Fish Population

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The decrease in fish populations are dramatically affecting commercial and recreational fishing. For example, less people are going on charter fishing trips because they do not catch any fish or not as many as they were hoping for. The fishing industry could end if charters do not catch any fish. People used to catch a dozen of Salmon in one day and now are lucky to catch one. The low fish population is causing people and fishing guides to sell their boats because they no longer go fishing since they rarely catch anything. Having little fishing tourists will affect the businesses like hotels and stores that surround charter companies.

The Impact of Invasive Species

The Round Goby: The Round Goby originated from the Black and Caspian Seas. The Round Goby was first observed in the bays and harbors of Lake Michigan in 1993. This invasive species population has exploded in Lake Michigan. To keep their population in check, Yellow Perch, Burbot, Smallmouth Bass, Lake Trout, and Whitefish have added the Round Goby to their diets.[1]

Zebra and Quagga Mussels: In May 1988 near Indiana, the first zebra mussel was found in Lake Michigan. Then zebra mussels was spotted in 1992 in The Bay Of Green Bay. The invasive mussels have been spreading throughout Lake Michigan. Bottom trawl surveys have noticed an increase in mussel population in the last few years. The surveys have also concluded Zebra and Quagga Mussels are moving to deeper waters which is allowing the population to expand. Studies have shown the Quagga Mussel's population in Lake Michigan has peaked and exceeded the carrying capacity. Seeing these results, the population is expected to decrease. [2]

Prey Fish Populations Affected by Invasive Species

Alewife: The Alewife population has been at an all time low. Too many predators and invasive species are to blame. There are too many predators feeding on young Alewives to allow the Alewives to reproduce.[3] Invasive Zebra and Quagga Mussels have changed the nutrient dynamics in Lake Michigan and are competing with Alewives over the same food source.[4] Since Zebra and Quagga Mussel's population is much larger than the Alewives, it is making it harder for the Alewife population to expand when there is a scarcity for food.

Bloater: The Bloater fish is similar to Alewives since they are both preyed upon by Salmon in Lake Michigan although Salmon prefer Alewives. The Bloater fish is also preyed upon by Lake Trout. The decrease in population is caused by Slimy Sculpins eating Bloater fish eggs. There is also a theory the Bloater fish has been pushed to deeper water than where they are normally found. This theory is based upon commercial fisherman catching Bloater fish in deeper waters during the past five to ten years. [5]

Rainbow Smelt: The Rainbow Smelt are important for the diet of Lake Trout and Salmon in Lake Michigan. Rainbow Smelt used to make up eighteen percent of the diet for Chinook Salmon but has decreased to two percent in 2009. They are now considered a rare diet for Salmon. There is no clear answer why the population has decreased but Salmon predation is not the answer. The Rainbow Smelt population was four times greater in 1992-1996 compared to 2001-2013. The decline in population is also affecting commercial fishing in Wisconsin waters.[6]

Sculpins: Sculpin populations are at a record breaking low. Spoonhead Sculpins used to be very common in Lake Michigan but have now disappeared. The fish are moving to deeper waters due to Zebra and Quagga Mussels and the stocking of juvenile Lake Trout into Lake Michigan. The decrease in population is from Lake Trout, Burbot, and Alewives overfeeding on Sculpins and Sculpin eggs. [7]

Ninespine Stickleback: Fortunately for Ninespine Stickleback, Salmon and Lake Trout in Lake Michigan rarely feed upon them. Yet the population is still fairly low. Currently, the low population is caused by Piscivores adding them to their diets since the Alewife populations are down.[8]

Predator Fish Populations Affected by Invasive Species and Low Prey Fish Populations

Chinook Salmon: The Salmon population has decreased seventy-five percent since its peak in 2012.[9] The population is decreasing due to many factors. One reason is Salmon are having a difficult time spawning due to the warm and low water levels in streams. The population of surviving spawning Salmon has decreased from six million to one million fish. A second reason the fish population is so low is due to the low populations of Alewives which makes up most of a Salmon's diet. Salmon do not feed on other prey fish because they are hard-wired to feed on Alewives. The last reason the population has decreased is because the DNR has reduced the amount of Salmon they stock into Lake Michigan since the Alewife population is so low.[10]

Burbot: The Burbot population was recovering in the 1980s but has been decreasing since. In order for the Burbot to recover there needs to be a decrease in the Sea Lamprey and Alewife population. Although the decrease in Alewives in Lake Michigan has not made major improvements for the Burbot population. Burbot fish have been moving to deeper waters because their main food source, Sculpins, have been moving to deeper waters. [11]

Yellow Perch: The Yellow Perch population is extremely valuable to recreational and commercial fishing. In 2005, the Yellow Perch population was at an all time high because many females spawned they had good weather for spawning. Since 2005, the population has been dropping dramatically and there is no clear answer why.[12]

References

  1. “Status and Trends of Prey Fish Populations in Lake Michigan, 2013.” Last modified March 25, 2014. http://www.in.gov/dnr/fishwild/files/fw-LMich_Prey_Fish_Report_Final_2013.pdf
  2. “Status and Trends of Prey Fish Populations in Lake Michigan, 2013.” Last modified March 25, 2014. http://www.in.gov/dnr/fishwild/files/fw-LMich_Prey_Fish_Report_Final_2013.pdf
  3. “Status and Trends of Prey Fish Populations in Lake Michigan, 2013.” Last modified March 25, 2014. http://www.in.gov/dnr/fishwild/files/fw-LMich_Prey_Fish_Report_Final_2013.pdf
  4. “Salmon Population Plummeting in Lake Michigan.” Last modified September 30, 2015. http://www.freep.com/story/news/local/michigan/2015/09/29/salmon-population-plummeting-lake-michigan/73032260/
  5. “Status and Trends of Prey Fish Populations in Lake Michigan, 2013.” Last modified March 25, 2014. http://www.in.gov/dnr/fishwild/files/fw-LMich_Prey_Fish_Report_Final_2013.pdf
  6. “Status and Trends of Prey Fish Populations in Lake Michigan, 2013.” Last modified March 25, 2014. http://www.in.gov/dnr/fishwild/files/fw-LMich_Prey_Fish_Report_Final_2013.pdf
  7. “Status and Trends of Prey Fish Populations in Lake Michigan, 2013.” Last modified March 25, 2014. http://www.in.gov/dnr/fishwild/files/fw-LMich_Prey_Fish_Report_Final_2013.pdf
  8. “Status and Trends of Prey Fish Populations in Lake Michigan, 2013.” Last modified March 25, 2014. http://www.in.gov/dnr/fishwild/files/fw-LMich_Prey_Fish_Report_Final_2013.pdf
  9. http://www.dnainfo.com/chicago/20150430/hyde-park/former-scourge-of-lake-michigan-now-needed-save-salmon
  10. “Salmon Population Plummeting in Lake Michigan.” Last modified September 30, 2015. http://www.freep.com/story/news/local/michigan/2015/09/29/salmon-population-plummeting-lake-michigan/73032260/
  11. “Status and Trends of Prey Fish Populations in Lake Michigan, 2013.” Last modified March 25, 2014. http://www.in.gov/dnr/fishwild/files/fw-LMich_Prey_Fish_Report_Final_2013.pdf
  12. “Status and Trends of Prey Fish Populations in Lake Michigan, 2013.” Last modified March 25, 2014. http://www.in.gov/dnr/fishwild/files/fw-LMich_Prey_Fish_Report_Final_2013.pdf

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