We are not the only ones who regard the fish we produce as being a tasty treat.  There are a host of predators that would love to share in the feast and will go to great lengths to accomplish this wish.  Most fish farms operate on a fairly modest margin and cannot, and certainly should not, simply regard predation losses as part of the cost of running the business.  Rather, appropriate and effective systems need to be put in place to control predation and keep it to a minimum, or even exclude it completely if possible.
 
Small fish are eaten by a very wide range of predators including insects and their larvae, as well as species of birds that opportunistically feed on the fry and fingerlings.  As the fish grow they become less susceptible to falling prey to the smaller predators and those that are not specifically fish predators, such that large fish are only vulnerable to a handful of large, specialised, fish predators.
 
The first level of defence is barriers to exclude the potential predators from the culture area.  Land based predators, such as otters and nile monitors, can be excluded by means of boundary walls, possibly in combination with electric fencing.  Ensure that effluent surface water canals are adequately protected.  Aerial predators can be excluded by placing bird netting across the culture infrastructure, again making sure that access points such as gates are secure.
 
Some farms make use of light to discourage fish predators.  Bright reflectors placed on poles do discourage some bird species but are not highly effective, certainly not good enough to be relied upon without barriers being in place.  Other farmers utilise lasers to shine a moving beam across their ponds or cages to discourage birds from settling there.
 
Another, far more sinister, form of loss in theft, which can originate from inside or outside of your fish farming business.  Although not true predation, theft can account for major losses on a fish farm and therefore needs to be managed carefully.  Access control with the checking of vehicles and bags is done on farms where the theft risk is high, elsewhere cameras are used to monitor the actions of staff on duty, especially at critical points such as where the market sized fish are being held and harvested.  Cameras are also effective when deployed across cages, and then manually monitored.  When a suspected intruder is observed a fast boat is sent out to intercept the suspect before a crime even occurs.  The arrival of the fast boat, often out of the dark when no obvious way of knowing the trespasser was there, can have a very unsettling impact on the would-be-thief, discouraging them from future attempts.  For staff who steal dismissal for a first offense is standard to dissuade other potential thieves, with the option of registering a criminal case.
 
The ability to effectively control stock loss is critical for the commercial fish farmer to be economically viable.  Our fish are a tasty treat and so tempting for predators, let’s be sure to protect them effectively.

The photograph shows a commercial fish pond covered with bird netting, to exclude avian predators, and surrounded by a plastic wall to exclude xenopus frogs