130 Fishery Bulletin 120(2) 
Table 1 
Catch per unit of effort (CPUE), mean abundance, carapace length, and weight of flathead lobsters (Thenus orien- 
talis) collected during trawl surveys conducted between 2013 and 2016 in waters of Saudi Arabia in the Arabian 
Gulf. A range of carapace lengths is not given for 2015 because only 1 individual was measured. Standard devia- 
tions (SDs) are given in parentheses. 
Year 2013 
Total no. of stations 88 
No. of stations with lobsters 14 
Mean lobster abundance (individuals/station) 0.278 (0.687) 0.454 (0.904) 
CPUE (kg/h) of stations with lobsters 0.4384 
CPUE (kg/h) of all stations 0.067 
Mean carapace length (mm) 90 (22) 
Carapace length (mm) range 27-134 50-107 
Mean total weight (g) 149 (78) 105 (74) 
Total weight (g) range 3-329 24-250 
Los 
o Observed proportion 
— Fitted curve 
Lso=59.5 (SE 0.6 mm) 
Los=64.6 (SE 1.5 mm) 
Maturaty proportion 
Lso=57.8 (SE 1.1 mm) 
T 
60 70 
Carapace length (mm) 
Figure 2 
Maturity curves for (A) female and (B) male flathead lobsters (Thenus orientalis) 
collected between 2013 and 2016 in waters of Saudi Arabia in the Arabian Gulf. 
Open circles along the fitted curve indicate observed proportions. The black circle 
and square indicate the carapace lengths at 50% maturity (L5)) and 95% matu- 
rity (Lo;), respectively. Error bars indicate the standard errors of these lengths. 
2015 2016 
40 
11 
0.026 (0.460) 0.590 (0.946) 
0.426 0.567 
0.117 0.339 
95 64 (9) 
- 22-86 
206 (33) 101 (180) 
46-243 97-318 
76,000 eggs (Suppl. Table 2) (online only). 
The fertilization rate was very high, above 
97% in all the lobsters. 
Age and growth 
Out of the 7 hypotheses tested, only 3 had 
successful numerical convergence under 
the multinomial likelihood model for the 
data. Those models are the ones with 
2, 3, and 5 age cohorts. Of these 3 mod- 
els, the best model is clearly the model 
with 2 cohorts, according to AIC values: 
—2182.1 for the 2-cohort model, —2174.4 
for the 3-cohort model, and —2157.5 for 
the 5-cohort model. The model with the 
best fit to the length—frequency data is 
shown in Figure 3. The presence of only 
2 cohorts indicates that this species has 
a very short lifespan and rapid growth. 
Estimated parameters of the best-fit 
normal mixture distribution model are 
shown in Supplementary Table 3 (online 
only). As can be seen in Figure 3, very 
few individuals belonging to the young- 
est cohort were observed. Nevertheless, 
all the parameters of the model could be 
estimated with satisfactory statistical 
precision, as evident from the low SEs. 
We were able to use the marginal likeli- 
hood model to estimate the parameters 
of the von Bertalanffy growth function 
in spite of the low number of cohorts 
estimated for the model underlying the 
length—frequency data (Suppl. Table 4) 
(online only). The growth was very rapid 
(with a high K of 0.846 year‘). Given 
these results, life history theory predicts 
that M must be very high (Table 2). 
