Papers by elazab elbokhty
Egyptian Journal of Aquatic Biology and Fisheries, 2020
Due to anthropogenic disturbance, many natural aquatic resources have suffered severe decline in ... more Due to anthropogenic disturbance, many natural aquatic resources have suffered severe decline in abundance and yields, and some have even been driven to the point of collapse (Lorenzen et al., 2016). Lake Manzala is considered one of the most important lakes in Egypt It represents 32% of the lakes fish production in Egypt and 44% of the ARTICLE INFO
Egyptian Journal of Aquatic Biology and Fisheries, 2012
Evaluation of Oreochromis aureus caught from Lake Borollus was studied based on the length-freque... more Evaluation of Oreochromis aureus caught from Lake Borollus was studied based on the length-frequency of samples collected by different fishing gears. Analysis of the data using (FiSAT) computer program returned the estimate of the von Bertalanffy's growth curve parameters as: L ∞ = 18.28 cm (total length); k = 0.87 year-1 (for Lokaffa), L ∞ = 19.32 cm; k = 0.41 year-1 (for Trammel), L ∞ = 17.19 cm; k = 0.42 year-1 (for Basket traps) and L ∞ = 14.55 cm, K=0.39 year-1 (for Al-qerba). Very narrow selection range was observed and its upper limit didn't exceed 11.53 cm in most of the investigated fishing gears except that of trammels which reached 12.11 cm. The total mortality coefficient "Z" was found to be 3.05, 1.83, 1.46, and 1.58 year-1 corresponding the fore-mentioned fishing methods respectively. Also, their respective natural mortality coefficient "M" was 1.67, 1.01, 1.06, and 1.06 year-1. The estimated exploitation rate "E" was 0.45, 0.45, 0.28 and 0.33 respectively. Their relative yield and relative biomass per recruit analysis showed that the stock of O. aureus is moderately exploited and more effort could be added to reach the maximum sustainable yield and at the same time larger mesh sizes of fishing nets should be used to increase the mean lengths at first capture and also to conserve the reproducible part of O. aureus population.
Egyptian Journal of Aquatic Biology and Fisheries
The present research was carried out during Autumn 2016 with the aim of studying the technical an... more The present research was carried out during Autumn 2016 with the aim of studying the technical and design characteristics of the widely used trammel nets in Lake Manzalah, as an attempt to be one of a data base that describe the different fishing gears used in Egypt. A number of net units were randomly used as samples. Results showed that such nets are used in collaboration with small fishing wooden boats (canoes) reinforced with a layer of fiber glass of the third class with an average number of 2 men. The dimensions of trammel net unit ranged between 20 and 25 meter long and a height of 0.5 to 1 meter. Trammel nets are formed of three netting panels, the stretched mesh size of the middle layer averaged # 40.82 mm while that of the outer layer was 125.24 mm. The upper and lower ropes were locally made of 3-strand staple fibers. Small sized cork floats were mounted on the upper rope (av. # 3 / 1 m) and lead sinkers to the lower rope (av. # 5-6 piece / m) of a total weight of 2-3 Kg per net unit. The netting materials were of polyamide monofilament of an average diameter (ɸ) 0.126 mm for the inner layer and ɸ 0.22 mm for the outer one. The horizontal hanging coefficients ranged between 0.60 and 0.70 for the outer layers and between 0.40 and 0.55 for the inner one. The results showed that such nets don't match the criteria for catching moderately sized fish (Average length 15 cm) of tilapia especially the mesh opening of the inner layer for conserving the fishery stocks and sustainable fishery.
Egyptian Journal of Aquatic Biology & Fisheries Zoology Department, Faculty of Science, Ain Shams University, Cairo, Egypt. , 2017
ABSTRACT
The present research was carried out during Autumn 2016 with
the aim of study... more ABSTRACT
The present research was carried out during Autumn 2016 with
the aim of studying the technical and design characteristics of the
widely used trammel nets in Lake Manzalah, as an attempt to be one
of a data base that describe the different fishing gears used in Egypt.
A number of net units were randomly used as samples. Results
showed that such nets are used in collaboration with small fishing
wooden boats (canoes) reinforced with a layer of fiber glass of the
third class with an average number of 2 men. The dimensions of
trammel net unit ranged between 20 and 25 meter long and a height
of 0.5 to 1 meter. Trammel nets are formed of three netting panels,
the stretched mesh size of the middle layer averaged # 40.82 mm
while that of the outer layer was 125.24 mm. The upper and lower
ropes were locally made of 3- strand staple fibers. Small sized cork
floats were mounted on the upper rope (av. # 3 / 1 m) and lead
sinkers to the lower rope (av. # 5 – 6 piece / m) of a total weight of
2-3 Kg per net unit. The netting materials were of polyamide
monofilament of an average diameter (ɸ) 0.126 mm for the inner
layer and ɸ 0.22 mm for the outer one. The horizontal hanging
coefficients ranged between 0.60 and 0.70 for the outer layers and
between 0.40 and 0.55 for the inner one. The results showed that
such nets don't match the criteria for catching moderately sized fish
(Average length 15 cm) of tilapia especially the mesh opening of the
inner layer for conserving the fishery stocks and sustainable fishery.
The present research was carried out during Autumn 2016 with the aim of studying the technical an... more The present research was carried out during Autumn 2016 with the aim of studying the technical and design characteristics of the widely used trammel nets in Lake Manzalah, as an attempt to be one of a data base that describe the different fishing gears used in Egypt. A number of net units were randomly used as samples. Results showed that such nets are used in collaboration with small fishing wooden boats (canoes) reinforced with a layer of fiber glass of the third class with an average number of 2 men. The dimensions of trammel net unit ranged between 20 and 25 meter long and a height of 0.5 to 1 meter. Trammel nets are formed of three netting panels, the stretched mesh size of the middle layer averaged # 40.82 mm while that of the outer layer was 125.24 mm. The upper and lower ropes were locally made of 3-strand staple fibers. Small sized cork floats were mounted on the upper rope (av. # 3 / 1 m) and lead sinkers to the lower rope (av. # 5 -6 piece / m) of a total weight of 2-3 Kg per net unit. The netting materials were of polyamide monofilament of an average diameter (ɸ) 0.126 mm for the inner layer and ɸ 0.22 mm for the outer one. The horizontal hanging coefficients ranged between 0.60 and 0.70 for the outer layers and between 0.40 and 0.55 for the inner one. The results showed that such nets don't match the criteria for catching moderately sized fish (Average length 15 cm) of tilapia especially the mesh opening of the inner layer for conserving the fishery stocks and sustainable fishery.
Evaluation of Oreochromis niloticus caught from LakeBorollus was studied based on the length-freq... more Evaluation of Oreochromis niloticus caught from LakeBorollus was studied based on the length-frequency samples collected by different fishing gears. Analysis of the pooled data using (FiSAT) computer program returned the estimate of the von Bertalanffy's growth curve parameters as: L = 26.29 cm (total length); k = 0.81year. Very narrow selection ranges were observed and recorded corresponding to the 1 different fishing gears. The total mortality coefficient "Z" was found to be 3.43 year. Also, the invariant 1 measure of effort, the fishing rate (F), was estimated to be 1.99 year. The estimated exploitation rate "E" was 1 0.58 which coincides with the maximum exploitation as revealed by Beverton and Holt's model. Their relative yield and relative biomass per recruit analysis showed that the stock of O. niloticus is over exploited. Howbeit, larger mesh sizes of fishing nets should be used to increase the mean lengths at first capture and their marketable sizes leading to more economic returns and also to conserve the spawning stock part of O. niloticus population instead of lowering the effort exerted which seems to be difficult to apply due to the social concerns of fishermen.
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Papers by elazab elbokhty
The present research was carried out during Autumn 2016 with
the aim of studying the technical and design characteristics of the
widely used trammel nets in Lake Manzalah, as an attempt to be one
of a data base that describe the different fishing gears used in Egypt.
A number of net units were randomly used as samples. Results
showed that such nets are used in collaboration with small fishing
wooden boats (canoes) reinforced with a layer of fiber glass of the
third class with an average number of 2 men. The dimensions of
trammel net unit ranged between 20 and 25 meter long and a height
of 0.5 to 1 meter. Trammel nets are formed of three netting panels,
the stretched mesh size of the middle layer averaged # 40.82 mm
while that of the outer layer was 125.24 mm. The upper and lower
ropes were locally made of 3- strand staple fibers. Small sized cork
floats were mounted on the upper rope (av. # 3 / 1 m) and lead
sinkers to the lower rope (av. # 5 – 6 piece / m) of a total weight of
2-3 Kg per net unit. The netting materials were of polyamide
monofilament of an average diameter (ɸ) 0.126 mm for the inner
layer and ɸ 0.22 mm for the outer one. The horizontal hanging
coefficients ranged between 0.60 and 0.70 for the outer layers and
between 0.40 and 0.55 for the inner one. The results showed that
such nets don't match the criteria for catching moderately sized fish
(Average length 15 cm) of tilapia especially the mesh opening of the
inner layer for conserving the fishery stocks and sustainable fishery.
The present research was carried out during Autumn 2016 with
the aim of studying the technical and design characteristics of the
widely used trammel nets in Lake Manzalah, as an attempt to be one
of a data base that describe the different fishing gears used in Egypt.
A number of net units were randomly used as samples. Results
showed that such nets are used in collaboration with small fishing
wooden boats (canoes) reinforced with a layer of fiber glass of the
third class with an average number of 2 men. The dimensions of
trammel net unit ranged between 20 and 25 meter long and a height
of 0.5 to 1 meter. Trammel nets are formed of three netting panels,
the stretched mesh size of the middle layer averaged # 40.82 mm
while that of the outer layer was 125.24 mm. The upper and lower
ropes were locally made of 3- strand staple fibers. Small sized cork
floats were mounted on the upper rope (av. # 3 / 1 m) and lead
sinkers to the lower rope (av. # 5 – 6 piece / m) of a total weight of
2-3 Kg per net unit. The netting materials were of polyamide
monofilament of an average diameter (ɸ) 0.126 mm for the inner
layer and ɸ 0.22 mm for the outer one. The horizontal hanging
coefficients ranged between 0.60 and 0.70 for the outer layers and
between 0.40 and 0.55 for the inner one. The results showed that
such nets don't match the criteria for catching moderately sized fish
(Average length 15 cm) of tilapia especially the mesh opening of the
inner layer for conserving the fishery stocks and sustainable fishery.