Large Trawl Research Articles

The Effect of Environmentally Unfriendly Fishing Gear on The Welfare of Fisher in Morodemak Village, Demak Regency

This study aims to see the effect of the use of fishing gear that is not environmentally friendly on the welfare level of fisher in Morodemak Village, Demak Regency. The method used in this study is a snowballing technique for sample collection through interviews so that 50 respondents are obtained, then the analysis method used is cross-tabulation and descriptive statistics. The results of this study found that the majority of Morodemak fisher use environmentally unfriendly fishing gear such as sodo, large trawls, especially small trawls. The use of environmentally unfriendly fishing gear by the majority of fisher certainly damages the marine ecosystem, but the fishing gear is still considered effective for obtaining abundant catches that affect the welfare of fisher.

The effect of quota portfolio composition on optimal harvest strategy and profitability in a multi-species fishery

Abstract The benefits of individual vessel quota (IVQ) management in terms of improved harvest strategy and profitability are well recognized, but there is less focus on how different components of a quota portfolio can influence decisions underlying the effort allocation and profit-maximizing behaviour of fishers. Variations in the components of the quota portfolio may create economic incentives that alter the optimal harvest strategy and profitability. Thus, we study the potential impact of different components of quota portfolio on the intra-annual harvest strategy and profitability in two segments of the Norwegian bottom trawl fleet. By developing a vessel-based spatio-temporal bioeconomic framework, we demonstrate and compare adopted harvest strategies and accrued profits for small and large trawl vessels under three scenarios regarding restrictive quotas in codfish fishery. Our analysis confirms that alternations in the components of the quota portfolio influence the spatio-temporal dynamics of the fishing effort for small and large trawl vessels in different ways, probably due to the differences in vessel-specific characteristics. We also demonstrate that the differences in profit between small and large vessels in part depend on the overall size of the quota portfolio. The economies of scale in the trawl industry are being eroded as the shares of higher-priced species in the quota portfolio decreases. The benefits of economies of scale cannot be reaped as trawlers respond to the reduction in profit by redirecting effort from offshore areas of the Arctic to nearshore waters or staying ashore. Likewise, having small quotas of high-priced species reduces the effectiveness of the IVQ system in meeting management objectives, and could in some cases undermine sustainability outcomes. Our results also demonstrate that both the intensity with which fishers react to the fluctuations in market price levels and fishers’ perceptions of location attractiveness are influenced by the components of the quota portfolio.

Turbulent flow interacting with flexible trawl net structure including simulation catch in flume tank

The interaction between fluid and the midwater trawl with stocked catches is extremely complex, but essential to improve the understanding of the drag force acting on the trawl, the behavior of the fishing structure during a trawling process, and to predict its selectivity process. The present study assesses the turbulent characteristics inside and around the midwater trawls with catch and without catch linked to its fluttering motion. The analysis is based on three-dimensional electromagnetic current velocity meter measurements performed in the multiple points inside and outside different parts of a 1/35 scaled midwater trawl model with the aim of access the main turbulent flow structure inside and around the gear. Time-averaged normalized flow velocity fields and turbulent flow parameters were analyzed from the measured flow data. Furthermore, Fourier analysis was conducted by watching the time–frequency Power spectrum content of instantaneous flow velocities fields, the fluttering trawl motions, turbulent kinetic energy, and momentum flux. Based on successive analyzes of mean flow characteristics and turbulent flow parameters, it has been demonstrated that the presence of catch inside the trawl net impacts the evolution of unsteady turbulent flow by creating large trawl fluttering motions that strongly affect the flow passage. The results showed that the time-averaged normalized streamwise and transverse flow velocities inside and around the trawl net with catch were 12.41% lower compared with that obtained inside and around the trawl without catch. The turbulent length scale and turbulent Reynolds number obtained in the different part of the trawl net with catch were about 33.05% greater than those obtained on the trawl net without catch, confirming that the unsteady turbulent flow developing inside and around the midwater trawl is influence by the catch and liner. It is observed that the motions of both the trawl without catch and the trawl with catch are mainly of a low-frequency activity and another component related to unsteady turbulent flow street. A complex fluid–structure interaction is then demonstrated where the fluttering motions of the trawl net affect the fluid flow inside and around trawl net, the fluid force, turbulent pattern, and simultaneously, the periodic unsteady turbulent flow influence the trawl motions.

The effect of grid size on catch efficiency and by-catch in the demersal trawl fishery for Norway pout (Trisopterus esmarkii)

Norway pout (Trisopterus esmarkii) is caught with large trawls with small meshed codends, inevitably causing the fishery to have large by-catch issues. To reduce the amount of by-catch, a rigid sorting grid was made compulsory in 2010. However, there is still a severe by-catch issue, as well as the loss of target species because of the grid. A possible cause might be clogging of the grid, which could be solved by increasing the grid area. Therefore, this study compared the size selectivity of by-catch species and target species in a double-trawl configuration in which one trawl was equipped with a standard grid (6.30 m2), and the other trawl was equipped with a grid that had a 50% larger surface area (9.45 m2). The results demonstrated that the size selectivity and catch efficiency of the target species were unaffected; neither was there any significant difference between the two grids in terms of wanted by-catch species [blue whiting (Micromesistius poutassou), horse mackerel (Trachurus trachurus), and greater argentine (Argentina silus)]. However, the larger grid caught significantly more unwanted by-catch species [haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), and hake (Merluccius merluccius)]. Approximately one-third of the accumulated catches comprised the target species, one-third of wanted by-catch species, and one-third of unwanted by-catch species, demonstrating the by-catch challenges in this fishery. Simultaneously, none of the by-catch limits were exceeded.

Trawler Engine Size Had No Effect on Baltic Herring Size/Age Structure: An Experimental Study in the Gulf of Riga, Baltic Sea

The Gulf of Riga stock of Baltic herring (Clupea harengus membras L.) has been maintained through several management tools. One such tool is the restriction of vessels’ main engine power (<221 kW). This restriction was implemented in the early 1990s and is based on the vessel types available in the area and on the assumption that the gear size used in trawl fishery depends on the vessel size (power). In the current study, we compared vessels with different engine powers using the same gears currently allowed in the gulf, to identify whether vessel power had any relation to catch structure. The results showed that engine power did not explain the differences in catch structure, which were more dependent on season and depth of water. Easing the power restriction of the trawl vessels in the Gulf of Riga will most likely not have a major negative impact on the sustainable management of the herring population. However, vessels with higher engine power should not use larger trawl gear than is currently used in the gulf.

Strategy to re-utilization shrimp resources in the Arafura Sea

Shrimp resources in FMA 718 have not been optimally utilized. This study aims to analyze the characteristics of shrimp use after the moratorium policy and formulate recommendations for the use of shrimp in the Arafura Sea that provide maximum benefits for the community. The research was conducted in 2020. The data used in this study are secondary data. The data analysis method used is multi-criteria analysis with the TOPSIS technique. The criteria used include ecological, economic and social aspects with nine criteria. These criteria are the catching range, the potential for shrimp, the effect of shrimp use on shrimp resources and the aquatic environment, the income of business actors, the value of shrimp, the benefits received by the central government, the benefits received by the local government, the possibility of conflict in the use of fishing gear and the area of fishing and labor recruitments. The policy options presented in this study are the option of using shrimp in existing conditions, the option of utilizing shrimp with the addition of a smallscale trawl, the option of utilizing shrimp using small scale trawl and large trawl, and the option of utilizing shrimp only using a large scale trawl. Recommended policy options using the Topsis method which gives the highest ci value, namely option 3.

EKSISTENSI DAN PEWARISAN BUDAYA TUKU DALAM MASYARAKAT PULAU NDAO (ORANG NDAO) KABUPATEN ROTE NDAO NTT

<p>On Ndao Island, Ndao Nuse Subdistrict, Rote Ndao Regency, the people have two prominent skills and have become the livelihoods of the people on the island, namely weaving skills (manènnu) and craftsmen or silversmiths (tuku). The two skills of the above Ndao island community are passed on by parents with informal and non-formal education patterns, but the two cultures experience different developments. Manènnu culture is still developing today among women while tuku culture is almost extinct. To<br />find out the existence and cause of near extinction of Tuku’s skills, this research was carried out with the formulation of the problem as follows: 1) how the existence of silver or tuku craftsmen on Ndao Island; 2) what is the cause of the almost endangered skill of silversmiths or tuku in Ndao Island; 3) how are the efforts of the people of Ndao Island to pass down the culture of silversmiths or tuku to young generation. This study aims: 1) to find out the existence of silver or tuku craftsmen on Ndao Island; 2) to find out the<br />cause of the almost endangered skill of silversmiths or tuku in Ndao Island; 3) to know the efforts of the people of Ndao Island to pass down the culture of silversmiths or tuku to their young generation. The method used in this study is a qualitative research method with interview and observation techniques for data collection. From the results of data analysis it can be concluded the following matters: First, there is an effort of cultural<br />inheritance in society but does not use the right pattern. Second, the lack of interest in the younger generation to learn tuku. Third, the existence of cultural assimilation is the inclusion of a new method of fishing that is using a large trawl boat with a large trawl type so that many young people from Ndao Island who do not want to learn tuku skills and prefer to be subordinates to lampara boats whose income is actually far below the<br />skills of tuku. Besides that, there are many people who pursue seaweed cultivation, the Fourth. The more difficult the silver raw materials in the community. The fifth pattern of cultural inheritance is not done well and well organized.</p>

Vertical and small-scale horizontal distribution of cephalopods in the Charlie-Gibbs Fracture Zone of the Mid-Atlantic Ridge

In summer 2009, NOAA surveyed the nekton fauna of the fracture zone on the Mid-Atlantic Ridge halfway between Iceland and the Azores as a small-scale follow-up to a previous large-scale Norwegian expedition. Midwater sampling with a Norwegian Krill Trawl resulted in 64 discrete-depth samples from 12 stations at depths from near-surface to 3000 m. Seven additional bottom samples were collected with a large trawl at depths of 2000–3500 m. The expedition collected 416 cephalopods in ca. 19 species in the vicinity of the fracture zone. Over 50 hrs of ROV video from the Norwegian expedition was also viewed to determine diel migratory patterns of the most common species of cephalopod in the region, Gonatus steenstrupi, for comparison with the NOAA trawl data. We found that trawl stations southeast of the Subpolar Front were generally most diverse. Cluster analysis showed that midwater trawls were more similar in species composition than bottom trawls. Unlike in the ROV observations, the small G. steenstrupi from trawl samples did not appear to participate in diel vertical migration, suggesting that trawl-caught juveniles are ecologically distinct from those visible in submersible videos.

Massive spawning behavior of the triplespine deepwater cardinalfish Sphyraenops bairdianus Poey, 1861 observed on an offshore sea mount in the West Mariana Ridge

Using a hydrographic echo sounder, we encountered an animal aggregation on a sea mount summit (350 m deep) at the West Mariana Ridge (14°07’ N, 142°48′ E). The aggregation suddenly ascended from the summit at civil dawn, and we were able to capture the ascending aggregation at the next dawn using a large midwater trawl net. Hundreds of fishes captured were determined to be Sphyraenops bairdianus (Poey, 1861). Hydrated eggs in the ovary were histologically confirmed, indicating that this species performed a massive spawning associated with an offshore sea mount and sunrise.

Occurrence of Chiroteuthis mega (Cephalopoda, Chiroteuthidae) in the Northeast Atlantic Ocean Identified by Integrative Taxonomy

A total of eight specimens of the squid family Chiroteuthidae were captured with a large semi-pelagic trawl net over bottom depths of 252–256 m in the NE Atlantic off NW Spain (Galicia, 42°34′N–8°08′E) in April 2016. Three of these specimens were morphologically identified as Chiroteuthis mega. The identification was genetically confirmed using sequences from 18S rDNA, COI and 16S rDNA genes. This finding represents the first in situ identification of individuals of the species caught in the Northeastern Atlantic Ocean, which signifies an extension of its known geographic distribution range. It also expands its known depth range from mesopelagic and bathypelagic depths to epipelagic waters.

Application of a bioeconomic model to Spanish mackerel in the seas of Korea

By focusing on a single species and multiple fisheries, this study provides a stock assessment of the Spanish mackerel caught mostly by Korean large trawl (LT), large purse seine (LPS), and large pair trawl (LPT) fisheries. We standardize the fishing efforts for the three fisheries by using a general linear model. We also employ a surplus production model, the Clarke–Yoshimoto–Pooley (CYP) model, based on the Gompertz growth function. The CYP model estimates the maximum sustainable yield, allowable biological catch (ABC), and associated fishing efforts, while a bioeconomic model is used to estimate the maximum economic yield and associated fishing efforts. Furthermore, the study analyzes the economic interactions among the LT, LPS, and LPT fisheries in the Republic of Korea. The economic analysis compares the net profits of the three different axes accruing to the three fisheries from the estimated ABC. The results show that fishing efforts to catch Spanish mackerel have recently risen in the seas of Korea; however, the stock has reduced because of overfishing. Thus, the study’s findings suggest that total allowable catch management is necessary for single species and multiple fisheries in order to preserve the Spanish mackerel stock in Korea.

Automated measurements of fish within a trawl using stereo images from a Camera-Trawl device (CamTrawl)

We present a method to automatically measure fish from images taken using a stereo-camera system installed in a large trawl (CamTrawl). Different visibility and fish density conditions were evaluated to establish accuracy and precision of image-based length estimates when compared with physical length measurements. The automated image-based length estimates compared well with the trawl catch values and were comparable with manual image processing in good visibility conditions. Greatest agreement with trawl catch occurred when fish were within 20∘ of fully lateral presentation to the cameras, and within 150 cm of the cameras. High turbidity caused substantial over- and underestimates of length composition, and a greater number of incompletely extracted fish outlines. Multiple estimates of individual fish lengths showed a mean coefficient of variation (CV) of 3% in good visibility conditions. The agreement between manual and automated fish measurement estimates was not correlated with fish length or range from the camera (r2=0–0.08). Implementation of these methods can result in a large increase in survey efficiency, given the effort required to process the trawl catch.

History, Biology, and Conservation of Pacific Endemics 2. The North Pacific Armorhead, Pentaceros wheeleri (Hardy, 1983) (Perciformes, Pentacerotidae)

Abstract: North Pacific armorhead (Pentaceros wheeleri) was previously considered rare and was sporadically captured in the eastern and western North Pacific. In 1967, an exploratory bottom trawler of the Soviet Union discovered large aggregations of this species associated with the summits of the Southern Emperor—Northern Hawaiian Ridge (SE-NHR) seamounts. The large trawl catches attracted the participation of commercial bottom trawl fleets of the Soviet Union, Japan, and Korea. Although exploratory fisheries and scientific surveys collected some basic information on the biology of this species, large uncertainties remain due to its peculiar life history. Here we describe the current knowledge and information gaps for the biology and ecology of this species through a review of original scientific literature. The life cycle of this species consists of pelagic and demersal stages. Juvenile and immature fish are widely distributed over the subarctic surface waters of the central and eastern North Pacific Oc...

It takes guts to locate elusive crustacean prey

Mobile crustacean prey, i.e. crangonid, euphausiid, mysid, and pandalid shrimp, are vital links in marine food webs. Their intermediate sizes and characteristic caridoid escape responses lead to chronic underestimation when sampling at large spa- tial scales with either plankton nets or large trawl nets. Here, as discrete sampling units, we utilized in- dividual fish diets (i.e. fish biosamplers) collected by the US National Marine Fisheries Service and North- east Fisheries Science Center to examine abundance and location of these prey families over large spatial and temporal scales in the northeastern US shelf large ecosystem. We found these prey families to be impor- tant to a wide variety of both juvenile and adult dem- ersal fishes from Cape Hatteras to the Scotian Shelf. Fish biosamplers further revealed significant spatial shifts in prey in early spring. Distributions of mysids and crangonids in fish diets shoaled significantly from February to March. Distributions of euphausiids and pandalids in fish diets shifted northward during March. Of multiple hypotheses for these shifts, prey migration is most strongly supported. Rather than only the classic ontogenetic shift from feeding on shrimp to piscivory, of the 25 identified diet shifts in fish predators, 12 shifts were toward increased shrimp feeding frequency with increasing body length.

The origins of the present: economic conflicts in the fisheries of the South African south coast, circa 1910 to 1950

This study investigates the historical roots of the conflict between commercial handline and inshore bottom trawl fisheries on the eastern Agulhas Bank off the southern Cape coast. It focuses on the early 20th century, particularly on the regional centre, Mossel Bay, and on Still Bay, a small town which until recently had an important handline kob fishery. The transport opportunities offered by the commercial harbour and railway line encouraged the establishment of industrialized fishing at Mossel Bay. In contrast, the Still Bay fishery originated in the river as a development of the local agricultural economy, only later pushing out to the sea. Marketing was always hampered by the remoteness and the lack of efficient transportation and refrigeration facilities. Although Mossel Bay handliners had access to ice and transportation, the marketing arrangement of the large trawl companies effectively excluded them from entering markets further afield. Monopolistic vertical integration by the country’s largest trawling company further deteriorated the situation of the independent small handliners. While government was uncomfortable with the trawling companies’ monopolistic practices, it saw the handline sector as a primitive holdover and therefore did not uphold the rights of handline fishers faced with encroachment by trawlers. The Still Bay fishery remained dependent on middlemen, limiting the profitability of the fishery. A tiny fish processing facility operated during WWII, but by and large the regional council sought to maintain the tourism-oriented image of the town. The development of both towns was strongly shaped by government policy and the development of the trawling sector. While the 20th century opened with handlining being the dominant mode of fishing, by the 1950s handline fishing was a marginal economic activity.

Species selectivity in different sized topless trawl designs: Does size matter?

Most demersal trawl fisheries are conducted in a multispecies setting, and the catch consists of several different species. An inherent challenge in such fisheries is to provide both biologically and economically sustainable exploitation of individually fluctuating stocks and vessel- or fleet-specific quotas. The topless trawl design was developed to improve species-specific selectivity in such fisheries. In a topless trawl, the foot rope is located more forward than the headline to allow fish to escape upwards, whereas the headline is located in front in traditional trawl designs. In this study we conducted twin trawls with a topless trawl towed parallel to a similar standard trawl; we tested a topless trawl design on a small trawl with a low headline height and on a larger trawl with a high headline height. We conducted the tows in the Nephrops (Nephrops norvegicus) directed mixed fisheries. For both the small and large trawls, we found a significant topless effect for haddock (Melanogramus aeglefinus) and no effect for Nephrops. For Atlantic cod (Gadus morhua) we found a significant topless effect for the low headline trawl but no effect for the high headline trawl. In both the eastern and western Atlantic, topless trawls have been introduced as legal cod-selective trawl designs. However, this study demonstrates that identical gear modifications made to similar trawls of different sizes and used in the same fishery can lead to different results.

Hog Daddy and the Walls of Steel: Catch Shares and Ecosystem Change in the New England Groundfishery

The U.S. National Oceanic and Atmospheric Administration implemented market-based fishery management in the New England groundfishery as catch shares, controlling aggregate harvests through tradable annual catch quotas allocated to fishing groups called sectors. Policy supporters assert that resulting markets raise conservation incentives. In compliance with the Magnuson–Stevens Fishery Conservation and Management Act, species assessments permit catch shares to replace more spatially and temporally specific constraints on fishing gear, time, areas, and daily harvest limits. Qualitative evidence from field interviews and participant observation questions the efficacy of catch shares. Fishing industry members observe that increased presence of large trawl vessels in previously protected areas damages fish subpopulations and benthic habitat. Regulatory bioeconomic models fail to consider these lay observations. The consequent inability of quota markets to recognize the materiality of human–environment relationships at the spatiotemporal scales of fishing activity, and to internalize associated externalities, may have devastating consequences for the fishery.

A quantitative analysis of greenhouse-gases emissions from the Korean offshore large trawl fishery using an LCA method

Since the Industrial Revolution, mankind faced with the problem of global warming. Each country effort to reduce greenhouse-gases emissions constantly. In the case of Korea, they declared that they will reduce greenhouse-gases voluntarily at “intergovernmental Panel on Climate Change” held in Cancun, Mexico, in 2010. In addition, the government said that they would decrease to 30% of greenhouse-gases emissions figure in 1990 until 2020. Furthermore, they will effort to reduce greenhouse-gases emissions continuously. In Korea, fisheries research of greenhouse-gases is in the beginning stages. Therefore, the generated greenhouse-gases in fisheries should be reduced. It means that we need to quantify the emission of greenhouse-gases.BR In this study, we proposed a quantitative analysis method about greenhouse-gases emissions in fisheries. The greenhouse-gas emissions were derived for producing 1kg of round weight of fish and 1 ㎏ of edible weight of fish quantitatively. In addition, we derived annual greenhouse-gases emissions using the greenhouse-gases emissions for producing 1 ㎏ round weight of fish and the annual production. As a result, the present study will be based for reducing greenhouse-gases emissions.

Quantitative Assessment of the Vertical Distributions of Micronektonic Fishes with Opening/Closing Midwater Trawls

AbstractSome problems of sampling oceanic micronekton with midwater trawls, especially those with opening/closing devices, are reviewed. Contamination of the catches is a major problem with codend opening/closing devices. Avoidance and escapement are perennial problems with small nets typically used by oceanographers. In order to capture the full spectrum of mesopelagic fishes, including agile or large ones, large nets as well as small nets are needed. Large trawls are not practical to use from most research ships, and the volume of water filtered is difficult to measure.

Comparisons of catches of large leptocephali using an IKMT and a large pelagic trawl in the Sargasso Sea

Leptocephali of several elopomorph families can reach sizes of 100–300 mm or larger, but it is questionable if these large eel or notacanth larvae are effectively sampled by small-mesh sampling gear in the open ocean because of net avoidance or insufficient fishing effort. A sampling survey in the Sargasso Sea using both an Isaacs-Kidd Midwater Trawl (IKMT) with fine mesh and a large pelagic trawl with large mesh sizes found that fewer species and individual large leptocephali >100 mm were collected by 25 IKMT tows compared to 4 trawl deployments. Net avoidance of the IKMT by the larger leptocephali appeared to occur at least during the day, and the large trawl did not catch any small leptocephali because of the large mesh size. A combination of net avoidance of the IKMT and greater sampling effort of the much larger mouth-opening trawl seems to have resulted in more large leptocephali being collected by the trawl. This indicates that IKMT surveys undersample large leptocephali species and that large trawls do not sample the whole assemblage of leptocephali. To fully understand the biodiversity and abundance of leptocephali in the world’s oceans, large fine-mesh sampling gear like the IKMT and very large trawls with smaller mesh will likely be needed. This may be important because leptocephali are probably more abundant in the open ocean than is realized, and their role in the ocean surface layer communities and carbon cycle is not understood.