A year round investigation in the estuaries of Barguna district revealed that for each Penaeus monodon postlarvae (PL), about 37 larvae of other shrimp species, 12 finfishes and 10 macrozooplankters are destroyed during the process of shrimp seed collection. Although abundance of P. monodon PL was not recorded throughout the year, a significant number of other shrimp spp., fin fishes including macrozooplankters are being damaged by the shrimp seed collectors. This indiscriminate destruction of aquatic organisms during P. monodon PL collection is serious threat to aquatic  biodiversity

Ahmed, S.U.

Haldar, G.C.

Hoq, M.E.

Islam, M.M.

Rahman, S.L.

Aquatic Commons

Bangladesh}. Fish. Res., 1 (1) : 41-46 
Bangladesh Fisheries Research Institute 
A study on damage caused to crustacean and finfish 
larvae during collection of Penaeus monodon (fab.) 
postlarvae in the estuaries of Barguna, Bangladesh 
h 1 * 2 1 S.L. Ra man , M.M. Islam 1 M.E. Hoq 1 C.C. Haldar and S.U. Ahmed 
Brackishwater Station, Bangladesh Fisheries Research Institute 
Khu/na-9280, Bangladesh 
1 FRI, Riverine Station, Chandpur 
2 
FRI, Freshwater Station, Mymensingh 
* Corresponding author 
Abstract 
A year round investigation in the estuaries of Barguna district revealed that for 
each Penaeus monodon postlarvae (PL), about 37 larvae of other shrimp 
species, 12 finfishes and 10 macrozooplankters are destroyed during the 
process of shrimp seed collection. Although abundance of P. monodon PL was 
not recorded throughout the year, a significant number of other shrimp spp., fin 
fishes including macrozooplankters are being damaged by the shrimp seed 
collectors. This indiscriminate destruction of aquatic organisms during P. 
monodon PL collection is serious threat to aquatic biodiversity. 
Key words : P. monodon PL, Finfish larvae, Colossal loss 
Introduction 
Shrimp exports contribute a very positive impact on the national economy of 
Bangladesh. Recent expansion of farming areas and the trend of selective 
stocking of P. monodon postlarvae (PL) by farmers has resulted in tremendous 
demand of seed (PL) of this species. The high demand of P. monodon PL has 
stimulated a large number of people in shrimp seed collection along the coastal 
belt. Shrimp seed are extensively collected by push net and fixed bag nets, and 
the seed collectors transfer their catches to earthen bowls, which are carried to 
the river bank. P. monodon PL locally known as 11 Bagda pona 11 are then sorted 
out and the rest are discarded along the dry shore, result in large wastage of 
both penaeid larvae and other commercially important aquatic organisms. 
Some previous investigations gave some information on zooplankton with 
special reference to penaeid postlarvae (Zafar and Mahmood 1994, Hossain 
1984) in estuaries of this country. The first information on colossal loss to 
zooplankton during shrimp seed collection in the estuarine waters of Chakaria 
S.L. Rahman et a/. 
Sundarban, Satkhira and l<hepupara are given by Mahmood (1990). The present 
year-round study was carried out in two river-estuaries of Barguna with the 
objectives of identification of seasonal and spatial pattern in crustacean and fin 
fish larval distribution, although, the main objective was to assess the quantum 
of damage caused to shell and finfish larvae while collecting P. monodon seed. 
Materials and methods 
Field methods 
Samples were drawn from two major rivers viz. Baleshawr and Bishkhali of 
Barguna coastal district during December'92 through November'93. Three 
stations were selected in each river. 
Sample were drawn at fortnightly intervals. A rectangular drag net made of 
nylon netting (mesh size 1 mm) and bamboo spilt structure(1.6x0.6m) was used 
for sampling. The net was operated in shallow waters of the river against current 
for about 10 minutes. Two samples were collected at day time during low and 
high tides. Immediately after collection samples were preserved in 5% buffered 
formalin solution. Salinity of water was recorded weekly by direct reading 
refractometer. Water temperature was measured weekly by a alcohol 
thermometer. 
Laboratory analysis 
In the laboratory P. monodon PL were identified and separated following 
Muthu (1978) and Motoh and Buri (1980), and other shrimp and fin fishes larvae 
including zooplankters were identified into major taxonomic group following 
Davis (1985), Fischer and Witchead (1974) and George (1969). 
Results and discussion 
Hydrographic conditions 
Average monthly water temperature and salinity values have been shown in 
Fig. 1. Water temperature ranged between 20.4 to 30.8 °C in both the rivers. 
During the period between july and December salinity attained '0' in both rivers. 
This lowest salinity may be due to monsoon effects, during other part of the year 
(January-June) salinity ranged between 1 to 6 ppt with highest in May. 
Abundance of P. monodon PL were probably related yvith presence of salinity, 
during '0' salinity period almost no P. monodon PL was recorded. Average 
salinity was lower than the rivers of Patuakhali and Bagerhat districts (FRI 1996). 
42 
P. monodon PL collection 
Baleshwar River 
30 
25 
20 
15 
10 
5 
o~~r-~~~---.--~--~-=~--+---~~--­
Dec. Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. 
Months 
- Temperature(oC) -I- Salinity (ppt) 
BishkhaH River 
35,----------------------------------------, 
30 
25 
20 
15 
10 
5 
0+-==r--,,--,---.--~----~~--+---r-~---+ 
Dec. !an. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. 
Months 
- Temperalure(oC) -I- Saiinity (ppt) 
Fig. 2. Monthly distribution of water temperature and salinity in two rivers of Barguna 
district during study period. 
Distribution of individual taxa 
Monthly quantitative distribution (individuals/unit effort) of P. monodon 
postlarvae, larvae of other shrimps, finfishes and macrozooplankters in two 
rivers of Barguna district have shown in Table 1. No P. monodon PL was found 
during the months of July to October when there was no salinity in river. On the 
other hand, abundance of other shrimp spp. increased during the months of 
August through January, and the maximum was recorded in October. There was 
a sudden decrease of other shrimps in November, but the finfish larvae 
occurred in abundance during this month. There was no uniform pattern in 
distribution of both finfish larvae and macrozooplankters, their abundance 
fluctuated from one month to another. Finfish larvae and zooplankters were 
more abundant in post monsoon period than other time of the year. 
43 
Table 1. Monthly distribution (Individual/unit effort) 1 of different taxa in the two major rivers of Barguna 
Months Yearly 
Major taxa Dec. jan. Feb. Mar. Apr. May. jun. jul. Aug. Sep. Oct. Nov. Total % 
A. BALESHWAR RIVER 
Penaeus monodon 1 2 3 3 2 2 1 0 0 0 1 1 s6 1.75 
Other shrimp spp. 100 42 27 35 22 14 34 19 37 46 155 35 566 61.99 
Finfish 16 4 4 16 11 9 7 11 5 7 30 80 200 1.91 
Macrozooplankter 9 5 16 20 13 19 12 8 11 7 7 4 131 14.35 
Total number 126 53 50 4 48 44 54 39 3 60 192 120 913 100.00 
B. BISHKHALI RIVER 
Penaeus monodon 1 2 3 2 3 2 1 0 0 0 0 1 15 1.60 
Other shrimp spp. 95 6 36 1 14 21 5 26 35 85 17 0 591 63.21 
Finfish 10 7 8 15 12 9 6 18 13 11 20 37 166 17.76 
Macrozooplankter 8 6 14 19 26 36 9 7 15 1 2 10 163 17.43 
Total number 114 71 61 67 55 68 51 51 63 107 139 88 935 100.00 
1 Operating a drag net (1.6 X 0.6m) for about 10 minutes as a unit effort 
P. monodon PL collection 
Composition and dominant taxa 
P. monodon PL contributed a small fraction to the total catch composition, 
1.75% in Baleshawr and 1.60% in Bishkhali river. Other shrimp spp., finfishes 
and macrozooplankters showed more or less similar pattern in distribution in the 
two rivers. Other shrimp species included P. indicus, Metapenaeus monoceros, 
M. brevicornis, Macrobrachium spp. Finfishes included Lates ca/carifer, Setipina 
phasa, Glossogobius spp., Uza spp. and other macrozooplankters were lsopods, 
Copepod, Acetes sp., Mysids, Alima, and crab larvae etc. Abundance of shrimp 
PL other than P. monodon reflected majority (63.21 %) in Bishkhali river followed 
by Baleshawr river (62%). Finfishes occupied 21.91% and 17.76% in Baleshawr 
and Bishkhali river respectively. Other zooplankton population occupied only 
17.43% in Bishkhali and 14.35% in Baleshawr river. 
Relative abundance and colossal loss 
Due to high demand of P. monodon PL, the number of shrimp fry collectors 
increased to a great extent in the coastal region of this country. All suitable sites 
for shrimp fry collection along the coastal rivers are exploited by them using fine 
meshed nylon nets. This causes a great loss to other aquatic organisms at the 
early stage of their life cycle. The present attempt to quantify the damage as a 
result of such exploitation, revealed that on an average the catch composition 
(%) of P. monodon PL were only 1 .67%, other shrimps 62.60%, finfishes 
19.84% and macrozooplankters 15.89% (Table 2). This observation revealed that 
for collecting single P. monodon PL, 37 other shrimps, 12 finfishes and 10 
macrozooplankters are being destroyed by shrimp fry collectors. Mahmood 
(1990) reported from Chakaria Sundarban, Satkhira and Khepup;:ua estuaries that 
for fishing single P. monodon PL, 14 other shrimp Pls., 21 finfishes and 1631 
zooplanktons were killed. The variations in zooplankton population with the 
present observation might be due to difference in mesh size of the collection 
net. The microzooplankters could not collected for this study due to large mesh 
size (1 mm) of the gear used. 
Table 2. Average catch composition of P. monodon, other shrimp spp., finfishes and 
macrozooplankters from rivers of Barguna 
Major Taxa 
P. monodon 
Other shrimp spp. 
Finfishes 
Macrozoop I an kters 
Total 
Yearly average catch 
(%) 
1.67 
62.60 
19.84 
15.89 
100.00 
Number of other species 
destroyed for each P. 
monodon PL collection 
37 
12 
10 
59 
45 
S.L. Rahman et a/. 
An estimate was made on the P. monodon PL, harvested from rivers of 
Barguna district revealed that about 1.3 billion P. monodon PL were collected 
during the year 1993, resulted damage of large number of other crustaceans 
and finfishes during shrimp fry collection. According to Funegaard (1986), about 
2000 shrimp fry/net/day were collected by the collectors of Satkhira district in 
1982 which were reduced to 200 fry/net/day in 1986- reflected the adverse 
effect of indiscriminate shrimp fry collection in the coastal region of this country. 
Immediate steps should be taken to stop this practice to conserve the aquatic 
biodiversity. 
References 
Davis, C. C., 1985. The Marine and Freshwater Plankton. Michigan State 
University Press. 16 pp. 
Fischer, W. and P. j. P. Witchead (eds.), 1974. FAO species identification sheets 
for fishery purposes. Eastern Indian ocean fishing area 57 and western 
central pacific area 71. Rome, FAO, Pag-Var., Voi.I-IV. 
FRI (Fisheries Research Institute), 1996. Survey and assessment of shrimp fry 
resources in Bangladesh- Annual report. In: Research Progress Report 
(1993-96). FRI, Mymensingh. (unpublished) 
Funegaard, P., 1986. Shrimp seed any to sell? Come to Satkhira, Bangladesh. 
Bay of Bengal News, 22: 2-6. 
George, M.j., 1969. Prawn Fisheries of lndia-11. Systematic taxonomic 
consideration and general distribution. Bull. Cent. Mar. Fish. Res. lnst., 14: 
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Hossain, M. A., 1984. Studies on zooplankton communities of the Mathamuhuri 
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monsoon. M.Sc. dissertation. lnst. of Mar. Sci., University of Chittagong, 
Bangladesh. 38 pp. 
Mahmood, N., 1990. An assessment on the quantum of damage caused to the 
zooplankton while fishing bagda shrimp Penaeus monodon fry in 
Bangladesh estuaries. Proc. Seventh Zoo/. Conf. Bangladesh: pp. 87-94. 
Motoh, H. and P. Buri, 1980. Identification of the postlarvae Penaeus (Crustacea, 
Decapoda, Penaeidae) appearing along shore water. Aquaculture Dept. 
SEAFDEC, Trigbaun, lliolio, Philippines, Res. Rep. 4(2): 15-19. 
Muthu, M. S., 1978. Larval development : Specific identity of penaeid postlarvae 
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Kartha). CMFR/ Bulletin, 28: 86-90. 
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Part-//: Science, 18(1): 39-45. 
(Manuscript received 31 December 1996) 
46 


A study on damage caused to crustacean and finfish larvae during collection of Penaeus monodon (Fab.) postlarvae in the estuaries of Barguna, Bangladesh

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A study on damage caused to crustacean and finfish larvae during collection of Penaeus monodon (Fab.) postlarvae in the estuaries of Barguna, Bangladesh

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