الفهرس 
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Abstract
Egypt has a long coastline from north Mediterranean Sea and from east Red Sea which has two Gulfs (Aqaba & Suez Gulf), most mullet found in Suez Gulf region due to its rich fauna. Liza carinata member of mullet belonging to family Mugilidae, which has a great commercial value and great demand in Egypt.
Suez Bay is one of the most important commercial sites in mullet production in Egypt. Although Egypt was known as one of the highest productive countries of mullets, (ELGamal, 2013), a decline of the production has been recorded recently from 33.5% in 2003 (GAFRD, 2004), to 11.3% of total fish production in 2011 (GAFRD, 2011) the following data represented by the general authority of fisheries and resources development in (2013-2014) book showing the production of mullet in the Red Sea during the recent years and show how it was decreased:
Year
2006
2007
0208
0222
0210
0211
2012
Production (ton)
4011
1125
1159
922
339
343
226
.
The rapidly growing aquaculture industry in Egypt depends largely on mullet production, which accounted for 29 %of the production in 2005 and 48 %of the market value of cultured fish (GAFRD, 2006). This activity depending on fry collection. Increasing rate of seed (fry) collection was considered as a major
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threat to fisheries authority due to its great influence on decreasing the stock recruitment and the production of L. carinata, at which EL-Gamal (2011) recorded in 2009 that 99% of collected fries belonging to mullet which require a brilliant solution to face this problem and increase the production of L. carinata by induced spawning. Knowledge about L. carinata reproductive biology as well as sex hormones pattern is urgently required.
So, this study was carried out to fill gabs of information about reproductive biology, histology and sex hormonal pattern of L. carinata and use the data to help the induced spawning of the species in Suez Bay.
The fresh samples of L. carinata were collected from November 2012 to October 2013 and transferred to the laboratories of the National Institute of Oceanography and Fisheries, in Suez. Length and weight was taken to the nearest 0.1cm and 0.01g, respectively for the biological studies. Gonads and liver weighted to the neasest 0.01g for measuring the GSI and HSI. Gonads of males and females were fixed in Bouin solution for histological examination, stained with eosin and haematoxylin and examined by Leica DM500 microscope equipped with camera. Fish were anaesthetized and blood samples were taken from the caudal vessels by using heparinized disposable syringes. Sample was centrifuged for 10 min at 3000 rpm and the plasma was stored at -45 0C until steroid analysis. Monthly plasma levels of 17β-Estradiol (E2) and Testosteron (T) hormones were measured for both male and female Liza carinata by radioimmunoassay using the procedure described by (Rinchard et al, 1993)
First: The reproductive biology
(1) Sex ratio for L.carinata collected in this study was 354:364 females: males, respectively.
(2) The total length of female L.carinata ranged from 10.8cm to 18.2cm but for males it was ranged from 10.5cm to 17.3cm.
(3) The length-weight relationship of both sex of L.carinata can be represented by the following equation:
Female L.carinata W= 0.012 L2.946
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Male L.carinata W= 0.034 L2.565
where W is the total weight in gram and L is the total length in cm, the computed growth performance index for females L.carinata in Suez Bay were 2.946 and 2.569 for males.
(4) Length at first sexual maturity (L50) was estimated for females and males 14.3cm and 12.5cm respectively, at which the first spawning occurred and 50% of the population becomes matured.
(5) The evaluated condition factor (K) showed that females and males of L.carinata reached the highest K value at 1.23 – 1.21 in September and August, respectively but the lowest K value in females occurred in April 0.88 and in January 0.97 for males.
(6) Gonado-somatic index (GSI) was estimated for both sex of L.carinata by equation:
GSI % = (Wg/ Wgut ) × 100
Wg = Weight of gonads, Wgut = gutted weight
Values of GSI varied from 0.921 to 8.883 for females and from 0.039 to 5.788 for males. GSI recorded the highest peak for both sexes in December 2012 but the lowest peak recorded in March and February for females and males, respectively.
L.carinata showed prolonged spawning period extended from November 2012 to March 2013. It is evident that the Suez Bay considered as a perfect region for L.carinata to live in.
(7) On the other hand the hepato-somatic index (HSI) for both sexes was evaluated by the following equation:
HSI % = (WL/ Wgut) × 100
WL = Weight of liver, Wgut = gutted weight
Values of males and females HSI was paralleled to each other showed the highest peak in September with values 5.034 and 4.414 for females and males, respectively
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and the lowest values recoded in October and December at which the highest values of GSI were estimated, it gives another sure about the spawning time of L.carinata.
(8) The macroscopic features of ovaries and testes of L.carinata during the study period was recorded using the scale used by (Abou-seedo and Stephen, 2004) showing seven maturity stages for males and females called (Immature, Immature & Recovering, Developing, Maturing, Mature, Spawning and Spent), these stages distributed according to the months and level of maturity.
(9) The absolute fecundity of L.carinata was ranged from 24,500 to 115,258 oocyte, fecundity increase with increasing of length and weight, this relationship between fecundity with total length and weight were evaluated by using the equation:
F= 0.5908 L4.1444 R= 0.8903
Where, F is fecundity, L is the total length (cm) of fish, while the relation of fecundity with total weight measured using the equation:
F= 313.8 W1.354 R= 0.8286
where F is fecundity, W is the total weight of fish (gm), this result represented high correlation of length with fecundity more than weight.
Second: The histological studies of L.carinata from Suez Bay improved the macroscopic result about the maturity stages; oogenesis (oocyte maturation) was divided into two phases:
A- First growth phase: which included
(i) chromatin – nucleolus stage.
(ii) Early & late Perinucleolus stage.
B- Second growth phase: which included
(i) Yolk vesicle stage.
(ii) Yolk stages which included (primary, secondary and tertiary yolk stage).
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(iii) Ripe stage.
The histological maturity stages of female L.carinata were the same as the macroscopic divided into seven stages (Immature: appeared from February till August, Immature &Recovery: found from March to September, Developing: recorded throughout the investigation especially in September and October, Maturing: observed from October to November, Mature: appeared from November to December, Spawning: recorded from November to March and Spent: observed from January to April.
The spermatogenesis happen as a successive process producing cells which increase in number but decrease in size as spermatogonia giving spermatocytes (primary and secondary), then give spermatids and sperms as an end product.
Maturity stages of testes were the same as female divided into seven stages with slight differences (Immature: appeared from February till August, Immature &Recovery: found throughout the study especially at March to April, Developing: recorded throughout the investigation especially in August and September, Maturing: observed from September to October, Mature: appeared from November and December, Spawning: recorded from November to March and Spent: observed from December to April.
Third: The sex hormones studies (17β-Estradiol & Testosterone) were estimated for both females and males of L.carinata during the study period and found that:
Females17β-Estradiol ranged from 0.120 to 0.122ng/ml, recorded the highest level in maturing stage in November, while the Testosterone level ranged from 4.71 to
5279ng/ml showing the highest peak in December 30.5ng/ml where the ovary became mature, and the lowest value recorded in February in spawning and spent stage.
Male 17β-Estradiol ranged from 0.0004ng/ml to 0.0009ng/ml the peak of Estradiol recorded in November, while the steady value 0.001ng/ml recorded from January to March. Testosterone in males L.carinata ranged from 5273 to 727.ng/ml the peaked value was recorded in December at high maturity stage and the lowest value recorded in the spawning and spent stage in January. The
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sex steroid hormones in female and male L.carinata from Suez Bay were compared with the GSI levels to indicate the relation of gonads maturity with the sex hormones concentration.
Conclusion and Recommendations:
The target way to face the continuous decreasing in mullet production especially for L.carinata in Egypt by the following:
1- Make use of the present study data to induced spawning of L .carinata to provide farms by fry without affecting the stock recruitment in nature.
2- Legislated new rules to prevent illegal collection of fry.
3- The government may adopt a policy of subsidizing hatchery production of L.carinata seed followed by a ban on wild seed fisheries to encourage hatchery development.
4- Biological studies should be in consideration to choose the fishing pan period after a complete maturation and spawning of L.carinata in March or April not as applied in May.
5- Variation of fishing regions year after year and closed catch in Suez Bay for three years to enhance the production and spawning of the fish.
6- Suez Bay considered as an excellent environment for L.carinata fry so the government should save this area from sweeping to build new tourist resorts.
7-Suez Bay also surrounded by large number of factories which polluted the water and affected the production of the fish, so this requires restricted rules from the government to preserve the area from pollution.