Net Mesh Research Articles

Bio-economic studies on the catch of Bardawil Lagoon, North Sinai, Egypt

The paper aims to give a comprehensive descriptive survey on the production of Lake Bardawil from 1985 to 2015. The average production in this period was 2970 tons. Monthly samples were collected for 12 species of fish during fishing season 2015. The results showed that the Length at first capture (Lc) of different species in Bardawil Lagoon was less than the length at first maturity (Lm); Lm of Mugil cephalus, Sparus aurata and Dicentrarchus labrax was 31.1, 24.5 and 31.0 cm, meanwhile, Lc was 29.0, 18.5 and 27.8 cm respectively. The percentage of small fish with less than the Length at first maturity (Lm) constitutes 67.3% for inexpensive species and 77.05% for expensive species. The loss of biomass in the inexpensive species was estimated at 3268 tons and the loss in income was 199 million Egyptian pounds (LE). The loss of biomass of expensive species was calculated at 1455 tons and the loss of income was 175 million LE. The total loss of biomass was 4723 tons and 374 million LE due to fishing violations and the use of illegal nets in only one fishing season. For proper management, the Length at first capture (Lc) must be increased by widening the nets mesh size. Legal fishing methods and the development of appropriate non-traditional methods for the management of Bardawil Lagoon must be applied.

Meta-analysis of the use of sterilized mosquito net mesh for inguinal hernia repair in less economically developed countries.

BackgroundInguinal hernias are common in less economically developed countries (LEDCs), and associated with significant morbidity and mortality. Tension‐free mesh repair is the standard treatment worldwide. Lack of resources combined with the high cost of commercial synthetic mesh (CSM) have limited its use in LEDCs. Sterilized mosquito net mesh (MNM) has emerged as a low‐cost, readily available alternative to CSM. The aim of this systematic review and meta‐analysis was to evaluate the safety and efficacy of MNM for the use in hernia repair in LEDCs.MethodsA systematic review and data meta‐analysis of all published articles from inception to August 2018 was performed. Cochrane Central Register of Controlled Trials, MEDLINE and Embase databases were searched. The primary outcome measure was the overall postoperative complication rate of hernia repair when using MNM. Secondary outcome measures were comparisons between MNM and CSM with regard to overall complication rate, wound infection, chronic pain and haematoma formation.ResultsA total of nine studies were considered relevant (3 RCTs, 1 non‐randomized trial and 5 prospective studies), providing a total cohort of 1085 patients using MNM. The overall complication rate for hernia repair using MNM was 9·3 per cent. There was no significant difference between MNM and CSM regarding the overall postoperative complication rate (odds ratio 0·99, 95 per cent c.i. 0·65 to 1·53; P = 0·98), severe or chronic pain (OR 2·52, 0·36 to 17·42; P = 0·35), infection (OR 0·56, 0·19 to 1·61; P = 0·28) or haematoma (OR 1·05, 0·62 to 1·78; P = 0·86).ConclusionMNM has a low overall postoperative complication rate and is unlikely to be inferior to CSM in terms of safety and efficacy. MNM is a suitable low‐cost alternative to CSM in the presence of financial constraint.

Length-weight relationships of nine freshwater fishes from six rivers of the Western Ghats of India

Length–weight relationships (LWRs) were estimated for nine freshwater fish species collected three times using a scoop net (mesh size 0.3–0.5 cm), cast net (mesh size 1–1.5 cm) and gillnet (mesh size 2.5–4.5 cm) from six rivers of the Western Ghats of India during August 2017–October 2018. The b values for LWRs varied from 2.862 to 3.656 (R2 > 0.916 and p < 0.0001 for all species).

Length–weight relationships for 15 fish species from the Three Gorges Reservoir

The length–weight relationships (LWRs) for 15 fish species from the Three Gorges Reservoir (TGR) were described in this paper. Specimens were collected using gill nets (mesh size: 6, 8, 10, 12 cm), cage net (mesh size: 1 cm), benthic fyke net (mesh size: 1 cm), hook longlines (80 m long, 3 barbless hooks per meter line) and electrofishing (power: 1,500 w; distance of electrodes: 1–2 m; water depth: 0.2–1.0 m; water area: 1–2 m²; catch by dip net [mesh size: 0.4 cm]) at four sections of the TGR, monthly in June–August and October–November in 2017 and 2018. The first LWR reference for Zacco acutipinnis (Bleeker, 1871), Discogobio brachyphysallidos Huang, 1989, Squalidus nitens (Gunther, 1873), Leptobotia pellegrini Fang, 1936, Sinibotia reevesae (Chang, 1944), Pseudobagrus tenuifurcatus (Nichols, 1931), Pseudobagrus medianalis (Regan, 1904), Liobagrus marginatoides (Wu, 1930), Glyptothorax fokiensis (Rendahl, 1925), and Ctenogobius szechuanensis (Liu, 1940) and new maximum total length for 12 species are provided.

Catch dynamics of set net fisheries in Israel

Artisanal fisheries are globally common, providing almost 50% of total world landings. However, due to overfishing, they are worldwide on the verge of collapse. Fisheries in the eastern Mediterranean Levantine Basin must additionally cope with extreme thermal conditions, meaning that fish are typically smaller relative to other regions. In Israel, mesh size restriction has been suggested as a means to rebuild stocks, but data on artisanal fishing landings across mesh size are extremely sparse. The aim of this study was to quantify set net catches across different mesh sizes in order to identify fishing methods that can benefit both fish populations and fishers. We hope to identify which mesh size provide the highest ratio of commercial to non-commercial fished biomass, the lowest variance in fisher’s revenues and benefits the reproductive potential of the resource by targeting mature individuals. We found that across the range of mesh sizes examined, smaller mesh sizes (i.e. 25, 28, 30) did not catch a larger proportion of individuals below reproductive size but, rather, smaller species. The 43 mm mesh, caught larger individuals with lower total biomass but of larger species, with similar proportions of individuals below reproductive size to smaller mesh sizes. Net mesh size was not associated with fisher revenue. Trammel nets were found to be the least selective in relation to non-commercial by-catch, although the proportion of mature individuals in the catch was larger than for the other nets examined. These findings suggest that mesh size restrictions, across the range of mesh sizes examined, will not result in a decrease in catch of individuals below reproductive size but rather shift the species composition of the catch towards large-bodied, often high trophic level, species. Thus, mesh size restrictions are unlikely to rebuild fish stocks of high-value commercial species nor increase fisher revenue. We suggest that artisanal fisheries management in the Levantine Basin should evaluate new management measures and consider reducing overall fishing pressure along with implementing ecosystem-based fisheries management, such as the closure of fish reproduction and recruitment areas and establishment of marine protected areas.

Cost effective use of mosquito net mesh in inguinal hernia repair

Mesh hernia repair is one of the commonest open techniques of inguinal hernia repair. The main limiting factor in the use of new meshes is the cost. We carried out a prospective randomized double blind study and comprising of a hundred patients with 100 inguinal hernias admitted consecutively for elective surgery, divided into the polypropylene mesh (PPM) group and the mosquito net mesh (MNM) group each containing fifty patients. All cases were completed successfully and results revealed no difference in two groups. The results of the present study, in consistent with the published literature, reveal that the cheap indigenous mosquito mesh, which has similar properties of an imported mesh, can be safely used for tension-free inguinal hernia repair in adults. Further trials with a larger number of patients and longer follow-ups are justified and recommended.

Development of a Catch Basin Sump Insert to Reduce Mosquitoes

A catch basin sump is one major habitat for mosquito larvae, especially in urban areas. This study developed a device for mosquito control, specifically for the catch basin sump. It consists of a housing, is a little smaller than the catch basin sump, numerous floating materials, which the key component for mosquito control, and mesh nets. The small balls or pyramid-shaped floating materials inhibit mosquito enclosures and spawning by significantly decreasing the surface area of the water, which is essential for the mosquito life cycle. These floating materials were designed to keep the water flowing. The mesh nets were installed to prevent the outflow of floating materials. The efficiency of the floating materials was tested with 3 conditions (1, 2, 3 layers of floating materials) and a control group. The emergence of mosquito adults decreased by 20% in one-layer, and 70-80% in second and third layers. Therefore, this device is expected to certainly contribute to mosquito population control in the catch basin sump.

Deformation and drag force of model square fish cages in a uniform flow

Model experiments were carried out to investigate the performance of different types of 1:8.3-scale model square fish cages in a uniform flow. The model cages were designed using different netting materials, mesh types, and cage depths. Shape deformation, volume reduction, and drag force were used as key parameters to characterize the cage performance. The results indicate that cages using polyethylene netting for the four sides and wire-netting for the bottom generally show better performance than those composed entirely of polyethylene netting; specifically, the former undergoes less shape deformation and volume reduction than the latter. The mesh type (square or diamond mesh) had a noticeable effect on shape deformation and drag force but a limited effect on cage volume reduction. Moreover, for the cages with wire-netting bottom and polyethylene sides, the bottom net tended to drift parallel to its undisturbed orientation when the sides were composed of square mesh netting. In contrast, the bottom net drifted obliquely upward on the downstream side when diamond mesh netting was used for the side nets. It was also confirmed that drag force per unit volume of the cages with wire-netting bottom was larger than that for the cages composed entirely of polyethylene netting.

Seasonal variations of plankton structure as bioindicators in Zayandehrud Dam Lake, Iran

Abstract Zayandehrud Dam Lake located in Isfahan province is the largest lake in central Iran. In this study, the plankton communities including phytoplankton and zooplankton were studied as bioindicator organisms for assessment of water quality in the Zayandehrud Dam Lake. The water and phytoplankton organisms were collected from four stations at different seasons during 2014 by using a Nansen bottle sampler. The zooplankton samples were collected with a plankton net (mesh size = 50 µm). The phytoplankton community was composed of Bacillariophyceae, Cyanophyceae, Euglenophyceae, Dinophyceae and Chrysophyceae. The zooplankton community viz; Cladocera, Rotifera and Copepoda were found to have a density range of 13–155, 21–141 and 11–93 (ind. m−3), respectively. In general, phytoplankton and zooplankton communities, especially the presence of genera such as Cyclotella, Dynobrion, Bosmina and Daphnia (as indices of oligotrophic lakes) and also absence of Microsystis, Brachionus and Lecane are seen as important indices of eutrophic lakes. It could be concluded that the Zayandehrud Dam Lake can be classified as a healthy water body.

PENERAPAN PERUBAHAN UKURAN MATA JARING DALAM PENANGKAPAN IKAN TERBANG SECARA BERKELANJUTAN DI KECAMATAN SENDANA KABUPATEN MAJENE

Catching flying fish in Sendana Majene Subdistrict is carried out continuously with gill nets 1-1.5 inches. The catch of flying fish is mostly still young fish (not yet worth catching). The demand for flying fish is quite high due to the existence of special stalls of smoke fly fish around fishing settlements. Apart from smoke flying fish, dried flying fish are also sold as souvenirs. Therefore, fishermen will continue to increase production. Various results of research and field observations show that gill net is able to catch flying fish well but the size of fish caught is dominated by young fish. The effort to increase the net mesh size to 1.5 inches resulted in the diminishing number of young flying fish. Catching flying fish in Majene waters is generally carried out with drifting gill nets with mesh sizes of 1 and 1.25 inches which are very intensive every fishing season while L50 (11.92 cm) and Lm (13.59 cm) for 1 inch more net mesh size were smaller compared to the length of the first gonad maturity, in this case most of the catch is still classified as young fish (Palo, 2009). Partners are a group of flying fish fishermen. Partner problems, flying fish production is getting smaller, group capacity is not strong and group management is still weak. Partners have not been able to obtain assistance facilities from various community empowerment programs carried out by the government. The approach to be used in this service includes: identification, observation, counseling, demonstration, construction, application, assistance, field observation and evaluation monitoring. Indicators of the success of activities are measured based on the results of the application of technology compared to the results of fishing gear commonly used by fishermen. Implementation of service includes counseling, construction of fishing gear, fishing operations and assistance has been going well. The size of 1.5-inch mesh is only able to catch flying fish in a limited amount, while the size of the 1.25-inch mesh can catch flying fish in relatively large numbers. Flying fish caught with 1.25-inch mesh size has passed the size of the first gonad mature so that it supports sustainable fisheries.

Effect of mesh size modifications on the sinking performance, geometry and forces acting on model purse seine nets

To ensure efficient and sustainable purse-seine fisheries, it is necessary to understand well the fishing performance of a purse seine, which can be related to many factors, such as mesh size, twine materials, leadline weight, fishing operations and the marine environment. In this study, we tested two tuna purse seine model nets with different mesh sizes to obtain the lateral and drifting distance, spatial geometry, purse line tension and sinking speed of a purse seine under different operation conditions related to the current direction, three net shooting patterns and two current speeds. It was found that better spatial geometry and sinking behavior of the purse seine occurred by shooting the net normal to the current than shooting it with or against the current. Setting with the current was considered as the optimal strategy of shooting the net in terms of reducing the tension of the purse line. The net drifting distance decreased when the mesh size of the main body was increased, and the minimum lateral and drifting distances occurred when setting with the current. Increasing the mesh size helped reduce the enclosed area in the horizontal direction, especially of the bottom of net, and keep a better net shape. The pursing time and purse line tension reduced by 12% and 9.26% respectively when the mesh size of the lower part of the main body increased from 30 to 45 mm. In general, larger mesh nets can decrease purse line tension and improve sinking performance and net geometry.

Diversity of phytoplankton species in Cheonjin Lake, northeastern South Korea

BackgroundSeveral investigations carried out from large brackish lagoons in South Korea. However, no studies have yet examined phytoplankton in lagoons that changed to freshwater, such as Cheonjin Lake. The present study examined the algae from Cheonjin Lake.MethodsSamples were collected at monthly inetrvals from May 2017 to April 2018, from the surface layer using a plankton net (mesh size 20 μm), and sequeezing submerged macrophytes. Microscopic examinations were conducted at a magnification of 200 to 1000x using a Zeiss microscope (Axio Imager. A2), and photographs were taken with an AxioCam HRC camera. Silica-scaled samples of Chrysophyta for SEM were placed on coverglass, air dried, coated with gold, and then examined with a Hitachi SV8220 SEM.ResultsA total of 376 taxa from six major algal groups (Chlorophyta, Chrysophyta, Euglenophyta, Cyanophyta, Dinophyta, and Cryptophyta) were identified. Among these algae, 28 taxa of desmids, 9 taxa of Euglenophyceae, 4 taxa of Chlorophyceae, 2 taxa of Chrysophyceae, and 1 taxon of Xanthophyceae are reported for the first time in Korea. A new species, Cosmarium hexagonum sp. nov was described. The phytoplankton communities were characterized by an abundance of Desmids (within Charophyceae) accounted for 148 taxa from 22 genera. Species richness were particularly high in the Autumn.ConclusionIn this study, a total 376 taxa of 148 desmids (Charophyceae), Chlorophyceae (103 taxa), Chrysophyceae (53 taxa), Euglenophyta (49 taxa), Dinophyta (8 taxa), and Cryptophyta (2 taxa) were identified from Cheonjin Lake. Twenty-eight taxa of desmids including a new species (Cosmarium hexagonum sp. nov.), 9 taxa of Euglenophyceae, 4 taxa of Chlorophyceae, 2 taxa of Chrysophyceae, and 1 taxon of Xanthophyceae were newly recorded in Korea.

Does the biofloc size matter to the nitrification process in Biofloc Technology (BFT) systems?

In addition to environmental factors, particle size can interfere with the nitrification process because smaller flocs are less efficient in terms of ammonia and nitrite oxidation. The objective of the present study was to evaluate, in three experiments, the effect of the biofloc size on the nitrification process during the production of the white shrimp Litopenaeus vannamei in a BFT system. In all experiments, 1% of biofloc inoculum from production tanks was used. Water samples were taken to photograph and measure the flocs. Measurements of temperature, salinity, nitrogen compounds and total suspended solids were also carried out in the experiments. In experiment 1, the flocs were separated by sifting the water through mesh nets of 50, 150 and 300 μm in size. In addition, there was a control treatment with integral flocs. In experiment 2, the bioflocs were separated into 300 and 600 μm size classes and were compared with an integral control. Experiment 3 aimed to evaluate the nitrification process in treatments with flocs smaller than 150 μm, in flocs without handling (Control), and in the treatment where flocs were partially filtered in a 50 μm mesh for five days. This treatment resulted in a reduction in the particle size; however, when the meshes were later removed, and the biofloc size increased again. Different from our original hypothesis, the results of these three experiments indicate that the size of the biofloc, as well as the amount of total suspended solids, do not affect the nitrification process in the BFT system. However, all treatments that included manipulation through sifting showed a delay or a decrease in the nitrification activity. Thus, it is likely that, more than the particle size or floc abundance, the rupture of the floc structure affects the distribution and interaction of nitrifying bacteria with reflections in the nitrification process.

Length-weight relationships of two fish species from the South China Sea

The length–weight relationships were determined for two fish species: Kumococius rodericensis (Cuvier, 1829) and Inegocia japonica (Cuvier, 1829). Samples were collected at seasonal surveys in the South China Sea using bottom trawl nets (mesh size 4.0 cm, at a towing speed about three knots) from September 2014 to October 2017. The estimated growth coefficient (b) of these two species ranged from 3.2963–3.2980.

Length-weight relationships of three fish species from central China

Length-weight relationships were determined for three fish species (Culter oxycephaloides Kreyenberg & Pappenheim, 1908, Liobagrus marginatoides (Wu, 1930) and Pseudobagrus tenuis (Günther, 1873)) from central China. Specimens were collected using fishing gears [set nets (mesh: 1.5 cm × 2.0 cm), hook, drift gill nets (mesh: 1.0 cm × 2.0 cm × 3.0 cm) and electro fishing (depth: 30–60 cm; near the beach) quarterly from September 2016 to August 2017. For Liobagrus marginatoides the LWR estimate includes a new SLmax. Further, the estimate for Pseudobagrues tenuis yielded a relatively high coefficient of correlation despite the relatively small sample size.

Length-weight relationships of four endemic snakeheads [Channa andrao Britz, 2013, Channa aurantimaculata Musikasinthorn, 2000, Channa bleheri Vierke, 1991, and Channa stewartii (Playfair, 1876)] from the Brahmaputra drainage, northeast India

The paper provides the Length–weight relationships (LWRs) for four endemic snakehead fish species namely Channa andrao Britz, 2013, Channa bleheri Vierke, 1991, Channa aurantimaculata Musikasinthorn, 2000 and Channa stewartii (Playfair, 1876), based on seasonal catches along the Brahmaputra river drainage from October 2016 to May 2018, using cast net (mesh size: 10–20 mm), scoop net (mesh size: 05–10 mm) and bamboo traps. Total lengths (TL) (nearest to 0.1 cm) and body weights (nearest to 0.1 g) were taken respectively. The b values in the LWRs were 3.26 for C. andrao, 2.74 for C. bleheri, 3.04 for C. aurantimaculata, and for 2.78 C. stewartii respectively. For C. aurantimaculata (=36.2 cm), C. bleheri (=14.4 cm) and C. stewartii (=29.7 cm) each, a new maximum total length (TL) was recorded.

Length-weight and length-length relationships of four fish species from rivers in the Tibetan Plateau, China

Length-weight (LWRs) and length–length relationships (LLRs) were estimated for three native and one non-endemic fish species, representating three families and four genera from four sites in the Tibetan Plateau, China. Specimens were caught by a gill net (mesh size: 1-inch), cast net (mesh size 1–2 cm; depth: 1–2 m) and a traditional shrimp coop during July 2006, and from July 2013 to August 2014. The LWRs b-values of all fish species ranged from 2.63 to 3.29. All correlation coefficient values were higher than 0.95. Their LLRs were highly correlated.

Length and weight relationships of five different fish species from northern areas of Pakistan

In present study five different species were studied from three different rivers from northern Pakistan. Specimens were collected in the period of January to December 2017 using cast nets (10–12 mm mesh size) for Barilius, Glyptothorax and Schistura species while cast nets (mesh size 1.25 × 1.25 cm) used for Schizothorax species. Total length (TL) and fork length (FL) to the nearest 0.1 cm and body weight (BW) to the nearest 0.1 g were recorded for each individual.

Shark management strategy policy considerations: Community preferences, reasoning and speculations

Shark management is contested and community support often influences policy. Decision makers are unlikely to be comfortable explaining policy solely based on expert advice, scientific data, or any information, if they feel out of touch with important stakeholder thinking. This study explored community attitudes to shark management and also reasons for preferences. It used Appraisal to analyse comments related to the NSW Shark Management Strategy in Twitter and public Facebook sites over one year, and focus groups with beach and ocean end-users. Most harm mitigation and research strategies were supported, with drones and Clever Buoys the preferred concepts. Mesh nets were widely criticised. The most common reasons given for strategy preferences emphasised the likelihood of harm to sharks and other marine species, cost efficiency, and likelihood that a strategy would generate fear or reassurance. Findings emphasised hope that detection, deterrent and surveillance technologies will improve efficacy of shark harm mitigation in the future. Importantly for policy makers, the findings elaborate simple preference information, revealing multidimensionality in attitudes concerning shark harm mitigation strategies, and explaining associations and thinking. The study highlights the importance of listening to communities and carefully planning and adapting policy communication.

POPULATION DYNAMIC AND EXPLOITATION RATE OF THE BLUE SWIMMING CRAB (Portunus pelagicus) IN THE KENDARI BAY WATERS

Kendari Bay waters consitute a potential blue swimming crab (BSC) fishing ground in WPP NRI 714 (the Banda Sea). The intensive fishing activities have been increasing from year to year that raised concern to the fishing that will disturb resource sustainability. Therefore, an alternative sustainable management is advisable. The purpose of this research was to examine the population dynamics and exploitation rate of BSC in the Kendari Bay waters conducted between January and November 2016. The results show the isometric of BSC growth pattern and balance of male and female ratio. The length at first capture (L c ) of BSC was 116.65 mm (carapace width),smaller than the length at first maturity (L m ) at 119.7 mm (carapace width). The von Bertalanffy growth equation for the blue swimming crab was L(t) = 182.0[1-e -0.91 (t - 0) ] and the fishing mortality rate (F) was higher than the natural mortality rate (M). The blue swimming crab exploitation rate calculated BSC from Kendari Bay has exceeded the optimum rate of 0.73 per year and is indicating a category “overfishing”. Therefore, to maintain the BSC stock sustainability, a management measure is needed to reduce the current fishing effort of approximately 46 % from the current effort and regulation of net mesh size.