Journal of the Royal Society of Western Australia, 90(3), September 2007 
60 
50 
40 
30 
20 
10 
0 
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Li. 
Year 
Figure 2. Total annual catch (solid line) and catch per unit effort (dashed line) for Shark Bay A. latus each calendar year (source: CAES, 
Dept. Fisheries, WA), and the frequency of individuals in each year class (bars) from a commercially-caught sample (n=108) collected 
in 2005. 
accurate aging of individuals. We could thus allocate the 
year of birth to each fish and assess the relative 
abundance of each year class in the catch sample. 
Results and Discussion 
A very strong 1999 year class was observed, 
comprising 52 (48.1%) of the 108 fish that we sampled 
(Fig. 2). Based on age and growth parameters estimated 
by Flail et al. (2004), the mean total length of the 1999 
year class as at 1 January 2002 was 215 mm (95% c.i. 208 
to 221), and at 31 December 2002 was 271 mm (95% c.i. 
261 to 279). With a minimum legal length of 250 mm, the 
1999 year class would have recruited to the fishery 
during 2002, consistent with the limited increase in catch 
and CPUE that year. The elevated catch and CPUE in 
2003 and 2004 was consistent with full recruitment of 
this highly abundant year class to the fishery in those 
years. The dominance of the 1999 year class in our 
sample, together with the timing of the increased catch 
and CPUE, constitutes strong evidence that the high 
Figure 3. Cross section of a Shark Bay A. latus sagittal otolith from the 1999 year class, caught in 2005. Opaque zones (arrowed) are 
formed annually. Reflected light; scale bar = 1 mm. 
158 
