Cappo et at: Causes and consequences of a latitudinal cline in the demography Lut/anus /ohnii 
319 
Table 5 
Parameters of the functions relating gonad weight (grams) to fork length (FL) for John’s Snapper ( Lut - 
janus johnii ) sampled in 3 regions of Australia over the period of February 1989-April 2002. Nonlinear 
least-squares estimation was calculated with the following equation: gonad weight = e (a + b Standard 
errors of parameters are shown in parentheses, and the range in FL (Lp), sample size ( n ), and coefficient 
of multiple determination ( R 2 ) are also given. 
Region; sex 
Lp range (mm) 
n 
a 
b 
R 2 
North Queensland (Male) 
222-860 
67 
-5.24 (0.99) 
0.01 (0.00) 
0.75 
North Queensland (Female) 
173-830 
60 
-2.27 (1.08) 
0.01 (0.00) 
0.57 
North Queensland 
173-860 
127 
-2.98 (0.75) 
0.01 (0.00) 
0.60 
Kimberley 
473-696 
60 
-6.49 (0.69) 
0.02 (0.00) 
0.68 
Cape York 
290-652 
56 
-31.64 (2.19) 
0.06 (0.00) 
0.96 
geon (Robertson et al., 2005a) and there are no indi- 
cations of consistent effects of fishing on longevity or 
adult survivorship (Robertson et al., 2005b). In relation 
to Berrigan and Charnov’s (1994) commentary, it is im- 
portant to note that there was no sign of a negative 
relationship between locality-specific and K in fig. 
5 of Robertson et al. (2005a) for Ocean Surgeon, but 
such a negative relationship was noted for Stoplight 
Parrotfish in fig. 4 of Choat et al. (2003). 
Counter-gradient variation in growth rates has been 
proposed to explain this contradiction of the temper- 
ature-size rule. This counter-gradient variation occurs 
where genetic and environmental influences on pheno- 
types oppose one another to produce metabolic com- 
pensation (Conover et al., 1997). Various physiological 
rates and processes are now known to be elevated to 
counteract the dampening effect of reduced tempera- 
ture and diminished length of the optimal season for 
Table 6 
Comparison of regional summaries of gonad weight at length for John’s Snapper ( Lutjanus joh- 
nii) from our study of a latitudinal cline in the demography of this species in Australia. Likeli- 
hood ratio tests, each with 2 degrees of freedom ( df) were performed for coincidence of curves. 
Tests of differences among slopes ( P) and intercepts (a) were made by using 1-way analysis of 
covariance of gonad weight against log e (age). All tests were conducted over age ranges in fork 
length (FL) present in both levels of the pairwise comparisons. The number of samples in, shown 
in parentheses) and gonad weights is shown for each member of a pair, and the common length 
range in millimetres is also given. P=probability of null hypothesis being true. If the chi-squared 
goodness-of-fit statistic (% 2 ) is large, the null model is a poor fit to the curve. The F statistic 
is the ratio of between-group mean square values to the within-group mean square values for 
slopes and intercepts. Inf=infinity. 
Region; fork length range 
Parameter 
Test statistic 
P 
North Queensland 
Male (66), Female (57); 222-830 mm 
Curves 
X 2 =lnf 
1 
P 
F= 0.08 
0.77 
a 
.F=0.60 
0.44 
Regions 
North Queensland (60), Kimberley (60); 473-696 mm 
Curves 
X 2 =74.17 
<0.00 
P 
F=1.05 
0.31 
a 
F=3.24 
0.07 
North Queensland (89), Cape York (56); 290-652 mm 
Curves 
X 2 =281.74 
<0.00 
P 
F= 2.24 
0.14 
a 
F= 0.55 
0.46 
Kimberley (55), Cape York (22); 473-652 mm 
Curves 
X 2 =157.12 
<0.00 
P 
F=25.74 
<0.00 
a 
F= 28.25 
<0.00 
