
                                  MEMORANDUM

Tetra Tech, Inc.
10306 Eaton Place, Suite 340
Fairfax, VA 22030
phone	703-385-6000
fax	703-385-6007

DATE: 		March 15, 2012; revised February 26, 2014

TO:			Paul Shriner and Lisa Biddle, EPA
	
FROM:		Blaine Snyder, Henry Latimer, and Kelly Meadows, Tetra Tech

SUBJECT:	Fragile Fish Species

EPA is reviewing approaches for including or excluding certain fish species from some impingement mortality (IM) requirements based on fragility, a concept suggested in comments. In this analysis, we characterize those fish identified in IM studies used in developing the IM performance standards based on their relative fragility. Specifically, EPA reviewed the species-specific mortality data from the studies that were used to develop the IM performance standard. (See the Technical Development Document for more details.) From that data, any species that exhibited a survival rate of less than 30% was deemed to be fragile and were then excluded from calculations for the performance standard. These species are: alewife, American shad, Atlantic herring, Atlantic long-finned squid, Atlantic menhaden, bay anchovy, blueback herring, bluefish, butterfish, gizzard shad, grey snapper, hickory shad, menhaden, rainbow smelt, round herring, and silver anchovy. These fragile species are specifically named in the regulatory language.

EPA corroborated this approach using two independent approaches; these approaches to defining the "fragility" of species subjected to impingement are summarized in the attached spreadsheet. The corroborating approaches are based on expert biologist opinion, and compared to existing impingement survival information.

The first analysis assumes that all fish were late juveniles or adults. It's difficult to craft a specific definition for "fragile" in this context, but one approach identifies those species that are considered particularly fragile because they are the least likely to survive stresses associated with impingement (e.g., the top third of the species on a theoretical impingement mortality gradient). Even with a definition of "fragile" and/or a threshold for distinguishing fragile and non-fragile species, there would still be some intermediate species. This is reflected in the attached spreadsheet, which used a sampling of IM studies to develop a list of commonly impinged fish and then assessed their hardiness. We used red, yellow, and green highlights to tag species as particularly fragile, somewhat fragile, and rather hardy in an IM context, respectively.

The red category includes some species that should be universally recognized as fragile, such as the anchovies and the herrings. Others like mackerel and bluefish were included in the red category because they're fast-swimming pelagic predator species that by nature are constantly moving and are unlikely to tolerate the "inactivity" of being impinged. The Salmonidae (trout and salmon) and Anguillidae (American eel) are highlighted in yellow because, depending on conditions and life stages, they can be somewhat fragile (e.g., American eel IM survival rates can vary widely).

Impingement survival can vary within species based on life stage, ambient conditions (e.g., water temperature or season, salinity, etc.), and intake conditions (e.g., amount of debris on screens, type of screen, screen wash frequency, screen travel time, etc.). However, late juvenile and adult species identified as fragile species are still categorized as fragile regardless of the other conditions, life stage, ambient conditions, and intake conditions. Therefore, other generalizations were not necessary to identify the most fragile (least hardiness categories) as highlighted in the spreadsheet.

After completing this analysis, we conducted a second analysis that compared EPRI's estimates of impingement survival for fish families (as found in Impingement and Entrainment Survival Studies Technical Support Document. EPRI, Palo Alto, CA. 2005. Technical Report #1011278) to our species ratings. EPRI summarized impingement survival data by fish family, and separated families into three categories: high survival rate potential (71-100%); intermediate survival rate potential (31-70%); and low survival rate potential (0-30%). EPRI based their survival estimates on the apparent overall potential for surviving impingement in prior studies. They noted that these estimations should only be used as an approximation of survival. We re-classified all species based on the EPRI fish family ratings and inserted those classifications as a separate column in the attached spreadsheet.

Conclusion

There is good general agreement in fragile species ratings between the list of fragile species in the draft regulation and the two independent analyses, particularly for the low survival (or fragile) category. Nearly all of the species identified from the IM studies as fragile are also identified as fragile in the Tt analysis; the exceptions are the Atlantic long-finned squid, grey snapper, hickory shad, round herring, and silver anchovy. None of these species were identified in the Tt analysis but all belong to a family identified by EPRI as being fragile. As a result, the analysis supports the draft definition and list of fragile species. 

Similarly, the EPRI data also supports the draft definition and resultant list of fragile species. The EPRI analysis identified families of fragile fish; this broader approach identified each of the species identified by EPA in reviewing studies for the IM performance standards, and resulted in a virtually identical list of species.

This revised analysis also generally agreed with the EPRI analysis. We highlighted 14 fragile species, 12 of which were in families identified as having a low survival rate potential by EPRI; the other two (mackerel and Spanish mackerel) were in families identified as having an intermediate survival rate by EPRI.


