Brief synopses of environmental news from this week. For more information click the links
Freshwater mussel considered for endangered species status
Responding to a petition from the Xerxes Society, the U.S. Fish and Wildlife Service is considering Endangered species status for the western ridged mussel, a mollusk that is found in shallow pools of freshwater creeks in southern British Columbia, Washington, Oregon, Idaho, California, Nevada, and maybe Montana.
It is believed that the mussel historically ranged from the Pacific Northwest to southern California. There is, however, much missing information on where the mussel may have lived before the 1980s, when biologists started to study the mussel in depth. Since 1985 it has been extirpated in much of California, from Eureka south to the Los Angeles area.
Western ridged mussels
Adult western ridged mussels can be about five inches long and are the color of black coffee, with swirls of caramel brown. As adults, western ridged mussels are estimated to live for 20 to 30 years. Being long-lived, their presence in streams makes them good indicators of water quality. As filter feeders, eating plankton and other nutrients from the water column, they also contribute to water quality by controlling nutrient levels.
The larva of freshwater mussels need a host fish. Once the female mussel incubates her eggs, the larva hatch and are released into the surrounding stream. The larva attach themselves to host fish and encyst in the animal’s tissue within two to 36 hours after hatching. The fish then carry the parasites for weeks or months, the mussels dropping from their hosts to the stream substrate once they metamorphose to their adult stage.
The use of host fish is a survival strategy of freshwater mussels, who have sedentary adult lives. While the larva are hitching along, the fish can transport the mussels to new habitats or habitats from which the mussels have been extirpated.
Conservationists and others working with the mussel have identified three species of fish, the pit sculpin, the hardhead, and the tule perch, as hosts for the mussel’s larval stage, but have yet to identify host fish outside of the ranges of these three fish. Lack of information on the western ridged mussel’s current and historical abundance and distribution and a lack of understanding of which host fish species it uses is expected to impede conservation efforts.
Things we do that harm mussels
Dams can be a big problem for mussels. Besides altering water chemistry, dissolved oxygen levels and temperature, dams can lead to the extirpation of host fish species. Dams can also alter the flow regime of a stream or river, disrupting conditions for reproduction. Dredging and altering the river channel can lead to erosion and sedimentation, both harmful to mussels.
Mining can harm mussels and other aquatic organisms when tailings are dumped in rivers. In general, all the contaminants that we throw in rivers from our paper mills, steel mills, tanneries, and other factories harm mussels. Overloads of nutrients that wind up in rivers and streams from agriculture can lead to mortality. Even when we go and restore rivers by removing dams or other such things, if not done wisely, can disrupt the habitat of mussels.
The mussel may have a moderate vulnerability to climate change. Increased intensity of winter storms could increase nutrient runoff, which could degrade and reduce mussel habitat. Warmer stream water in summer could change the availability of their host fish for the mussel’s larval stage.
The state of Washington already considers the mussel a Species of Greatest Conservation Need, which compels the state to develop a conservation plan for the species. In 2010 the Committee on the Status of Endangered Wildlife in Canada listed the mussel as Endangered.
Recently, biologists have witnessed mysterious mass die-offs in a number of rivers, including in the Middle Fork John Day River and Crooked River in Oregon and Washington state’s Chehalis River.
The western ridged mussel is the first species of freshwater mussel to be considered for Endangered status, Freshwater mollusks, which include mussels, are the most imperiled animals in the U.S. (Xerces Society)
Three baby forest elephants caught on camera
Only recognized as a separate species four months ago, African forest elephants are smaller than their savannah dwelling counterparts. Living in forests, they are also far less conspicuous. They are critically endangered, their numbers being reduced because of the illegal ivory trade as well as other human induced factors.
So in the west African country of Guinea, in which the forest elephants number only about two dozen, there was much excitement when a wildlife camera trap collected snapshots of a previously undocumented family of eight, including three young calves, giving hope of recovery for this imperiled species. (Fauna & Flora International)
This is happy news. So let’s enjoy some Baby Elephant Walk!
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