Rapp. Comm. int. Mer Médit., 36,2001
278
Pandora,Pagellus erythrinus(Sparidae, Percoidei) is only economically
interesting species which biology and population dynamics has been studied in
details in the Montenegrin coastal area. Among the others, growth parameters
of this species have been studied too,(1) estimated growth parameters of
Pandora in this area from the data obtained in the period from 1964 to 1965.
These estimates apart, the only data on Pandora’s growth for the Eastern
Adriatic coast are those from the channel of the Middle Adriatic in the period
1957/58 (2). Therefore, the recent results given in this paper can be compared
with these previous data.
Material and methods
Material was collected during the period from May 1997 to May 1999, with
commercial trawlers in depth of 50-300 m. Thirty trawl hauls were analysed in
total. In Boka Kotorska Bay 10 hauls were performed, and 20 at the open sea
(Fig.1). The length and weight of 3201 individuals of Pagellus erythrinuswere
measured. The total weight of analysed individuals was 362.39 kg. Of that num-
ber, 2093 individuals (310.99 kg)
were from Boka Kotorska Bay,
while 1108 individuals (51.4 kg)
have been taken at the open sea.
Collected material was almost
entirely processed on board Total
length (TL), from the peak of
mandible to the stretched ends of
the caudal fin was measured with
the one mm precision. The age of
the fish was determined through
rings on scales taken immediate-
ly above the lateral line. The age
was read with the help of binocu-
lar lens “WILD” that enlarges 25
times. The estimate of growth
parameters in the vo n
B
e
r
t
a l
a n
ffy's function (3,4) is
done with the method of smallest
squares of non-linear functions.
In order to calculate this, programs FISAT (5) and TRAWLAN (6) were used.
The parameters L
8
, K and t
0
are being estimated after the various transforma-
tions, in different ways, based on a long row of data about age (t) and length of
fish (L). The ratio was also calculated (7), as the mass growth in the
function of time (3,4).
Results
The results of estimate of growth parameters are shown in Table 1 as well as
graphically in Figure 2 and Figure 3.Table 2 shows the estimated values of
length-weight ratio (8), growth and maximum weight of individuals, gathered
both through this estimate and the earlier estimates for Boka Kotorska Bay, for
year 1964/65 (1) and the channels of Midlle Adriatic from year 1957/58 (2).
Discussion
Estimation of growth parameters by the method of smallest squares of non-
linear functions gave following results: for the Bay L
8
= 37.741, K = 0.162 and
t
o
= -1.227, for the open sea L
8
= 32.752, K = 0.202 and t
o
= -0.568. Rijavec
(1) got following values: for Boka Kotorska Bay L
8
= 30.92 cm, K = 0.239 and
t
o
= -1.639. The results of present estimate show larger values of the asymptote
for Boka Kotorska Bay L
8
= 37.741, but smaller growth rate K = 0.162, while
t
o
=-1.227. The most probable explanation of this difference is the increase of
trophic base in the bay as well as the increase in this species' biomass.
Therefore, it may be assumed that the intraspecific competition has increased
too, so the individuals grow slower but attain larger final size. The parameters
that indicate the levels of eutrophication (nutrients, oxygen saturation, BOD,
etc.) were not systematically measured in the Boka Kotorska Bay.Therefore, it
is difficult to estimate the time of the beginning of anthropogenic eutrophica-
tion, and to assess its level. The only reliable indicator of human induced
eutrophication of the Bay is the regular appearance of the summer maximum
instead of usual spring and autumn maxima of phyto and zooplankton (9).
However, until the beginning of seventies, there were no summer maxima of
both phytoplankton (10) and zooplankton (11) in the Adriatic. They appeared
for the first time with the beginning of anthropogenic eutrophication of
Adriatic.It is not possible to compare these data with data from Rijavec (1), as
he does not present data of estimates of growth parameters for the open sea. The
only existing data which may be compared with ours are given for the channel
area of Midlle Adriatic, Zupanovic and Rijavec (2) have compared the material
collected in season 1957/58 and find out that L
8
= 37.88 and K = 0.20. The
value of K in the channel zone of the Midlle Adriatic matches the value of K for
the open sea of Montenegin sea coast, while L
8
matches the value for Boka
Kotorska Bay.These data point to the conclusion that the ecological conditions
of channels in Midlle Adriatic in season 1957/58 were similar to the present
ecological conditions of Boka Kotorska Bay. The discovered diff
e
r
e
n
c
e
between the asymptotes and the temporary growth rates in Boka Kotorska Bay
and the open sea, supports the theoretical hypothesis that, the quicker growth
rate is, the smaller are the asymptotic lengths, means that, K and L
8
. are oppo-
sitely correlated. On the other hand, Zupanovic and Rijavec (2) have find out
that at the relatively high values of temporary growth rate, the asymptote is
large, too. This disagreement with the theory can be explained in two ways. As
the channel area of Midlle Adriatic belongs to the naturally euthrophic zones
(12), while the trawling fishing as well as the other ways of fishing were inten-
sive even then, it is possible that Pandora grew faster due to suitable trophical
conditions on one hand, and the decreased intraspecific competition on the other
hand. The other explanation is, that perhaps those are two different populations
ofPagellus erythrinus, one living in channel area of Midlle Adriatic and other
from Montenegin shelf.The calculated Hohendorf’s index shows that the speci-
mens from the bay have a better growth potential (0.962) than those on the open
sea (0.930). Considering the ecological conditions and the greater amount of
suitable food, the difference in values of this index is clear.The calculated val-
ues of final growth W
8
for the bay are now at 559.95 grams, similar to the val-
ues for channels of Midlle Adriatic 679.74 gr (2). This fitting of values supports
the already explained similarity of ecological conditions in these two areas. On
the other hand, the almost identical values for the open sea now 326.28 gr and
Boka Kotorska Bay 313.84 gr in the period 1964/65 (1) speak in favor of the
smaller trophical base, i. e., insignificant eutrophication of the Bay in previous
period. Nowadays, the value of W
8
for Boka Kotorska Bay is almost twice big-
ger than in the season of 1964/65, and this also points to the intensive anthro-
pogenous eutrophication of Boka Kotorska Bay.
References
1-Rijavec L., 1975. Biology and Dinamics of Pagellus erythrinus(L.) in the Boka Kotorska Bay
and of the Coast of Montenegro (South Adriatic).Studia Marina,8: 3 - 110.
2-ZupanoviC S., Rijavec L., 1980. Biology and population dynamics of Pagellus erythrinus(L.)
in the insular of the Middle Adriatic. Acta Adriat., 21(2): 203-226.
3-Bertalanffy L. von, 1934. Untersuchungen über die Gesetzlichkeiten des Washstums. 1.
Allgemeine Grundlagen der Theorie. Roux’Arch. Entwicklungsmech. Org., 131: 613-653.
4-Bertalanffy L. von, 1938. A quantitave theory of organic growth (inquiries on growth laws. II).
Human Biology, 10(2): 182-213.
5-Gayanilo F.C., Sparre P., Pauly D., 1995. The FAO-ICALRM Stock Assessment Tools (FISAT)
User’s Guide. FAO Computerized Information Series (Fisheries). 8:126p.
6-Regner S., 1999. TRAWLAN - a BASIC package for trawl survey analysis.
7-Hohendorf K., 1966. Discussion der Bertalanffy - Funktionen und ihre Anwandung zur
Characterisierung des Wachstums von Fischen. Keiler Meeresforsch., 22: 70 -97.
8-Joksimovich A., 1999. Length-weight relationship of pandora, Pagellus erythrinus (Linnaeus,
1758), from the Montenegrin shelf. Ichthyologia,31(1): 9-21.
9
-
R
egner D., et al.1999. Zastita i unapre|enje zivotne sredine morskog dobra. E
koloska studija: 38p.
10-Pucher - PetkovicT., 1975. Fitoplankton Kastelanskog zaljeva u odnosu na organsku poluciju.
Pomorski zbornik, 13: 247-256
11-Regner D., 1979. The in?uence of eutrophication on the copepods in the coastal area of Split
(Central Adriatic). Rapp. Comm. int. Mer Médit., 25/26(8): 101-102
12-Buljan M., 1964. Ocjena produktivnosti Jadrana dobijena na temelju njegovih hidrografskih
svojstava.Acta adriat., 11 (4): 35-45
L
max
L
8
GROWTH OF PANDORA, PAGELLUS ERYTHRINUS,FROM THE MONTENEGRIN SHELF
Aleksandar Joksimovich
Institute of Marine Biology, Kotor,Yugoslavia - ajoksim@biokotor.org
Abstract
The growth parameters of Pandora, Pagellus erythrinus(Linaeus, 1758) were estimated for the Montenegrin coastal area, as this is one of
the most important species of trawling fishing. The estimates were made separately for Boka Kotorska Bay and the open sea of Southern
Adriatic.
Keywords: Growth, Teleostei, Montenegrin shelf, South Adriatic
L
8
s.e.c.v.Ks.e.c.v.t
0
s.e.c.v.r
Bay37.7410.4570.01210.1620.00650.0399-1.2270.0979-0.045
0.993
Fig.1.Investigatedarea(Bold
Table 1. Growth parameters of von Bertalannfy's growth function, by
method of estimation of sum smallest squares of non-linear function.
Fig. 2. Graphical explanation of
growth parameters estimated for
Boka Kotorska Bay.
Fig. 3. Graphical explanation of
growth parameters estimated for
W
8
(gr)L
8
(cm)a
b
B.K..Bay 98/99.
559.9537.7410.01462.907
Open sea 98/99.
326.2832.7550.02162.758
B.K.Bay 64/65.
313.8430.920.02202.787
Midlle Adriatic 57/58.679.7437.880.01342.981
Table 2.- The estimatied values of length-wight ratio, growth and maxi-
mal weight of specimens in present and previous research.
