Norriss & Jackson; Western yellowfin bream 
catch and CPUE was caused by an increased abundance 
of fish available to fishers generated by recruitment of 
the strong 1999 year class to the fishery. Although 
increased targeting by fishers and/or fishing efficiency 
cannot be totally excluded in this multi-species fishery, 
the strength of the 1999 year class has been a major 
influence. 
The 1995 year class also exhibited relatively strong 
recruitment (Fig 2), confirming a similar observation by 
Hall et ill. (2004) from commercial catch samples from 
1999 and 2000. This suggests that all three samples 
provided consistent and representative age structures of 
the population. The 1995 year class was not associated 
with an increase in catch or CPUE, indicating that such 
an increase requires particularly strong recruitment like 
the 1999 year class. Hall et al. (2004) also found a strong 
1990 year class which we failed to detect, although these 
very old fish may have almost disappeared from the 
population by the time we sampled in 2005. 
Catch-at-age sampling shows that interannual 
recruitment is highly variable, a common feature of 
sparids worldwide (e.g. Azeta et al 1980; Geoghegan & 
Chittenden 1982; Francis 1993; Vigliola et al. 1998; Hamer 
& Jenkins 2004), sometimes affecting catch and CPUE 
(McGlennon et al. 2000). In temperate southern 
Australian estuaries, variability in year class strength for 
the congeneric A. butclieri is associated with rainfall and 
river flow, in turn influencing catch and CPUE (Norriss 
et al. 2002). There was no known rainfall event in arid 
Shark Bay associated with the 1999 A. latus recruitment, 
however. 
Water temperature is strongly correlated with year 
class strength in the sparid Pagrus auratus in New 
Zealand (Francis 1993). Along the West Australian coast 
the warm, southward-flowing Leeuwin Current is a 
major oceanographic feature affecting recruitment of fish 
and invertebrates (Caputi et al 1996), including the 
northern waters of Shark Bay (Joll & Caputi 1995). Sea 
levels, an index of Leeuwin Current strength, at nearby 
Carnarvon indicate no distinctive timing or feature of the 
current that might explain the 1999 A. latus recruitment 
event. Moreover, the penetration of the current into the 
shallow inner gulfs, where the A. latus fishery operates, 
appears minimal based on hydrodynamic modelling 
(Nahas et al. 2003) and the existence of frontal systems 
(transitional regions between mixed and stratified water 
columns) around the entrances of Shark Bay (Nahas etal. 
2005). 
Intertidal mangrove creeks in Shark Bay are an 
important habitat for juvenile A. latus (Hesp 2003), and 
possibly a key to determining year class strength. 
Relative to other years 1999 had a distinct lack of very 
low tides in Carnarvon in the months following 
spawning. No relationship is apparent between tides and 
year class strength among other years, however. Key 
factors determining and possibly predicting year class 
strength for this sparid remain unknown and require 
further research. 
References 
Azeta M, Ikemoto R & Azuma M 1980 Distribution and growth 
of demersal 0-age red sea bream, Pagrus major, in Shijiki 
Bay. Bulletin of the Seikai Regional Fisheries Laboratory 54: 
259-278. 
Caputi N, Fletcher W J, Pearce A & Chubb C F 1996 Effect of the 
Leeuwin Current on the recruitment of fish and invertebrates 
along the Western Australian coast. Marine & Freshwater 
Research 47: 147-155. 
Francesconi K A & Clayton D 1996 Shark Bay World Heritage 
Property. Management Paper for Fish Resources. Fisheries 
Management Paper 91, Department of Fisheries, Western 
Australia. 
Francis M P 1993 Docs water temperature determine year class 
strength in New Zealand snapper (Pagrus auratus, 
Sparidae)? Fisheries Oceanography 2: 65-72. 
Geoghegan P & Chittenden M E 1982 Reproduction, 
movements, and population dynamics of the longspine 
porgy, Stenotomus caprinus. Fisheries Bulletin 80: 523-540. 
Hall N G, Hesp S A & Potter 1 C 2004 A Bayesian approach for 
overcoming inconsistencies in mortality estimates using, as 
an example, data for Acanthopagrus latus. Canadian Journal 
of Fisheries and Aquatic Sciences 61; 1202-1211. 
Hamer P A & Jenkins G P 2004 High levels of spatial and 
temporal recruitment variability in the temperate sparid 
Pagrus auratus. Marine & Freshwater Research 55: 663-673. 
Hesp S A 2003 Biology’ of two species of sparid on the west 
coast of Australia. Thesis for Doctor of Philosophy, Murdoch 
University, W'estern Australia. 
Hesp S A, Potter 1 C & Hall N G 2004 Reproductive biology and 
protandrous hermaphroditism in Acanthopagrus latus. 
Environmental Biology of Fishes 70; 257-272. 
Joll L M & Caputi N 1995 Environmental influences on 
recruitment in the saucer scallop (Amusium balloti) fishery 
of Shark Bay, Western Australia. ICES Marine Science 
Symposium 199: 47-53. 
McGlennon D, Jones G K, Baker J, Jackson W B & Kinloch M A 
2000 Ageing, catch at age and relative year class strength for 
snapper (Pagrus auratus) in northern Spencer Gulf, South 
Australia. Marine & Freshwater Research 51: 669-677. 
Nahas E L, Jackson G, Pattiaratchi C B & Ivey G N 2003 
Hydrodynamic modelling of snapper Pagrus auratus egg 
and larval dispersal in Shark Bay, Western Australia: 
reproductive isolation at a fine spatial scale. Marine Ecology 
Progress Series 265: 213-226. 
Nahas E L, Pattiaratchi C B & Ivey G N 2005 Processes 
controlling the position of frontal systems in Shark Bay, 
Western Australia. Estuarine, Coastal & Shelf Science 65: 
463-474. 
Norriss J V & Jackson G 2006 Shark Bay Beach Seine and Me.sh 
Net Managed Fishery Status Report. In: W J Fletcher & F 
Head (eds) State of the Fisheries Report 2005/06. Department 
of Fisheries, Western Australia, pp. 100-105. 
Norriss J V, Tregonning J E, Lenanton R C J & Sarre G A 2002 
Biological .synopsis of the black bream, Acanthopagrus 
butcher! (Munro) (Teleostei; Sparidae) in Western Australia 
with reference to information from other southern states. 
Fisheries Research Report 93. Department of Fisheries, 
Western Australia. 
Vigliola L, Harmclin-Vivien M L, Biagi F, Galzin R, Garcia- 
Rubies A, Harmelin J G, Jouvenel J Y, Le Direach-Boursier L, 
Maepherson E & Tunesi L 1998 Spatial and temporal patterns 
of settlement among sparid fishes of the genus Diplodus in 
the northwestern Mediterranean. Marine Ecology Progress 
Series 168: 45-56. 
Acknowledgements: We thank the commercial net fishers of Shark Bay, 
John Standring at the Denham Fish Factory, and Kim Gray for coliecting 
and forwarding .samples. Carnarvon sea level data was supplied by the 
West Australian Department for Planning and Infrastructure. 
159 
