FAT THREERIDGE (AMBLEMA NEISLERII)
The Environmental Issue: Damming, Dredging, and everything else.
The fat threeridge is one of many mussels that is critically endangered due to habitat degradation. Freshwater mussels like the fat threeridge are constantly on the defense against an increasing human population and development on the land surrounding the rivers they occupy. The paramount threat to the fat threeridge is the impoundment or damming of their waterways. You may recall this term from the Topeka shiner blog because this also affects many freshwater fish populations as well as entire ecosystems. Rivers and other waterways are impounded to provide services like a fresh water supply, flood control, and energy from hydropower. One negative is that in creating a blockade in the water system, you slow the current of the waterway and cause sediments to build up. This is detrimental to mussels because it covers the mussels potentially causing suffocation. Additionally, dams cause habitat fragmentation thus causing fat threeridges to become separated from other mussel populations, new dispersal habitat, and the algae and host fish they need to survive.
A couple of scientists back in the 1950s gathered data introducing us to this phenomeon in Dead Lake, Alabama. They found an exceptional subpopulation in this area with reported “densities of 0.9 to 1.4 specimens per square foot along a 600+ foot stretch of shoreline.” Then in 1960, a low-head dam was installed and subsequently removed in 1987. The dam filled Dead Lake with unnaturally high levels of sediment that couldn’t be reversed. Unfortunately, the fat threeridge is now extirpated from Dead Lake.
As one could expect, river dredging also threatens fat threeridge habitat because the act literally obliterates the riverbeds they live in. But, wait, that’s not all that threatens the fat threeridge. Recently, scientists have noted that an invasive species of clam, the Asian clam, may be out-competing the native mussels in certain areas. On top of all that, the introduction of the flathead catfish may also be hitting the fat threeridge populations hard as they may feed on mussels and the host fish species. Additionally, as in most freshwater systems, the fat threeridge must fight for survival against pesticides, herbicides, and other chemical pollutants entering the water because as a filter feeder, they are ingesting the chemicals directly into their bodies. In some areas, such as in the lower Flint River basin, biologists are looking into the possibility of an inadequate water flow that could be the cause of the fat threeridge disappearance. So in sum, this mussel has almost every environmental issue stacked again it.
In 1998, the fat threeridge was listed as an endangered species federally and today it has attained the designation of a critically endangered species because of its rapid population decline, although its likely the populations had been declining long before that. In current years, this designation was chosen because a recent drought destroyed much of the mussel’s habitat due to a lack of water. Even with the recent title promotion to critically endangered, the fat threeridge still hasn’t been able to drum up a huge following for its protection. One report analyzed that it may be a result of the boring and camouflage appearance or its “disappointing” motor skills making them particularly monotonous to nonbiologists.
Professionals agree that surveys have revealed an alarming rate of disappearance at historic sites. One study conducted in the 1990’s only located fat threeridge at 11 of 324 historically occupied sites. The most recent studies have even proposed that the Flint River population may be completely extirpated. If this is in fact the case, then fat threeridges have completely vanished from Georgia altogether.
State and federal agencies have called for an increase in research on the species as it is unclear what exactly is the best management decisions to be made in ensure the protection of a species facing a plethora of environmental issues. Some have also suggested repairing riverbank buffer zones to prevent erosion into the water which, in addition to river impoundment, has been a large source of sediment accumulation in some rivers.
If you are looking for ways to lower your impact on river species like the fat threeridge, keep in mind that all land, regardless of where you live, is part of a watershed that drains into some waterway. Easy ways to reduce your impact include: using less (or no) fertilizers and chemicals on your yard, making sure any product you plan on putting done the drain is waterway safe (check for organic and sulfide-free tooth pastes, shampoos, and other health products), and as I’ve said before, it is always a good idea to reduce your water use in any way that you can.
If you would like to check out more animals on the Endangered Species List on your own, please visit the U.S. Fish and Wildlife Service’s list of Threaten/Endangered Species in the U.S. and Foreign Countries.
References: Bogan, A.E. Amblema neislerii. The IUCN Red List of Threatened Species 1996: [Online] 1996. http://dx.doi.org/10.2305/IUCN.UK.1996.RLTS.T1076A3214210.en (accessed Apr 3, 2017). Wisniewski, J. Fat threeridge (Amblema neislerii). Georgia Dpt. of Nat. Resources: Wildlife Resources Division. [Online] 2008 http://www.georgiawildlife.org/sites/default/files/uploads/wildlife/nongame/pdf/accounts/invertebrates/amblema_neislerii.pdf (accessed Apr 3, 2017). Florida Fish and Wildlife Conservation Commission. Fat Threeridge (Mussel). Florida Fish and Wildlife Conservation Commission. [Online] 2011 http://myfwc.com/media/2211661/Fat-Threeridge.pdf (accessed Apr 3, 2017). Images: Image 1: Miller, M. Weird Nature: Flexing Mussels. http://19mvmv3yn2qc2bdb912o1t2n.wpengine.netdna-cdn.com/wp-content/uploads/2012/05/fat-threeridge-mussel-cgs.jpg (accessed Apr 3, 2017). Image 2: Biggins, D. Amblema plicata. https://upload.wikimedia.org/wikipedia/commons/5/57/Amblema_plicata.jpg (accessed Apr 3, 2017). Image 3: Schooner, J. Mehoopany Creek Low-head Dam, https://i.ytimg.com/vi/3g6n0O7T13o/maxresdefault.jpg (accessed Apr 7, 2017). Image 4: Lamprey Surveys. Politically Motivated Dredging On The River Bandon, Co. Cork; Destruction. https://lampreysurveys.files.wordpress.com/2014/02/bandon-drainage-scheme.jpg (accessed Apr 7, 2017). Image 5: Rizzardi, K. Last Time To See? https://s-media-cache-ak0.pinimg.com/originals/d0/95/d4/d095d4e8bf395a279c762276340e9c64.jpg (accessed Apr 7, 2017). Image 6: Unknown. Earth Conservation Corps WP Contest. http://ecc1.org/wp-content/uploads/2016/03/river-of-hope.jpg (accessed Apr 7, 2017).