Mud banks and
#Mahesh. V, #Harshavardhan
B. Katare, Vijay S. Hapase @Harshal P. Wankhade, *Snehal
S. Lokhande, *Amrapali M. Gajbhaye, *Nileshwari M.
Warhekar,*Priyanka S. Naik
#College of Fisheries,
Mangalore, Karnataka Veterinary Animal and Fisheries Sciences University,
Bidar, Karnataka, India 575 002.
Fisheries,Veraval,Junagadh Agriculture University,Junagadh,Gujarat,India
*BBKKV, College of
Fisheries, Ratanagiri, Maharashtra, India
The calm, turbid regions
in the coastal waters of Kerala are called the mud banks. The well known mud
banks are formed along the coast of Cochin and Alleppy. The mud banks appear
during the south west monsoon season. The mud gets churned up and this mud is
kept in suspension making the water highly turbid. The muddy waters are free
from surface disturbance their being no wave even during peak monsoon season.
Portion of the beach corresponding to mud banks are free from wave action.
While regions of the adjacent beach experiences severe erosion. The mud banks
acts as a barrier and save the beach being eroded. These mud banks are unique
in nature, which are not reported from anywhere in India. It is periodic
phenomenon taking place between Cannanore and Quilon.
First mention of mud
banks recorded in 1755 by caption cope and described in his book entitled “A
new history of East Indies” later attempts were made to study the Chemistry,
Physics, and Geology of these mud banks. To substantiate the calmness of the
mud bank, there are two schools of thoughts.
1. According to W. King
(1881) attribute to the presence of oil along with mud which causes damping of
2. Keen and Russle
attribute the calming effect to the mud itself- ie mud in suspension increases
viscosity of water and causes damping of waves. This is also reflected as
Generally, the mud colour
is dark green and contains some foraminifera remains. The fineness of mud gives
it an oily feeling consisting of ¾ th clay and ¼ th of silt. The rich Phosphate
the rich content of the mud was observed by Jayaraman and Sheshappa.
Theories regarding the formation of mud
The proposed theories are
1. Underground discharge of mud from mud banks
2. Wave action on bottom mud
3. Upwelling and mud bank formation
This theory was put
forwarded by Ramasastry and Myrland in 1959. According to this, mud bank
formation is associated with upwelling and divergence near the bottom between
20 to 30 meter depth along the coast line. This produces vertical acceleration
resulting in lifting of fine bottom mud.
4.floculation and deflocculation
particles in sea water either be deflocculated depending on whether the
salinity is high or low. In lower salinity conditions particles remain in
suspension. While in higher salinity condition they get flocculated. A
flocculated suspension can be deflocculated by lowering the salinity. This
deflocculation takes place when the salinity falls below 2.5 ppt and
flocculation above 20 ppt. between these two salinity range, the flocculated
mud gets deflocculated and kept in suspension, thus become the responsible
factor for formation of mud banks.
Fish and Fishery
The S.W.Monsoon period
is generally an off season for fisher folk on the west coast of India, who
still use non-mechanised fishing crafts. In this period of general idling, the
calm areas created by the mud banks natural, attract fishermen in large
numbers, from far and wide. These calm areas, varying in extent from about 10km2
to 25km2, provide safe harbourage to the country crafts. Launching and landing
of canoes are very easy in the mud bank areas. Most of the canoes from the
fishing villages of Cochin-Quilon and Cochin-Ponnani congregate respectively at
the mud banks of Alleppy and Nittika, and these places then become centres of
intense fishing activity.
Craft and gear
Dugout and rigged canoes
(Vallom or Vanchi in Malayalam) were the main crafts used in the fishing
operations. Catamarans of Tamilnadu with hook and lines were also seen. The
canoes were mainly of two sizes, a larger one of 9.5 m, manned by 15 persons,
and a smaller one of 6 m, manned by 9 persons. Canoes fitted without board
motors, which had been introduced in 1980, were also in operation. The main
gears of operation were drag nets (Thangu vala) and gill nets (Mathi-chala
vala) Cast nets were also used effectively near the shore in the mud bank area.
This is a rectangular
net made of Cotton or Nylon and is about 50-60 m in length and 15-20 m in
width, with a narrow end measuring about 6-9m. the mesh size is about 20mm. on
sighting a shoal, one person jumps in to the water holding one end of the net
and remains stationary, while the Conoe moves paying out the net to encircle
the shoal. The Canoe on reaching the person, collects the other end also from
him, and the net is hauled. Hauling the ends, a bag like belly in the centre is
formed, where the fishes are collected and removed.
This is a gill net made
of Cotton or Nylon pieces. Each piece, measuring about 2.5 to 3 m long and 4 to
6 m broad, with a mesh of 9 to 25 mm one or two conoes are operated to lay the
net and these Canoes carry 7 to 8 pieces of net is rapidly paid out in a semi
circular fashion, the fishermen making loud noise. Thus driving the shoals
toward the net they are gilled on the nets and removed.
The monsoon fishery was
composed of 50 species of fish and 6 species of prawns. Fishes of the families
Carcharinidae, Clupeidae, Dussumieridae, Dorosomidae, Engraulidae, Tachysuridae,
Ambassidae, Theraponidae, Chirocentridae, Sillaginidae Sciaenidae, Siganidae,
Trichiuridae, Scombromoridae, Stromatidae, Cyanoglossidae and Drepanidae were
encountered in the landings. Of the prawns, Pennaeus indicus, P monodon, P
semisulcatus, Metapenaeus dobsoni, M. monoceros and M affinis represented in the
catch. While the monsoon fishery of the Alleppey mud bank region was dominated
by M dobosoni, Stolephorus sp, Sardinella sp and Leiognathus sp. The mager bulk of the
catch of the northen sector was contributed by Sardinella sp, P indicus and M dobsoni.
The monsoon fishery in
Kerala has a legal protection from the State Government, providing exclusive
operational rights during monsoon to Canoes and Catamarans, especially so in
the vicinity of the mud bank region. Fishing by mechanised vessels is strictly
prohibited at the mud bank and nearly areas. However, indigenous crafts fitted
with outboard motors, introduced in 1980, are allowed to operate in the mud
CMFRI bulletin No. 31,
Mudbanks of Kerala Coast
CMFRI bulletin No. 44, National Symposium on
Research and Development in Marine Fisheries
Seafood — Fish — Crustacea
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