320 
Fishery Bulletin 111(4) 
20 - 
A.vir 
S.nem 
S.nem 
+ L.seb 
.c 1C 
CT) 3 
'd> 
g 
Q> 
O 
10 
L.arg + 
L.seb 
L.arg 
A.vir ,, 
+ S.nem 
L.seb + + L.boh 
L.boh+ + S.nem 
Avir L + mal L.mal® 
l'+ +L.seb o 
A.vir 
L.boji 
L.boh 
L.mal 
o 
L. johnii 
L. johnii 
L. johnii 97 cm 
} 
Cairns 
L.arg + 
L.arg 
L.mal 
o L. johnii — Darwin 
• L. johnii 71 cm Andaman Sea; 
Druzhinin & Hlaing (1972) 
~1~ 
20 ° 
-30° 
- 20 ° 
- 10 ° 
— r 
10 ° 
30° 
Latitude 
Figure 6 
Records of maximum weight of John’s Snapper (. Lutjanus johnii ) and 6 other large lutjanids landed 
until 2011, shown by latitude. The data (whole weight in kilograms) for each species was provided 
by the following sources: the International Game Fishing Association, Australian National Sportfish- 
ing Association, Australian Angler’s Association, and Australian Underwater Federation. The cluster 
of data for John’s Snapper is bracketed for comparison with the data from Darwin and the largest 
weight reported in the scientific literature, by Druzhinin and Hlaing (1972) (bottom right). The other 
6 lutjanids were Mangrove Jack (L. argentimaculatus : L.arg), Twospot Snapper (L. bohar ; L.boh), Mala- 
bar Snapper (L. malabaricus: L.mal), Emperor Snapper (L. sebae: L.seb), Chinaman Fish ( Symphorus 
nematophorus: S.nem), and Green Jobfish (Aprion virescens : A.vir). 
feeding and growth at increasing distance from the 
equator (see Conover et al., 2009, for review). In fact, 
the crisper clarity of opaque and translucent zones in 
otoliths of tropical fishes from latitudes where water 
temperatures are 5-10° Celsius cooler may be a physi- 
ological product of this counter-gradient variation in 
growth (see photomicrographs in Choat et al., 2003, 
2009; Marriott and Mapstone, 2006; Robertson et al., 
2005a). 
Portner and Knust (2007) proposed a “thermal 
limitation hypothesis” that natural selection favors 
individuals that maximize growth and energy effi- 
ciency at the expense of ranges of thermal tolerance 
(see also Portner et al., 2008). The underlying con- 
cept of oxygen- and capacity-limited thermal toler- 
ance (OCLT) implies that oxygen supply to tissues 
is optimal between lower and upper temperature 
limits. Between these limits (termed pejus tempera- 
tures), oxygen supply also can be increased to exceed 
maintenance demand and fuel aerobic metabolism for 
the performance of growth, foraging, migration, and 
reproduction. 
These “performances” support the fitness of species, 
and the excess in oxygen availability that supports 
them is reflected in a species-specific aerobic scope. 
The aerobic scope is the difference between the low- 
est and highest rates of aerobic respiration, with an 
optimum close to the upper pejus temperature. Beyond 
upper pejus limits, oxygen supply decreases, mainte- 
nance demand rises, and aerobic scope begins to de- 
crease (for review, see Portner 2012). At suboptimal 
high temperatures, fish cannot consume enough food to 
meet increasing metabolic needs because aerobic scope 
is insufficient to satisfy the increase in oxygen demand 
from exercise and digestion (Portner and Peck, 2010). 
Populations of Atlantic Cod ( Gadus morhua) also 
follow James’s rule in the Atlantic, where the growth, 
spawning, and recruitment of this species are well 
