Lake sturgeon are listed as as either threatened or endangered by 19 of the 20 states within its original range in the United States. This means that all of the populations of this large bottom-feeding fish are at risk of disappearing from the waters which they inhabit, including Lake Champlain. To be a threatened or endangered species means that the numbers of reproductively mature individuals in a population are low enough that stresses like habitat changes, a disease outbreak, the arrival of an invasive species, bouts of unfavorable weather, or increased levels of pollution can eliminate a population from an area over time. Often, more than one of these stresses act on a population at the same time. For the lake sturgeon, the use of our Basin's rivers to generate power- saw and grist mills in the past, hydroelectric nowadays- have disconnected these large fish from their riverine breeding habitat. The few fish that can still find silt-free gravel beds in which to spawn may produce fewer offspring due to the stresses like elevated pollutants have on their reproductive system.
We were recently contacted by Dr. Louis DiVincenti, a veterinarian for the Seneca Park Zoo in Rochester, New York to see if we might help with a study of lake sturgeon restoration in that he has been involved in for a number of years. Dr. DiVincenti's part of the study is to measure the levels of contaminants present in sturgeon that have been re-introduced to the Genesee River. To put the data from these wild fish into perspective, he asked if we (along with other aquariums) could provide blood samples from the captive lake sturgeon. Because our participation would mean performing some invasive procedures on our most charismatic animals, we decided with caution whether we would participate in the study. Is it worth taking blood from our healthy animals to help their wild cousins?
We decided that yes, we would participate with an appropriate level of caution. We'd carefully capture one sturgeon, coax it into a floating tub, put it under anesthesia, draw the necessary blood for the study, and recover the fish before quietly releasing back to the tank. If things didn't go smoothly, we'd reconsider putting our animal ambassadors at risk for the greater good.
After receiving our supplies and reviewing the protocols for taking the blood samples, we began our work:
A team of three people would work to capture the fish- two using nets to guide the fish into a plastic cattle trough held vertically by the third.Once the fish was captured and contained inside the now floating cattle trough, we allowed it to acclimate to its short-term housing, then dissolved a carefully measured amount of fish anesthetic into the water. At this point, we must track time to prevent an overdose. The longer a fish is in the anesthetic bath, the larger dose it receives. The art and science to this is choosing a dosage that allow us adequate time to perform our procedure
without the chance of accidental overdose. Lower amounts of anesthetic allow more time, but take more time to take effect. Since each fish responds differently to this, a lot of careful guesswork, observation, and patience pays off.Then we wait until the fish become unresponsive to being manipulated, a sign that the anesthesia is working and we can perform the blood draw without injuring our friend. If we act too early, the fish could move and cause the needle to go into unwanted tissues (or us!). We measured the fish's length and girth during this time.
Once the fish is fully "under," we prepared to insert a needle through the muscles between anal pore and anal fin by locating an area of soft tissue
between two of the bony scutes on the underside of the fish. As the needle passes into the muscle tissue, a vacuum tube is engaged to draw blood into it when the needle finds the vein. In this case we are seeking a vein that runs along the bottom of the fish's spine. The needle is pressed downward until it meets the spine, and then very slowly reversed until a "flash" of blood enters the vacuum tube from the vein. The trick is to move slowly enough to find the vein, see the flash, and then hold the needle in place to collect the samples needed for the project.
Once the samples were collected, they were processed and shipped overnight to the lab for analysis. The needle was removed from the fish and the process to recover the fish from anesthesia begins.
By carefully using these methods, we successfully collected samples from all three lake sturgeon that the study required.
Capitalizing on this particular stewardship opportunity was a collaborative effort. In addition to our dedicated animal care staff and volunteers, our friends Dr. J. Ellen Marsden and Susan Fuller at the the Rubenstein Ecosystem Science Laboratory provided equipment without which we could have completed this project. Thank you to everyone involved!
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