Otoliths from the benthic individuals were re- 

 moved, mounted on glass microscope slides and 

 ground to a sagittal thin section through the nu- 

 cleus using 600 grit carborundum paper. Incre- 

 ment counts on these ground sections were made 

 at 250-400 X using either bright-field or polar- 

 ized illumination. 



The age of each fish was defined as the number 

 of daily otolith growth increments plus five, the 

 age at first increment formation for this species 

 (Laroche et al. 1982). 



In order to characterize changes in body form 

 during metamorphosis, body depth, snout to 

 anus length, lower jaw length, and the distance 

 of migration of the left eye, of 65 larvae and 0-age 

 benthic specimens were measured to the nearest 

 0.1 mm. 



Results and Discussion 



A plot of the length-at-age of P. vetulus larvae 

 and juveniles taken in both pelagic and benthic 

 collections exhibits a prominent plateau between 

 60 and 120 d of age and between 18 and 22 mm 

 SL (Fig. 1). This plateau shows that there is a 

 period of reduced growth in body length when 

 these fish are undergoing metamorphosis. Plots 

 of body depth and snout to anus length versus 

 standard length both have a well-defined inflec- 

 tion point between 18 and 22 mm SL (Figs. 2, 3). 

 Other morphometric measurement plots (lower 

 jaw length and distance of migration of the 

 left eye) (not shown) also contain an inflection 

 between 18 and 22 mm SL, but less clearly. 

 Changes in body morphology during the growth 

 plateau are illustrated by examining a develop- 

 mental series just prior to metamorphosis (Fig. 

 4A) and comparing individuals of similar sizes 

 within the plateau (Fig. 4B). Changes in body 

 depth are most pronounced, but eye migration 

 and changes in head morphology are also evi- 

 dent. 



The definition of two distinct growth stanzas 

 separated by a plateau conforms to several of the 

 criteria outlined by Ricker (1979). However, as 

 he points out, the timing of the inflection points 

 on the size-at-age plot depends on whether length 

 or weight is measured. We have not measured 

 weight in this study. 



Due to the shape of the length-at-age plot we 

 might expect the length-weight relationship for 

 this species to be complex in form over the inter- 

 val considered here. 



The age of 18-20 mm SL P. vetulus, taken in 



40 



80 120 



Age (days) 



160 



200 



Figure 1.— Standard length versus age of Parophrys vetulus 

 larvae and juveniles caught in plankton net and beam trawl 

 collections. 



o 

 o 



I I I I I I I I I i i i i 



I I I I I I I i i i 



-.Q l I I I I . I - I I I I I I'' 



10 15 20 25 30 



Standard Length (mm) 



Figure 2.— Body depth as a percentage of standard length ver- 

 sus standard length of Parophrys vetulus. 



20 25 



Standard Length (mm) 



35 



Figure 3.— Snout to anus length as a percentage of standard 

 length versus standard length of Parophrys vetulus. 



plankton samples, was 41-74 d (about 1.4-2.4 mo) 

 and those caught by the beam trawl, 49-116 d 

 (about 1.6-3.9 mo; Fig. 1). The exact duration of 

 transformation cannot be determined because of 

 this large range. This is also illustrated by Fig- 

 ure 4B. The range in age of 1 1 pelagic specimens, 

 17.6-20.0 mm SL, whose left eye had begun mi- 

 gration, but was still on the left side of the body, 

 was 49 d. However, if resumption of growth in 

 body length is used to mark the end of metamor- 



151 



