NOTE Laurenson et al.: Growth curves of two estuarine populations of Cnidoglanis macrocephalus 



883 



1 Translucent Zone 19 



Aug Oct Dec Feb Apr Jun Aug Oct Dec Feb Apr 

 1987 1988 1989 



Figure 1 



The percentage of lapilli of the eel tailed catfish 

 Cnidoglanis macrocephalus from Wilson Inlet pos- 

 sessing a clearly defined peripheral translucent zone 

 in each month. Data are presented separately for 

 otoliths in which there are one to five or more inner 

 translucent zones. Black rectangles on the x-axis 

 represent summer and winter months, white rect- 

 angles the autumn and spring months. 



MHI 



1 Translucent Zone 



2 Translucent Zones 



5 



«e 120 



3 Translucent Zones 



1 



7 3 1 



**\i 



>4 Translucent Zones 



2 1 



Aug Oct Dec Feb Apr Jun Aug Oct Dec Feb Apr 

 1982 1983 1984 



Figure 2 



Mean relative marginal increments for 

 asterisci otoliths of the eel tailed catfish, 

 Cnidoglanis macrocephalus from the Swan 

 Estuary. Recalculated from the data used 

 by Nel et al. (1985). Data are presented 

 separately for otoliths in which there are 

 one to four or more translucent zones. Stan- 

 dard errors are given when sample size was 

 >3. Black rectangles on the x-axis represent 

 summer and winter months, white rect- 

 angles the autumn and spring months. 



remained through the following summer, autumn, and winter months. Although data for otoliths with both 

 four and five or more translucent zones were less abundant, they followed a similar trend (Fig. 1). The mean 

 marginal increment on otoliths with one, two, and three translucent zones from Swan Estuary fell to a mini- 

 mum in the spring and rose progressively during the ensuing summer and early autumn, before levelling off 

 in the late autumn and winter (Fig. 2). While the number of otoliths with four or more translucent zones was 

 small, the trend shown by the marginal increment on these otoliths is similar. 



A cubic polynomial equation, using logarithm (natural) transformed data, provided the best description of 

 the relationship between otolith radius and total fish length in both Wilson Inlet and Swan Estuary, when 

 lapilli and asterisci otoliths were used, respectively (Fig. 3). 



The equations were as follows: 



Wilson Inlet 



Males: 

 Females: 



y = 5.700 + 1.388* 

 y = 5.708 + 1.374* 



0.191a: 2 - 0.315.x- 3 {R 2 = 0.935, P < 0.001, n = 462) 

 0.235.V 2 - 0.317* 3 (R 2 = 0.926, P < 0.001, n = 876) 



