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Response to Double-crested Cormorant Management Plan

August 15, 2014
by Barry K. MacKay

Sondra Ruckwardt
U.S. Army Corps of Engineer, District, Portland
Attn: CENWP-PM-E/Double-crested Cormorant draft EIS
P.O. Box 2946
Portland, Oregon 97208-2946

Response to Double-crested Cormorant Management Plan to
Reduce Predation of Juvenile Salmonids in the Columbia River Estuary

I am writing on behalf of Born Free USA in response to the "Double-crested Cormorant Management Plan to Reduce Predation of Juvenile Salmonids in the Columbia River Estuary", hereafter referred to as "the Plan". We oppose the "Preferred Alternative".

As the title suggests, the Plan is designed to enhance smolt survival by killing a large number of cormorants. The Plan discusses a multiplicity of anthropogenic factors influencing smolt survival, but then has simply scapegoated cormorants -- one species in a complex ecosystem. The Plan assumes that if more smolt leave the Estuary, more adults will return to spawn thereby enhancing the salmon populations. Our position is that this approach -- based on the assumption that each predator removed results in an increase in the species equal to the number of individuals not consumed -- reflects a long outdated approach to ecology and wildlife management in which no positive role is assigned to the predator. But in fact, in a naturally-evolved predator-prey relationship, it is the number of prey that determine the number of predators.

Recent media coverage, reporting on the current presence of cormorants and other predators, suggests that the numbers of Sockeye and Chinook Salmon taken in 2013 broke all previous records. Yet, there appears to be no empirical evidence provided in the plan that demonstrates having the largest take of two Salmonid species is related to having a large cormorant population which the Plan alleges is having a deleterious effect?

While the Plan examines the various Salmonid populations in the Columbia River, showing some populations increasing and some in decline, it fails to identify what Salmonid populations cormorants feed on and whether the consumption enhances, reduces or has no significant effect on the overall carrying capacity of the River for the different Salmonid populations.

I argue that such a simplistic approach to a complex system will have ecological consequences not considered in the Plan and with no guarantee that the Plan's assumed outcome will indeed become a reality.

There are multiple human activities that affect Salmon, including fish farming, an increase in numbers of sea lice within the oceanic environment, acidification, dams and the results of various forms of land use. The singular and accumulative effects of these impacts are not well understood. Nor is there any real consideration of the need to modify such activities to mitigate negative impacts on Salmonids and other species. Instead, simplistically, blame is attributed to the cormorants. Given the enormity of the anthropogenic changes to the river ecosystem, the simplistic notion that more salmon leaving the estuary means more salmon returning and the singular blame of one (or a few) predatory species reduces the credibility of the Plan and calls into question the management approach.

Wildlife managers tend, too often, to operate under the inherent assumption that when apex predators are reduced or removed from a region, prey species of concern will not be consumed and will survive and be part of and contribute to their respective populations. This assumption is not based on empirical evidence or peer reviewed science but is presented as a "logical assumption".

Dating back over a century, study after study has demonstrated that Double-crested Cormorants are rarely responsible for declines in fish species, exclusive of highly contrived situations, such as a diurnal hatchery release, or when the fish are confined by some construction. In most cases the species of fish that are of concern typically are "game" or "commercial" species, or "forage" fish they consume (see, for example: since they are of the greatest interest to commercial fishers and anglers. Indeed, the Columbia River Estuary appears to be an example of an ecosystem that sustains a large cormorant population where at least two Salmonid species, the Sockeye and Chinook Salmon populations are currently on the increase.

Yet cormorants are, for a variety of reasons, irresistibly attractive as scapegoats, and "traditional" reasons for blaming them are often complex, as discussed by Linda Wires in her book, The Double-crested Cormorant: Plight of a Feathered Pariah (Yale University Press, 2014) and by Richard King, in his book, The Devil's Cormorant A Natural History (University of New Hampshire Press, 2013).

Wildlife managers single out the Double-crested Cormorant as the "villain" with no consideration of its role as an apex predator. No weight is given to the possibility that Cormorants can enhance or maintain fish species by removing ill or genetically compromised fish, predators and competitors, or even contribute to ecological health by transferring nutriment from aquatic to terrestrial environments as is true of "sea" birds generally. It seems likely that the species has had a role in making newly emerged islands more fertile, thus enhancing biodiversity.

The nineteenth century lethal approach to wildlife management, however politically expedient, did not then and does not now effectively resolve the concern for the decline in some species, in this case a decline in specific Salmonid at the smolt stage. Such management approaches divert resources from efforts which, while perhaps more complex to explain, are more likely to actually work.

The decline in some Columbia River Salmonids has coincided with the decline in a variety of fish and other species of wildlife native to the region, including a variety of other seabird species. The species involved are diverse. But they do share a common food source, the herring (Clupea) and other small oceanic fish species such as Sand Lances (Ammodytes).

According to Iain McKechnie, a coastal archaeologist with the University of British Columbia, the archaeological record indicates that for the past 7,000 years herring population levels have been robust and steady, but now are in decline. Herring are consumed by seabird populations including wintering loons, Western Grebes and other species that may nest in salt or fresh water, leading to the theory that, depending on the species, their decline is at least to a variable degree the result of documented and unprecedented declines in herring populations, and those of other small fish species that occurred in the region in much greater numbers than now

But the system is far more complicated than that. For example, one of the Alcids that is increasingly rare, the Marbled Murrelet, is famous for being Old Growth forest dependent. Thus a decline in Old Growth forests is generally cited as a causative factor in the decline in Marbled Murrelet. This is not to suggest that the decline in Old Growth forest habitat is the only factor contributing to the decline in murrrelets, since it also apparently has a high dependence on viable herring stocks.

What is overlooked, I fear, is the effect not only of the loss of Old Growth forest on Salmonids but also the loss of all forests in the vast, Columbia River drainage, including the Snake River. This river is 1,240 in lenth, fed by networks of other lakes, ponds, artesian wells, rivers and streams, which in turn are fed by variable amounts of precipitation and snow and glacial melt, themselves influenced by suites of other factors ranging from local to global in scope.

I mention these variables to emphasize the changing and dynamic nature of the environment and to demonstrate that no single factor can be attributed to the decline in Salmonids but that it involves s suite of interacting factors.

For example, when I visited the upper reaches of the Columbia River basin last year, I noted that the trees in the region have been influenced by heavy infestations of Mountain Pine Beetle which are considered "natural processes". Parks Canada writes, "Mountain pine beetle (Dendroctonus ponderosae Hopk., hereafter referred to as MPB) and fire are major natural disturbance agents for lodgepole pine ecosystems in western North America". This natural disturbance potentially impacts the ecosystems, including the Columbia River and may contribute to a suite of factors that impact the Salmonid populations.

Numerous other influences contribute to Salmonid survival during the sea-going stage, including a large variety of anthropogenic factors, many of relatively recent origin. Among these one of outstanding concern is fish farming. Areas of concern about salmon farming include the risk of escaped domestic fish interbreeding with wild Salmonids, the transference of disease associated with such contrived and intensive concentrations of fish, and the presence of artificially enhanced population sizes of sea lice (see

There is a relatively new potential threats as we can see from the fates of other species. In nearby Puget Sound, north of the Columbia delta, the production of oyster larvae went from a peak of 7 billion in the 2006 -- 07 season to less than a third as many by 2009, with similar catastrophic declines in shellfish up and down the coast. These coincide with indications of stunted growth in Alaskan king and tanner crabs. Evidence suggests the cause is likely increased acidification of the water. A senior scientist of the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory and the University of Washington, Richard A. Feely, has predicted that in about 36 years some fifty to 70 percent of the water will be corrosive (see

Such acidification will destroy the ability of small marine organisms with calcium-based shells or other calcium-dependent physiological components to survive, which, in turn, can deplete the foundation of food chains that end up with Salmonids, as well as whales, seals, cormorants and other species that may or may not be scapegoated.

The degree to which smolt survival is key to ultimate population goals is similarly unclear from the Plan. It is of particular concern as it is not only smolt survival that contributes to the fishery, but also other events in the marine environment. Positive fisheries management, which has resulted in the declines in fishery catch, seems to have led to increased populations of Salmonid populations overall.

The Plan's calculations on smolt survival in the lower Columbia lacks empirically derived estimates. The estimates in the Plan are based on unpublished, non-peer-reviewed and non-accessible data. Why would the authors of the Plan not access the arguably more reliable data set, provided by Passive Integrated Transponder tags (PIT tags)?

The following questions must be asked: If the purpose of the Plan is to enhance smolt survival, which smolt species are targeted for enhancement? Where are the scientific papers that demonstrate a carrying capacity of the river and estuary that can support a greater number of smolts and adults should they return as the Plan assumes? Given that there are other Salmonid predators such as terns, sea lions etc, why focus on cormorants? Indeed, are all opportunistic piscivorous species common in the region to be targeted.

There is a vast range in the amount of consumption of Salmonid smolts by cormorants in the Columbia River from year to year (see ) and yet fish biomass per cormorant, times the number of cormorants, is presumably more consistent. Thus opportunistic consumption would be tied to availability. The fewer smolt consumed, the more of other fish species which may be displacing competitors or predators of smolts.
As in any opportunistic predator-prey interaction, it is important for wildlife managers to know what species are consumed when smolt consumption is lower to make up the equivalent aquatic biomass consumed.

It appears, at the very least, to be possible that within a given population size of cormorants, consumption by the birds of predatory or competitive species within the overall Salmonid smolt habitat adjoining the Sand Island colony may be at least neutral, and possibly positive, in affecting Salmonid smolt survival. Certainly the range of species documented as being consumed by cormorants is vast, with numbers of individuals of given species determined by accessibility, thus availability.

The positive role of predators was very poorly, if at all, understood in the 19th century. We should do better in the 21st.

And yet I read that cormorant predation of smolt is comparable to the number of smolt lost to a dam. This contention totally ignores the difference between impacts of man-made devices such as dams on species verses natural ecological processes. Cormorant consumption of smolt is far more, and differently, selective, with said selectivity possibly benefiting smolt survival overall. Losses from dams are far more random than losses to predation by any species.

As well, the authors of the Plan admit that reduction of nesting cormorants may be counterbalanced by arrival of more Double-crested Cormorants, with no particularly significant decrease in the amount of consumption of whatever the cormorant is preying upon.

Cormorants prey on individual smolts, on individuals of species that would prey upon smolts, on individuals of species that would compete with smolts for resources, and on individuals of species whose presence or absence would have a neutral effect on smolt survival. That's inevitable.

I would further argue that what cormorants prey upon and in what number would also be a function of the number and availability of smolts relative to other species and that there remains an unanswered question as to what has been or is the limiting factor in cormorant numbers. Removing cormorants from the nesting site would not reduce consumption of whatever is being consumed. If it is food availability that limits cormorant numbers, there should be some indication of it (and none is given) as demonstrated by such indicators as reduced cormorant recruitment, a decline in mean weight of adult birds, etc.
Thus reducing nest site carrying capacity, as proposed, literally by making nesting a fatal option for a percentage of the cormorant population, will not necessarily, or even likely, reduce cormorant predation of any species (smolt, smolt competitors, smolt predators, or neutral species) any time soon, or ever, given the likelihood of compensatory mortality and subsequent immigration from other locations, which will counterbalance the losses from management action.

Such a Draconian action as the massive destruction of so many individuals of a native species is completely unsupportable given that cormorants have never been demonstrated to be responsible for, nor even implicated in, the loss of a single fish species or significant population of a single fish species anywhere.
Many government regimes talk about "sustainable" consumption of renewable resources, and then proceed to do no such thing. The current take of Columbia River Salmonid species by commercial or recreational fishers cannot be called "sustainable" so long as it is deemed necessary to augment the population with the addition of hatchery-raised smolts . The "average" number of Chinook Salmon sub-yearlings released into the environment may annually be around 75,000,000 (half way between the low of 50,000,000 and the high of 100,000,000 given).

What is more to the point, though, is the admission that even though some Salmonid species numbers are on the rise, there has been a steady decline in Salmonids overall "since the late 19th century", due to various anthropogenic factors that are, as we indicate above, increasing, both in number and in kind. Thus what Salmonids are experiencing is not different, in kind, than the losses of herring and other species in the Pacific region, as indicated above. The loss of major Salmonid stocks from the Okanagan River system, for example, had nothing whatsoever to do with cormorants (or Caspian Terns, sealions or other Pinnipeds, Orcas, mergansers or other natural predators).

Historically there were some ten to sixteen million Salmonids breeding in the Columbia River system. With fewer than two million anadromous Salmonids (not all Salmonids are anadromous) returning to spawn currently, there are millions not accounted for.

When Salmonids fail to recover after the killing of thousands of cormorants what other natural predator will be targeted as a causative factor impacting the Columbia River Salmonds? We can only speculate, and the Plan does not even do that. It is not as if fish declines only occur where there are cormorants. Freshwater Atlantic Salmon, once found in Lake Ontario, were completely exterminated when cormorants were absent from the environment. There is certainly no dearth of candidate causations for Salmonid decline, and fish stock decline of species that are not eaten by cormorants are certainly widespread and widely documented.

In Toronto, near where I am based, we have the largest Double-crested Cormorant colony in eastern North America, and it is managed, but without any lethal culling. While the Plan states non-lethal procedures to reduce cormorant smolt predation have been tried and failed, the Plan does not acknowledge that the killing of cormorants in other jurisdictions has also been tried and failed. The Plan is lacking in any scientific studies showing that cormorants negatively impact the fish biomass.

Because I do not think a case for reducing cormorants has been made in the first instance, I am reluctant to advocate for dispersal procedures, since I would prefer to focus on preventing known anthropogenic detriments to fish stock declines. That said, hazing techniques to prevent establishment of nesting (or, in other terms, to lower the capacity of the environment in question to accommodate nests) does work and has the added advantage of being relatively humane and possibly of not removing non-target species (such as Brandt's Cormorants). Hazing also has the benefit of being socially more acceptable, because it is more humane, than culling. Yet there is no indication in the Plan that a well-thought out hazing regime has been adequately tried.

I have long witnessed a scenario, now at play in the Plan, whereby a wildlife management agency assures itself that simply by removing "X" number of cormorants from a breeding colony (with "X" always being a significant percentage of the number present) a reduction to "Y" will occur, with "Y" always being a number that meets whatever the objective is, usually either to protect a given fish stock or age class within a given fish stock, and/or vegetation at risk, and/or other species dependent on that vegetation within the colony. It never works because the population is fluid and other birds will simply replace those removed, making culling a permanent management strategy.

Lastly, I would like to address the Plan's concern over the perceived threat of the Double-crested Cormorant to the local, endangered subspecies of the Horned Lark. After a life devoted professionally and otherwise to an appreciation of wild birds and dedicated to their survival, with species always valued over individual, I'm naturally concerned about the survival of an endangered local race of the Horned Lark. I believe that endangered species legislation in both our countries is correct and valid to the degree that it addresses survival at the taxon level, thus giving the subspecies consideration equal to that of the species. The last thing I would want would be to champion a common species at the expense of an endangered species or subspecies.

But I think it is disingenuous in the extreme to suggest that the activities of Double-crested Cormorants, in any way have a negative impact on the strigata race of the Horned Lark. There is nothing about the habitat requirements of the lark, which all literature sources I have referenced suggest are similar to the several subspecies I am familiar with, including those that nest in my home province of Ontario. In fact, I respectfully suggest that it discredits the document overall to imply that the Horned Lark is at risk from the presence of the Sand Island cormorant colony, or would be compromised by hazing and other non-lethal, non-culling procedures.

I strongly urge rejection of the "Preferred Alternative" as the case that reducing the number of cormorants on Sand Island will result in enhanced Salmonid smolt survival has not been made. Do not scapegoat the cormorants for the excesses of our own species.


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