Document ID: EPA-HQ-OW-2002-0049-0159
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2003-03-19T05:00Z

SC10077
Memorandum
To:
Lynne
Tudor
and
Tom
Wall,
U.
S.
EPA
From:
Elizabeth
Strange
and
Dave
Cacela,
Stratus
Consulting
Inc.

Date:
6/
28/
02
Subject:
Responses
to
Riverkeeper
Questions
About
the
§
316(
b)
Phase
II
Case
Study
I&
E
Analyses
1.
I
am
looking
at
the
impingement
data
used
in
the
example
of
316b
and
I
have
a
problem.
I
have
been
trying
to
calculate
the
figures
given
in
Table
B4­
2.
I
have
gone
back
to
the
source
Tables
B3­
2
and
B3­
3
and
the
Salem
input
Excel
sheet.
I
can
get
the
annual
impingement
data
to
tally
in
Table
B3­
2
by
use
of
the
adding
the
age
1,
and
Juvenile
1
and
2
fish
from
the
Excel
sheet.
I
then
try
to
move
on
to
get
the
age
1
equivalents
in
Table
B3­
3.
For
each
year
I
calculate
the
Year
1
equivalent
of
the
life
stage
of
interest.

For
example
take
1978
for
weakfish
Action
Juv
1
Juv
2
Age
1
Total
From
Tab.
6,378,530
11,260
1,466
6,391,256
I
cannot
get
from
these
values
to
the
total
age
1
equivalents
of
237,865.
Accepting
that
as
correct
I
cannot
get
from
the
mean
age
1
equivalent
of
65,182
to
the
value
given
in
the
Table
B4­
2
of
55,856.
I
have
tried
following
your
model
in
Section
A5­
3
but
I
cannot
get
it
to
work.
Could
I
have
a
spreadsheet
showing
the
calculations
of
a
single
species
such
as
the
weakfish
from
raw
data
to
the
year
1
equivalents?

A
complete
elaboration
of
the
calculation
of
age
1
equivalents
is
provided
for
the
reviewer's
convenience
in
Tables
1­
4
below.
Table
1
reports
the
life
history
parameters
that
EPA
used
for
modeling
weakfish
at
Salem.
These
values
are
included
in
the
workbook
"
salem.
input.
data.
xls"
(
DCN
4­
2051).
Table
1
also
shows
the
associated
survival
rates
that
EPA
derived
from
the
basic
life
history
parameters
using
methods
described
in
Chapter
A5
of
Part
A
of
the
Case
Study
Document
(
DCN
4­
0003).
Table
2
provides
further
elaboration
of
the
values
presented
in
Table
1,
and
gives
an
explicit
elaboration
of
how
stage­
specific
survival
rates
are
combined
to
give
effective
stagespecific
survival
rates
from
the
age
of
entrainment
until
age
1.
Table
3
reports
the
stage­
specific
1978
impingement
losses
of
weakfish,
which
are
included
in
the
workbook
"
salem.
input.
data.
xls"
(
DCN
4­
2051).
Table
4
associates
the
values
in
Table
2
and
Table
3
to
provide
a
stage­
specific
accounting
of
age
1
equivalent
losses
and
indicates
where
the
values
so
derived
were
reported
in
the
Salem
case
study
(
Part
B
of
the
Case
Study
Document).
Stratus
Consulting
Memorandum
(
6/
28/
02)

Page
2
SC10077
Table
B3­
3
of
the
Case
Study
Document
(
DCN
4­
0003)
reports
the
mean
annual
number
of
weakfish
age
1
equivalents
as
65,182,
which
summarizes
weakfish
losses
during
1978­
1998.
Table
B4­
2
reports
the
mean
annual
number
of
weakfish
age
1
equivalents
as
55,856,
which
summarizes
losses
that
occurred
during
1995,
1997,
and
a
1998
(
as
presented
in
Table
B3­
18).
The
latter
time
period
was
selected
to
represent
the
current
baseline
losses
at
Salem
for
reasons
described
in
Section
B3­
7
of
Chapter
B3.

Table
1.
Stage­
specific
weakfish
life
history
parameters
(
M,
F,
fraction
vulnerable
to
fishery)
used
to
derive
stage­
specific
weakfish
survival
rates
(
Sj)
at
Salem.

Life
history
parameter
Life
stage
(
j)
M
F
Fraction
of
life
stage
(
j)
vulnerable
to
fishery
F
adj
1
Z
=
M+
F
adj
S
j
=
e­
Z
S*
j
2
Egg
1.043
0.00
0.00
0.00000
1.0430
0.3524
0.5211
Yolk­
sac
larvae
1.341
0.00
0.00
0.00000
1.3410
0.2616
0.4147
Post
yolk­
sac
larvae
6.3325
0.00
0.00
0.00000
6.3325
0.0018
0.0035
Juvenile
stage
1
2.439875
0.00
0.00
0.00000
2.4399
0.0872
0.1604
Juvenile
stage
2
1.483788
0.00
0.00
0.00000
1.4838
0.2268
0.3697
Age
1
0.348575
0.25
0.10
0.02237
0.3709
0.6901
0.8166
1.
F
adj
represents
fishing
mortality
rate
(
F)
adjusted
for
fraction
of
age
class
vulnerable
to
fishery.
2.
S*
j
represents
the
stage­
specific
survival
rate
(
S
j)
adjusted
to
account
for
the
fact
that
the
precise
within­
stage
age
of
entrained
fish
is
unknown.

Table
2.
Elaboration
of
Equation
4
of
Section
A5­
3.1
of
the
Case
Study
Document:
Example
derivation
of
Sj,
1,
the
stage
specific
cumulative
survival
rate
(
as
a
fraction)
from
stage
at
entrainment
(
j)
to
age
1
for
weakfish
entrained
at
Salem;
the
definition
of
Sj,
1
includes
accommodation
for
unknown
within­
stage
age
at
entrainment.

Life
stage
(
j)
Egg
Yolk­
sac
larvae
Post
yolksac
larvae
Juvenile
1
Juvenile
2
Age
1
S
j,
1
Egg
0.52114
0.26158
0.00178
0.08717
0.22678
0.69008
0.0000048
Yolk­
sac
larvae
0.41469
0.00178
0.08717
0.22678
0.69008
0.0000146
Post
yolk­
sac
larvae
0.00355
0.08717
0.22678
0.69008
0.0000702
Juvenile
stage1
0.16036
0.22678
0.69008
0.0363669
Juvenile
stage2
0.36971
0.69008
0.3697119
Age
1
0.81663
1.1833738
1.
S*
j
represents
the
stage­
specific
survival
rate
(
S
j)
adjusted
to
account
for
the
fact
that
the
precise
within­
stage
age
of
entrained
fish
is
unknown.
2.
1.18
=
(
0.81663/
0.6901)
=
effective
inflation
factor
applicable
to
fish
>=
age
1
to
offset
effects
of
S*
j
[
see
Section
A5­
3.1
of
Chapter
A5
of
the
Case
Study
Document
(
DCN
4­
0003)
for
further
explanation].
Stratus
Consulting
Memorandum
(
6/
28/
02)

Page
3
SC10077
Table
3.
Weakfish
impingement
losses
at
Salem
NGS
in
1978
[
detail
from
salem.
input.
data.
xls
(
DCN
4­
2051)].

Life
stage
(
j)
Impingement
losses
Egg
0
Yolk­
sac
larvae
0
Post
yolk­
sac
larvae
0
Juvenile
stage
1
6,378,530
Juvenile
stage
2
11,260
Age
1
1,466
Total
6,391,256
Table
4.
Elaboration
of
calculations
to
express
1978
weakfish
losses
to
impingement
at
Salem
as
age
1
equivalents.

Life
stage
(
j)
Number
of
fish
impinged
S
j,
1
Age
1
equivalent
losses
Egg
0
0.00000479
0.0
Yolk­
sac
larvae
0
0.0000146
0.0
Post
yolk­
sac
larvae
0
0.0000702
0.0
Juvenile
stage
1
6,378,530
0.0364
231,967.6
Juvenile
stage
2
11,260
0.370
4,163.0
Age
1
1,466
1.183
1,734.8
Total
6,391,256
237,865.3
matches
Table
B3­
2
of
Case
Study
Document
(
DCN
4­
0003)
matches
Table
B3­
3
of
Case
Study
Document
(
DCN
4­
0003)

2.
At
Salem,
how
is
the
silverside
age
1
equivalent
calculated
for
entrainment?
I
do
not
seem
to
be
able
to
get
this
figure.
I
get
4,886,300,
which
is
some
way
off
the
EPA
figure
in
Table
B4­
3
of
107,867.

Age
1
equivalent
losses
of
silversides
were
calculated
using
the
same
general
procedure
that
is
elaborated
for
age
1
equivalent
losses
of
weakfish
in
the
response
to
Question
#
1,
and
described
in
Chapter
A5
of
Part
A
of
the
Case
Study
Document
(
DCN
4­
0003).

EPA
does
not
understand
the
value
4,886,300
that
the
questioner
cites
for
silverside
losses.
Stratus
Consulting
Memorandum
(
6/
28/
02)

Page
4
SC10077
3.
In
Table
B4­
3,
how
is
the
total
catch
number
of
the
same
table
obtained?
Is
it
possible
to
calculate
this
figure
from
the
information
given
in
the
documents?
For
example,
for
spot
 
where
they
are
completely
in
the
fishery
at
age
1,
why
is
the
number
lost
to
the
fishery
so
much
less
than
the
age
1
equivalent
value?

The
metric
"
Total
Catch
(#)"
presented
in
Table
B4­
3
of
Chapter
B4
of
Part
B
of
the
Case
Study
Document
(
DCN
4­
0003)
is
derived
from
"
Total
Catch
(
lb)"
by
the
relationship:

N
s,
k
=
Y
s,
k
/
E
s,
Equation
1
where:

N
s,
k
=
Total
Catch
(#)
=
Foregone
yield
expressed
as
numbers
of
landed
fish
for
species
s
in
year
k
Y
s,
k
=
Total
Catch
(
lb)
=
Foregone
yield
expressed
as
pounds
of
landed
fish
for
species
s
in
year
k
E
s
=
Average
weight
of
landed
fish
(
lbs/
individual)
for
species
s.

The
values
of
E
s
are
not
reported
explicitly
in
the
case
study
reports.
However,
they
are
provided
implicitly
by
the
simple
relationship
described
in
Equation
1,
above.
Values
of
E
s
were
defined
as
the
expected
weight
of
a
landed
fish
of
species
s,
i.
e.,
as
the
average
weight­
at­
age
of
all
age
classes
statistically
weighted
by
the
relative
contribution
of
each
age
class
to
the
overall
age
composition
of
harvested
fish.
In
the
case
of
spot,
E
s
equals
0.41
lbs/
individual.
The
values
N
s,
k
were
not
used
in
the
benefits
analysis
except
for
valuation
of
foregone
recreational
catch.

An
age
1
equivalent
fish
represents
a
living
age
1
fish.
It
is
calculated
under
the
assumption
of
zero
(
or
negligible)
harvest
prior
to
age
1.
The
number
lost
to
the
fishery
is
considerably
less
than
the
number
of
age
1
equivalents
because
most
harvested
fish
are
older
than
age
1
(
and
therefore
fewer
because
of
ongoing
natural
mortality),
and
because
the
fishery
typically
does
not
capture
every
fish
that
survives
to
harvestable
age.

4.
Is
there
any
information
on
the
age
structure
of
impinged
fish
at
any
of
the
case
study
stations?
I
know
that
the
fish
are
measured
at
Salem
but
the
data
does
not
seem
to
be
in
the
documents.

The
available
information
about
the
age
composition
of
impinged
fish
varies
between
case
studies
because
of
differences
in
study
design
and
reporting
habits
among
the
facilities.
In
most
cases,
detailed
information
about
age
composition
was
not
available.
EPA
assumed
that
impinged
fish
were
age
1
fish
unless
ages
of
fish
less
than
1
were
reported,
in
which
case
age
classes
younger
than
age
1
were
enumerated
as
reported
in
facility
documents.
Stratus
Consulting
Memorandum
(
6/
28/
02)

Page
5
SC10077
All
of
the
available
information
about
age
composition
is
provided
in
the
input
data
files
that
are
available
in
the
docket
(
see
DCN
4­
2051).