Journal of the Royal Society of Western Australia, 90; 157-159, 2007 
Notes 
on .... 
A substantial recruitment year 
for the western yellowfin bream 
(Acanthopagrus latus, Sparidae) 
sustains years of high catch 
rates in the inner gulfs of Shark 
Bay, Western Australia 
J V Norriss & G Jackson 
Western Australian Fisheries and Marine Research 
Laboratories, 
PO Box 20, North Beach, W.A., 6920 
0 Jeffrey.Norriss@>fish.wa.gov.au, 
Gary.Jackson@fish.wa.gov.au 
Manuscript received January 2007; accepted June 2007 
Abstract. A large increase in the annual commercial catch 
and catch per unit effort of western yellowfin bream 
{Acanttiopagrus latus) in the inner gulfs of Shark Bay, 
Western Australia, from 2002 to 2005 prompted an 
examination of the age structure of the 2005 catch. 
Sectioned otoliths from 108 fish were assessed to 
determine whether the cause was related to an increased 
abundance following a substantial recruitment. The 1999 
age class was exceptionally strong, contributing 48.1% of 
the sample, and according to published growth rate 
estimates, this cohort would have recruited to the fishery 
at the same time catch rates began to increase. Year class 
strengths of older cohorts were consistent with catch 
sampling carried out in 1999 and 2000, together 
demonstrating highly variable interannual recruitment, a 
trait commonly reported for sparids. Neither Leeuwin 
Current strength nor rainfall was found to be associated 
with year class strength. Factors determining and 
possibly predicting year class strength in this species in 
Shark Bay remain unknown and require further research. 
Keywords: recruitment; western yellowfin bream; 
Acanthopagnis latiis; Shark Bay; otolith; year class 
strength, age 
Introduction 
Shark Bay, Western Australia, is a World Heritage 
Property with a complex marine embayment (Fig. 1) in a 
semi-arid to arid climate (Francesconi & Clayton 1996). 
The commercial fishery for western yellowfin bream 
(Acantliopagrus latus, Sparidae) in the inner gulfs forms 
part of the Shark Bay Beach Seine and Mesh Net 
Managed Fishery (Norriss & Jackson 2006). Commercial 
fishers are legally required to submit catch and effort 
data to the Western Australian Department of Fisheries, 
declaring the weight and species composition of their 
catch each month, and number of days fished (effort). In 
2002, the total annual commercial A. latus catch, and 
catch per unit effort (CPUE), began to increase (Fig. 2). In 
© Royal Society of Western Australia 2007 
2003, 2004 and 2005 the catch and CPUE further 
Increased to about 2.5 times the long-term annual 
average, prompting an investigation into the reasons for 
this increase, which was either due to a change in 
behaviour of fishers related to increased targeting and/or 
fishing efficiency and/or a proliferation in abundance 
following highly successful recruitment to the fishery. 
Growth rates for Shark Bay A. latus estimated by Hall 
et al. (2004) suggest that the year class spawned in 1999 
would have dominated recruitment to the 250 mm 
minimum total legal length for the fishery during 2002, 
the year when catch and CPUE began to increase. We 
therefore tested the hypothesis that the increased catch 
and CPUE was due to a proliferation in abundance 
dominated by the 1999 year class. 
JVIethods 
During 2005 a sample of 108 commercially-caught A. 
latus were collected from the local fish factory at 
Denham, Shark Bay, the only port of landing for the 
product. Catches from multiple fishers on several 
occasions were taken to ensure the sample was 
representative of the A. latus population in the fishery. 
Sagittal otoliths were removed, sectioned and examined 
microscopically under reflected light (Fig. 3). Their 
opaque zones are formed annually (Hall et al. 2004), and 
there is a short, distinct spawning period during late 
winter and early spring (Hesp et al. 2004), enabling 
I _I_I_ 
113°E 114°E 
Figure 1. Map of Shark Bay, Western Australia, where the Shark 
Bay Beach Seine and Mesh Net Managed Fishery occurs 
predominantly in the inner gulfs (Eastern and Western) south of 
latitude 25°30' S. 
157 
