630 



Fishery Bulletin 102(4) 



1992 1994 1996 1998 2000 



1994 1996 



Year 



Figure 5 (continued) 



collapse in distribution was evident in 1999 for three of 

 the four regions examined and has been attributed to a 

 combination of fishing mortality, several years of poor 

 recruitment, and two mass mortality events (Murray 

 and Gaughan, 2003). The spawning stock in Albany and 

 Bremer Bay decreased to a point where the annual total 

 allowable catch (TAC) in these fisheries was reduced to 

 zero. The concurrent decreases in B sp _ DEPM and PPS at 

 the south coast regions in 1999, estimated shortly after 

 the progression of an epidemic mass mortality (Gaughan 

 et al., 2000), indicates a positive relationship between 

 Bsp-depm an d PPS. This widespread response provides 

 support for the concept of using the PPS-B SP DEPM rela- 

 tionship to objectively detect, albeit retrospectively, 

 particularly suspect estimates of B sp _ DEPM . 



The marked decline in B sp in 1999 to a very low 

 level at Albany provided sufficient contrast in the time 

 series of data to allow detection of an overestimation of 

 spawning biomass in 1997. Although the difference may 

 not appear to be overly large, the critical factor in this 

 particular case is that the B sp of 18,597 metric tons (t) 



was seen to be healthy, whereas an estimate of 13,660 t 

 would have clearly indicated to the Management Advi- 

 sory Committee a downward trend in Sar-dmops B sp . In 

 turn, such a result would have supported the contention 

 that the stock was in decline, which was expected be- 

 cause of several years of poor recruitment, as evidenced 

 by catch-at-age data (Gaughan et al., 2002). Further- 

 more, in 1998, during the 6 months prior to the mass 

 mortality, the purse-seine fleet in Albany experienced 

 significant difficulties in meeting catch expectations, 

 which also indicated that the stock was at a low level. 

 Although we cannot assess precision of the revised es- 

 timates of B sp , it is likely that the Bsp-OPTIMAI ^ 01 " 1997 

 still overestimates the actual stock size. 



The evidence for a decline in B sl , at Bremer Bay from 

 1994 to 1999, as suggested by the decline in PPS, was 

 supported by trends in catch curves for that period, 

 which showed very low levels of recruitment (Gaughan 

 et al., 2002). The recruitment trends ensured that the 

 annual TACs for Bremer Bay after the mid 1990s did 

 not increase but instead were gradually reduced. The 



