45
Indian J. Fish., 58(3) : 45-50, 2011
Food and feeding habits of deepsea pandalid prawns Heterocarpus
gibbosus, Bate 1888 and Heterocarpus woodmasoni, Alcock off Kerala,
south India
S. R. RADHIKA RAJASREE AND B. MADHUSOODANA KURUP*
Centre for Ocean Research, NIOT-SU Research Centre, Sathyabama University
Jeppiaar Nagar, Rajiv Gandhi Road, Chennai - 600 119, Tamil Nadu, India
*Kerala University of Fisheries and Ocean Studies, Panangad P. O., Kochi - 682 506, Kerala, India
e-mail: radhiin@gmail.com
ABSTRACT
Food and feeding habits of two deepsea prawns Heterocarpus gibbosus and Heterocarpus woodmasoni were studied from
the commercial deepsea prawn landings off Kerala coast (south India). The diet of both the species were examined giving
emphasis to variations with regard to months, size groups, sex and maturity stages. Stomach conditions in various maturity
stages, length groups and gastrosomatic index were also studied. The diet of both the species were found similar showing
presence of euphausids, foraminiferans, sponges and detritus. In both the species, highest numbers of full stomachs were
observed in orange-berried females, and spent males, which may be due to their voracious feeding after spawning while
highest number of empty stomachs was observed in head roes of females and maturing males. Variations in the gastrosomatic
index indicated strong correlation between feeding intensity and breeding periods of both the species.
Keywords: Deepsea prawns, Feeding habits, Heterocarpus gibbosus, Heterocarpus woodmasoni, Kerala coast, south India.
Introduction
Prawns form one of the most economically important
constituents in the marine fish landings in India. Kerala is
a fertile strip of land lying along the south-west coast of
India, which forms, less than 10% of the entire Indian
coastline. This state occupies the foremost position in
marine fish production, accounting for about 29% of the
total all India landings (Rajasree, 2005). With the decrease
in traditionally exploited prawn stocks in shallow coastal
waters, prawns in deeper water layers increasingly attracted
economic interest. Targeted fishery for deepsea prawns off
Kerala began for the first time in 1999. However, the rapid
developments of fisheries as well as the considerable
vulnerability to overfishing often lead to a fast decrease in
deep sea prawn stocks off Kerala (Rajasree, 2004). As food
being the major factor regulating the abundance, growth
and movement of animals, any information in this regard
will add to the existing knowledge needed for better
management of the prawn stock.
Some of the important works on the food and feeding
habits of deepsea prawns are those of Turpaeva (1948,
1953), Allen (1959), Butler (1964), Berenboim (1981,
1992) and Weinberg (1980) on the pandalid prawn
Pandalus borealis and those of Mistakidis (1957), Allen
(1963) and Cartes (1993) on the feeding habits of the
deepsea prawns of the western Mediterranean slope. In
the Indian Ocean, only very little is known on the food and
feeding habits of the deepsea prawns, the pioneer study
being the study conducted by Kurian (1965) on the gut
contents of Penaeopsis jerryi in comparison with the
feeding habits of littoral penaeids. Suseelan (1985)
conducted a preliminary study on the gut contents of
deepsea prawns collected during the exploratory surveys
off south-west coast of India, however, information on their
food preference pertaining to season, sex, maturity stage
and size class are still lacking. Therefore, the present study
was aimed to unravel the seasonal variations, if any, in
sex-wise, maturity stage-wise, size group-wise food
preference and stomach conditions of males and females
of H. gibbosus and H. woodmasoni off Kerala coast.
Materials and methods
Samples of H. gibbosus and H. woodmasoni were
collected at weekly intervals from the landings of
commercial deepsea trawls fishing at depths between
300 – 500 m off Kerala coast between September 2000
and August 2002. The specimens collected from Cochin,
Munambam and Sakthikulangara harbours of Kerala were
pooled for gut content analyses. The specimens obtained
46
S. R. Radhika Rajasree and B. Madhusoodana Kurup
from exploratory surveys conducted by FORV Sagar
Sampada along Kerala coast were also utilized for the
studies. In the laboratory, the specimens so collected were
washed, segregated sex-wise and maturity stage-wise and
preserved in 5% formalin. Each prawn was measured for
its total length (TL) and weight (TW) to the nearest mm
and g respectively. After cutting open the carapace wall,
the stomach was dissected out, weighed and stomach
fullness was recorded. The intensity of feeding was
determined by observing the degree of distension of the
stomach due to the quantity of food inside the anterior and
posterior chambers of the proventriculus and this is further
expressed by computing the gastrosomatic index, as the
percentage weight of stomach to the total body weight. The
condition of feeding was expressed as full, 3/4 full, 1/2 full,
¼ full, trace and empty respectively (Pillay, 1952).
A preliminary qualitative analysis of the gut contents
showed that H. gibbosus and H. woodmasoni are carnivores
and detritus feeders and therefore the index of
preponderance method (Natarajan and Jhingran, 1961)
suitable for carnivorous animals was adopted in this study.
Food items of prawns were identified up to generic level
wherever possible, counted and measured volumetrically.
All identifiable and partially digested food remains were
grouped under semi-digested matter. A total of
407 specimens of H. woodmasoni and 596 specimens of
H. gibbosus were used in the present study. Food analysis
was done in relation to months, sexes, maturity stages and
size groups. The prawns were grouped with a class interval
of 10 mm. For maturity stage-wise analysis, three stages in
males and seven stages in females were employed following
Ceccaldi (1966) and Company and Sardá (1997).
Results
Euphausids appeared as the most predominant among
the food items and could be easily identified by the presence
of appendages, broken bright orange coloured shells and
antennae. In H. gibbosus, they formed 40% of the diet
whereas it was 28% in H. woodmasoni. Detritus formed
16% and 14% to the diets of H. gibbosus and
H. woodmasoni respectively, whereas foraminifera
constituted 13% and 23% each to the diets of H. gibbosus
and H. woodmasoni. Among the foraminifers encountered
from the stomachs, Globigerina species showed its
predominance. In most cases, this was represented as whole
organisms. This was followed by Lagena vulgaris,
Proteonina fusiformes, Entosolenia marginata, Rotalina
mammalia, Redobolivina mexicana while Cristellaria
calcar was found only very occasionally in the diet.
Echinoderms and sponge spicules were present as spicules
of glass sponges and skeletal rests of echinoderms. Fish
scales belonging to species of the family Gadidae were also
found in a number of guts of H. gibbosus (4%) and
H. woodmasoni (5%). Other crustaceans comprising of
mostly amphipods and rarely isopods were encountered in
the stomach of H. gibbosus in significant quantities (11%).
On the contrary, in H. woodmasoni, it was not regularly
represented and if present, was only in traces (3%).
Polychaetes consisting of mostly Paramphinome spp. and
aphrodites were rarely encountered from the stomach of
H. woodmasoni (0.5%). Molluscan shells were present in
the stomachs of both the species in quite negligible
quantities. Among them, thecostomata (Cavolina
trispinosa) and gastropoda (Gapulus ungaricus) were the
dominant items. Crushed unidentified items were also often
encountered.
Preference to food items
Monthly variations in the Index of preponderance of
various food items encountered from the guts of males and
females of H. gibbosus showed euphausids as the most
preferred food during most of the months. Detritus turned
out to be the major food items during November in females
and during September in males. Foraminifers were found
aplenty in the female diet during September, May, January
and August. Other crustaceans were present as an important
diet during February and April in females and during
January in males. Monthly variations in the diet preference
of H. woodmasoni showed the predominance of euphausids
in some of the months in the gut contents of females
(September, January, February, March, April, August and
March) whereas foraminifers showed preponderance in
October, December, January, July, January and February.
In males, euphausids and foraminifers were found equally
in most of the months. Detritus was found in significant
quantities during September, November and February in
females but found in less quantity in males. Echinoderms
showed regular occurrence during most of the months in
both the sexes especially during May.
In H. gibbosus, immature females preferred detritus
as the major component (50%), however, with the
progression of maturity, the presence of euphausids was
regular (Fig. 1). In males, the euphausids and detritus
showed regular occurrence at all the maturity stages
(Fig. 2). The presence of foraminifera was encountered only
in maturing males while sand, molluscs and fish remains
were preferred by maturing and spent males.
In females of H. woodmasoni, the maturity stages viz.,
immature, maturing, head roes and spent showed a strong
preference towards euphausids while in other maturity
stages detritus also showed equal preference (Fig. 3). The
foraminifera were found in relatively higher quantities in
immature, maturing and spent females whereas the diet of
orange berries mostly comprised of glass sponges
(33.33%). Copepods and fish remnants were observed in
47
Food and feeding habits of deepsea prawns
Fig. 1. Index of preponderance of various food items in different
maturity stages of female H. gibbosus
Fig. 4. Index of preponderance of various food items in different
maturity stages of male H. woodmasoni
(53.3%) and sponge spicules (66.7%). Euphausids, detritus
and foraminifers were the most favored food items in
females of H. gibbosus in 70-79 mm length group. From
80 mm onwards females of H. gibbosus fed on sponge
spicules, echinoderms and molluscs. Euphausids were the
most preferred food items in males of H. gibbosus of
60-139 mm length group.
Stomach conditions
Fig. 2. Index of preponderance of various food items in different
maturity stages of male H. gibbosus
Fig. 3. Index of preponderance of various food items in different
maturity stages of female H. woodmasoni
Percentage occurrence of various stomach conditions
in different maturity stages of H. woodmasoni showed that
in females, the occurrence of empty stomachs were high in
head roes (20%) where as high percentage of ‘¾ full’
stomachs was observed in orange (75%) and grey berries
(60%) due to the voracious feeding, while ‘full’ stomachs
could be discernible only in black berries (20%) (Fig. 5).
Among male maturity stages of H. woodmasoni, highest
percentage of ‘¾ full’ stomachs were observed in spent
animals (Fig. 6). The presence of ‘empty’ and ‘1/4th’
stomach conditions were predominant in females of
different maturity stages of H. gibbosus viz., immature
females (50%) and head roes (52%) whereas higher
numbers of ‘full’ stomachs were noticed in spent females
(21%) as well as in orange berries (19%). In orange, black
and grey berries, high occurrence of ‘½ full’ stomach was
appreciable quantities in the diets of maturing females
(10.19%) and black berries (34.62%). Euphausids and
detritus dominated the diets of immature males (50%)
whereas mature males showed preference towards
foraminifera, detritus and echinoderms (Fig. 4).
Results of size-wise index of preponderance showed
that in females of H. woodmasoni, besides euphausids,
foraminifera, detritus, echinoderms, fish remains, molluscs
and semi-digested matter showed regular occurrence up to
80-89 mm length groups. Small males of H. woodmasoni
preferred detritus and euphausids as the major food items
and with growth, the preference got shifted to detritus
Fig. 5. Variations of stomach condition in female maturity stages
of H. woodmasoni
S. R. Radhika Rajasree and B. Madhusoodana Kurup
48
Active feeding was noticed in 130-139 mm and 140-149 mm
length groups, as manifested by the occurrence of ‘¾ full’
and ‘½ full’ stomachs in these prawns. Incidence of empty
stomachs was less in 60-69 mm and 70-79 mm length
groups in males and females of H. gibbosus. In male
H. gibbosus, the number of full stomachs was invariably
high from 120-129 mm to 150-159 mm, showing highest
percentage in 140-149 mm (50%) length group.
Gastrosomatic index (GSI)
Fig. 6. Variations of stomach condition in male maturity stages
of H. woodmasoni
GSI
observed which would manifest their voracious feeding
habits after the gonadal maturation process (Fig. 7). In males
of H. gibbosus, high percentage of ‘full’ stomachs was
observed in spent males (17%) in contrast to the high
percentage of ‘empty’ stomachs seen in mature males
(33%) (Fig. 8).
Variations in the gastrosomatic index observed in
males and females of H. woodmasoni commensurating with
ovarian maturation process are depicted in Fig. 9 and 10.
The feeding intensity was high in immature females (1.59),
while it was low in head roes (1.00) Among the three
maturity stages of males of H. woodmasoni, the lowest GSI
values were recorded in immature males (1.20) in contrast
to the high GSI values observed in spent males (3.5). Among
various maturity stages of H. gibbosus, the highest GSI
values were observed in immature and spent specimens of
both females and males while it was lowest in matured
males and head roe females.
4
3.5
3
2.5
2
1.5
1
0.5
0
H. woodmasoni
H. igibbosus
Immature
Headroe
Grey berry
Spent
Maturity stages
Fig. 7. Variations of stomach condition in female maturity stages
of H. gibbosus
Fig. 9. Variation of gastrosomatic index in female maturity stages
of H. woodmasoni and H. gibbosus
5
GSI
4
3
H. woodmasoni
2
H. igibbosus
1
0
Immature
Maturing
Spent
Maturity stages
Fig. 10.Variation of gastrosomatic index in male maturity stages
of H. woodmasoni and H. gibbosus
Discussion
Fig. 8. Variations of stomach condition in male maturity stages
of H. gibbosus
In males of H. woodmasoni, empty stomachs were
noticed in the length groups 80-89 mm, 90-99 mm,
110-119 mm and 120-129 mm while in female
H. woodmasoni, the empty stomachs were more in
80-89 mm, 90-99 mm and 100-109 mm length groups.
The results of stomach content analysis have shown
that the food of pandalid shrimp H. woodmasoni consisted
of two major groups viz., euphausids and foraminifera
whereas H. gibbosus feeds mainly on euphausids.
Belogrudov (1973) stated that the most preferable food
components of pandalids were crustaceans whereas
polychaetes and molluscs formed the least preferred food
items. The presence of detritus, euphausids and mixture of
49
Food and feeding habits of deepsea prawns
bottom and planktonic organisms in the food of
H. woodmasoni and H. gibbosus suggests their greater
inclination for bottom feeding habits. Similar observations
have been reported by a number of workers in other
pandalids. Turpaeva (1948, 1953) reported dominance of
flake like detritus mainly composed of fragments of
crustacean chitin, foraminifera, polychaetes and planktonic
copepods in the gut contents of P. borealis from Barents
Sea.
Though there exists inter-specific dietary overlap
between two species, H. woodmasoni exhibits highly diverse
preference for diets. On the contrary, H. gibbosus has a
restricted dietary preference as the number of taxa observed
in their diet is lesser than that of H. woodmasoni. Though
H. woodmasoni and H. gibbosus exhibit nektobenthic
behaviour, the depths of inhabitance of both the species differ
significantly and this may be attributed to the variation in
the dietary preference. H. woodmasoni inhabits
comparatively shallower depth zones in the range 200 and
300 m while the distribution of H. gibbosus has been
recorded from 300 to 600 m (Suseelan, 1985). As a result of
inhabitance in deeper waters and less productive zones, the
animals exhibit scavenging behaviour and become more
detritophagus (Mary and Ioannis, 1999). The diet of
H. gibbosus is predominated by high concentration of
euphausids, detritus, other crustacean carcasses and semidigested matter. Sporadic presence of carapace remnants and
chewed muscle tissue of pandalid shrimps indicate its
cannibalistic behaviour due to lack of food items in its place
of inhabitance (Turpaeva, 1953). From the presence of
copepods, polychaetes and nematodes in H. woodmasoni
and their total absence in the diets of H. gibbosus, it can
reasonably be inferred that H. woodmasoni prefers shallower
depth zones. This is further confirmed by the presence of
trace quantities of euphausids and detritus and predominance
of shallow water foraminifers in the gut contents. Mary
and Ioannis (1999) reported that there exist strong
differences in the dietary behaviour of Plesionika ensis and
Polycheles typhlops inhabiting at greater depths than
Parapenaeus longirostris and Plesionika heterocarpus from
Eastern Mediterranean Sea.
The qualitative analysis of food in relation to size
showed that there exists significant variation in the diet
composition of juveniles and adults of both the species. In
H. gibbosus, immature male and female devoured more
actively on other crustaceans, sponges and echinoderms,
the former up to 80-89 mm and latter up to 100-109 mm
where as in adults of both the sexes, a glaring shift in the
diet composition was observed towards molluscs, fish scales
and nematodes. The percentage composition of foraminifers
declined steadily with the increase of length groups and in
adults, foraminifera was rarely observed in males and
females of H. gibbosus. In H. woodmasoni, juveniles
devoured less detritus and more foraminifers than adults
and with progression of length groups, the amount of
detritus in the diet also showed an increase thus exhibiting
more and more detritophagus behaviour with increasing
stages of growth. Ivanova (2000) also reported similar
findings in the diets of P. borealis from Flemish Cap in
north Atlantic.
Sex-wise analysis of food preference in various length
groups showed that in females of H. gibbosus and
H. woodmasoni the higher length groups showed more
selectivity in comparison with their males. Females of
H. woodmasoni showed preference to detritus, euphausids
and other crustaceans where as males preferred euphausids,
detritus, foraminifers and other crustaceans. In H. gibbosus,
females preferred euphausids, nematodes and sand particles
whereas non-selective feeding was observed in males by
the occurrence of diverse number of diets than females.
Ivanova (2000) noticed slight difference in the diets of both
the sexes of P. borealis where males showed rich diversity
of dietary preference. In contrast, females exhibited only a
narrow range of dietary variation.
Maturity stage-wise feeding intensity of H. gibbosus
and H. woodmasoni indicated that in both the species,
highest number of empty stomachs was observed in head
roes of females and matured males. Voracious feeding habit
in females after oviposition was observed as evidenced by
the occurrence of highest number of ‘full stomachs’ and
‘3/4full’ stomachs in the orange berry to black berry stages.
This finding strongly corroborates with that of Suseelan
(1985) who reported highest frequency of empty stomachs
in ovigerous females. The feeding intensity studies also
showed that occurrence of ‘trace’ stomachs were high in
all the months. This might be due to the faster digestive
rates of carnivores (Qasim, 1972) or may be due to
regurgitation while removing from deeper waters (Job,
1940). Low feeding intensity of head roes and matured
males are further explained on the basis of their lower
gastrosomatic index. In H. woodmasoni and H. gibbosus,
higher GSI values were observed in spent males whereas
in females, the GSI values were maximum in orange berries
and spent females. The lowest values recorded in head roe
females have been attributed to less space in the cephalic
region due to the fully developed ovaries thus affecting
food intake (Weinberg, 1980).
Acknowledgements
The authors are grateful to the Director, School of
Industrial Fisheries, Cochin University of Science and
Technology for providing necessary facilities to carry out
the work.
S. R. Radhika Rajasree and B. Madhusoodana Kurup
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Date of Receipt
: 26.04.2010
Date of Acceptance
: 29.07.2011