Ecological Fish Farmers

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Ecologists or fish farmers? Yup! From left to right, Cam MacKenzie, Heidi Golden, Linda Deegan, and Mark Urban are now officially ecological fish farmers.

 

You never know where your research questions might lead but species adaptability to climate change brought us in a brave new direction.  As first-time “fish farmers,” we faced challenges knowing when to begin artificially spawning our three Arctic grayling populations (Kup, Oks-Zev, and Oks3) in order to populate our common garden experiment with hand-raised larval fish. If we started too early, the eggs might be immature. On the other hand, waiting too long might cause the eggs to degrade and become non-viable. When our populations showed signs of spawning readiness, such as fish pairing up within the stream, breeding tubercles, and expression of eggs and milt, we pulled out all the stops to catch fish, using combinations of weir traps, fyke nets and angling. We held the fish we caught in large mesh pens within the rivers so we could check their spawning condition daily. However, although we were able to express eggs and milt early on, we mistook mature eggs for immature eggs due to a unique feature of Salmonid oocytes, lipid droplets, which mimicked early stages of vitelligenesis (the accumulation of yolk within an immature egg). After some deliberation and consultation with more experienced colleagues, we proceeded with fertilizing our Arctic grayling eggs. We hit it right-on with one population, the Kup, almost caught it right with another population, Oks3, and flat-out missed it with our third population, Oks-Zev. In my opinion, the condition of our grayling eggs reflected differences in the timing of spawning for these populations, such that Oksrukuyik headwaters likely spawned first, followed by the lower Oksrukuyik, and then the Kuparuk. Discovering what drives variation in spawning timing for grayling populaitons is certainly on my “To Do” list and I already have some testable ideas in mind. As with every field season, we learn something new about this amazing species, the Arctic grayling, and the Arctic tundra stream ecosystem.

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As soon as the icy waters of the Oksrukuyik become wadable, we enter with rebar and fyke nets to set traps for catching spawning-ready Arctic grayling.

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A beautifully set weir-trap on the lower Oksrukuyik Creek awaits upstream spawning migrants.

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These lucky participants await their chance to donate their eggs and sperm to the scientific cause of assessing local adaptation to climate change in our common garden experiment.  Thanks guys and gals!

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Although these eggs appear to be immature vitelligenesis 1 stage, they are actually fully yolked, mature oocytes with oil droplets (orange spots) within each egg.

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We not only extracted fabulous looking eggs from this female, but our PIT tag popped out, as well!  I’ve often suspected that intraperitoneal tagging could lead to tag loss during spawning. Could be something to that.

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After adding milt from the male, these fertilized eggs must be rinsed, water hardened, and then disinfected before we can safely transport them to Toolik Field Station.

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Linda Deegan and Kate Michmerhuizen painstakingly count fertilized Arctic grayling eggs into treatments for a in situ transplant experiment, placing eggs from each of our populations in all three rivers to see who does best and where.

 

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The 2 am Arctic sun casts its rays on Johanna Ruff, Cam MacKenzie, and Kate Michmerhuizen as we take advantage of the “midnight sun” in order spawn all three Arctic grayling populations as close together as possible.  And although not shown here, Greg Hill caught many of the fish in our holding pens by tirelessly angling these reaches.  Now that’s a dedicated team!

 

 

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