200 Years. 200 Stories. Story
104: “A Minnow's Life History
Micrographs of fish scales belonging to the Rio Grande silvery minnow (Hybognathus amarus). The scale on the left is from a specimen collected by Cope and Yarrow in 1874. The one on the right is from a recently collected specimen. The bands visible in these scales, which are analogous to tree-rings, can be used to age the fish.
A Minnow's Life History
The endangered Rio Grande silvery minnow (Hybognathus amarus) is the only remaining species in a group adapted to the flow pattern of the Rio Grande. Ecologists like the Academy’s Dr. Richard Horwitz hope to protect this endangered species by learning more about its life cycle. Controversy about the life span of this species relates to managing river flows adequate to sustain the species.
In 2009 and 2010, Rich and his colleagues collaborated with researchers at the University of New Mexico on a minnow aging study. Colleagues in New Mexico collected minnow samples, which they sent to the Academy for analysis. Rich and colleagues examined the fishes’ scales and ear bones to determine their ages, and they compared historic samples taken from the area in 1874 to the recent samples to understand how the lifespan of the fishes changed over time. They concluded that the fishes have a short life span which is not related to environmental modifications.
Now part of the collection of the Smithsonian Museum of Natural History, the historic samples have an exciting connection to the Academy. The samples were collected during the 1874 Wheeler Expedition to the American West by Academy member H.C. Yarrow and famed paleontologist and Academy scientist Edward Drinker Cope. Charged with conducting extensive topographical and faunal surveys in areas including the Rio Grande, Cope was so excited to see the badlands across the river that he scurried off to hunt for fossils, leaving Yarrow to collect the fish. Still, Cope wrote descriptions of the fish for the United States Geological Survey (Volume Five). You can read more about Cope in our 200 Stories.