Summary:
For this thesis we used a total of 199 individuals of the family of Rajidae and
1 of the family Dasyatidae, which are captured from different parts of the
marine area of Greece at different depths. In the laboratory the fish got
thawed, washed and become sex determination-if-clear sexual dimorphism. There
were realized measurements of total weight (RW) and of linear dimensions of the
characteristics of the fish's body, such as the physical characteristics, total
length (TL ), the width and length of the tray, the diameter of the eye etc.
For the measurements we used tools such as ruler & precision scale. There were
also measured the length and weight of certain liver, stomach, intestine and
gonads and determined gonadosomatic index (GSI). Also visual observation of the
gonads and determination of step gonadal maturity were proceeded.As for the
sizes, the largest size of Rajidae family was male with a total length 725mm
total weight of 2148g and the smallest was also male with a total length of
160mm and a total weight of 12g.The largest average length and the average
weight caught is the kind R.radula.
In female specie R.clavata, the total length ranged from 160 to 650mm and in
males from 160 to 725mm. The weight in females ranged from 11 to 1921g and 12
to 2148g in males.
In females of the species R.asterias , the overall length ranged from 148 to
385mm while in the males ranged from 254 to 520mm. The weight in females ranged
from 8 to 260g and from 46g to males.
In females of R.melitensis, the total length ranged from 203 to 250mm, while in
males from 213 to 291mm. The weight in females ranged from 20 to 55g and from
27 to 99g in males.
In females of R.brachyura, the total length ranged from 229 to 320mm while in
males from 222 to 515mm. The weight in females ranged from 40 to 138g and from
31 to 688g in males.
In females of R.montagui, the total length ranged from 360 to 502mm, while in
males of 350 to 655mm. The weight in females ranged from 220 to 710g and from
160 to 1632g in males.
In females of R.radula, the total length ranged from 550 to 610mm while in the
males of 415 to 565mm. The weight in females ranged from 1241 to 1592g and 380
to 1290g in males.
Applying regression analysis there were correlated gonadosomatic (GSI) and
hepatosomatic (HSI) ratio to the total length (TL) and the width od disk(DW) of
species separately. Regarding the hepatosomatic index is increased in relation
to the total length of individuals, but there were large males with lower
prices. In more mature stage, the average value of the index increases, as well
as the maximum and minimum value.
As for the graphs on the frequency of the diameter of oocytes, an increased
incidence of rates was observed mainly in the middle and as we climb ripe fish
observed shift to the right, towards longer wavelengths eggs. Finally, there
was a relatively good correlation between weight and diameter of eggs .
