الفهرس 
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Abstract
Family Sparidae represent one of the important families in the Egyptian sector of the Red Sea and Acanthopagrus bifasciatus is member of this family which are among the most valuable and highly priced fish species in Egypt. The present work has been suggested due to the rarity of biological, population dynamics, stock assessment and fisheries studies with respect to Acanthopagrus bifasciatus from the Red Sea, Egypt.
The results of the present work can be summarized in the following points:
1. Identification of fish stock
Identification of the stock of Acanthopagrus bifasciatus by: a- Morphometrics and meristics, b- Scale characteristics.
a. Morphometrics and meristics.
Morphometrics, meristics and the type of allometry (i.e isometry, negative allometry and positive allometry) were estimated for Acanthopagrus bifasciatus.
Discrimination between sexes of Acanthopagrus bifasciatus was possible by using certain morphometric indices. The type of allometry in each of males and females of Acanthopagrus bifasciatus was estimated according to the bivariate concept. No sexual dimorphism was observed in the meristics of Acanthopagrus bifasciatus.
b. Scale characteristics
The scale characteristics of Acanthopagrus bifasciatus were studied in terms of morphometry and Scanning electron Microscopic techniques.
A wide spectrum of size-free intraspecific variations between different body regions was recorded in Acanthopagrus bifasciatus in terms of scale morphometric indices. The scale characters included the overall form of the scales, shape of the first circuli, form of circuli, the outer lateral and inner lateral circuli and granulations of caudal field. Moreover, the forms of the lateral line canal were studied.
2. Fishery Statistics
There are main seven fishing landing sites along the Red Sea; they are from north to south: Ataka, Hurghada, Safaga, Qusier, Baranies, Shalateen and Abu-Ramad. Baranies fishing harbor is considered the principal fishing port along the proper Red Sea where about 53.22% of the total landings comes from it, followed by Hurghada (20.72%), Qusier (9.48%), Shalateen (6.72%), Safaga (3.44%) and Abu-Ramad (2.55%) and then Ataka (2%).
The annual Sparidae catch caught from the Egyptian Red Sea fluctuated between a maximum value of 821 ton (representing 1.75 % of the total Red Sea) during 2007 and a minimum value of 210 ton (representing 0.44 %) during 2008. During the investigation period, Acanthopagrus bifasciatus was the most abundant species in the total Sparidae fishes catch but it is not represented in General Authority for Fish Resources Development (GAFRD).
3. Biological and dynamical studies
Age of Acanthopagrus bifasciatus was determined and the maximum life span was 9 years old. The relationship between (TL) and scale radius (S) was found to be linear with high correlation (R2 = 0.95). Such relationship was described by the following equation:
Males: TL = 1.78 S - 5.26
Females: TL = 1.77 S - 5.14
Combined sexes: TL = 1.78 S - 5.20
Accordingly, the equations used in back calculation were found to be as the following:
Males: TLn = Sn/S*(TL – 5.26) - 5.26
Females: TLn = Sn/S*(TL – 5.14) - 5.14
Combined sexes: TLn = Sn/S*(TL – 5.20) - 5.20
The length–length relationships of Acanthopagrus bifasciatus through the whole period of investigation were described as the following:
Males:
TL = 1.18*SL + 2.54 R² = 0.99
TL = 1.06*FL + 1.08 R² = 0.99
FL = 1.11*SL + 1.40 R² = 0.99
Females:
TL = 1.18*SL + 2.38 R² = 0.99
TL = 1.05*FL + 1.28 R² = 0.99
FL = 1.12*SL + 1.08 R² = 0.99
Combined sexes:
TL = 1.18*SL + 2.58 R² = 0.99
TL = 1.06*FL + 1.19 R² = 0.99
FL = 1.11*SL + 1.34 R² = 0.99
The growth in weight of Acanthopagrus bifasciatus was isometric and length - weight equation was best described by the power function equation. It is represented by the following equations:
Males W = 0.0192 TL2.989
Females W = 0.0232 TL2.942
Combined sexes W = 0.0204 TL2.974
The lowest value of Kn was 0.99 recorded in May and September for males and in September and October for combined sexes; while the highest value of Kn was recorded in January for combined sexes and females (1.01 and 1.03 respectively).
Growth in length
The growth rate in length of Acanthopagrus bifasciatus fishes reaches its maximum value 24.6 cm (43.85%) by the end of the second year of life, after that gradual decrease in the annual increment with further increase in age was observed.
The growth rate in weight was much slower during the second year of life for Acanthopagrus bifasciatus then increased to reach its maximum rate at the end of the sixth year of life then decreased with the increasing in age.
The von Bertalanffy growth in length equation for Acanthopagrus bifasciatus is:
Lt= 65.62 [1- e-0.21(t+0.101)]
Accordingly, The von Bertalanffy growth formula for growth in weight is:
Wt = 5170.06 (1 - e -0.21 (t +0.101)) 2.974
The value obtained for the computed growth performance index (Ø’) for Acanthopagrus bifasciatus was 2.96.
The estimated Lc = 25.31 cm TL, Tc = 2.22 year, Lr = 17 cm, Tr = 1.33 year, Lm = 35.8 and Tm = 3.65 year for combined sexes of Acanthopagrus bifasciatus.
The mean total mortality (Z) was 1.99/year, the mean value of natural mortality (M) was 0.46, the mean value of fishing mortality (F) was F= 1.53/ year and the value of exploited rate (E) was 0.77 for combined sexes of Acanthopagrus bifasciatus. The high values of both fishing mortality coefficient and exploitation rate reflect the high level of exploitation of Acanthopagrus bifasciatus from Red Sea, Egypt.
Food and feeding habits
The food and feeding habits of Acanthopagrus bifasciatus from Red Sea, Egypt were studied to know its feeding behavior in relation to sex, length and season as well as its preference for food items. The results indicated that Acanthopagrus bifasciatus feeds on a variety of food materials mainly Mollusks (gastropods, bivalves and chitons), crustaceans (hermit crabs, crabs and eggs of hermit crab), fish scales, cnidarians (soft corals), Echinodermata as well as food remains. The feeding intensity showed its highest value during spring (76.74%) followed by winter (73.58%), while the lowest value was recorded during summer (57.14%). Acanthopagrus bifasciatus shifted their fullness index as they grow in length where the lowest value of this index was recorded for a length group 17–25 cm TL and the highest value was recorded for a length group 36–45 cm TL.
The ability of Acanthopagrus bifasciatus to feed on a number of different trophic levels coupled with the potential for fast growth makes this species a promising candidate for commercial culture. As the species is widely used as human food throughout the area in which it occurs, it could easily be incorporated into locally operated polyculture systems.
Reproduction
Monthly pattern of gonadal activity showed occurrence of five maturity stages for females and males; from stage I up to stage V. The overall sex ratio was estimated as M: F (1.5:1). The spawning season extends from January to April and December with a highest GSI value in December. The absolute fecundity (F) of Acanthopagrus bifasciatus was varied from 737674 to 1741666 eggs/ female/ spawn, showing considerable variations among individuals. The relationship between fecundity and both total length (TL) and total weight (W) were best fit by the following linear equations:
F = 67803* TL -2 E+6 R2 = 0.92
F = 245791 + 473.23* W R2 = 0.82
4. Fisheries management
For evaluating and managing Acanthopagrus bifasciatus fishery in Egyptian Red Sea, yield per recruit model was used. The results showed that:
• The current yield per recruit of Acanthopagrus bifasciatus equal 242.71 g corresponding to fishing mortality coefficient equal 1.53/y.
• The maximum yield per recruit was equal to 250.56g. For achieving this yield the fishing mortality coefficient should be reduced by about 48%.
• The increase of age at the first capture can be associated with the increase of the maximum yield per recruit.