Set-net Fishing Research Articles

Water-Tank and Semi-Field Experimental Investigation of a Hose Net Fish-Hauling Device for Next-Generation Set-Net Fishing

The flexible fire hose and net (hose net) is a novel fish-hauling device developed for set-net fishery. The hose net is placed inside the box chamber net, air is injected from one edge of the hose net, the hoses are inflated, and the buoyancy force is increased. The net floats up gradually, cornering the fish on the other edge. In previous studies, we have conducted a series of floating-up and sinking-down experiments to evaluate the performance of the hose net in calm water. In this study, aimed at the practical implementation of the hose net fish-hauling system, we conducted a water tank experiment and a semi-field test to confirm the operation of the hose net, which was installed inside a box chamber net model. The results demonstrated that the net could float up gradually in an ideal form and stretched on the surface of the box net. The time taken to float up processes varied with the air injected into the auxiliary hose and hose net, so that the motion of the hose net could be controlled by adjusting the air at different parts of practical operation. Furthermore, semi-field trials were conducted to verify its performance in the natural marine environment and its ability to capture schools of fish. Overall, this innovative hose net fish-hauling device is expected to be valuable for next-generation set-net fishing.

Analysis of the positioning factors affecting the sustainable fishing gear-Set net

Using a passive method to catch fish, the set-net fishery is an environmentally friendly fishery posing little risk to the marine ecosystem. To date, no studies have been conducted by industry, government, or academia to formulate a set of physical selection criteria for the installation of set nets. In this study, meteorological and sea condition data were collected around existing set-net fishing grounds in Taiwan, and binary logistic regression analysis and sequential logistic regression methods were used to determine the factors that affect the installation of set nets to confirm the future development of this fishery. According to the results of binary logistic analysis and comparison of physical factors in the waters near Xiaoliuqiu, Pingtung County, Nanliao City, Hsinchu City, Qixingtan City, and Hualien City, where there are set-net fishing grounds, ocean temperature (OCT) and sea surface factors, namely, maximum wind speed (OSWm), wave (WV), air temperature (TEMP) and air pressure (PRES), are the primary factors affecting the installation of set-nets. The results of sequential logistic regression and odds ratio analysis were also used to verify the degree of influence of the determinants of these three sea areas on the nearby set-net fishing grounds. The fish catch data from the fishing grounds studied fitted very well to the examined physical factors in different regions.

Simulation of the capture process in set net fishing using a fish-schooling behavior model

Generally, the catch efficiency (CE) of a set net is difficult to evaluate because it is affected by fish behavior. Therefore, to evaluate CE, we proposed a fish school behavior simulation model based on the boid model and applied it to a full-scale set net. The moving path of the fish school around the set net was simulated and visualized via the proposed method. From the moving path, three behaviors were identified: all individuals entering, all individuals escaping, and the school dividing in the entrance. A Monte Carlo simulation was conducted to evaluate the relationship between set net entrance shape and CE. The entrance net angle (θ) was considered over a range of 55°–90°. The ratio of fish entering the set net was ~ 60% at θ = 60°–90°, and significantly lower at θ = 55°. After entering the playground, over 80% of individuals entered the bag net. When θ = 60°, the ratios of fish escaping from the set net and entering the bag net were at their lowest and highest, respectively. Therefore, maximum CE was achieved at θ = 60°. We conclude that the proposed simulation method will contribute to more efficient set net design.

A preparatory study on fish behavioral properties in a set-net

The fish influx and behavioral properties at a set-net off Goseong, South Korea were investigated using an imaging sonar. As a result, the average influx of fish was 33.9% at day time and 66.1% at night time, respectively, which indicated that a majority of fish entered into a playground in the set-net at night. The fish behavioral properties such as target (fish) length, range, orientation and major-axis angle were examined and compared among survey dates (4, 5, and 6 June 2019) using the statistical analysis tool (analysis of variance, ANOVA). The behavioral properties presented differently sometime of survey dates. This is preparatory study to support fish behavior properties in a set-net. It is expected that more elaborated behavioral information of fishes in the set-net is beneficial for designing and deploying a set-net fishing gear as well as general fish behavior research in the future.

Influence of Spatial-Temporal and Environmental Factors on Larimichthys polyactis, Octopus variabilis, and Species Aggregated Set-Net CPUEs in Haizhou Bay, China

Set-nets are common alongshore fishing gear used in Haizhou Bay, which rely on flow to catch fish. The catch per unit effort (CPUE) of set-net is affected by spatial-temporal and environmental factors but no research has been conducted on this subject. In this study, we used generalized additive models (GAMs) to explore the influence of spatial-temporal and environmental factors on CPUEs of species aggregated, small yellow croaker (Larimichthys polyactis), and octopus (Octopus variabilis) based on logbooks investigations conducted at 4 stations in an alongshore area of Haizhou Bay from 2011 to 2012. The results showed that all CPUEs exhibited significant spatial-temporal differences at various scales. Aggregated CPUE was high when the sea surface temperature (SST) was 15–18°C and 20–23°C, which was mainly determined by life history traits of the octopus and small yellow croaker (optimal SSTs 14–17°C and 19–24°C, respectively). Chlorophyll-a concentration had significant influences on the aggregated, small yellow croaker and octopus CPUEs at optimal ranges of 3.8–6.2 mg m−3, 4.2–4.8 mg m−3 and 4.5–5.5 mg m−3, respectively. Flow through the net had positive relationships with CPUEs. The approximate logarithmic trends in regression curves had a critical point of 2.5 Mm3 d−1, which was the dividing point that differentiated whether the major factor affecting CPUEs was the flow velocity or the fishery resource. Our results from this study will help guide fishery production and improve catch rate of set-net fishing in Haizhou Bay.

Framework and Evaluation of Total Material Requirement for Food Material: Specific TMR for Food Material in Japan

It is of great importance to consider strategic food production to cope with ongoing rapid increases in population. For effective mass food production, addition of fuel for heating, artificial fertilizers, and agricultural chemicals, etc. are indispensable. In order to supply these inputs, a large amount of mining activities accompanied with energy and mineral resources are required, and these are largely hidden flows from the perspective of the consumer. In this study, we have proposed a framework to quantify mining activities relevant to food production in terms of total material requirement (TMR), which has been applied to food material in Japan as a case study. Targeted food material were 41 types of domestic vegetables, 8 types of fruit, 16 types of seafood, and 5 types of livestock. Domestic and foreign livestock feed was also considered. The functional unit was set as “1 kg of food material to be shipped”. The results indicated that the specific TMR (kg-TMR/kg) for food material with similar production methods showed similar values. Generally, contributions by energy were dominant for vegetables cultivated in a greenhouse and fertilizer inputs were dominant for non-greenhouse cultivation. On the other hand, the specific TMR of livestock feed was relatively small compared to vegetables, with no major difference observable among the different feed types. The specific TMR for seafood production by set net fishing was relatively low compared to other fishing and the effects of fishing tools and energy were negligibly small, the effect of energy ascribed to fuel was dominant for other fishing types using boats. For livestock, the specific TMR for a beef cow was 5 〜 6 times as high as that for pigs or broiler hens.

Seabirds, set-nets, and conservation management: assessment of conflict potential and vulnerability of birds to bycatch in gillnets

AbstractSonntag, N., Schwemmer, H., Fock, H.O., Bellebaum, J., and Garthe, S. 2012. Seabirds, set-nets, and conservation management: assessment of conflict potential and vulnerability of birds to bycatch in gillnets. – ICES Journal of Marine Science, 69: 578–589. We addressed the issue of bird bycatch in set-nets in the southern Baltic Sea by (i) assessing the vulnerability of diving birds to drowning by developing a vulnerability index based on weighted bird abundance, (ii) providing information on set-net fishing activities, and (iii) using a spatial overlap approach to indicate the potential conflicts between diving birds and fishing activities. Birds and fisheries concentrated in the same areas. Vulnerability and potential conflict were highest during winter and spring in coastal waters and around shallow offshore grounds. Local bycatch studies validated the usefulness of our approach, which can provide a valuable tool for conservation purposes. Although the conflict analysis outlined the current extent of overlap between birds and fisheries, the vulnerability index indicated important areas and periods in terms of diving bird abundance, irrespective of fisheries, and enabled the development of appropriate conservation and management options. A suite of measures including temporal or spatial restrictions can be derived, despite a scarcity of real data for bycatch rates. This approach is particularly useful for assessing impacts that are difficult to monitor and where mortality cannot be properly addressed, as in artisanal gillnet fisheries. It is also generally applicable to any marine area or species worldwide.

Gillnet fisheries as a major mortality factor of Magellanic penguins in wintering areas

The incidental capture in fisheries is probably the main conservation problem affecting seabirds. While the capture of albatrosses and petrels on longline hooks is well-known worldwide, the bycatch of diving seabirds in gillnets is an overlooked conservation problem. During a winter coastal fishing trip, the capture of Magellanic penguins (Spheniscus magellanicus) was recorded in driftnet and bottom setnet fisheries for the first time in southern Brazil. The highest captures rates were found in driftnets, from 146.5 to 545.5penguins/km2 of net and a total of 56 dead penguins were recorded. In the bottom gillnet, a total of 12 birds were killed and the capture rates varied from 41.7 to 125.0penguins/km2 of net. Although preliminary, the results presented in this paper were consistent between sets. If we consider the magnitude of driftnet and setnet fishing fleets, and that most dead penguins were adults, the impact upon Magellanic penguin populations is probably significant.

Preliminary estimate of incidental mortality of Commerson's dolphins (Cephalorhynchus commersonii) in an artisanal setnet fishery in La Angelina Beach and Ría Gallegos, Santa Cruz, Argentina

The Commerson's dolphin, Cephalorhynchus commersonii, is perhaps the cetacean species most impacted by fisheries in the coastal waters of southern South America, south of 41°S. Between January 1999 and February 2000, 66 Commerson's dolphins were found dead on the coasts of La Angelina and Ría Gallegos, and at least 37 of the ones at La Angelina beach (51°20'S, 069°02'W) were caught incidentally. These captures occurred in gill nets that were set in waters shallower than 15m and mainly for Patagonian blenny (Eleginops maclovinus), silversides (Odonthestes nigricans) and parona leatherjack (Parona signata). The season for set net fishing, extending from the end of August to mid February, overlaps with the breeding season (November-February) of Commerson's dolphins, which is also when this species moves inshore. The estimated catch per unit of effort (CPUE) for gillnets in the area of La Angelina was 0.229 dolphins x (1,000m of net x set)-1. By extrapolation, the estimated total by-catch during the 1999/2000 fishing season in the region of La Angelina and Ría Gallegos was 179 dolphins (SD = 18.8; CI = 141 - 212). Although no abundance estimation of Commerson's dolphins in this region is available, the estimated level of bycatch is concerning. Recommendations for action to mitigate and further document the impact of set gillnets are presented.

定置網漁業における魚群行動に関する研究 ＶＩ 定置網周辺における魚群の出現時刻と来遊

Surveys were carried out at several set-net fishing grounds using a scanning sonar to study the appearance times of each species. Flying fish and salmon were observed in the daytime, while mackerel, sardine and other species during the night and day. Their appearance times were different depending on the species. Set-nets were in operation for 24 hours in order to catch all the different species of fish. The movement behaviour of the spotted mackerel and salmon were also analyzed using the fish number and distribution data that had been gathered from the area under observation. Their movement to and from the coast was caused by their repeated movement behaviour around the set-nets. These movement behaviour patterns were regarded as being attributed to the passive capturing process of the set-nets in relation to diurnal periodicity.

4. 定置綱漁場における魚道について

4. 定置綱漁場における魚道について

Formation and Result of Co-Operative Self-Operation of Pelagic Skipjack Pole and Tuna Long Line Fishery in Southern Kyushu

About 1953 and 1954, fifteen co-operative associations of self-operating pelagic skipjack pole and tuna long line were born at the southern parts of Kyushu (Kagoshima-Pref. & Miyazaki-Pref.) which are well-known for the fishery in Japan. The formation of the associations is one of the ways to protect themselves against the structural pressure in the after-war Japanese fishery. And they are under the political protection to promote the deep-sea fishing and joint operation. But there is only six of them existing now. We can say, this is the same tendency about the associations all over Japan (Tab. 1).This study is intended to classify the factors concerning its success and its failure.Of the factors for its failure, the first is the change of the policy; it was from the promotion of the deep-sea fishery which began to fail about 1955, to the development and structural improvement of coastal fishing. The second is the keen competition for making tuna long line fishing vessels larger among the monopolic giant capitals of fishery. Another reason is the heavy fall of the price for fish because of the experiments of H-bomb at Bikini.There are some factors for the failure inside of the associations. (1) the irrational management, (2) the accidents, e.g. the sinking of the fishing boats, etc. (3) the becoming worse of the economic condition of the associations because of the poor catch of the self-operating set-net fishing which was the economic foundation of the association. The fatal factor among them is the dullness of the self-operating deep-sea fishing brought by the irrational management of above mentioned precapitalistic loose one because of the lack of the experience.All of the five active associations of self-operating deep-sea fishing (Kushikino, Hashima, Bodomari, Makurazaki-shi, Yamakawa-cho) is located at the areas developed by the fishing of bonito and tuna as their chief industry for a long time. But the failures of the nine associations came from the lack of the experiences for that fishing. They were at villages of coastal fishing like set-nets. Furue Fishing Association is the only exception, which had the change from coastal fishing to tuna fishing. But its boat is small one, only 39t. Its economic condition is worse. Its labor power is not enough. Today it is on the turning point for its existence.

Sonobuoyによる魚群検知に関するー実験

The detection of fish shoal by their swimming sound is usually made by research vessels, or, in case of set net fishing, by the cable transmission of under-water sound to coastal receiving stations. To listening simultaneously to the sea noises of several locations or surveying the fish location by the sound originated from fish school, it has been demonstrated that the sonobuoy's disposition offers an easier and more economic survey. The observation is made by setting several sonobuoys at sea and receiving the under-water sound through the radio system at a coastal station. The sonobuoy device consists of hydrophone, audio amplifier, radio transmitter and receiver, speaker, pen-recorder and tape recorder. The under-water signal received by hydrophone is recorded on the penrecorder or on the magnetic tape recorder. The effective communication range of sonobuoy is up to 10km. The observation obtained at fixed set-net fishing ground has demonstrated that the sonobuoy can clearly distinguish the sound of fish school (mainly yellow-tail) from the sea noise, and that the frequency of sound generation at the entrance of set-net has a certain relation with probable catch of yellow-tail. We can conclude that in future, the forecast of fish catch may be possible by listening to the sound of fish by means of such a device.

Sonobuoyによる海中騒音および魚群の水中音の検知(日本航海学会第21回講演会)

The research of sea noise in the ocean or the detection of fish shoal by their swimming sound were usually made by research vessels, or, in case of set net fishing, by the line transmission of under water sound to coastal receiving stations by means of electric cable. For the purpose of listening to the sea noises of several locations simultaneously or surveying the fish location by the sound originated from fish shoal, it has been demonstrated that the "sonobuoy's disposition offers an easier and more economic survey. The observation is made by setting several sonobuoys at sea and receiving the under water sound transmitted through the radio system of a coastal station. The sonobuoy device consists of hydrophone, audio-amplifier, radio transmitter and receiver, speaker, pen-recorder and two channel magnetic tape-recorder. The sonobuoy adopts frequency modulation system at V.H.F. of 42.M.C. band and its effective communication range is up to 10km. The under water signal caught by speaker is recorded on pen-recorder or on magnetic tape-recorder. The observation by this device of the swimming sound of yellowtail in set-net fishing grounds has demonstrated that the sonobuoy can clearly distinguish the sound of yellowtail from the sea noise, and that the frequency of sound generation at the entrance of set-net has a certain relation with probable catch of fish. It is expected in future that we can tell the possibility of catch by listening to the sound of fish by means of this device. We can conclude that in feature, the forecast of fish catch may be possible by listening the sound of fish.