Fishery resources in arid zone mangroves in gulf of Kachchh, Gujarat, northwest coast of India

Article (PDF Available)inJournal of Ocean University of China 8(3):233-240 · September 2009with121 Reads
DOI: 10.1007/s11802-009-0233-3
Abstract
The finfish and shellfish resources were assessed quantitatively and qualitatively in regard to their abundance in creek waters at three sites within a period of two years, from January 1999 to December 2000, in the western mangrove areas of Kachchh. The catch rate varied from 0.69 to 6.99 kg h−1. It was low during monsoon (July to October), which could be due to the freshwater-flow-induced salinity reduction in all the sites. Among 38 species recorded, 5 were shellfish and 33 were finfish. The spawning period of fishes was found to be during summer and early monsoon period (May to August). Surface water temperatures varied from 17 °C to 37 °C. Salinity values varied from 34 to 44 and the pH ranged between 7 and 8.9. Variation in dissolved oxygen content was from 3.42 to 5.85 mL L−1. The high fishery densities in these semi arid mangrove creek areas were recorded during monsoon and early winter season.
J. Ocean Univ. China (Oceanic and Coastal Sea Research)
DOI 10.1007/s11802-009-0233-3
ISSN 1672-5182, 2009 8 (3): 233-240
http://www.ouc.edu.cn/xbywb/
E-mail:xbywb@ouc.edu.cn
Fishery Resources in Arid Zone Mangroves in Gulf
of Kachchh, Gujarat, Northwest Coast of India
A. Saravanakumar
1)
, M. Rajkumar
1),*
, J. Sesh Serebiah
2)
, and G. A. Thivakaran
3)
1) Centre of Advanced Study in Marine Biology, Annamalai University, Parangipettai – 608 502, Tamil Nadu, India
2) Marine Studies and Coastal Resource Management, Madras Christian College, Tambaran, Chennai – 600 059, Tamil Nadu, India
3) Gujarat Institute of Desert Ecology, Bhuj – 370 001, Gujarat, India
(Received November 8, 2007; revised December 8, 2008; accepted March 2, 2009)
Abstract The finfish and shellfish resources were assessed quantitatively and qualitatively in regard to their abundance in creek
waters at three sites within a period of two years, from January 1999 to December 2000, in the western mangrove areas of Kachchh.
The catch rate varied from 0.69 to 6.99
kg h
-1
. It was low during monsoon (July to October), which could be due to the freshwa-
ter-flow-induced salinity reduction in all the sites. Among 38 species recorded, 5 were shellfish and 33 were finfish. The spawning
period of fishes was found to be during summer and early monsoon period (May to August). Surface water temperatures varied from
17
to 37 . Salinity values varied from 34 to 44 and the pH ranged between 7 and 8.9. Variation in dissolved oxygen content was
from 3.42 to 5.85 mL
L
-1
. The high fishery densities in these semi arid mangrove creek areas were recorded during monsoon and early
winter season.
Key words mangroves; Gulf of Kachchh; Gujarat; finfish and shellfish; species diversity; richness; evenness
1 Introduction
The area with mangroves is well known for its impor-
tance as the most productive ecosystem. It can efficiently
fertilize the sea, potentially protect the coastal zone and
vitally serve the fishes as breeding and feeding grounds
(Ramaiyan et al., 2002). Adverse physico-chemical con-
ditions and biological parameters such as food supply and
predation generally influnce the temporal and spatial dis-
tribution of young finfishes in mangrove environment
(Krishnamurthy and Prince
Jeyaseelan, 1981). So juvenile
stock assessment and evaluation of fishery seed resources
may prove to be more convenient and reliable for an ap-
praisal of prospective commercial fishery. The fishery
resources in Gulf of Kachchh mangal have not received
attention in the last few decades. During 1972, Gopa-
lakrishnan et al. (1987) made attempts to survey the fish
and prawn seed resources of this area and reported 21
species of finfish and 5 species of shellfish. After several
years, Joseph and Soni (1990) made a few preliminary
observations on the prawn fishery of this region. Despite
of the above researches, no further study has been done
for this water area. Some researches on species’ composi-
tion and distribution of fin and shell fishes have been car-
ried out in some tropical estuaries and mangrove creeks
* Corresponding author. Tel: 04144-243223
E-mail:
arunachalashivamdr@yahoo.com
along the Indian coasts, which include the work of
Joyothi and Nair (1990), Joseph and Soni (1990), Chan-
drasekaran and Natarajan (1993, 1994), Mohan et al.
(1995, 1997), Chandrasekaran (2000) and Kathiresan and
Rajendran (2002).
Gujarat’s annual fishery production is about crores of
tons and 90% is contributed by marine fisheries. The state
ranks first in marine fish production, accounting for 20%
of the whole country’s catch supporting an estimated 3.6
lake fishing community. Among the total finfish landings
of Gujarat coast, Gulf of Kachchh contributes a major
share. Kachchh district alone contributed 82
473 tons du-
ring 1999–2000 (Gujarat Fisheries Statistics, 2000). Such
high fishery yield may be attributed to mangroves since
fish recruitment and mangrove cover are directly propor-
tional (Chandrasekaran and Natarajan, 1993). Hence, the
present work aims to assess the fishery potential, density
and diversity of Kachchh mangroves, and further assumes
its significance in view of the close relationship between
fishery resources and mangroves.
2 Materials and Methods
The sites were selected based on their proximities to
open seas and their levels of anthropogenic pressure. The
three selected sites, namely, Site 1 Jakhau
(Babber
Creek) (68.36
˚N, 23.30˚E), Site 2 Sangi – (Kharo Creek)
(68.31
˚N, 23.17˚E) and Site 3 Medi – (Sinthodi Creek)
(68.29
˚N, 23.27˚E) (Fig.1) were chosen with 5 km dis-
Saravanakumar et al./ J. Ocean Univ. China (Oceanic and Coastal Sea Research) 2009 8: 233-240
234
Fig.1 Map showing the study area.
tance between each other.
Monthly samples of finfish and shellfish were collected
within a period of two years from January 1999 to De-
cember 2000 by using a cast net with 3
m diameter (when
spread) and 7
mm mesh size. The net was operated onto
the water from the canoe or by one person standing in
waist-deep water. For effective sampling, sampling points
were fixed at regular distance in the 3 sites close to areas
where other parameters were investigated. In each sam-
pling point, 10 hauls were made and the C. P. U. E (catch
per unit effort) was estimated per hour. The collected
specimens were segregated into groups and weights were
measured in fresh condition. The finfish species were
preserved in 10% neutralized formalin and shellfish spe-
cies in 8% formalin solution. Finfishes were identified
using the methods following Fischer and Bianchi (1984),
Masuda et al. (1984), de Bruin et al. (1995) and Mohsin
and Ambiak (1996). Shellfishes were identified using
Sethuramalingam and Ajmal Khan’s method (1991).
Rainfall data were obtained from meteorological de-
partment at Bhuj, Kachchh Gujarat. The water tempera-
ture was measured in-situ through Merck mercury ther-
mometer with 0.1
accuracy. The salinity was estimated
by hand refractometer (Atago, Japan) and DO by
Winkler’s method on the spot. The pH value was meas-
ured with pH meter with reference to a standard buffer
solution. Biodiversity indices such as species diversity,
richness and evenness were calculated following the
standard formulae (Shannon and Weaver, 1949; Gleason,
1922; Pielou, 1966). The data thus collected was grouped
according to different seasons while a calendar year was
divided into 3 main seasons including winter (November
February), summer (March June) and monsoon (July
October).
Simple correlation coefficient (r) was calculated be-
tween physico-chemical parameters and fishery faunal
assemblage. Two-way ANOVA was employed to find out
the variations in physico-chemical parameters and fishery
assemblage in relation to sites and seasons.
3 Results
The total rainfall was 607 mm in 1999 and 272 mm in
2000. Comparatively, rainfall rate was higher in the first
year than in the second year. Most of the rainfall occurred
as downpour, confined to 4
9
d of the year during July
and August. The surface water temperature ranged from
17 to 37
(Fig.2) and salinity from 34% to 44% (Fig.3).
The dissolved oxygen concentration ranged from 3.42 to
5.85mL
L
-1
(Fig.4). The monthly pH fluctuation was with
Fig.2 Seasonal variations of temperature recorded from
sites 1, 2 and 3.
Saravanakumar et al./ J. Ocean Univ. China (Oceanic and Coastal Sea Research) 2009 8: 233-240
235
Fig.3 Seasonal variations of salinity recorded from sites 1,
2 and 3.
Fig.4 Seasonal variations of dissolved oxygen recorded
from sites 1, 2 and 3.
Fig.5 Seasonal variations of pH recorded from sites 1, 2
and 3.
a range from 7.0 to 8.9 (Fig.5). The maximum value was
recorded in winter and minimum in monsoon season.
The total catch quantity from all the 3 sites was 218.5
kg. The catch rate varied from 0.69
kg h
-1
to 6.99 kg h
-1
(Fig.6). In general, in these three sites the highest catch
rate was during winter season and the lowest was during
monsoon. The average catch rate was 2.48
kg h
-1
, 2.94 kg h
-1
and 3.67
kg h
-1
from sites 1, 2 and 3 respectively. The
two-way analysis of variance showed no significance
between any two sites and any two seasons.
A total of 38 species were recorded in the present study,
among which 5 species were shellfish and 33 were finfish.
In site 1, the total number of species was 31 including 5
species of shellfish and 26 species of finfish. In site 2
totally 31 species were recorded including 5 shellfish
species and 26 finfish species. In site 3, totally 37 species
were recorded including 5 species of shellfish and 32
species of finfish. There were more finfish species than
shellfish species (Table 1).
At site 1, the highest composition percentage of finfish
was 96.8% during early monsoon and the minimum was
82.8% during summer. With shellfish the lowest percent-
age was 3.4% in early monsoon and the highest was
17.2% in the summer. At site 2, the highest percentage of
finfish was 94.5% during early winter and the lowest was
80.0% during the monsoon season. With the shellfish, the
lowest and highest percentages were 5.5% (winter) and
20.0% (monsoon) respectively. At site 3, the highest per-
centage of finfish was 97.06% in monsoon and the lowest
was 80.0% during late winter. With shellfish, the lowest
and highest values were 2.94% during monsoon and
20.0% during late winter respectively (Figs.7a, b and c).
Fig.6 Monthly variations of fishery resources at sites 1, 2
and 3.
Fig.7 Fin and shellfish percentage composition during
1999 to 2000 at sites 1(a), 2(b) and 3(c).
The diversity values varied from 2.25 to 3.07 bits/ind.
The maximum species diversity was recorded during
winter and the minimum during the monsoon season
a
b
c
Saravanakumar et al./ J. Ocean Univ. China (Oceanic and Coastal Sea Research) 2009 8: 233-240
236
Table 1 Check list of shell and finfishes recorded at sites 1, 2 and 3
Shell fishes Babber creek (Site 1) Kharo creek (Site 2) Sinthodi creek (Site 3)
1 Scylla serrata + + +
2 Metapenaeus kutchensis + + +
3 M. monoceros + + +
4 M. brevicornis + + +
5 Penaeus monodon + + +
Fin fishes
Scat
6 Scatophagus argus + + +
Clupeioids
7 Stolephorus indicus + + +
8 Thryssa mystax + + +
9 Nematalosa nasus + +
10 Dussumeria acuta + +
11 Hilsa ilisha + +
Mullets
12 Liza parsia + +
13 Mugil cephalus + + +
Half and Fullbeaks
14 Hemiramphus far + + +
15 Strongylura leiura + +
Flat head
16 Platycephalus indicus + + +
Glass perch
17 Ambassis commersonii + + +
Groupers
18 Epinephelus
caeruleopunctatus
+ +
Sweet lip
19 Pomadasys sp. + + +
Whitings
20 Sillago sihama + + +
Jacks and pamponas
21 Atule mate + + +
22 Caranx para + + +
23 Caranx sem + + +
24 Megalapsis cordyla + +
Moon fishes
25 Mene maculata + +
Silver bellies
26 Leiognathus equulus + + +
Snappers
27 Lutjanus lutjanus + +
28 Lutjanus johnii + + +
Mojarras
29 Gerres filamentosus + + +
30 Gerres abbreviatus + +
Emperor
31 Lethrinus nubulosus + +
Tiger perche
32 Terapon jarbua + + +
33 Terapon puta + +
(to be continued)
Saravanakumar et al./ J. Ocean Univ. China (Oceanic and Coastal Sea Research) 2009 8: 233-240
237
(continued)
Shell fishes Babber creek (Site 1) Kharo creek (Site 2) Sinthodi creek (Site 3)
Cichlid
34 Etroplus suratensis + +
Slipmouth
35 Secutor incidiator + +
Mudskipper
36 Boleopthalmus boddarti + + +
Tongue soles
37 Cynoglossus puncticeps + + +
Puffers
38 Chelonodon patoca + +
Table 2 Fisheries diversity, richness and evenness values at sites 1, 2 and 3 during 1999 to 2000
Site 1 Site 2 Site 3
Year
Winter Summer Monsoon Winter Summer Monsoon Winter Summer Monsoon
1999 2.78 2.29 2.25 3.01 2.63 2.62 2.95 2.62 2.25
Diversity
2000 2.88 2.51 2.35 3.07 2.69 2.67 2.82 2.51 2.31
1999 0.97 0.89 0.87 0.97 0.87 0.83 0.96 0.90 0.85
Richness
2000 0.98 0.89 0.88 0.98 0.89 0.85 0.96 0.89 0.87
1999 0.86 0.75 0.70 0.91 0.85 0.81 0.85 0.74 0.71
Evenness
2000 0.87 0.77 0.71 0.93 0.84 0.80 0.85 0.74 0.73
(Table 2). The two-way analysis of species diversity showed
no significant variation between sites and seasons. The
overall species richness values of the study area varied
from 0.83 to 0.98. Generally richness value was higher
during winter and lower during the monsoon season (Ta-
ble 2). No significant variation was observed between
sites and seasons through two-way analysis. The species
evenness index varied from 0.70 to 0.93, while the
maximum value was found during winter and the mini-
mum during the monsoon season (Table 2). The two-way
analysis showed no significant variation between sites
and seasons.
4 Discussion
Rainfall is the most important cyclic phenomenon in
tropical countries as it brings important changes in the
hydrographical characteristics of marine and estuarine
environments. In the present study, peak values of rainfall
were recorded during the monsoon months of July and
August. The rainfall in India is largely influenced by two
monsoons, the southwest monsoon on the west coast of
northern and northeast India and the northeast monsoon
on the southeast coast (Perumal, 1993). In Gujarat, par-
ticularly in Kachchh district, the monsoon is preceded by
hot dry weather from March to June. The rain sets in over
most of Gujarat from late June to September and no rain
in November (Saravanakumar et al., 2007a). The months
of December, January and February are rainless. Kachchh
district experiences typical ‘Monsoon climate’ with a
rainy season of four months from the mid-June to Sep-
tember, it is found that 93 to 98 percent of the annual
rainfall occursin this period (Saravanakumar et al.,
2007b).
The surface water temperature varied from 17
to
37
during winter and summer seasons. There was a
steady increase in temperature from March to June, which
peaked during May and a low temperature of 17
was
recorded during winter. All the sites showed similar trend
with similar seasonal changes. Generally, surface water
temperature is influenced by the intensity of solar radia-
tion, evaporation, insolation, freshwater influx and cool-
ing and mixing up with ebb and flow from adjoining
neritic waters (Govindasamy et al., 2000). In the present
study, summer peaks and monsoonal troughs of air and
water temperatures were observed, which has been ob-
served in the west coast of India (Saravanakumar et al.,
2007a, b). Statistical analysis showed a positive correla-
tion between air and surface water temperatures for all the
three sites.
Salinity varied from 34 to 44 during monsoon and
summer seasons. The minimum salinity was presumably
due to the influence of heavy rainfall and the resultant
river run-off, which is a regular annual event in this area
during monsoon. Salinity acts as a limiting factor in the
distribution of living organisms, and its variation caused
by dilution and evaporation is most likely to influence the
fauna in the intertidal zone (Sridhar et al., 2006; Sarava-
nakumar et al., 2008). Generally, changes in salinity of
brackish water habitats such as estuaries, backwaters and
mangroves are due to influx of freshwater from land,
caused by monsoon or by tidal variations. This is further
evidenced by the negative correlation between salinity
and rainfall (r =
0.350 at site 1, r = 0.513 at site 2 and r
=
0.500 at site 3). Salinity showed a significant positive
correlation with temperature. In the present study, salinity
in all the sites was high during summer season and low
during the monsoon season. Higher values during sum-
Saravanakumar et al./ J. Ocean Univ. China (Oceanic and Coastal Sea Research) 2009 8: 233-240
238
mer may be attributed to the low amount of rainfall, high
degree of evaporation and dominant neritic water from
open sea (Saravanakumar et al., 2007b). On the other
hand during the monsoon season, more rainfall and con-
sequently more freshwater inflow from the land would
moderately reduce the salinity. Thus the variations in sa-
linity in the study sites were mainly influenced by the
rainfall and inflow of freshwater as reported in the Gulf
of Kachchh by Vijayalaksmi et al. (1993), in the Goda-
vari estuary by Saisastry and Chandramohan (1990), in
coastal waters of Kalpakkam by Satpathy (1996).
The dissolved oxygen content was high (5.85
mL L
-1
)
during the monsoon (August) and low (3.42
mL L
-1
) dur-
ing the summer (May). Season-wise observation of dis-
solved oxygen showed an inverse trend against tempera-
ture and salinity. It is well known that temperature and
salinity affect dissolution of oxygen in seawaters
(Vijayakumar et al., 2000). In the present investigation,
higher values of dissolved oxygen were recorded during
monsoon months in all the sites. Relatively lower values
found during winter could be mainly due to reduced agi-
tation and turbulence of the coastal and estuarine waters.
Higher dissolved oxygen concentration observed during
the monsoon season might be due to the cumulative ef-
fects of higher wind velocity coupled with heavy rainfall
and the resultant freshwater influx. Saravanakumar et al.
(2007a, b, 2008) attributed seasonal variation of dissolved
oxygen mainly to freshwater influx and ferruginous im-
pact of sediments. Furthermore, significant inverse rela-
tionship between rainfall and nutrients indicated that
freshwater input constituted the main source of nutrients
in the mangroves. Two-way analysis of variance on the
results showed that there was no significant variation be-
tween sites and seasons.
The pH varied from 7.0 to 8.9 during monsoon and
summer seasons. Hydrogen ion concentration (pH) in
surface waters remained alkaline throughout the study
period in all the sites with the maximum values occurring
in the summer and winter seasons and minimum values
occurring in the monsoon season. Generally, fluctuation
of pH values during different seasons of the year is attrib-
uted to factors like removal of CO
2
by photosynthesis
through bicarbonate degradation, dilution of seawater by
freshwater influx, reduction of salinity and temperature
and decomposition of organic matters (Paramasivam and
Kannan, 2005; Saravanakumar et al., 2008). Statistical
analysis also revealed that salinity had a significant nega-
tive correlation with rainfall.
The Kachchh coastal land is a semi arid area lacking
soil fertility and freshwater flow. Mangroves are the only
prominent vegetation in the coastal belt and hinterland.
These mangroves can provide suitable food and reduce
predation as a shelter, which is advantageous to juveniles
of many species. Furthermore, it has been demonstrated
that many juveniles prefer shallow waters with high tur-
bidity. Such areas usually consist of high productivity and
can help the juveniles to escape from predators (Russell
and Garrett, 1983). Additionally, decomposed detritus of
mangrove leaves can serve ideally as food with high ca-
loric value to the epibenthic and nektonic animals in
mangrove biotopes (Kathiresan and Rajendran, 2002).
In the present study, catch rate varied from 0.69 to 6.99
kg
h
-1
. The catch rate was low during monsoon (July to
October), which could be due to the freshwater flow that
caused salinity reduction in all the study sites. Elsewhere
in west coast, similar monsoon-related salinity reduction
and the concomitant low catch per unit effort have been
reported in Thane basin area (Joyothi and Nair, 1990). In
the present study, abundance of prawns reached a peak in
monsoon season. Similar observations were reported in
Goa mangrove creek by
Achuthankutty and Sreekumaran
Nair (1980) and in Gulf of Kachchh by Gopalakrishnan
et al. (1987). The highest catch of shellfish, especially
shrimps, was greater in mangrove-rich areas than in man-
grove-low areas (Kathiresan and Rajendran, 2002). The
mangrove waters retained approximately 65 billion
penaeid prawn larvae annually prior to their settlement in
coastal nursery grounds in the Klang Strait of Malaysia
(Chong et al., 1996). With finfish, the highest catch was
recorded during winter (November to February), as the
post-larvae prefer the stable environment in the aquatic
biotopes after monsoon (Robertson and Blabber, 1992).
High finfish juvenile abundance was recorded during
monsoon in the present study; it could be because the out
welling of detritus could provide important food/habitat
for juvenile shrimps in mangrove water ways and also the
abundance in nutrients and sediments of terrestrial origin,
which are favourable for the production of high biomass
of shrimps and finfishes (Robertson and Blabber, 1992).
Reproductive activities of coastal marine fishes and
prawns extend for a considerable period of the year in
tropical waters (Rajendran and Kathiresan 1998, 1999a,
b). In the present study the spawning periods of fishes
were found to be during summer and early monsoon pe-
riod (May to August). A similar trend of low population
density during monsoon was observed along the Indian
coastal waters by Achuthankutty and Sreekumaran Nair
(1980) and Sambandam et al. (1982).
In the study sites of Kachchh mangrove area, totally 38
species were recorded. Among these species, 5 species of
shellfish, namely S.serrata, M. kutchensis, M. brevicornis,
M. monoceros and P. monodon, were commonly encoun-
tered and M. kutchnesis was dominant throughout the
study period. Finfish groups like Jacks and pamponas,
mullets and clupeoides were dominant in all the study
sites. The most dominant finfishes were C. para, C. sem,
M. cordyla, T. mystax, D. acuta, N. nasus and M. cepha-
lus. Puffers, moon fishes and groupers were rarely found
in the present study. Similarly, several investigations
made in other areas also found that the mangroves sup-
ported a rich fish fauna ranging from 26 to 197 species
with fish densities varying from 0.3 to 161 fish m
-2
, and
the biomass estimates were mostly in the range of 7
29 g m
-2
(Robertson and Blabber, 1992; Vance et al., 1996).
The percentage composition of finfishes ranged from
80.0 to 97.05%. The highest value of 97.05% was re-
corded during late October. These high percentages of
finfish juveniles were caught in site 3 in a spawning sea-
Saravanakumar et al./ J. Ocean Univ. China (Oceanic and Coastal Sea Research) 2009 8: 233-240
239
son, when the juveniles prefer mangrove swamp for
avoiding predators (Robertson and Blabber, 1992).
Diversity and richness values ranged from 2.25 to 3.07
and 0.83 to 0.98 in the present study. The highest and
lowest values were reported during winter and monsoon
months, respectively. Occurrence of minimum number of
species and individuals was due to lowered water salinity
that caused low diversity values during monsoon. In addi-
tion, low diversity values were also due to the prepon-
derance of two or three species, which was clear in the
present observation and a similar pattern in North Florida
salt marshes (Subramanyan and Drake, 1975). It is widely
accepted that diversity increases with an increase of the
environment stability in aquatic biotopes (Rajendran and
Kathiresan 1998, 1999a, b; Kathiresan and Bingham,
2001). The high diversity values recorded during winter
in the present study indicated very well that more stable
environmental conditions prevailed in this period,
whereas the low values recorded during monsoon might
be due to the sharp decrease in salinity and other phys-
ico-chemical changes in the marine environment, which
was affected by inundation and influx of freshwater in the
system. Similar observations were reported in other three
mangrove areas by Kathiresan and Rajendran (2002).
Similar to diversity values, evenness values were also low
during monsoon and high during winter. In general, the
Kachchh mangrove area sustained a fairly good fishery
potential. During winter (November – February), the bio-
diversity of fish and crustaceans in this area indicated a
healthy ecosystem.
5 Conclusions
From the present study on fin and shell fish faunal den-
sity and diversity, it is quite clear that Kachchh mangrove
regions appear to be a healthy ecosystem with a pristine
nature. Therefore, the present baseline information of the
fin and shell fish resources and abundance would form a
useful tool for further ecological assessment and moni-
toring of these coastal ecosystems of western mangroves
of Kachchh.
Acknowledgements
The authors would like to thank Gujarat State Forest
Department for its giving permission to carry out this
study. We are grateful to Director of Gujarat Institute of
Desert Ecology and Prof. T. Kannupandi, CAS in Marine
Biology, Parangipettai, Annamalai University, Tamilnadu
for their constant encouragement and advice in various
stages of the studies.
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(Edited by Ji Dechun)
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