08 Nov 2021
Year 9 Science have been learning about ecosystems and the nitrogen systems by cultivating Murray Cod.
The practical unit was the brainchild of science teacher Mark Slavin. Mr Slavin, a keen fishkeeper for as long as he can remember, decided that the life cycle of the Murray Cod was an excellent way to model an ecosystem.
“Bringing in live animals helps kids engage,” explains Mr Slavin, “It’s also great that we’re able to model a local system from this area.”
To research the project, Mr Slavin enlisted the help of local business AQUNA, who make a living from cultivating the native fish. AQUNA graciously toured Mr Slavin through one of their farms and walked him through the process they use to grow the fish. They even provided Mr Slavin with a few Murray Cod fillets so he could test the merchandise for himself.
With this knowledge in hand, Mr Slavin then sourced fish tanks, sponge filters and Murray Cod fingerlings from a local pet store and put the classes to work. The students have been charged with setting up the tanks, monitoring the ammonia, nitrate and nitrite of the water in the tanks and journaling their findings.
The nitrogen cycle follows nitrogen in the ecosystem. In the example of the Murray Cod in the tanks, the fish produce ammonia which is then broken down into nitrate and subsequently nitrite by bacteria. The nitrite is then turned back into food by plants which the fish then eat, thus completing the cycle.
Aside from some algae, the lack of plants in the tanks mean that the students need to intervene in the nitrogen cycle to ensure the fish don’t become poisoned by excessive nitrite levels. Consequently, students have to refresh a fraction of the water every day.
“Every class seems to be enjoying looking after the fish,” says Mr Slavin, “They’re also learning a lot. I’ve seen a few of the students' journals. They are really getting better with their observations.”
The experiment is expected to take a few weeks. Once grown, the Murray Cod will be released into local waterways to help boost their numbers in the ecosystem.