Page 208 - PARVEEN, S

the D-value of 0.013, and Belal Uddin and Bhai- were comparatively higher. The mortality of fishes
Bon populations were differentiated from each
other by the D-value of 0.002, which suggests that
the four populations may be fallen into the local
population or race.
567 KHAN, S. (Dept. of Fisheries Management,
Bangladesh Agricultural University, Mymensingh).
Euglenophytes in aquaculture ponds- their ecology
and role in fish production. Bang. J. Fish. Res.,
2005, 9(1), 29-30.
The ecology of euglenophytes and their role in fish
production were studied in 12 small earthen ponds
beside the Faculty of Fisheries, BAU from July to
November 2001. Four experiments each with three
replications were conducted and those were as
follows: pond treated with both poultry droppings
and cowdung (T 1); pond treated with only poultry
droppings (T 2), and pond treated with only poultry
droppings (T 3), while the control (T 4) where no
organic manure was applied. Fishes comprising of
rohu (Labeo rohita), catla (Catla catla), mrigal
(Cirrhinus cirrhosus), silver carp
(Hypophthalmichthys molitrix) and silver barb
(Barbonymus gonionotus) were stocked at the
same stocking density of (10,621 fish/ha) and
species ratio (1:1:1:2:2). The stocked fishes were
fed with a common supplemental diet comprising
of mustard oil cake and rice polish (1:1) at the rate
of 4% of body weight per day. The highest cell
density of euglenophytes was found in the ponds of
T 2, where poultry droppings were applied and was
followed by T 1, where both poultry droppings and
cow dung were applied. Higher temperature,
nitrate-nitrogen, phosphate-phosphorous and acidic
pH were found to be conducive for the bloom of
noxious euglenophytes. The bloom was found to
use up most of the nutrients resulting in reduction
in the growth of beneficial plankters and
planktivorous fishes. The SGR (%/day) of catla,
rohu and mrigal was lower during heavy bloom
period while that of silver carp and silver barb
201
in a pond of T 2 during the bloom period was
possibly due to formation of anoxic situation
(dissolved oxygen level as low as 0.34 mg/1) in the
early mornings through bacterial decomposition of
the settled dead individuals or due to the combined
effect of anoxic situation and toxic metabolite
secretion by the euglenophytes.
568 KHAN, S. (Dept. of Fisheries Management,
Bangladesh Agricultural University, Mymensingh).
Management of euglenophytes in aquaculture ponds
for improvement of fish production. Bang. J. Fish.
Res., 2005, 9(1), 31-32.
Four experiments each with three replications were
conducted in 12 experimental ponds to control the
euglenophytes bloom viz. treatment 1 (T 1),
covering of one third of the water surface by
duckweed (Lemna minor); treatment 2 (T 2),
application of 123.5 kg lime/ha/month; treatment
3 (T 3), use of both duckweed as in T 1 and lime as
in T 2; treatment 4 (T 4) was considered as control
where neither duckweed nor lime was applied.
Fishes comprising of rohu (Labeo rohita), catla
(Catla catla), mrigal (Cirrhinus cirrhosus), silver
carp (Hypophthalmichthys molitrix) and silver
barb (Barbonymus gonionotus) were stocked at
the rate of 1080 fishes/ha with the species ratio of
8:4:6:9:13, respectively. The lowest cell density
of euglenophytes was found in the ponds of T 3
followed by T 2 and T 1. In the ponds of T 3,
euglenophytes bloom did not occur possibly due
to alkaline pH, shade and nutrient absorption by
duckweed. Thin bloom was observed in the
ponds of T 1 where pH was neutral or slightly
alkaline. The grazing on euglenophytes by the
silver carp and silver barb also had some
contribution in controlling the bloom. Growth of
fishes was comparatively higher in the ponds of
T 3 and T 1, which might be due to better water
quality and availability of adequate food while