Author: Matt H.
Can reach lengths up to 50 feet and weigh up to 30,000 pounds. Have over 27,300 species. Have colors ranging from green to red to blue. Are able to live in water, something impossible for humans. Can swim up to speeds of almost 70 miles per hour, a little less than three times the speed of the fastest human. Some can detect electrical fields, and yet others can even "fly". Yes, I think we can agree that fish are amazing, not to mention beautiful, creatures. And on February 27th, 2013, 20 kids, including me, walked into a room to partake in a hands-on lab with these animals. Walking into the room, we were divided into groups. Once everyone was settled, we started to delve into the world of water. To start off, we discussed fish farms. What they do, what they are used for, et cetera, but mainly about how disease and other things can spread throughout fish farms and the impact that this may have, whether it is on the fish, the farm, or both. Fish farms, well, farm fish! Hence the name fish farm! They basically breed fish so they can be sent to restaurants and other places for us hungry carnivores to eat! But problems can arise in fish farms as well. Think about it. If one fish has a disease, if there is something wrong with it, then chances are that the other fish will soon have the same problem. This is not good. Some fish may die, and some cannot be taken for restaurants. To prevent this, a report about the fish farm and its fish is filled out at times. By comparing the report to what should be normal, you are able to see if something is wrong. Changes in size and weight, for example, can be clear indicators that there is a problem. What the abnormalities are can lead to discovering what the problem actually is and how to fix it. Our instructor asked us why we would inspect or dissect a dead fish. We came up with two reasons. A) To simply learn more about that type of fish, and b) to try and find out why the fish died. That is exactly what they do at the Shedd, and what our lab was about. We were going to perform a necropsy, meaning we were trying to find the cause of death, by first inspecting the exterior of the fish, and then the interior. The first step was to take the mass and length of the mass. Our group's fish was quite small compared to the others; it only had a mass in the 600's. And while two people were doing that, the other two were finding out what the pH of the water the fish was in was. This can have a big effect on fish. The ideal pH range for them is 6.5-8.0, where numbers above 7 are basic and numbers below are acidic. At first it may seem that only acids are harmful, but this is not true. Bases can be harmful, too. Our fish's water's was over 9. This could easily be a factor that affected the fish. The size of the fish also warns that something may have been wrong. When everybody completed the task, we inspected the scales of the fish. Different things could be associated with the scales, two of which being skin rot and parasites. Our group removed one of the scales and looks at it under a microscope. At such a close view, it reminded us of a fingerprint, with the repeating lines and such. Everything looked just as it should. But when we flipped the fish over, however, we noticed what looked like some skin rot on a part of the fish. The scales here did not have a clear, distinguished pattern as the others did. We recorded our finding on our paper, and then moved on. Next, we had to take a clipping of the tail fin using the scissors. Our tail was not in very good shape. The last part of our exterior examination was to inspect the gills. We had cut a bit to get to them, but when we took a clipping, everything looked pretty good. Obviously, the gills are very important, considering they are the fish's way of breathing. Once, we finished inspecting the outside, it was time to examine the inside. Each group was supposed to cut upward, starting near the anal fin, to the line above the lateral line of the fish. The lateral line of a fish detects vibrations in the water surrounding the fish. This allows the fish to sense things such as nearby movement. Dissecting the fish wasn't easy, though. We had to cut through the fish's ribs, each time hearing a loud "CRUNCH". When we finally peeled down the flap of skin, the organs of the fish were revealed. We combed through the fish, inspecting organs such as the liver, ovaries, intestines, and swim bladder, which controls the fish's buoyancy. We actually removed the stomach, and squeezed it so that the digested food came out onto the tray. Perhaps the strangest part of it all was that a large part of the fish's inside was green. That was definitely not normal, and we wondered why it could be like that and if it might have been a reason as to why the fish died. Later, when the biologist came in, he explained that our fish was female, and was going to lay her eggs. This takes energy, so she was storing up extra fat, and that is what we were seeing. After inspecting the organs, we took the lens out of the fish, which is a hard, clear, circular thing that is located in the eye. To do this, we expunged the fish's eye by cutting around it and then into it, where we had to use the forceps the extract the lens. And that was the end of our dissection. Since we finished our dissection, we had to clean up. We disposed of the fish, and then wiped down our tables. Meanwhile, a fish biologist came into the room. When everybody was settled, he shared his presentation with us. He talked about certain places for endangered fish, and how the fish that live hear in Chicago are not all natives. The American Eel, for example, travels all the way from the Atlantic to here and then back again. Some fish also may only live in certain places. He then talked about ways to fish for fish. One method was to generate a shock in the water, which stuns the fish for a small period of time. The fishers can then scoop up the fish with nets. We also learned about threats to fish, such as eliminating things that may seem unnecessary, but when removed can bring harm to the fish in the area, like small rivers or tributaries. At the end of the presentation, we received guides to fish that live right here in the Chicago area. The guides had pictures and information. Things like how the Lake Sturgeon, which can grow up to eight feet long, were once common in Lake Michigan, but are now rare. And how the Longnose Dace was voted to be the official fish of Chicago by schoolchildren. Overall, I learned a lot about fish anatomy, necropsies, and threats to fish. All that we have left is one more session at the aquarium, which I hope will be as informative as this one was.
Author: Matt H.
With Every Drop is a Chicago-based blog, published by CR² team members, that focuses on the biodiversity, ecology, and conservation of marine and freshwater ecosystems.
“Even if you never have the chance to see or touch the ocean, the ocean touches you with every breath you take, every drop of water you drink, every bite you consume. Everyone, everywhere is inextricably connected to and utterly dependent upon the existence of the sea.” – Dr. Sylvia Earle