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### 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 L isa Biddle , EPA FROM : Blaine Sn yder , Henry L ati mer, and Kell y Meadows , Tetra Tech SUBJECT: Fragile Fish Species EPA is re viewing approaches for including or excluding certain fish species from some impingement mortality (IM) requirements based on fragility , a concept suggested in comments
. Inthis analy sis, we characterize those fish identified in IM studies used in developing the IM performance standards base d on their relative fragility
. Specificall y, EPA reviewed the species

- specific mortality data f rom 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
. T hese 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 anc hov y . 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 att ached spreadsheet. The corroborating a pproaches are based on expert biologist opinion , and compared to existing impingement survival information. Th e first anal ys is 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 identif ies those species that are considered particularly fragile because they

are the least likely

to survive stresses associated with impingement (e.g., the top thi rd 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 atta ched spreadsheet , which used a sampling of IM studies to develop a list of commonly impinged fish and then assessed their2

hardiness
. We used red, yellow, and green highlights to tag species as particularl y fragile, somewhat fragile, and rather hardy in an IM context, respectively
. T he red category

includes some species that should be universall y recognized as fragile, such as the anchovies and the herrings
. O thers like mackerel and bluefish were included in the red category

because they ’re fast

- swimming pe lagic predator species that by nature are constantly

moving and are unlikel y to tolerate the “inactivity” of being impinged. T he Salmonidae (trout and salmon) and Anguillidae (American eel) are highlighted in yellow because, depending on conditions and lif e stages, they can be somewhat fragile (e.g., American eel IM s urvival rates can vary widel y)
. 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 g eneralizations were not necessary to identify

the most fragile (least hardiness categories ) as highlighted in the spreadsheet. After completing this analy sis , we conducted a second anal ys is 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. EPRIsummarized impingem e nt survival data b y 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 appar ent overall potential for surviving impingement in prior studies
. They noted that these e stimations should only

be used as an approximation of survival. We re - classified all species based on the EPRIfish family

ratings and inserted those classifications a s 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 anal ys es , particularly for the low s urvival (or fragile) category
. Nearly all of the species identified from the IM studies as fragile are also identified as fragile in the Tt anal ysis; 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 analy sis but all belong to a family identified by EPRIas being fragile. As a result, the analy sis supports the draft definition and list of fragile species. Similarly , th e EPRIdata also supports the draft definition and resultant list of fragile species. The EPRI anal ys is identified families of fragile fish; this broad er approach identified each of the species identified b y EPA in reviewing studies for the IM performance standards , and resulted in a virtuall y identical list of species
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This revised anal ys is also generall y agreed with the EPRIanal ys is. We highlighted 14 fragile species, 12 of which were in families identified as having a low survival rate potential by

EPR I ; the other two (mackerel and Spanish mackerel) were in families identified as having an intermediate survival rate by EPRI
.