Air Incubation Fact Sheet

Julie Lively  |  11/3/2016 4:05:06 PM

Cocahoe Air Incubation

Air incubation appears to be a common occurrence in wild cocahoe minnows. Females are known to lay their eggs among the marsh grass during maximum high tides where they develop fully exposed to the humid air when the tide recedes. The eggs then hatch when they are flooded by the next maximum high tide, approximately 13-15 days later. This situation can be replicated in an aquaculture setting. Air incubation encourages all of the eggs to hatch at the same time yielding uniform sized larvae and subsequently uniform adult minnows. This reduces the likelihood of larger older minnows eating the newly hatched larvae. In addition, air incubation provides the opportunity for easy transport of eggs to grow out facilities or other locations.

Helpful Tips:

-Use an incubator or modified refrigerator to maintain temperature (68-74°F) and keep egg-eating fruit fly larvae out

-Put eggs in containers at low densities to help control fungus -Use saline water between 7-12 ppt to help fight against fungus

-Eggs must stay moist with salt water but not soaked to ensure true air incubation and help control fungus

-Make sure to clean and dry used incubation foam thoroughly after every use to prevent fly larvae infestations

Recommended Procedure

Soak sheets of synthetic foam such as Expanded Polystyrene (EPS) or soft hobby foam in clean saline water approximately 5-15 parts per thousand (ppt), the same salinity used for hatching. Ensure that the foam sheets are wet but not soggy or over saturated. In lieu of foam sheets, eggs may be incubated directly on the spawning mats. Place one mat in a shallow container of the same size with a loose fitting lid (plastic is the most common). If using foam, place eggs on top of the foam sheets and gently cover with another moist foam sheet of the same size. Place the lid on the container ensuring that it is loose enough to allow some airflow. The container(s) should then be placed in an area with a constant temperature between 68 °F and 74 °F. The temperature should be stable for the entire incubation period. A homemade incubator can help with this. An incubator can be made out of a working refrigerator by following the instructions in the “How To” box. The warmer the temperature, the more accelerated the development will be, shortening the incubation period. This allows for egg batches of different ages to be hatched at the same time by storing them at different temperatures. See Table 1 for a list of temperatures with approximate incubation periods. Moisten eggs every two days with salt water (5-15 ppt) in a spray bottle. Once the eggs are ready to be hatched out, submerge eggs in water of the same salinity they have been stored. They should hatch in a few hours or minutes depending on their readiness to hatch. Shortly after hatching, larvae will have the ability to feed. Feed options at this stage include live artemia nauplii (newly hatched brine shrimp), commercial larval diets (Otohime), or plankton collected from a natural water source or aquaculture pond.

How To:

This type of homemade incubator will only be effective for outside temperatures warmer than the desired temperature. To make an incubator out of a working refrigerator acquire an external temperature controller, like the one pictured below. Connect the refrigerator to the female plug of the temperature controller. The male plug goes into an outlet. Place the display in an easy to see but out of the way area. Put the temperature sensor inside the refrigerator with the wire running out to the display. Make sure that the door will still close securely. Set the desired temperature on the dial or display, depending on the model you have. The temperature controller will turn the refrigerator on and off to achieve the desired temperature.

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