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Gualala River Steelhead Spawning Run Surges to New High in 2008
News Release: March 10, 2008
The 2008 spawning return of adult steelhead in the Gualala River appears to be on its way to the highest annual total this investigator has recorded since surveys began in 2001
During just four surveys (of the Wheatfield Fork’s “Index Reach”) conducted through early March 2008, a total of 834 adult steelhead (i.e., a population index, not a total count) have already been counted. In contrast, four-to-eight counts in 2003, 2004 and 2006 yielded only 86 to 211 adult fish, while seven-to-nine counts in 2002, 2005, and 2007 produced totals of 377 to 762 fish.
Should the 2008 spawning return remain as strong throughout the remaining weeks of the spawning season (which usually ends about April 30th), the Wheatfield Fork’s total spawning population (to be calculated by mid-2008) estimate for the season is likely to exceed 3,000 fish.
The Wheatfield Fork is the largest (37 percent) of the river’s five primary branches. It probably supports the largest segment of the river’s steelhead spawning run. It is also the only branch currently being systematically surveyed (for spawning), although in the future, surveys from helicopter of other selected river reaches will likely be initiated (Helicopter Surveys page).
Recording such a robust spawning return in 2008 leads to an obvious question: Does it indicate a river ecosystem and steelhead population in good health? The unfortunate answer in both respects is “no.”
The significant upsurge of spawning adults in 2008 is the likely product of recent climatic anomalies which may not recur again for decades. The first anomaly was an usually early start to the 2004-2005 rainy season in mid-October 2004. Heavy rains restored surface flows to main-stem river reaches which had become dewatered over summer. Juvenile steelhead (JSH) thus gained relief from hostile in-stream conditions, including lack of surface flows (and associated connectivity) and massive stranding (and mortality) in drying pools. A large proportion of the surviving JSH population then apparently made a relatively early seaward exodus from the river. With a more normal start to the rainy season in November or early December (i.e., when the first seasonal flow increases normally occur), many more JSH would likely have perished before smolting and migrating to sea.
A second, even more fortuitous climatic anomaly appeared in the spring of 2005. Both March and May had above-average rainfall, with May far above average. Late-season precipitation of such magnitude, even when overall yearly rainfall remains average or below, greatly benefits watershed hydrodynamics. Ground and surface water is replenished just before the onset of summer, thus reducing and delaying inevitable summertime declines of surface stream flow. With higher summertime flows, little or no main-stem dewatering occurs (which was true in 2005) and rearing conditions for JSH (especially with respect to water temperature) are markedly improved. Improved summertime rearing results in both more and healthier JSH ultimately emigrating to sea. A strong case can thus be made that 2008's robust spawning return is largely a product of 2005's unusually wet springtime conditions.
Moreover and despite low odds, the wet-spring anomaly recurred yet again in 2006, when April rainfall far exceeded average. In addition, annual rainfall for 2006 was also far above average. Thus, just as in summertime 2005, flows, temperatures, and JSH rearing conditions were greatly improved in summertime 2006. The resulting improved production of JSH may have played a role in the robust 2008 spawning run, but is more likely to be expressed as increased spawners in 2009.
Nevertheless, short-term benefits to steelhead of rare back-to-back wet springtime seasons cannot negate serious and extensive habitat problems facing the river and its salmonids (i.e., also including coho salmon–which appear to have been extirpated from the river). Excessive sediment, extensive summertime dewatering (including large, main-stem reaches), and water temperatures elevated to lethal levels for JSH, not only persist in most years, but appear to be incrementally worsening.
A return of extensive summertime dewatering and hostile (to JSH) water temperatures is inevitable with recurrence of average-to-below annual rainfall–or seasons with low springtime rainfall. Just as inevitably, fewer JSH will then be produced, with fewer adult spawners returning 1-3 years later.
Nevertheless, there is reason for optimism. Mother Nature, via high springtime rainfall in 2005-2006 has sent us a message: The robust spawning return for 2008 shows that the steelhead population is still quite resilient and capable of marked positive response, when favorable habitat conditions driven by climatic anomalies improve JSH rearing and production. And the jump in adult numbers lends credence to the thesis that man-made habitat improvements may benefit steelhead equally as well (as natural acts).
The “window of opportunity” is clearly limited, however. Effective solutions to the river’s habitat problems must show marked progress soon or population viability will certainly become compromised at some future point. And at that time, steelhead will surely start down the same path as the river’s coho salmon.
December 31, 2008 Update:
The final results for the 2008 spawning season were indeed historic. During just six surveys of the Index Reach of the Wheatfield Fork, an amazing 1,402 adult steelhead were counted. Therefore, the overall Wheatfield Fork spawning population for 2008, based on the methodology described in detail in my 2007 Annual Report, was 5,843 fish. Allowing for various potential errors that may have occurred in the calculation methodology, the real number of adult fish may have only been about 4,000 to 4,300. Nevertheless, a spawning return on the order of 4,000-5,800 adult fish, for just one of the river’s five main branches, is indeed important and exciting news. There is no question that this was the largest spawning return in my 8 years of working on the river–-and quite possibly the largest return in decades!
(Note: Several issues addressed here are more fully discussed and explained in the 2001-2007 Annual Reports and other pages of this web site. The reader may wish to review these for more insight.)
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