Net Fishing Research Articles

Anthropogenic threat assessment of marine-associated fauna in Spencer Gulf, South Australia

Assessing the vulnerability of species to [anthropogenic threats is an essential step when developing management strategies for wild populations. With industrial development forecasted to increase in Spencer Gulf, South Australia, it is crucial to assess the ongoing effects of anthropogenic threats to resident and migratory species. Expert elicitation was used to assess 27 threats against 38 threatened, protected, and iconic marine-associated species. Species and threat interactions were assessed individually, and as taxonomic or functional groups. Climate change had the greatest overall exposure (c.f. risk) across species, followed by disturbance, pollution, disease/invasive species, and fishing/aquaculture threats. The largest overall sensitivities (c.f. consequences) were pollution and disease/invasive species, followed by climate change, disturbance and fishing/aquaculture threats. Vulnerability scores (exposure x sensitivity) showed the climate change group posing the greatest overall threat in Spencer Gulf, with individual climatic threats ranking as three of the top four biggest threats to most animal groups. Noise, shipping, and net fishing were considered the greatest region-specific individual threats to marine mammals; as were trawl fishing, line fishing, and coastal activities to fish/cuttlefish; trawl fishing, line fishing, and net fishing to elasmobranchs; and oil spill, disease, and coastal activities to sea/shorebirds. Eighteen of the 20 highest vulnerability scores involved the short-beaked common dolphin, Indo-Pacific bottlenose dolphin, and Australian sea lion, highlighting the particular susceptibility of these species to specific threats. These findings provide a synthesis of key threats and vulnerable species, and give management a basis to direct future monitoring and threat mitigation efforts in the region.

Alien and native fish in gill nets at Rhodes, eastern Mediterranean (2014–2015)

Fish catch composition in 21 gill net samplings performed between 2014 and 2015 at Rhodes Island (Aegean Sea, Greece) was analysed, with the aim to contribute in filling scattered information on coastal fish assemblages in a Mediterranean region heavily impacted by biological invasions. A total biomass of 183 kg was collected comprising 1070 fish individuals, distributed along 43 native and six Lessepsian migrant species. The alien Siganus luridus prevailed in terms of frequency of occurrence, followed by the native Sparisoma cretense, which exhibited the higher abundance and biomass, followed by S. luridus, Scorpaena scrofa and Siganus rivulatus. Ratios between alien and native species as well as between their abundance and biomass are discussed.

A net fishing enrichment strategy for colorimetric detection of E. coli O157:H7

The strict regulatory requirements for pathogen monitoring in food systems to ensure safety demands that the detection method can recognize small numbers of pathogens. Although significant efforts on the development of biosensors have been reported with marked improvement in sensitivity, appropriate enrichment strategies are still needed in a detection scheme. Herein we proposed a unique strategy for the enrichment of pathogens, based on a concept termed as net fishing, to capture target bacteria with antibodies functionalized on porous substrates to fish the target from samples. Because of their large surface area porous nitrocellulose membranes (NC membranes) were used as substrates for target capture. By immersing the antibody modified NC membrane into liquid samples and upon mixing, we expect to anchor target pathogens on the membrane due to the specific interaction between antibody and target, where the nonspecific enrichment could be reduced compared to methods such as filtration. Meanwhile the net fishing enrichment requires 2h, less than common culture methods. An enzyme enhanced procedure was performed with the NC membrane after the capture to obtain colorimetric signal. Gold nanoparticle (GNP) probes conjugated with horseradish peroxidase (HRP) and antibody were used to label capture target bacteria, and the presence of pathogens was determined by the colorimetric signal generated from HRP catalyzed TMB reaction. With E. coli O157:H7 as target, we investigated the detection performance of the proposed net fishing strategy with an enzyme amplification step for colorimetric reporting. After optimization of detection conditions, we show that as low as 100CFU/ml E. coli O157:H7 could be detected. The feasibility was then demonstrated using pineapple juice as a food model.

Production of recyclates – compared with virgin Plastics – a LCA Study

Plastix A/S is a Danish cleantech company transforming discarded fishing trawls and nets into valuable green raw materials. Plastix– technology and processes solve a maritime waste problem and contribute to a more circular green economy and reduce landfilling, marine pollution, CO 2 emissions and especially loss of valuable resources. Plastix– recycling technology enables recovery of discarded fishing trawls and nets via mechanical and thermal processes transforming the waste into valuable recycles which can be converted into plastic products replacing virgin raw materials. The performance has been proved through a Life Cycle Assessment (LCA) study. The results from the LCA study are compared with the production of virgin materials. The results of the LCA show that especially the carbon footprint is remarkable better for Oceanix than for virgin plastics. Oceanix HDPE is 5 times better than virgin HDPE, when talking about the carbon foot print, and the results for Oceanix PP and Oceanix PA6 are 5 times and 20 times better compared with virgin PP and PA6. Also other environmental indicators are better for Oceanix compared with virgin plastics.

Using Behavioral Observations to Develop Escape Devices for Freshwater Turtles Entrapped in Fishing Nets

AbstractThe drowning of freshwater turtles following incidental capture in fishing gear has the potential to cause population declines. Fyke nets can be equipped with bycatch reduction devices that enable the escape of turtles before they drown. We employed quantitative and qualitative behavioral observations (with action cameras deployed underwater) to develop a new, collapsible, escape bycatch-reduction device that mounts internally in the terminal end of a fyke net. We also used behavioral observations to identify areas of the net most used by turtles, thus revealing the most logical placement for an escape bycatch-reduction device. When turtles were introduced into modified nets, escape was rapid (mean of 12.4 min), with 100% escape for map Graptemys geographica and musk turtles Sternotherus odoratus and 94% escape for painted turtles Chrysemys picta. Our preliminary field trials indicated that modified fyke nets decreased the capture rate of turtles relative to unmodified nets. Escape devices can be used as a key component of a bycatch reduction program and be particularly effective when paired with exclusion bycatch-reduction devices. The escape device developed in this study can potentially be used in the local fishery or modified for other fisheries. The use of behavioral observation to guide the development of bycatch reduction devices may provide an extra tool for managers to increase selectivity and maintain sustainable harvests of target fish.

Preliminary study of the sea surface temperature (SST) at fishing ground locations based on the net deployment of traditional purse-seine boats in the northern waters of Aceh — A community-based data collection approach

Reconstruction projects after the Indian Ocean Tsunami of December 26, 2004 were typically contracted out to implementing partners or government agencies. One of the few projects directly implemented by the Body of Rehabilitation and Reconstruction (BRR) was funded by the Asian Development Bank (ADB) to help reestablish fisheries. During the course of the project, 151 GPS-enabled depth sounders with data-logging devices were installed on various types of artisanal fishing boats engaged in the different types of fishing strategies in Aceh such as purse-seine, drop-line, long-line, and gill net fishing. These devices were configured to automatically record time, position, speed, water depth, and sea surface temperature (SST) every time the boat moved 30 m. This study examines the relationship between the sea surface temperature (SST) and the net deployment (ND) of traditional purse seine fishers. The data consists of 922 data sets (6,170,648 data points) collected from 45 purse seine boats between June 2007 and May 2009. Among the data, 1,619 data points indicated the total number of ND; the nets were deployed only when schools of fish were actually sighted. The results indicate that the most frequent SST for ND is 28–28.5°C±0.1365°C with a mean standard error of 0.0117% in a 95% confidence interval. This study has demonstrated that the data gathered from the fishermen (community-based approach) has near-real-time character and, consequently, is an important source for the monitoring and managing of the local fish stocks.

Present status of fish diversity in the Beel Kumari in relation to fish sanctuary and fishing gears

The study was conducted on Beel Kumari beel (wetland) in Rajshahi, Bangladesh from October 2013 to September 2014. A total of 52 species of fish were recorded and the dominant species was Mystus tengara (Tanagra (9.75%). Exotic species like bighead carp (Aristichthys nobilis), silver carp (Hypophthalmichthys molitrix) and common carp (Cyprinus carpio) were also commonly found. Of the indigenous species, Ompok bimaculatus, Puntius sarana, Pseudeutropius atherinoides, Botia dario, Mystus aor and Chitala chitala were abundant, though these species were rare before the establishment of the fish sanctuary. Four groups of fishing gears i.e. net, trap, spear and harpoons and line fishing were found to use, among them 8 types of net, 7 types of trap, 4 types of spear and harpoon and 4 types of line fishing were recorded. Among these gill net contributed to the highest catch (32%) and push net was the lowest (6%). Most of the respondents (80%) were found to believe that their fish catch had increased considerably due to impact of fish sanctuary establishment and effective community based fisheries management approach employed in this beel.

Present status of fish diversity in the Beel Kumari in relation to fish sanctuary and fishing gears

The study was conducted on Beel Kumari beel (wetland) in Rajshahi, Bangladesh from October 2013 to September 2014. A total of 52 species of fish were recorded and the dominant species was Mystus tengara (Tanagra (9.75%). Exotic species like bighead carp (Aristichthys nobilis), silver carp (Hypophthalmichthys molitrix) and common carp (Cyprinus carpio) were also commonly found. Of the indigenous species, Ompok bimaculatus, Puntius sarana, Pseudeutropius atherinoides, Botia dario, Mystus aor and Chitala chitala were abundant, though these species were rare before the establishment of the fish sanctuary. Four groups of fishing gears i.e. net, trap, spear and harpoons and line fishing were found to use, among them 8 types of net, 7 types of trap, 4 types of spear and harpoon and 4 types of line fishing were recorded. Among these gill net contributed to the highest catch (32%) and push net was the lowest (6%). Most of the respondents (80%) were found to believe that their fish catch had increased considerably due to impact of fish sanctuary establishment and effective community based fisheries management approach employed in this beel.

Mosquito Net Use in an Artisanal East African Fishery

AbstractWidespread, anecdotal reports of the use of bed nets designed for malaria control (“mosquito nets”) in artisanal fisheries have led to concern from health and natural resource management sectors. However, mosquito net fishing (MNF) may play an important role in the livelihoods of artisanal fishers, an aspect not yet investigated. At a coastal Kenyan site among Giriama fishers, nearly half of homesteads interviewed used mosquito nets as fishing gear, targeting juvenile fish and prawns for subsistence and sale. The majority of mosquito net (MN) fishers here were men, suggesting that the assumption that MNF is a female activity is not valid in this case. However, MN use for fishing at this site is unlikely to impact malaria protection as fishers used old or surplus nets. Respondents perceived both positive aspects of MNF (e.g., food and income) and negative aspects (e.g., impact on fishery). As mosquito nets are widely available, they may enable new entrants to access fisheries. There is a critical need to review current management responses, which predominately focus on banning the practice, and instead promote integrated strategies for sustainable livelihoods.

Ecological aspects of water impoundment in the tropics.

Recognition of the potentially harmful effects of water development in the tropics had led to increasing efforts to assess the environmental impact of such projects prior to construction. Decisions regarding the development or non-development of water resources must be based on sound investigation of both the long-and short-term effects of reservoir construction and operation. The environmental effects of water impoundment vary greatly with the characteristics of the region as well as the type of reservoir to be constructed (area and depth of reservoir, ratio of water inflow to storage). Of major concern are the reduction of reservoir capacity as sediments accumulate behind the dam and the loss of these sediments to downstream agriculture and fisheries. The potential impact of altered flow regimes, siltation, reduction in beach formation and nutrient enrichment at the mouths of rivers, and the possibility of saltwater encroachment should receive careful stdy. A thorough description of the plants and animals to be affected by inundation should be made to determine the possible loss of rare or key organisms as well as the potential development of "nuisance species". Included in this survey should be a detailed study of existing fish and the potential for commercial fishery development in the proposed reservoir. Consideration should be given to vegetation removal in the reservoir basin prior to inundation, since decaying vegetation can result in deoxygenation, formation of hydrogen sulfide, possible development of suitable habitats for undesirable species and snagging of fish nets. Sanitation and land use practices as well as erosion in the watershed surrounding the reservoir must be controlled to prevent accelerated eutrophication caused by increased nutrient loading. Inundation in tropical areas can have serious sociological and human health implications including the increase of diseases, e.g., malaria, schistosomiasis, onchocerciasis, and dysentery, and the probable resettlement and alteration of land use practices. Census information and surveys concerning land use, housing and health standards and the social and economic structure of the community to be affected must be evaluated in order to anticipate and avoid potential problems. The archaeologic, historic, scenic and recreational value of the site to be inundated must also be considered. Studies of the EL Cajón site on the Sula River in Honduras and the Purari River Project in Papua, New Guinea, are utilized as examples in this report.

Sinuolinea niloticus n. sp., a myxozoan parasite that causes disease in Nile tilapia (Oreochromis niloticus).

Sinuolinea species are myxozoans of the order Bivalvulida, suborder Variisporina, and family Sinuolineidae, which can be parasites for freshwater and marine fish. The aim of this study was to describe the occurrence of Sinuolinea niloticus n. sp. infecting Nile tilapia (Oreochromis niloticus) from aquaculture and from river sources with morphological and molecular analyses. Between March 2010 and November 2012, 116 Nile tilapia were randomly sampled from aquaculture net fishing (n = 56) in Mira Estrela, São Paulo, and from the Capivari River (n = 60) in Botucatu, São Paulo. The fishes that were sampled were examined by necropsy, microscopic observation and molecular techniques for detection and identification of the myxozoan causing disease in tilapia. All of the tissues that were sampled for analysis showed the presence of the parasite. It was observed by microscopy that the myxozoan belongs to the Sinuolinea genus. This identification was performed based on morphological characteristics and histopathology findings, such as structures consistent with myxozoan in the interstices in all analysed tissues, coagulative necrosis, haemorrhage, inflammatory processes, presence of melano-macrophages and eosinophils. The results of the molecular analyses revealed that the myxozoan detected and identified in this study is sister to a group of other Sinuolinea species. Because this is the first report of this parasite in Nile tilapia, the parasite was named S. niloticus n. sp. This is the first report of a Sinuolinea species in Brazil and in tilapia.

The Use of Bridle Line on Operation of Bottom Gill Nets in Manado Bay Waters, North Sulawesi, Indonesia

This study was intended to figure out the influence of bridle line application on bottom gill net fishing operations. Bridle line length 1 m in order to prevent the lead line and lower net line to directly touch the bottom waters, and to minimize lifting of pieces of coral and by-catch. Lifting pieces of coral could damage bottom habitats and the benthic organisms. The use of bridle line had resulted the gill net to be environmental friendly and cought only the economically important fish. Bottom gill net used in this study had a size of 148.00 m long and 4.70 m wide and mesh size of 13.75cm with net yarn number 18. It was operated outside of the coral reefs zones at the depth range of 20 m to 50 m. The fish catches were demersal and reef fish with minimum size of 25cm body circle or bigger was dominated by dogtooth tuna, Gymnosarda unicolor. The application of 1 m-bridle line can reduce the coral cover up to 98% compared to the other bottom gill net which its lower part have a direct contact with the seabottom. During 10 fishing trips, there was no benthos brought up to the surface at during the net hauling. But new problem was found that the use of bridle line on the gill net had causes fish escape through the bridle line along the bottom net.

What gets left behind for future generations? Reproduction and the environment in Spey Bay, Scotland

What gets left behind for future generations? Reproduction and the environment in Spey Bay, Scotland

Customary Access: Sustaining Local Control of Fishing and Food on Kaua‘i’s North Shore

Where Hawai`i’s land and sea once supported a population close to contemporary times, today 90 percent of food consumed in Hawaiʻi is imported and delivered on container ships. Once plentiful in the bays and coral reefs surrounding these islands, fish is now frequently shipped in and store bought. Yet, local families in parts of Hawai`i have maintained self-sufficiency in part of their food system through communal surround net fishing, employing ancestral knowledge, mobilizing community effort, and sharing catch from these collective harvests. This article examines the role of access in perpetuating surround net harvests and sharing through hōʻihi (respectful reciprocity); konohiki (inviting ability); and kuleana (rights based on responsibilities). It concludes by considering the implications of the findings for food systems and food security.

Length-weight relationships of three schizothoracinae fish species from the Niyang River, a branch of the Yarlung Zangbo River, Tibet, China

The focus was on the length–weight relationships of three schizothoracinae species endemic to Tibet, including Schizothorax oconnori Lloyd, 1908, Ptychobarbus dipogon (Regan, 1905) and Schizopygopsis younghusbandi Regan, 1905, all of which are characterized by slow growth, late maturation and vulnerability to the environment (Ma et al., 2010, 2012; Duan et al., 2014). Among them, Schizothorax oconnori is an endangered fish and listed in the China species Red List (Wang and Xie, 2004, 2009). Samples were obtained by drift net fishing (mesh size 2 cm × 3 cm; 50 m net length) in November 2008. The r2 value was 0.94, 0.97, 0.98 and the b value 3.51, 3.12, 3.16, representing Schizothorax oconnori, Ptychobarbus dipogon, and Schizopygopsis younghusbandi, respectively.

Do you catch undersized fish? Let's Go fishing to learn some important concepts in multiple testing

SummaryIn the era of Big Data, because of diminishing cost of data collection and storage, a large number of statistical tests may even possibly be conducted all together by a high school student to seek for some ‘exciting’ new scientific findings. In this article, we propose an interesting approach to introduce students to some important concepts in multiple testing by an analogous example of net fishing. The proposed teaching approach is fun and requires no mathematical calculation.

Age and growth of blotched picarel (Spicara maena Linnaeus, 1758) in the Sea of Marmara and Northern Aegean Sea

Abstract: : The aim of this study was determining of some population parameters of Spicara maena in the Sea of Marmara and North Aegean Sea. Samples of S. maena were collected from commercial fishing, gillnet/trammel net and line fishing, between February-October 2013 in the Northern Aegean Sea (Dikili, Altinoluk, Kucukkuyu) and the Sea of Marmara (Karabiga, Bandirma, Tekirdag). A total of 323 S. maena specimens were analysed. The total length of the specimens ranged from 8.4 to 18.8 cm. The length-weight relationships for the Sea of Marmara and the Northern Aegean Sea were a=0.0030, b=3.53, SEb=0.080 and a=0.0100, b=3.06, SEb=0.120 respectively. The b values showed that the growth of S. maena in the Northern Aegean Sea was isometric while the sample in the Sea of Marmara showed positively allometric growth. Fish aged 1-4 years in the Sea of Marmara and 2-6 years in the North Aegean Sea were present in the samples. Growth in length including both sexes was expressed using the von Bertalanffy equation, L∞=17.17 cm, k=0.52 y, t0=-1.04 y-1 in the Sea of Marmara and L∞=18.71 cm, k=0.35 y, t0=-1.98 y-1 in the Northern Aegean Sea. The otolith length-total length relationships in the Sea of Marmara and the Northern Aegean Sea were OL=0.301×TL+1.049 and OL=0.249×TL+1.885, respectively. Keywords: Spicara maena, otolith, length-weight relationship

Artisanal fishing net float loss and a proposal for a float design solution

Abstract Plastic floats from fishing nets are commonly found washed up on beaches in southern Brazil. They are usually broken and show signs of having been repaired. Characteristics of floats and interviews with fishermen suggest two main causes of float loss. First, collisions between active gear, bottom trawl nets for shrimp, and passive gear, drift nets for fish, destroy nets and release fragments of them, including floats. Second, the difficulty with which floats are inserted on the float rope of the nets when they are used near the surface. Floats are inserted to replace damaged or lost floats, or they may be removed if it is desired that the nets be used in deeper waters. Floats may thus be poorly fixed to the cables and lost. Here a new float design that offers greater safety in use and for the replacement of floats is described and tested.

Use of biodegradable driftnets to prevent ghost fishing: physical properties and fishing performance for yellow croaker

When synthetic non-biodegradable fishing nets are lost, abandoned or discarded at sea, they may continue to catch fish and other animals for a long period of time. This phenomenon is known as ‘ghost fishing’. Biodegradable fishing nets, on the other hand, are intended to degrade or decompose after a certain period of time under water and thereby lose their ghost fishing capacity more quickly than conventional gear. A biodegradable net material, a blend of 82% polybutylene succinate (PBS) and 18% polybutylene adipate-co-terephthalate (PBAT), was developed. We examined the physical properties and degradability of the biodegradable monofilament, and compared the fishing performance of driftnets made of conventional nylon and of the biodegradable material. When dry, conventional nylon monofilament exhibited a greater breaking strength and elongation than biodegradable monofilament of the same diameter. When wet, the biodegradable monofilament exhibited a stiffness of c. 1.5-fold than nylon monofilament. This suggests that a net made of the less flexible biodegradable monofilament would have lower fishing efficiency than conventional nets. The fishing performance comparisons between the biodegradable and conventional nylon nets, however, revealed similar catch rates for yellow croaker Larimichthys polyactis. Biodegradable monofilament started to degrade after 24 months in seawater by marine organisms. We conclude that biodegradable netting may become a feasible alternative to conventional nylon netting and can contribute to reducing the duration of ghost fishing. Nonetheless, there remain many uncertainties, challenges and knowledge gaps that have to be solved before we are able to draw firm conclusions about the overall benefits of these materials in driftnet fisheries.

Further expansion of the alien seaweed Caulerpa taxifolia var. distichophylla (Sonder) Verlaque, Huisman & Procacini (Ulvophyceae, Bryopsidales) in the Eastern Mediterranean Sea

Caulerpa taxifolia var. distichophylla (Sonder) Verlaque, Huisman and Procacini is a green alga of Australian origin recently reported as an alien species in the Mediterranean Sea, where it is known from SE Turkey, Sicily, Cyprus and Malta. In the current study we present additional records of this taxon, expanding its known distribution into the Eastern Mediterranean Sea, and provide additional records from Cyprus and the first records from Rhodes Island (Greece). Our specimens were identified through a combination of morphological and molecular methods involving sequencing of ITS and tufA. Locally, C. taxifolia var. distichophylla occurred in high abundances and dominated the benthic community, suggesting that has the potential to become a major pest in the Mediterranean. It was also observed over a very wide depth range, from the sea surface to at least 100 m depth, on a variety of natural soft and hard substrates as well as abandoned fishing nets, suggesting a broad environmental plasticity. One of the findings reported here constitutes the deepest record of an alien Caulerpa in the Mediterranean Sea, even though it remains to be demonstrated that it actually grows at this site and depth rather than being merely a drift specimen.