Author: oppliger.6

At approximately 9,940 square miles, Lake Erie is an incredibly important component of the Great Lakes¹. Whether it is due to the lake’s aesthetic value or its economic importance, Lake Erie is an ecosystem that is heavily monitored and researched. This monitoring has revealed a couple of very concerning trends that seem to be intensifying as a result of anthropogenic disruption and alteration.  Regardless of whether it is the well-known algae blooms caused by increasing levels of dissolved phosphorous finding its way to the lake from agricultural and urban management practices or the introduction of invasive species and their effects on native fish populations, humans are disrupting the natural ecosystem of the lake at concerning levels². One of the monitored aspects of the lake is the temperature of the water within the lake. Studies have shown that water temperatures have become warmer over the past 90 years⁶. Although the warming temperature is rather inconsistent in nature, resulting in up and downs in temperature on a year-to-year basis, linear trend lines indicate that water temperatures are getting warmer (refer to figure below). Water temperature readings are reaching all-time highs in the summer months and increased winter water temperature are resulting in decreasing ice cover⁴. Although a topic for debate, these increases in water temperature are largely a result of increased air temperatures resulting from climate change⁴. Understanding how these changes to the water temperature of Lake Erie may effect the organism within the lake is essential to future management and conservation strategies.

Short, Warm Winters Affect Successful Reproduction of Yellow Perch

The Lake Erie Yellow Perch (Perca flavescens) is a staple fish found in Lake Erie due to its relative importance ecologically, as well as, economically. With a harvest limit of 11.081 million pounds of total allowed catch in 2014, one can easily understand the importance of understanding the Yellow Perch physiological demands in order to best manage this species⁵. The Yellow Perch has a set of preferred reproductive traits and procedures that have proven essential to maintaining a healthy native population in Lake Erie. Female Yellow Perch develop ovaries in the cold winter months and spawn during the spring months³. With this in mind, studies have been conducted in order to understand how increases in water temperature resulting from warmer, shorter winters could affect the spawning success of this species. Results indicate that there are two main disruptions that arise from these shorter and warmer winter weather patterns. First, it seems that shorter and warmer winters are causing reduced size in Yellow Perch eggs, yielding smaller and less successful larvae³. In turn, this means that a reduced number of juvenile fish are advancing to the next life stage, potentially resulting in the reduction of overall surviving adult Yellow Perch in the lake. In addition, the spawning time of the Yellow Perch seems to be earlier than that of what it is typically seen under normal winter lake conditions. As seen in the figure below, spawning periods occurring around two weeks to a month earlier in shorter and warmer winter when compared to the typical longer and colder winters³. These unconventional spawning periods lead to increased food scarcity for surviving Yellow Perch juveniles, further impacting survival rates⁴. The study, run in an experimental setting and confirmed by actual lake conditions, show that the Yellow Perch is unable to adapt to the changing environmental conditions³.

 

Lake Erie Yellow Perch Population Dynamics & Impacts of Continuing Climate Change

            Research has confirmed that Yellow Perch are negatively impact by shorter and warmer winters resulting from climate change, therefore it is imperative to continue researching just how fast this species is able to adapt in order to avoid a drastic population crash. The figure below indicates that Ohio temperatures will continue to increase with the consequences occurring whether we decrease carbon emissions or not⁷. Since the Yellow Perch is such a prominent species within the seven-billion-dollar fishing industry in the Great Lakes, a decrease in the perch population or a potential behavioral response to move out of the warmer regions of the lake could have monumental consequences to regional economies⁴. In addition to Yellow Perch, further research as to how other species of fish may be impacted by these warming trends could inform conservation efforts for a wide range of operations, not just recreational and commercial fishing.      

References:

1. Lake Erie Facts and Figures. Retrieved November 1, 2017, from http://www.great-lakes.net/lakes/ref/eriefact.html

2. Michalak, Anna M. et al. “Record-Setting Algal Bloom in Lake Erie Caused by Agricultural and Meteorological Trends Consistent with Expected Future Conditions.” Proceedings of the National Academy of Sciences of the United States of America16 (2013): 6448–6452.

3. Farmer, T.M., Marschall, E.A., Dabrowski, K., Ludsin, S.A. (2015). Short winter threaten temperate fish populations. Nature Communications, 6 (7724)

4. Linn, M (2015, September 20) Climate change threatens perch, other warm-water fish. November 1, 2017, retrieved from http://greatlakesecho.org/2015/09/30/climate-change-threatens-perch-other-warm-water-fish/

5. Golowenski, D (2014, April 6) Lake Erie perch, walleye bag limits to stay same. Retrieved November 2, 2017, retrieved from http://www.dispatch.com/content/stories/sports/2014/04/06/lake-erie-perch-walleye-bag-limits-to-stay-same.html

6. Frankson, R., K. Kunkel, S. Champion and D. Easterling, 2017: Ohio State Summary. NOAA Technical Report NESDIS 149-OH,4 pp.

7. https://statesummaries.ncics.org/oh

 

The largest indigenous fish found within the Greats Lakes Basin is the Lake Sturgeon (Aciperser fulvescens). Lake Sturgeon have flourished in their natural habitat since the glaciers that shaped the basin we know today retreated and gave way to the Great Lakes. However, this once booming population found throughout the majority of the Great Lakes Basin, has declined rapidly since the late 1800s and early 1900s. Today, the Lake Sturgeon is recognized by the American Fisheries Society as either endangered, threatened, or of special concern in 19 of the 20 states throughout its range⁵. Overexploitation of the Lake Sturgeon due to its importance in commercial fisheries and sport fishing, as well as, habitat alteration in the streams and rivers that the Sturgeon rely upon for spawning are considered two of the most influential drivers of the current status of the fish¹. Current management practices aimed at the recovery of the Lake Sturgeon have proven challenging due to several life history and reproductive traits associated the fish. Lake Sturgeon prefer clean gravel shoals and stream rapids during spawning². In addition, the Lake Sturgeon requires many years to reach sexual maturity, have slow growth rates, and intermittent spawning cycles that make population restoration progress difficult to track in small periods of time³. Understanding these traits and how they alter management, on top of controlling exploitation, has provided the framework guiding our current recovery practices. This framework has offered a hopeful outlook into the future of Lake Sturgeon populations.

Past Management Practices:

It is important to understand how the Lake Sturgeon population declined from its historical abundances to being classified as endangered or threatened across the majority of its range. Between 1879 and 1900 an estimated 4 million pounds of Lake Sturgeon were harvested annually⁵. Lake Sturgeon populations were decimated throughout the basin and many of the commercial and sport fishing operations struggled to take in sustainable numbers of catch. Management of Lake Sturgeon exploitation began to spread in the early 1900s as many states began to regulate commercial and recreational fishing. With these regulations in place, Lake Sturgeon population status was widely unknown for vast majority of the last century. Along with overexploitation, human induced destruction and fragmentation of spawning habitat greatly hindered that ability of populations to recover. The installation of dams throughout the tributaries of the Great Lakes prohibited adult Lake Sturgeon from reaching preferred spawning sites located in streams and rivers. Land use, such as extensive deforestation and agricultural development, gave way to increased erosion and siltation that covered these the once prime gravel spawning habitats found in the tributaries³. Documented research of increased water pollution causing low hatching success and decreased survival of young Sturgeon further enhanced the population crash illustrated below¹. These anthropogenic stressors act as the primary source of disturbance in natural reproducing populations of Lake Sturgeon and, as stated earlier, mitigating these disturbances has been the main goal of recovery initiatives.

Current Management Practices:

The Great Lakes Restoration Initiative (GLRI) consists of over 40 multi-agency partnerships whose mission is to preserve, protect, and recover populations of Lake Sturgeon in the Great Lakes Basin¹. Funding aimed at reestablishing naturally spawning Lake Sturgeon populations, in addition to hatchery based populations, have initiated many of current recovery projects found in the Great Lakes. The combination of closed seasons, catch limits, and gear restrictions have nearly eliminated all harvesting and recreational exploitation from the Great Lakes in both the United States and Canada. Increased knowledge of habitat fragmentation caused by the installation of dams has resulted in efforts to remove dams that are no longer in use. On top of removal efforts, fish passages through and around barriers that prevent upstream travel have been implemented in existing Sturgeon streams, enhancing the opportunity for Sturgeon to reproduce naturally through many generations. Stream-side rearing facilities have been installed in the majority of the 26 tributaries that currently support Sturgeon¹. Rehabilitation efforts and rearing facilities will stock approximately 25,000 Sturgeon each year in an effort to enhance the existing populations basin-wide⁴. Implementation of human-constructed reefs systems that resemble native stream beds, consistent monitoring of spring run numbers, and consistent communication and monitoring of water usage by hydroelectric power plants are all considered essential for health populations^1,3.

 Looking into the Future:

            As we look into the future of Lake Sturgeon populations in the Great Lakes Basin, there a number of successful operations that have populations trending in the right direction. Many of the stocking and recovery programs initiated in recent years have existedlong enough for reproduction to occur, yet strategies are full go. Recovery efforts in the New York ‘s Oneida-Lake system and Oswegatchie River have existed long enough for reproduction to occur. Reports indicate that not only are Lake Sturgeon reproducing naturally within these systems, but they are displaying unparalleled growth rates⁶. Lake Michigan is reporting increasing growth rates as a result of enhanced water quality⁶. The St. Louis river, which has been extensively cleaned and stocked with thousands of fry and fingerlings beginning in 1983, is a shining example of the success of current recovery efforts⁶. Building on these success stories and continuing to spread awareness will aid our efforts to return these magnificent fish to their once historic populations numbers.

 

References:

1. Schram, S. T., Lindgren, J., & Evrard, L. M. (1999). Reintroduction of lake sturgeon in the st. louis river, western lake superior. North American Journal of Fisheries Management, 19(3), 815-823.
2. Auer, N. A. (1999). Population characteristics and movements of lake sturgeon in the sturgeon river and lake superior. Journal of Great Lakes Research, 25(2), 282-293
3. Smith, K. M., & King, D. K. (2005). Movement and habitat use of yearling and juvenile lake sturgeon in black lake, michigan. Transactions of the American Fisheries Society, 134(5), 1159-1172
4. Holtgren, J. M., Ogren, S. A., Paquet, A. J., & Fajfer, S. (2007). Design of a portable streamside rearing facility for lake sturgeon. North American Journal of Aquaculture, 69(4), 317-323
5. Lake Sturgeon Fact Sheet. September 25,2017, from https://greatlakesinfrom.org/knowledge-network/532
6. Williams, T., Miller, M., David, S., Hausheer, J. E., & Sankar, C. L. (2016, February 22). Recovery: Saving Lake Sturgeon, an Ancient Fish with a Bright Future. Retrieved September 27, 2017, from https://blog.nature.org/science/2016/02/15/recovery-saving-lake-sturgeon-ancient-fish-bright-future/