380-J._INDIAN_FISHERIES_ASSOIATION_1994 by liamei12345

VIEWS: 18 PAGES: 39

									Journal of the Indian Fisheries Association
24.1994 (Proc. Nat. Symp. Aquacrops),   1~39


ESTIMATES OF GROWTH, MORTALITY, RECRUITMENT PATTERN
       AND MSY OF IMPORTANT RESOURCES FROM
               THE MAHARASHTRA COAST


 . SUSHANT K. CHAKRABORTY, VINAY D. DESHMUKH, MOHAMMAD
     ZAFAR KHAN, KUBER VIDYASAGAR AND SADASHIV G. RAJE,
  Bombay Research Centre of Central Marine Fisheries Research Institute,
     Army & Navy Buildings, 148, M.G. Road, Mumbai . 400 001.

                                               ABSTRACT
    Based on the data collected from the year 1987 - 1991 the growth,
mortality and recruitment pattern of eighteen species of fish, two
species of cephalopods and four species of penaeid prawns have been
presented in the present communication_ The total mortality coefficient,
(Z) varied from lowest of 1.20 for O.cuvieri to a highest of 10.78 for
P.stylifera. The natural mortality coefficient, (M) varied from 0.52 for
T. thalassinus to 3.44 for S.crassicornis.
   The average annual yield of eighteen species of fish, four species of
prawns and two species of cephalopods are 65,083, 38,404 and 11,373
tons as against the MSYof 83,023, 72,460 and 10,475 tons respectively.
The MSY estimated for the total fish stock is 1,77,753t where as the
present yield is 1,14,859t. This indicates that higher yield can be
obtained by increasing the effort.


INTRODUCTION                                        craft began in the early sixties and
                                                    continued on increasing till mid
    The state of Maharashtra with a
                                                    eighties . The increase in the
coastline of 720 km. and continental
                                                    mechanization of the fishing fleet has
shelf of 89,096 sq. km. has rich
                                                    however, slowed down. The number
potential for marine fisheries. The
                                                    of units operating now at new Ferry
areas of potential fishing grounds in
                                                    Wharf and Sassoon Docks centres are
o to 50 m .:..nd 50-200 m depths are                about 600 and 450 respectively. The
2.55 and 10.48 million hectares
                                                    description of the craft, gear and area
respectively (Srinath et 01., 1987). It
                                                    of operation of this fishing fleet has
contributes about 16% of the total
                                                    been described by Chakraborty et al.
marine fish landings of India. The
                                                    (1983). But the depth of operation of
fishing and allied activities are very
                                                    the commercial trawlers have
well developed in the state in general
                                                    increased from 40 to 70 m and the
and Bombay in particular. The
                                                    duration of fishing has also gone up
process of mechanization of fishlng
                                                    from 3 -4 days to 5-6 days.
 2                             CHAKRABORTY ET AL.

    In the present communication the       better understanding of multi species
length frequency data collected on         fishery in the region.
various fish, penaeid prawns and
cephalopods were used fof growth,
mortality, recruitment and estimation      MATERIAL AND METHODS
of maximum sustainable yield. The
                                               Weekly length frequencies on
data cover fourteen genera of fish
                                           various species were collected at the
which includes eighteen species, two
                                           landing centres. In the present
genera of cephalopods with as many
                                           communication data collected for the
species and three genera of prawns
                                           years 1987-1991 have been used. The
covering four species. The length
                                           length frequencies were grouped in
frequency data of two species of
                                           different length classes depending on
perches (Epinephelus diacanthus and
                                           the largest size recorded and this was
Priacanthus hamrur) and one species
                                           raised for the day and subsequently
of sciaenid (Pennahia .macrophtha-
                                           for the month using the method of
Imus) have been collected from
                                           Sekharan (1962). The von Berta-
Sassoon Docks as these three species
                                           lanff'y's (1938) growth parameters, the
are not represented in adequate
                                           asymptotic length (L~) and growth
quantities at New Ferr! ·~harf.
                                           cofficient (K) were estimated using
Though, Harpodon neher/ius and .
                                           ELEFAN programme developed by
Coilia dussumieri are landed in
                                           Gayanilo et al. (1988). The von
appreciable quantity by trawlers, the
                                           Bertalanffy's equation is as follows.
major gear for these resources is IIdol"
net which is operated mainly in the           Lt =   L~   _ (l_e-K (t-to)j
inshore waters. Therefore, the length
                                              This programme does not produce
frequency data for these two species
                                           an estimate of to'
were collected from Satpati, one of
                   ll
the major "dal net centre in                  The total mortality coefficient (Z)
Maharashtra. For rest of the species       has been estimated by length-
the data were collected from New           converted catch curve method of
Ferry Wharf.                               Pauly (1982) and the natural
                                           mortality coefficient was estimated
   The growth and mortality
                                           mainly by Pauly's (1980) emperical
parameters form the basis in the
                                           formula which is as follows.
stock assessment and formulating
the management strategy of the                Log M = -0.0066+0.279*Log Loo
resources. Although, information on        + 0.6543 Log K+0.4634* Log T
these parameters of some of the
                                              where Loa is in em and
species are available from Bombay
                                           temperature is in degree centigrade.
waters, they are few and scattered.
                                           The mean environmental tempera-
This is an attempt to bring out as
                                           ture of 27 .2°e was taken from Bapat
much information in one place for
         GROWTH, MORTALITY, RECRUITMENT AND MSY OF RESOURCES                    3

et al. (1982). The recruitment pattern     stocks studied, eleven are optimaly
was worked out to assess the               exploited and seven are under-
seasonality of recruitment of the          exploited (Figs. 1-19) The penaeid
stock investigated.                        prawns appeared to be under-
                                           exploited where as cephalopods are
   Fishing mortality coefficient 'F'
                                           optimally exploited (Figs. 20-29).
was computed by subtracting (M)
from (Z) and the exploitation ratio            Fourteen species of fish analysed
was derived from the relation.             show recruitment in two pulses while
                                           a couple of species indicated
               E = F/Z
                                           recruitment in single pulse while r est
    The maximum sustainable yield          of the two species it could not be
(MSy) was estimated by Corten's            resolved (Figs .I-18). Both the species
(1974) formula and the calculations        of cephalopods indicated recruitment
were done on a PC using ELEFAN             in two pulses. Among the penaeid
II programme .                             prawns' P.stylifera showed recruit-
                                           ment in one pulse and M .monoceros
    The summary of various parameters
                                           shows recruitment in two pulses. The
on growth, mortality and recruitment
                                           recruitment pattern could not be
pattern obtained for all the species are
                                           resolved     for     M. affinis    and
given in Table 1 and the estimates of
                                           S.crassicornis femal e shows recruit-
MSY, standing stock and annual and
                                           ment in two pulses and male in one
average yield for 1987-1991 period in
                                           pulse. (Fig. 28 & 29).
Table 2.
                                               The gear used is shrimp trawl
                                           and the effort is mainly directed
RESULTS AND DISCUSSION                     towards catching of prawns. But in
                                           the last four to five years
    The total mortality coefficient (Z)
                                           cephalopods have also gained
varied from lowest of 1.20 for
                                           economic importance. Because of
O.cuvieri (Fig.3) to the highest of 5.0
                                           this, a part of the effort is also
for O.militaris (Fig.17) amongst fish,
                                           directed towards catching of
2.09 to 3.0 for S.acul ea ta and
                                           cephalopod resourc es . Recently,
L.duvaucelii (Figs.20 & 21 ) amongst
                                           rihbonfish, hecause of its newly
cephalopods and 3.82 for M.
                                           acquired export value, is also caught
monoceros (female) (Fig.24) to 10.78
                                           in good quantity.
for P.stylifera (Male) (Fig.2 3) among
prawns . The natural mortality                 It is to be noted that all the
coefficent (M ) ranged from 0.52           . species of fish and cephalopods are
(A.t halassinus) (Fig.16) to 3.44            landed as by-catch of the shrimp
(S.crassicornis) female ) (Fig.28).          trawl. The occurence of by-catch
                                             raises a number of biological,
   Out of eighteen species of fish
                                             economical and social questions. It
  4                             CHAKRABORTY ET AL.

 Table 1        Growth and mortality parameters of the species studied
        Name                         L~          K      Z      M        F       E
  Scoliodon laticaudus                  726     0.48   3 .00   0.90    2.10     0.70
          (female)
  Seoliodon wticaudus                   740     0.63   3.00    0.90    2.10     0.70
          (male)
  Otolithes cuvieri                     398     0.52    l.20   0.86    0.34     0.28
  Johnieops vogleri                     345     0.72 3.20      l.10    2.10     0.65
  Johnius macrorhynus                   350     0.75 4.10      l.20    2.90     0.70
  Johnieops sina                        240     0 .80 6.56     l.60    4.96     0.75
  Pennahia macrophthalamus              245     0 .64 2.00     l.30    0.70     0.35
. N emipteru s japonicus                335     0 .65 2 .80    l.10    l.70     0.60
  Nemipterus n:-esoprion                286     0.71 3.44      1.40    2.04     0.65
  Epinephelu s diaeanthus               502     0 .61   l.50   l.12    0.40     0.26
  Priacanthus ha1J1,TUT                 345.5   0.66  . 2.50   l.10    1.40     0.56
  Saurida tumbil                        600     0.51 2.80      l.00    l.8 0    0.64
  Saurida undosquamis                   421     0.51 2.52      l.10    l.42     0.56
  Harpodon nehereus                     413     0.73 3.10      l.53    l.57     0.51
  Tachysurus caelattts                  521     0.68 3.50      l.10    2.40     0.68
  Tachysurus thalassinus                8 50    0.28 l.50      0.52    0 .9 7   0.65
  Osteogeneiosus militaris              600     0 .65 5.00     l.10    3.90     0.78
  CoUia dussumieri                      230     l.20 7.05      3.00    4 .00    0.57
  Tric hiurus lepturus' .            1480       0.40 2.62      0.75    l.87     0.71
  Loligo duvaucelii                     343     0.49 2.09      l.10    0 .99    0.47
  Sepia aeuleata                        297     0 .56 3.40     l.10    2.30     0.67
  Parapenaeopsis stylifera            . 140.8   2.15 7.60      3.60    4.00     0.53
          (female)
  Parapenaeopsis s tylifera             119.2   l.45 10.78     2.96    7.82     0.73
          (male)
  M etapenaeus m onoceros               219.2   1.40   3.82    2.40    l.42     0.37
          (female)
  M etap enaeus monoceros               180.5   l.35   4.50    2.50    2 .00    0.44
          (male)
  M etapenaeus affinis                  188.8   l.47   6.78    2.5 8   4.20     0.62
          (female)
  M etap enaeus affinis                 15l.5   l.50   4.60    2.78    l.12     0.40
          (male)
  Solenocera crassicornis               139     2.00 10.36     3.44    6 .92    0.67
          (female)
  S olenoce.ra crassicornis               92    l.50   6.00    3 .20   3.60     0.53
          (male)
                           Lao is in mm and     K is annual
        GROWTH, MORTALITY, RECRUITMENT AND MSY OF RESOURCES             5

Table 2 : Yield and stock parameters of fish, cee.halopodsand prawns
         Name              Yield LcIL~ MlK     E Emax     F    Y/F   MSY
Scoliodon laticaudus        2349 0.77 1.87 0.70 1.0      2.10 ll19   3356
         (female)
Scoliodon 1aticaudus .                        0
                            2150 0.46 1.42 . .70 0.66 2.10 1024      2024
         (male)
Otolithes c"uvieri          6063 0.40 1.65 0.28 0.61 0.34 17832 13209
Johnieops v,lgleri          6126 0.40 1.52 0:65 . 0.67 2.10 2917     6314
Johnius macrorhynus         4958 0.45 1.60 0.70 0.66 2.90 1709       4674
Johl1:ieops sina            2118 0.60 2.00 0.75 1.00 4.96        427 2824
P.ennahia macrophthalamus 1038 0.44 2.03 0.35 0.70 0.70 1483         2076
Nemipterus japonicus        1242 0.48 1.69 . 0.60 0,71 1.70      731 1470
Nemipterus mesoprion         962 0.49 1.97 0.65 0.75 2.04        472 ll10
Epinephelus diacanthus       280 0.46 1.83 0.26 0.71 0.40        701  761
Priacanthus hamrur           283 0.56 1.66 0.56 0.83 1.40        202  606
Saurida tumbil              3193 0.43 1.97 0.64 0.68 1.80 1774       3388
Saurida undosquamis          171 OA7 2.15 0.56 0.77 1.42         120  236
Harpodon nehereus          37270 OAO 2.09 0.51 0.65 1.57 23739 47650
Tachysurus cae latus         453 0.71 1.61 0.68 1.00 2.40        189  666
Tachysurus thalassinus      1990 0.28 2.16 0.65 0.52 0.97 2051       1588
Osteogeneiosus militaris    2948 0.53 1.69 0.78 0.79 3.90 2268       3004
Coilia dussumieri           4793 0.64 2.22 0.57 1.00 4.00 2397       8715
Trichiurus leplurus        23965 0.44 1.87 0.71 0.68 1.87· 12815 22986
Loligo duvaucelii           6125 0.29 2.26 OA7 0.53 0.99 6187        6895
Sepia aculeata              5248 0.30 1.96 0.67 0.53 2.30 2281       4143
Parapenaeopsis stylifera   12320 0.64 1.67 0.53 1.00 4.00 3080 23245
         (female)
Parapenaeopsis stylifera    5646 0.72 2.04 0.73 1.00 7.82        722 7734
         (male)
Metapenaeus monoceros       4563 0.59 1.71 0.37 1.00 1.42 3213 12332
         (female)
Metap~naei!-s, monoceros    1709 0.61 1.85 0.44 0.91 ' 2.00     855  3519
,        (male)
Metapenaeus affinis         6227 0.72 1.75 0.62 1.00 4,20 1483 10044
         (female)
Metapenaeus affinis         2876 0.79 1.85 0.40 1.00 1.12 1580       7190
         (male)
Solenocera crassicornis     4401 0.68 1.72 0.67 1.00 6.92       636  6569
         (femule)
Solenoce·ra crassicornis ·   662 0.71 2.13 0.53 1.00 3.60        184 1249
         (male)
Lc = Length at first capture, Emax ::::: -Maximum exploitation rate,
Y IF = Standing stock.
 6                            CHAKRABORTY ET AL.

is noteworthy that though by-catch       is estimated at 10,475t. The
forms quantitatively a large consti-     estimated MSY of total fish stock is
tuent, economically it does not fetch    1,77,785t whereas the present yield
good value. But though not very          is 1,14,859t. Therefore, there is a
remunerative, their value is not         scope to increase the total fish catch
altogether negligible. The value of      by 54.78%.
minor species can make all the
                                             The "dol' net is an important gear
differences between a profitable and
                                         operated in the northern part of
nonprofitable trip (Gulland, 1983).
                                         Maharashtra .        Bombay      duck
   The groupwise distribution of         Harpodon nehereus is the target
catch shows that fish forms 56.77%,      species of "dol" net and Coilia
prawns 33.4% and cephalopods 9.9%.       dussumieri is one of the by-catch.
Out of eighteen species of fish stocks   The average yield of the former
studied eleven are optimally             species was 37,270t whereas the
exploited whereas seven species are      MSY was 47,650t. C.dussumieri the
underexploited. The notable under-       average yield was 4,793t whereas the
exploited resources are O. cuvieri,      MSY was 8,715t. This species
P. macrophthalamus, E. diacanthus,       appears to be under exploited.
P. ham'rur, S. laticaudus (female),      Bombay duck shows a wide year to
C.dussumieri and T.caelatus. Both        year fluctuation in the catches (Table
the species of cephalopods appear to     2) with 18,565t in 1991 to 25,222t in
be optimally exploited. The four         1989 and 48,000t in 1990. Srinath et
species of prawns which together         al. (1987) observed that catches by
constitute 76.3% of the penaeid          the dolnetters did not respond
prawns in Maharashtra appear to be       positively to the effort expended and
underexploited.                          any change in the effort may not
                                         have any impact on the landings. '
   The standing stocks of eighteen
                                         Khan (1989) also observed that the
species of fish is 78,420 t, of two
                                         dol net fishery is labour intesive, the
species of cephalopods is 8,468t and
                                         effort is regulated depending on the
four species of prawns is 1l,753t.
                                         catch per haul. Due to economic
     The present average yield of        reasons the fishing is suspended
 eighteen species of fish is 65,082t     when the CPUE is very low.
 whereas the MSY is 83,023t thus
                                             Gulland (1975) suggested that if
,giving scope of increasing the catch
                                         the ' E' value is more than 0.5, the
 by 27.57%. Th", present yield of four
                                         stock understudy appears to be
 species of prawns is 38,404t whereas
                                         overexploited. In the present study
 the MSY is 72,460t giving a scope
                                         we find that in most of the species of
 for increasing the catch by 88.67%.
                                         fish, prawns and cephalopods the 'E'
 The present average yield of
                                         is more than 0.5. In spite of that
 cephalopod is 1l,373t and the MSY
                                         these species do not show any sign
          GROWTH, MORTALITY, RECRUITMENT AND MSY OF RESOURCES                   7

 of overexploitation like drastic          additional 60,000 tonnes of trawl
 decline in catch and catch rate,          catch are expected by increasing 40%
                                           of efforts at 1984 leveL It was further
      It can thus be stated that perhaps
                                           suggested that the increase could be
  the concept of Eopt of 0,5 may not
                                           made in a phased manner. There
  hold true in the tropiGs, It is also
                                           were 1792 trawlers in operation in
  observed that all the species studied
                                           Maharashtra in1984 since then the
  have in general a small standing
                                           numbers of tawlers have increased
  stock and the LclL= ratio is also very
                                           to 2118 in 1992-1993, Despite this
, high, It is noteworthy that a small
                                           increase in the number of trawlers
  standing stock is able to generated a
                                           in Maharashtra in the last eight
  higher yield in the north west coast
                                           years there is no decline in the total
  of India (Table 2), The chief reasons
                                           fish landings,
  may be attributed to
                                               The present LclL= for all the
a, Faster rate of growth,
                                           species taken together is 0,53 and
b, Abundance of food supply,               the estimated exploitation ratio is
                                           0,53 whereas using the relative yield
c, Less abundance of predators like
                                           per recruit model (Fig, 30) the
    "Ghal", IIKoth    "Dara" and
                      ll
                           ,
                                           estimated E max is 0,83 at which
    "Karkara" and
                                           the projected yield (MSY) would be
d, Majority of species have protracted     1,77,785t. The present avrage yield
    spawning which results in              is 1,14,859 (combined catch of all the
    recruitment through out the year,      species), The study indicates that at
                                           present none of the species studied
    Jones and Banerji (1973)
                                           is over exploited, Most of them are
estimated that the potential yield of
                                           either optimally exploited or
Maharashtra waters as 2,62 lakh
                                           underexploited, The study thus
tonnes, George ef al. (1978)
                                           indicates that the present fishing
estimated the potential yield of north
                                           fleet could be safely be increased to
west coast off India as 8,43 lakh
                                           25% without having any adverse
tonnes based on the rate of
                                           effect in the fishery,
production, Antony Raja (1974) gave
an estimate of 3.53 lakh tonnes in           . This document would be useful
which 2.7 lakh tonnes obtainable           to fishery biologists and management
from the 0-50m depth zone . Kalawar        people in fishery and related
(1978) and Srinath et al. (1987)           industries as it covers the age,
arrived at potential yield of 3,74 lakh    growth~    mortality, recruitment
tonnes, They also observed that the        I1.tttern and MSY of most of the
relationship between catch and             co ltime,rci all y important fish,
e fforts by trawlers was C ~               cephil-lopods and prawns.
O,65lfLoo4(?~O,9) and suggested that
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Fig . 1   S coliodon laticaudus (Femal~) L = =726mm, K=0 .48, Z=3 .0, A nnual recruitmen t occured in two p ulses.
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Fig. 2   Scoliodon laticaudus (Male) L~=470mm, K=0.63, Z=3.0, Annual recruitment occured in two pulses.
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     ..
                         2              3                                    _ _ _ _ _ _ I_'l'EAR _ _ _ _ _ __
                   RELATIV£ AGE (Y.H.RS-Io )

Fig. 3    Otolithes cuuieri             L~=398mm,          K=O.52, Z=1.2, Annual recruitment in two pulses.
                                   .,                 t-
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                                     '"     '"   U)   III                            III
                                                 ~    ... '"           !!!    ~ '"
                                   . ..                   '"                         2     ~
                                                                                               300
        ,...
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        N                                                                                      240
        6
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~
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 •                                                              :; 10
...                                                             ex                                   13
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       5                                                        f;!   5                              ~
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                                        2                                                            o
                    MEAN RELATIVE AGE                                        -----I-YEAR
                                                                                                     ~
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                       { YEARS-to)                                                                   rn
                                                                                               •
      Fig. 4 : Johnieops vogleri L~=345mm, K=O.72, Z=3.2, Annual recruitment in two pulses.          ~
                                                                                                     ~
                                                                                                    ....
                                                                                                    '"


               I
                                                                                       180 :L
               6
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                •                                                                      120 ~
               !
                                                                                       60 -'
                                                                                           '"
                                J   F   M   A    hi   J       J   A   S   0   N   0
                                                                                                    ()

                                                      MONTHS                                        ::r:
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      124
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                                    2       3                             I-YEAR---_ _ _ _ _ _ __

                       R!LATIVEAGE (YEARS-'. )


Fig. 5      Johnius macrorhynus L==350mm, K=O.75, Z=4.1, Annual recruitment in one pulse.
                                                     !II    !!!           ...          \L'\                       N
                        ~                   ~                                    ~     ...,       aJ              N           ~
                        ...,                         '"     N             ~                       ....                    ~   10


                                                                                                                                       Z
                                                              b                    P
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                                    -                                                                                                         >
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                                                                                                                                              UJ
                                                                     RE~AT      IV E AGE      (nARS~J



Fig. 6   J ohnieops sina         L~=240mm,           K=O.8, Z=6.56. Th e recruitment pattern could not be resolved.                           w
                                                                                                                                              -
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                                                     51                                                                  o         ~                       ...
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                                   RELATM: AGE (YEARS-ie»


Fig. 7 : Pennahia macrophthalamus L==245mm, K=O.64, Z=2.0. The recruitment in two pulses.
                                       ...                       D       N       on         N        on
                                                                                            ~
                                       8
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                                                                                                                                                  '"
F ig. 8   N emip terus japonicus L~=335mm, K= O.65, Z=2.S. R ecruitment in two p ulses.
                                                                                                                                                  en
                                                                                                                                                  '"
                                                                                                                                                          ....
                                                                                                                                                          en

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                                                                 ....                        Yf                          ~
                                       2             ~           4                                                I-YEAR

                        R[LATI'Jt AGt: (tORS-f.)




Fig. 9 : Nemipterus mesoprion L =;286mm, K;O.71, Z;3.44. R ecru itment                                                                   in two pulses.
                                                                                       ....
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                             ~                                    Ia          !               ~       ~
                                     x i          ~                                    -
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       •                                                                      I-                                       60          ;:j
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                                                                                       ----I-YEAR--------                          t<J
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                         REL.ATIVE AGE (YEARS-t.)

    Fig. 10 : E pinephelus diacanthus L ==502mm , K=O. 61, Z =l.S. Recruitmen t in two p ul ses.                                   ....
                                                                                                                                   ...,
                                                                                                 ~
                       i !      £      i    ~   •
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                                                                                     ,00
                          r                                  ...I   f'   •               Z
                                                                                     240 2
                                           .J        •   ~                   j   .         z
             0-                                                     p ~P -
             N
             .        •                                       .        p             110 %
                                                                                           ...
             6            ~   p -p   ~ ~'                F0-                 P       120   ~
              •
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             II:                                                                     60 -'
                              ~
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Fig. 11 : Priacanthus h a mrur L==345mm, K=O.66, Z=2.5. Recruitment occured in two pulses.
                               Q)             ,...       '<T               OJ                                                 00
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                            RELATIVE AGE (YEARS- to)                                                                                                             to
                                                                                                                                                                 rn



Fig. 12            Sa ll rida tu mbil L oo;600 mm, K;O.5 1, Z;2.80. R ecruitment in s ingle pul..e.                                                              "'
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                                         2                           5         6
                                                                                                                       I-YEAR·
                                                    , •
                                        RELATIVE             AGE (YEARS-'.)


Fig. 13   SaUl-ida undosquamis L==412mm, K=O.51, Z=2.52. Recruitment pattern could not be resolved.
                                                                                            N
                                     o   ...       '<t   If)
                                                                              o    o    o
                                !D
                                '"                       '"    o              10            ~
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                 CD                                                                                    z:         1
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                                                                                                 180   %
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                                                                                                 120   i
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                                                                        20                                        13
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                                RELATIVE AOE(YEARS-Io)                                 1- YE AR - - - - - - - -

                Harpodon nehereus L==413mm, K=O.73, Z=3.l. Recruitment in two distinct pulses.                    ~
Fig. 14                                                                                                           '"
                          >-       n          N        N                                        ~      $    :g
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                                                                                        '"      >-     N         &       I:
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                                                                                                _________   IY[A,RR~   ______________
                              RELA"f'V£       AGE ( YEARS-I. )


Fig. 15
                Trachysuru s caelatus                 L~ ~              521mm, K = 0.68, Z = 3.5. R ecruitment in two pulses.
                                                                                                       (II                                N
                                            III
                                            .,      It'
                                                    .,           o    .
                                                                      .,                               .,             ~      ~
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                                                                                                                  •                                  60
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                                            J       r            ...     A           ....        J     J              A     5       o     N    o                          ~
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                                                                                                                                                                          -~
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                       '0                                                                                      ....
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                                                2       3            •       5              6                               - - - - - '-YEAR                              '"
                                       R£ LATlvE M:iE CY[ARSo,o)


Fig.16   Trachysurus thalassinus                    L~      = 850mm,                         K   = 0.24,        Z         = 1.5.    Recruitment in two distinct pulses.   co
                                                                                                                                                                          '"
                         ....         10                      II)   o      .,         C1>
                                N
                                .,                                  OIl               .
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                                                                          1-15
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          3
                                              •
                                     2                    3

                       RELATIVE      AGf (YEARS-to                                              - - 1-     YEAR...:....-.,..--_ _ __

Fig. 17    Osteogeneiosus militarias L~ = 600mm, K = 0.65, Z = 5.0. Recruitment in two pUlses.
          ClIO                  1ft                                 II>
          N
                                                          on                  10   o
          ., • ., ., •                N                   N
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                                          N ON T~S                                                               [;J
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                              RELATIVE     AGE (YEARS_! \
                                                       o
Fig. 18          Coilia dussumieri L~ = 230mm, K                = 1.2,    Z   = 3.6.    Recruitment pattern of
                 this species could not be resal ued.                                                            en
                                                                                                                 '"
                                                                                                                                ,..                  o
                                                                                                                                              II>    N
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                                           :3        4
                                                                                                             - - - - -- I-YEAR -                            ------

                        RELATIVE AGE ( 'I'[ARS-Io )



Fig. 19       T rich i urus lep turus L~             = 1480mm,                    K       = 0.4,             Z    = 2.62,       R ecruitment occured in two pulses.
                                                                                                                              ,.
                                                                                                                     240F.
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                                                                               MONTHS                                               [;l
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                                                                                     ~---            One year
                                      R elalive age

Fig. 20    Loligo duvaucelii. L~ ~ 343mm, K ~ 0.49, Z ~ 2.09. Recruitment occured in two pulses.                                   -.J
                                                                                                                                   '"
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        I                       i:3.,                                              o I ,=-:::: .                                           ./             ---- b
          f)                   2   lelotive o',le                                                        - - - - One yeor                                   ---1



               Fig, 21    Sepia aculeata, L~ = 297mm, K = 0.56, Z = 3.4. Recruitment in two pulses.
                                     11'1                0                                      ...            N
                                                     ~                           ~              0        :lI   ...
                                                                                                               .,
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                  RELATIVE            AGE - I.                                                          I YEAR

                                 Fig, 22 : Parapeneopsis stylifera (Female) L= ; 140,8mm, K; 2,15,
                                                                                                                                '"
                                                                                                                                '"
                                           Z = 7.6. Recruitlnent occured in two pulses.
                                0     ...                                      ;;;
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                                      ~              !!!   on  !I!             ~               ~
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     61        •
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              RELATIVE         AGE - I.                                                              1- YE AR


          Fig. 23 : Parapeneopsis stylifem (Male) L=                                       =    l19.2mm, K       =     1.45,
                         7: = In , 7R.        Rr>f'rll;fI11r>nf nr'rur,.,r/ ;'1 hun Jlfll .~r .~
                                    J:       ~              i      .
                                                                   iii   s·   .. ..
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                                                                                                 ID
                            !       ..   i ... $
                                               •                         •
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                                                                                                      180

                       ~
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                      RELATIVE AGE-'.                                             1- YEAR

           Fig. 24    Metapenaeus monoceros (Female) L~ = 219.2mm, K = 1.4,                                     co
                                                                                                                ~
                      Z = 3.82. Recruitment in two pulses.
                             ~                                          ~             ~    .                ~                     w
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                                                                                                            I
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                                                   MONTHS
                                                                                                                              (')




                                                                      300
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Fig. 25           jl,;Ietap enaeus m onoceros (Male) L =                            = 180.5mm,          K   = 1.35,
                  Z = 4 .5. R ecr uitmen t in on e p u lse.
                                   t!               ~         It                            j:       .,     •
                                                                                                            .          S
                                   •        ~       .,        <II       e       , s.,
                                                                                •           •        on
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                                        J       F        II         A   M         J J   J        A        s   o    N        o
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      16
                                                                                zo
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      104                                                               ..  z                                                               §
-.,   12                                                                ...
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                    RELA liVE AGE - 10                                               -----------1 · YEAR----------------___

      Fig. 26                   M etapenaeus affinis (Female) L = = 188.8mm, K = 1.47,
                                Z = 6.78. R ecruitment pattern could not be resolved
                                                                                                                                             '"
                                                                                                                                             '"
                                       ..,.   N               .,        0                                 0
                                                                                           OJ
                          12                      ~
                                                              ., ., ... .,
                                                              ..,        on                               N
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                                                                                                                     120
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                                                                                                 p)               60
               ~
                                                                                                                     40
                                                                                                                     20
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                              J        F      .   A       M   J        J           A   S   0      N       0
                                                  MONTHS




                                                                                                                               o
     15
                                                                              20
                                                                                                                               !
                                                                                                                               ~
     13                                                            >-         I~                                               ~
                                                                   Z
                                                                   \oJ
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0                         "                                        a:
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                                                                   a:
     7                                                                         ~
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                                                      2
                   RE LA TillE AGE -I.                                                          1- YEAR

     Fig. 27          M"etapenaeus affinis (Male) L~ = 151.55mm, K                                    = 1. 5,    Z   = 4 .6.
                      Recruitment pattern could' not be resolved.
                                     Il    $I   ~           •          ~    ~   N
                                                                                ... ... g ...
                                     OJ)        OJ)   on    •               N   on  ...       I'-
                               ~           on
                                                                                    '" ... en
                                                      *     • •
                                                                                                    120        C'l

                                                                                                    '00        1:5
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                        c                                                                                 %    o
                                                                                                    40 ...
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                                                                                                        -'
                                                                                                    20 ....

                                                                                        N                       ~
                                J     f    M    II    hi    J    J
                                                           MON·THS
                                                                            A   s   o         o
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          o                       I                                                 ,- YEAR
                RELATIVE AGE (YEARS-'.)
                                                                                                                      co
              Fig. 28          Solenocera crassicornts (Female) L~ = 139mm, K = 2.0,                                  en
                               Z = 10. 36. Recruitment occured in two distinct pulses.
                                                                                                    '"
                                                                                                    '"
                                                                                               r-
                                                                                               z
                                                                                               '"
                                                                                               -4
                                                                                               "

                             1~ 1f                rr                                 ~   f    ~i
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                                                             MONTHS                                  ~

                                                             30
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                                                             7'~




          o
                MEAN RELATIVE AGl(YEARS-to I                       ---ONE   yEAA------

              Fig. 29            Solenocera crassicorms (Male) L~ : 92mm. K : 1.5. Z : 6.B.
                                  Recruitlnent occured in one pulse.
                       GROWTH, MORTALITY, RECRUITMENT AND MSY OF RESOURCES                                                                                                                            37




                                                                                                                                                     RELATIVE y .... /R
                        RELATIVE Yw/R
              0                                             0                                                                              0                     0                              0
                                 0            0
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                            RELATIVE              aIR                                                                                                  RELATIVEB/R




   Fig. 30 : Relative yield per recruit (YwIR) and biomass per recruit (BIR)
              against exploitation rate.
38                            CHAKRABORTY ET AL.

ACKNOWLEDGEMENT                          Gayanilo, F .C. Jr., Soriano, M. and
                                           Pauly D. 1988. A draft guide to
    The authors are grateful to
                                           the COMPLEAT ELEFAN.
Dr.P.S.B.R. James, Director,
                                           ICLARM Softwa re Project 2 : 65
C.M.F.R.I.,     Cochin    for    the
                                           p and 10 diskettes (5.25 inches,
encouragement provided during the
                                           360 K ).
course of investigation. We are
thankful to S/Shri J.D. Sarang,          George, P.C., Antony Raja, B.T.
B .B.Chavan, A.D. Sawant, A.Y.             and George, K.C., 1978. Fishery
M e stry and Thakurdas for the             resources of the Indian Exclusive
assistance provided in the field and       Zone . Souvenir Silver Jubilee,
the laboratory.                            IFP, Cochin.
                                         Gulland, J.A. 1971. Th e fish
                                           resources of the oceans. W est By
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