08-08-2019, 06:07 PM
[#0000FF]Got a response from Chris Penne. Thanks, Chris.[/#0000FF]
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Yes, we've got some info. The Standard Examiner did a pretty good article on it. [url "https://www.standard.net/news/environment/thousands-of-fish-dead-at-pineview-officials-say-water-quality/article_73717c62-2071-53dc-9025-fba54e60282c.html"]Here's a link[/url]. A few additions I'd make would be that this is pretty common with black crappie across their range. It's not uncommon for big year classes of crappie to undergo die offs like this. In the case of these fish, they were spawned in 2017 during the high water that year. They had a similar die off last year, but the die off wasn't as large and not nearly as noticeable as the fish were 2" at the time as opposed to the 4" long they are now. The short of it is they are crowded, hot, hungry and stressed. These events typically happen during the heat of summer and that also typically coincides with reservoir drawdown. Once the water starts going down, brush and vegetation gets more limited and it seems most of the crappie that can't find that habitat choose to try to make a living in the shallows rather than go in open water and risk being food for predators. In the shallows things get hot and crowded. Warmer water holds less oxygen and we've measured temps as high as 80 degrees along the shorelines in the afternoons.
This is just a more extreme example of natural mortality that fish populations undergo all the time. We're not really any hotter than other years that I can tell, so I think the magnitude of the die off we're seeing can be attributed to just how many young crappie there are right now. The more crappie we have, the more crowded conditions get. The bright side is that even as these fish are dying there are still plenty of healthy fish to be caught in Pineview. Whether these die offs knock this year class of crappie back enough that it eventually turns out to be a small year class has yet to be seen, but there should still be plenty of crappie in Pineview. We refer to this in fisheries management as "density dependence", where the density of a year class of fish can affect it's success over time. We see density dependence in other species like walleye and kokanee, where as an example, sometimes it's better to have an average spawn and year class as the really big year classes often end up losing a lot of individuals over time to starvation, disease or other negatives that come with crowding and competition.
It's hard to say whether this will be good or bad in the long run. The way I see it, it's going to come down to how many fish we lose. If we lose enough fish that it turns into a subpar year class that could be seen as a setback. If we lose enough fish that it allows a good number of remaining fish to quickly grow to a desirable size then it will be a positive. That's one of the trickier parts of crappie management, particularly at Pineview, which is the big year classes take a long time to reach that 7-8" long that people start considering harvestable, whereas the smaller year classes are quicker to reach that desirable size. So there's pros and cons to each scenario. Overall, it's not something we're particularly concerned about but it is indeed interesting when it happens.
Hope that helps.
Chris
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[#0000FF] [/#0000FF]
Yes, we've got some info. The Standard Examiner did a pretty good article on it. [url "https://www.standard.net/news/environment/thousands-of-fish-dead-at-pineview-officials-say-water-quality/article_73717c62-2071-53dc-9025-fba54e60282c.html"]Here's a link[/url]. A few additions I'd make would be that this is pretty common with black crappie across their range. It's not uncommon for big year classes of crappie to undergo die offs like this. In the case of these fish, they were spawned in 2017 during the high water that year. They had a similar die off last year, but the die off wasn't as large and not nearly as noticeable as the fish were 2" at the time as opposed to the 4" long they are now. The short of it is they are crowded, hot, hungry and stressed. These events typically happen during the heat of summer and that also typically coincides with reservoir drawdown. Once the water starts going down, brush and vegetation gets more limited and it seems most of the crappie that can't find that habitat choose to try to make a living in the shallows rather than go in open water and risk being food for predators. In the shallows things get hot and crowded. Warmer water holds less oxygen and we've measured temps as high as 80 degrees along the shorelines in the afternoons.
This is just a more extreme example of natural mortality that fish populations undergo all the time. We're not really any hotter than other years that I can tell, so I think the magnitude of the die off we're seeing can be attributed to just how many young crappie there are right now. The more crappie we have, the more crowded conditions get. The bright side is that even as these fish are dying there are still plenty of healthy fish to be caught in Pineview. Whether these die offs knock this year class of crappie back enough that it eventually turns out to be a small year class has yet to be seen, but there should still be plenty of crappie in Pineview. We refer to this in fisheries management as "density dependence", where the density of a year class of fish can affect it's success over time. We see density dependence in other species like walleye and kokanee, where as an example, sometimes it's better to have an average spawn and year class as the really big year classes often end up losing a lot of individuals over time to starvation, disease or other negatives that come with crowding and competition.
It's hard to say whether this will be good or bad in the long run. The way I see it, it's going to come down to how many fish we lose. If we lose enough fish that it turns into a subpar year class that could be seen as a setback. If we lose enough fish that it allows a good number of remaining fish to quickly grow to a desirable size then it will be a positive. That's one of the trickier parts of crappie management, particularly at Pineview, which is the big year classes take a long time to reach that 7-8" long that people start considering harvestable, whereas the smaller year classes are quicker to reach that desirable size. So there's pros and cons to each scenario. Overall, it's not something we're particularly concerned about but it is indeed interesting when it happens.
Hope that helps.
Chris
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[signature]