CHAPTER - IV (Contd.)

TABLE - 67 : SHOWING MONTHLY PERCENTAGE COMPOSITION OF SHRIMPS PER KG OF PONDHARVEST AT CHAKARIA

TABLE - 68 : SHOWING MONTHLY PERCENTAGE COMPOSITION OF FISHES AND OTHER ORGANISMS (OTHER THAN SHRIMPS) PER KG. OF PONDHARVEST AT CHAKARIA

TABLE - 69 : SHOWING MONTHLY PERCENTAGE COMPOSITION OF SHRIMPS PER KG. OF PONDHARVEST AT SATKHIRA

TABLE - 70 : SHOWING MONTHLY PERCENTAGE COMPOSITION OF FISHES AND OTHER ORGANISMS (OTHER THAN SHRIMPS) PER KG. OF PONDHARVEST AT SATKHIRA.

TABLE - 71 : SHOWING PERCENTAGE COMPOSITION OF THE MALES & FEMALES (SEX-RATIO) OF PENAEID SHRIMPS IN PONDHARVEST (PER KG.) AT CHAKARIA

TABLE - 72 : SHOWING MONTHLY PERCENTAGE COMPOSITION OF THE MALES AND FEMALES (SEX-RATIO) OF PENAEID SHRIMPS IN PONDHARVEST (PER KG) AT SATKHIRA.

TABLE 73 : SHOWING OCCURRENCE OF DIFFERENT SPECIES OF SHRIMPS IN POND HARVEST AT CHAKARIA AND SATKHIRA.

Rarely present + (1< )
Present ++ (1 – 5)
Dominant +++ (5 – 10)
Most abundant ++++ (10> )
Absent -

TABLE 74 : SHOWING OCCURRENCE OF DIFFERENT SPECIES OF FISHES AND OTHER ORGANISMS (OTHER THAN SHRIMPS) IN POND HARVEST AT CHAKARIA AND SATKHIRA.

+ Rarely present (1<)
++ Present (1 – 5)
+++ Dominant (5 – 10)
++++ Most dominant (10>)
- Absent

7.5 DISCUSSION

In the present investigation the average p^H at Chakaria and Satkhira was noted to be 7.4 and 7.3 respectively. Hora and pillay (1962) observed that p^H range of 7.0 – 8.0 is characteristic of good water suitable for fish culture. The p^H value and yearly average content of dissolved oxygen at Chakaria and Satkhira (Table 4 & 5) showed that these areas are productive. The above observation is confirmed from the high concentration of zooplankton which was recorded at Chakaria (monthly average of 418.248/m³) and Satkhira area (monthly average of 309.841/m³). On the otherhand the Khepupara area showed the average p^H value of 6.8 and a poor density of zooplankton (125.760/m³). Thus among the three areas the Chakaria and Satkhira may be treated as productive and good for fish culture. However, a noticeable difference between the abundance of zooplankton in these two areas was observe The possible reason for the difference in the abundance of organism between Chakaria and Satkhira area are explained earlier. Thus the density of organisms (309.841/m³) as noted at Satkhira does not show the exact productivety of the area. The number of zooplankton at Satkhira might have increased to a great extent if some of the sampling stations were chosen in a around the vicinity of mangrove forest as it was done at Chakaria area.

In the present studies a high concentration of shrimp larvae was found at Chakaria (4.328/m³) and Satkhira area (4.22/m³) in the population of plankton. The Khepupara area showed a poor abundance of shrimp larvae (1.085 indv/m³). The salinity content of Chakaria (yearly average of 16.2‰) and Satkhira (yearly average of 13.7‰) was noted to be fairly high which may be treated as good for shrimp production. However, at Satkhira the sampling Station-III was located at Ichamati River where from an extensive collection of shrimp seeds is practised by both Indian and Bangladesh side. Moreover the sampling station-II was located at a channel which is partly fed by the River Ichamati. Thus the number of shrimp larvae at Satkhira was reduced to a great extent by the extensive fishing pressure at Ichamati. The concentration of shrimp larvae at Satkhira as revealed in the present observation does not possibly reflect the exact potentiality of the area in shrimp fishery. To get a clear vision further studies are necessary choosing some sampling stations close to the vicinity of mangrove forest. On the otherhand, a sudden drop in salinity content was noticed during monsoon at Chakaria (9.9 to 1.9‰) which might not be good for shrimp culture. However, further studies are also necessary to this end.

The highest density of finfishes (Juvenile), caught through ‘Behundi’ net, was noted at Khepupara (279.08 indv/kg). The Chakaria area was ranked second (249 indv./kg). The lowest density of the Juvenile finfishes, caught by (Behundi' net was recorded at Satkhira (244.5 indv./kg). Hilsa ilisha was the dominant species at Khepupara (monthly average of 9 indv./kg) where as at Satkhira Harpodon nehereus (monthly average of 111.87 indv./kg) and Mystus qulio (monthly average 11.6 indv./kg) were the dominant fauna among the commercially important fin fishes. Mugil tade, another commercial species showed the highest occurrence at Chakaria. Cynoglossus spp. which have export potentiality were found abundantly at Chakaria and Satkhira.

Lates calcarifer, which feeds on shrimps, occurred from July to December at Chakaria area in the Behundi catch. The species though was not found in ‘Lehundi’ catch at Satkhira and Khepupara yet it is presumed that this fish is available in these waters possibly during July to August.

The highest number of shrimps was recorded in the Behundi fishery at Satkhira area (505.6 indv./kg) and the lowest at Chakaria (172.5 indv./kg). The Khepupara area occupied second position (492.9 indv./kg). The above observation shows the high potentiality of Satkhira area in shrimp fishery.

Of the panaeid shrimps, Metapenaeus monoceros and M. brevicornis were dominant species in all the three areas. Parapenaeopses sculptilis was noted in large number at Satkhira and Khepupara where as this species was found to be absent at Chakaria.

In the present observation a relatively higher concentration of shrimps (with a monthly average of 201.82 indv./kg) was recorded in pondharvest at Satkhira area. The Chakaria area showed a monthly abundance of 168.88 indv./kg. Panaeus monodon, Metapenaeus Monoceros and M. brevicornis were the dominant species at both the areas.

Lates calcarifer was noted in the population from March to December at Chakaria area. An inverse relationship was found between Lates calcarifer and shrimp in pondharvest at Chakaria area. Though Lates calcarifer was not recorded at Satkhira in the present observation it is presumed that the species is also available at Satkhira area. The populations of shrimp are minimised to a great extent by the presence of the fish. However, it is difficult to forecast the exact time when the species (Lates calcarifer) was first appeared at the ponds in these areas. Further observation to this end may be helpful.

Thus inview of the present studies, it is presumed that the Chakaria and Satkhira areas are good for shrimp fishery and the Satkhiraarea may be treated as the most suitable for shrimp cultivation among the three areas studied.

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