Comparison of invertebrate sampling methods in the Middle Rio Grande

Background/Question/Methods Complementary sampling methods are sometimes necessary to gain accurate representation of aquatic invertebrate communities.  In this study, we used two techniques to obtain both benthic and pelagic taxa in slow-flowing areas of the Rio Grande in New Mexico. The first technique was an epibenthic corer, pelagic tube, and dipnet used in a 0.25m² throw trap and the second technique was a stovepipe sampler. We then evaluated whether relative abundance and diversity of invertebrates differed between the two techniques using 23 pools at five different locations in the Middle Rio Grande. We also determined if there was a bias in the size of the organisms captured in any collection method.

Results/Conclusions

In general, the stovepipe captured as great a diversity of epibenthic invertebrates, compared to the corer and dipnet, but more diversity of invertebrates than the pelagic tube used within the throw trap. However, the dipnet was collected lower numbers of microinvertebrates compared to the other sampling methods. The epibenthic corer was a more efficient method of processing invertebrate samples - both in the field and in the laboratory - and captured more abundance than the other collection methods.  However, we recommend that dipnet samples be taken as a complement to the epibenthic corer to more fully reflect the species richness of the invertebrate community in the Rio Grande.