PREPARED FOR:
Nestucca / Neskowin Watershed Council

PREPARED BY:
Steve Trask
Bio-Surveys,LLC.
Po Box 65
Alsea, Or.
97324

FUNDED BY:
Oregon Watershed Enhancement Board

USDA – Forest Service WY020 and WY2-005

RAPID BIO-ASSESSMENT 2004

INTRODUCTION

             A Rapid Bio-Assessment inventory was conducted for the Nestucca / Neskowin Watershed Council (NNWC) during the summer of 2004. This inventory included the Nestucca, Neskowin and Sand Lake basins and marked the final year of a three year project. The intent of the project was to gather information on the status of juvenile salmonid summer distributions and summer rearing densities. The inventory consists of extensive snorkel surveys in each basin that begin at the head of tidal influence and continue to the end of juvenile Coho distribution in each stream and its tributaries (the mainstem Nestucca began at the confluence of Beaver Cr. during 2002 and 2003 and at the confluence of Boulder Cr. during 2004).  These surveys were conducted using funds granted to the NNWC by OWEB.  The intent of these surveys is to develop base line data for each of three successive cohorts and to eventually identify long term trends in the distribution and abundance of juvenile Coho, Steelhead, Cutthroat and Chinook at the 6^th field level in response to restoration and watershed management issues.

            The escapement of adult Coho in all of the surveyed basins during the 2001, 2002, and 2003 brood years has remained insufficient to adequately seed the summer habitat currently available on a watershed scale throughout the four 5^th fields in the NNWC management area. For many of the basins and subbasins, adult escapement is the primary limiting factor for production. The trend in the adult escapement of Oregon Coast Natural (OCN) Coho since 1990 has been positive for all of the NNWC basins with the highest recorded escapement in the last 13 years occurring in 2002.     The agreement in trends between the ODFW adult SRS data and the RBA juvenile estimates for the Nestucca basin mutually support the ability of each method to assess inter annual trends. This agreement in methodology is largely a function of appropriate sampling effort for the size of the target basin. Conversely there was a radical divergence in trends within the Sand Lake / Neskowin complex when comparing these two methods. There is a weakness in the SRS sampling effort within small basins that can lead to conclusions in adult abundance and trend analysis that do not appear to be supported by the abundance of summer rearing juveniles (see table 1). This effect is discussed in more detail in the Neskowin Basin introduction.

            The 2001-2003 adult Coho estimates exhibit dramatic increases in abundance and are indicators of recent improvements in ocean conditions. ODFW’s long term SRS monitoring of adult Coho escapement suggests that the 14 year trend for the North Coast monitoring area is one of only two statistically significant trends observed in the five coastal monitoring areas. This statistically significant trend was also detected in the more intensive monitoring associated with the Oregon Plan conducted between 1997 and 2001 (E-Map). Both methods suggest that the trend is driven primarily by abundance in the Nehalem River but that a significant positive trend is also quantifiable in the Nestucca.

It is important to recognize the significant role that changes in adult escapement can have on the observed distributions and densities of juvenile salmonids.  The resultant distribution data from 2004 still does not describe all of the accessible and suitable spawning and rearing habitats for salmonids because of continued under-escapement.

 (Table 1) Adult escapement and normalized summer parr estimates for Coho

Survey                   Nestucca Basin                                    Neskowin / Sand Lake

Year        Adult escapement    Summer Parr          Adult escapement     Summer Parr

2002               3,940 (01)           189,865                          71 (01)                10,745  

2003             13,003 (02)           353,045                          16 (02)                12,700

2004               8,929 (03)           295,320                            0 (03)                12,375

             The juvenile survey method was designed to look at a sub-sample (20%) of rearing habitats using a Rapid Assay technique that could cover large distances and succeed in describing the current distribution of Coho and quantify the rearing densities of Coho and the relative abundance of Cutthroat, Steelhead, and Chinook in all of the surveyed streams and their tributaries.

            The 2004 database contains the results of 187.6 stream miles that were surveyed. This includes the full extent of Coho distribution in Sand Lake (7.1 miles), Neskowin (12.4 miles) and Nestucca basins (161.5miles), except for the segment of the mainstem Nestucca between the head of tidal influence and the bridge just below Boulder Cr., as well as the majority of West Beaver (inadequate visibility). The start point for the mainstem Nestucca survey was moved upstream 5.4 miles from Beaver Cr. in 2004 due to a funding shortfall and the observed low Coho production in this reach during 2002 and 2003. 2.8 miles of the upper Nestucca mainstem, between the Cedar Cr. bridge and the Walker Cr. confluence, were surveyed for the first time in 2004 to assess the effects on adult passage from the channel alterations which took place in the gorge just above Cedar Creek. Walker Cr. was also surveyed. If a stream is not included in the database it was not surveyed. This will occur only in situations where a mapped tributary was dry or where there was a lack of suitable visibility for the survey methodology.

METHODS

             The basins and sub-basins surveyed were selected and prioritized by ODFW, BLM, USFS and NNWC technical advisors.  Survey crews were concentrated within a basin to complete the sampling activity within a concise window of time.  This approach led to transportation efficiency and eliminated any possibility of population shifts in response to changes in flow or temperature. This strategy was altered for the mainstem Nestucca where local knowledge from the technical advisory panel of the NNWC indicated that visibility in the lower mainstem could degrade during the summer months because of temperature driven algal blooms. This resulted in a hiatus of 24 days between surveys on the mainstem Nestucca between the first 10.7 miles surveyed in June above the confluence of Beaver Cr. and the remaining 22.2 miles surveyed in July and August to the end of Coho distribution.

            Land owner contacts were made for all of the private, industrial and public ownerships that existed on both sides of every stream reach surveyed.  Developing these contacts involved extensive research in the county tax assessor’s office and then a personal contact to describe the survey and request permission for access. The land owner information was recorded (name, contact #, tax lot # and location) and will be available in subsequent years as a byproduct of this contract.

            Most surveys were initiated by randomly selecting any one of the first five pools encountered.  The protocol however was altered for small tributaries (2^nd order) where Coho presence or absence was undetermined, in these tributaries, the first pool above the confluence was selected as unit number one. This alteration in protocol was adopted to identify minor upstream temperature dependant migrations that may not have extended more than a few hundred feet. The identification of this type of migratory pattern in juvenile salmonids is critical for understanding potential limiting factors within the basin (temperature, passage, etc.). Some surveys were initiated at a point above brackish water influence or above agricultural influence where visibility conditions shifted from poor to good. In these surveys the start point of the survey will be indicated separately on the USGS quads available through the NNWC.                                                                                                                                                 

            The survey continued sampling at a 20% frequency (every fifth pool) until at least two units without Coho were observed.  In addition, pools that were perceived by the surveyor as having good rearing potential (beaver ponds, complex pools, tributary junctions) were selected as supplemental sample units to insure that the best habitat was not excluded with the random 20 percent sample. This method suggests that the data existing in the database could tend to overestimate average rearing density if these non-random units were not removed prior to a data query (the selected units are flagged as non-random in the database).

In subbasins with low rearing densities, there were situations where Coho were not detected for more than two sampled units.  These situations were left to the surveyor’s discretion, whether to continue or terminate the survey. There is a possibility that very minor, isolated populations of juvenile Coho could be overlooked in head water reaches of small 2^nd order tributaries. This tributary would have to include a strong beaver population that would impound emergent fry and truncate their normal downstream fry distribution patterns.

            Pools had to meet minimum criteria of being at least as long as the average stream width. They also had to exhibit a scour element (this factor eliminates most glide habitats) and a hydraulic control at the downstream end. There were no minimum criteria established for depth.  Only main channel pools were sampled.  Side channel pools, back waters and alcoves were not incorporated into the surveyed pool habitats. The primary reasons for not including these secondary and off channel pools is that they are typically not highly productive summer rearing locations and they compromise the consistency of measuring, summarizing and reporting lineal stream distances.

            The lineal distances represented in the database were estimated by pacing from the beginning of one sampled unit to the beginning of the next sampled unit.  The length of the sampled pool is an independent quantity, which was always measured and not estimated.  A minimum of three lineal estimates were also measured with a hip chain for each surveyed stream to develop a calibration factor for each surveyors estimate of distance.  Total distances represented in the database are consistently greater than map wheeled distances using USGS 1:24,000 series maps. This is related to the level of sinuosity within the floodplain that is not incorporated in mapping. If you are attempting to overlay this database on existing stream layer information there would be a need to justify lineal distances with known tributary junctions (these can be found in the comments column). In addition, the USFS under contract to the NNWC will be producing a digitized stream layer of Coho distribution for incorporation into the current GIS database.

Pool widths were generally estimated.  Because pool widths vary significantly within a single unit, a visual estimate of the average width was considered adequate.  Pool widths were typically measured at intervals throughout the survey to calibrate the surveyor’s ability to judge distance.

            The snorkeler entered the pool from the downstream end and proceeded to the transition from pool to riffle at the head of the pool.  In pools with large numbers of juveniles of different species, multiple passes were completed to enumerate by species. (Coho first pass, 0+ trout second pass, etc. ). This allowed the surveyor to concentrate on a single species and is important to the collection of an accurate value. In addition, older age class Steelhead and Cutthroat were often easier to enumerate on the second pass because they were concentrating on locating food items stirred up during the surveyors first pass and appeared to have less of their initial avoidance behavior.

            In large order stream corridors (mainstem Nestucca), two snorkelers surveyed parallel to each other, splitting the difference to the center from each bank.

            A cover/complexity rating was attributed to each pool sampled. This rating was an attempt to qualify the habitat sampled within the reach. The 1 - 5 rating is based on the abundance of multiple cover components within a sampled unit (wood, large substrate, undercut bank, overhanging vegetation). Excessive depth (>3 ft) was not considered a significant cover component. The following criteria were utilized:

1          0 cover present

2          1-25   %   of the pool surface area is associated with cover

3          26-50 %   of the pool surface area is associated with cover

4          51-75 %   of the pool surface area is associated with cover

5          > 75   %   of the pool surface area is associated with cover

            A point to consider here is that the frequency of higher complexity pools increases with a decrease in stream order. This inverse relationship is primarily a function of average channel width and the resultant ability of narrow channels to retain higher densities of migratory wood. Channel morphology begins to play a much more significant role in this relationship during winter flow regimes where increases in floodplain interaction and the abundance of low velocity habitat may become as significant as wood complexity.

 A numerical rating was given to each sampled unit for the surveyor’s estimate of visibility. The following criteria were utilized:

Visibility                                                                

1          excellent                                                    

2          moderate                                                   

3          poor                                                           

             This variable delivers a measure of confidence to the collected data. Survey segments with a measure of 1 can assume normal probabilities of detection (the observed is within 20 percent of the actual for Coho). Segments with a measure of 2 suggest that less confidence can be applied to the observed number (uncalibrated) and segments with a visibility rating of 3 suggest that the observation can probably be used for only an assessment of presence or absence.

            There was also commentary recorded within each of the surveyed reaches that included information on temperature, tributary junctions, culvert function, the abundance of other species and adjacent land use. This commentary is included in only the raw Access database under the “comments” field and not in the Excel cd.

            The database contains fields designed to facilitate the development of a GIS data layer. These are LLID location numbers that are unique for each stream segment and latitude and longitude coordinates collected for unique features. Lat / Long coordinates are reported in degrees, minutes and seconds. Latitude and longitude values were not collected for start points because these values already exist in the actual LLID number used to initiate a surveyed reach.

GENERAL OBSERVATIONS

  The distribution and abundance of Coho juveniles observed during the 2004 summer field season in the Nestucca and Neskowin basins was the result of a wide spread decrease in adult escapement during the 2003 brood year. This resulted in general reductions in juvenile abundance when compared to the strong response observed the previous year from the 2002 Coho cohort.

The summation of data from three years of inventory in these watersheds illustrates the relative production significance and spawning location preferences between each of three separate cohorts, or generations, of Coho returning to each basin. The pattern that emerges for the Nestucca clearly shows the 2001 adult brood as the smallest, the 2002 adult brood as nearly twice as large, and the 2003 adult brood in the middle nearer to the size of the larger (table 1). The changes in adult estimates for these years in the Nestucca basin appear to closely match the changes in summer rearing estimates which lends validity to this comparison.

The pattern observed for Coho in the Neskowin / Sand Lake complex is not as clear. The trends observed in adult estimates disagree with the trends observed in juvenile estimates. Adult estimates have been steadily decreasing for these two basins while combined summer parr abundance over three years has increased by 15%. Juvenile abundance patterns in the Neskowin basin appear to follow those from the Nestucca more closely than those from Sand Lake.

Juvenile abundance estimates from Sand Lake appear to stand alone, exhibiting a trend in abundance unique from either the Nestucca or Neskowin basins. The 2002 adult brood appeared to represent the smallest cohort in Sand Lake, based on 2003 summer parr estimates. The 2001 adult brood was approximately 41% larger, and the 2003 adult brood was the largest of the three cohorts, about 72% larger than the 2001 brood. The unique patterns encountered in the Sand Lake basin are in part a function of their depressed and erratic states of production but also may be a function of the specialized adaptations for survival and rearing that the specific Sand Lake habitats dictate through natural selection. More discussion of these factors is included in each basin’s respective introduction.    

The above patterns only compare differences (strengths and weaknesses) between the three separate Coho cohorts. In order to follow how each cohort fairs individually at over winter survival, ocean survival, and spawning success another three consecutive years of monitoring would be necessary (i.e. the fourth year of data would reflect the life cycle success of the first year, its “cohort”). A weak or strong cohort may be uniquely affected by a number of factors including yearly differences in ocean conditions, stream flow patterns, catch limits, and hatchery straying.

Most habitats are still not seeded to capacity in the inventoried systems and there remains extensive summer habitat available to salmonids that is currently under-utilized. There were some exceptions - Baxter, Bear, East Beaver, Elk, Louie, Sourgrass, and Trib F / Nestucca (2004) exhibited a fully seeded condition for Coho during both the 2002 and 2003 inventories (Trib F for 2004 also). These tributaries represent important anchor habitats for OCN Coho. For the following review, we are considering 1.5 fish / sq.meter a fully seeded density for Coho. There are concerns from many biologists that this estimate of fully seeded does not represent the production potential that exists in completely functional Coho habitat that is benefiting from the nutrient loading of adult spawning salmonids (eggs, carcasses). There are excellent examples from 2003 in Elk Cr., Baxter Cr., and East Beaver Cr. of stream reaches that far exceeded the level of 1.5 fish/sq.m. of pool surface area (up to 3.0 fish/sq.m. in Baxter and Elk). The intent of establishing this target of full seeding is to provide a platform for comparing stream reaches to each other and to themselves over time. The graphics available in the Nestucca / Neskowin cd utilize this value to normalize scaling.

            The average density for a surveyed reach is an excellent measure of trend that can be monitored from year to year. However, it tends to portray only a general description of the current status within a reach. Understanding how each reach is functioning is more accurately interpreted in a review of how the rearing density changes within the reach. The graphics provided in electronic format with this summary are essential for the proper interpretation of this review (refer to 2004 Nestucca / Neskowin cd, NNWC).

 Distribution profiles 

            The distribution of juveniles and their observed rearing densities for each surveyed reach provide a basis for understanding how each reach is functioning in relation to the remainder of the basin or subbasin. These profiles can help identify spawning locations, identify potential barriers to upstream adult and juvenile migration, identify the end point of Coho distribution and they may also indicate how juvenile salmonid populations are responding to environmental variables such as increased temperature. You will find a review of these distribution profiles within this document for each of the major basins and subbasins surveyed during the 2004 field season.

Location of spawning destinations

 The approximate locations of spawning pairs was observable in many of the sampled sub basins by the presence of a distinct spike in rearing density that trailed off rapidly just upstream. The physical location of a spawning destination has a range of variance plus or minus 4 pools due to the 20 percent sample methodology.  Depending on the average distance between pools, this typically describes a maximum lineal distance that varies between 150 ft. in a small 2nd order tributary to 800 ft. in a fourth order tributary. To utilize the database to identify spawning destinations, an additional precaution is necessary. Surveyed lineal distances are typically longer than calculated distances (map wheel, GIS, etc.) due to the sinuosity of the active channel that is not displayed in the 1:24,000 series USGS maps. To accurately evaluate site specific locations it is important to utilize the digitized map layer that has been justified to known end points and tributary junctions. This layer was developed by the USFS in 2002 and 2003 and is available from the Nestucca / Neskowin Watersheds Council.

            The average densities generated represent a snapshot in time of the current condition that can be compared to known levels of abundance that exist in fully seeded and fully functional Coho habitats. These densities also provide a method for quantifying changes in rearing densities by reach or subbasin over time. Average densities utilized as a metric in this analysis are calculated for pool surface areas only. Lower levels of Coho abundance exist in fast water (riffle/rapid) and glide habitats. Replicate surveys conducted in these same reaches in subsequent years will function as an indicator of response to future restoration and enhancement strategies and potential changes in land use. It does not however, provide any indication of actual smolt production because of the distinct relationship between juvenile Coho survival and the abundance of high quality winter habitat.

Adult and Juvenile Barriers

                Adult migration barriers are verified by determining that no juvenile production is occurring above a given obstruction (culvert, falls, debris jam, beaver dam, etc.). There are many barriers, both natural and manmade that impact the migration of salmonids in coastal basins. Some are definitive barriers that are obvious obstructions (such as the bedrock falls on the Little Nestucca below the confluence of Fall Cr., which is a migration barrier to juveniles?) Many barriers however, only impede adult salmonid migrations during low flow regimes. Summer juvenile inventories allow us to definitively quantify whether passage was obtained at any point during the season of adult migration.

            Juvenile salmonids typically migrate upstream for a variety of reasons (temperature, winter hydraulic refuge, food resources). Hydraulic refuge and food resources are typically fall, winter and spring migrations that would not be detectable during summer population inventories. Temperature however, is probably the most significant driver of upstream juvenile salmonid migrations during summer flow regimes. Juvenile barriers are subjective to the eye of the observer. The trend in juvenile density can be a method of detecting either partial or full barriers to upstream migration. Each of the surveyed reaches contains a comments section in the Access database to note the presence of culverts, jams and other physical factors that may influence the ability of salmonid populations to make full use of aquatic corridors.  

Temperature Dependant Migrations

Potential temperature dependant migrations can be observed in the database by looking for densities that decrease significantly as the lineal distance increases from the mouth of the stream or tributary. This is more likely to be observed in the case of low abundance years where tributary habitats that are seeded to capacity are the exception. During years of high abundance there is a more significant potential for density dependant upstream migrations that would be indistinguishable from the distribution pattern mentioned above. The recognition of this migration pattern allows us, during years of low escapement, to identify important sources of high water quality within the basin that may be traditionally overlooked because of some other morphological condition that suggests to us that there is no significant potential for rearing salmonids (i.e. lack of spawning gravel). These stream reaches typically exhibit declining densities with increased distance from the mouth and no indication of a spawning peak (a point near the upper distribution of the population with significantly higher rearing densities). These tributaries may be functioning as important summer refugia for salmonid juveniles threatened by increasing temperatures in the mainstems.

 Precautions

             The specific location of spawning sites does not infer that the highest quality spawning gravels were targeted by adult salmonids or that there is any relationship between the location of a redd and the quality of the rearing habitat that exists adjacent to these locations.

            The location and distribution of juvenile Coho represented in the database is not related to the quality of the rearing habitat that exists in the aquatic corridor adjacent to these sites.

            The average densities that can be generated as an end product for each stream reach are the result of a 20 percent sample. Consequently, they probably vary significantly around the true average density. There are many sources of potential variation, start point, number of units sampled within the reach, surveyor variability, etc. The range of variability for at least one of these variables (start point), was documented in the final review of the 1998 Rapid Bio-Assessment conducted by Bio-Surveys for the Midcoast Watershed Council. To facilitate the proper utilization of the data included in this inventory, the 1998 results are included in Table 2. The true average density of a stream reach was retrieved by querying the database from an ODFW survey on East Fk. Lobster where every pool was sampled. Comparisons could then be made between the true average density and a randomly selected 20 percent sub sample (every 5th pool). Only mainstem pools were utilized within the range of Coho distribution to match the protocol for the Rapid Bio-Assessment. Table 2 contains this comparison, exhibiting the variation in average density based on the selection of different starting points.

(Table 2)

SAMPLE FREQUENCY     AVG. COHO DENSITY               AVG. SH DENSITY    AVG. CUT DENSITY    AVG. 0+ DENSITY

100 %                               1.07                                .03                                  .04                    .13                   50  %                               1.10                                .04                                  .03                     .14

20 % Start Pool 1               0.87                               .04                                  .03                     .13

20 % Start Pool 3              1.01                                .03                                  .03                     .13

20 % Start Pool 5              1.13                                .05                                  .04                     .12

                When calculating the average density of juvenile Coho in a particular stream reach, it is important that only the data be utilized that falls within the distribution of Coho. Many stream reaches contain sample sites that extend well above the actual distribution of juvenile Coho. Including these data points significantly underestimates the average rearing density and provides a poor foundation for monitoring trends in subsequent years. There are also many streams surveyed that have a downstream point of Coho distribution that is well above the start of the survey reach. Two factors for each stream reach surveyed are key elements for trend analysis, the extent of the distribution and the average density within that distribution.

SITE SPECIFIC OBSERVATIONS

 Site specific observations within this document have been organized in a format that utilizes GIS definitions to describe basins and subbasins. The area within the NNWC management zone includes four 5^th fields. Each of these 5^th fields has been summarized separately. The expanded juvenile salmonid estimates are also broken down into 5^th field estimates (i.e., the mainstem Nestucca does not include the production from the Little Nestucca).

Nestucca

The Nestucca mainstem survey began at the confluence of Beaver Cr. in 2002 and 2003. Habitat downstream of this point exhibited poor visibility resulting from suspended solids and algae. This mainstem start point was moved upstream 5.4 miles to Boulder Cr. in 2004 due to reduced funding and previous observations of low mainstem Coho production between these two tributaries. There is significant juvenile salmonid rearing that occurs in the 14.5 river miles between Pacific City and the confluence of Beaver Cr. (6.6 of these river miles are classified as intertidal, from the boat ramp in Pacific City to the head of tide at the Cloverdale bridge). This potential production has not been accounted for in the 4^th or 5^th field production estimates below.

The following tables represent the contribution in salmonid production (by species) from each tributary to the Nestucca 4^th field Watershed.  Table 4 represents total results from 2004 inventories and Table 3 represents production within just the Main Nestucca 5^th field (minus the Little Nestucca subbasin). These production estimates are based on an expansion of the 20% snorkel sample in pools only and therefore do not constitute an entire production estimate for the basin. In addition, production from several streams that were not surveyed during all three years has been omitted from the tables in an effort to normalize the comparisons. These estimates greatly under estimate the standing crop of 0+, Steelhead and Cutthroat because a large component of the basin’s standing crop is summer rearing in riffle / rapid and glide habitats that were not inventoried. In addition, there is also production for these three groups that extends upstream beyond the end point of Coho distribution where the surveys were terminated. This table however, can be utilized to establish a baseline for trend monitoring for subsequent survey years on the basin wide scale and by tributary. The table functions well to establish relative production potentials that can be utilized as a foundation for prioritizing restoration opportunities.

Basin wide Coho production rose 92% in 2003 in response to a surge in adult escapement. That year stands as the largest summer rearing population within our three year inventory, nearly twice as large as the 2002 population and 20% larger than the 2004 population. Highest rearing increases in 2003 were found in Powder Cr. (798%), Moon Cr. (533%), Little Nestucca Mainstem (327%), Niagara Cr. (265%), Mainstem Nestucca (91%), Three Rivers (70%), Elk Cr. (58%), and Bear Cr./Nestucca (40%). Habitat reaches seeded to capacity that year were found in Elk Cr., Bear Cr./Nestucca, and East Beaver Cr.

In response to a 31% drop in adult escapement estimates 2004 summer rearing estimates fell 16.4%. The top five subbasins have changed little from year to year except for the continuous rise of Niagara Cr. to the #1 producing tributary. The Nestucca mainstem has remained the largest component of basin wide Coho production during all years. Moon Cr. rose to the second largest tributary producer in 2004 leaving Beaver Cr. in third, Bear Cr. in fourth, and Elk Cr. in fifth. Highest average rearing densities for Coho were observed again in Trib F/Nestucca/2004 (1.5fish/sq.m.), Niagara (1.1 fish/sq.m.), Elk (1.0 fish/sq.m.), and Bear/Nestucca (0.94 fish/sq.m.). These density levels all display decreases from 2003 figures. Trib F of the Nestucca appeared to represent the only habitat within the basin that was seeded to capacity in 2004. Table 3 clearly illustrates the changes in abundance between these subbasins from year to year.

(Table 3) Coho production trends in the Nestucca 5^th field.

-Mainstem figures and % totals in Table 3 above have been normalized to include identical habitats

 Decreases in Coho production were noted throughout most reaches in 2004 with most notable losses recorded in the Nestucca mainstem (down 11.5%), the Little Nestucca mainstem (down 54%), Beaver (down 49%), Elk (down 51.4%), and Wolfe (down 61%). Exceptions to this trend included Bear Cr. of the Nestucca (up 14%), Niagara (up 16.4%), and Powder (up 42%). These three streams alone displayed continued production growth for two consecutive years. Notably, almost every tributary to the Little Nestucca showed an increase in 2004 despite basin wide reductions led by a dramatic reduction in mainstem rearing. Also worth noting were the greatly depressed populations seen this year in Elk Cr. and Beaver Cr., two primary producers of Coho and the only two subbasins to display a smaller summer rearing population in 2004 than in 2002 (the lowest year of the three year inventory for Coho abundance). These comparisons are drawn from a total of 161.5 miles of Coho distribution within the Nestucca basin.          

These shifts in populations may be influenced by a number of factors ranging from differences in habitat accessibility based on winter stream flow regimes, to behavioral mechanisms that dictate which tributary will receive the bulk of the adult escapement. For example, 2004 summer rearing patterns (a year of moderate abundance compared to 2003) appeared to reflect more spawning focus in tributary reaches as compared to 2003’s higher mainstem Nestucca, Little Nestucca, and Beaver Cr. focus. Tributary distributions in general were also greater for most reaches in 2004 while rearing densities decreased. The most important trend to emerge for Coho out of all three years is the continued spawning focus on the upper basin tributaries, including Elk Cr., Bear Cr., Niagara Cr., Moon Cr., East Beaver Cr., Louie Cr., Sourgrass Cr., and the South Fork Little Nestucca, in addition to the extremely high rearing densities observed in the upper reaches of the Nestucca mainstem.  

Overall 1+Steelhead rearing within surveyed reaches has dropped two years in a row by 11%. This emerges as a conspicuous negative trend that may reflect something as serious as a substantial loss of wild smolt production. 0+trout abundance displayed a 44% decline basin wide in 2003 then rose by 37% in 2004. The final basin-wide population size of 95,955 (normalized) in 2004 remained substantially lower than the 2002 population of 130,405 (normalized). This trend supports the observation that a decrease in production is occurring.

Increases in 1+Steelhead rearing were observed in Bear Cr./Nestucca (53%) and the Little Nestucca subbasin (26%) in 2003, while the largest reductions in abundance were recorded in Moon Cr. (-44%), Mainstem Nestucca (-26%), and East Beaver Cr. (-18%). 2004 surveys observed more widespread losses to this population in the Mainstem Nestucca (-27%), the Little Nestucca subbasin (-42%), Three Rivers (-42%), Beaver Cr. (-13%), and Bear Cr./Nestucca (-21%). Notable increases were observed this year in Bays Cr. (+235%, artificially supported by a large release of hatchery smolts within the tributary), Moon Cr. (+42%), Horn Cr. (+63%), and Bear Cr./Little Nestucca (+185%). The top five Steelhead producers remained similar during all three inventoried years – the Nestucca mainstem, Beaver Cr., Three Rivers, Moon Cr., and the Little Nestucca mainstem. A large 62% reduction in 1+Steelhead abundance in the Little Nestucca mainstem in 2004 coupled with the artificial surge in the Bays Cr. population from hatchery releases has switched the 5^th place ranking between these two reaches

(Table 4) 2004 Basin Wide Inventory (Includes Nestucca, Little Nestucca and Nestucca Bay 5^th fields)