Underwater Video Research Articles

Caracterización de las comunidades ícticas de charcos intermareales en la isla de Tenerife

The island of Tenerife has experienced significant population growth and urban development in coastal areas, resulting in a negative impact on the ichthyic communities associated with its intertidal pools, which act as a refuge and nursery for a large number of species, many of them of fishing interest. In order to characterize these populations and know their conservation status, sampling was carried out using baited remote underwater video (BRUV) in four areas in Tenerife located on the north coast, Punta del Hidalgo and Finca El Apio, and on the south, Las Galletas and Punta Rasca. A total of 13 fish species were found throughout the sampling, 7 of them of fishing interest in the Canary Islands. According to the results obtained, a significant variation can be seen between the communities of the sampled localities. Specifically, it was observed that Punta del Hidalgo has the highest fish abundance and richness of species. On the other hand, it was found that the locality of Las Galletas differs significantly from the rest, presenting a low abundance of species, especially those of fishing interest.

Elasmobranch diversity around the southern Caribbean island of Tobago: opportunities for conservation in a regional trade hub

Abstract Sharks are scarce in much of the Caribbean due to widespread depletion. Trinidad and Tobago, in the southern Caribbean, is a shark meat consumer and international exporter of dried shark fins. Despite limited fisheries management there is a small Marine Protected Area (MPA; 7 km2) in urbanised southwest Tobago, but its effect on sharks and rays (elasmobranchs) is unknown. The rural northeast is a recently designated UNESCO Man and the Biosphere Reserve with a significant marine component and plans for a large MPA, but no baseline data for elasmobranchs exist. Given the local importance of elasmobranchs and a newly drafted Sustainable Shark and Ray Management Plan, we used baited remote underwater video stations within a 40 m depth contour at 270 randomly generated points around Tobago to: (i) establish a baseline of species richness and relative abundance, (ii) investigate the influence of season, habitat relief, depth and water temperature on relative abundance, and (iii) investigate spatial variation in relative abundance. Caribbean reef sharks, nurse sharks, and southern stingrays were observed at all sites, the latter two more frequently in the urbanised southwest. Shark diversity was unexpectedly high in the northeast, driven by rarer species (sharpnose, smoothhound, tiger, scalloped hammerhead, great hammerhead) only observed there. Habitat relief, depth and season likely influence relative abundance of elasmobranchs around Tobago, but research is needed to elucidate species-level effects. Shark species richness in northeast Tobago is high for the Caribbean, warranting research attention, while the larger MPA presents an opportunity to strengthen elasmobranch management.

Comparison of traditional and molecular surveys of fish biodiversity in southern Te Wāhipounamu/Fiordland (Aotearoa/New Zealand)

AbstractEffective management of biodiversity requires regular surveillance of multiple species. Analysis of environmental DNA (eDNA) by metabarcoding holds promise to achieve this relatively easily. However, taxonomy‐focused eDNA surveys need suitable molecular reference data, which are often lacking, particularly at the species level and for remote locations. To evaluate the comparability of environmental DNA surveys and traditional surveys in a real‐life case study in a marine area of high conservation value, we conducted a biodiversity survey of the fish in remote and pristine Te Wāhipounamu/Fiordland (Aotearoa/New Zealand), incorporating multiple data sources. We compared eDNA‐derived species identifications against Baited Remote Underwater Video (BRUV) data collected at the same time and locations as eDNA. We also cross‐referenced both eDNA and BRUV data against literature and the Ocean Biodiversity Information System (OBIS), with literature and OBIS data representing a summary of multiple traditional surveying approaches. In total, we found 116 fish species in our study area. Environmental DNA detected 43 species; however, only three of those species overlap with species known from the literature, OBIS, or our BRUV analyses. A total of 61 fish species were known from the region from the literature, while OBIS listed 28 species, and our BRUV analyses picked up 26 species. BRUV data coincided more strongly than eDNA data with literature and OBIS data. Twenty of the 26 species detected by BRUV were known from literature and OBIS. We argue that limitated DNA reference databases are the main cause of this discrepancy, and our results indicate that eDNA of rare and endangered species can be detected if matching reference data were available. Environmental DNA analyses can only identify species present among reference data and with relaxed taxonomic assignment parameters may converge on relatives of detected species if the actually existing species themselves are missing among reference data. However, the high number of species detected by our eDNA analyses confirms that eDNA could be a powerful tool for biodiversity surveys if suitable investments in local reference databases were made.

Designing, implementing and monitoring the translocation of a highly threatened freshwater fish

Abstract Conservation translocations are increasingly applied for the protection of threatened species, but their success depends strongly on pre‐release preparatory work and strict implementation methodology, followed by post‐release monitoring. The aim of this work was to implement a conservation translocation that involved (a) the design and application of a pre‐release feasibility assessment tool for the selection of the translocation water bodies; (b) the translocation of 77 individuals of the highly threatened freshwater Corfu killifish Valencia letourneuxi in 2015, 2016 and 2017; and (c) a 5‐year post‐release monitoring with multiple methods. After initial pre‐screening, a feasibility assessment was conducted on two potential release water bodies (R‐WBs) and on four potential source water bodies (S‐WBs), using a custom‐made feasibility assessment tool that incorporated 14 criteria for the potential R‐WBs, related to the species' habitat requirements, human pressures and technical issues. Two criteria were applied to the potential S‐WBs, on source population availability and on its genetic compatibility to the release area. Post‐release monitoring (2017–2022) was conducted with fish sampling methods, underwater video recording and/or using environmental DNA (eDNA). The feasibility assessment tool gave one R‐WB high, positive score, and one S‐WB met both criteria, thus these selected as the translocation water bodies. Despite the low number of founders, the establishment of a self‐reproducing population was finally confirmed in 2022 in the R‐WB, initially with video recording and subsequently by fish sampling and eDNA. This study highlights the importance of pre‐release feasibility assessment, the use of multiple post‐release monitoring methods and actions to secure the long‐term viability of the translocated population. The feasibility assessment tool and the methodological protocol can easily be modified for successful application to other freshwater fish species, with different habitat requirements, current and future human pressures and genetic constraints.

Automated identification of invasive rabbitfishes in underwater images from the Mediterranean Sea

Abstract Coastal ecosystems of the Mediterranean Sea are among the richest in non‐indigenous species, mostly due to the establishment of species coming from the Red Sea through the Suez Canal. Two herbivorous rabbitfishes, Siganus rivulatus and Siganus luridus, are already invasive in the south‐eastern part of the Mediterranean Sea where they cause ecological damage by overgrazing algae. The early detection and the counting of these non‐indigenous species in the rest of the Mediterranean Sea is thus a major challenge for scientists and ecosystem managers. However, analysing images from divers or remote cameras is a demanding task. Here, a dataset of 31,285 images of Siganus spp. and of six common native fishes to the Mediterranean Sea was built from 40 underwater videos recorded at three reef habitats. A deep learning algorithm was then trained to identify Siganus spp. on images containing the eight Mediterranean species. Finally, the algorithm and a post‐processing filtering were tested with an independent dataset of 2024 images. The model had a recall of 0.92 for the Siganus genus (i.e., two Siganus species combined). After a confidence‐based post‐processing, the recall increased to 0.98 with only 4 out of 272 images of Siganus spp. being misclassified. Accuracy reached a score of 0.61 meaning that experts would have to discard false positives. Images of five native species not present in the training dataset yielded similar false positive rates than species present in the training dataset. Overall, the automatic processing of images by the model and then the checking of putative Siganus images by experts required up to five times less effort than a full processing by experts. The algorithm can help to efficiently detect these two invasive fishes in underwater images to evaluate progress towards conservation objectives and accelerate citizen‐based monitoring of coastal ecosystems.

Feature Matching-Based Undersea Panoramic Image Stitching in VR Animation

The continuous development of virtual reality animation has brought people a new viewing experience. However, there is still a large research space for the construction of virtual scenes. Underwater scenes are complex and diverse, and to obtain more realistic virtual scenes, it is necessary to use video panoramic images as reference modeling in advance. To this end, the study uses the [Formula: see text]-means clustering method to extract key frames from underwater video, and adaptively adjusts the number of clusters to improve the extraction algorithm according to the differences in features. To address the problems of low contrast and severe blurring in underwater images, the study uses an improved non-local a priori recovery method to achieve the recovery process of underwater images. Finally, the final underwater panoramic image is obtained by fading-out image fusion and frame to stitching image synthesis strategy. The experimental analysis shows that the runtime of Model 1 is 21.46[Formula: see text]s, the root mean square error value is 1.89, the structural similarity value is 0.9678, and the average gradient value is 12.59. It can achieve efficient and high-quality panoramic image generation.

Species‐specific foraging behavior and diets of stream salmonids: An implication for negative impacts on native charr by nonnative trout in Japanese mountain streams

AbstractSalmonids have been introduced globally as a food source and recreational fishing target. In Japan, brown trout (Salmo trutta) and brook trout (Salvelinus fontinalis) were introduced in the 19th century and have since spread. In many headwater streams, native white‐spotted charr (Salvelinus leucomaenis) are thought to be experiencing negative impacts from these species. The current study examined foraging behavior, microhabitat use, and diet overlap of these three species in Kamikochi, Nagano Prefecture: one of Japan's premier mountain areas. In Kamikochi, many spring‐fed headwater streams are currently dominated by these invasive salmonids and white‐spotted charr have declined drastically over the last half century. Underwater video analysis revealed that while total foraging rates and foraging modes were similar between the three species, brook trout and white‐spotted charr foraged benthically more frequently than brown trout. Microhabitat water depth and flow velocity were similar between species, and fish size had a positive effect on water depth and flow velocity in all three species. Diet analysis indicated that brook trout and white‐spotted charr diets were nearly identical, comprised primary of aquatic invertebrates, while brown trout preyed on a mix of terrestrial and aquatic invertebrates, as well as amphibians and fish. These results indicate that in Kamikochi, the decline of white‐spotted charr is likely most influenced by direct competition with brook trout for prey resources. However, brown trout likely also predate on juvenile white‐spotted charr, while also possibly causing a foraging niche shift of white‐spotted charr, and have ecosystem‐level impacts due to predation on terrestrial prey.

Lophelia reefs off North and West Africa–Comparing environment and health

The health status of cold-water coral reefs on the West African coast was investigated with the main objective of obtaining knowledge of the adaptive capacity of Lophelia pertusa to environmental stressors. Three coral sites were studied, in Northern Morocco, in the Morocco/Mauritania region (both in 2020) and, in the Ghana and Ivory coast region (visited in 2012, 2017, and 2019). Area cover of live colonies, explored through underwater videos, was used as an indicator of reef health and compared with the environmental variables: reef position, depth, water mass, temperature, dissolved oxygen concentration (DO), carbonate chemistry (pH, aragonite saturation (ΩAr), macronutrients and particles (visual). For a broader picture of the adaptations presented by Lophelia our results were compared with reefs in contrasting environments. Off Ghana and Mauritania healthy reefs (i.e., having areas with more than 20 % cover of live colonies) were found to reside at DO concentrations between 1.1 and 1.6 ml L−1, in corrosive waters (pH 7.7 and ΩAr 1.0) with high nutrient concentrations. By contrast, the reefs off the North of Morocco, sitting in well-oxygenated waters with oversaturated ΩAr, had no or few live colonies. Our findings together with data from other studies show that Lophelia has a wide tolerance to hypoxia and acidification, and that in relation to climate change increased temperature and silting could pose more serious threats. These findings highlight the importance of continued studies of Lophelia reefs in contrasting environmental conditions to better understand their adaptation potential to climate change-related stressors.

Temperate rocky reef fish community patterns in a coastal marine protected area (MPA) from northern Chile, utilizing remote underwater video cameras (RUVs)

Shallow water seascapes are complex systems, important for the life history and connectivity of many marine fish species. Remote Underwater Video cameras (RUVs) are an increasingly used, non-lethal technique able to record the occurrence of reef fish species with little disturbance. In this study, RUVs were installed in a Marine Protected Area (Chañaral Island, northern Chile, 29°2'S, 71°34'W) at three different depth strata (5, 10, 15 m) in three different habitats (sand and boulder, bedrock, and kelp forest) during October 2018, July 2021 and October 2021. The RUV system recorded a total of 20 species belonging to 16 families over 73.5 h of videotaping. The most recurrent fishes were damselfish Chromis crusma, Chilean sandperch Pinguipes chilensis, and marblefish Aplodactylus punctatus. There was a significant difference in fish assemblage composition among depth strata and seasons, but not among habitats. In July 2021 (austral winter) higher densities of small cryptobenthic fish (Helcogrammoides spp.) and medium-sized carnivorous Chirodactylus variegatus were detected, whereas P. chilensis was associated to the deeper stratum, and the herbivorous blenny Scartichthys viridis was related to the shallower depths, which is likely due to differences in the habitat structure and composition. Winter 2021 showed a higher species richness than in spring 2018, while the evenness (Pielou’s J’) was significantly higher in spring 2018 than winter/spring 2021. There was no other strong or consistent pattern, which suggests that most fish species use the entire depth gradient throughout the year. Finally, the results suggest that the use of RUVs for the estimation of biodiversity of rocky reef fishes is a cost-effective way to improve our understanding of nearshore community shifts in relation to environmental forcing.

Applying collective motion models to study discordant individual behaviours within a school of fish.

Computational models of collective motion successfully reproduce the most common behaviours of a school of fish, using only a few elementary interactions between individuals. However, their ability to also reproduce individual behaviours that are discordant from those of the group has not yet been adequately investigated. In this paper, a self-propelled particle model using three interaction zones is considered in relation to the counter-rotation of an individual: a phenomenon observable in real schools of fish milling in a torus, when an individual moves in the same torus but in the opposite direction for a certain period of time. This study shows that the interactions of repulsion, orientation and attraction between individuals moving at constant speed in a three-dimensional space, with asynchronous updating, can generate temporary counter-rotations. The analysis of such events sheds light on the mechanisms that start the counter-rotation and those that end it. Although the contribution of the repulsion interaction is often significant to start and terminate the counter-rotation, it does not prove to be decisive. Indeed, it is observed that even when interactions between individuals are limited to attraction alone, temporary counter-rotations of individuals occur, provided the fish density along the circumference is not uniform. Some of these conclusions, deduced from the simulations performed, are visually consistent with what is observed in some underwater video recordings of milling schools of fish.

Colour change and colour phases in Lethrinidae with insights into ecology.

Colour change is used by a wide range of animals. It is used for intra- and interspecific communication and crypsis, and can occur on morphological and physiological levels. Bony fish employ rapid physiological colour change and display various types of patterns and colouration (colour phases) useful for aposematic and cryptic purposes. Using an existing database of benthic stereo-baited remote underwater video systems from two locations in Western Australia, we tested whether the frequency of colour phases of emperors, Lethrinidae, varied by species. We described colour phases and rapid physiological colour change in 16 species of lethrinids, and related occurrences of colour change to feeding activity and life stages. Dark and light colour phases were observed in nine of the 16 evaluated species of which seven also displayed physiological colour change. Frequency of colour phases varied between species, suggesting that the display of different dark patterns may be especially important for certain species. Both juveniles and adults showed the ability to change between different colour patterns. The change into a mottled pattern mainly occurred while feeding or when approaching to feed, suggesting that it may be triggered by feeding and the associated decrease in environmental awareness. Colour change is a commonly observed strategy in lethrinids and may have evolved as an adaptation for increased foraging success or to reduce aggression from conspecifics. Physiological colour change allows lethrinids to quickly adapt to various cues from the environment and can therefore be considered a versatile physiological mechanism in this family.

Fish Detection under Occlusion Using Modified You Only Look Once v8 Integrating Real-Time Detection Transformer Features

Fish object detection has attracted significant attention because of the considerable role that fish play in human society and ecosystems and the necessity to gather more comprehensive fish data through underwater videos or images. However, fish detection has always faced difficulties with the occlusion problem because of dense populations and underwater plants that obscure them, and no perfect solution has been found until now. To address the occlusion issue in fish detection, the following effort was made: creating a dataset of occluded fishes, integrating the innovative modules in Real-time Detection Transformer (RT-DETR) into You Only Look Once v8 (YOLOv8), and applying repulsion loss. The results show that in the occlusion dataset, the mAP of the original YOLOv8 is 0.912, while the mAP of our modified YOLOv8 is 0.971. In addition, our modified YOLOv8 also has better performance than the original YOLOv8 in terms of loss curves, F1–Confidence curves, P–R curves, the mAP curve and the actual detection effects. All these indicate that our modified YOLOv8 is suitable for fish detection in occlusion scenes.

Comparative Trophic Levels of Phragmocone-Bearing Cephalopods (Nautiloids, Ammonoids, and Sepiids).

Cephalopods are among many marine animals that through some combination of habit and/or habitat have proven difficult to study, especially understanding their trophic positions in marine communities. Stable isotope analyses have provided powerful tools for discovering quantitative aspects about the ecology and food sources of many cephalopod species. Here, we present new gut content and isotopic data (carbon and nitrogen isotopes) from phragmocone-bearing cephalopods (both ectocochleates, as well as those with internal, hard part buoyancy maintenance apparatuses). To this, we also include observations from baited remote underwater video systems to describe feeding habits and potential prey types to correlate with gut contents analyses. These data come from extant Allonautilus, Nautilus, and Sepia species, as well as from extinct nautiloids and ammonites. Extant nautiloids occupy a different isotopic niche than all other cephalopod groups where such data have been published to date. We conclude that these species are obligate scavengers rather than predators on any living species in their environments. Extant Nautilus and Allonautilus also demonstrate different patterns of functional allometry of nitrogen isotope values over ontogeny than do most other cephalopods (or animals in general), by showing decreasing nitrogen isotope levels during ontogeny. This pattern is shown to be different in Sepia and the yet small number of ammonite cephalopods studied to date, supporting the increasingly accepted view that ammonites were far closer to coleoids in basic biology than nautiloids. Overall, phragmocone-bearing cephalopods appear fundamentally different ecologically than cephalopods without this kind of buoyancy system. Of these groups, nautiloids appear to live a low-energy existence that allows them to subsist on energy-poor food sources, such as crustacean molts, as well as being able to scavenge in low oxygen basins where rare food falls, such as dead fish, remain unobtainable by most other animals.

A labeled data set of underwater images of fish and crab species from five mesohabitats in Puget Sound WA USA

The sustainable management of fisheries and aquaculture requires an understanding of how these activities interact with natural fish populations. GoPro cameras were used to collect an underwater video data set on and around shellfish aquaculture farms in an estuary in the NE Pacific from June to August 2017 and June to August 2018 to better understand habitat use by the local fish and crab communities. Images extracted from these videos were labeled to produce a data set that is suitable for use in training computer vision models. The labeled data set contains 77,739 images sampled from the collected video; 67,990 objects (fishes and crustaceans) have been annotated in 30,384 images (the remainder have been annotated as “empty”). The metadata of the data set also indicates whether a physical magenta filter was used during video collection to counteract reduced visibility. These data have the potential to help researchers address system-level and in-depth regional shellfish aquaculture questions related to ecosystem services and shellfish aquaculture interactions.

Baited remote underwater video stations as a potential tool for assessing coastal rocky fishes in Chile

AbstractCoastal rocky fish species support important fishing activities, but basic information is lacking for many before catches decline. Monitoring and management of coastal rocky fish species is urgently needed in Chile, but knowledge of these species is fragmentary at best. Performance of Baited Remote Underwater Video Stations (BRUVS) for assessing rocky fish assemblages was evaluated in south‐central Chile. Seven medium‐ to large‐sized exploited species dominated fish assemblages in the survey area, including five small cryptic rocky reef fishes, one agnathan and a catshark species. These seven species represented 78% of the species targeted by commercial fishing in the survey area. Furthermore, this tool provided new information on behaviour of rocky fish species. The simple, inexpensive and light nature of single‐camera BRUVS may be crucial for maintaining monitoring programs along remote areas of Chile.

Biodiversity study of the deep-sea ecosystems in the northwestern part of the Pacific Ocean

The aim of the work was to study some deep-sea bottom communities of the Far Eastern seas of Russia using a remotely operated underwater vehicle.Materials were the data of underwater video and photo profiling, as well as direct sampling, performed in 2011–2013, 2016, 2018, 2020 and 2021.As results, an extensive array of new data on the composition, structure, and patterns of distribution of deep sea biota has been obtained. A primary description of the benthic communities of the Gamovsky Canyon (Sea of Japan), cold seeps of the Deryugin Basin (Sea of Okhotsk), and Piip underwater volcano (Bering Sea) has been prepared. Some features of the composition and structure of communities are revealed, and vertical zonality is described.Practical value: the results can be used in the development of environmental protection measures and measures of rational nature management in the waters of the Far Eastern seas of Russia and in areas of potential development of deep-sea mineral resources in the ocean.

Automated riverbed composition analysis using deep learning on underwater images

Abstract. The sediment of alluvial riverbeds plays a significant role in river systems both in engineering and natural processes. However, the sediment composition can show high spatial and temporal heterogeneity, even on river-reach scale, making it difficult to representatively sample and assess. Conventional sampling methods are inadequate and time-consuming for effectively capturing the variability of bed surface texture in these situations. In this study, we overcome this issue by adopting an image-based deep-learning (DL) algorithm. The algorithm was trained to recognise the main sediment classes in videos that were taken along cross sections underwater in the Danube. A total of 27 riverbed samples were collected and analysed for validation. The introduced DL-based method is fast, i.e. the videos of 300–400 m long sections can be analysed within minutes with continuous spatial sampling distribution (i.e. the whole riverbed along the path is mapped with images in ca. 0.3–1 m2 overlapping windows). The quality of the trained algorithm was evaluated (i) mathematically by dividing the annotated images into test and validation sets and also via (ii) intercomparison with other direct (sieving of physical samples) and indirect sampling methods (wavelet-based image processing of the riverbed images), focusing on the percentages of the detected sediment fractions. For the final evaluation, the sieving analysis of the collected physical samples were considered the ground truth. After correcting for samples affected by bed armouring, comparison of the DL approach with 14 physical samples yielded a mean classification error of 4.5 %. In addition, based upon the visual evaluation of the footage, the spatial trend in the fraction changes was also well captured along the cross sections. Suggestions for performing proper field measurements are also given; furthermore, possibilities for combining the algorithm with other techniques are highlighted, briefly showcasing the multi-purpose nature of underwater videos for hydromorphological assessment.

Multiple lines of evidence highlight the dire straits of yellowfin tuna in the Indian Ocean.

Yellowfin tuna (Thunnus albacares) are highly valued pelagic fisheries target species. Regional fisheries management organizations (RFMOs) are the principal mechanism that manage yellowfin tuna fisheries. Determining changes in population abundances is crucial for effective conservation and management. We use multiple methods for monitoring biomass trends and evaluating the status of yellowfin tuna in each ocean basin and show how additional, multiple lines of evidence can enhance our understanding of the conservation and exploitation status of this species. Our analysis of regional biomass trajectories and Catch-MSY++ assessments corroborate the findings of the most recent RFMO stock assessments suggesting yellowfin tuna in the Indian Ocean are in critical condition, while the Eastern Pacific yellowfin tuna population shows the lowest levels of exploitation. These results are supported by fisheries-independent data from baited remote underwater video systems (BRUVS), showing that the Indian Ocean yellowfin tuna population is the least common, least abundant, and smallest across all oceans. Our findings support previous claims of systematic and widespread overfishing of yellowfin tuna in the Indian Ocean and thus confirm calls to reduce current fishing levels to ensure the long-term viability of the species.

Coral reefs in the northeastern Saudi Arabian Red Sea are resilient to mass coral mortality events

We conducted an integrated survey combining visual census and baited remote underwater video survey on the coral reefs in the northeastern Red Sea and examined their health by comparing the baseline information from two decades ago. The mean coverage of the corals of all stations was 36 %, including 32 % stony corals and 4.0 % soft corals, significantly higher and lower to previous baseline. Observed high proportion of dead corals indicated the occurrence of the events of mass mortality, and the heating events were the most likely cause. Similar levels of coral coverage compared to two decades ago indicated their resilience to past events with mass coral mortality. Small proportions of macroalgae and sea urchins indicated that they might be controlled by their predators frequently observed in both visual census and underwater video survey. Regular monitoring and careful development plans are needed to safeguard these invaluable reefs.

Subaqueous silt ripples measured by an echo sounder: Implications for bed roughness, bed shear stress and erosion threshold

Bedforms like ripples are widely distributed in the coastal zone. They influence the bed roughness thus the estimation of bed shear stress and associated sediment transport. An echo sounder was mounted on a bottom-supported tripod intended to measure the erosion and deposition of seabed in the subaqueous Yellow River Delta, China. However, variations in bed elevation are found to be not the net erosion or deposition at the observation site, but the migration of silt ripples which were generated by waves and pushed back and forth or flattened off by the tidal currents. Ripple heights were observed to be within 0.1–0.7 cm and were used for testing the model of Nielsen (1981). The model overestimated the height of silt ripples as it was developed for sands, but the deviation can be well addressed by incorporating a linear modification (R2 = 0.79). Alternatively, a new model specifically for silt ripple height was regressed from the field data with R2 up to 0.78. The existence of silt ripples increases the bed shear stress by 4 times due to the additional bed roughness. A “fluffy layer” overlies the consolidated seabed, therefore, net seabed erosion occurs after the “fluffy layer” is resuspended. A representative critical bed shear stress for net seabed erosion in the study area was found to be 0.8 Pa. The echo sounder can be an alternative tool for observing silt ripples in coastal regions like the Yellow River Delta where the water is too turbid for underwater videos. The proposed model infers silt-ripple features from bed grain size and flow condition and provides a quick estimate for bed roughness improving the understanding on sediment transport.