International Journal of Aquaculture, 2015, Vol.5, No.6 1
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3
2
mainly consisted of diatoms, decayed organic matter,
fresh and decomposing algal matter together with sand
and mud (Figure 2). Mullets generally feed by grazing
on submerged rock and plant surface and the function
of inorganic particles in the diet is suggested in the
grinding activity to degrade plant cell walls in the
pyloric portion. (Thomson, 1966; Blaber, 1976). In
addition to inorganic particles, qualitative analysis
revealed 18 other algal food items as C
hlorella
,
Pleurosigma
,
Biddulphia, Peridinium
,
Gyrosigma
,
Coscinodiscus
,
Bacteriastrum, Nitzschia, Closterium
,
Navicula
,
Ceratium
,
Isochrysis
,
Rizosolenia
and
Oscillatoria
and zooplanktons
Tintinnid
,
Sagitta
,
Tabellaria
and copepod, few algae like
Chlorella
,
Oscillatoria
,
Biddulphia
and
Gyrosigma
were the
regularly occurring food organisms throughout the study.
Figure 2 Composition of food items in the stomach of
Mugil
cephalus
of Kayamkulam estuary
Quantitative estimations showed that diatoms are the
most abundant among the total gut contents
contributing to about 58.44% followed by decayed
organic matter (15.02%) and sand and mud (6.69%).
The prevalence of motile benthic diatoms and attached
diatoms in the gut contents of
M.cephalus
, which fed
on the sediment, is common (Oren, 1971; Marais,
1980; Blaber and Whitfield, 1977; Rao and Sivani,
1996). The presence of detritus in the guts of most of
the specimens led to infer that
M.cephalus
swallows
detritus along with diatoms and it forms an
indiscriminate part of the food throughout the year. It is
generally observed that decayed organic matter forms an
important food item of mullets in estuarine environments,
which are associated with thick deposits of silt.
Algal matter consists of a main portion of gut contents
(13.73%) and the common constituent was
Oscillatoria
. These were found almost throughout the
period with the peak occurrence during the post
monsoon months. Zooplankters were found only a
smaller constituent of the food items, with copepods
as the predominant, never forming a major food item.
The percentage composition of each food item in the
diet of fish during the different months (Figure 3) also
indicated marked variations.
Gyrosigma
was the
predominant component during May (33.12%) and
June (29.23%) while it decreased from May to
September. Decayed organic matter formed the major
component during July (25%), October (25.9%),
November (21.06%) and December (20.37%).
Chlorella
forms the frequently appeared food
throughout the year whereas
Oscillatoria
almost
missed in July and September.
Pleurosigma
was
totally absent during July but predominant during
September (36.16%) and decreases towards December.
Feeding on certain food item at different intensities
may be an adaptation to minimize the intraspecific
competition for food observed in mullets (Blay, 1995).
Figure 3 Monthly percentage occurrence of food items from the
stomach of
Mugil cephalus
of Kayamkulam estuary
There is remarkable enhancement in the intensity of
feeding during the post monsoon months and lowering
in the rainy months. The increased feeding intensity in
post monsoon corresponds to the general abundance
of algae in the waters. During rainy season there is
considerable agitation and disturbance to the flora and
a fall in feeding intensity.
Acknowledgements
The author is thankful to Dr. M. E. Kuriakose, Principal,
Kuriakose Gregorios College, Pampady, Kottayam for the
encouragement and support.
References
Al-Marzouqi A., 2012, Food and feeding habits of santer seabream
Cheimerius Nufar
(Val.,1830) from the Arabian sea coast of Oman,
J.
Mar. Biol. Ass. India
, 54(1): 108-112
