Stock assessment of Sprat Sprattus sprattius L. of Bulgarian Black Sea Coast, using Length Cohort Analysis
Daskalov G., Prodanov K.
Dynamique des populations marines Zaragoza : CIHEAM
Cahiers Options Méditerranéennes; n. 10 1995
pages 71-72
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--- D askalov G., Prodanov K. Stock assessmen t of Sprat Sprattu s sprattiu s L. of B u lgarian B lack Sea Coast, u sin g Len gth Coh ort An alysis. Dynamique des populations marines . Zaragoza : CIHEAM, 1995. p. 71-72 (Cahiers Options Méditerranéennes; n. 10)
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Stock assessment of Sprat Sprattus sprattius off Bulgarian Black Sea Coast, Cohort Analysis
and
of
attempt is made, to evaluate the dynamics of abundance and of
stock by means of 1981).
Length composition data catches 3
the and the to be
steady state conditions.
was et
1990), an the analysis was employed.
was also possible to estimate the 1970-92,
statistics and
available. Sensitivity analysis was taken into account, the optimal choice of
was not. possible to the of
lack of data the studied. Even though, such estimates 1977-93 this vol.) we did not
by JONES( 1990) gives closest
studies 1993).
Table. A. used in anlysis
at length 7.0cm in 106
l3z o+-
mean biomass at leqgtli 7.0cm and in tons,
o+
B.
years 45-49 ,
B 7 m /H p+
56-59
48059.6 1.2
60-62
Lou=16cm( 1977-92) the k
k = 1 n ( ~ 0 0 - ~ ~ ) / ~ 0 0 - 1 2 ) ) was found:
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and 2 (TabZe,A).
length was chosen to be 12cm(750/aLoo).
-
0.95 1975-92 and 1.2 1945-74
-
the last one, the thein that 1966, and
1985). to
(1993). catches(C) and fishing
to F+ values
1975
200000 40000
20000 c
o O
mean in tons(co1umns) and catches(C: scalc) with line:
The evolution of the stock state could be devised into main the up to mid ~ O ' S , stock
an the
abundance 'is fion1 the combination of stable and at the end of 5O's.The second stage is
by a of stock biomass and mid 70's to
mid 80's. Such an "explosion" could be the extinction of top in late 60's and ?O's, and the of the sea level due to
of two explains the, in
the late 70's. the beginning, the high abundance ita of the base, but soon ,the outstanding
like hypoxia and of gelatinous
megaloplancton, which is feeding on fish eggs and and
fish on food. The is obviously the too .high at the
same time when the standing stock is 1945-92
et A, 1990. lOl(4): 124pp.
G. 1993 de
and 1985. 135pp.
JONES, 1981, 57pp.
JONES, 1990, 46: 130-139
STOYANOV, S.,1966, Varna, 6:21-48
72
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