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Stock Status of Pufferfish Lagocephalus sceleratus (Gmelin, 1789) Along the Egyptian Coast, Eastern Mediterranean Sea
Mahmoud M. S. Farrag
,
Alaa Eldin A. K. El-Haweet
,
El-Sayed Kh. A. Akel
,
Mohsen A. Moustafa
Issue: Volume 3, Issue 6-1, November 2015
Pages: 83-93
Received: 27 August 2015
Accepted: 13 September 2015
Published: 29 November 2015
DOI:
10.11648/j.ajls.s.2015030601.22
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Abstract: Stock of pufferfish Lagocephalus sceleratus was evaluated using specimens that collected monthly from the commercial fishing boats at landing sites along whole the Egyptian Mediterranean coast during 2012. Specimens were ranged from 5 to 83cm (TL) in length with an average 43.01± 13.5cm and total weight from 2.1-5400g with an average of 1103.27±850.83 g. The length-weight relationship revealed negative allometric growth for males, females and combined sexes with insignificant difference between males and females at (P > 0. 05). The highest condition factor (1. 13) was recorded for immature/smaller fishes while the lowest value 0. 86 was recorded for largest female individual. Age determination by two methods (length frequency analysis and vertebrae) revealed seven years old with no significance difference between mean lengths at age of two methods at (P > 0. 05). Von Bertalanffy growth parameters for combined sexes of length frequency were L∞ = 106.34 cm, K = 0.17 year-1 and to = 0.0228 year-1, while they were L∞ = 101.63cm and K = 0.189 year-1 and to = 0.1186 for vertebrae data. By using data of length frequency, the population parameters were, total mortality (Z=1. 01 year-1), natural mortality (M= 0. 347 year-1), fishing mortality (F= 0. 663 year) and exploitation ratio (E= 0. 657). The length at first capture (Lc) was 32. 34cm, while length at recruitment (Lr) was 25. 95cm. Yield per recruit (Y/R) at current parameters was 447.26g. The maximum sustainable yield per recruit (MSY) was 467. 42g, at fishing mortality (FMSY) 0.403 year-1 Which is lower than current fishing mortality. The (Y/R) at the biological reference points (F0. 1 & Fmax) were 423.72 g and 467.42g respectively. The fishing mortalities at these points were 0. 203 year-1 and 0. 403 year-1 for F0. 1 and Fmax respectively giving lower values than current fishing mortality reflecting over-exploitation status. Inspite of, the fishing of pufferfish is prohibited by the Egyptian law, its stock in the eastern Mediterranean is overexploited but still growing well and the younger individuals are in good condition reflecting a good adaptation in new habitat, and explain the illegal trade of this species in different markets. The over exploitation suggests reduce it or Y/R to level of F0. 1 for the point of conservation regardless its poisonous effect. The importance of present data of such species could emphasis the need of special management plan for conserve and better use of economically valuable fishery resources.
Abstract: Stock of pufferfish Lagocephalus sceleratus was evaluated using specimens that collected monthly from the commercial fishing boats at landing sites along whole the Egyptian Mediterranean coast during 2012. Specimens were ranged from 5 to 83cm (TL) in length with an average 43.01± 13.5cm and total weight from 2.1-5400g with an average of 1103.27±850...
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Distribution of Short Neuropeptide F-like Immunohistochemical Reactivity in the Brain and Midgut of the Terrestrial Isopod, Armadillidium vulgare (Latreille)
Maged M. A. Fouda
,
Makio Takeda
Issue: Volume 3, Issue 6-1, November 2015
Pages: 76-82
Received: 30 September 2015
Accepted: 7 October 2015
Published: 29 November 2015
DOI:
10.11648/j.ajls.s.2015030601.21
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Abstract: Immunohistochemical reactivity against short neuropeptide F (sNPF-ir) was detected in both the brain–subesophageal ganglion (Br-SOG) and midgut epithelial cells of the isopod, Armadillidium vulgare. More than 194 cell bodies showed immunohistochemical reactivity in the brain and SOG. A wide distribution of sNPF-ir occured in the optic lobe (OL; 82 cells), accessory lobe (AL; 56 cells), central body (CB), tritocerebrum (Tr; 18 cells), circumesophageal connective (COMI; 7 cells), and subesophageal mass (SOG; 25 cells), while no sNPF-ir was observed in the deutocerebrum (DC) and pseudofrontal organ (PFO). sNPF-ir was also detected in both paraneuronal cells and stomatogastric nerve elements in the midgut muscle layer. Immunostaining of cells in the Br-SOG and midgut was blocked by preabsorption test. No difference was found in number or distribution of sNPF-ir between males and females. sNPF is both neuropeptide and midgut factors. This wide distribution suggests that sNPF may not only coordinate feeding and digestion in A. vulgare but also support multiple functions.
Abstract: Immunohistochemical reactivity against short neuropeptide F (sNPF-ir) was detected in both the brain–subesophageal ganglion (Br-SOG) and midgut epithelial cells of the isopod, Armadillidium vulgare. More than 194 cell bodies showed immunohistochemical reactivity in the brain and SOG. A wide distribution of sNPF-ir occured in the optic lobe (OL; 82 ...
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Inducing Molting by Eyestalk Ablation in the Red Swamp Crayfish, Procambarus clarkii from the Egyptian Freshwaters
Mohamed A. Amer
,
Awaad A. M. El-Sayed
,
Khalid A. Al-Damhougy
,
Samir A. Zaahkouk
Issue: Volume 3, Issue 6-1, November 2015
Pages: 69-75
Received: 30 September 2015
Accepted: 7 October 2015
Published: 29 November 2015
DOI:
10.11648/j.ajls.s.2015030601.20
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Abstract: Eyestalk ablation was used for inducing molting in the freshwater crayfish, Procambarus clarkii at the laboratory conditions. The results exhibited that, both of unilateral and bilateral eyestalk removal accelerated molting rate than in non-ablated or intact individuals of this species. The use of unilateral eyestalk removal has low effect, induced molting at the 6th week and reached 100% at the end of the 16th week, compared with starting molting at the 8th week for control, which did not exceed than 40 % for molted individuals at the end of experiment, with 20% mortality for each. On contrast, the bilateral ablation has high effects and induced molting rapidly at the first and second weeks for the two experiments. It was associated with high mortality rates, averaged 28.33%for ablated individuals of the two experiments, increased gradually to 51.67%and 80.0% for individuals of the premolt stages, which showed signs of molting but were unable to complete molting cycle and died at the end of the last week of each experiment. Repeating molting was recorded for only one bilateral ablated animal after 11 days, but no molting was noticed for control group, with mortality of 20 %.The percentages of increments in body dimensions included body length, carapace length, chelae length and total body weight were calculated. Most ratios of increments, except only total body weight, were high in ablated males than ablated females, as well as clearly higher in normal molted males and females than ablated ones, but declined sharply to 3.30±2.91% in total body weight for bilateral ablated males.
Abstract: Eyestalk ablation was used for inducing molting in the freshwater crayfish, Procambarus clarkii at the laboratory conditions. The results exhibited that, both of unilateral and bilateral eyestalk removal accelerated molting rate than in non-ablated or intact individuals of this species. The use of unilateral eyestalk removal has low effect, induced...
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Effects of Replacing Soybean Meal with Jojoba Meal in Sea Bream (Sparus aurata) Diets on Fish Performance
Norhan E. Saleh
,
Mohamed M. Toutou
Issue: Volume 3, Issue 6-1, November 2015
Pages: 62-68
Received: 21 September 2015
Accepted: 21 September 2015
Published: 29 November 2015
DOI:
10.11648/j.ajls.s.2015030601.19
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Abstract: The study aimed to investigate the effect of replacing soybean meal (SBM) by treated, either by heat (HJM) or by boiling (BJM), Jojoba meal (JM), to eliminate the negative effects of antinutritional factors, at 10, 20 and 30% replacing levels in diets of sea bream (Sparus aurata)) fingerlings on growth performance, nutrient utilization, body biochemical composition, middle intestine morphology and measuring of some hematological parameters of sea bream. Results indicated an enhancement in growth and feed utilization for all fish groups fed boiled followed by heated jojoba meal at 20% inclusion level compared to the control and other tested fish groups. Results of fish biochemical analyses indicate significant increase in crude protein contents in fish fed 10 and 20% HJM and 20% BJM. The present results also showed obvious increment in lipid contents as the level of JM inclusion level increase. Serum total protein, albumin and globulin levels indicated no negative effects when soybean meal was partially replaced by jojoba meal. Also, results indicate pronounced gradual decrease in serum cholesterol levels coincided with an increase in triglyceride. Middle intestine morphology examination showed significant variations in thickness of muscularis layer, villi length and width and also number of goblet cells.
Abstract: The study aimed to investigate the effect of replacing soybean meal (SBM) by treated, either by heat (HJM) or by boiling (BJM), Jojoba meal (JM), to eliminate the negative effects of antinutritional factors, at 10, 20 and 30% replacing levels in diets of sea bream (Sparus aurata)) fingerlings on growth performance, nutrient utilization, body bioche...
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Evaluation of Adding Potassium Iodide and Thyroxin to Sea bream (Sparus aurata) Fingerlings Diets Containing Fenugreek as a Growth Promoter
Ashraf El-Dakar
,
Shymaa Shalaby
,
Bahig Nemetalla
,
Norhan Saleh
,
Eman Sakr
,
Mohamed Toutou
Issue: Volume 3, Issue 6-1, November 2015
Pages: 53-61
Received: 20 September 2015
Accepted: 22 September 2015
Published: 29 November 2015
DOI:
10.11648/j.ajls.s.2015030601.18
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Abstract: This study was conducted to investigate the effect of addition of potassium iodide and thyroxin to sea bream fingerlings diets containing fenugreek as growth promoter on growth performance, feed utilization, body composition, biometric measurements indices, some serum constituents and histological characteristics of sea bream intestine. The 1st group was considered as a control which fed on the basal diet (C) for 84 days. The experiment was designed to determine the effects of using 2% fenugreek/kg diet (F), 2% fenugreek+0.05mg thyroxin/kg diet (FT4), and 2% fenugreek+0.1g potassium iodide /kg diet (Fi). The results of the present study showed that the best growth performance and feed utilization values were recorded in fish fed diets supplemented with F. The lowest growth performance and feed utilization values were recorded in fish fed diet supplemented with iodine when compared with corresponding values in case of C group. Histological analysis showed satisfactory values in F and FT4 groups compared to the control.
Abstract: This study was conducted to investigate the effect of addition of potassium iodide and thyroxin to sea bream fingerlings diets containing fenugreek as growth promoter on growth performance, feed utilization, body composition, biometric measurements indices, some serum constituents and histological characteristics of sea bream intestine. The 1st gro...
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Greenwater, Marine Bacillus subtilis HS1 Probiotic and Synbiotic Enriched Artemia and Rotifers Improved European Seabass Dicentrarchus labrax Larvae Early Weaning Length Growth, Survival, Water and Bacteriology quality
Salem Ahmed Md.
,
Nour A. M.
,
Srour T. M.
,
Assem S. S.
,
Ibrahim H. A.
,
El-Sayed H. S.
Issue: Volume 3, Issue 6-1, November 2015
Pages: 45-52
Received: 16 September 2015
Accepted: 16 September 2015
Published: 29 November 2015
DOI:
10.11648/j.ajls.s.2015030601.17
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Abstract: The present study conducted in Fish Reproduction & Spawning Lab., NIOF, Alexandria, Egypt. European sea bass Dicentrarchus labrax newly hatched larvae from 8 dph to the 40 dph was reared according to (Süzer et al., 2011). The 6 tanks was green water with N. salina Algal count not less than 300000 cell/ml. The experimental treatments using green water using N. salina as positive control (G), green water plus marine probiotic bacteria (G+MP) and green water plus synbiotic (G+S).4 hours enriched rotifers Brachionus plicatilis started from the 7th dph until the 14th dph, the beginning of cofeeding on 6 hours enriched Artemia fransiscana (GSL) nauplii started and rotifers reduction started in the 18th dph and stopped from the 20th dph and artemia napulii fed alone until the 25th dph, 25dph larvae started feeding on artemia metanauplii and cofeeding with Orange® P 1/2 Small microdiets with 100-200 micron to 35dph. From the 35th dph artemia metanapulii stopped and larvae fed only on O.range® until the end of the experiment (the 40th dph). The treatments were green water using Nanochlorapsis salina algae (G), greenwater plus marine Bacillus subtilis HS1 Probiotic bacteria (G+MP) and greenwater plus synbiotic (G+S) in 30 l tanks in duplicates. Microbiological measurements were performed in water samples in every larvae critical stage (7, 14, 21, 25, 35 and 40dph) for colony forming unit (CFU) of total bacterial count, Vibrio, Staphylococus, Aeromonas and Bacillus. Also water quality measurements were performed in the beginning of the experiment in 2 pm and in the same time in the 7, 14, 21, 28, 35 and 40 dph newly hatched larvae tanks. Finally, the results of the 40dph early weaned larvae showed significantly (p<0.05) higher final total length achieved by (G+MP) followed by (G+S) and the lower significant (p<0.05) recorded by (G) treatment. The bacterial counts of the Aeromonas not detected in all treatments, the other bacterial counts showed promising results of (G+MP) and (G+S) than (G) treatments in both inhibiting potentially pathogenic bacteria counts and also in improving the potentially useful bacterial counts.
Abstract: The present study conducted in Fish Reproduction & Spawning Lab., NIOF, Alexandria, Egypt. European sea bass Dicentrarchus labrax newly hatched larvae from 8 dph to the 40 dph was reared according to (Süzer et al., 2011). The 6 tanks was green water with N. salina Algal count not less than 300000 cell/ml. The experimental treatments using green wat...
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Production and Evaluation of Some Bioactive Compounds Extracted from Squilla (Oratosquilla massavensis) Shells
Abouzeed A. S.
,
Omayma E. Shaltout
,
Ibrahim S. M.
,
Attia. R. S.
,
Aboul-yazeed A. M.
Issue: Volume 3, Issue 6-1, November 2015
Pages: 38-44
Received: 9 September 2015
Accepted: 10 September 2015
Published: 29 November 2015
DOI:
10.11648/j.ajls.s.2015030601.16
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Abstract: This work was performed to investigate the production and physicochemical properties of some bioactive compounds (chitin, chitosan and astaxanthin) extracted from squilla (Oratosquilla massavensis) shells. Chemical composition of squilla shells and chitin yield were determined. Results showed that pre-treated squilla shells contained 68.11% moisture, 12.88% true protein, 4.79% crude fat and 44.59% ash content (on dry weight). Chitin yield and its ash content ranged between 15.75–16.08% and 0.81–1.26%, respectively. The physicochemical properties of chitosan at different times and temperatures showed that chitosan composed 8.73–11.19% moisture, 0.66–0.83% true protein, 0.14 - 0.25% ash content. Viscosity of chitosan at higher temperatures (120°C and 130°C) for different times (30 min and 60 min) were significantly (P˂0.05) lower (80-111cps) than the lower temperatures (100°C and 110°C) for 60 min (138-130cps). At 120°C and 130°C, for 30 min, solubility was significantly lower (93.5-95.6%) than all other temperatures and times used. The degrees of deacetylation (DD) were significantly different at 130°C for 30 min and 60 min than all other temperatures and times used being higher than 70 % and ranged 73.11%-84.68%. Average molecular weight (MW) of chitosan at 120°C for 30 min was significantly different than all times and temperatures used except 120°C for 60 min and as high as 130°C for 60 min. Thus, it is obvious that MW ranged 180-189 Kilo Dalton was significantly different than lower Mw value (134.8 KD). A high value of water binding capacity (WBC) was found at 120°C for 60 min while fat binding capacity was found at 120°C for 30 min and 60 min compared with other treatments. Concerning the carotenoids, it was found that the astaxanthin in female gonads exhibited higher carotenoid concentration (14.01µg\g) than the shells (10.10µg\g on wet weight). In conclusion, squilla shells are highly prized as an inexpensive market value which could be converted into a valuable expensive chitosan and female gonads are considered a good source for carotenoids, particularly astaxanthin.
Abstract: This work was performed to investigate the production and physicochemical properties of some bioactive compounds (chitin, chitosan and astaxanthin) extracted from squilla (Oratosquilla massavensis) shells. Chemical composition of squilla shells and chitin yield were determined. Results showed that pre-treated squilla shells contained 68.11% moistur...
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Histopathological Studies on Trichodinosis of Farmed Oreochromis niloticus
Mohamed Arafa Adly
,
Mohamed Abdelaziz Ahmed Abd El-Galil
,
Fayza M. Soliman
,
Fatma El Zahraa A. A. Ahmed
Issue: Volume 3, Issue 6-1, November 2015
Pages: 30-37
Received: 27 August 2015
Accepted: 13 September 2015
Published: 29 November 2015
DOI:
10.11648/j.ajls.s.2015030601.15
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Abstract: The present study was planned to study the trichodinosis in the farmed freshwater fish Oreochromis niloticus and investigate the histopathological alterations on the skin and gills. The diseased fish had signs of irritation in the form of erratic swimming, swimming near borders, scratching against hard objects, detached scales, excessive and turbid mucus and ulcerations; and signs of asphyxia in the form of rapid operculum movement, surfacing and piping or gasping. Histopathological examination using light microscopy on the skin of O. niloticus with moderate trichodinosis infection revealed detachment of the epidermis and disarrangement of the collagen bundles in dermis. Heavy infections caused sloughing of the epidermis and the remaining dermis had disarranged collagen bundles and was infiltrated with melanin- carrying cells, forming a thick dark band. Scanning electron micrographs of infected skin surface showed cracked and irregular thickness of squamous epithelium at the whole surface with erosions and marked ulcerations. Histopathological examination using light microscopy on gills of O. niloticus with moderate trichodinosis infection revealed erosions in the epithelial lining cells of the secondary lamellae, causing thinning of their peripheral portions. Heavy infections caused hyperplasia and an intense lamellar epithelial lifting. Scanning electron micrographs of gill arches showed the gill filaments with irregular thickness at their whole lengths. Moreover, filamentary and lamellar surfaces were cracked, spotted and had small notches due to the crawling movement of the Trichodina parasites.
Abstract: The present study was planned to study the trichodinosis in the farmed freshwater fish Oreochromis niloticus and investigate the histopathological alterations on the skin and gills. The diseased fish had signs of irritation in the form of erratic swimming, swimming near borders, scratching against hard objects, detached scales, excessive and turbid...
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Evaluation of Growth Performance of Nile Tilapia Oreochromis niloticus niloticus Fed Piophila casei Maggot Meal (Magmeal) Diets
Ahmed E. Ali
,
Mohamed I. Mekhamar
,
Ali G. Gadel-Rab
,
Alaa G. M. Osman
Issue: Volume 3, Issue 6-1, November 2015
Pages: 24-29
Received: 23 July 2015
Accepted: 24 July 2015
Published: 2 September 2015
DOI:
10.11648/j.ajls.s.2015030601.14
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Abstract: A relatively new approach is the use of insects as a source of animal protein in fish nutrition. Houseflies larvae utilise decaying organic waste to produce animal protein and the larvae can be used to produce a meal (magmeal). Interestingly study of the use of magmeal as substitute for fish meal in fish diets have increased in recent times. In the present work, a feeding trial was conducted to evaluate the potential of housefly maggot meal (magmeal) as a protein source for Nile tilapia ( Oreochromis niloticus niloticus ). The results of the present study revealed that all the experimental diets were accepted by O. niloticus niloticus. This implies that the different experimental feed ingredients did not affect the palatability of the diets. The good overall growth performances and no mortality obtained in both experimental group of this study confirm the suitability of chosen nutritional composition for tilapia. FCR values below 1 have been reported here, indicating the most efficient utilisation of food by Oreochromis niloticus niloticus . The fish fed on maggot diet exhibited a higher K value compared to those fed on commercial diet. The results suggested that dietary maggot meal promoted the growth of Nile tilapia and enhanced nutrient utilization which is reflected in improved length gain, weight gain, FCR, and SGR. Progressive increment in length gain, weight gain and SGR were observed in maggot meal based diet, recording better growth than commercial based diet, concluding that maggot diet has the best performance. Based on the result obtained from the experiment, it is hereby recommended that 100% maggot meal can be included in the diet of O. niloticus nilotcus to reduce cost and maximize profit.
Abstract: A relatively new approach is the use of insects as a source of animal protein in fish nutrition. Houseflies larvae utilise decaying organic waste to produce animal protein and the larvae can be used to produce a meal (magmeal). Interestingly study of the use of magmeal as substitute for fish meal in fish diets have increased in recent times. In the...
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A Key for Identification of Spiders at Qena Governorate, Upper Egypt
Ahmad H. Obuid-Allah
,
Amal A. Mahmoud
,
ElAmier H. M. Hussien
Issue: Volume 3, Issue 6-1, November 2015
Pages: 13-23
Received: 21 July 2015
Accepted: 22 July 2015
Published: 2 September 2015
DOI:
10.11648/j.ajls.s.2015030601.13
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Abstract: Spiders are one of the more diverse arthropod taxa, ranking seventh in global diversity, which makes them a fascinating group to study [1]. The correct identification of many spider species is considered problematic due to complex variation in morphology [2]. The Egyptian spider fauna are incompletely known due to scarcity of studies on this group especially in Upper Egypt. So, the present key for identifying terrestrial spiders at Qena Governorate is a part of a comprehensive study conducted at the region to study the ecology and taxonomy of this group. The present key was designed to facilitate identification of terrestrial spiders at Qena Governorate using their morphological characteristics. Samples of spiders were collected during a period of one year (from February, 2012 till January, 2013) from six different sites covering Qena governorate. Qena (15-260 N, 32-500 E) is located at Upper Egypt about 600 Km south of Cairo and 60 Km north of Luxor and 260 Km west of the Red Sea. Climate of Qena is hot, dry in summer and cold in winter. It rarely rains. Also, it receives a large quantity of solar radiation; especially in summer. Sampling methods of spiders included hand picking, sweep net and pitfall trap. Survey results revealed the occurrence of 14 families that included 23 genera and 23species. The present key for the collected families and species was designed and illustrated using taxonomic characteristics of each species.
Abstract: Spiders are one of the more diverse arthropod taxa, ranking seventh in global diversity, which makes them a fascinating group to study [1]. The correct identification of many spider species is considered problematic due to complex variation in morphology [2]. The Egyptian spider fauna are incompletely known due to scarcity of studies on this group ...
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Age and Growth of the Areolate Grouper Epinephelus areolatus from the Gulf of Suez
Ezzat Abd-Allah
,
Azza El-Ganainy
,
Alaa Osman
Issue: Volume 3, Issue 6-1, November 2015
Pages: 7-12
Received: 5 July 2015
Accepted: 6 July 2015
Published: 2 September 2015
DOI:
10.11648/j.ajls.s.2015030601.12
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Abstract: Age and growth of the associated coral reef grouper, Epinephelus areolatus, were estimated for samples collected from the artisanal fishery in the Gulf of Suez during November 2013 and October 2014. Otoliths of 597 specimens ranged in length from 11.2 to 50.5 cm were used in age determination. The otoliths showed alternating opaque (light) and translucent zones when seen by reflected light against a dark background, a translu¬cent zone plus the opaque zone immediately around it formed an annulus. According to the otolith examination, the maximum life span of E areolatus was eight years with mean lengths of 16.9, 24, 29.9, 35.7, 39.7, 43.4, 46.6 and 49.7 cm for the age groups from one to eight respectively. Individuals belong to age group two constituted the bulk of the catch with more than 60% of the population. The results showed that the E. areolatus is a relatively slow growing species and the values of the von Bertalanffy growth function was estimated as K = 0.154, L∞ = 66.55 cm (LT) and t0 = −0.91 years. The estimated growth performance index is 2.83. The length weight relationship was estimated as a = 0.0135 and b = 2.9947, r2 =0.981 indicating an isometric growth of the weight relative to the length.
Abstract: Age and growth of the associated coral reef grouper, Epinephelus areolatus, were estimated for samples collected from the artisanal fishery in the Gulf of Suez during November 2013 and October 2014. Otoliths of 597 specimens ranged in length from 11.2 to 50.5 cm were used in age determination. The otoliths showed alternating opaque (light) and tran...
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Age, Growth and Demographic Structures of Thorny Flathead Rogadius asper, Cuvier, 1829 (Pieces: Platycephalidae) from the Coastal Waters of the Suez Gulf
Manal Sabrah
,
Amal Amin
,
Aly El Sayed
Issue: Volume 3, Issue 6-1, November 2015
Pages: 1-6
Received: 30 June 2015
Accepted: 22 July 2015
Published: 2 September 2015
DOI:
10.11648/j.ajls.s.2015030601.11
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Abstract: The age and growth of the Olive tail Rogadius asper exploited by the demersal trawl fishery in the Gulf of Suez were investigated during the fishing season 2014/2015. Ageing was done by sagittal otoliths for a sample of 675 ranged from 9.2 to 25.9 cm in total length (TL) with mean of 17.4±2.95 cm. The sex ratio was skewed in favors of females (1.6:1), which tended to high in number and bigger in size than males. The maximum investigated age of females was 4 years and that of males was 3 years. The mean von Bertalanffy growth parameters for both sexes L∞= 26.43±0.22cm and K=0.47±0.03year-1 as estimated by four different methods. According to gender the growth was variable and significantly differed (P˂0.05=0.002). Females attained a greater mean L∞= 27.2±0.44cm than males L∞=24.0±0.26 cm and males displayed greater mean k value 0.53±0.02 year-1 than that of females K=0.43±0.01 year-1. Fish of age groups 1 and 2 years were dominated the age compositions of R. asper constituting 36.6% and 39.3 % respectively. The estimated value of total mortality, natural mortality and fishing mortality for the pooled data was: Z= 1.51±0.25, 0.58±0.09 and 0.93±0.08 year-1 respectively. It was indicated that the fishing mortality was more than one third (37.6%) of the derived natural mortality and exploitation rate was 0.62, indicating that the species was heavily exploited. Although R. asper is not a target species of commercial fisheries, it suffers high exploitation as part of the by-catch for its suitable market price for insufficient income.
Abstract: The age and growth of the Olive tail Rogadius asper exploited by the demersal trawl fishery in the Gulf of Suez were investigated during the fishing season 2014/2015. Ageing was done by sagittal otoliths for a sample of 675 ranged from 9.2 to 25.9 cm in total length (TL) with mean of 17.4±2.95 cm. The sex ratio was skewed in favors of females (1.6:...
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