Jason Hwan




University of California, Berkeley, Environmental Science, Policy, and Management, Ph.D. Candidate (Advanced to candidacy, May 2010)

California State Polytechnic University, Pomona, Biology, B.S. Magna Cum Laude, 2007

Research Interests

Freshwater Ecology, Fish Ecology, Conservation Biology, Intermittent Streams

Research Description

Mediterranean climate regions are characterized by wet winters and dry summers and, as a result, Mediterranean streams contract greatly during the summer low flow period. Under these conditions, small streams can become fragmented as shallow riffle habitats dry leaving behind isolated pool habitat. I have been studying the ecology of one such “intermittent” stream in the Point Reyes National Seashore (Marin County, CA) across four recent summer drought seasons. My study aims to quantify the effects of summer drought on stream habitat availability, fish ecology, and ecosystem processes. In particular, I have monitored habitat availability and stream connectivity to better understand changes that occur in the physical environment across the summer drought season. Additionally, I am assessing the effects of stream contraction and fragmentation on the growth, survival, and movement of juvenile salmonids. To do this, I have followed the fates of individually-marked salmon and trout across the summer drought season. In particular, using PIT-tags and a hand-held portable antenna, I have monitored the movement and survival of juvenile trout and salmon each week across the summer dry season to pinpoint periods of elevated movement or mortality. Lastly, at the ecosystem level, I am monitoring the influence of summer drought on leaf litter breakdown and algal productivity to better understand how drought influences the base of the stream food web. These data will improve our understanding of habitat requirements for fishes rearing in intermittent streams and help identify low flow thresholds for sustaining juvenile salmonids over the summer drought season, which has implications for human water use in salmon watersheds.

Selected Publications

Moore, J.W., Carlson, S.M., Twardochleb, L., Hwan, J.L., Fox, J.M., Hayes, S.A. 2012. Trophic tangles through time? Opposing direct and indirect effects of an invasive omnivore on stream ecosystem processes. PLoS ONE 7: e50687 (PDF).

Ball, J.E., Diver, S.W., Hwan, J.L. 2009. Evidence of streamflow and sediment effects on juvenile coho and benthic macroinvertebrates of Lagunitas Creek and San Geronimo Creek, Marin County, California. UC Berkeley: Water Resources Center Archives (PDF).

Honors and Awards

Edward A. Colman Fellowship in Watershed Management, ESPM                        Spring 2013

American Fisheries Society Equal Opportunities Section Travel Award                Sept. 2011

National Science Foundation Graduate Research Fellowship                               2009-2012

Contact Information

Email: jhwan@berkeley.edu

Office: 326 Mulford Hall

Office Phone: 510-643-9688


Research Group(s)

Mailing Address

Dept of Environmental Science, Policy, & Management
UC Berkeley
130 Mulford Hall #3114
Berkeley, CA 94720