Wetland habitat associations of imperiled Pecos pupfish Cyprinodon pecosensis in a brackish ciÁƒÂ©nega

Authors: Christopher* Hoagstrom, Colleen Caldwell, Damon Peterson

Year: 2015 (xlvii)

Abstract

Ciénegas of semi-desert grasslands are disappearing from the American Southwest, but were once common in the Pecos River valley. Pecos pupfish Cyprinodon pecosensis was endemic to these wetlands, but now persists only in remnant habitats. Habitat fragmentation can create divergent morphotypes among isolated habitats, whereas habitat connectivity appears to allow gene flow, maintaining average morphotypes. We studied habitat association by Pecos pupfish in a connected, diverse brackish ciénega. The U.S. Fish and Wildlife Service National Wetlands Inventory Program mapped habitat types. Over two years, we monitored 52 locations representing six habitat types quarterly. Pupfish occurred in > 60% of collections from permanently watered locations and > 35% of collections from intermittent locations (when watered). It was the most abundant and widespread fish species, but in intermittent sites it had greater differential in frequency of occurrence and dominance (i.e. percent abundance) over other species. Dominance was also positively correlated with specific conductance. Distribution of pupfish among available habitats was even in June, but biased toward vegetated habitats in December. Smaller pupfish (< 20 mm SL) predominated in shallow, salty, intermittent flats and deeper, fresher, permanent ponds with thick submergent vegetation. In contrast, larger pupfish (> 20 mm SL) predominated in shallow, fresher semi-permanent and seasonally flooded marshes. Pecos pupfish is a tolerant, generalist with a dynamic distribution when diverse habitats are available and variable. Habitat connectivity may not only increase gene flow, but also allow populations to maximize seasonal reproduction, recruitment, and survival.