Tuesday, August 2, 2011

Snorkeling Day

Last Friday, we all headed out for some summer snorkeling in the Hiwassee River to celebrate the last day of our high school summer volunteer, Caroline. The access point was a bit remote (lots of time on gravel roads!), but it was a pleasant day and everyone saw many beautiful native fish species, including tangerine darters (Percina aurantiaca), mirror shiners (Notropis spectrunculus), whitetail shiners (Cyprinella galactura), and logperch (Percina caprodes). Despite the isolation of the area, it was still being impacted by aquatic nuisance species. We saw two invasive species, redbreast sunfish (Lepomis auritus, discussed here), and Asian clams (Corbicula fluminea).

Asian clams are native to Southeast Asia and parts of Russia. They were first seen in the United States in 1938 and have spread to almost 40 states since then. They were first brought into the country by immigrants using it for food, but now the main pathways of spread are bait buckets and intentional release.

Asian Clam (Corbicula fluminea). From http://nas.er.usgs.gov/XIMAGESERVERX/2005/20051110110923.jpg

Once the clams are established in an area, they outcompete native invertebrates for habitat and food. They also spread very quickly, in part because they are hermaphroditic, possessing both male and female reproductive organs. Asian clams are capable of self fertilization, and a single clam can produce seventy thousand offspring per year. The larvae are free swimming, an advantage over the native mussels whose larvae must attach to fish to disperse. Asian clams also cause economic damage through biofouling. In a very short time, pipes can become clogged with these small clams, and they have cost the U.S. millions of dollars in pipe repair or replacement.

So we did our part for native species on Friday—we opened up a few Asian clams to feed to the tangerine darters and logperch swimming around us! It was quite the feeding frenzy.

No comments: