Comments filed by the American Ornithologists' Union

February 27, 2003

Jon Andrew, Chief
Division of Migratory Bird Management
US Fish and Wildlife Service4401 N. Fairfax Drive, Suite 634
Arlington,VA  22203

Dear Dr. Andrew:

This letter represents the official comments of The American Ornithologists’ Union on the Draft Environmental Impact Statement: Double-crested Cormorant Management issued in Fall, 2001.  The American Ornithologists’ Union is the oldest and largest scientific organization of professional ornithologists in North America, and for over a century has worked to improve understanding of the biology and natural history of birds, and to help provide fundamental scientific information as a basis for conservation and management.  In addition to our comments, we offer realistic alternatives for further study and action.

We conclude that the Draft Environmental Impact Statement (DEIS) is significantly flawed for the following reasons, detailed below.  In summary, we find that:

1)                  the scientific evidence supporting the proposed action is weak;

2)                  the analysis of the data is simplistic;

3)                  the proposed management plan is inadequate and ineffective;

4)                  the consequences of the proposed action are punitive instead of mitigatory; and

5)                  the assessment of success is based on public perception, and not on scientific results.

Furthermore, we find that the DEIS treats perceptions and sociology in the same way as scientific findings, confuses economics with natural history, and disregards geographic scale.  For these and other reasons detailed below, we do not support the proposed management plan, Alternative D, presented in this draft EIS. 

Cormorants are fish-eating birds, and that fact places them—along with all other fish-eating birds—into potential conflict with humans.  When we move our fish-related activities into those natural environments occupied by piscivorous birds such as cormorants, we introduce new interactions into a natural system.  The precise nature of the interactions can be specified with scientific study of the biological parameters, but the perceptions and the assessment of human impacts is based ultimately in sociology and in economics.  Any practical analysis of the cormorant-human problem must recognize the difference among these different components of the problem and analyze the impacts and mitigations in terms of the biology, the sociology, and the economics.  In our opinion, the DEIS has not done this.  Consequently, the solutions proposed in this plan are likely to have very mixed results, with the greatest variation at the smallest local areas.  At the largest scale required with this management plan, i.e., the continental U.S., the proposed management actions will fail.

Perceptions and Potential Areas of Conflict

It is clear that diverse members of the public are concerned about perceived conflicts between the natural activities of Double-crested Cormorants (DCCOs) and certain human values, including commercial fishing, sport and recreational fishing, and aquaculture.  It is important to evaluate these perceptions, evaluate the biological reality of the perceived conflicts, and  if these perceptions are warranted, create a reasonable management plan to resolve the conflicts. 

The potential areas of conflict include commercial fishing, sport and recreational fishing, aquaculture, and wildlife impacts.  The types of impacts that cormorants can have include predation of desirable fish, use of natural resources, use of human resources, public health and safety (by affecting water quality), interactions with other wildlife, and aesthetics.  Some of the potential impacts overlap and interact with others, and some may be local in effect while others may be noticeable throughout the distribution of the species.  Of the potential conflicts between cormorant and human resource use, predation of desirable fish is central to all of the other potential areas of conflict.  The other potential impacts are just as biologically relevant, but in this DEIS they are secondary and are used in a supporting role to the central theme that cormorant predation is directly responsible for fisheries declines. 

Cormorants and Aquaculture:  The impacts of piscivorous birds on fixed pond aquaculture are well known and have been the subject of numerous symposia here and in Europe.  The problem is particularly exacerbated in the U.S. because the greatest density of freshwater aquaculture development is located within the wintering range of cormorants and other waterbirds.  The DEIS hopes to address this problem with Alternative D, eliminating or at least mitigating the economic losses. 

Unfortunately, the current management plan has not worked very well, and the proposed plan (Alternative D), does not provide any support that it will improve the situation.  It will not work well for several reasons, as based on the evidence from numerous scientific studies.  First, controlling cormorants by lethal or non-lethal means is a very local affair, and every study to date shows that constant and continuing effort must be taken to keep birds off ponds.  The cormorants habituate to static or automated deterrents quickly, and killed birds are soon replaced from nearby.  Consequently, killing birds at roosts near aquaculture ponds is likely to create only short-term respite.  Second, although eliminating local breeding near aquaculture sites might be appropriate because of its potential local benefits in subsequent summers, it would have no effect on wintering numbers, and wintering numbers appear to be the more relevant issue.  Local reductions will have a miniscule impact on a continental scale, and thus the same problem will be revisited in the next season when new wintering birds appear.  Third, cormorants are not the only fish predator on aquaculture ponds; herons and pelicans have similar behaviors but not the numbers at present.  Selectively culling the most numerous species of fish predator—Double-crested Cormorants--from aquaculture ponds will only shift the problem to the other species. 

DCCOs are opportunistic feeders, and they are able to range over great distances particularly during the non-breeding season in search of food, preferentially aggregating at rich food sources.  As a consequence of localized culling, fish aquaculture and hatchery sites could become large population sinks, where killed birds are soon replaced by others seeking a rich food source.  The continuing influx of new birds means that aquaculture sites would become the last places for cormorant numbers to decline even when continental numbers are declining rapidly.  

As the Draft EIS acknowledges, prime foraging areas might be the last to be abandoned (p. 81), thus the proposed management option will focus intensive culling efforts on the most dynamic habitats.  In other words, we anticipate that this action will result in massive kills of Double-crested cormorants before any compensating effect is seen.  In fact, the DEIS states that the offered solution might fail completely because of the foraging and ranging behavior of the species (p. 82), but then concludes that, “nonetheless, population reductions would likely make efforts to manage … more effective.”   No explanation or evidence is provided for this conclusion, which typifies a serious problem evident throughout the DEIS.  Actions are proposed in this DEIS that are not justified by the result of scientific study.

Studies of Great Cormorants in Europe show that the key to limiting impacts to aquaculture is exclusion.  Aquaculture (and hatcheries as well) facilities can be designed with the means to exclude piscivorous birds from ponds containing fish.  Several alternatives have been explored, such as buffer ponds with fish species more preferred by cormorants, nets or wires, etc.  However, for the relatively larger aquaculture facilities found in the southern U.S., the costs of retrofitting with exclusion devises might be prohibitive.  In fact, using excluders such as wires can create an unacceptable hazard to fish-eating birds (entanglement followed by slow death).  It is clear that more creative solutions to exclusion are required, with experimental evaluation of their effectiveness.

Cormorants and Fisheries.  DCCOs were reduced to very low levels in the 1940s-60s by pesticides and removal programs.  When these constraints on population growth were released, the populations had the potential to rebound.  But for many now active in aquaculture and fisheries, their perceptual “baseline” was set when DCCOs were rare, so they consider current population abundances to be represent of outbreak.  It might in large part be a return to unsuppressed population levels.  Humans also have altered the feeding opportunities for DCCOs by building aquaculture facilities that house dense populations of fishes.  Of course these facilities will be attractive to efficient foragers such as DCCOs, similar to the deer attracted to the cornfield or the fox to the henhouse.  When humans choose to aggregate resources, we can expect wildlife to find those resources and to attempt to use them.   

Humans have also altered feeding opportunities for DCCOs in the wild.  In many systems, heavy fishing pressure has reduced the abundance of large predatory fishes, enhancing populations of smaller forage fishes.  Food web alterations have also led to increasing opportunities for establishment of non-native fishes such as alewife in the Great Lakes.  A century of scientific research on DCCO diet and feeding behavior data indicates that cormorants are attracted to schooling and slow moving fishes—they are also attracted to high densities of fishes as can occur when forage fishes are released from predation. 

The DEIS documents well a public perception by several sectors over the decline in creel catch of large game fishes such as small-mouth bass and yellow perch.  We agree with these findings insofar as they document a public perception and concern over a deteriorating situation in one type of public recreation and its attendant economics.  We disagree completely, however, with the contention that cormorants and their natural history are the cause of this problem, and that control by depredation is the answer to this problem. 

We fail to see the case for a major change in policy regarding public resources.  We have no doubt the recreational fishers perceive declines in the quality of their fisheries, but only 3 states reported that DCCOs predation was perceived to be of major importance to sport or commercial fisheries (DEIS section 4.2.2).  Eight states reported a perception of moderate importance.  Fisheries ecosystems are changing under a plethora of factors, only one of which is cormorant predation, and using cormorants as a scapegoat is not justified. 

Every study for about a century has shown that cormorants do not impact significantly the demography of desirable fish, except at very small scales.  The studies listed in the DEIS are no different.  The results of peer-reviewed studies show no significant impact by cormorant predation on desirable fish.  The other studies, which are not published in scientific journals and are issued without impartial external review, show equivocal findings.  Trapp et al. 1999 concluded that DCCOs have only a minor effect on sport fisheries.  The best evidence given for important effects of DCCOs on fish are mostly unpublished, equivocal or suggest only minor effects (EIS pages 50-51), see Table 1. 

            * all cited in the DEIS

     The last study in Table 1, the NYSDEC report, deserves special attention.  This report summarizes the results of 11 studies on creel surveys, diet analysis of cormorant pellets, and fisheries biology of the common and economically important fish in the eastern basin of Lake Ontario, including the waters around Little Galloo Island, New York.  The primary sources of data that associate cormorants with economically important fish species are diet analysis obtained from analysis of regurgitated pellets and analysis of regurgitated food from chicks and, rarely, adults.  Cormorants feed underwater and direct evidence of feeding activities is unobtainable.

Based on the results reported in this study, the proportion of smallmouth bass found in cormorants ranges from 0.4% of the total diet (1996) to 2.2% (1994), with the median amount around 1.0%.  The primary food item for Double-crested Cormorants, as in all cormorants, is small bottom feeding fish and other species not rated as highly desirable by sportsfishermen (e.g., alewife, trout perch, sculpin).  Smallmouth bass and yellow perch are taken in small and moderate amounts respectively, but very likely at size and age ranges unlikely to affect the population structure of these fish populations.  Fingerling mortality is quite high in the smallest size classes, and the additional take by cormorants even with increased populations has been shown to be a negligible impact on numbers.  These findings indicate a very minor role played by cormorants in bass and perch predation, but even these results must be viewed with caution.

Here, as in other studies of cormorant diet and feeding behavior, identification of food is by inspection of stomach contents.  Stomach contents can be obtained by necropsy of recently killed birds, by inducing the birds to regurgitate food, or indirectly by analysis of regurgitated pellets comprising inedible components such as bones, gravel, crustacean shells, etc.  If the fish are still intact, their identification can be done by inspection and comparison with preserved specimens.  Intact fish in stomach contents are rare; much more commonly, the fish are partially or completely digested, and identification has to be done using bony elements—usually otoliths (an ear bone), very rarely parts of the skeleton.  Unfortunately, bony elements are themselves digested within the stomach, and the longer the contents remain the less likely they can be identified. 

The evidence shown that purports to reconstruct the size classes from otolith size is presumptive and speculative.  The association between freshly dissected otoliths and body size of the bass and perch they came from is significant—as is found usually for other species of fish.  This fact forms the premise for diet reconstruction from food samples and pellet regurgitations, i.e., otolith identification and measurements will reveal what fish species the bird predator has eaten.  Further, in this study it is hoped that by measuring the size of otoliths contained in regurgitated food and pellets, it will be possible to reconstruct the size of the fish.  There are several problems with this approach as pointed out in the report. 

First, the identification of the otoliths by species is easiest with undamaged otoliths from large fish.  Reliable identification becomes increasingly difficult with younger age-classes of fish (i.e., smaller otoliths).  It is particularly difficult when the otoliths (of any size) are degraded by digestive action in the cormorant stomach, and key identification characters and dimensions are obscured.  The longer the otoliths are digested, the more variable the results.  As is pointed out in the report, otoliths from small-sized smallmouth bass are nearly indistinguishable from small size classes of other species of fish; furthermore, the longer the otoliths were digested, the more problematic their identification.  Compounding the error, most of the studies offered here to support the contention that cormorants have a negative impact on smallmouth bass are based on very small sample sizes. 

It is standard practice in peer-reviewed publications to provide evidence for identification accuracy and precision of results.  This publication was not peer-reviewed, and perhaps as a consequence this evidence is lacking.  Nowhere in this report is there an attempt to quantify or address the variation in size of otoliths and identification, the effects of digestive degradation on identification, or what accuracy in identification was achieved.  We are quick to point out that we do not impugn the motives or the competency of the researchers associated this study.  Given the evidence presented in the report, however, we cannot accept the findings with confidence.  Based on the information presented in this report, it is impossible to determine with accuracy what species or what size class of fish correspond to the otolith data.  These data are unsubstantiated, presented without adequate controls or error assessment, and are ambiguous and unverifiable. .

The peer-reviewed papers cited on Table 1 suggest no significant effects unless DCCO densities are extremely high – what constitutes “extreme” would probably change by situation, and would require demonstration of an impact by DCCOs.  Other observations are unpublished or in state reports.  These case studies are detailed in Appendix 5 of the DEIS, but the data, taken as a whole, are at best equivocal.  This does not imply that there cannot be localized conditions where DCCOs are problematic, but the evidence demanding a change in the current management DCCO approach appears to be driven entirely by perception and not by scientific reality.  Many factors contribute to variation in recreational fisheries catches and the systems where perceived problems are the greatest are highly altered by overfishing, exotic species invasions, stocking of apex predators and perhaps climatic variability.  To single out cormorants as the cause of these perceived problems is not justified by the science reviewed in the EIS.

In reality, management is driven by perception and public comment.  And the values expressed by the public drive the policy making process.  If policymakers choose to support aquacultural production by allowing shooting of DCCOs, that becomes policy.  But for recreational fisheries there is so little evidence to support the idea that DCCOs at current levels are a problem, that the USFWS should allow killing only when a specific case can be made in a particular location.  We are extremely concerned that the evaluation of damage mitigation is not based on scientific findings but public perception (p. 77).  A perception driven policy without scientific evidence runs counter the legal mandates of the agency.

In conclusion, the only documented cases where cormorant predation has been shown convincingly to reduce availability of desirable fish are those where cormorant populations are very high and where the water bodies were isolated impoundments where fish recruitment is artificial and dependent on hatchery fry (Oklahoma).  We do not see that such localized problems require a change in federal management policy on a national scale. 

Water Quality.  We cannot reconcile the statements in the DEIS that local water quality will improve under the proposed action (section 4.5.6, p. 73) with the evidence provided here and elsewhere that show that this is not an issue.  Cormorants have not been shown to have deleterious effects on water quality or on public health, except at miniscule scales (e.g., in a colony, beneath a roost).  To imply otherwise is misleading and provocative. 

Alternative plans and management actions

We do not find that the alternatives listed in the DEIS constitute an adequate approach or a new approach to the human-cormorant problem.  Six alternatives are listed and comprise various combinations of six discrete actions (Table 2).  Only two of these actions differ from the existing ones in use (i.e., Public Resource Depredation Order, Hunting Season) and one of these (expanded Aquaculture Depredation Order) is a modification of one in use.  Our comments on each of the component actions follow,

* existing actions and Alternative. 

NLM (Non-lethal Management): Controlling cormorants by non-lethal means is effective, but every study to date shows that constant effort must be taken to keep birds off aquaculture ponds.  Because cormorants habituate quickly, harassment or passive deterrents (flashing lights or decoys) lose effectiveness.  Exclusion devices are effective, but current applications are expensive and economically impractical at large scales. 

ADO (Aquaculture Depredation Order): Double-crested Cormorants can be killed at commercial freshwater aquaculture facilities and state fish hatcheries in 13 states without permits or regulation.  Other states and localities take is done under authority of a Depredation Permit administered by the USFWS regional offices.  The take is required to be monitored, and breeding populations surveyed at 10-year intervals.  We do not believe that the ADO is effective.  As adjudged by the participants in the ADO, the results have not been satisfactory and the negative perception of cormorant predation is unchanged.  Furthermore, we are not convinced that the current monitoring system returns accurate data in a timely fashion

ADO-E (Expanded Aquaculture Depredation Order): In addition to the provisions of the existing ADO, expansion would include killing at winter roosts, and at Federal fish hatcheries.  This expanded action adds localities in 13 states where unregulated take of cormorants may occur.  It adds localities in other states as well, and the take is regulated by Depredation Permit as in the ADO. 

PRDO (Public Resource Depredation Order): This will allow unregulated take in 13 states as before, but does not restrict localities or circumstances.  All activities will be done at state and local levels.  Federal oversight is limited to reporting and monitoring.  In other states, killing is regulated by Depredation Permit, but localities or circumstances are not restricted.  In other words, this action would allow local unregulated cormorant control with only passive oversight at the Federal level

DP (Depredation Permits): These are issued by USFWS for take of cormorants in states other than the 13 listed in the ADO, ADO-E, or PRDO.  As these are issued on a case-by-case basis, DPs are likely to be responsive to local conditions.  The evidence does not support widespread success of DPs, but in some cases permittees have been satisfied with result

HS (Hunting Season): Hunting seasons and bag limits would be established in states and federal lands.  There is no evidence to suggest that this likely to be a popular action, and previous approaches indicates that opening hunting on cormorants would considered be undesirable by wildlife managers and hunters alike, and unlikely to have any significant impact. 

Alternative A, the current plan, does not work.  Alternative D, the proposed plan differs from Alternative A essentially only in the scale of killing.  Since all control would be made locally, and there is no enforceable provision for coordination, this will have very undesirable consequences.  Local extirpation will have only temporary effects as birds from neighboring areas can replace them.  Local pressure to control cormorants can result in large numbers of birds killed for local reasons, without oversight.  We see no essential differences in the other Alternatives, other than in scale.

DCCO Population Models and Monitoring

Ignoring for the moment that the DEIS has failed to demonstrate a problem caused by DCCOs that needs a response, and that the DEIS has failed to demonstrate that the proposed Alternative would resolve perceived problems, the population models and monitoring plans also are inadequate to evaluate the supposed effects of the proposed Management Alternatives. 

The DEIS does not provide evidence that any specified reduction in DCCO numbers could be achieved, or that the USFWS would have sufficient data to know what population trends are occurring.  It is necessary to have in place a system of measuring changes in actual (not perceived) impacts associated with different management actions, and a specific feedback mechanism that alters management performance as specific, defensible target numbers are encountered.  This must be more that counting the number of complaints.

The DEIS points out that there are five subspecies of DCCO, that the problems associated with DCCOs are not evenly distributed among the subspecies, and that the increased depredation proposed will affect the subspecies unevenly.  However, all evaluations of the potential management alternatives and impacts are made treating DCCOs continentally.  This is not acceptable.  Modeling should occur at least at the subspecies level, and should be more sophisticated.  Since monitoring must be addressed regionally, regional models would allow more efficient adaptive management.

For example, even though the USFWS has data on variances in life-history parameters, the population models are not stochastic.  The population growth rate modeled assumes a growth rate (6.2%) that comes from a period of rapid population growth.  As is stated in the DEIS, density dependence can be expected, so it would be important to include some estimate of carrying capacity and density dependent feedback to see how they affect modeled results.

If the model results and kill estimates from the DEIS that are required to created a decline in DCCOs are to be believed, in the early years of control up to 250,000 DCCOs would need to be killed each year, and tens of thousands of nests would have to be oiled.  This would be an enormous effort and cost, and is probably impractical. For example, some of the presented model results  require oiling 50% of the nests, and the disruptions caused to the breeding colonies by these activities have not been included in the modeling exercises.  For example, such disruptions may cause cormorants to move and nest in different sites, thereby exacerbating the problems.   Furthermore, at 4 pounds per bird on average, Alternative D proposed in this DEIS will result in about a million pounds of dead birds each year.  How will these carcasses be dealt with?  It is not clear that the preparers of the DEIS have thought through the implications of the suggested alternatives.

The DEIS concludes that the cumulative effects of the recommended management action could threaten DCCO populations, but “would be carried out in such a way that risks to viable regional and continental DCCO populations would be minimized (e.g., through the use of population goals and monitoring.” (p. 88).  However, no viability analyses beyond a simple continental model were done, and no population goals were provided beyond not letting the continental population drop below 60% of their current size, without any consideration of regional limits.  Furthermore, more than half of the Double-crested Cormorant populations breed in Canada, and we see no discussion at all relating to the international implications of this action.

Currently, and with the proposed management action, depredation and by-kill are not required to be reported by those with depredation permits except when requested.  There appears to be no mechanism in place to verify and evaluate the accuracy of the data on reported take and by-kill. This will not allow the USFWS to adequately evaluate depredation effects and alter management as population goals are neared.  Proposed management plan allows for state and tribal issuance of depredation permits, along with the current federal issuance.   Based on current experience, it is clear that this would be very difficult to control, regulate, and monitor. 

There are many problems in the monitoring section (pp. 75-77) of the DEIS.  For example, the DEIS reports that there are 10 of monitoring systems already in place that might be used for DCCO monitoring, and that one could look for similar trends in more than one monitoring scheme to get a real feel for what is happening to the population.  However, all of the approaches are not equal in their abilities to detect a trend, so they should not have equal weight in making management plans.  Specifically, methods (B), (C), (D), and (F) look ineffective for DCCOs, method (C) will work well only with large numbers of marked birds, and appropriate distribution of banding effort in time and space, and methods (D) and (F) don’t give information that would allow USFWS to detect a decline in numbers, only in range, and no range criteria for adaptive management are presented.  Counts of colonies and roosts (E and I) can be effective but have not yet been implemented on the appropriate scale, which is throughout the range of the species because the likely effects of killing many cormorants will not be limited to local areas.  In fact, continental colony counts would require extensive collaboration with Canadian Provinces.

The DCCO Management EIS should include specific details about a monitoring plan, including (1) biologically defensible local target goals for population decline, (2) a statistical power analysis to determine the intensity, locations, and frequency of counts to demonstrate that target declines can be detected, and (3) specific management actions that will occur if the target population decline is achieved or exceeded.  The monitoring plan needs to include areas where DCCOs breed and winter that are not in “problem” areas to determine if local DCCO killing is having undesired results elsewhere even if there is no decline in control areas.  Given the foraging behavior of DCCOs, this could occur.  These non-control areas should also have biologically defensible target declines in population size below which killing elsewhere would stop. 

Possible directions and mitigating actions

First, public perceptions and public attitudes related to the natural history of cormorants need to be addressed.  It would be a grave mistake in our opinion to proceed with a biological approach to a problem that likely is one of sociology and economics.  We suggest that an aggressive, pro-active program of research, public education, and outreach be undertaken on a regional and national scale.  Scientific research on the environmental sociology of cormorant-human interactions needs to be done, and it will be critical that experts in sociological research conduct these studies.

Second, serious attention must be given to finding innovative and economically appropriate methods for exclusion of all piscivorous birds at fixed site facilities, such as aquaculture ponds and hatcheries.  Retrofitting existing solutions has not proved to be as successful as needed, and where aquaculture ponds are extensive and large, as in the delta region of the southeastern US are clearly impractical.  New solutions are needed.

Third, further study is needed to understand better the causes and possible mitigation of declining yields in sport-fishery.  Single-factor explanations for complex phenomena are unlikely to be helpful in finding solutions to problems that affect people’s recreation or livelihoods.  We believe that regional consortia of fisheries scientists, ornithologists, hydrologists, and those in allied fields working together are the best solution to gathering relevant scientific information.

Fourth, we believe that there are management options that are available and can be undertaken immediately.  We believe that the actions described under Alternative C with modifications can serve as an effective first step for management of human-cormorant conflict.  Specifically, that the federal government continue Non-Lethal Management and Depredation Permits as currently administered, and that the Expanded Aquatic Depredation Order as described in the DEIS be authorized.  The evidence does not support control at winter roosts as being effective or having the desired consequences, and we believe that it should not be allowed.

We hope that these comments are useful as guidance on this difficult issue.

Sincerely,

On behalf of the American Ornithologists’ Union

J. Michael Reed, Ph.D., Chair, Tufts University

Douglas Causey, Ph.D., Harvard University

Jeremy Hatch, Ph.D., University of Massachusetts, Boston

Fred Cooke, Ph.D., Simon Fraser University (retired)

Larry Crowder, Ph.D., DukeUniversity

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