Prepared on behalf of the Council of Great Lakes Fishery Agencies by
John Cooley (DFO), Margaret Dochoda (GLFC), Gary Isbell (ODNR), Bob Lange (NYDEC), Mike Staggs (WDNR), Roy Stein (GLFC), and Chris Wiley (DFO). 
Romulus, MI, 3 November 2000.
Accepted by Council 4 June 2001 in Windsor, ON.

Fishery agencies with responsibility for the Great Lakes have resolved to “¼ exercise their full authority and influence in every available arena to meet the biological, chemical, and physical needs of desired fish communities” (A Joint Strategic Plan for Management of Great Lakes Fisheries, 1997 revision). In a series of events triggered by the Lake Superior Committee’s 1988 discovery of ruffe and call for action to prevent further such introductions, Canada implemented a voluntary program for oceangoing ships of ballast exchange. Then, in 1990, with passage of the Nonindigenous Aquatic Nuisance Prevention and Control Act, the United States required ballast exchange or equivalent measures to commence in 1993. These measures have not proven sufficiently effective, and the Council of Great Lakes Fishery Agencies Fishery agencies is concerned that the biological integrity of the Great Lakes Ecosystem continues to be threatened by shipborne introductions of exotic species.

Ballast Management Insufficient to Safeguard Aquatic Communities

Two species that are thought to have established in the 1990s ballast management era are the predaceous cladoceran Cercopagis pengoi (MacIsaac et al 1999) and the amphipod Echinogammarus ischnus (Witt et al. 1997). Like several other well known ballast invaders, C. pengoi is a Ponto-Caspian species. It was first reported in Lake Ontario in 1998. As with the earlier shipborne invader, the predacous cladoceran spiny water flea (Bythotrephes cederstroemi), scientists are studying C. pengoi’s impact on zooplankton biomass. (Zooplankton is a common item in young fishes’ diets.) The 1990s amphipod invader, E. ischnus, is also from the Ponto-Caspian region. It was first discovered in the Detroit River in 1995, where it occupied a habitat typical of the native scud Gammarus fasciatus, suggesting the possibility of competition between the two species.

In addition to the two ballast invaders of the 1990s, other specimens have been reported confirming that the ballast vector continues to be active. European flounder (Platichthys flesus) was probably released with ballast water in 1993 or 1994 in Lake Superior (MacCallum et al 1995) and similarly in Lake Erie (Holm 2000). European flounder are regarded as an indicator of overseas ballast discharge since, while individuals originate from estuaries in northwestern Europe and can survive in the Great Lakes, they cannot reproduce in freshwater. Thus each specimen reported in the Great Lakes was itself introduced within a specified time frame (i.e., within the lifetime of the specimen, most likely in the first year of life). (P. flesus specimens have been reported periodically in the Great Lakes since 1974 (Crossman 1989).) A single specimen of yet another Ponto-Caspian amphipod, Corophium mucronatum (Grigorovich and MacIsaac 1999), is further evidence that the ballast vector continues to be active. This species can reproduce in freshwater, and is thought capable of colonizing the Great Lakes under suitable conditions.

What’s next?

Scientists predict that additional invasions will occur if effective safeguards are not placed on the discharge of ballast water from ocean-going ships. Ricciardi (1998) identified 17 species from the Ponto-Caspian region alone (including 1 polychaeteas, 5 mysids, 1 bivalve, and 3 fishes) that have high invasion potential and are likely to survive an incomplete ballast-water exchange and thus should be considered as probable future immigrants to the Great Lakes. He suggests that the suspension-feeding amphipods Corophium curvispinum and Corophium sowinskyi could significantly alter littoral communities and food webs in North American river systems. Ponto-Caspian mysid shrimp, are adapted to shallow, warm waters, and could potentially invade a large number of North American lakes that are currently devoid of mysid shrimps, reducing zooplankton thereby impacting planktivore fish, and biomagnifying contaminants such as mercury and PCBs. The tyulka, a Caspian herring (Clupeonella caspia), could also cause reductions of planktivores (coregonids, shiners, yellow perch) in the Great Lakes, and increase contaminant levels of piscivores in lakes currently devoid of pelagic forage fish. 

Of increasing concern are ‘fellow travelers’ or parasites and pathogens carried by introduced species (Ganzhorn et al. 1992) such as ruffe (Pronin et al 1997a, Pronin et al. 1998, Bronte 2000) and gobies (Pronin et al. 1997b). For example, fish pathologist fear that continued inoculations of previously introduced species, such as ruffe, may facilitate the introduction of potentially harmful parasites and pathogens, such as Viral Hemorrhagic Septicemia (VHS), which is not yet found in the Great Lakes. VHS, a serious disease of rainbow trout in Europe, which is carried by other fishes, may have been introduced to the Pacific Ocean via ballast (ICES 1989). An introduced parasite, possibly introduced with ballast water, may already be impacting Great Lakes zooplankton: elongated, transparent cysts, one of which was clearly Ellobiopsis, have been found in Lake Michigan crustaceans. Cysts and ellobiopsid parasites appeared suddenly on zooplankton in an inland Michigan Lake potentially explaining tumor-like anomalies (Bridgeman et al. 2000). Similar anomalies have been found in Lake Michigan zooplankton. 

[Human pathogens are known to be carried in ballast water (Ruiz et al 2000) but the risk to human health in the Great Lakes, if any, has not been determined.] 

There is evidence of multiple colonizations that could introduce new parasites and pathogens: the invasion of zebra mussels appears to have been founded from multiple population sources in northwestern and northcentral Europe (Stepien et al. 2001).

Purpose of Council Reference on Ballast

The Council of Great Lakes Fishery Agencies prepared this document

to serve as a reference for its members in advocating for the needs of Great Lakes fish and in commenting on initiatives for managing ballast water,

to share with the Great Lakes Fishery Commission, professional societies, and other entities similarly interested in protecting Great Lakes fish, and
to inform and motivate stakeholders.

This document is subject to revision by the Council as understanding of the ballast issue evolves.

Points of Consensus

Fishery professionals, their environmental colleagues, and concerned citizens can together ensure that policy-makers understand the long term interests of the Great Lakes region in deciding ballast management measures. The Council recommends that each of its members refer to this document when opportunities arise to advocate for more effective ballast management measures, for example when called upon to comment on proposed initiatives or changes in law, or to otherwise communicate on the problem of ballast water invaders:

1. Convey sense of indignation and issue a call for action: impacts on Great Lakes aquatic ecosystems are serious, large scale, and permanent.

2. Recognize that ballast exchange appears to have helped.

3. Be emphatic that end target must be zero – not a reduced rate of invasions.

4. Insist on a can-do attitude from Federal Governments.

5. Support a biologically meaningful ballast effluent standard and program of incentives and enforcement and accountability.

6. Support measures to protect the Great Lakes until fully effective, standards-based management implemented.

7. Make specific program recommendations.

8. Keep focused on measures needed to protect the biological integrity of the Great Lakes -- don’t be distracted by red herrings!

1. Convey sense of indignation and issue a call for action:
impacts on Great Lakes aquatic ecosystems are serious, large scale, and permanent.

Decision-makers are well informed by the shipping industry advocates on the impacts of proposed measures on their industry. Likewise there are panels and task forces that purport to balance economic and environmental needs of the Great Lakes region. It falls to fishery professionals, their environmental colleagues, and concerned citizens to speak on behalf of aquatic communities that we want to leave for future generations. 

While a full understanding of the impacts of ballast invaders usually takes decades, scientists are already working toward an appreciation of impacts, particularly of dreissenid mussels and predaceous cladoceran zooplankton (Shuter and Mason, 2000). Because the base of the foodweb is the main arena, where, for example zebra mussel is shifting production from pelagic to benthic communities, Diporeia, an important fish food, is disappearing, and Bythotrephes is consuming significant portions of zooplankton biomass, there is a particular need to educate on the impacts of lake-changing changes that can be wrought by introduction of a handful of barely visible organisms, i.e.,  overgrowth of rooted aquatic plants and algae, including toxic species (Microcystis), once thriving whitefish fisheries at risk, and less food for larval yellow perch and chub, etc. 

Fishery agencies represented on the Council of Lake Committees plan to develop communications on changes which are thought attributable to ballast invaders of the 1980s. In addition to those discussed above, impacts may also include the halving of Lake Erie landings, changes in contamination levels of fish, goby predation on smallmouth bass nests, cladoceran fouling of downriggers and fishing lines, ruffe dominance of rivermouth fish populations, beaches littered with sharp shells and rot, zebra mussel effects on the endangered Northern Riffleshell Clam etc.

"When I hear of the destruction
of a species, I feel just as if all of the works
of some great writer had perished."

-- Theodore Roosevelt

Perhaps most disturbing, the rehabilitation prospects for the Great Lakes are being diminished or transformed. The United States and
Canada have invested heavily in rehabilitating the Great Lakes -- through control of sea lamprey, phosphorus, toxic contaminants, and over-fishing. These successes should now be allowing rehabilitation of extirpated species and depressed populations. Instead, fish production is down, more aquatic populations and species (from Diporeia to threatened clams) are at risk, and rehabilitation opportunities are being lost to biological roulette where every discharge of ballast can contain a new species.

2. Recognize that Ballast Exchange Appears to Have Helped

Fewer species and specimens appear to have been introduced via ships in the 1990s than in the previous decade, a reduction likely attributable, at least in part, to the Governments’ introduction of ballast management measures. (Currently 162 exotic species have been introduced in the Great Lakes by various vectors including ballast water (Ricciardi 2001).) There are, however, other explanations for the apparent slowing of invasions in the 1990s (Simberloff and Von Holle 1999), and significant evidence that the ballast vector continues to threaten the biological integrity of the Great Lakes. Soon after implementation of the Canadian ballast management program in 1989, research sponsored by the Canadian Coast Guard showed that ballast exchange, while it might slow the rate of invasions, was not sufficiently effective to virtually eliminate ship-mediated invasions (Locke et al 1993). As discussed earlier, two new species are thought to have become established since ballast management commenced, and other specimens indicative of an active ballast vector have been recovered in the 1990s.

3. Be Emphatic That End Target must be Zero – not Reduced Rate of Introductions.

Decision-makers tend to think of regulation in terms of chemical pollution such as phosphorus and toxics which can, in appropriately small amounts, be disposed of safely by the Great Lakes ecosystem. While ballast water is truly a pollutant under the U.S. Clean Water Act and Canada Shipping Act, it is different from chemical pollution in two very important aspects: because living organisms reproduce and spread, biological pollution is persistence without parallel in the chemical sense. Thus, delaying introductions by a few decades is meaningless for longterm protection of Great Lakes biological integrity, unless borrowed time is used to continually tighten measures to prevent future introductions. Zero must be the target unless another scientifically derived threshold will be effective in preventing introductions. (With EPA and GLFC support, David Lodge, Notre Dame U., is researching the question of propagule pressure in order to provide a quantifiable, biology-based standard for ballast discharge effluent.) 

4. Insist on a Can-Do Attitude from Federal Governments

Great Lakes advocates should be wary of succumbing to shipping advocates’ pessimism regarding our collective ability to prevent ballast invasions. According to Eric Reeves (USCG, retired), “This is plumbing, not rocket science!” (He might have added that even were it rocket science, NASA put a man on the moon in 10 years!) Council members should also recall that auto emissions, smallpox, pollution and sea lamprey are just a few of the knotty problems that yielded to determined Governments.

One problem often cited is that of scale, i.e., that shipping is a global business. Council members may wish to remind decision-makers that by virtue of the huge U.S.-Canadian market, the U.S. and Canada, jointly, are in a strong position to influence global decision-making on ballast management. While preference is for coordinated action by Canada and the U.S., state/provincial action is also an alternative option for protecting the integrity of Great Lakes ecosystems.

5. Support a Biologically Meaningful Ballast Effluent Standard and
Program of Incentives and Enforcement, Timetables, and Accountability

Effluent standards must be biologically and not just technologically based or rationalized. As discussed above, research is underway to provide basis for biologically based standards. While technologically based standards (e.g., salinity, pump until break in suction) may be useful working tools, they must be rationalized against the biology of the organisms whose transfer we seek to prevent. 

While global standards are preferable, at the very least a ballast effluent standard for North American waters should be developed cooperatively by Canada and the U.S. Effluent standards are acceptable under admiralty law, and allowable for ballast management under the U.S. Clean Water Act (in litigation: Northwest Environmental Advocates; Center for Marine Conservation; and San Francisco Baykeeper vs. U.S. Environmental Protection Agency. Complaint for Declaratory and Injunctive Relief Administrative procedures Act (5 U.S.C. §§ 551-706)). 

With a program of incentives, enforcement, and accountability, standards can drive ship design, retrofit, and R&D. Industry is unlikely to take the initiative without leadership from the Governments in terms of timetables, incentives and enforcement and accountability, in support of  clear standards. In addition, Governments must assign unequivocal responsibility to their agencies, fund them adequately for the job, and require regular, science-based assessments of progress toward biological security in the Great Lakes. In 2000, the Great Lakes Fishery Commission recommended that the United States and Canada develop and implement a coordinated, adaptive 10-year strategy to end ship-mediated introductions.

Ballast management technologies recently discussed as having potential for retrofit of existing vessels include centrifuge filters, and heat, ultraviolet, and sound (‘boom box’) treatments.

Industry must begin now to design new ships for ballast management, if, in the ~40-year turnover time of the fleet, we are to have solved the problem of ballast introductions. At the very least new ships should be built in anticipation of mass-produced future technologies, i.e. ballast fixtures and available space should be standard and accommodating in every new ship. In addition every new ship should be built with the best available technology. For example, ballast tanks could be built with outlet and inlet for flow-through ballast exchange (safer for some ships). Tank reinforcements (‘rebar’) should be oriented to outlet and inlet to facilitate self-cleaning. Filters and other technologies can be field-tested and installed on new ships. An appropriate set of standards, backed up with a program of incentives, enforcement and accountability could ensure the best possible ballast program in tomorrow’s fleet, at the least possible cost. 

6. Support Measures to Protect the Great Lakes
Until Fully-Effective Standards-Based Management Implemented

Effective alternatives and supplements to ballast exchange are needed until the desired binational program of standards and timetables, incentives and enforcement, and accountability is in effect. Biocides such as chlorine should not be presumptively set aside, but any interim, specified use should be in the context of a protocol that minimizes any environmental damage. Ocean-going vessels not covered by the existing program, such as those declaring ‘no ballast on board’ and those with undetected, untreated ‘ballast on board’ (i.e., noncompliant) should be addressed. Because the Gulf of St. Lawrence may be lost as an option for emergency ballast exchange, alternative exchange arrangements, such as the IJC-proposed onshore treatment facilities, should be supported. Whether state or province, federal or international, biologists or industry, those seeking to protect the biological integrity of the Great Lakes should have our support.

7. Make Specific Program Recommendations

To protect the Great Lakes, fish and environmental advocates should not hesitate to specify the kinds of program that is needed. For example, Canada and the United States should establish partnerships based on formal agreements (convention or executive agreement) negotiated between Foreign Affairs and State Department to protect the Great Lakes,  to provide world leadership on world stage, and to provide clear accountability. 

Canada and U.S. are natural allies in ballast management: coastlines are contiguous and water is shared, shipping traffic is identical or very similar, the North American market is shared, and binational cooperation would maximize clout and credibility. The U.S. Nonindigenous Aquatic Nuisance Species Control and Prevention Act (1990) encourages the U.S. Secretary of State to initiate negotiations with governments of foreign countries re planning and implementation of prevention and control programs in shared waters. 

When faced with water pollution, Canada and the United States created the IJC and signed an executive agreement (the GLWQA) giving direction to their respective regulators. When faced with sea lamprey they created the GLFC, and charged it to minimize or eradicate the sea lamprey. A Ballast Commission or executive agreement on ballast or the reference requested by the IJC would give evidence that Governments are serious about protecting the biological integrity of the Great Lakes. The Great Lakes would be well served by a Clean Water Act effluent standard, plus an implementation schedule and system of incentives, supported by mechanisms such as a Great Lakes Ballast Commission, or reference to IJC to identify and implement interim measures to protect the Great Lakes.

Governments must provide adequate resources to stop ballast invaders. In 2000, the U.S. spent approximately the same amount nationally on ballast management as it did on Great Lakes sea lamprey. Moreover, U.S. ballast monies are scattered among programs in various agencies. In 2000, Canada had virtually no program on ballast water: the salary of an EPA coordinator of its ballast grants was greater than Fisheries and Oceans’ entire FY 2000 ballast program

8. Keep Focused on Measures Needed to Protect the Biological Integrity of the Great Lakes
(Don’t be Distracted by Red Herrings)

Many have put forward arguments that can distract from support of measures most likely to protect the biological integrity of the Great Lakes. Several are discussed briefly below:

“Blame the victim (if Great Lakes managed better, wouldn’t be invaded).” This argument leads to paralysis, and is losing traction among most biologists. Cleaner harbor waters here and elsewhere may have created opportunities for ballast invaders. In addition, scientists now hold that invaders such as zebra mussel create opportunity for their co-evolved fellows (gobies etc.). (Simberloff and Von Holle 1999).

“Blame another vector, e.g., aquaculture.” All vectors are and will be addressed. Ballast is, however, the most active vector in play today.  Arguably, new invaders that arrived in water transfers (canals, ballast, etc.) are proving the most disruptive in the Great Lakes ecosystem as a whole.

“Choose a regulator (national, international).” While international action makes sense, the interests of the Great Lakes demand that we support whomever can provide and implement an effective regime.

“Predict fiscal ruin.” Decision-makers should be reminded that all industries do this when confronted with potential regulation.

“Cite safety concerns.” Safety is important and should be maximized consistent with effectiveness. We cannot, however, allow the Great Lakes to be held hostage by shipowners who fly flags from countries that place the fewest constraints on operations. There is also human cost for not having effective ballast management: thousands died in the 1990s cholera epidemic in South America believed due to ballast discharge (Garrett 1994). 

“Let industry regulate itself.” While a regime of effluent standards and +/- incentives, may allow industry flexibility in choice of technology, Michigan’s Sen. Sikkema reminds us that no other industry nor municipality nor private citizen has enjoyed such freedom in disposal of its polluting byproducts.

“Focus on pathogens & known problem species.” It takes many years to tease out the mechanisms behind an accomplished problematic invasion, much less predict which of thousands will be a problem. Scientists recommend that the focus be kept primarily on the vector.

“Worry about lakers.” While fish managers appreciate Lake Carriers Association efforts to not facilitate secondary spread, lakers are not likely to introduce a new species except, possibly, when they take up ballast water in Montreal or further downstream. 

“Canada doesn’t have regulations.” Merely codifying current practices of the U.S. and Canada will not better protect the Great Lakes, and it may make it more difficult to introduce needed measures in future. Canadian regulations are only worth the effort if they improve protection.

“React or control introduced species, don’t prevent introductions.” It is rarely possible or cost-effective to control invaders by “chasing exotic species around North America throwing money in their wake” (Bob Lange, NYDEC). In the Great Lakes we control sea lamprey through applications of lampricide and alewife populations through salmon stocking, but no other species are tackled on an ecosystem scale.  Prevention needs emphasis over popular control efforts. 

“Use socio-economic analyses.” Traditional socio-economic analyses can undervalue preservation of public resource for future use (Bulte and Van Kooten 2000). As currently practiced, socio-economics is not the language of Aldo Leopold or Teddy Roosevelt, and will be used to negotiate down needed safeguards.



Bridgeman, T.B., G. Messick, and H. A. Vanderploeg. 2000. Sudden appearance of cysts and ellobiopsid parasites on zooplankton in a Michigan lake: a potential explanation of tumor-like anomalies. Can. J. Fish. Aquat. Sci. 57:1539-1544.

Bronte, Charles (USFWS). 17 July 2000 e-mail to M. Dochoda listing parasites introduced with ruffe: Tryponasoma acerinae, Dactylogi(Y??)rus amphibothrium, D. hemiamphibothrium (per Pronin et al. 1997a, Pronin et al 1998). Great Lakes Fishery Commission. Ann Arbor, MI.

Bulte, E., and G.C. Van Kooten. Economic science, endangered species, and biodiversity loss. Conservation Biology, pages 113-119, Volume 14, No. 1, February 2000.

Crossman, E.J. Platichthys flesus, European flounder, in the Great Lakes. App. VII of Minutes, Ballast Water Monitoring Workshop, St. Catherines, ON, 23-25 October 1989. Great Lake Fishery Commission, Ann Arbor, MI.

Ganzhorn, J., J.S. Rohovec, and J.L. Fryer. 1992. Dissemination of Microbial Pathogens through Introductions and Transfers of Finfish in Rosenfeld, A., and R. Mann (editors). 1992. Dispersal of Living Organisms into Aquatic Ecosystems. Maryland Sea Grant College, University of Maryland, College Park.

Garrett, L. 1994. The Coming Plague: Newly Emerging Diseases in a World Out of Balance. Penguin Books

Grigorovich, I.A., and H.J. MacIsaac. 1999. First Record of Corophium mucronatum Sars (Crustacea: Amphipoda) in the Great Lakes. J. of Great Lakes Research 25:401-405

Holm, E. 19 April 2000 e-mail to T. Johnson stating that “The specimen captured by Rob Dietz on 21 March 2000 in a gill net off Erieau, Lake Erie, has been confirmed as Platichthys flesus. It is catalogued as ROM (Royal Ontario Museum) 72241¼”

ICES. 1989. Report of the Working Group on Introductions and Transfers of Marine Organisms, Dublin, Ireland, May 23-26, 1989.  International Council for the Exploration of the Sea, ICES Palaegrade 2-4, DK1261, Copenhagen K DENMARK. 

Locke, A., D.M. Reid, and H.C. van Leeuwen, W.G. Sprules, and J.T. Carlton. 1993. Ballast Water Exchange as a Means of Controlling Dispersal of Freshwater Organisms by Ships. Can. J. Fish. Aquat. Sci. 50:2086-2093. 

MacCallum, W., Casselman, J.M., Furlong, P., and J. Leach. 1995. Correspondence on flounder and Chinese mitten crabs in meeting minutes of Council of Lake Committees. Great Lakes Fishery Commission, Ann Arbor, MI

MacIsaac, H.J., I.A. Grigorovich, J.A. Hoyle, N.D. Yan and V. Panov. 1999. Invasion of Lake Ontario by the Ponto-Caspian predatory cladoceran Cercopagis pengoi. Canadian Journal of Fisheries and Aquatic Sciences 56:1-5. 

Pronin, N.M., J. Selgeby, S.V. Pronina, and T. Darlen. 1997a. Effect of Parasites on Resistance to Oxygen Starvation in the Ruff (Gymnocephalus cernuus). Russian Journal of Ecology, Vol.28, No. 4, 1997, pp.314-316. (Translated from Russian. Briefly discusses 23 parasites in Lake Superior ruffe, some of which were introduced with ruffe.)

Pronin, N.M., G.W. Fleischer, D.R. Baldanova, S.V. Pronina. 1997b. Parasites of the recently established round goby (Neogobius melanostomus) and tubenose goby (Proterorhinus marmoratus) (Cottidae) from the St. Clai River and Lake St. Clair, Michigan, USA. Folica Parasitologica Vol. 44. No. 1

Pronin, N.M., J.H. Selgeby, S.V. Litvinov, and S.V. Pronina. 1998. The comparative ecology and parasite fauna of exotic invaders in the Great Lakes of the world: amur sleeper (Perccottus glehni) in Lake Baikal and ruff (Gymnocephalus cernuus) in Lake Superior. Siberian Journal of Ecology 5(5):397-406. (In the original Russian.)

Ricciardi, A., and J.B. Rasmussen. 1998 Predicting the identity and impact of future biological invaders: a priority for aquatic resource management. Can. J. Fish. Aquat. Sci. 55: 1759-1765. 

Ricciardi, Anthony. 9 May 2001 e-mail to M. Dochoda reporting count of 162 introductions in the Great Lakes. Great Lakes Fishery Commission, Ann Arbor, MI.

Ruiz, G.M., T.K. Rawlings, F.C. Dobbs, L.A. Drake, T. Mullady, A. Huq, and R. Colwell. 2000. Global spread of micro-organisms by ships. Nature. Vol. 48, p.49

Shuter, B.J., and D. Mason. 2001. Exotic invertebrates, food-web disruption, and lost fish production: understanding impacts of dreissenid and cladoceran invaders on lower lakes fish communities. A white paper prepared for the Board of Technical Experts (Great Lakes Fishery Commission) with support from the Great Lakes Fishery Trust and Ohio Sea Grant.

Simberloff, D., and B. Von Holle. 1999. Positive interactions of nonindigenous species: invasional meltdown? Biol. Invasions 1:21-23.

Stepien, C.A., C. D. Taylor, and K.A. Dabrowska. 2001 Population genetic variability and phylogeographic patterns of zebra and quagga mussels: exotic invasions and the “leading edge” hypothesis. (Submitted to Journal of Evolutionary Biology)

Witt, J.D.S., P.D.N. Hebert, and W.B. Morton. 1997. Echinogammarus ischnus: another crustacean invader in the Laurentian Great Lakes basin. Canadian Journal of Fisheries and Aquatic Sciences 54:264-268




Canada Department of Fisheries and Oceans
Chippewa-Ottawa Resource Authority
Great Lakes Fishery Commission
Great Lakes Indian Fish and Wildlife Commission
Illinois Department of Natural Resources
Indiana Department of Natural Resources
Michigan Department of Natural Resources
Minnesota Department of Natural Resources
National Marine Fisheries Service
New York State Department of Environmental Conservation
Ohio Department of Natural Resources
Ontario Ministry of Natural Resources
Pennsylvania Fish and Boat Commission
U.S. Fish and Wildlife Service
U.S. Geological Survey
Wisconsin Department of Natural Resources