At the Apopka, Florida Pentair AES facility, PAES W.A.T.E.R., our knowledgeable team of aquaculture experts is responsible for the rearing of more than 10,000 fish every year in three species: hybrid striped bass, Nile tilapia (Oreochromis niloticus), and a hybrid tilapia (Oreochromis niloticus x aureus). The production cycle for the hybrid striped bass and hybrid tilapia is similar, about 250-260 days. The nile tilapia production cycle is about 130 days.
As an organization committed to excellence, there are several reasons why we sample our ever-growing fish populations. We monitor growth and general performance, recalculate feed requirements, and determine when fish are ready for market.
So What is Fish Sampling?
We also calculate the feed conversion ratio (FCR) at this time, which is the amount of feed an animal requires to gain a kilogram of body weight. We feed the fish a percentage of their biomass. The FCR of the interval from the last time the fish were sampled would be the total feed that was fed during that interval (ex 14 days) divided by the biomass gain (growth of the fish from the last time they were sampled). The lower the FCR the more efficiently the fish utilizes the protein and fat in the fish feed for growth. The average weight of the fish is used to calculate feed requirements, with an ideal FCR of 1:1. Typically at the beginning of the growth cycle fish are being fed a high percent biomass (15%-10%). The percent biomass fed decreases throughout the production cycle usually ending around 2%-3% or lower depending on the species.
How Do We Do It?
The fish sampling process can vary depending on the type of system and tanks being used for grow out (the longest phase of the production cycle from fingerling to harvest) of the fish. At PAES W.A.T.E.R., we maintain relatively small tanks, the largest at 20 ft diameter and 8600 gallons and the smallest 4 ft diameter and 940 gallons, so we use a seine net to crowd the fish. We then use dip nets to net fish from the crowded area. We count the fish from the net into a container of water that has been tared (the container and the water in it have been set to zero on the scale so the only weight that is measured is that of the fish) on the scale. We record the weight of the fish after a set number has been reached in the container - usually 20-30 fish. We release those fish back into the tank behind the seine net so we don’t catch them again. We continue counting and weighing fish until we have reached our target number.