Trawl Codend Research Articles

Non-linear dynamic behavior of T0 and T90 mesopelagic trawls based on the Hilbert–Huang transform

Although adopting the T90 mesh orientation on the trawl net can improve the selectivity of the trawl codend, it is unknown whether the T90 mesh orientation influences the dynamic behavior of the trawl system. Therefore, this study uses non-linear dynamic analysis to examine the effect of mesh orientations, mesh size, and twine diameter on the mesopelagic trawls' fluttering motions and hydrodynamic force responses. Three trawls are designed with different mesh orientations (T0 and T90), mesh sizes (40 mm and 60 mm), and twine diameters (0.96 mm and 1.11 mm) on the codend and codend extension sections of the trawl model based on Tauti's law. These trawls are tested in a flume tank under various flow velocities and catch sizes. A time-frequency analysis method based on the Hilbert–Huang transform is utilized to analyze each trawl's dynamic responses, including motions and drag force responses. The results are compared with those obtained through Fourier analysis using power spectral density. The results highlight that the oscillation amplitude of the surge motion of the T90 trawl is higher than that of the T0 trawl. In contrast, the T90 trawl's heave motion oscillation amplitude is smaller. The dominant frequency of the periodic high-energy coherent structures of the surge and heave motions are detected at a low frequency. The surge and heave motions of the T0 trawl have a greater response to the current components with lower frequencies than that of the T90 trawl. An increase in mesh size, a decrease in twine diameter, and a change in mesh orientation decrease the drag force. The inherent characteristic oscillations of the drag force response for the three trawl models are synchronized with the low-frequency characteristic of surge and heave motions. The gravity periods of the low-frequency mode components of drag force, surge motion, and heave motion for the T90 trawl are higher than those for the T0 trawls. In other words, the T90 trawl is more stable and selective than the T0 trawl. The findings of this study offer important information for comprehending and enhancing the selectivity of trawls in marine mesopelagic fisheries, particularly for exposing the effects of mesh orientation and design parameters on trawl performances.

The Oscillating Behavior of Trawl Codends Including Various Geometric Configurations of Simulated Catch

Codends are the posterior components of trawl nets that collect the catch and play a crucial role in the selectivity process. Due to the accumulation of catch and the variety of catch types, the quality of catch and trawl selectivity can be negatively impacted. Therefore, this study aims to investigate the effects of various catch configurations on the hydrodynamic characteristics, geometrical profile, and fluttering motions of the codend in a flume tank. A codend structure was designed and tested using various catch configurations, including grooved-type configurations (canvas, green canvas, basketballs) and spherical configurations (table tennis balls filled with water, balloons filled with water, and balls made of twine) in the flume tank. The sea trial data were compared with the flume tank data. The results indicate that there were no significant differences in the codend profiles between the different catch configurations. The drag of the codend with a grooved-type configuration was 13.63% greater than that obtained using a spherical configuration as the catch. The wavelet coefficient obtained from the codend drag revealed that the oscillations of the codend with a grooved-type catch configuration began at a periodicity of 0.07 s and were more intense than that of the codend with the spherical catch configuration. Moreover, these amplitudes increased as the codend flow velocity increased. The wavelet analysis results showed that the dominant frequency of the periodic high-energy coherent structures for the codend drag and codend displacements was detected at a low-frequency. In terms of displacement oscillation characteristics, the table tennis ball filled with water was an approximate substitute for real catch during the sea trial because the difference in wavelet coefficients for the codend displacements in amplitude and the period between the model codend with the table tennis ball filled with water and the full-scale codend was 91% and 89%, respectively. The findings of this study confirm the feasibility of replacing real catch with simulated catch configurations with similar shapes in model testing. They can provide basic scientific data for improving the hydrodynamic characteristics and selectivity of the codend structure.

Escape Survival and Scale Damage Assessment of Red Mullet (Mullus barbatus Linnaeus, 1758) during Bottom Trawling in the Central Mediterranean Sea.

Stock assessments routinely evaluate the status of commercially harvested species, but seldom account for the possible mortality of released or escaping fish. This study presents a method for estimating the escape survival of the red mullet (Mullus barbatus) from demersal trawling in the Central Mediterranean Sea. Fish escaping from the trawl codend were collected in a detachable cage, which was lined to reduce water flow and protect the sampled fish from further fatigue and injury. Control fish (from an open codend) showed high survival, 94% (87-97%, 95% Confidence Interval), and minimal injuries, while fish escaping through codend meshes had significantly increased injuries and reduced survival, 63% (55-70%). During 7 days of captive monitoring, treatment group mortality was highest in the first 24 h and ceased for both groups within 48 h. Conflicting length-related mortality was observed, where larger treatment fish had a higher probability of dying, while the opposite was observed in the controls. Analysis showed that treatment fish were significantly more injured than control fish, with treatment fish predominantly injured in the head zone. In conclusion, this improved methodology should be repeated to provide accurate escape mortality estimates for the improved stock assessment of the red mullet in the Central Mediterranean.

The capability of square-meshes and fixed-shape meshes to control codend size selection

Trawl codends are commonly made of diamond-mesh netting. However, diamond-mesh codends vary in mesh geometry along its length and during fishing due to catch build up. This introduces variability in the size selection process. This phenomenon compromises the rationality of regulating exploitation patterns in trawl fisheries through adjustments in codend mesh size. One technical solution often applied to achieve more well-defined size selection is turning the codend netting 45 degrees (square-mesh). However, there is a lack of evidence that square-mesh codends result in more constant size selectivity. Therefore, we aimed at quantifying the variability in size selection in square-mesh codends. We tested the size selectivity of three codends; a standard square-mesh codend, and two rigid codends where mesh geometries were fixed in diamond shape with an opening angle of 60° and square shape, respectively. The two rigid codends were used to establish baselines with limited variability in size selection. The size selectivity of these codends was compared to results - previously obtained for a standard diamond-mesh codend. Using Atlantic cod (Gadus morhua) as a case study, we demonstrated that the standard square-mesh codend had significantly larger variability in size selection compared to the fixed diamond-mesh codend. Moreover, we found no evidence that the standard square-mesh codend had lower variability in size selection than a standard diamond-mesh codend with same mesh size. These results demonstrate that the use of standard square-mesh codends is not sufficient to reduce variability in codend size selection. Additionally, we demonstrate that the sizes of fish retained is strongly dependent on mesh shape and openness. We conclude that a profound re-thinking over codend designs is required in order to achieve better control of size selection in trawl fisheries.

Catch Composition of Different Bottom Trawl Cod-ends in the Western Black Sea

Catch Composition of Different Bottom Trawl Cod-ends in the Western Black Sea

Impacts on biodiversity from codend and fisher selection in bottom trawl fishing

Fisheries have important impacts on marine biodiversity. In this work, combined information on the abundance, species richness, diversity indices, species composition, trophic level and vulnerability index were examined for the first-time to detect differences in five units related to trawl fishing: the fish assemblage entering the trawl codend, and the escaping, retained, discarded and landed fractions, derived by the gear and fisher selection practices. The work was based on a case study conducted in the Mediterranean Sea, using three different meshes in the trawl codend (40mm-40D and 50mm-50D diamond meshes, and 40 mm-40S square meshes) and a cover of the codends with small mesh size. In general, trawl fishing produces an escaping fraction that was always lower in abundance, richness, and vulnerability index, similar in diversity indices and trophic level, and different in species composition compared to the fish assemblage entering the codend. In almost all cases, fishers selected as landings a fraction that was the lowest in diversity indices, and the highest in trophic level. In contrast, fishers discarded a fraction that was the highest in diversity and vulnerability index, and the lowest in trophic level. Although the three codends did not differ significantly in the fraction of escapees in terms of diversity indices, trophic level, and vulnerability index, the 40S codend showed a significantly higher percentage in the escaping number of species and individuals, and less differences in the species composition; in addition, lower percentage in abundance of discards and higher of landings in the retained catch (0.6:1) than did the other two codends (0.9:1). It was suggested that an urgent modification of the trawl for the elimination of the discarded highly vulnerable species (e.g. Elasmobranchs) is needed, and that trawl species-selectivity should be improved by allowing escape or avoiding catch of the discarded fraction to minimize biodiversity losses.

Escape of hake (Merluccius merluccius), horse mackerel (Trachurus trachurus) and blue whiting (Micromesistius poutassou) in codends with shortened lastridge ropes

Diamond meshes in trawl codends have limited openness, which reduces escape opportunities for roundfish. Shortening the lastridge ropes (LR) attached to codend selvedges can increase the availability of open meshes resulting in higher chances of escape. However, this availability does not imply optimal mesh openness, nor does it guarantee use. We estimate the escape probability of hake, horse mackerel and blue whiting through a 20% shortened LR codend and a standard codend, and quantify the contribution of different mesh opening angles (OAs) to their size selectivity. The results confirm that high OAs increase escape opportunities for all species. However, shortened LR only improved size selectivity significantly for horse mackerel and blue whiting. This difference between species may be related to behavioural differences. The mesh openness achieved with 20% shortened LR was below that necessary to obtain optimal escape opportunities for these species. The study highlights the relevance of considering fish morphology and behaviour to optimally exploit size selectivity when designing shortened LR codends.

Validating a narrow codend cover and improving selectivity in south-eastern Australian fish trawls targeting eastern school whiting, Sillago flindersi

As part of attempts to improve selection among south-eastern Australian benthic fish trawls, an experiment was done to assess: (1) for confounding effects of a narrower-than-recommended hooped cover over a conventional trawl codend; and then (2) the associated size selection of eastern school whiting, Sillago flindersi; and (3) if this could be improved by inserting a large panel of smaller square-shaped mesh. The narrow cover was required to avoid contacting the seabed and did not affect trawl wing-end spread or catching efficiency. Despite a stretched mesh opening (SMO) of 96 mm and much larger than all S. flindersi (11–26 cm total length; TL), the conventional codend had a low 50% size at retention (L50) of 16.8 cm TL (selection range of 5.9 cm), which was close to the minimum marketable length. The capture of small S. flindersi by the large-meshed codend was attributed to an excessive increase in circumference (from 100 to 200 meshes) and a legally permitted ‘catch-separating’ rope to restrict fractional mesh openings to <~21%. Replacing ~1/4 of the 96-mm SMO netting in the codend and anterior extension with a panel of square-shaped mesh (~42-mm SMO hung on the bar) marginally (p = 0.065) improved size selection for S. flindersi (by allowing some fish <~15 cm TL to escape). Increasing the size of mesh in the panel to ~47 mm hung on the bar might allow more smaller S. flindersi to escape. But using a smaller mesh size throughout the entire codend, concurrent with other gear or spatio-temporal controls when targeting S. flindersi might be a more coherent management option than retroactively handicapping the existing large-mesh codends.

Estimating overall size-selection pattern in the bottom trawl fishery for four economically important fish species in the Mediterranean Sea

The management of multispecies fisheries, such as the Mediterranean bottom trawl fishery, is always a challenge. However, information on gear selectivity and discards has been studied separately so far. In this paper, the overall size-selection pattern by the trawl codend in the sea and by the fisher onboard the vessel is investigated for four commercially important fish species, Mullus barbatus, Mullus surmuletus, Pagellus erythrinus and Lophius budegassa, using different codends. For each species, the selection model used offered the possibility to simultaneously describe the escape, discard, and landing probability. The results, useful for fisheries management, showed that the codend made of 40 mm diamond meshes was always detrimental for the stocks. The 40 mm square meshes codend compared to that of 50 mm diamond meshes was more appropriate for the sustainability of both Mullus species, providing also a lawful catch along with greater compliance to the rules fisher behaviour, negligible discards and the lowest possible economic losses for the fisher. None of the codends was effective for P. erythrinus in achieving the minimum conservation reference size (MCRS) of the species. All codends were harmful to L. budegassa as the majority of juveniles were retained in the codend, resulting in negligible escapees, a high discard probability, and landings of a size much lower than the length at first maturity of the species. Further studies are needed to be conducted in the future for other species, since the trawl fishery in the Mediterranean is a multi-species fishery.

Selectivity estimates for Sepiella inermis (Van Hasselt, 1835) in 40 mmdiamond mesh codend trawl net

Cephalopods are mostly targeted by trawlers and Sepiella inermis (spineless cuttlefish), contributes about 2-4 percent oftotal cephalopod landings in India. Cephalopods accounted for 6.9 percent of total landings in Gujarat in 2018, with S.inermis accounting for approximately 1 %. The most common length of this species in the fishery is between 35 mm to 147mm. The length at first sexual maturity varies along the coast, and recent estimates for west coast of India for this species is48 and 55 mm for males and females, respectively.There are no estimates of trawl codend selectivity for this species and experiments were carried out using a 40 mmdiamond mesh codend using covered codend method. The selection parameters for S. inermis were derived using SELECTmethodology and the length at 50 % retention (L50)±(s.e.) was worked out as 36.2±1.2 mm and selection range as 19.9±2.1mm. The selection factor and the selection ratio for the codend were worked out as 0.9 and 0.55, respectively. The suggestedmesh size for the codend based on length at first sexual maturity (LFM) of females (55 mm) and males (48 mm) wereestimated as 60 and 53 mm (diamond mesh), respectively. This is the first estimate of trawl selection for this species andoperational parameters like towing speed, codend catch etc., that could influence selectivity were not considered and hencemore studies by incorporating these factors will help in further refining the parameters of the selection curve.

Effect of Cutting Ratio and Catch on Drag Characteristics and Fluttering Motions of Midwater Trawl Codend

The codend of a trawl net is the rearmost and crucial part of the net for selective fish catch and juvenile escape. To ensure efficient and sustainable midwater trawl fisheries, it is essential to better understand the drag characteristics and fluttering motions of a midwater trawl codend. These are generally affected by catch, cutting ratio, mesh size, and twine diameter. In this study, six nylon codend models with different cutting ratios (no cutting, 6:1, 5:1, 4:1, 7:2, and 3:1) were designed and tested in a professional flume tank under two conditions (empty codends and codends with catch) and five current speeds to obtain the drag force, spatial geometry, and movement trend. As the cutting ratio of empty codends decreased, the drag force decreased, and the drag coefficient increased. The unfolding degree of codend netting and the height of empty codends were found to be directly proportional to the current speed and inversely proportional to the cutting ratio. The positional amplitude of codend with cutting ratio 4:1 was the smallest for catch. The drag force of codends with catch increased as the current speed increased, and first decreased and then increased as the cutting ratio decreased. To ensure the best stability and minimum drag force of the codend, it is recommended to use the 4:1 cutting ratio codend.

The Cost of Fishing on Juveniles of Finfish and Shellfish: Assessment of Economic Impacts of Trawl Juvenile by-Catch along the Coast of North Andhra Pradesh, India

A study was carried out to assess the economic value of juveniles of commercially important species of finfish and shellfish caught as by-catch by multiday commercial trawlers operated off the coast of Visakhapatnam, north Andhra Pradesh from January 2014 to December 2015. Juveniles of twenty species (four species of cephalopods and sixteen species of finfish) were found to dominate the trawl by-catch. The landed juveniles of these 20 species formed 12,757.16 t and 286.86 million numbers per year and their contribution to the total landings of these species in trawl by-catch were 55.30% by weight and 57.03% by numbers. The highest percentage of quantities of juveniles (biomass) was found in trawl by-catch in the months of August and July in, 2014 and 2015 respectively. Among the juveniles, ribbonfish (Trichiurus lepturus) and goatfish (Upeneus vittatus) dominated, contributing together, on an average 11.60% by weight and 33.68% by numbers respectively. Using the bio-economic model, it was estimated that if the juveniles were allowed to grow up to length at first maturity; total annual economic gain would have been Rs. 273.21 crores (42.03 million USD) with biomass gain of 44,493.02 t per annum. The estimated total annual biomass would have increased 3.46 times with an increase in revenue by 4.20 times. Annual average loss due to fishing of juveniles was estimated to be Rs. 209.62 crores (32.25 million USD). The results of the present study suggested that sustainable harvest of these resources would have yielded maximum economic return to the fishers. With the help of stakeholders using a participatory approach, management measures such as increase of cod end mesh size of trawl to 40 mm from the present mesh size of 10–12 mm, use of square mesh for trawl cod ends, fishing effort restriction and awareness campaign on the detrimental impacts of catching juveniles needs to be implemented at the earliest for avoiding growth overfishing.

Improving species and size selectivity in the Baltic cod trawl fishery with two simple codend designs

The eastern Baltic cod (Gadus morhua) stock is at a critically low level and recruitment of the western Baltic cod stock is at the lowest observed level in over 30 years. The EU (European Union) landing obligation was introduced in 2015 for cod and in 2017 for plaice (Pleuronectes platessa). Size selective codend designs have been used in the Baltic cod trawl fishery for 25 years; however, there are still relatively high discard rates for cod, plaice and European flounder (Platichthys flesus; henceforth flounder) in the trawl fishery and landings of individuals below the minimum conservation reference size (MCRS). These problems call for additional improvements of species and size selectivity in the cod trawl fishery. In this study, two trawl codend designs were developed and tested to improve species and size selectivity in the Baltic cod trawl fishery. The codends were tested onboard a commercial trawler and the test codends were compared to the conventional Bacoma codend, which was fished simultaneously in a twin trawl rig. New codend designs were based on the Bacoma design, where the first test codend had a bottom net panel made of larger diamond meshes (nominal 130 mm mesh size) to improve selectivity in a cod fishery with high catch rates of flatfish. This codend showed a reduction of plaice and flounder, and cod below 45 cm, in the catches. The other test codend was a full square mesh codend (nominal 120 mm mesh size) developed for a cod directed fishery with low flatfish catches, and showed a marked reduction in the catch of cod below 50 cm, with no differences for flounder and plaice catches. With cod stocks at critically low levels and relatively high discard rates of cod, plaice and flounder, the simple codend designs tested in this study could benefit the sustainability of the Baltic cod trawl fishery, but with some loss of commercially targeted sizes.

A meta-analysis of plaice size-selection data in otter trawl codends

The influence that mesh size, the number of open meshes around the circumference, twine thickness and catch size have on the size-selection of plaice (Pleuronectes platessa) in otter trawl codends is investigated by synthesising the data from 164 hauls using 25 gear configurations during 9 trips.All these variables have an effect on selection. The 50 % retention length (L50) increases by 1.9 cm for every 10 mm increase of mesh size and decreases by 0.24 cm for every doubling of catch. The selection range decreases by 3.8 % for each increase of 10 open meshes and increases by 12.3 % for each 1 mm increase of twine thickness. The mesh size and twine thickness effects have strong support from the data. The open meshes and catch size effects have less support and should be treated with some caution.There is good correspondence between the predictions of the analysis presented here and the L50 estimates of beam trawl codend selectivity trials, which is noteworthy given the many operational differences between the two fishing methods.

Karadeniz’de Mezgit (Merlangius merlangus euxinus) avcılığındaki trol torba seçiciliklerinin karşılaştırılması

A large part of the total whiting (Merlangius merlangus euxinus) fishing in the Black Sea is carried out with the traditional bottom trawl nets along the coast of Turkey. Diamond mesh shape with 40 mm mesh size (40D) has been used in the codends of these trawls. In this study, the traditional trawl codend (40D) and square-mesh codend with different size (36S and 40S) were compared for whiting size selectivity in August 2014. Selectivity data were collected by using a covered codend method and analysed taking between haul variations in to account. The selectivity parameters were estimated by using CC2000 software. Results showed that commercially used 40D trawl codend is not selective enough to release immature of whiting. However, the net change in square mesh (36S and 40S) instead of a diamond-shaped (40D) mesh significantly improved the mesh selectivity for whiting. The 40S trawl codend is even higher than the first maturity size (LM50) with a length at fifty percent retention (L50) of 15.74 cm. In conclusion all square mesh codends with different mesh size tested here supplied appropriate selection considering minimum landing size (MLS) of whiting.

Can active behaviour stimulators improve fish separation from Nephrops (Nephrops norvegicus) in a horizontally divided trawl codend?

A promising design to improve selectivity in the Nephrops-directed trawl fishery is the horizontally divided trawl codend. Previous studies have succeeded in separating the majority of fish from Nephrops; however, cod (Gadus morhua), juvenile roundfish and flatfish still enter the lower compartment in relative high proportions. In this study we investigated if and to which extent it is possible to improve the vertical separation of fish from Nephrops by adding active behaviour stimulators. These stimulators are designed to exploit fish avoidance behaviour and lead them into the upper compartment while Nephrops move into the lower compartment. We tested two types of behaviour stimulators: a chain curtain at the entrance of the lower compartment at the point of separation and a set of rising float-lines inserted ahead of the point of separation. The length-dependent vertical separation of five important commercial fish species and Nephrops was analysed in comparison to the horizontally divided trawl codend with no stimulator, towed in parallel to the test trawl. The results showed that fish’s vertical separation can be partially improved by the addition of stimulators, without complicating fishing operations or increasing the proportion of Nephrops that enters the upper compartment. However, the improvement was limited and none of the two active stimulators tested managed to simultaneously improve the separation of cod, juvenile roundfish and flatfish.

A game of two halves: Bycatch reduction in Nephrops mixed fisheries

Trawlers that target Nephrops norvegicus and a range of demersal fish species need gear options to reduce bycatch and address European Union landing obligation requirements. We demonstrated how this can be achieved by using inclined panels to separate fish species into an upper codend with 90 mm T90-mesh, and Nephrops norvegicus into a lower codend with 80 mm diamond-mesh. A nested mixed effects model was developed to compare proportional catch at length of key species retained in test or control trawls, and based on this, the conditional probability of retention in the upper and lower test trawl codends. Haddock (Melanogrammus aeglefinus) and whiting (Merlangius merlangus) < minimum conservation reference size (MCRS) were significantly reduced, while haddock ≥ MCRS, Nephrops, cod (Gadus morhua), monkfish (Lophius piscatorius), and commercial flatfish catches were generally maintained in the test trawl. Model outputs demonstrated effective separation of Nephrops into the lower codend, and size dependent separation of haddock and whiting into the upper codend. Strong performance of this catch separation device facilitates alternative selectivity measures depending on landing obligation requirements. Additional benefits such as improved catch quality and reduced catch sorting times, but also the need for further incentives to encourage industry uptake are discussed.

The influence of mesh size and shape on the size selection of European hake (&lt;em&gt;Merluccius merluccius&lt;/em&gt;) in demersal trawl codends: An investigation based on fish morphology and simulation of mesh geometry

European hake (Merluccius merluccius) is an important commercial species for several European bottom trawl fisheries. Therefore, understanding the influence of codend mesh size and shape on the size selection of European hake is critical for defining technical measures for fisheries targeting this species. Based on morphology data collected on European hake, the influence of mesh size and shape on bottom trawl codend size selectivity was investigated by simulation using the FISHSELECT methodology successfully applied previously for other species. The predicted size selection for European hake was found to agree well with previous experimental results for a wide range of mesh sizes if it was assumed that the codend meshes had a relatively small opening angle, between 20° and 40°, during trawling. This study enables detailed prediction of size selectivity for European hake and offers a potential explanation for previous experimental size selectivity results.

Predicting the Size Selectivity Based on the Striped Red Mullet Morphology (Mullus surmuletus) in Bottom Trawl Fisheries

DOI: 10.26650/ASE201817 The striped red mullet (Mullus surmuletus) is a commercially important demersal species caught by mixed trawl fishing in the Mediterranean Sea. Although it is not among the target species of bottom trawl operations, the striped red mullet is an important species due to its high commercial value in trawl catch composition. The primary target is to catch adult individuals while allowing the immature and juvenile fish to escape for sustainable fisheries using selective fishing gears. Various selectivity studies regarding trawl codends aimed at improving selectivity have been carried out in the past two decades. However, the selectivity sea trials generally require a great deal of work, time, and labor on the deck and are also expensive. Therefore, instead of experimental-based selectivity studies, simulation-based studies (i.e., the FISHSELECT methodology) were recently started to predict the size selectivity of species in bottom trawl fisheries. In this study, sampled individuals of the striped red mullet were used in morphological measurements, fall-through experiments, and simulation phases. Diamond mesh sizes of 40, 44, and 50 mm and a square mesh size of 40 mm of bottom trawl codends were simulated, and the L50 values were calculated as 9.87, 10.75, 12.19, and 12.3 cm for the aforementioned mesh sizes, respectively. Design guides were then created for various mesh sizes and opening angles. The study results were compared with those of previous studies on the red mullet (M. barbatus) that were conducted using the FISHSELECT methodology, and the selectivity results of these two species were found to be similar.

Ege Denizi’nde Derinsu Pembe Karidesi (Parapenaeus longirostris), İstavrit (Trachurus trachurus) ve Bakalyaro için (Merluccius merluccius) döndürülmüş ağ gözü torba seçiciliği

More than fifty published on demersal trawl codend selectivity studies have been carried out in the Mediterranean waters of Turkey since the mid-1980s. In this study, in an attempt to enhance the size selectivity of three species in the Aegean Sea trawl fisheries, three 90o turned meshes codens were investigated. Experiments were carried out in the Kuşadası Bay of the Eastern Mediterranean, between 19 January and 29 March 2015 with commercial stern trawler. The meshes of tested codends were turned 90o , two of them have 44 mm mesh size with 300 and 150 meshes around codend circumferences (44T300 and 44T150). The other has 40 mm mesh size with 165 meshes around codend circumferences (40T165). Individual hauls and mean selectivity parameters were estimated by using the CC2000 and EC-Modeller softwares, respectively. The mean L50 values of 44T300, 44T150 and 40T165 were 17.5 ± 0.2 mm, 18.6 ± 0.1 mm and 17.1 ± 0.2 mm carapace length for shrimp, 16.4 ± 0.4 cm, 17.1 ± 0.4 cm and 14.8 ± 0.2 cm total length for horse mackerel, respectively. The pooled L50 values of, 12.8 ± 0.5 cm, 13.2 ± 0.6 cm and 12.1 ± 0.1 cm total length for hake. While there are no differences between L50 values of 40T165 and 44T300 for deepwater rose shrimp (p>0.05), there are significant differences for horse mackerel (p<0.05). The likelihood ratio test results showed that there were no significant differences among all codends for European hake. In conclusion, any effort such as using square mesh, turned mesh codends or halved the number of meshes in the codend to release immatures of some species, is probably to cause the loss of marketable sizes of other species in the Mediterranean. This economical loss of revenues is the essential concern of fishermen that prevents them using alternative codend designs, though such designs are technically applicable. Consequently, the losses of income caused by using T90 mesh codend and halving the number of meshes around codend circumference should also be investigated in future studies