Categories
vol-1AGE AND GROWTH STUDIES ON
SARDINELLA MADERENSIS LOWE AND SARDINELLA AURITA
CUV. and VAL. FROM THE MEDITERRANEAN SEA
AT ALEXANDRIA (U.A.R.)
By
A.M. EL-MAGRRABY G.A. BOTROS
Oceanography Dept., Alexandria University
and
I.A.M. SOLIMAN
Institut of Oceanography and Fisheries, Alexandria
INTRODUCTION
The Sardine waf; among the most important fishes contributing to the Egyp r tian Mediterranean fisheries. Prior to 1966, huge quantities of Nile flood water
was annually disobarged to the sea tbrough Rosetta and Damietta mouths of
the Nile during the period from August to November. The fertilizing effect of
the Nile flood water initiated the developmeot of luxuriant phytoplankton, blooming off the Nile delta during autumn months.
The Sardine fish used to be attracted in big shoals to this region to feed,
thus becoming vulnerable to the fishermen’s gill-nets. The landings of tbis fish
during the autumn season varied between 6000 and 8000 tons, or approximately
40-50 percent of the total catch from the Mediterranean fisheries of Egypt.
Since 1966, tbis condition no longer exists as a result of the construction of
the Aswan High Dam and the storage of all the flood water infront of the dam.
Tbe two species contributing to those oatclJes, namely Sardinela maderensis
Lowe and Sardinella aurita Ouv. & Val., are however fished in small quantities
througbout the year by tbe shore – seines, particularly in summer. The summer
catches consist of maturing fish whose gonads are ripening in preparation for
spawning. As a matter offact, a clear contrast in the condition of the fish existed
between the fatty well-fed fish of autumn and the emaciated fish of summer.
This paper embraces the results of a study on the age and rate of growth
of the two species. The study of age was based on reading winter annuli and
growth zones on the scales and expressing them in terms of fish length.
Sucb a study was previously carried out, but not in detail, by EI-Maghraby
(1960) and Nassif (1961). The present wotk could be considered as the first
comprebensive study on this subject on these two species in Egypt.
A study of the growth history of fish as recorded on their scales bas been
long aplied by fishery biologists, Hoffbauer (1899); Walter (1901); Dahl (1907),
1909 and 1910-; Lea (1910) ; Taylor (1916) ; Van Oosten (1929); Graham (1929)
and others.
Lea (1910) was however the first to modify the basis of age determination
and to introduce a new approach in his growth studies on the Olupeid fish Clupea
harengus (herring)’ Since then, his procedure bas been widely adopted in fishery
biology investigations.
The growth studis of the two species of Sardinella were attempted on Mediter·
ranean samples by Fage (1920); Navarro (1952); Dieuzeide (1950) ; Ananaides
(1951); Dieuzeide and Roland (1957); Ben-Tuvia (1960); EI-Maghraby (1960)
and NasEif (1961).
Growth studies on the two species were also done in West Africa by Postel
(1955) and 1960) and Rossignol (1955).
