During a partial draining of the San Antonio River along the River Walk on Monday, biologists found giant invasive snails according to My San Antonio

The San Antonio River Authority is in the process of draining the river for the first time in four years to remove the Amazonian apple snails for the riverbanks.

The species are not native to the area and were first seen back in October. River Authority workers removed nearly 80 of the snails' pink egg sacs which can hold thousands of eggs, back in December. 

50 snails were removed on Monday. 

According to biologist Chris Vaughn, the snails take away food from the river's native species and are "almost certainly" the result of them being released from personal aquariums because they are typically sold at pet shops.