- Percent Hatch Rate (HR%)
This is ascertained by first determining the Cyst Per Gram (CPG) count and then determining the Nauplii Per Gram count and dividing the two as NPG / CPG.
This number is important because it is the industry standard by which brine shrimp eggs are sold. However, as we are dealing with a living organism, there are inherent variations with the physical characteristics of brine shrimp eggs. Variations that may affect the HR % can be attributed to many factors including the geographical source of the eggs, the biological strain of the eggs, processing methods, etc.
- Nauplii Per Gram (NPG)
This is determined by obtaining the total number of newly hatched nauplii within the hatching container and dividing this number by the number of grams of brine shrimp eggs that were initially put into the hatching container.
This number is significant because this is the number of brine shrimp nauplii individuals that the customer is getting for their money. It is also significant because this is the end product, i.e., this is what will actually be fed to, or consumed by, the fish or shrimp larvae. Many hatchery technicians base their feeding regimes on this number.
This is a subjective indicator ascertained by the individual or technician in charge of hatching out the brine shrimp eggs. It is determined by first taking a sample of approximately 500-1000 ml in an imhoff cone or glass beaker from the hatching container immediately prior to harvesting the brine shrimp nauplii. After the sample has been taken, a visual observation is noted as to the separation of newly hatched brine shrimp nauplii from un-hatched eggs and shells. With excellent separation, one should observe mostly newly hatched brine shrimp nauplii, with little to none eggs or shells on the bottom of the cone or beaker.
This indicator is important because the introduction of un-hatched eggs and shells into the larval rearing tanks can cause water quality problems leading to health related problems with the cultured organisms.
- Volume (CC’s)
This is an indicator that determines the “volume” of a given amount of newly hatched brine shrimp nauplii within a specified period of time. SCI ascertains this in the following way: Brine shrimp eggs are allowed to hatch in an Imhoff cone and after 24 hours, the aeration is removed. After two minutes without aeration, the amount of brine shrimp nauplii are observed and measured at the bottom of this Imhoff cone as per the graduations (in cc’s) located on the Imhoff cone itself.
This indicator is important to those individuals that determine hatch rate quality visually with emphasis being placed on how much “volume” the brine shrimp nauplii are occupying within the container they are using to observe the newly hatched nauplii. Again, the biological variations associated with this living organism is what causes this indicator to vary.