Report on the Development of a Refuge Pond for the Sonoyta River Form of the Longfin Dace at the CEDO Research Station, Rocky Point, Sonora, Mexico.

Authors: Chuck Minckley, Alan Berman

Year: 2018

Abstract

The Longfin Dace (Agosia chrysogaster) is a small fish (<10 cm) native to the southwestern United States and northern Mexico. Populations are widespread, and many are reduced, existing in uncertain conditions, impacted by introduced fishes, the over-use of ground water, and climate change which continues to impact freshwater ecosystems. As a result, the population in the Rio Sonoyta, a tributary of the Colorado River, present along the US-MX border, is faced with extinction. This prompted concerned scientists at CEDO, the Intercultural Center for the Study of Deserts and Oceans, in Puerto Penasco, the U.S. Fish & Wildlife, Arizona Game and Fish Department, and non-governmental environmental groups to establish several new populations in man-made refuge ponds in and around Puerto Penasco, Sonora, Mexico. Species that evolve in habitats with limited predation are predicted to have reduced investment in antipredator traits, such as the production and detection of chemical alarm cues. Our study focused on epithelial club cells, which are presumed to contain injury-released alarm cues and are present in numerous fish taxa. This evaluation was carried out on four desert fishes in the Cyprinodontiformes; Pahrump Poolfish, Empetrichthys latos latos, White River Springfish, Crenichthys baileyi, Amargosa Pupfish, Cyprinodon nevadensis, and White Sands Pupfish, Cyprinodon tularosa. We also sampled three cyprinid species: Hot Creek Valley Tui Chub, Suphateles bicolor ssp., and two non-insular species, Fathead Minnow, Pimephales promelas, and Zebrafish, Danio rerio. Club cell densities per mm2 of epithelial tissue differed significantly among species (X2 = 91.81, df = 6, p < 0.0001), and pairwise comparisons revealed no differences among Cyprinds or among Cyprinodontiformes. As expected, Fathead Minnows and Zebrafish displayed relatively high densities of club cells (446.5 ± 100.3; 310.4 ± 51.3; mean ± SE, respectively). By contrast, mean club cell densities were low for Pahrump Poolfish (17.1 ± 8.5), White Sands Pupfish (17.1 ± 9.0), Amargosa Pupfish (1.0 ± 0.6), and White River Springfish (0.0 ± 0.0). In comparison, however, the Hot Creek Valley Tui Chub, a desert cyprinid, displayed club cell densities similar to non-insular cyprinids sampled (137.9 ± 56.3). Thus, phylogeny, and not locality or history of predation, may be the primary driver for expression of club cells and antipredator behaviors present in populations.