642 
Fishery Bulletin 95(4), 1997 
equal to 1, 3, 4 and 5 years, values of are 0.21, 
0.10, 0.07, and 0.05, respectively. 
North Carolina 
Curves of yield-per-recruit on F for Atlantic croaker 
in North Carolina (Fig. 3) showed an opposite trend 
from that shown in Chesapeake Bay. For all levels of 
ForM used in simulations, yield values continuously 
increased from t (; = 1 (177 mm TL) to t c = 5 (434 mm 
TL), indicating that yield could be maximized by in- 
creasing t . However, the shape of yield-per-recruit 
curves differed among different levels of M and t c 
(Fig. 3). For M = 0.20 and 0.25, curves for t c = 1-3 
peaked at low to intermediate levels of F ( F MAX = 
0.20-0.60) and gradually decreased after that, 
whereas for t = 4-5 they increased rapidly in the 
range of F between 0 and 0.35-0.60 and remained 
relatively flat thereafter. For M = 0.30-0.35, the 
peaks in yield at low to intermediate levels of F oc- 
curred only for t = 1-2 and were a lot less pronounced 
than those at lower levels of M. 
For the range of M used in our simulations, esti- 
mates of F cjjr (Fig. 4) indicated that during the pe- 
riod 1979-81 the level of fishing mortality for Atlan- 
tic croaker in North Carolina was well above the lev- 
els of F 0 j and F MAX . At t = 1, estimated losses in 
potential yield-per-recruit from F MAX to F CUR were 
equal to 45%, 35%, 25%, and 4% for M = 0.20, 0.25, 
0.30, and 0.35, respectively. Estimated losses if fish- 
ing mortality were kept at the level of F Q 1 would be 
44%, 22%, 20%, and 14%, respectively. 
Estimated values of t CRITIC and P for Atlantic 
croaker in North Carolina were much higher than 
those estimated for Chesapeake Bay. For M equal to 
0.20, 0.25, 0.30, and 0.35, values of t CRITIC were 7.5, 
M = 0.20 
M = 0.25 
roo 
M = 0 30 
M = 0 35 
500 
f*'0.0 
1 * 0.0 
Figure 3 
Curves of yield-per-recruit on fishing mortality (F) for Atlantic croaker, Micropogonias 
undulatus, in North Carolina (period 1979-81) estimated for mean age-at-first-capture (f c ) 
= 1-5 and natural mortality (M) = 0.20-0.35. 
