Hyndes et al.: Age and growth estimates of Ptatycephalus speculator 



279 



Figure 2 



Mean marginal increments ± SE for whole 

 and sectioned sagittal otoliths of Platyce- 

 phalus speculator. Note that the marginal 

 increment is given as a relative value, i.e., 

 as a percentage of the distance between the 

 focus and the outer translucent zone when 

 only one zone was present, or as a percent- 

 age of the distance between the outer edges 

 of the two outermost translucent zones when 

 two or more such zones were present. In this 

 Figure and in Figs. 3 and 6, the black bars 

 on the X-axis refer to winter (June-Aug.) 

 and summer (Dec. -Feb.) and the open bars 

 to spring (Sept. -Nov.) and autumn 

 (March-May). 



the same as that of otoliths with 

 1-4 translucent zones (Fig. 2). 

 Mean marginal increments based 

 on all whole otoliths followed 

 similar annual trends, but they 

 were not as pronounced or con- 

 sistent, and the variation about 

 the means was greater (Fig. 2). 



Length-frequency data 



Few fish < 180 mm in length were 

 caught (Fig. 4), reflecting the 

 fact that smaller individuals of 

 this benthic species did not tend 

 to be collected by seine and gill- 

 nets. 



The three fish caught in the 

 middle of spring (October) of 

 1987, which had otoliths with a 

 single translucent zone bounded 

 by a very narrow opaque zone, 

 measured 91-106 mm in length 

 (Fig. 4). This group is assumed to 

 represent the O-i- age-class, i.e., 

 the result of spawning which 

 peaked in early January 1987 

 and can therefore be referred to 

 as the 1987 year-class. The larger 

 fish, which produced modal length-classes at 325-349 

 mm and 400-424 mm in October 1987 (Fig. 4), had 

 otoliths with a narrow opaque zone bounding two and 

 three translucent zones, respectively. The groups with 

 two and three translucent zones therefore represent 

 the 1 + and 2+ age-classes, or the 1986 and 1985 year- 

 classes, respectively. Fish viath otoliths exhibiting one, 

 two, and three translucent zones in December 1987 and 

 February 1988 are designated as representing the 



Whole otoliths 



Sectioned otoliths 



1 translucent 

 zone 



0.4 





 1.2 ■ 

 0.8 ■ 

 0.4 



0"- 

 1.2 



2 translucent 

 zones 



3 translucent 

 zones 



4 translucent 

 zones 



5-12 translucent 

 zones 



Pooled 

 data 



A O D 



1987 



F A J A O D F A 



1988 1989 



AODFAJAODFA 

 1987 1988 1989 



1987, 1986, and 1985 year-classes, which is consistent 

 with their length distributions (Fig. 4). The marked dif- 

 ference between the lengths of the 1987 year-class in 

 October and December 1987 suggests that this year- 

 class underwent remarkable growth between these 

 months. However, the three fish caught in October 

 were taken by beach seine in the shallows and are thus 

 presumed to represent the lower end of the length 

 range of this year-class, whereas those fish of the 



