Necropsy Experiment!

As our fish grew larger, we ran into numerous issues regarding their increasing demands for ideal conditions, sadly resulting in 4 fatalities of our 32 fish. This examination gave us an inside look at the fish we lost, and enabled us to form a more educated conclusion on what could be done to prevent further fish deaths. We were able to do this experiment with the Marine Biology club at our high school and share our findings with its 30 members. We found issues with the swim bladder, which may have been caused by stresses due to temperature or inadequate dissolved oxygen content. We hope to have more success in the future by using tilapia, a much more resilient fish. Here are our results: Fish #1: The liver appeared darker and very loosely held together. Otherwise, there seemed to be no visible abnormalities in the first fish. Fish #2:This fish appeared to have a deflated swim bladder. This is shown to be a result of low levels of dissolved oxygen and high levels of carbon dioxide. Otherwise, there seemed to be no other visible abnormalities in the second fish. This inference is based upon the fact that our dissolved oxygen levels were lower than adequate and our system could not provide for our the demands of brown trout. Our system had a dissolved oxygen ranging from 6.2 to 5.8 ppm. Ideally, our system would have been providing closer to 7-8 ppm. According to a 1990 study by J. M. Shrimpton, , D. J. Randall, and , L. E. Fidler, an environment with inadequate levels of dissolved oxygen can change the volume of the swim bladder. We conclude that this fish died due to low levels of dissolved oxygen in our tank. Fish #3:There seemed to be no visible abnormalities in the third fish. The cause of death is unclear. Potential cause may be due to lack of oxygen. Fish #4:This fish appeared to have a fractured spinal cord. This fish was caught in the water pump due to its small size. We learned that it is necessary to cover the pump after this incident.Conclusions: It appeared as if our system was not able to sustain brown trout as well as we has hoped. Since brown trout are a relatively sensitive species, we plan to use tilapia next. Tilapia are the most common fish used for aquaponics purposes due to their hardy nature and ability to withstand diverse environmental conditions. We will be using tilapia for consumption in the Hudson Valley in our upcoming work.