastest-growing ones. At the same time predators can be eliminated, and the pond bottom remodeled or fertilized accordingly. The fish can be size-sorted and distributed to other ponds that have been
prepared. All this activity requires equipment, planning and manpower such that the whole operation does not overly stress or kill the fish. A rough schedule of essential activities is illustrated in the table below. These activities are not all that the farmer needs to do, but he will soon acquire a sense of how well his stock is doing by regular observations of feeding or shoaling behaviour of the fish, in just the same
way as a cattle, sheep or goat farmer can tell the
state of his animals by regularly observing them.
An essential ingredient to successful fish husbandry is to prepare well in advance for any operation that involves catching or moving any of the fish stock, to reduce stress to a minimum.
Attention to such details as sufficient buckets or containers, water temperature differences between waterbodies, adequate and suitable
nets for the job, enough staff to carry all the equipment, prepared tanks to put the fish in that are to be moved, and many other factors, are all vital components of good fish husbandry.