Small Boat Research Articles

Estimating Obstacle Maps for USVs Based on a Multistage Feature Aggregation and Semantic Feature Separation Network

Obstacle map estimation based on efficient semantic segmentation networks is promising for improving the environmental awareness of unmanned surface vehicles (USVs). However, existing networks perform poorly in challenging scenes with small obstacles, scenery reflections, boat wakes, and visual ambiguities caused by unfavorable weather conditions. In this paper, we address the small obstacle segmentation problem by learning representations of obstacles at multiple scales. An efficient multistage feature aggregation (MFA) module is proposed, which utilizes fully separable convolutions of different sizes to capture and fuse multiscale context information from different stages of a backbone network. In addition, a novel feature separation (FS) loss function based on Gaussian mixture model is presented, which encourages the MFA module to enforce separation among different semantic features, thereby providing a robust and discriminative representation in various challenging scenes. Building upon the MFA module and the FS loss function, we present a fast multistage feature aggregation and semantic feature separation network (FASNet) for obstacle map estimation of USVs. An extensive evaluation was conducted on a challenging public dataset (MaSTr1325). We validated that various lightweight semantic segmentation models achieved consistent performance improvement when our MFA module and FS loss function were adopted. The evaluation results showed that the proposed FASNet outperformed state-of-the-art lightweight models and achieved 96.71% mIoU and > 1.5% higher obstacle-class IoU than the second-best network, while running over 58 fps.

Who travels how far: German Baltic sea anglers’ travel distances as precondition for fisheries management and coastal spatial planning

The marine recreational fishery (MRF) is a branch of coastal tourism with noticeable effects on fish stocks, coastal environments, and economies. Nevertheless, little research has been conducted on its spatio-temporal dimensions. This study extends the knowledge about marine angling tourism by investigating activity hot spots and travel distances of 8429 German Baltic Sea anglers using data obtained from an on-site survey which was conducted from 2015 to 2019. Fishing from shores, small boats, and charter vessels, the anglers targeted primarily Atlantic cod and to a lesser extent sea trout, salmon, and herring. Angling effort clustered along the coast primarily according to the available infrastructure and the spatial distribution of the target species. The medians of travel distances differed among the target species and decreased from salmon (261 km), cod (194 km), sea trout (63 km) to herring (44 km). The high percentage of non-resident anglers, most of whom travelled more than 200 km to the coast, suggested that particularly cod and salmonid anglers conducted multiple-day trips and contributed to local economies. The period 2016/17 was characterised by a severe decline of the western Baltic cod stock and the first-time implementation of harvest limitations. The number and travel distances of cod charter vessel anglers decreased after the implementation, whereas the numbers and travel distances of boat and shore anglers targeting cod remained constant despite overall decreasing catch rates. The delineation of areas where marine recreational fishing concentrates may help to define areas relevant for tourism development and destination branding and equally those that require a risk assessment to evaluate the potential extent and consequences of MRF on local environments. The travel distances underlined the heterogeneity of the MRF and may be used as tool to identify stakeholder groups, to estimate the species-specific attractiveness for resident and non-resident anglers, and to evaluate the outcome of management actions.

A SFCW harmonic radar system for maritime search and rescue using passive and active tags

AbstractThis paper introduces a new maritime search and rescue system based on S-band illumination harmonic radar (HR). Passive and active tags have been developed and tested while attached to life jackets and a small boat. In this demonstration test carried out on the Baltic Sea, the system was able to detect and range the active tags up to a distance of 5800 m using an illumination signal transmit-power of 100 W. Special attention is given to the development, performance, and conceptual differences between passive and active tags used in the system. Guidelines for achieving a high HR dynamic range, including a system components description, are given and a comparison with other HR systems is performed. System integration with a commercial maritime X-band navigation radar is shown to demonstrate a solution for rapid search and rescue response and quick localization.

Sound reception system by an acoustic meta-lens

ABSTRACT Applying the directionality of an acoustic meta-lens, a sound reception system for ships is designed. A two-dimensional disk shape acoustic meta-lens or an acoustic Luneburg lens made of 253 acrylic pipes of different radii which control the refractive index is used. The lens has the diameter of 180 cm and the thickness of 20 cm. Eight microphones were installed around the edges of the lens because the lens focuses the input signal into the edge of the other side of the lens. The sound reception ability of the lens was tested on the sea using the horn of a university training ship as an emitter and the lens loaded on a small boat as a receiver. Both are moving at 20 ~ 40 km/h at a distance between 300 ~ 700 m. The lens could focus to recognize the direction of the input sound in the frequency range between 300 and 900 Hz. ABBREVIATIONS IMO: International Maritime Organization ALL: Acoustic Luneburg Lens SRS: Sound Reception System

A Review on Waste-wood Reinforced Polymer Matrix Composites for Sustainable Development

This study reviews the various techniques used in the preparation and processing of waste-wood fibre/particle reinforced polymer matrix composite with special interests on mechanical and structural applications. Polymer composite materials are being used in a wide range of structural applications such as construction, safety wears, aerospace and automotive industries owing to their lightweight, high specific stiffness and strength. A number of materials are being used ranging from lower performance of glass fibre/polyester used in small sail boats and domestic products to high performance of carbon fibre/epoxy systems used in military aircraft and spacecraft. In recent years, many studies have been dedicated to utilize organic fillers such as coconut shell, coir, wood, pineapple leaf, cow bone, palm kernel shell, rice husk. As fillers in order to replace synthetic fillers through utilization of natural fillers or reinforcement in thermoplastic and thermoset polymer composites in an attempt to minimize the cost, manage waste-wood, increase productivity and enhance mechanical properties of composites. Waste-wood as reinforcing fillers in plastics, in place of the previously used inorganic substances and synthetic fibres, offer a major benefit in terms of environmental protection. The benefits offered by waste-wood over synthetic fibres are low densities, non-abrasive, non-toxic, high stiffness and specific properties.

Fa’atsiru Faqlidu Rokat Tase ‘ala ‘aqidatu as-shiyadin

Rokat Tase’ is a tradition or ancestral heritage that is still preserved by coastal communities, especially fishermen. In its implementation, several rituals have become their beliefs which have a major influence on the faith of the local community. One of the rituals in this tradition is Larung Sesaji. This ritual is also one of the relics of the teachings of Hinduism, which is still preserved by the ancestors to date, leaving an impact on the fishermen. This article will discuss the implementation of Rokat Tase ‘in Pakandangan Barat village, Sumenep Madura and its influence on fishermen. Rituals in Rokat Tase’ begin with khatam al-Quran and continue with istighasah, tahlilan, Larung Sesaji that are paraded to the sea in a boat. The a Sesajen were dissolved in the form of food and goods placed in a small boat called Bithek. This ritual is not following the teachings of Islam. Besides that, there is also an art performance and ends with tabligh akbar. Rokat Tase’s implementation affects the faith of the fishermen in Pakandangan Barat village, Sumenep, Madura.

Signal Analysis of Radar Echoes from the Small FRP Boat

Signal Analysis of Radar Echoes from the Small FRP Boat

Climate Staged: The Place of Theatre in The Great Immensity

Steve Cosson and Michael Friedman already had climate change on their minds when they encountered The Great Immensity. Sitting in a small boat in the Panama Canal, conducting research for a new work on environmental issues for their theatre company The Civilians, Cosson, a playwright, and Friedman, a composer and lyricist, were nearly overtaken by a giant container ship with its name etched in Chinese letters across its side (Peters). The ship’s name would become the name of their musical play, and their memory of being overwhelmed by unmanageable and indifferent forces its governing perspective. As Cosson later described it, the experience taught them that the challenge of grasping the full complexity of global ecological crisis, not only its science but also the “economics, policy, political sides of the issue,” feels “like being in a little boat while a great ship goes by” (qtd. in Peters). This anecdote, an...

Red Sea fish market assessments indicate high species diversity and potential overexploitation

In many parts of the world, particularly remote and underdeveloped regions, reports of fisheries catch, effort, and landing data are limited. In order to implement effective fishing regulations to protect natural stocks, understanding fishing pressure, key target species, catch composition, and value of each species is vital. In regions where published data is limited, and the sampling of numerous small boats and landing sites is not feasible, fish market surveys represent an opportunity to obtain key fisheries data. This study therefore aims to obtain species-specific prices and market composition for fish landed in the central Red Sea by surveying local fish markets. We conducted 11 surveys at two major Red Sea fish markets to ascertain key fisheries metrics using market data as a proxy for catch data. Results indicate that a high proportion of the market composition is generated by 46 species from six family-level groups, Serranidae, Labridae, scarine labrids, Carangidae, Lethrinidae, and Lutjanidae, contributing to 87 % of the total market biomass. Species-specific values ranged from 4.50 USD/kg to 26.44 USD/kg, with market surveys highlighting the economic value of three local serranid species: Plectropomus pessuliferus marisrubri, Plectropomus areolatus and Variola louti, all valued at more than 25 USD/kg, and a labrid: Cheilinus undulatus, valued at 26.44 USD/kg. The Serranidae family represents 47 % of the total biomass and 55 % of the potential revenue in the market, while also indicating potentially overfished reefs due to the high occurrence of smaller species and undersized individuals of higher priced serranid species. Many of the high-valued serranids were below the size at sexual maturity. Target species exhibited small body size and decreasing abundance, potentially indicating a “shrinking baseline” scenario occurring in the Saudi Arabian artisanal coral reef fishery. These results indicate that introducing effective fisheries legislation and management is necessary for the longevity and sustainability of the reef-based fishery in the Saudi Arabian Red Sea. Implementing catch quotas, size limits, and seasonal restrictions are potential mechanisms that could be used to facilitate positive change within this vulnerable fishery.

Factors Related to Operational of Marina in West Coast Malaysia

Marina is a mooring facility or port located on a body of water that provides service for a small boat and yacht. The marinas in Malaysia are managed by private companies and few by Marine Department Malaysia. There are successful marinas in Malaysia. However, some marinas failed. This study aims to identify the factors to establish a successful marina and to identify factors that certain marina is less performed or failed. To identify the factors, the literature review and survey is performed to marina operators in Malaysia. The method used to analyse the data was the Analytic Hierarchy Process (AHP). Results showed that the identified factor are the location, services, and facility are the most important to establish the marina. The factor has a relationship with others, and the high possibility factor should be taken to establish a marina.

Book review: Dobeson A, 2019: Revaluing coastal fisheries: how small boats navigate new markets and technology, Palgrave Macmillan, Switzerland.

How nature interfaces with markets, influences technology and in turn conditions the way humans organize their lives is not a common theme dealt with by economists or sociologists. Perhaps, this is due to the fact that most studies of market, technology and institutions deal with sectors of the economy and society where the determining influence of nature per se is not of much consequence. Nature may be present, but is very much in the backdrop.

Winds, waves, warm waters, weekdays, and which ways boats are counted influence predicted visitor use at an offshore fishing destination

Quantifying the number of recreational fishers is important for many aspects of managing coastal resources. Unfortunately, quantifying recreational boaters in offshore settings has proven difficult due to their distance from shore and a lack of cost-effective methods to monitor small boats (<10 m length). We investigated visitor-use at an offshore marine protected area (MPA) in the southeastern USA. We used multiple methods of counting boats (satellites, buoy camera, passive acoustics, and boat-based observations) and a generalized linear modeling approach to identify environmental and calendar-based predictor variables that influenced visitation. Based on the model, predicted visitor-encounter rates were estimated for various weather and calendar-based scenarios, and the probability of detecting a hypothetical change in visitation with each counting method was examined through a power analysis. The most important predictors were day of the week, special day (e.g., tournament), water temperature, and wave height. Boat counts were 2–5 times higher on weekend days than on weekdays. More boats were predicted on weekdays with good weather (defined as water temperature 24 °C, wave height 0.5 m), than weekends with decent weather (17 °C and 1 m). Considering weekends alone, those with good weather were predicted to have 5 times higher visitation than weekends with decent weather. Predicted visitation was highest on calm days, dropped by ∼75 % when wave height reached 1 m, and was essentially zero when wave height exceeded 1.5 m. Highest counts were predicted when water temperature was warmest and gradually declined as temperatures cooled. For the buoy camera and passive acoustic boat-count methods, power analysis suggested that 3–6 years of typical samples before and after a hypothetical 25 % increase in visitation would be needed to have an 80 % chance of detecting the change. Other techniques would take 14 or more years of typical samples. The process used here for investigating visitation can be adapted to other offshore or remote locations.

Anthropogenic and natural inputs of polycyclic aromatic hydrocarbons in the sediment of three coastal systems of the Brazilian Amazon.

Polycyclic aromatic hydrocarbons (PAHs) were measured in 32 surface sediment samples collected around three cities (Barcarena, Belém, and Santana) located on the coast of the Brazilian Amazon. The concentration of total PAHs ranged from lower than detection limit to 33,101 ng g-1 in a sample from Barcarena and was related to a large aluminum industrial complex and port activities. In Belém, which is the most populated area in the Amazon region, PAHs were probably derived from untreated sewage discharge and inputs from a large municipal landfill. Pyrogenic PAHs were predominant in both cities, with a smaller contribution of petrogenic PAHs. Low alkylated PAH levels may be associated with small boats and ship traffic. Santana had low total PAH concentrations, with a predominance of unusual alkylated PAHs, probably related to diagenetic transformations of organic matter in the sediment. In general, PAH concentrations in the samples were low and may reflect baseline levels for this Amazon estuarine system.

Comparison of In Situ and Remote-Sensing Methods to Determine Turbidity and Concentration of Suspended Matter in the Estuary Zone of the Mzymta River, Black Sea

The paper presents the results of a comparison of water turbidity and suspended particulate matter concentration (SPM) obtained from quasi-synchronous in situ and satellite remote-sensing data. Field measurements from a small boat were performed in April and May 2019, in the northeastern part of the Black Sea, in the mouth area of the Mzymta River. The measuring instruments and methods included a turbidity sensor mounted on a CTD (Conductivity, Temperature, Depth), probe, a portable turbidimeter, water sampling for further laboratory analysis and collecting meteorological information from boat and ground-based weather stations. Remote-sensing methods included turbidity and SPM estimation using the C2RCC (Case 2 Regional Coast Color) and Atmospheric correction for OLI ‘lite’ (ACOLITE) ACOLITE processors that were run on Landsat-8 Operational Land Imager (OLI) and Sentinel-2A/2B Multispectral Instrument (MSI) satellite data. The highest correlation between the satellite SPM and the water sampling SPM for the study area in conditions of spring flooding was achieved using C2RCC, but only for measurements undertaken almost synchronously with satellite imaging because of the high mobility of the Mzymta plume. Within the few hours when all the stations were completed, its boundary could shift considerably. The ACOLITE algorithms overestimated by 1.5 times the water sampling SPM in the low value range up to 15 g/m3. For SPM over 20–25 g/m3, a high correlation was observed both with the in situ measurements and the C2RCC results. It was demonstrated that quantitative turbidity and SPM values retrieved from Landsat-8 OLI and Sentinel-2A/2B MSI data can adequately reflect the real situation even using standard retrieval algorithms, not regional ones, provided the best suited algorithm is selected for the study region.

Efficiency management in catch handling onboard small boats – Standardisation of processes in Icelandic fisheries

• Icelandic small boat fishers central to economic prosperity of remote communities. • Applied research methods used to develop exemplar standards for onboard catch handling. • Eight recommendations formed relating to safety, ergonomics, hygiene and fish handling. • Adoption of recommendations could lead to gains in time and resource efficiency. • Standardisation also likely to reap benefits in at least five Sustainable Development Goals. Small boat fishers are often the lifeblood of remote coastal communities in Iceland, contributing to employment, jobs and economic prosperity. This study conducts exploratory but highly practical research into the productive efficiency of onboard catch handling practices by Icelandic small boat fishers using fish handling tools called automatic jigging machines. Using applied research methods, this study researches whether standardisation of operations could be applied to make catch handling practices on small boats more time and resource efficient, leading to reduced waste, a consistently higher quality product, and potential increases in economic efficiency and sustainability. Thematic analysis, value stream mapping, flow analysis and Kaizen ideology were adopted to identify gaps and continuous improvement opportunities to standardise processes, leading to exemplary performance. Eight core recommendations are identified, seven of which are classed as straight-forward, ‘do now’ measures according to a Kaizen Priority Matrix. These include human and technological interventions in the areas of safety, organisational arrangements, hygiene, fish handling and bleeding, and cooling. Questionnaire responses reveal four main themes of importance to the sub-sector: changes in recent decades; the importance of small boat fishers; education and improvement; and the particularities of the sub-industry. The latter include the perception of a ‘race against time’ to land the catch, an issue that sometimes contributes to sub-optimal catch handling practices. Although this study has decidedly practical connotations for small boat fishers, its outcomes are also likely to be of interest to academics, particularly those focused on the organisational management of natural resources and general applications of the project management methodology and applied research methods as a means of solving practical problems in everyday life.

Reduction of roadway noise in a coastal city underwater soundscape during COVID-19 confinement.

Confinement due to the COVID-19 pandemic drastically reduced human activities. Underwater soundscape variations are discussed in this study, comparing a typical and confinement day in a coastal lagoon near a popular tourist city in Mexico. Recording devices were located at 2 m in depth and 430 m away from the main promenade—a two-way avenue for light vehicle traffic—where main tourist infrastructure is located. The nearby marine environment is habitat to birds and dolphins as well as fish and invertebrates of commercial importance. Medium and small boats usually transit the area. The main underwater sound level reduction was measured at low frequencies (10–2000 Hz) because of the decrease in roadway noise. Vessel traffic also decreased by almost three quarters, although the level reduction due to this source was less noticeable. As typical day levels in the roadway noise band can potentially mask fish sounds and affect other low frequency noise-sensitive marine taxa, this study suggests that comprehensive noise analysis in coastal marine environments should consider the contribution from nearby land sources.

Development of a Small Electric Robot Boat for Mowing Aquatic Weeds

HighlightsA small, automatically guided electric robot boat was developed to control the growth of aquatic plants in lakes.The robot boat was able to mow without becoming entangled with aquatic plants due to the paddle propulsion mechanism.The average speed was 0.41 m s-1, and the lateral deviation from the set path was 9.4 cm.The growth restraint effect was confirmed using aerial images collected by a drone.Abstract. At present, aquatic plants are becoming a problem in various lakes. Aquatic weeds that grow to high densities cause decreases in the oxygen concentration in the water, accumulation of sludge, and adverse effects on water use facilities and fisheries. Although there are large machines for cutting and harvesting aquatic plants, their use is limited due to their high cost, large size, and heavy weight. On the other hand, manual cutting is very labor intensive and inefficient. Therefore, in this research, we developed a labor-saving and low-cost robot boat to mow aquatic plants. This robot boat is automatically controlled by a real-time kinematic global navigational satellite system (RTK-GNSS) and is characterized by its small size, light weight, excellent portability, and low energy consumption. In addition, a paddle mechanism that replaces a conventional propeller was introduced as a propulsion mechanism to prevent entanglement of water plants and enable long-term automatic navigation. Mowing lotus (Nelumbo nucifera) in Lake Izunuma, Miyagi prefecture, Japan, confirmed that mowing could be properly conducted with a lateral deviation of 9.4 cm, average speed of 0.41 m s-1, and average power consumption of 518 W even when lotus was at its densest growth. If the cutting width of the robot boat was 1.2 m and the sidelap width was 0.3 m, the theoretical field work rate would be 0.133 ha h-1. Images captured by a drone confirmed that cutting with the robot boat was effective in suppressing the growth of lotus. It was found that the effect of suppressing growth was maximized by mowing at the time when the stopping leaves appeared in the late growth stage of lotus. Keywords: Autonomous navigation, Lotus, Moving baseline, Robot operation system, RTK-GNSS, Virtual private network.

Afterword

Afterword Rodrigo Lazo Some years ago, before starting graduate school, I travelled to the Galápagos Islands. As someone originally from Ecuador, I was aware that the islands are a province of the "República del Ecuador" but also very far from the coastal and Andean regions that are the economic and political strongholds in my country of birth. Anyone who has managed to reach that archipelago knows that to experience the natural variety of the group it is necessary to navigate from one enchanting island to another. Galápagos tourism has always relied on local small boats and yachts taking tourists to the different islands, and it was aboard the appropriately named Albatross that I stumbled on a collection in the ship's tiny library containing "The Encantadas; or, Enchanted Isles." The sketches offered Galápagos lore shared by guides as part of the visit—stories of buccaneers and castaways. It also became quickly apparent that the sketches did not seem to be about the islands before me. As I stared at the volcanic formations and contemplated the friendly animal-life, the Galápagos looked nothing like "five-and-twenty heaps of cinders dumped here and there in an outside city lot" (Piazza Tales 179). Nor were they as elusive as Salvator R. Tarnmoor's delusional account conveys. While I do not regularly look for veracity in fiction—and Melville's invocation of sites and references in South America are not always invested in accuracy—the difference between what I apprehended in the Galápagos and the sketches prompted questions that continue to hang like an albatross around my neck: Why was a writer associated with US literary nationalism engaging with locations that were distant to his New England home and also distant from the part of Ecuador where I had been born? And what kind of referential weight did these sketches carry for Melville's work and, more generally, the way people in the United States view Latin America? With those questions foremost, I note that three of the five pieces in this special issue on Melville and the region we are calling "Spanish America" place "The Encantadas" at the center of their arguments and take a variety of approaches: philosophy and epistemology, questions of allegory, and a US-centric historicism. Those very different critical directions appear to pull away [End Page 103] from Spanish America and remind us of the complicated relationship of "The Encantadas" to the geographic destination that inspires its organization. Anna Brickhouse, for example, argues that the sketches dwell in "a space of philosophical rupture, a vantage point for meditation on the West: its enduring problem of evil, its invention of the human, and its perpetual creation of theodicies that justify the world's racial and geographical apportionment of suffering" (37–8). In connecting her interpretation to Western thought more generally, Brickhouse offers a more ample terrain than the very geographic location that draws the sketches. Taking a different approach, Yoshiaki Furui reads "The Encantadas" in relation to the temporality of the discourse of Manifest Destiny and the teleology of Euro-American modernity. These types of shifts should be no surprise given that, as I have noted, the Galápagos themselves are geographically and culturally distant from the mainland. Long uninhabited by humans, the islands are "Spanish" only in the poetry of colonial assumption. Both historically and in Melville's sketches, the Galápagos are distant geographically from the area we associate with Spanish America. As such, "The Encantadas" offers a series of literary and cultural dislocations and critical navigations that send readers in a variety of directions. The contributors to this special issue follow that spirit and see "Spanish America" as an opportunity for departure as much as a necessary critical stopping point when reading Melville. The special issue makes a convincing case for the importance of "Spanish markers" as a set of referents in Melville's writing. As Emilio Irigoyen shows in his textually attentive introduction, some of Melville's Spanish American images, words, and motifs return from one text to another. These range from humorously off-handed remarks by narrators to more serious contemplation about the implications of a hemispheric American...

Boat hull assembly methods and provision manufacturability of their designs

The design and technological characteristics of modern boats are presented and the technology of block assembly of hulls of large boats, as well as of frame assembly of hulls of small boats, is described. The design and the principle of operation of the equipment used, such as slipway-conductors and readjust able beds, providing the possibility of assembling the hulls of small boats from pre-made modules of the outer skin, representing its development in the plane, are considered. Particular attention is paid to the structural and technological improvement of boat hulls, aimed at replacing welded stiffeners with stamped corrugations and assembly welded joints of the outer skin — mechanical joints on pressed elements made of aluminum alloys. In accordance with the requirements for ensuring quality and reliability of the assembly of boats hulls, as well as their structural and technological improvement, the methods of tightness control used in domestic and foreign shipbuilding are considered.

Automated content analysis of the Hawai&amp;#699;i small boat fishery survey reveals nuanced, evolving conflicts

Automated content analysis of the Hawai&amp;#699;i small boat fishery survey reveals nuanced, evolving conflicts