MEMORANDUM

Tetra Tech, Inc.

400 Red Brook Blvd., Suite 200

Owings Mills, MD 21117

phone 410-356-8993

fax 410-356-9005

DATE: March 20, 2008

TO: Paul Shriner, EPA

FROM: Henry Latimer, Blaine Snyder, and Chris Millard

SUBJECT: Taxonomically-based fish species grouping scheme

As part of a larger effort to interpret potential impingement mortality and entrainment 

(IM&E) effects, it is desirable to organize fish species into groups with similar IM&E 

vulnerabilities. Ideally, these groups would comprise fish species with similar 

characteristics (e.g., swim speed, schooling behavior, reproductive and life history

characteristics) as well as habitat preferences (e.g., benthic vs. pelagic, river vs. lake, 

freshwater vs. estuarine). However, given the number of fish species potentially exposed 

to IM&E and the effort required to summarize relevant information to be used in 

grouping these species, a first effort based simply on taxonomy has been undertaken. 

The goals of this effort are to 1) help define the scope of the species grouping effort and

2) better understand the types of information required to successfully assemble species 

into meaningful groups. 

There are currently 3,694 fish species in North America (Nelson et al. 2004). 

Functionally, many of these species are not likely to be exposed to cooling water intake 

structures (CWIS) in the U.S., either because they occur only in Mexico or Canada or are 

pelagic marine species that are unlikely to occur in near-shore waters. The list of North

American fish species was screened to eliminate those that do not occur in the U.S. and 

those that are unlikely to occur in near-shore waters. Following this screening, 1,279 

species remain that could reasonably be expected to occur in the U.S. in the vicinity of 

CWISs and be exposed to IM&E related to those CWISs. This list includes all freshwater 
and most (if not all) estuarine fish. Future, comprehensive species grouping efforts will 

require that marine species be reviewed in greater depth to determine which species 

should be considered to be reasonably vulnerable to IM&E.

To minimize the number of fish species groups, the taxonomic level selected for use as a 

basis for groupings must be fairly general, but specific enough to capture meaningful 

morphological and habitat-specific differences among the various species. For this 

exercise, we selected Family as the appropriate level for use as the basis in establishing

groups. Dividing the groups based on Class was determined to result in species 

groupings that lumped clearly dissimilar species together. Groups based on Genera 

would be preferable in terms of lumping more similar species together, however such an 

approach yields so many groups (278) as to limit the utility of a grouping approach.

The family-level evaluation yields 72 different groups (see attached spreadsheet). It is 

likely that in refining this approach, similarities among some Families will be identified 

that will allow for several of these distinct groups to be combined. However, it is also 

known that variations in morphology and preferred habitat within some Families will 

require that those groupings be further sub-divided. 

Based on a brief analysis, it is possible that some species from differing families could be 

combined. For example, some members of the sculpin Family (Cottidae) would be able 

to be combined with some members of the Perch Family (e.g., darters), in that some 

species within each group exhibit similar, benthic habitat preferences. However, further 

investigation into habitat preferences, geographic ranges, and swim speed analyses is 

required before such groupings can be made. It is also likely that some, more diverse 

Families would require further division to more accurately represent the IM&E 

vulnerabilities of these groups. For instance, the minnow family (Cyprinidae) which 

contains carp, minnows, and pike minnows would likely have to be divided into at least 

three groups that are reflective of the diverse body sizes, habitats, and swim speeds of 

fish within this family. 

Thus, while a taxonomically-based species grouping effort is a reasonable initial step in 

grouping fish species in terms of IM&E vulnerability, there are clear shortcomings of this 

approach. To assemble larger and more inclusive species groups, the scientific literature 

must be evaluated to gather data on species-specific habitat preferences, geographic 

range, and swim speeds. Such information is required to determine whether the 

groupings based on potential IM&E vulnerability are similar to existing taxonomic 

groupings and, if not, how such groupings could be refined. Further, information should 

be assembled for more than one life-stage to ensure that the IM&E vulnerability of 

potentially more sensitive (but less well-studied) life stages (e.g., egg) are adequately 

addressed. It is likely that the scientific literature does not contain complete, relevant 

information for the majority (possibly the vast majority) of species. It is expected that 

this more in depth approach would be able to propose IM&E vulnerability values for a 

subset of all fish species. These values would then be extrapolated and applied to all 

taxonomically similar species within each group. The scientific validity of the final 
proposed grouping schemes would be directly dependent upon the amount of available 

species-specific data available in the literature. 

An alternative approach would be to refine the species list (currently 1,279 for freshwater 

and estuarine in the U.S. and 3,694 if all North American fish are included) based upon 

those fish that can reasonably be expected to be subject to IM&E. A judgment as to 

which species can reasonably be expected to be subject to IM&E could be made based 

upon an analysis of those fish species actually impinged and entrained through CWISs at 

representative facilities (e.g., encompassing intake types, sizes, and locations) throughout 

the U.S. Such data from facilities located in all geographic (e.g., Northeast, Southwest, 

Midwest) areas and water body types (e.g., river, lake, Great Lakes, estuary, marine) have 

already been collected and are available in state and/or EPA records. Evaluation of 

assembled impingement and entrainment (I&E) data would be expected to yield a much 

more limited list of species which are demonstrably subject to IM&E in the U.S. 

A list of species that are actually subject to IM&E would be useful for a variety of 

reasons. This list would be expected to represent a small percentage of all species in the 

U.S., thus enabling species grouping efforts to be streamlined, more relevant, and likely

more scientifically defensible. Such a list would also reveal real-world data that is 

directly relevant to species specific IM&E vulnerability which may be more useful that 

literature-derived data that may have questionable application in determining IM&E 

vulnerability. The resulting list would also allow alternative approaches to be explored to 

evaluate and regulate IM&E. Further, this list would allow EPA to make more informed 

decisions as to how IM&E regulations should be applied to various water body types and 

how the various water body types could reasonably be combined (e.g., address whether 

separation of lakes and rivers is appropriate or necessary).

We are optimistic that some type of species grouping scheme is possible. However, we 

believe that inclusion of actual I&E data is a necessary step to screen the list of all 

possible fish species to assemble a list of fish species that can reasonably be expected to 

be subject to IM&E. Using this revised list, a more appropriate and defensible IM&E 

vulnerability assessment could be made of each species, and reasonable species 

groupings could then be assembled with a fairly high degree of confidence.

Literature Cited

Nelson, J.S., E.J. Crossman, H. Espinosa-Perez, L.T. Findley, C.R. Gilbert, R.N. Lea, and 

J.D. Williams. 2004. Common and scientific names of fishes from the Unites 

States, Canada, and Mexico. American Fisheries Society, Special Publication 29, 

Bethesda, Maryland.