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Fishery Bulletin 118(4) 
Table 3 
Results from the Wald chi-square (x) test for significance 
of predictor variables in the 2D generalized additive model 
used to examine overall temporal and spatial patterns in 
catch of adult female blue crab (Callinectes sapidus) col- 
lected during trawl surveys in the northwestern Gulf of 
Mexico between 2000 and 2019. The characters “s()” indi- 
cate that a continuous variable was included as a smooth 
term. Degrees of freedom (df) and estimated degrees of 
freedom (edf) are shown for parametric factor terms and 
smooth terms, respectively. 
Source df or edf "2 P 
Year 19 240.40 <0.0001 
Season 1 21.54 <0.0001 
Year x season 19 174.71 <0.0001 
s(geographic location): 66.16 745.00 <0.0001 
summer 
s(geographic location): fall 69.20 530.10 <0.0001 
Relative importance of offshore and estuarine waters 
During 2006-2018, considering only SSZ 13-21, CPUE 
of adult females from summer surveys in offshore waters 
of the Gulf of Mexico averaged 0.38 individuals/ha 
(SE 0.03), compared with the CPUE values of 0.46 
individuals/ha (SE 0.03) in estuaries of Texas and of 3.92 
individuals/ha (SE 0.17) in estuaries of 
Louisiana. Total available habitat area 
was estimated to be 11,473,937.0 ha 
for the offshore SSZ 13-21 in the 
SEAMAP study area, 578,310.7 ha for 
estuaries of Texas, and 853,436.2 ha 
for estuaries of Louisiana west of the 
Mississippi River. Rough calculations 
made by using CPUE of adult females 
(as a proxy for density) and total habi- 
tat area indicate that estuarine areas 
during June—July supported a min- 
imum abundance of 1,248,675 adult 
female blue crab in 2017 and a maxi- 
mum abundance of 8,631,449 adult 
female blue crab in 2006 and that the 
offshore SEAMAP survey area during 
June—July supported a minimum abun- 
dance of 664,203 adult female blue crab 
in 2013 and a maximum abundance 
of 9,509,020 adult female blue crab in 
2010 (Fig. 5). On average, across the 
13-year period of 2006-2018, the off- 
shore SEAMAP survey area supported 
48.8% of the total spawning stock in the 
northwestern Gulf of Mexico, although 
this percentage ranged from 26.5% in 
2014 to 79.7% in 2017. 
CPUE (individuals/ha) 
Condition and reproductive output of spawning females 
Collection of blue crab for reproductive analyses occurred 
on each state and federal leg of the SEAMAP groundfish 
trawl surveys during summer and fall 2017. In total, 
120 mature female blue crab were collected, with CWs 
ranging from 110 to 209 mm. The vast majority of blue 
crab (109 of 120) were collected during the summer 
survey (30 May—2 July 2017), and the rest of the indi- 
viduals (11 of 120) were caught during the fall survey 
(13 October—8 November 2017). 
Of the 109 mature females collected during summer, 
95 individuals (87.2%) were spawning capable, as evidenced 
by an external egg mass (65 individuals) or mature ova- 
ries (30 individuals). All embryonic developmental stages 
were observed in ovigerous blue crab collected during the 
summer survey, with 56.9% (37 individuals) in the early 
developmental stage, 10.8% (7 individuals) in the middle 
developmental stage, and 32.3% (21 individuals) in the late 
developmental stage. Additionally, 26.2% (17 individuals) 
of the ovigerous females collected during the summer sur- 
vey also possessed developed, full ovaries, indicating the 
capacity to produce at least one additional clutch of eggs 
following the clutch carried at the time of collection. Only 
1 female (0.9%) collected during the summer survey had 
mated recently. 
Of the 11 mature females collected during the fall sur- 
vey, 6 individuals (54.4%) were spawning capable, as evi- 
denced by an external egg mass (5 individuals) or 
developed, full ovaries (1 individual). Of these 5 oviger- 
ous individuals, 4 crab carried eggs in the early 
-® Annual 
~- Summer 
-7- Fall 
Figure 2 
Observed mean annual (solid line) and seasonal (broken lines) catch per unit 
of effort (CPUE) for adult female blue crab (Callinectes sapidus) collected 
during groundfish surveys conducted in the northwestern Gulf of Mexico from 
2000 through 2019 as part of the Southeast Area Monitoring and Assessment 
Program. Values of CPUE were calculated by dividing catch by the area swept 
by the trawl. Error bars indicate standard errors of the mean. 
