THEILACKER: CHANGES IN BODY MEASUREMENTS OF LARVAL NORTHERN ANCHOVY 



4.0 

 3.0 



2.0 - 



1.0 - 



0.1 



0.9 



0.8 

 0.7 



0.6 

 0.5 



-^0.4 



E 



— 0.3 



0.2 



0.1 



3 4 5 6 7 89 10 15 20 



EYE DIAMETER 



J I I I I 



2 3 4 5 6 7 8 910 15 20 



LIVE STANDARD LENGTH (mm) 



Figure 2. — Head length, body depth, and eye diameter as func- 

 tions of standard length in live northern anchovy larvae. Non- 

 linear models for live head length and body depth with standard 

 lengths and linear model for eye diameter with standard length 

 are described in the text; estimated parameters are in Table 1. 

 Dots are means of 10 larvae. Circles represent individual fish. 



obtained by eliminating time it) from two Gom- 

 pertz equations 



y ^ yo exp(Ao [l -exp( -at)]/a) and 

 X = Xoexp(Bo[l~exp(-/30]//3) 



Table L — Estimated parameters for nonlinear and linear mod- 

 els relating live body part measurements (y) with standard 

 length (x I of northern anchovy larvae. 



(Zweifel footnote 3). a corresponds to the natural 

 logarithm of the asymptotic size of 3'; c represents 

 the natural logarithm of the asymptotic size of a: 

 (standard length); and d is the ratio of the decay 

 parameters a and /3 in the individual Gompertz 

 growth curves. The parameter b has no simple 

 biological interpretation except when the decay 

 parameters are equal id = 1); in this case the 

 equation is reduced to a simple allometric growth 

 model. The model was fit to the observed head 

 length and body depth measurements using Mar- 

 quardt's algorithm for fitting nonlinear models 

 (Conway et al. 1970). The equations (Table 1) gave 

 a good fit to the data (Figure 2). The relation be- 

 tween eye diameter and all treatments is discus- 

 sed in the section on Eye Diameter. 



Laboratory Shrinkage 



For northern anchovy larvae preserved in For- 

 malin, the ratio of preserved to preceding live size 

 for standard length (Figure 3), head length, and 

 body depth did not increase with length; i.e., 

 shrinkage did not decrease with age. The ratio 

 averaged 0.92 for standard length after shrinkage 

 in Formalin, and this relation also held for shrink- 

 age in standard length of northern anchovy, jack 

 mackerel, and Pacific barracuda larvae preserved 

 in Bouin's fixative (Table 2). Shrinkage of other 

 body parts differed among species, but the mea- 

 surements were not made on all three species in 



(.50 



0-75 - 



0-50 



2,50 



7.50 125 17.5 22.5 27.5 

 LIVE STANDARD LENGTH (mm) 



Figure 3. — Ratio of subsequent laboratory -preserved standard 

 length to live standard length in northern anchovy preserved in 

 Formalin. Dots are means of two or three larvae. Circles repre- 

 sent individual fish. 



687 



