The cold temperatures maintained in the Trinity River are beneficial to fish but may be problematic for foothill yellow-legged frogs. TRRP assesses foothill yellow-legged frog breeding distribution, timing, and survival of egg masses. In 2009, 50 egg masses detected in the mainstem river between Lewiston Dam and the North Fork Trinity River. This was the highest count since egg mass surveys began in 2004, and several of the breeding sites were at restoration sites below Canyon Creek . However, it is still minimal compared to some tributaries. Tributaries and the mainstem with colder water had later onset of egg laying and emergence of smaller froglets when compared to warmer tributaries. While relative abundance on the mainstem has increased over the previous four years, reproductive effort is still substantially less than observed on the South or North Fork Trinity River.
Suggested further reading:
Fuller, T E; Pope, K L; Ashton, D T; and Welsh, H H Jr (2010) Linking the distribution of an invasive amphibian (Rana catesbeiana) [bullfrogs] to habitat conditions in a managed river system in northern California.
Ashton, D T; Bettaso, J B; and Welsh, H H Jr (2010) Foothill yellow-legged frog (Rana boylii) distribution and phenology relative to flow management on the Trinity River. Oral presentation provided at the 2010 Trinity River Science Symposium
Lind, A J; Welsh, H H Jr; and Wilson, R A (1996) The effects of a dam on breeding habitat and egg survival of the foothill yellow-legged frog (Rana boylii) in northwestern California.
Wilson, R A; Lind, A J; and Welsh, H Jr (1991) Trinity River riparian wildlife survey – 1990.