Counting Adult Steelhead in Favored Pools and Runs at Gualala River Steelhead Studies web site

Counting Adult Steelhead in “Favored”

Pools and Runs

Every die-hard steelhead fisherman worth his salt knows a secret: Adult steelhead migrating up and down small coastal rivers invariably prefer to hold and rest in certain “favored” pools and runs, while many other outwardly similar areas of the stream are rarely, if ever, used. This key principal helps drive the fabled 10 percent of anglers in landing (and hopefully, releasing) 90 percent of the steelhead catch. And it is an important nuance of steelhead behavior which can be exploited for conducting relatively quick and inexpensive population surveys.

Generally, locations of favored pools and runs along any particular reach of stream are learned by anglers through experience (and observation). As the fish move upstream into more remote reaches, or to reaches where angling is not permitted, steelhead investigators must rely on their own surveys to identify the favored resting and holding places.

From my 7 years of surveys along the 18.7-mile Index Reach of the Wheatfield Fork, Gualala River, the favored resting and holding sites are gradually revealing themselves. The best data comes from the 24 surveys (449 miles) conducted between December 23, 2004 and March 7, 2008, in which a total of 2,115 adult steelhead was tallied. Prior to December 2004, adult observations were not consistently recorded down to the site-level, so surveys before this date were not useful in the analysis.

So far, about 16-18 important pools and runs have been identified. However, eight of these sites (see table), including four each on the upper and lower halves of the survey reach, are where most of the fish are consistently counted. The eight most-favored pools and runs (i.e., one every 2.3 miles, on average) cover a broad range of habitat types, from very large, very deep pools to relatively shallow runs. In-water cover and bottom substrate types also vary widely. (Note: The locations [digital maps and GPS coordinates] of these sites are not revealed here, due to possible use by illegal fishers, but are available upon request from qualified resource agency personnel or other similar professionals.)

POOL OR FLATWATER Name and General Description Upper (U) or Lower (L) Survey Reach	Percent All Surveys (Adults Recorded)	Percent Surveys When Total ≥50	Average Count When SH Present	Percent of All SH Counted Here	Max. Single- Survey SH Count
Yellow Rope (L): Long, very deep pool. Sand/bedrock bottom. Low- moderate cover.	49	50	11.1	5.6	30
Bedrock (U): Long, shallow run. Bedrock bottom. Low cover.	43	68	8.5	4.4	23
YMCA (U): Large, circular, deep pool. Sand bottom. Boulders upstr.	40	52	12.5	5.8	25
Lower Cable (L): Long, narrow, deep run. Sand bottom. Abundant woody cover.	21	30	8.6	2.4	17
Concrete Slab (U): Moderate pool. Sand and concrete slab bottom (old road crossing). Low cover.	51	50	12.0	11.8	46
Indian Spearing (U): Large, very deep pool. Sand bottom. Low cover from boulders.	18	25	7.9	1.5	12
Angle-Log (L): Deep, narrow run. Sand bottom. High woody cover.	38	50	18.6	5.8	45
ATV (L): Very large, very deep pool. Sand bottom. Moderate woody and bouldery cover.	22	30	10.7	3.8	40
MEANS AND TOTALS (**)	35	44	11.2	41.1	29.8

Over the past 24 surveys, these eight favored sites have accounted for 41% of the total adult steelhead counted on the Index Reach. On average, adults were recorded at these sites 35% of the time–or 44% if only surveys in which the total count equaled or exceeded 50 fish are considered. The average number per count (when fish were present) for the various sites ranged from 7.9 to 18.6. Highest individual survey counts at the sites ranged from 12 to 46 and averaged 29.8. The top four sites, based on percent of total adults counted there, were the Concrete Slab Pool, YMCA Pool, Angle-Log Pool, and Yellow-Rope Pool. The first two are in the upper survey reach, the second two in the lower. Overall, a combined 29% of all fish counted were recorded in just these four pools.

Thus, the population indexing I have been doing on the river could probably be accomplished just as effectively from surveys (by snorkeling, diving, or boating) of only these four (or all eight) pools and runs. Unfortunately, these sites do not lend themselves well to individual survey, since they are relatively remote and inaccessible, and are best reached by boating down river. However, they could all be surveyed very effectively by helicopter and I am considering doing so in the future.

Identifying these key staging sites could have been done using snorkeling or diving surveys. However, I conducted most surveys by boat, which may be less accurate than snorkeling surveys, but nonetheless less expensive (i.e., requiring less time and manpower).

During my first few seasons on the river, I tested and evaluated several different kinds of survey boats. Kayaks and canoes were both tried and deemed unsuitable, because the observer sits too low for the best (glare-free) view of the stream bottom and adult fish; there are also numerous reaches that are unnavigable using such boats. Medium-and large-size drift-boats were also ineffective, due to their lack of maneuverability on such a relatively small, rocky stream and inability of the observer to see clearly into the water over the (relatively high) sides of the boat.

I eventually selected an 8-ft aluminum mini-drift-boat manufactured by Redwood Welding Service of Crescent City, California (1020 Hwy 101 North; 707-464-6218) for the survey vessel. These boats (two, presently) are highly maneuverable on water and for the past 4 years have been by far the vessel of choice for standard surveys of the Index Reach. They are similar in size and shape to the one-person (inflatable) survey boats that the Oregon Department of Fish and Wildlife has found to be the best choice for standard surveys of steelhead in coastal Oregon streams.

However, achieving the best possible counts of adult steelhead necessitates following some very specific guidance for use of this boat during Index-Reach surveys:

The bottom of the boat is covered (and recovered, as needed, during each season) with “Coat-It,” a two-part epoxy material (Tap Plastics, Inc. and other outlets) containing graphite. This facilitates easy and quietest passage through the shallowest water and while sliding over rocks and boulders at the side of the stream during portages.
Oars are 6.5-ft in length, made of aluminum, with fixed (clamped-on) oarlocks, which are either oiled liberally prior to each survey or appropriately “bushed” to eliminate any rowing noise which might otherwise frighten fish and “push” them ahead of the boat.
A padded seat is added to the boat’s standard aluminum rowing seat, to raise the observer (and reduce low-back strain during the 19-mile float) another 4-6 inches for a better view of the stream bottom.
Surveys are restricted to periods of low turbidity, minimal surface turbulence (which can result from both wind and high flows), and good weather (without rainfall, fog or overcast conditions) to the extent possible. The goal is to always have conditions which allow the entire stream bottom–including the deepest pools–to be seen by the observer.
The observer always wears good-quality polarized sunglasses for seeing into the water and a cap or hat suitable for shading from glare.
The observer always sits facing the wide end of the boat (i.e., the stern) and “pushes” the boat downstream with the oars, maintaining a continuous, downstream view of the bottom (and thus any fish) as he goes. It is important to keep moving slightly faster than the current, so that fish are approached quickly and not “pushed” ahead of the boat, preventing their detection or causing recounts. When shallow or otherwise impassable sections of stream are encountered, the observer exits the boat briefly and drags it around the obstacle(s).
Prior knowledge of traditional fish-holding places along the sample reach is essential. When approaching shallower holding places, the boat is “pushed through” with the oars, while keeping slightly to one side (shallower side) and maintaining speed slightly faster than the current, with the observer remaining seated. When approaching the deepest holding places, the same approach is followed, except the observer remains standing (thus the need for a specific oar length–to allow rowing while standing) for a better view of the bottom (and any fish).
When a group of fish is first detected, a single count is made and recorded on the first “pass” over them. Numerous attempts at repeat passes during dozens of surveys have shown that they invariably (90% of times) result in fewer fish being seen and recorded than on the initial pass.
Survey start times each day are kept within a 90-minute (0830-1000 hrs) window in the morning. This helps ensure that differences in visibility of fish during the day due to the angle of the sun and daily wind patterns (e.g., afternoon upstream breezes) are held roughly constant among seasons. (Parken et al. [2003] and others have reported on the variability that different conditions at different times of the day can add to counts due to sun-angle changes and daily riffling patterns on the stream surface from wind.)
All surveys are conducted by the same experienced observer(s).

For photos of the survey boat (and author), refer to the Photo Gallery.