Sunday, November 24, 2013

Protecting Mussels - The Importance and Decline of Mussels.

Earlier in November, the Arkansas Legislative Council Asked Attorney Dustin McDaniel to intervene in the federal government's proposed designation of critical habitat in Arkansas for two mussels with dwindling populations.  There is worry that dwindling populations of the Neosho mucket and rabbitsfoot mussels would have a potentially devastating impact.

It has been proposed to place both mussels under the Endangered Species Act. The critical-habitat designation would cover 2,138 river miles in 12 states, including 800 miles in Arkansas.  Public comment has been opened.  A coalition of groups seeks to reduce the proposed habitat designation in almost half.  The Arkansas Legislative Council recognizes that it would be potentially devastating economically on private, public landowners, farmers, ranchers, timber producers, oil and gas producers, utility providers, county and municipal governments, school districts, irrigation districts and countless small businesses.

A resolution was passed to urge congressional delegation to press the US fish and Wildlife Services to petition the US office of Management and Budget to use a cumulative economic analyses of the critical-habitat designation.  And, to reduce the proposed habitat area.  The legislative council questioned the economic impact on the state.  So, here we are again . . . "man vs. wild".  I appreciate the effort of the federal government to protect this vital species and the state legislation to protect the people and state.  I hope that the state and federal bureaucracy can come to some maximum level of protection for the endangered Neosho mucket and rabbitfoot mussels.

Importance of Mussels
Mussels play a key role in aquatic environments and are considered to be "ecosystem engineers" because they modify aquatic habitat, making it more suitable for themselves and other organisms.
One of the valuable functions performed by mussels is capturing organic matter from the water column when they siphon, processing it to build body and shell, excreting nutrients that are immediately available to plant life and then depositing the remaining organic material to the sediment making it available for other invertebrates and fish to consume. During this feeding process, the mussels "clean" the water they live in by removing phytoplankton and the bacteria and fungi that are attached to the non living organic particles they have removed from the water column. Other undesirable particles and chemicals are bound in the mussels' pseudo feces and deposited on the river bottom.
The mussel's shells provide an important substrate for algae and insect larvae to attach to. When mussels are present in large numbers, they may become underwater gardens that in turn attract fish to feed, including their host fish. Because mussels firmly anchor themselves to the lake or stream bed, they may actually stabilize the lake or stream bottom, thus minimizing the scouring affects of floods and wave action.
Mussels are also an important food source for several different kinds of terrestrial and aquatic animals, including muskrats and raccoons, as well several species of fish. 1

Decline of Mussels
Humans have been impacting the environment
of North America for thousands of years, with
the greatest changes having occurred since
Europeans began colonizing the continent,
especially during the last 100 years. Prior to
European colonization, native agrarian cultures
changed the terrestrial habitat by clearing and
burning forested areas to plant domesticated
crops. The clearing and burning of land
probably changed local aquatic environments
Freshwater mussel shell with button blanks
"punched" out.
through siltation and increased carbon ingress,
with minimal impact on the native fauna.

Indigenous cultures utilized many of the aquatic
natural resources, including freshwater mussels.
They used the shells, meat, and pearls of
freshwater mussels for food, ornaments,
currency, tools, and as a temper in pottery.
However, there is no evidence that any
freshwater mussel species went extinct due to
Native Americans. This is supported by the fact
that many aboriginal middens (refuse piles)
contained shells of species that were still extant
in the early 1900’s, when biologists began
intensively studying freshwater mussels.
However, there is one species believed to have
gone extinct before or about the time
Europeans arrived, since it has only been found
as dead, empty shells. Even though specimens
were found in aboriginal middens, it had
occurred in a stream basin that was impacted by
early settlers which could have caused its

As North America was settled, major cities and
towns were established along rivers and larger
streams at crossings or ports. As these cities
grew larger, the amount of municipal and
industrial wastes released into adjacent streams
increased and caused local declines of
freshwater mussels. As land was cleared and
tilled, the amount of sediment entering the
waterways increased at levels above that of the
Native American farmers.

For the next 60 years, large dam and channel
modification projects were completed
throughout the southeastern U.S. and other
parts of the country. Many large rivers and
small and medium-sized rivers were converted
into a series of lakes, converting river habitat
into lake habitat. Since most freshwater
mussels are/were riverine species, this had a
detrimental effect on many mussel populations.
The last major channelization/canal project was
completed on the Tombigbee River in 1984, the
most unpolluted, longest free-flowing river in
the Mobile Basin at the time, and one of the
most diverse stream systems in North America.
The extinction of mussels probably began 
around 1930, and has been documented as late 
as the 1990’s. However, this is not where 
extinctions will end. Many populations 
occurred in peripheral habitat that may have 
been unsuitable for self-sustaining populations, 
but were refreshed by fish coming into these 
peripheral habitats containing glochidia from 
larger source populations. The glochidia would 
drop off within these peripheral habitats, and 
thus sustain these populations. However, since 
the habitat for the larger source populations has 
been lost or changed into unsuitable habitat, and 
populations have become fragmented, many 
former peripheral populations are beginning to 
disappear. This process continues and where it 
stops, nobody knows. As it now stands, 36 
freshwater mussel species went extinct in the 
20th Century. 
Much of the information contained in this article 
was gleaned from Dr. Wendell Haag’s chapter 
on the extinction of freshwater mussels since 
the Holocene, as found in the book Holocene 
Extinctions (Oxford Press). 

1 Wickline, M 2013 'McDaniel asked to tackle mussels, Arkansas Democrat Gazette
  16 November, pp B1, B2.'

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