Coho and Steelhead Smolt Outmigration from the San Geronimo Valley, Marin County, 2009
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Coho and Steelhead Smolt Outmigration from the San Geronimo Valley, Marin County, 2009 Prepared by Christopher Pincetich, Ph.D., SPAWN Watershed Biologist Todd Steiner, M.S., SPAWN Executive Director Paola Bouley, M.S., SPAWN Conservation Program Director Ssssssssssssssssss Salmon Protection Salmon Protection And Watershed Network And Watershed PO Box 370 • Forest Knolls, CA 94933 Network Ph. 415.663.8590 • Fax 415.663.9534 PO Box 400 • Forest www.SpawnUSA.org Knolls, CA 94933 i Salmon Protection and Watershed Network (SPAWN) Coho and Steelhead Smolt Outmigration from the San Geronimo Valley, Marin County, 2009 Table of Contents Abstract…………………………………………………………………………………………………...…1 Introduction……………………………………………………………….…………………….…………...1 Lagunitas Coho………………………………………….…………………………...…………...1 Lagunitas Steelhead………………………………………….…………………….…….……...2 San Geronimo Valley Headwaters………………………………………….….….…………...3 Salmon Protection and Watershed Network (SPAWN)- Background…..…………….….....4 Methods………………………..……………………………………………………………………………4 Smolt Trap Design and Location ……………………………………...………………….……5 Daily Monitoring…………………………………………………………………………..………6 Smolt Scale Collection and Age Estimation Analyses…………………………………..……7 Data Analyses……………………………………………………………………………….……7 Fulton Condition Factor……………………………………………………………..…..…….…8 Results……………………………………………………………………………………..……...…...……8 Coho Salmon………………………………………………………………………..…..……...…8 Steelhead……………………………………..……………………………………..…..…….…12 Other Aquatic Organisms ……………………………………..………………………..…...…15 Discussion………………………………………………………………………………………….…...…17 San Geronimo Valley Coho Smolt Production…………………………………..……..…....17 San Geronimo Valley Steelhead Smolt Production………………………………………… 19 San Geronimo Valley Trends…………………………………………………………………. 20 Acknowledgements…………………………………………………………………………….…………21 References……………………………………………………………………………………………...…22 ii Salmon Protection and Watershed Network (SPAWN) List of Tables Table 1. Summary of coho smolt captures from San Geronimo, Arroyo, and Larsen Creeks….…9 Table 2. Summary of coho smolt measurements from the San Geronimo Valley Creek…………10 Table 3. Table 3. Summary of total steelhead smolt captures from San Geronimo, Arroyo, and Larsen Creeks…………………………………………………………………………………………….13 Table 4. Summary of measurements from San Geronimo Creek steelhead smolts with smoltification code 4. …………………………..…………………..…………………………..….….…13 Table 5. Summary of measurements from San Geronimo Creek steelhead parr with smoltification codes 2-3. ……………..…………………………………………….…………………………………....14 Table 6. Summary counts of native, non-salmonid species recovered in smolt traps……...……..15 Table 7. Summary counts of non-salmonid, non-native, invasive species that are predators on salmon eggs and fry that were recovered in smolt traps………………………………………..……16 Table 8. Summary of coho smolt population estimates from the San Geronimo Valley (SGV) and upper Lagunitas Creek Watershed (LCW). ……………………………………..………………….…17 List of Figures Figure 1. The Lagunitas Creek watershed is located north of San Francisco Bay in Marin County, California, and originates near the top of Mount Tamalpais and flows north to Tomales Bay. The San Geronimo Creek watershed is the upper, un-dammed headwater tributary that joins Lagunitas Creek 7.2 km downstream from its origins on White’s Hill……………………...…………3 Figure 2. The San Geronimo Valley sub-watershed contains twelve main tributaries that support coho salmon or steelhead. The location of the three outmigrant smolt monitoring stations is shown along San Geronimo, Arroyo, and Larsen Creeks…………………………………..…………5 iii Salmon Protection and Watershed Network (SPAWN) Figure 3. The smolt traps were constructed as a combination fyke net/pipe trap design intended for larger creeks (A). Smolts were measured (B) and weighed (C) while immersed in cold creek water to minimize handling stress. …………………………………………………………………….…6 Figure 4. Outmigrant coho smolt captures, capture probability, and population estimates from 2009 monitoring in San Geronimo Creek……………………...………………………………….……10 Figure 5. Salmonid measurements from 2009 San Geronimo Creek monitoring of fork length and wet weight plotted for coho smolts …………………………….……………………………………….11 Figure 6. Length frequency histogram of coho smolts size classes captured from both San Geronimo and Larsen Creek smolt traps. …………………………….…………………………….…11 Figure 7. A representative coho smolt scale sample, under 10x magnification, that indicates an estimated age of 2+ years old for the fish……………………………………..………………………12 Figure 8. Outmigrant steelhead smolt captures, capture probability, and population estimates from 2009 monitoring in San Geronimo Creek………………………………………………....…….14 Figure 9. Salmonid measurements from 2009 San Geronimo Creek monitoring of fork length and wet weight plotted for steelhead smolts (A) and parr (B)……………………………………………14 Figure 10. In-stream creek temperatures during the outmigration monitoring were recorded at each smolt trap using an in situ HOBO device at 15 minute intervals in (A) Arroyo, (B) Larsen, and (C) San Geronimo Creeks. ……………………………………………….………………………16 Figure 11. Annual cumulative rainfall as measured in San Geronimo Creek just upstream of the smolt trap in Lagunitas indicates rainfall averages below annual averages since 2006, evidence of current drought conditions observed throughout the SGV watershed (top). Monthly rainfall before, during, and after the salmonid smolt migration for 2009(bottom)………………..………..18 iv Abstract Smolt production of coho salmon and steelhead in the San Geronimo Valley (SGV) sub- watershed, the un-dammed headwaters of the Lagunitas Creek Watershed (LCW) in Marin County, California, was determined through outmigrant trapping during the spring months March- June 2009 by the Salmon Protection and Watershed Network (SPAWN). SPAWN biologists made daily observations and measurements at three fyke-net fish traps, one on San Geronimo Creek just before its confluence with Lagunitas Creek, and two on smaller tributaries to San Geronimo Creek. Mark and recapture analysis was used to estimate the number of coho salmon or steelhead smolts migrating toward the ocean. Coho smolt captures and population estimates calculated using DARR 2.0 software from the San Geronimo trap were the second largest in 4 years of monitoring, with 362 coho captures resulting in a population estimate of 2,499 (±370) individuals. Tributary traps produced small numbers of coho smolts, and for the first time in 4 years, no coho fry were observed in the traps. Scale samples from 11 large coho smolts from Larsen and San Geronimo Creeks were examined and indicated the presence of 9 age 2+ coho smolts, suggesting smolt migration in 2008 was inhibited by barriers to outmigration, possibly exacerbated by the driest spring and summer on record in Marin since 1879. Similar annual steelhead population responses were seen with 208 captures from San Geronimo Creek resulting in an estimated population of 1,625 (±409), the second largest population observed in the 4 years of monitoring. The value of small tributaries such as Larsen Creek was demonstrated by the 48 steelhead smolts observed outmigrating this year, almost double the numbers ever recorded from this creek. A total of 664 steelhead fry were observed from all three traps, much lower than previous years. Based on the results of monitoring conducted by MMWD, Stillwater Sciences, and SPAWN from 2006-2009, the San Geronimo Valley watershed is responsible for rearing an average of 40% of the total coho smolt population in the upper Lagunitas Creek watershed. Introduction The Lagunitas Creek watershed (LCW) of Marin County supports the largest-remaining, documented wild population of endangered Central Coast coho salmon (Oncorhynchus kisutch) in California (Moyle et al., 2008). The Central California Coast Evolutionarily Significant Unit (ESU) of coho salmon has been listed as endangered in the State of California and under the U.S. Endangered Species Act (ESA) since 2005. The LCW also supports a population of Central California Coast ESU steelhead (Oncorhynchus mykiss) that has been listed at threatened under the ESA since 2006. Lagunitas Coho The LCW occupies 281.85 km2 (69,646 acres) in Marin County and contains 56.32 km (35 miles) of ESA-listed coho salmon coho bearing streams and 59.55 km (37 miles) of steelhead streams 1 Salmon Protection and Watershed Network (SPAWN) (NOAA SWFS, 2008). Coho salmon normally have a fixed three-year birth to death life cycle, producing three separate year classes each of which can be considered essentially a separate population because there is little mixing among year class lineages. Juvenile coho salmon emerge from redds in late winter to early spring and spend over one year in the stream before undergoing a physiological and morphological smoltification process and migrating to the ocean in the following spring. During smoltification, their scales slough, vertical parr marks along the lateral line fade and become a uniform silver color, their length increases in proportion to their girth, and they begin physiological adaptations to prepare them for life in seawater. They spend about 1.5 years in the ocean and return to spawn in the late fall to early winter three years from when they were spawned. The regular occurrence of “jacks” that return to spawning grounds as 2-year old males in limited numbers, and the occasional juvenile that holds over in their natal stream for 2 winters, are known exceptions to the usual fixed life-cycle of coho salmon. Due to the relatively rigid