NOTE Porter et al.: Estimating live standard length of net-caught Theragra chalcogrammci 
693 
Table t 
Shrinkage correction equations used to estimate the live standard length (SL) of net-treated and preserved laboratory-reared wall- 
eye pollock (Theragra chalcogramma ) larvae. Best model and model containing only preserved standard length (PSL) are shown. 
For 95% ethanol, results indicated that there was borderline multicollinearity in the data (see “Results” section). All variables were 
measured in millimeters. Body depth was measured at the anus. Maximum diameter of the sagitta otolith was used. 
95% ethanol (n= 91; SL range: 5.41 to 9.25 mm J ) 
r 2 
MSE 
Live SL = 2.18 + 0.464(PSL) + l.TKbody depth) + 30.53(otolith diameter) 
0.90 
0.073 
Live SL = 0.230 + 1.02(PSL) 
0.82 
0.130 
5% formalin (n=90; SL range: 5.61 to 9.43b 
Live SL = 2.52 + 0.509(PSL) + 3.18(body depth ) 
0.88 
0.073 
Live SL = 1.88 + 0.807(PSL) 
0.81 
0.112 
1 Live standard length of larvae used to formulate regression equations. 
Table 2 
Growth rates of laboratory-reared walleye pollock (Theragra chalcogramma) larvae between the first and last sampling days deter- 
mined by using live standard length (LSL), and standard length corrected for shrinkage (for shrinkage correction equations see 
Table 1). 
957c ethanol (n=61) 
Growth rate (mm/day) 
% Error from LSL 
Live standard length 
0.056 
Standard length corrected with only preseived standard length 
0.048 
14 
Standard length corrected with best model 
0.058 
4 
5% formalin (n= 60) 
Live standard length 
0.050 
Standard length corrected with only preseived standard length 
0.043 
14 
Standard length corrected with best model 
0.045 
10 
For 5% formalin, residuals for the best shrinkage correc- 
tion model did not increase as the amount of shrinkage in- 
creased; therefore the model worked well for all shrinkage 
up to the maximum amount of 27%. 
Growth rates 
Growth rates were calculated with live SL, corrected SL 
from the preserved SL only models, and corrected SL from 
the multivariate models. For each preservative there was 
no significant difference between the growth rate for live 
SL and growth rates calculated with the models (Dun- 
nett’s test, P>0.05). Although the growth rates were not 
significantly different, growth rates calculated from the 
multivariate models were more similar to growth rates 
calculated from live SL (Table 2); therefore additional mor- 
phometric variables improve growth rate estimates over 
using preserved SL alone. 
Discussion 
Fish larvae shrink considerably when they are caught in 
nets and preserved. Shrinkage during collection is most 
likely caused by the plankton net, which can damage the 
larva’s integument (Holliday and Blaxter, 1960). Shrinkage 
also varies between preservatives because of the differing 
ionic strengths of these solutions (Parker, 1963; Hay, 1982; 
Tucker and Chester, 1984). We found that shrinkage of 
walleye pollock larvae was greater in 5% formalin than in 
95%< ethanol — a finding similar to results from other spe- 
cies (Bailey, 1982; Fey, 1999). Often only preserved SL has 
been used to correct for shrinkage in length (Theilacker 
and Porter, 1995; Fox, 1996; Kristoffersen and Gro Vea Sal- 
vanes, 1998), although other measurements, such as oto- 
lith size, have been suggested for use to correct for larval 
fish shrinkage (Leak, 1986; Radtke, 1989,1990). By using 
measurements that are easily made and readily adapted to 
