Niamaimandi and Zarshenas: Economic valuation of stock enhancement of Fenneropenaeus merguiensis in the Strait of Hormuz 
43 
Table 1 
Weights (g), numbers, and times of release of tagged 
juvenile banana prawns ( Fenneropenaeus merguiensis) 
in estuaries in the Strait of Hormuz along the coast 
of the Persian Gulf in Hormozgan Province, Iran, dur- 
ing June-July 2010. The standard deviation (SD) of the 
mean weight is provided in parentheses. 
Mean weight 
(g) 
Number 
released 
Hour of 
release 
0.98 
519,200 
22-02 
1.10 
494,542 
24-02 
1.00 
433,000 
01-03 
1.40 
1,098,332 
11-02 
1.00 
282,816 
11-02 
0.89 
733,578 
18-02 
1.10 
617,269 
18-01 
1.20 
521,664 
20-03 
Total 1.08(0.1) 
4,700,401 
of this study, capital investment of the hatchery was 
not considered. The total cost was the sum of hatchery 
production cost (Qh) and juvenile production cost (Tp). 
Growth increment (Gw) and growth rate ( Gr ) were 
calculated by using King’s (2007) formulas: 
Gw = Gf — Gi (3) 
Gr = W[ / dt, (4) 
where Gf and Gi = the average weight of released and 
recaptured prawns; 
W[ = the change in weight between times of re- 
lease and recapture; and 
dt = the time (in days) between release and 
recapture. 
In the study area, most of the fishing vessels were 
equipped with electronic geo-positioning systems (GPS), 
which provided accurate locations of recaptures. GPS 
information for the release and recapture location was 
used to estimate days at liberty, movement rate, and 
distance traveled for recaptured prawns. The distance 
between release and recapture locations was calculated 
as a straight line between the 2 locations. 
Results 
Of the 50,000 prawns that were marked and released 
overall, 11 (0.022%) were recaptured. The majority of 
these prawns were reported by local fishermen, and 
a few were observed by employees in local processing 
plants. 
During this study in 2010, more than 4.7 million 
banana prawns, each 1 g in weight, were released in 
the mangrove estuaries in Hormozgan waters. The op- 
eration was carried out in June and July. Table 1 shows 
the numbers of prawns released at different times. The 
total production cost was approximately USD 0.004 g -1 
prawn— or 4,700,000x0.004=USD 18,800. 
On the basis of the comparison of the number of 
prawns released (4.7 million) and the recapture rate 
observed for tagged prawns (0.022%), about 1034 re- 
leased prawns, with a mean weight of about 22.80 kg, 
were estimated to have been in the shrimp catch in 
Hormozgan in 2010. 
The average local market price of prawns in 2010 
was USD 3.440 kg -1 . Therefore, the total market value 
for the estimated number of released prawns in the 
catch in Hormozgan was USD 8670. The ratio of catch 
benefit to expenditures was 77.50:18,800=0.0041. 
The juvenile prawns released in shallow waters (at 
depths of 1-2.5 m) on July 4-11 were recaptured at 
depths of 20-25 m, after reaching maturity, on Nov. 
5-20 (a period of about 18 weeks). Tagged banana 
prawns moved in northwesterly direction from the re- 
lease site at 56°56'E, 26°55'N to the recapture site at 
56°24'E, 27°06'N in Hormozgan waters — a distance of 
46 km (Fig. 2). The estimated rate of linear displace- 
ment for recaptured prawns was 310-330 m days -1 . 
The mean age and weight of the 50,000 tagged 
prawns at release were 8.5 weeks old and 1.08 g (SD 
0.1). The mean age and weight of the 11 recaptured 
prawns were 22 weeks and 22.06 g (SD 4.9). The dif- 
ferences in the weights of prawns between release and 
recapture were 16-26 g, and the differences in growth 
rates were 0.87-1.42 g weeks -1 (Table 2). 
Discussion 
In this study, certain factors, such as the choice of re- 
lease sites, release season, and prawn handling, were 
carefully controlled to reduce the rate of mortality. 
In spite of a strong public awareness program, few 
prawns were recaptured. Success in recognizing indi- 
vidually marked marine organisms in the field requires 
observer training, mark visibility, and mark retention. 
Although previous studies indicated that the fluores- 
cent elastomeric tag is a useful method for marking 
juvenile shrimp and fishes (Neal, 1969; Benton and 
Lightner, 1972; Frederick, 1997), problems with this 
method in our study may have contributed to the low 
recapture rate. For example, growth of tissue adjacent 
to the elastomeric mark reduced visibility of the mark 
in the recaptured prawns. Another contributing factor 
may have been a lack of prior training of observers 
that would have allowed them to identify marks. 
In a study in China, other tagging methods (e.g., 
hanging tag brands, unilaterally extirpating eyestalks, 
and cutting uropods) were used and resulted in es- 
timated recapture rates for juvenile fleshy prawns 
( Fenneropenaeus chinensis) from 0.001% to 1.510%. 
Such low recapture percentages likely were affected 
by tag shedding, death of tagged individuals by me- 
chanical injury, and regeneration of the uropod (Wang 
