206 
Fishery Bulletin 1 14(2) 
cally, the growth and size of male and female salmon 
covary over time, although at different scales; therefore 
inclusion of models and discussion for both sexes would 
be redundant. Body length (nearest 1.0 mm) measure- 
ments were from the middle of the eye to the posterior 
edge of the hypural plate (MEHP). MEHP measure- 
ments were converted to fork length (FL) by using a 
conversion formula from male Fish Creek chum salmon 
carcasses measured in 1974: (FL=1.21(MEHP)+32.8; 
n= 51; r 2 =0.923; P<0.001). Annual sample sizes for a 
given stock varied from 6 to 86 scales. Years with no 
data included 1995, 1997, and 2001 for Fish Creek and 
1980 for Quilcene River. 
Scale processing and scale measurements 
Scales were processed for age and growth determina- 
tion according to Arnold (1951). The acetate impressions 
were scanned at 24x magnification and stored in JPEG 
file format at 300 dpi. The electronic images were then 
imported into the digitizing software program Image 
Pro 2 with ringed structure macros developed by Media 
Cybernetics (Bethesda, MD). Scales were screened and 
those showing evidence of resorption or regeneration 
were not used in the growth analysis. Each scale was 
measured along a reference line drawn along the lon- 
gest axis of the posterior portion of the scale from the 
center of the focus to the leading edge of the 9 th circu- 
lus (Sa), 21 st circulus (Sb), 1 st annulus (Sc), 2 nd annulus 
(S2), 3 rd annulus (S3), and to the edge of the scale (S4). 
We use the terms annulus and annuli in a restricted 
sense to mean those groups of circuli that represent 
growth from 1 year to the next. 
Growth during specified time periods during the first 
year at sea was estimated from intercirculus spacings 
in the first ocean zone on the scale (Fukuwaka and 
Kaeriyama, 1997). We estimated and assumed that cir- 
culi formed at an approximately constant rate (1 cir- 
culus/7-10 days) on the basis of the total number of 
circuli in the first ocean zone and the length of the 
growing season (time of fry out-migration to the time of 
formation of the first marine annulus on the scale). Fish 
Creek chum salmon fry leave their native streams from 
March through May (Heinl, 2005) and form an average 
of 30 to 35 (mean=32) circuli during the first year at 
sea. Quilcene River chum salmon fry that are released 
into the Quilcene River from the hatchery in early May 
form an average of 33 to 40 circuli (mean=36) during 
the first year at sea. Although the Quilcene River chum 
salmon left freshwater later and had more circuli, this 
southern stock likely endured a longer growing season. 
Sa represented the first 2-3 months (63-90 days) at sea 
(April-May/June for Fish Creek and May-June/July for 
Quilcene River). Sb represented the next 3-4 months 
(84-120 days) at sea (June-August/Sept or July-Sept/ 
Oct for Fish Creek and July-Sept/Oct or Aug-Oct/Nov 
2 Mention of trade names or commercial companies is for iden- 
tification purposes only and does not imply endorsement by 
the National Marine Fisheries Service, NOAA. 
for Quilcene River). Sc represented the remaining time 
through the end of the first growing season, before for- 
mation of the first winter annulus on the scale. 
Growth indice 
For each stock, saltwater growth ( SW ) in body length 
(mm) was back-calculated for the early juvenile (SWla), 
middle juvenile (SWlb), late juvenile ( SWlc ), 1 st imma- 
ture (SW2), 2 nd immature (SW3), and maturing ( SW4 ) 
life stages by using the Fraser-Lee back-calculation 
equation (Lee, 1920). With this method, fish length 
is assumed to be directly proportional to scale radius 
(Dahl, 1909; Kaeriyama, 1998). The equation was given 
as 
L t ,i = 40 + (L t j otal - 40) -(S ti / S t total ), (1) 
where t = year; 
40 = length of the fish at the time of scale forma- 
tion (mm); 
L t i = mean total body length at stage i; 
L t total = mean total body length of the carcass samples; 
S t j = mean radius from the focus to the mark on 
the reference line on the scale; and 
S t tota i = mean total radius of the scale. 
We set the intercept to 40 mm, the length at the time 
of formation of the scale for chum salmon (Kobayashi, 
1961; Helle, 1979). Finally, SW indices were calculated 
as the differences in the back-calculated lengths (L) 
for each life stage: early juvenile ( SWla=La ), middle 
juvenile ( SW lb=Lb-La ), late juvenile ( SWlc=Lc-Lb ), 
1 st immature year (SW2=L2-Lc), 2 nd immature year 
( SW3=L3-L2 ), and maturing ( SW4=L4-L3 ). 
Salmon abundance indices 
Chum and pink salmon abundance indices for early 
juvenile (SWla), middle juvenile (SWlb), late juvenile 
(SWlc), 1 st immature (SW2), 2 nd immature (SW3), and 
maturing (SW4) stages were back-calculated from the 
numbers of pink and chum salmon returns (harvest 
and escapement) of North America by management re- 
gion, time series of age composition of chum salmon, 
and marine mortality schedules for pink and chum 
salmon. 
The pink and chum salmon abundance indices N for 
year t were estimated with the following equation: 
where p 
a 
R 
US 
Pa,t+a ^ a,t+a 
ns„ 
( 2 ) 
the proportion of chum salmon of each age 
class for samples taken in-river; 
age class; 
returns (catch and escapement); and 
the product of daily survival rates from the 
middle of the life stage to the end of life. 
Abundance indices were based on estimates of re- 
turns (harvest and escapement) of pink and chum 
salmon from Ruggerone et al. (2010). For each life 
