24 
Fishery Bulletin 1 14(1) 
age between seasons, nested within years. A signifi- 
cant result from a MANOVA model would indicate 
that there were differences in the composition of 
length and ages in the larvae and early juveniles of 
Atlantic croaker that were collected. Growth rates 
were tested with an F-test to compare the residu- 
al sums of squares for the pooled Laird-Gompertz 
growth model with those of the Laird-Gompertz 
growth models that were fitted by season and sam- 
pling year (Chen et al., 1992). 
Distributions of lengths and calculated ages that 
were based on readings of otoliths were tested for 
normality with a Shapiro-Wilk’s test. A mixed model 
was applied by using R software (vers. 2.13.0) to look 
at growth rates of individual larvae with respect to 
salinity, temperature, and NWT within the tidal pass: 
y LJ =P 0 + ^Salinity ;j + f3 2 WaterTemp ;j + p 3 NWT. t ^ ^ 
+ P 4 Tide^ + T; + E;j, 
where jqj = the response variable of growth rate for the 
random group i and individual j; 
Po = the intercept term; 
P parameters = the effects for each of the variables 
(i.e. , salinity, water temperature, and 
NWT), with tide being a binary dummy 
variable for each of the tide states (i.e., 
flood or ebb); 
r i = the random effect of sampling month when 
the larvae were collected; and 
e ij = the random error term for the model. 
Results 
Hydrology 
There were no statistical differences in water tempera- 
ture by sampling depth. This result is consistent with 
a seasonally, vertically well-mixed tidal pass, such as 
Bayou Tartellan. Generally, water temperatures fol- 
lowed the normal seasonal trends, in which water was 
warmer during the early fall (i.e., September and Oc- 
tober) and cooler during the winter before rising again 
during March and April. There was a noticeable drop 
in temperature during November 2006, and median 
water temperature remained below 15°C through early 
February 2007. During the winter months, colder tem- 
peratures and greater temperature fluctuations were 
recorded than those recorded during fall or spring 
months. In particular, for the December 2007 sampling 
effort, there was a fluctuation range of 10.2°C during 
the 72-h sampling period. Although water temperature 
also decreased in November 2007, the median water 
temperature did not fall below 17°C during all remain- 
ing sampling efforts, resulting in higher water temper- 
atures during year 2 of sampling. 
No statistically significant differences were found 
between surface or near-bottom salinities, once again 
supporting a seasonally, vertically well-mixed estu- 
ary. In general, 95% of all measured practical salinity 
values fell between 21.5 and 31.4 within a total range 
of 14.5-33.2 and with a mean of 27.32. Median salin- 
ity values dropped by more than 5 between December 
2006 and January 2007. In early February 2007, the 
median value was similar to that of January 2007 but 
ranged from as high as 32 to a low of nearly 20 over 
a 4-d period. Aside from median salinities of approxi- 
mately 28 in late February 2007, the median salinity 
in Bayou Tartellan remained below 25 until early April 
2007. Salinities during late 2007 and early 2008, with 
the exception of early March, showed less variation 
and were generally higher than those of the previous 
sampling year. 
Catches of larval Atlantic croaker 
There were 3118 larval and early juvenile Atlantic 
croaker collected from October 2006 through March 
2007, and 425 larvae were collected from September 
2007 through March 2008. Sampling continued through 
April in both 2007 and 2008; however, no Atlantic 
croaker were collected during that period. Catches 
in November 2006 accounted for 53.5% of the total 
number of Atlantic croaker larvae collected over both 
sampling periods. As in 2006, collections made in No- 
vember 2007 had the greatest number of larvae caught 
in the second sampling period, but a second peak was 
observed in March 2008. 
Table t 
Hatching dates for larval and early juvenile Atlantic 
croaker ( Micropogonias undulatus) collected in Bayou 
Tartellan, Louisiana during 2006-2008. Hatching dates 
are based on back-calculated otolith ages and collection 
dates after application of age-length keys. Percentages 
of the total number of larvae collected in that sampling 
year and cumulative percentages are based on half- 
month intervals. 
Interval 
2006-2007 
2007-2008 
% 
Cumulative 
% 
% 
Cumulative 
% 
08/15-08/31 
0.26 
0.26 
0.00 
0.00 
09/01-09/15 
8.97 
9.23 
4.65 
4.65 
09/16-09/30 
29.74 
38.97 
21.71 
26.36 
10/01-10/15 
32.56 
71.54 
17.83 
44.19 
10/16-10/31 
10.51 
82.05 
18.60 
62.79 
11/01-11/15 
2.05 
84.10 
3.88 
66.67 
11/16-11/30 
4.10 
88.21 
5.43 
72.09 
12/01-12/15 
6.15 
94.36 
1.55 
73.64 
12/16-12/31 
0.26 
94.62 
3.10 
76.74 
01/01-01/15 
1.28 
95.90 
6.98 
83.72 
01/16-01/31 
3.08 
98.97 
10.85 
94.57 
02/01-02/15 
1.03 
100.00 
5.43 
100.00 
02/16-02/28 
0.00 
100.00 
0.00 
100.00 
