Defining Technical Words in Aquaculture:

By Alex Choompo

Understand the Common Words and Definitions that are used in Fish Farming Stories.

I have decided to share the basic definitions, terms and/or words that are common in aquaculture language. Following the questions that we receive in the field and from readers of the Agricoop newspaper’s fisheries corner, I thought this will be helpful as we carry on with acquiring information about fish farming and aquaculture in general.

Acclimate:           Allowing the animal to slowly adjust to new environmental conditions.

Aeration:             Mechanically adding air into water with the objective of increasing the levels of dissolved oxygen in the water.

Algae: A large group of simple non-flowering plants that includes seaweeds and many single-celled forms. Algae contain chlorophyll but lack true stems, roots, leaves, and vascular tissue.

Anaerobic           This refers to life forms or processes that occur in environments with limited or no oxygen.

Anoxia (Anoxic) A situation whereby the dissolved oxygen level is zero in water.

Appetite:             The desire for food.

Assimilation:      This means to incorporate, absorb or integrate, i.e., combine two substances to the point where one cannot distinguish them as separate. With feeding fish, assimilation of ingested feed refers to the incorporation of digested food materials into cells and tissues of the fish’s body.

Base of Dam:      The width of the dam base. This is largely dependent on the slope of the dam.

Best Management Practices        This term is used to describe a practice considered to be the most practical means of solving a resource management problem or reducing pollution levels to those compatible with water quality goals.

Biomass or ‘Standing Crop’:         The total weight (mass) of the fish in the pond at any one time.

Carrying Capacity:            The maximum biomass the pond can hold for production without resulting into water quality problems.

Condition(ed )(ing):         Holding fish without feed for a minimum of 48 hours in good quality water at the hatchery or nursery prior to their collection and transportation to the grow-out farm.  The major objective of doing so it to allow the fish to empty their guts in order to reduce stress and maintain water quality during transit.

Dam (dike, dyke, or Levee):         The dam (i.e. dike, dyke, or levee) is the embankment that holds the water in the pond.

Disease:              This is the manifestation of something gone wrong. Body functions become impaired as a consequence of stress, inherent weakness or infection.

Feed Conversion Ratio (FCR):      The Feed Conversion Ratio (FCR) is the amount of feed units it takes to produce a unit weight of fish.  It is a measure of the efficiency of feed utilization.  It is a critical parameter to monitor, as it determines the viability of the enterprise in feed-based production systems.

Feeding Frequency:        This is the number of times in a day fish in are pond are given food. (This represents the number of times fish are fed in one day.)

Fingerling:           A young fish, e.g. tilapia juveniles that range between 5-20 g.  

Flushing/ Flocculate: Replacing a half or more of the water in the pond within a day or less. The objective of flushing a pond is to get rid of or dilute excess suspended and soluble wastes. Think of flushing a toilet.

Freeboard:         Distance from the maximum water line to the top of the dam.

Green-Water:   This is when phytoplankton density in the pond is maintained at an optimum level as a means of managing water quality for tilapia production.  Because of phytoplankton, the pond water consequently looks greenish

Gutting Removal of the intestines and other viscera from the abdomen of a fish.

Health :                The standard or typical condition of the fish, whereby its bodily functions are normal.  A healthy fish functions optimally and is free of abnormalities of stress and disease.

Height (h):          The height (h) of the dam is the distance from the base to the top of the dam.

Maximum Sustainable Yield:        The maximum amount of fish that can be harvested from a natural water body without causing long term negative effects.

Metabolism:      Series of processes by which food is converted into energy and products needed to sustain the life of an animal. In the process of food metabolism, wastes are also produced. For example, in fish, ammonia is produced as a result of protein metabolism.

Optimum Ration:              The fish feed that the best growth and Food Conversion Ratio (FCR). There is minimum wastage and minimum deterioration of water quality when fish are fed optimum amounts of feed.

Oxidation (oxidize):         A chemical reaction where oxygen binds to another substance; this substance becomes oxidized. Typically, oxidation changes the physical and/or chemical attributes of a substance, e.g. becoming less acidic. An example of oxidation is rust forming on iron when it is exposed to air.

Phytoplankton:                 A type of plankton that consists of microscopic plants that grow in water. Phytoplankton create their own food energy through photosynthesis and do not consume other plants or animals.

Piping or gasping:             This is when the fish come out of the water to gasp in air.

Production Cycle:             This is the period between stocking and harvesting when fish are being raised in the pond.

Ration:  The amount of feed given to the fish per day.

Sampling:            This is the removal of fish from the pond to assess their growth and health status. After the observations are made the fish are returned to the pond.

Satiation:             The fulfillment of the desire for food. When fish are satiated (full) they show no interest to take in more feed.

Secchi disc:         This is a simple tool used to measure the turbidity of water. It is circular disc usually made out of wood or a metal plate. The upper surface of the disc is divided into four quarters.  Two of the opposite quarters are painted black and the other two opposite quarters white.  

Shooters:            These are fish of the same age group within the same population that grow much bigger than the rest. Often such fish cannibalise the smaller ones.

Standing Crop:  The total weight (mass) of fish in the pond at any one time.

Stock:    Generally, refers to the fish in production within the pond or on the farm.

Stocking:              Putting fish seed into the pond. Stocking the pond marks the start of the production cycle.

Stress:  An abnormal physiological condition of fish. Often resulting from environmental conditions that are beyond a fish’s normal adaptive response limit or tolerance.

Thermal Stratification:   Differences in pond water temperature based on depth. For example in a pond that is 2 meters deep, one could expect the upper meter to be distinctly warmer than the lower meter.

Toe:       The point where the slope of the dam reaches the pond bottom. The inside toe refers to this point within the pond and the outside toe refers to this point on the outer embankment.

Top Width (TW):               The width of a dam above the water’s surface. This area is typically used as a walkway around the pond.

Turbidity:             The degree to which light penetration through the water column is blocked. Turbidity in ponds is often directly related to the amount of small particles, e.g. clay or phytoplankton, that are suspended within the water column.

Whole Fish:        This refers to the fish before it has been gutted, i.e. before any of it body parts have been removed for whatever reason.

Zooplankton:     A type of plankton that consists of microscopic animals that grow in water. Zooplankton must consume phytoplankton or other microscopic animals to survive.

Will continue to give you all the necessary information, helpful for your research and development as we move passionately towards achieving our fish farming agenda.