Here are some technical terms used by hatcheries.
The adipose fin is a small, fleshy fin located on the salmon’s back in front of the tail fin. It is commonly clipped in hatchery-raised salmon to mark them for identification purposes when they return to spawn. It was once thought to be a non-functional vestige, but is now understood to likely be a sensory organ helping the salmon adjust its tail movements for better stability and maneuverability, especially in turbulent waters. Clipping is still the most efficient way of marking salmon, which is crucial for management of fish stocks.
The various stages of development, such as the eyed stage and hatching time, can be predicted by hatchery staff. They do it by keeping track of the water temperatures over time. The sum of the temperatures is called the ATUs (Accumulated Thermal Units).
Here's how it works: On the day the fish eggs are fertilized, the water temperature is measured and recorded on a chart. Each day, a volunteer goes to the hatchery, again records the water temperature, and adds it to the previous day's entry. For example, if the temperature is 9° on November 7th, 9° on the 8th and 10° on the 9th, the ATUs equals 28.
It is known that Coho eggs reach the eyed stage and are ready for shocking when they reach 220 ATUs, they will hatch as alevins with yolk sacs at 400—500 ATUs and they will emerge as fry at 700—800 ATUs. This knowledge makes it possible to control and predict development by adjusting the incubator's water temperature—an approach that's useful for scheduling.
Broodstock refers to collecting sexually mature adult salmon, male and female, for the purpose of spawning (breeding) in order to produce fertile eggs. These are the "parent" salmon whose offspring are used for the hatchery's purposes.
A Capilano trough is a specialized water tank used in fish hatcheries for rearing salmonid species. Originally designed in BC and named after the Capilano River, they have been widely adopted in fish hatcheries across the region.
The trough simulates natural water flow which is crucial for oxygenation and maintaining a healthy environment during the rearing of salmon fry before they are ready to move to larger rearing ponds.
In the fish hatchery business, an egg take refers to the process of collecting eggs from female fish (broodstock) and fertilizing them with sperm (called milt) from male fish. It marks the beginning of the hatchery cycle, where fertilized eggs are then incubated and raised into juvenile fish.
Eggs that have developed to the point where the eyes of the embryo are visible—an early developmental milestone.
A Heath tray is a type of vertical incubation system used to efficiently incubate large numbers of salmon eggs.
It consists of a series of stacked plastic trays with mesh bottoms in which water flows from the top tray downward, keeping all trays oxygenated and clean. The water temperature is monitored closely using the ATU system to determine the rate of development of the eggs as they go through stages from green to eyed to alevin before being transferred to Cap troughs.
This refers to the process of transferring fish fry from the Heath trays into Cap troughs or rearing ponds. It typically occurs after the fry of absorbed their yolk sack, and are capable of swimming and feeding on their own. It allows for more space, better water flow, and access to food which are crucial for growth and survival.
Taxa (singular: taxon) are groups of organisms that are classified together based on shared characteristics.
In biology, the term taxon can be used at any level of classification, whether species, genus, family, order, class, phylum, or kingdom. For example, the coho salmon belongs to the species taxon Oncorhynchus kisutch and in turn the genus taxon, Oncorhynchus and the family taxon Salmonidae, etc.
So, “taxa” basically means groups of living things organized by how they relate to each other.