Fishing for Answers: How to Save the Rio Grande Silvery Minnow

Tom Turner photo

A rose may be a rose, but a minnow is not necessarily a minnow, at least when we're discussing reproduction of an endangered species. And with yet another year of low water on the Rio Grande, artificial propagation is certain to play an important role in efforts to save the Rio Grande Silvery Minnow from extinction.

But rearing fish in hatcheries is more complicated than just putting males and females together and hoping for the best. In captive populations, all too often only a few fish actually do the breeding. With so few individuals contributing to the next generation, genetic diversity declines. Populations without sufficient genetic variability are less stable over time, so adding hatchery-reared fish that already have limited diversity doesn't help the wild population much. Associate Professor THOMAS F. TURNER is helping to alleviate this problem by determining the extent of genetic diversity in both wild and captive populations. Turner first developed specific genetic markers, including both microsatellites and mitochondrial genes, that he could use to assess levels of diversity in various minnow populations. For the past several years he has been obtaining such data, allowing Turner to make recommendations to hatchery officials about how they should proceed. Once they are returned to the wild, fish with higher levels of diversity are more likely to reproduce successfully, helping to stabilize the population decline of this endemic species.

In 2003, Turner and members of his laboratory collected for analysis fin clips from more than 300 wild minnows. They also sampled more than 400 fish reared at the Albuquerque BioPark and at the Dexter National Fish Hatchery. Now that these fish have been returned to the river, Turner will continue to monitor genetic diversity in wild populations to determine the impact of the returnees. His hope is that by returning a genetically diverse group of fish, some of the variability that has been lost in wild populations may be regained. If such increased genetic diversity translates into population growth, this is one fish story that might have a happy ending.