STUDIES ON SAURIDA UNDOSQUAMIS (RICHARDSON)

STUDIES ON SAURIDA UNDOSQUAMIS (RICHARDSON)
FROM THE GULF OF SUEZ
lUonthly Peculiarities of Gonads
BY
A. F. A. LUIF AND TH. S. SHENOUDA

1. INTRODUCTION
Fishes live under adverse ecological condition and they vary greatly
in the character of their spawing. Thus, while some fishes lay their eggs in
the summer, others spawn in winter. Moreover, some species have usually
a short spawning season while this becomes longer in some others. Some
female usually shed the eggs.in a single batch in the spawning season along
one sexual cycle but still others deliver a number ‘of batches (Kazansky, 1949,
Latif, 1966, etc.)
Furthermore, fecundity designated as the number of egg discharged in
the oviparous species is variable in the different species as well as in
the different populations Iiving under diffferent environmental conditions
or i\n different years (Nikolsky, 1965). Besides, the fecundity being
a specie peculiarity responsible for preservatior of species through the
different years, We find that fecundity is closely connected with the
characters of species. Thus, the species, guarding or protecting the eg-rs
are less fecund than the species not doing SQ. In other words, the
smaller i the degree of mortality of individuals of a species, the less is
their fecundity. Among oviparous fishes, species laying pelagie eggs
are more productive th an those discharging demersal eggs. Besides, the
extreme condition of protecting the eggs is found in the Tiviparous or
ovoviviviparous eggs where few individuals are delivered.
It is well-kown thart the different species of fishes attain sexual maturity at different ages. Thus, some fishes as the gobiids Apliyra and
Crystallogobius mature before reaching an age of one year. The white
sturgeon Huso lutso L matures, at at an age of 15 – 20 years. In between these
two extremes, lie other species of fishes. Besides, the 01100tof sexual
maturity of one and the same species varies from one region to another.
Thus, the roach in Finland matures art an age of 5 – 6 years, in cetnral
Europe at 4 – 5 years and in southern Europe, at 3 years (Nikolsky, 1963).
Besides, the males and females of one species may become sexally
mature at different agess. Thus, males reach sexual maturity at U
years of age in Acipenser [uloescens, at 7 – 9′ years in A. sturio, at 8 – 14
years in A. guldenstadii, at 3 – 7 years in A. baeri and at 12 – 14 years
in Huso huso. The females of these species attain sexual maturity at ages
of 23, 13 . 20, 12 • 14, 5 – 12 and 16 – 18 years respectively (Roussow,
1957). These data. besides. refer to the fact that the spec-ies of one
genu!’ may he sexually mature at different ages