Juvenile salmonid rotary screw trap data from Battle and Clear Creeks, Shasta and Tehama Counties, California.

Clear Creek The U.S. Fish and Wildlife Service continued its juvenile salmonid
monitoring project in Clear Creek, Shasta County, California, that
began in December 1998 using a rotary screw trap (RST) located at
river mile (RM) 1.7. This monitoring project has three primary
objectives: (1) calculate annual juvenile passage indices for
Chinook Salmon Oncorhynchus tshawytscha and Rainbow
Trout/steelhead O. mykiss (we use the term O. mykiss to refer to
both the stream resident (Rainbow Trout) and anadromous
(steelhead) life histories because of the difficulties in
differentiating the anadromous and resident forms in the field)
for inter-year comparisons and analyses of the effectiveness of
stream restoration activities; (2) obtain juvenile salmonid life
history information including size, timing, and potential factors
limiting survival; and (3) collect biological samples from
juvenile salmonids. Chinook Salmon run classifications show that
all Chinook Salmon runs known to the Sacramento River were
captured; however, due to overlapping spawning times of spring-run
and fall-run Chinook Salmon it was problematic to index the
juvenile passage using only the RST at RM 1.7. Since 2003 a
separation weir has been used to isolate adult spring-run Chinook
Salmon from adult fall-run Chinook Salmon; therefore, a second RST
was added above the weir at RM 8.4. Battle Creek The U.S. Fish and Wildlife Service continued its juvenile salmonid
monitoring project in Battle Creek, Shasta and Tehama Counties,
California, that began in December 1998 using a RST located at
river mile (RM) 6.2. The upper Battle Creek RST objectives are to
(1) calculate annual juvenile passage indices for spring-run,
late-fall run, and winter-run Chinook Salmon; Rainbow
Trout/steelhead O. mykiss (we use the term O. mykiss to refer to
both the stream resident (Rainbow Trout) and anadromous
(steelhead) life histories because of the difficulties in
differentiating the anadromous and resident forms in the field);
(2) obtain juvenile salmonid life history information including
size, timing, and potential factors limiting survival; and (3)
collect biological samples from juvenile salmonids. Chinook Salmon
run designations in the Sacramento River watershed were developed
using length-at-date criteria for Sacramento River fall-run
Chinook Salmon. These designations may not be accurate when used
for salmon captured in tributaries of the Sacramento River; these
streams have variable and overlapping run timing of spring-run and
fall-run Chinook Salmon. After 2008 all fall-run designated
Chinook Salmon were reassigned as spring-run in the spring-run
Chinook Salmon passage indices as preventative measures were taken
to reduce the potential for fall-run Chinook Salmon to enter the
upper watershed (above the Coleman National Fish Hatchery barrier
weir). Mark–recapture trials Since the RST only captures fish from a small portion of the creek
cross section, it is necessary to implement a method to project
the RST catch numbers to portions of the creek outside of the RST
capture zone. Mark–recapture trials were attempted, when creek
conditions were conducive for such studies and when fish numbers
allowed, to determine the efficiency of the RSTs to catch juvenile
salmonids moving downstream during a given time period. If one or
no mark–recaptures trials were conducted, then the historic
monthly and global averages were used to calculate that passage
indices. Mark-recapture–trials on Battle Creek are conducted using
hatchery-origin fish (from Coleman National Fish Hatchery), while
on Clear Creek natural-origin fish are used. Fish used for the
trials were either single or dual marked. For the single mark
trials the fish were stained with Bismarck brown-Y. Dual marked
fish clipped with surgical scalpels, removing an area of
approximately 1–2 mm^2 from the tip of either the upper or lower
lobe of the caudal fin and then the fish were stained as above. Note: data within the current year’s monitoring season are
considered provisional. The monitoring season typically concludes
at the end of September.

克利尔溪（Clear Creek）：美国鱼类及野生动物管理局（U.S. Fish and Wildlife Service）持续推进加利福尼亚州沙斯塔县克利尔溪的幼鲑（juvenile salmonid）监测项目，该项目自1998年12月启动，采用设置在河英里（river mile, RM）1.7处的旋转螺旋陷阱（rotary screw trap, RST）开展监测。本监测项目共有三项核心目标：（1）计算奇努克鲑（Chinook Salmon, *Oncorhynchus tshawytscha*）与虹鳟/钢头鳟（Rainbow Trout/steelhead, *O. mykiss*）的年度幼鱼通过指数，用于年际比较及溪流修复活动的效果分析——因野外难以区分洄游型与陆封型个体，本研究采用*O. mykiss*一词同时指代陆封型（虹鳟）与洄游型（钢头鳟）两种生活史类群；（2）获取幼鲑的生活史信息，包括个体体长、出现时序及潜在的生存限制因素；（3）采集幼鲑生物样本。监测结果显示，萨克拉门托河已知的所有奇努克鲑洄游类群均被捕获，但由于春型与秋型奇努克鲑的产卵时间存在重叠，仅依靠RM1.7处的RST估算幼鱼通过指数存在难度。2003年起，项目组使用分隔堰将春季成体奇努克鲑与秋季成体奇努克鲑进行分隔，因此在RM8.4处的堰上方增设了第二台RST。

巴特尔溪（Battle Creek）：美国鱼类及野生动物管理局持续推进加利福尼亚州沙斯塔县与蒂哈马县巴特尔溪的幼鲑监测项目，该项目同样始于1998年12月，初始采用设置在RM6.2处的RST开展监测。巴特尔溪上游RST的监测目标为：（1）计算春型、晚秋季型、冬季型奇努克鲑以及*O. mykiss*的年度幼鱼通过指数；（2）获取幼鲑的生活史信息，包括个体体长、出现时序及潜在的生存限制因素；（3）采集幼鲑生物样本。萨克拉门托河流域的奇努克鲑洄游类群划分采用基于日期的体长标准（针对萨克拉门托河秋型奇努克鲑），但该划分标准用于萨克拉门托河支流捕获的鲑鱼时并不准确，因为这些支流的春型与秋型奇努克鲑洄游时序存在变异且相互重叠。2008年后，为防范秋型奇努克鲑进入科尔曼国家鱼类孵化场（Coleman National Fish Hatchery）拦堰以上的上游流域，所有被划分为秋型的奇努克鲑在春季型幼鱼通过指数中被重新归类为春型。

标记-重捕试验（mark–recapture trials）：由于RST仅能捕获溪流横断面的一小部分个体，因此需要通过外推法将RST的捕获量换算至RST捕获区以外的溪流区域。当溪流条件适宜且鱼类数量允许时，项目组会开展标记-重捕试验，以确定RST在特定时段内捕获下游洄游幼鲑的效率。若当年开展的标记-重捕试验次数少于1次或仅开展1次，则采用历史月度及全局平均数据计算幼鱼通过指数。巴特尔溪的标记-重捕试验使用科尔曼国家鱼类孵化场的孵化场来源鱼类，而克利尔溪则使用野生来源鱼类。试验用鱼分为单标记与双标记两类：单标记组采用俾斯麦棕-Y（Bismarck brown-Y）进行染色标记；双标记组则先用手术手术刀在尾鳍上叶或下叶尖端切除约1–2 mm²的组织，再按照前述方法进行染色标记。

备注：本年度监测季内的数据均为暂定数据，监测季通常于9月底结束。