Sex ratio of the false trevaly Lactarius lactarius (Bloch and Schneider)

The sex ratio in Lactarius lactarius at different months and years was studied. Sex ratio data show that males outnumber females in all months except in October. The insignificant difference in the number of individuals of both the sexes during spawning months (January, March, October and November) indicated that males and females congregate during the spawning season. Among the larger specimens, males constituted the minority.

Morphometry, length-weight relationship and biology of Sepia aculeata (d'Orbigny, 1848) from Mumbai coast, India

Seventeen morphometric characters of Sepia aculeata of Mumbai coast have been studied and the relationships of morphometric characters with dorsal mantle length (DML) were established. The characters compared showed a fair to high degree of correlation ('r' 0.63-0.99). Number of arm suckers and shell rings were related with DML. The shell rings also showed high degree of correlation with DML ('r' 0.79-0.95). However, the relationship between arm suckers and DML was not so good ('r' 0.1-0.4). The length-weight relationship is described as W=0.1821336 L sub(2.801102). Food and feeding analysis confirm the carnivorous feeding behaviour of the species. Mature females found in all months indicate that it has prolonged spawning season with two peaks, september and march-april. Absolute fecundity ranged from 214 to 4143 eggs.

Milt quality determination of a critically endangered fish, olive barb (Puntius sarana, Ham.) in Bangladesh

The present study was aimed to evaluate the characteristics of the olive barb sperm. Milt was collected fortnightly from 49 male fish (mean weight 90.8 g and length 18.64 cm) from April to July in 2008. In the olive barb ejaculated milt, volume (µl/g), motility (%), duration of motility (s), concentration (x 10 super(10)/ml) and pH values were found to be 6.06±0.32, 88.27±0.71, 171.41±7.41, 5.16±0.05 and 7.75±0.04, respectively. Milt volume was significantly (P<0.05) correlated with sperm concentration. Milt volume, sperm concentration, motility and duration of motility significantly varied (P<0.05) during spawning season.

Biological characteristics and determination of population dynamics parameters of Nemipterus japonicus in the coastal waters of Province Bushehr, Persian Gulf

This study was conducted to determine biological characteristics and population dynamics parameters of threadfin bream (Nemipterus japonicus) in Persian Gulf (Bushehr Province), during November 2006 and October 2007. The minimum and maximum specimens were 75-273 mm FL and their weight was 7.6 - 351.9 g. Based on the exponential relationship between fork length and weight, slope (b) for individuals, males and females was 2.987321, 2.992546 and 3.007314, respectively. The emptiness value (V) was 45.6% and it shows that N. japonicus is a moderate feeder. The results of Fp indicates that crustacean with 78.2% are main foods, mollusca (27.7%), fishes (20.7%), polychaeta (19.2%) and Foraminifera (11.7%) were identified as minor foods and phytoplanktons (9.9%), nematoda(8.0%), echinodermata (2.3%) and sea weeds (0.3%) were random foods. The reproduction studies showed the spawning season extended within 2 peaks, from April- May and September and main spawning occurs in spring season.The mean absolute and relative fecundities were 472388±42633 and 3817±293 (X±SE), respectively. The maximum, minimum and mean of oocyte diameter were 0.448, 0.022 and 0.221mm (SE=0.071), respectively.The fork length at 50% maturity estimated to be 20.25 cm for females. The growth coefficient (K) , length infinity (L∞ ) and ɸ' was estimated 0.42/yr , 34.17 cm and 2.69, respectively. The coefficient of total mortality, fishing mortality, natural mortality and E was 1.37, 0.43, 0.94 and 0.31, respectively.

The study of biological characteristics and heavy metal determination of Cd, Pb, Fe, V, Ni in the muscle, liver and gonad tissues of kingfish Scomberomorus commerson in the coastal waters of the Hormozagan Province (Persian Gulf)

Biological studies and heavy metal (Ni, v, Fe, Pb,Cd) determination in liver, gonad and muscle of Scomberomorus commerson were carried out from Oct 2006 to Sept 2007 in Hormozgan coastal waters. 599 Samples were gutted for reproduction and nutrition studies, fork length and weight were measured to nearest cm and g respectively. Meanwhile 40 samples were also investigated for heavy metal studies. All specimens were collected from two major landing sites (Bandar Lengeh & Bandar Abbas). Minimums & maximum fork length & weight were 29, 128 cm & 235 and 15350 g respectively.Isometric growth was shown according to our study and b was estimated 2.9 (overall), 2.91(male) & 2.89 (female). The average relative gut length was 0.52± 0.007 and it was determined that S. commerson is a carnivorous. More than 99 percent of gut content was different teleost fishes. Gastro somatic index had two peaks in Nov & Jan (before spawning) and with a decreased trend in July, the spawning period. Occurrence of empty stomach was estimated % 65.77. Maximum amount of condition factor was in Dec. Spawning season was started from June. The average of Absolute & relative fecundity (to weight unit) was 1217149±179315 and 178.2±15.58 respectively. Lm50% was estimated 75 cm for females. Sex ratio was 0.97: 1 (male: female). Chi- Square test showed no significant difference (p>0.05). Maximum amount of hepatosomatic index was estimated in March.Metal concentrations were determined using either Flame Atomic Absorption Spectroscopy (for Fe) or Graphite Furnace Atomic Absorption Spectroscopy (for Pb,Cd,Ni and V). The mean concentration (μg/g dry weight)of Pb,Cd,Ni,V and Fe in the liver were 0.0309, 0.0268, 0.0672, 0.0077, 2.5159 in the gonad 0.0440 ,0.0295, 0.1096, 0.0000, 1.4449 and in the muscle 0.0244, 0.0324, 0.0656, 0.0128, 1.6138 respectively. The maximum metal concentrations were below the maximum permissible limits for human consumption recommended by the USEPA, WHO and the UK. The results of Kendall's Tau-b correlation coefficient were as follows: The Liver tissue: There were significant positive linear relationships between accumulation of V, Fe, and Pb with Fork length, Pb and Fe with weight, GSI with Pb, Cd, V and 109 Fe, and a negative linear relationships between HSI with accumulation of V and Fe, Fork length, weight and GSI. The Gonad tissue: There were significant positive linear relationships between GSI with accumulation of Pb, Cd, Fe, Fork length and weight, a negative linear relationship between HSI with Fork length, weight and GSI. The Muscle tissue: There were significant positive linear relationships between accumulations of V, Fe with Fork length and weight factors and as well as GSI with Cd, V, Fe, Pb, Fork length and weight,a negative linear relationship between HSI with Fork length, weight, Cd, Fe and GSI. The results of Mann-Whitney U tests (P≤0.05) show that there were significant differences between summer and autumn from heavy metal contents in the studied tissues point of view. The only exceptions were for Ni in the liver, gonads and muscle and as well as there were significant differences between male and female from heavy metal contents in the studied tissues. The only exceptions were for Pb in muscle, Ni in liver, gonad and muscle, V in muscle, and Cd and Fe in gonads.

The study of biological characteristics and determination of population dynamic parameters of sawtooth barracuda (Sphyraena putnamae) in the Persian Gulf (Hormozgun Province waters)

The biological characteristics and population dynamisms of Sphyraena putnamae, were studied in the northern Persian Gulf and Oman Sea restricted to Hormuzgan province waters within 13 months period, from November 2006 up to November 2007. Biometrical and anatomical measurements were carried out, and biological surveys were conducted on 486 specimens. On the other hand, the growth and mortality parameters were estimated by using 3096 samples. These samples were collected from 3 landings, namely Bandar Abbas, Bandar Lengeh and Bandar Jask. The measurements of the minimum and maximum Fork lengths and weights were 11.7 to 8.03 cm and 135.0 to 4140.0 g, respectively. The results indicated that this species, having the Relative Length of Gut, RLG=0.34±0.002, is strongly carnivorous (often fish-eater), proven by the fact that more than 98% of its stomach contents were fish pieces. Examining the changes in the index of stomach emptiness by the percentage of CV = 0.47% indicates that this fish is Moderate feeder. The level of feeding increased in March, before spawning and decreased in June and September, simultaneously with the spawning season. There are 2 peaks of reproduction or spawning seasons during the months of April-May and September, of which the prior is assumed as the main spawning. The sex ratio (M:F) was calculated 0.5:1.0(X2 =2.11), which did not show a significant difference with expected level of 1:1 (P>0.05). The average absolute and relative reproduction rates of Sphyraena putnamae is respectively as follows: 1866827.1±255448.9 and 1097.7±94.3. The highest and the lowest diameter of matured egg are from 200 to 750 μ, and its average diameter is 402.10 ± 0.190 μ. A parameter for Saw-tooth barracuda length measurement, Lm50, based on the Fork-length, was calculated as 54.01 cm. In other words, as far as the fisheries management is concerned, the fish whose lengths are less than 54.01 cm should not be caught. The calculated level of (R2) (correlations of total length & weight), indicated strong correlations between length and weight of this fish, and the obtained formula included W =0.007100 FL 2.9295 and reinforced this assumption. The “K” Index for this fish in 3 above mentioned landings (Jask, Bandar-Abbas and Bandar-Length) were 1.24, 0.37 and 0.46 per year, respectively and the FL index for the same landings were estimated as 129, 110 and 134 cm, respectively. The growth coefficient (MONRO) for the above mentioned regions were calculated as 3.601, 3.647 and 3.917, respectively; and in the surveyed regions there were no significant differences in populations. The Total mortality coefficient (Z) was calculated 0.76, 1.12 and 1.07 per year, the Natural mortality coefficient was 0.46, 0.63 and 0.70, and the Fishing mortality coefficient (rate) (F) was found to be 0.30, 0.49 and 0.37 per year. The value of the exploitation rate (E) is equal to 0.39 per year, indicating that this species is an under-exploited resource, and there is no excessive fishing pressure on the fish supply of this species in the afore-said regions. The highest level of exploitation was found for ‘Bandar Abbas’ fishing region and the lowest level of exploitation is in ‘Bandar Lengeh’ waters.

Determination of biological characteristics and blood groups of hilsa shad (Tenualosa ilisha) in the north of Persian Gulf (Bushehr coastal waters)

Hilsa shad, Tenuolosa ilisha, belongs to Clupeidae family and Alsinae subfamily is an euryhaline pelagic and anadromous species living in marine and freshwater waters. Regarding to study the biological characteristics of this species, this study was carried out in the Northern Persian Gulf within Bushehr province waters during years 2006-7. A total of 344 specimens were collected and transported to the laboratory for further different biological measurements consist of: reproduction (GSI, fecundity, maturity stages), feeding (stomach contents, food preference ...), aging; 58 morphometric and ٧ meristic measurements. The results indicate that minimum, maximum and mean body weight are 203, 953 and 481.35±147.64 g, respectively and this values for total length are 26.5, 45.1 and 35.99±3.98 cm. For food regimes, the most abundant phytoplankton foods belong to Bacillariophyta (83.74٪) and zooplanktons of Arthropoda (51٪). The mean RLG was measured about 1.53±0.22 and the mean feeding intensity was about 51.79±38.13. Also, the aging of studied fishes showed that they have 2 to 4 years and most of the samples had 2+ years. The reproduction studies showed that Indian shad is a batch spawner species. The average gonadosomatic index (GSI) is 1.64±1.382 and the main spawning season was determined for April-May.

Distribution and growth biology of rock oyster Saccostrea cucullata in the Oman Sea

Distribution and growth biology of rock oyster (Saccostrea cucullata) in the northern shores of Oman sea have been struied. During this one-year study, samples have been taken monthly from ten different stations. quantity of vertical distribution of this species was obseredl in the mid - intertidal zone. After determining the spread pattern, the following subjects were studied: - Growth parameters - Distionction of the "cohorts" - Determination of "spawning Season" - Condition of the "Gonado Somatic Index" - Sex ratio - Length of the species during the first year of maturation. - Identification and determination of percentage of "Biofouler Organisms." Results obtained from the above - mentioned studies show that considering a growth factor (k) of 0.52, the value of "Loo " for this species is equal to 114 (mm).Five to six different age groups were observed among the samples taken. In the areas where this study was conducted, this species grows 24 to 30 (mm) in the first year of its life this growth rate is lower in the higher - aged grpups relative to the lewer - aged groups, so that the longest size classes grow between 4 to 6 (mm) per year. • The maxinum Value of the "Condition Index" is in the pozm area and the minimum value of it belongs to Darak and Tang areas. Along with the increase in the growth of gonads the above mentioned condition index increases gradually simultaneous with the onset of spawning. Also, study of the influence of environmental factors on the maturation process suggests that the most important factors affecting maturation and spawing are temperature and salinity. The study of GSI shows that this species has a coordinated bimodal spawing trend, with its spring peak in june and its autumn peak, being still higher than the spring peak, in september. The recruitment curve confirms the above spawning peaks with its peaks occuring after a delay of one month or maximum two months in comparison to the spawning peaks. The results of calcuation of "Sex Ratio" of this species in each area show that sex ratio is 1:1. Among the first size classes that reach maturity, nearly 67% of the samples are male and the remaining 33% are female. with the increase in the shell size, the percentage of males decreases and the percentage of females increases. , The above facts prove the protandrous nature of this species the diagram showing the sizes of the first samples which reach maturity suggests that more than 50% of the samples mature after their length exceeds 36 (mm). The shortest mature sample was found to have a length of 22(mm). After studying "Biofouler Organism" nine different invertebrate groups were indentified. Barnacles and Tunicates have the highest and lowest percentages respectively. According to zonal observations, Barnacles and polychacta do the greatest damage to this species.

Population diversity studies of pharaoh cuttlefish (Sepia pharaonis) in the Persian Gulf and the Gulf of Oman

The pharaoh Cuttlefish (Sepia Pharaonis) is the most abundant species in the persian gulf and oman sea. The stock patterns of this species was studied conserning biological, morphological and electrophoretical aspects. In addition to measuring the biological patterns; 21 quantitative and qualitative factors were measured or counted. There tissues namely muscle, eye and liver were also used for further polyacrylamide electrophoresis analysis (SDS-Page method). The densitograms of protein bands of each tissue were prepared by Gel-Scanner and also the amount of bands' areas were estimated. The results of LSD test showed that tentacle length (TL), Tentacle club length (TCL) and TCL were indicative factors which they showed significant difference between male TL and female specimen of Bushehr and Balouchestan regions. Regarding to length and weight frequencies data the results indicated that males are always bigger than females and also, the cuttlefishes of the gulf of oman are bigger than persian gulf's samples. There were found a significant sample correlation (95%) between different quantitative parameters and the most correlation (0.963) was found to be between TL and TCL; whereas the less correlation (0.384) was observed between GL and LA3. However the gill length factor illustrated the less correlation with the other factors. The results of Cluster analysis for both sexes showed that the cuttlefishes of both studied regions belongs to seperate stocks. The electrophoretic experiments of proteins showed that the protein bands of the sample tissue of muscle and eye from both sampling areas revealed significant differences; whereas the tissue of liver wasn't recognized as an indicative tissue for population studies. Taking into consideration the findings of the present study including: (1) difference in spawning season, (2) results of dendrograms, (3) observed Significant differences in one-way analysis of variance (ANOVA) for morphometric measurements, (4) differences in body length and weight, (5) ecological variations of the persian gulf and oman sea, (6) as well as the results of electrophoresis of proteins have indicatend that: "The Pharaoh cuttlefishes of Bushehr and Balouchestan waters belong to two seperate stocks. Also, it is believed that each region has propably two different populations and more studies are needed to approve this result.

Fishery biology of Indian mackerel in Sri Lankan coastal waters

The objective of the project was to determine the reproductive biology of Indian Mackerel (Rastrelliger kanagurta) using Gonado-Somatic Index (GSI); length at first maturity; spawning season; morphological characteristics; and stomach contents.

Biology and distribution of grouper (Epinephelus coioides) in province waters (Abadan Bhrakan)

This survay has been done from Januray 2000 till May 2002 in Khouzestan costal waters. Four species of grouper were identified from which orange spotted grouper (Epinephelus coioides) was the dominant species. For studing environmental parameters and reproductive biology, age, growth parameters and mortality rate samples were collected by fishing ship. Samples were taken montly in 4 days by fishing traps and trawls. In addition, some samples were obtained from Khozestan fish landing centres. Environmental factors such as PH, 02, salinity, water temperature and depth of traping areas, were measured. To identify species, morphometric characteries of 452 individal fishes were measured. Stomach contents of 394 fish were has survaid, from which stomach of 226 fish, and 168 fish had empty stomachs. Percentage of empty stomachs (cv) in males was more than females. Food items found in 73 percent of stomach were crab (11%), shrimps (8.8%) , squids (3.9%), gastropods (17%) and bivalves (0.4%). Feeding intensity in year classes did not obay logic trends The importance relatively indicator (I.R.I) were 81, 9.9, 4, 1.5 and 0.3 percent for fish, crab, shrimp, squid, gastropod and bivalve respectively. For age determination, sagita otoliths of 450 fish were taken and countable sections were obtained from 425 specimens. Relative frequency distribution of opaque and transparent rings showed that each opaque growth ring generates once a year from November to September. It seemed that generation of opaque rings is affected by temperature and photoperiod changes. Correlation between length and age was calculated using Von Bertalanffy's least square method. Following equasion was obtaind: L(t) : 122.27 (1 e 0.146 (t+0.482)) Growth parameters were determined through by Ford Walford equasion and Response Surface and Shepherd subcommands in Elefan program and L00 and K amounts were have determined. Correlation between length and age of 635 fish was determined by gender . Length and age correlation was calculated by exponential model and between total length and standard length by straghit line model. Correlation between age and weight of sagita was calculated by total length and age. The most Correlation was between sagita weight and fish age (r=0.876). Total mortality rate (z) was estimated by Length Converthed Method , Jones and Vanzaling and Powel Wetherall. Total mortality rate was z=0.39. Natural mortality rate, using Pauly method was calculated M=0.32. Fishing mortality (F) was 0.08. Gonads of 425 fishes were surveid within 18 month, from which 363 were female, 46 were male and 16 were sex reversing individuals .Total length of females varied from 26 to 95.5 centimeters while males length varied from 56.5 to 107 centimeters. Sex reversing individuals had a length of 47.5 centimeters, when two years old and 62.5 centimeters at age of 3 years. From the mentioned 425 fish, 401 individuals were matured, containing 339 females and 62 males, 5.47 females against each male. Montly changes of Gonadosomatic Index (GSI) by total body weight and standard length and total body length showed that this index increases from march to May and maximum increase was in May . This experiment was adapted in spawning season. Potential, relative, and absoulate fecundity was estimated by counting eggs in three samples. Total amount of traped fish using special traps was 16182.18 kg from which Epinephelus coioides provided catching 15353.43 kg of it (91.27 %) and By catch was 141.18 kg (8.24 %). Total average CPUE for whole catch was 123.33 kg/day/vessel. Total amount of catch was estimated 232.04 tons, considering CPUE of total catch and total Khuzestan trap ships effort.

Dispersion, population dynamics and stock assessment of Caspian Sea prawns, genus Palaemon in Guilan Province coastal waters

Biological aspects, population dynamics and stock assessment of the Caspian Sea prawns Palaemon adspersus and Palaemon eleganse were investigated in Guilan coastal water of the Caspian Sea. Sampling was done monthly with a bottom trawl with mesh size of 3 mm in cod end in 0 - 5 m and 5 - 10 m depth in areas as Astra, Shafa Roud, Anzali, Chonchanan Chamkhaleh and Chaboksar during year 2002. Results of one year sampling showed that mean total length of Palaemon adspersus (pooled data) was 39.9±6.84 mm (X±SD) and mean wiegth was 1.133±0.67 g. The mean total length of females and males was 41.6±7.5 mm and 37.9±5.2 mm respectively and mean weight for the mentioned sexes was 1.353±0.65 g and 0.868±0.38 g respectively. There was significant differences in mean length and weight of females and males (P<0.05). The mean total annual sex ratio of males: females for this species was 1.4 and this sex ratio deviated significantly from 1:1 (X2, P<0.05) and biased towards males in the population of this species. The spawning season of Palaemon adspersus begins in April and ends in September with a peak in June . Mean fecundity of this species was 1994.5 ± 506.6 . The growth coefficients Loo and K for females were estimated as 58.5 mm and 2.3 /Year and for males as 55.9 mm and 2.6 /year respectively . The mean CPUA ( catch / Km2 ) for this species was 9.99 ± 33.2 kg / km2 and the correspondance biomass was calculated as 5067.7 kg in 0 - 10 m depth . The mean total length of Palaemon elegans (pooled data ) was 27.5 ± 5.7 mm (X±S.D) and mm and 24.01±4.18 mm respectively and mean weight for the mentioned sexes were was 0.553 ± 0.3 g and 0.237±0.15 g respectively. There was significant differences in mean length and weight of females and males (P<0.05). The mean total annual sex ratio of males:females for this species was 0.57 and in this species also sex ratio differed significantly from 1:1 (X2, P<0.05) and skewed towards females in the population of this species. The spawning season of Palaemon elegans extended from May to September with a peak in July . Mean fecundity of this species was 642.7±313.4. The growth coefficients LOO and K for females were estimated as 42.119 mm and 2.40 /Year and 33.87 mm and 2.50 /year for males respectively. The mean. CPUA ( catch/ Km2 ) for this species was 0.75±3.86 kg/km2 and the correspondance biomass was calculated as 382.1 kg in 0-10 m depth .

Study on the reproductive biology of Pinctada fucata (Gould) (Mollusca: Pteriidae)

Annual cycle of gonad development and spawning in pearl oyster, Pinctada ficata (Gould) in Nakhiloo, Northeast Persian Gulf, was investigated over two years from August 1994 to June 1996. Gonadal condition was assessed by staging criteria to describe gametogenic development from histological preparations of randomly collected individuals of all sizes. A bimodal gametogenic pattern with summer and autumn spawning periods was evident throughout the study. Gametogensis commenced in November-December which proceeded by major gonadal maturation during February-April. Summer spawning was observed from April to July with major spawning at the latter end. During spawning peak in July, low level of gametogensis was noticed. Gametogenic activity was picked up again in August-September which proceeded by autumn spawning from September to December. Towards the end of spawning season, incidence of gonadal inactivation increased. Minimum level of gonadal activity was observed in November. Temperature regime appears to have influential role in regulation of gametogenic and spawning processes. Gonadal development and spawning trends were similar in both sexes. P. radiaata was found to be protandrous hermaphrodite which matured as a male at shell height greater than 20 mm. Biseivality was uncommon and the sex ratio was about 1:1. Ultrastructure of gametes were investigated in the Pictada fucata (Gould). "Auxiliary cells" closely accociated with developing oocytes were observed. Each oocyte seems to be associated with only one secretory cell. which is characterized by an abundant rough endoplasmic reticulum at the onset of vitellogenesis. Contact between this cell and a developing oocytes is maintained by a desmosome-like junction which can be observed when the vitelline coat is formed. these "auxiliary or nursing cells" seem to play a tropic role in vitellogenesis, and may be involved in the formation of the vitelline coat of the oocytes. Oocytic degeneration is observed in this species, it is a continuous phenomenon of varing intensity throughout the year. The ultrastructural changes resulting in lysis of the oocyte are described. Mature spermatozoa consist of a broad, cap-shaped acrosomal vesicle, subacrosomal material, a round nucleus, two triplet substructure centrioles surrounded by four spherical mitochondria, and a flagellum anchored to the distal centriole and plasma membrane. Spermatozoa of Plucata closley resemble to those of other investigated Pteriidae. Changes in proximate composition of soft tissue and gonadal cycle of Pinctada fucata was studied. Mobilization and utilization of stored reserves are apparent during gametogenesis and gonadal maturation. Protein reserves are utilized during spermatogenesis while reserved carbohydrates form the main energy donor in oogenesis. The role of lipid as am.: energy reserve is second to that of carbohydrate.

Reproductive physiology of ribbon fish (Trichiurus lepturus)

The ribbon fishes ‘of the family Trichiuridac are represented as one of the most important food resources in Indian ocean. High density of the dominant species of ribbon fish (Trichiurus lepturus) in Oman sea and the 'Tillable catch in last yeas (more than 7000 tones per year) makes a trust area for studing their population biolog and stock assessment. As our knowledge on reproductive biology of this species has an important role on their fisheries management, as well as conservation of this stock from decline or over fishing, this research was held to determine some aspects of reproductive physiology of ribbon fish and the effects of environmental factors in gonadal cycle. The goals of the present thesis is to determine some aspects of reproductive physiology such as gonadosomatic index (GSI) , hepatosomatic index (HSI), condition factor (Ko, fecundity, sex ratio, size at first maturity, size at maturity (LM5O) and their relative hormonal & biochemical fluctuations. In this regards annual variation of sex hormones ic. estradiol 17-B, progestron, cortisol, testostrone and gonadotropins FSH (GTH-I) , LH (GTH-ll)I were measured ; gonadal histological studies were done by light & electron micrography. The research was carried out from April 1995 to January 19% in Ras Nleidani in the north part of Oman sea, and the environmental factors such as temperature, salinity, oxygen, rainfall and pH were measured. The effects of these parameters on reproductive cycle and hormonal fluctuationswere discussed by using correlation and principle component analysis (PCA). Female Ribbon fish reproductive strategy shows the same paterns of nonguarder marine teleosts. T. lepturus has more than one spawning season (existance of egges in different size in each month) and therfore it must have asynchronous ovaries and belong to continious spawners. GSI and HSI are good evidences for this type of reproductive patern. The testis of the lobular type , which is typical of most teleosts , is composed of numerous lobules which are separated from each other by a thin layer of fibrous connective tissue. GSI fluctuations revealed prolong- spawning time in males. There is significant increase in 17-13 estradiol. progestrone , cortisol and gonadotropins with maturity and prespawning period of female T lepturus. Plasma concentration of E2 and GTH II incresaed along with water temperature increasing (3300).. Spawning was observed from Nov. 1995 to Apr. 1996 in this species. Progestrone increased significantly with increasing rainfall in this season (P<0.01). Plasma cortisol levels increased with maturation and vitelpgenesis and also with the peak of spawning. From lenght-weight frequency and size distribution in each age groups and also minimum size at first maturity (52a cm) it would he concluded that T. lepturus must be matured at 2 years of age. Serum cholestrol and triglicerides significantly increased when maturation occured in this species. The relationship between alkaline phosphatase activity and hormonal fluctuations with maturity and vitelogenesis were discussed. Proximate compostion (muscle) shows significant variation with spawning period and maturity. Absolute individual fecundity (17420-159150) increased with body length and weight. Ultrastructural observations show dramatic variation in cell membrane (0ocyte membrane), yolk vesicles and, nucleolus dispersal in relation to maturity stages. fluctuations of gonadal hormones were discused in relation with vitelogenesis. Testosterone increased in males from Nov: to Mar. due to environmental impacts and spawning time. Sex ratio in different depth (10-40 m ,80-110 m) shows significnt differences in this ratio for two depths. In 10-40 m depth female shows dominant abundance to male in each months that may be due to their reproductive migration behaviour. The effects of temperature photoperiod and rainfall to maturity and spawning were discussed. According to -pawning period of T. leptunts in our sampling area it could be suggested that ribbon fish fi,theries must be restricted in the peak of spawning seasons (Feb. to Mar.) and in the spawning grounds (under 40 m depths). Other suggestions for population conservation have been mentioned.

Biological observations in Indian mackerel, Rastrelliger kanagurta (Cuvier) 1816, (Pisces: Scombridae) from East African waters

The present study was under taken to provide further and more detailed information on the apparent seasonal and relative abundance of the species, food and feeding habits. Spawning season and size composition. The incidence of parasites, in relation to the month of the year and the fish length, was also examined.