The Artemia Hatchery
The development of an Artemia hatchery is a performance based learning experience that is part of my Aquaculture Science program at Honoka'a High School. Students are given the parameters vital to an Artemia hatchery and are asked to construct one using a liter bottle. The construction of the hatchery gives evidence of the mastery of the concepts that they have learned. A log is kept as a record of their progress throughout the activity from which a final lab report can be written. The final lab report outlines the materials that were used, the design of the hatchery (and the changes made to improve it), the results (percent hatch out) of each of the hatcheries that were designed and tested, and an evaluation/conclusion of the project.
INFORMATION FOR THE TEACHER
The students work in groups to develop their hatcheries, working cooperatively in its design and construction. The primary objectives of this unit are for the students to be able to:
The lessons begin with the introduction to Artemia as a primary food source of many aquaculture species during their larval stages. The life cycle of the Artemia is studied by looking at it in various stages of development and examining the biological requirements of the animals. Once introduced to the factors that affect the hatching of Artemia cysts, the students are asked to construct a hatchery with the materials provided.
- List the important characteristics ofan Artemia hatchery
- Construct and refine an Artemia hatchery
- Analyze water quality.
- Analyze the success of their hatcheries through statistical analysis.
- a. Determine hatch out rates of their hatcheries
- b. Determine Artemia population using population sampling techniques.
- Observe the developmental stages of the Artemia
- Demonstrate an analytical approach to the development of the hatchery through the scientific method.
Students are asked to construct a hatchery of their own design with the materials provided. Additional materials are provided for the students if requested and available. The hatchery needs to provide the proper environmental conditions for hatching Artemia cysts as well as allow for harvesting after hatching.
When construction is complete, the hatcheries are stocked with 1 to 3 grams of Artemia cysts. The actual amount stocked affects the hatch out, so it is one of the critical decisions made by the group. The students record all essential data that may affect the hatch , such as stocking rate, air flow, pH level, starting time, and salinity. This data will be used in the evaluation of the hatchery after harvesting.
The following are some of the parameters that are important in the hatching of Artemia (Hatching instructions are generally provided with your Artemia Cysts):
- Water quality should be clean and free of disease pathogens and bacteria.
- Clean hatchery methods: Hatcheries and equipment should be disinfected. (Alconox or chlorine are good disinfectants).
- pH: Incubation water should have an initial pH of at least 8.5 as pH will decrease with incubation time.
- Illumination: Ideally the incubation tank should be subjected to constant illumination.
- Temperature: 28 degrees Celsius should be maintained and should never drop below 24 degrees of above 30 degrees Celsius.
- Aeration: Dissolved Oxygen levels are not of primary importance but aeration is needed to keep Artemia cysts circulating. Aeration cannot be too excessive as to splash cysts out of the incubating solution.
- Salinity: recommended to be approximately 28ppt.
- Density of cysts should not exceed 10 grams / liter.
- Incubation Time: usually hatch out takes approximately 24 hours.
- Before placing cysts into the hatchery, cysts should be disinfected for 10-20 min. in an aerated bath of chlorinated water ( ~.4% household bleach and water solution). After disinfecting thoroughly rinse cysts with tap water.
Once the required incubation time has elapsed, the students harvest the Artemia . The method by which the Artemia is harvested is also determined by the cooperative groups. Poor harvesting technique will result in a lower percentage of hatch out.
HARVESTING OF ARTEMIA AND DETERMINING THE HATCH OUT RATE
Once the cysts have been incubated the cysts need to be harvested. Be sure to carefully harvest as many nauplii as possible so that an accurate estimate of the hatch out rate can be calculated.
HARVESTING OF ARTEMIA
Once T90 ( time at which 90 % of the cysts have hatched-each grade of Artemia has its own T90 rating usually about 22-24 hours) has been reached it is time to harvest the Artemia. The empty cysts of the Artemia have no nutritional value and carries higher amounts of bacteria , therefore, needs to be separated from the Artemia nauplii. This is done by shining a bright light near the collecting area at or near the base of the hatching cone. Aeration should be removed and the tank should be allowed to stand for 10 -15 minutes before beginning to harvest. The nauplii are attracted to and should gather around the light at the collecting area and should be siphoned off with a tubing (this would be a good time to discuss the behavior of Artemia).
EVALUATION OF THE HATCHERY
The effectiveness of the hatchery is evaluated by the hatch out rate which is calculated by taking a population sample of the Artemia hatch.
DETERMINING THE NAUPLII DENSITY
Take 9 - 1 mL samples using the 1 mL pipette and place each sample into the depression sampling dish. Count the Artemia nauplii and divide the total by nine to get the number of nauplii/mL. The total number of Artemia nauplii is calculated using the following formula:
(Number of Artemia Nauplii/mL) X Volume of Water (mL)
The percent hatch out is determined using the following :
total number of Artemia nauplii / total number of cysts put into hatchery*
* there are approximately 240,000 cysts per gram.
Students then evaluate the effectiveness of their hatchery design, discuss their results with the class, develop a hypothesis that will improve their design, and redesign their hatchery to improve their hatch out rate and test their new hypothesis as they revise and reconstruct their hatchery design and harvesting methods.
Students are evaluated through objective tests and performance portfolios (lab reports and records) which document the research and development of their hatcheries.
What makes this unit successful is the fact that the development of the hatchery is student centered. Their work is crucial to the maintenance of the aquaculture stock. The hatcheries will be used to culture Artemia to be used as a food source for the animals that they will be raising in their aquaculture tanks. Most of the animals that are hatched will be used to feed their post-larval prawns.
The process of evaluating and reevaluating their hatcheries is important in the learning process. The hatch out rate is a very concrete evidence of learning success. It is a good example of real world and applied learning.
The Aquaculture Science course is interdisciplinary and develops integrated skills and knowledge in science, math, language arts, computer science, and history. Students are able to see the application of the principles and concepts they are learning in the classroom to authentic tasks. Concepts learned in chemistry, biology, algebra, physics, and geometry are applied to the development of the aquaculture system.