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Similarities in the behavior of diverse animal species that form large groups have motivated attempts to establish general principles governing animal group behavior. It has been difficult, however, to make quantitative measurements of the temporal and spatial behavior of extensive animal groups in the wild, such as bird flocks, fish shoals, and locust swarms. By quantifying the formation processes of vast oceanic fish shoals during spawning, we show that (i) a rapid transition from disordered to highly synchronized behavior occurs as population density reaches a critical value; (ii) organized group migration occurs after this transition; and (iii) small sets of leaders significantly influence the actions of much larger groups. Each of these findings confirms general theoretical predictions believed to apply in nature irrespective of animal species.

Diadromous fish use both freshwater and marine habitats to complete their life cycles, but dams restrict those connections, and as a result, many populations are historically low across their range. The Penobscot River, Maine, USA, once had large populations of diadromous fish and has recently been the focus of large restoration projects. Our objective was to assess the river restoration impacts in the estuary using mobile, multi-frequency echosounders (SIMRAD EK60 split-beam 38 and 120 kHz) to construct a time series of fish distribution using metrics of fish length and fish density, both seasonally and pre-restoration (2012–2014) versus post-restoration (2015–2019). Seasonally, fish size was the smallest in summer, while density and biomass were greater as compared to spring and fall. Between pre- and post-restoration years, fish length did not differ, and with a median of 4.7 cm, median density increased from less than 0.5 fish m−2 to greater than 1 fish m−2. Fish biomass was approximately three times greater in post-restoration years where it ranged 23 to 316 mt per survey than pre-restoration years where it ranged from 9 to 114 mt per survey. These patterns are consistent with a system undergoing restoration of migratory fish where larger adult fish migrate in the spring and their juveniles in the summer and fall. This study demonstrates the ecological impacts of river restoration on its estuary by quantifying multiple metrics (fish biomass, density, and size).

Monitoring changes of land cover near water bodies and water bodies themselves represents a part of environment protection and management. The management can be done at the global or local level. The local level requires more detailed data, which can be collected i.e. by means of aircraft or UAV. The paper describes a case study focused on the utilization of UAV-based RGB data to monitor land cover near the pond Baroch, which is located in the Czech Republic, near the city of Pardubice. The area is specific – it is a small pond accompanied by several smaller pools and connecting canals and surrounded by meadows (often watered), reeds, bushes and some trees Used data were collected by authors by in advance planned flights in August, September, October, November, and December 2021. Support Vector Machine, Maximum Likelihood, Random Trees, and Deep Learning are used as methods to process data and detect land cover changes. Manually interpreted data are used as reference data. Because of the nature of the data (only R, G, and B bands), classification into bare land, the water, vegetation, dry vegetation, and wet vegetation classes only was used. Very high heterogeneity of the observed area, availability of RGB bands only, and very high spatial resolution (1,9 cm per pixel) led to isolated cells.

Mesopelagic fishes are an important component of the world’s oceans in terms of their abundance, biomass, and ecosystem function. These fishes are important contributors to the biological carbon pump via their feeding and behaviors, whereby they facilitate the transfer of carbon from shallow waters to the deep sea. Several species undertake diel vertical migration, feeding in shallower waters at night and moving to deeper waters during the day. This process actively expedites the downward flux of carbon. However, carbon budgets and climate models require accurate information regarding the depth distributions and migration patterns of these fishes, and environmental DNA (eDNA) analyses can provide this information. Here, we utilize eDNA approaches, generating taxonomically-informative COI and 12S reference barcodes for 80 species of mesopelagic fishes, which can be used for species-level identification of eDNA sequences. Using these, along with a publicly available barcodes database, we compare results from eDNA analysis with traditional net sampling, and explore the ability of eDNA techniques to detect diel vertical migration in fishes from samples collected in Northwest Atlantic Slope Water. We found that eDNA and net samples often resulted in different species identifications, demonstrating that eDNA can detect species that would otherwise be missed with traditional methods. In our eDNA samples, we also detected more species (12) in our shallowest depth category (0 - 100 m) from night samples than from day samples (3). This is consistent with increased diversity in shallow waters at night due to diel vertical migration. Based on the variability observed in sample duplicates, we suggest that future mesopelagic eDNA studies incorporate larger sample volumes and scaled-up sampling efforts. We also note the potential applications of eDNA analysis in addressing ecological questions related to predator-prey relationships identification of foraging hotspots, and carbon flow through the ocean’s midwaters.

ObjectiveOffshore wind development is expected to expand rapidly along the East Coast of the United States within the next 10 years and will impact the biology and ecology of the flora and fauna as well as human activities, such as commercial and recreational fishing. The Block Island Wind Farm is a five-turbine, 30-MW wind array located about 6 km off the coast of Rhode Island and has been in operation since 2016.MethodsWe conducted a 4-day acoustical and biological survey of the area during daylight hours to gain insight on the spatial distribution of fish species in and around the turbines. We utilized a hull-mounted, downward-looking Simrad 38-/200-kHz ES70 and a pole-mounted iXblue SeapiX steerable Mills Cross, 150-kHz, 1.6° resolution multibeam echosounder oriented downward to map the two- and three-dimensional distributions using spiral and straight-line transect patterns. We collected fish by using hook and line to verify the sources of acoustic backscatter and to measure length, sex, and diet.ResultBlack Sea Bass Centropristis striata were the most commonly caught species and appeared to be the primary constituents of the fish aggregations that were mapped by the acoustic systems. We found increased levels of acoustic backscatter within 200 m of the turbine structures, suggesting that they were attractive structures.ConclusionThese levels were not greater than backscatter levels in the surrounding area, suggesting that the proximate effect of the wind array was spatially limited.

Vocalizations were recorded for over eight distinct whale species as they converged on a shoal of herring to feed; the predators divided the shoal into overlapping but species-specific foraging sectors and the activities of the whales changed between day and night. Marine predators at prey Using a combination of passive and active ocean acoustic waveguide remote sensing in an important northwestern Atlantic marine mammal autumn foraging ground, Purnima Ratilal and colleagues have mapped the movement and distribution of more than ten marine mammal species simultaneously with that of their fish prey. The vocalizations of humpback, blue, fin, minke and other marine mammal species were recorded across an area of roughly 100,000 square kilometres as they converged onto dense herring shoals, dividing them into overlapping but species-specific foraging sectors, which were maintained for more than two weeks. This snapshot of marine life reveals how predators moved through the huge shoal, indicating how the activities of the predators varied as day moved into night. The results will increase understanding of marine-mammal behaviour and inform conservation efforts. Observing marine mammal (MM) populations continuously in time and space over the immense ocean areas they inhabit is challenging but essential for gathering an unambiguous record of their distribution, as well as understanding their behaviour and interaction with prey species 1 , 2 , 3 , 4 , 5 , 6 . Here we use passive ocean acoustic waveguide remote sensing (POAWRS) 7 , 8 in an important North Atlantic feeding ground 9 , 10 to instantaneously detect, localize and classify MM vocalizations from diverse species over an approximately 100,000 km 2 region. More than eight species of vocal MMs are found to spatially converge on fish spawning areas containing massive densely populated herring shoals at night-time 11 , 12 , 13 , 14 , 15 , 16 and diffuse herring distributions during daytime. We find the vocal MMs divide the enormous fish prey field into species-specific foraging areas with varying degrees of spatial overlap, maintained for at least two weeks of the herring spawning period. The recorded vocalization rates are diel (24 h)-dependent for all MM species, with some significantly more vocal at night and others more vocal during the day. The four key baleen whale species of the region: fin, humpback, blue and minke have vocalization rate trends that are highly correlated to trends in fish shoaling density and to each other over the diel cycle. These results reveal the temporospatial dynamics of combined multi-species MM foraging activities in the vicinity of an extensive fish prey field that forms a massive ecological hotspot, and would be unattainable with conventional methodologies. Understanding MM behaviour and distributions is essential for management of marine ecosystems and for accessing anthropogenic impacts on these protected marine species 1 , 2 , 3 , 4 , 5 , 17 , 18 .

Acoustic surveys have been conducted on Georges Bank from 1998 to present to estimate Atlantic herring (Clupea harengus) population abundance. Acoustic data were collected with a 12 or 18, 38, and 120 kHz Simrad EK500 scientific echo sounder. A pelagic trawl and underwater video images were used to collect biological information and to verify the species composition of acoustic backscatter. A multifrequency classification method was developed to improve the efficiency and accuracy of classifying species from acoustic echograms. In this method, a volume backscatter (S v ) threshold was applied equivalently to all echograms, and then a composite echogram was created based on which frequencies had S v greater than or less than the S v threshold. The results of this method were compared with the standard method of visually scrutinizing regions, and metrics were developed to evaluate the accuracy of classification algorithms relative to current methods, as well as to assess the effects of classification methods on population abundance estimates. In general, this method matched visually scrutinized Atlantic herring regions, but with consistent biases in classifying 38 kHz backscatter. The metrics highlighted spatial and temporal changes in the acoustic landscape, which may be indicative of intra- and inter-annual biological changes.

Fish diversity and ecology in the ocean’s mesopelagic zone are understudied compared to other marine regions despite growing interest in harvesting these potential resources. Otoliths can provide a wealth of taxonomic and life history information about fish, which can help fill these knowledge gaps; however, there has been relatively little research to date on the otoliths of mesopelagic species. Here, a species-specific image library was assembled of sagittal otoliths from 70 mesopelagic fishes belonging to 29 families collected in the western North Atlantic Ocean. Images of adult sagittal otoliths from 12 species were documented and photographed for the first time. The fish were identified to species with a combination of morphological characters and DNA barcoding. Regressions between otolith size and fish length are presented for the six species with the largest sample sizes in this study. This otolith image library, coupled with otolith-length and width to fish-length relationships, can be used for prey identification and back-calculation of fish size, making it a valuable tool for studies relating to food webs in the important yet poorly understood mesopelagic zone. In addition, the 44 fish barcodes generated in this study highlight the benefit of using an integrative taxonomic approach to studies of this nature, as well as add to existing public databases that enable cryptic species and metabarcoding analyses of mesopelagic species.

The migration of extensive social groups towards specific spawning grounds in vast and diverse ocean environments is an integral part of the regular spawning process of many oceanic fish species. Oceanic fish in such migrations typically seek locations with environmental parameters that maximize the probability of successful spawning and egg/larval survival. The 3D spatio-temporal dynamics of these behavioral processes are largely unknown due to technical difficulties in sensing the ocean environment over wide areas. Here, we use ocean acoustic waveguide remote sensing (OAWRS) to instantaneously image immense herring groups over continental-shelf-scale areas at the Georges Bank spawning ground. Via multi-spectral OAWRS measurements, we capture a shift in swimbladder resonance peak correlated with the herring groups’ up-slope spawning migration, enabling 3D spatial behavioral dynamics to be instantaneously inferred over thousands of square kilometers. We show that herring groups maintain near-bottom vertical distributions with negative buoyancy throughout the migration. We find a spatial correlation greater than 0.9 between the average herring group depth and corresponding seafloor depth for migratory paths along the bathymetric gradient. This is consistent with herring groups maintaining near-seafloor paths to both search for optimal spawning conditions and reduce the risk of predator attacks during the migration to shallower waters where near-surface predators are more dangerous. This analysis shows that multi-spectral resonance sensing with OAWRS can be used as an effective tool to instantaneously image and continuously monitor the behavioral dynamics of swimbladder-bearing fish group behavior in three spatial dimensions over continental-shelf scales.

Atlantic herring (Clupeaharengus ) in the Georges Bank, Gulf of Maine, and southern New England regions were sampled from early September into mid-November by the Northeast Fisheries Science Center during their annual randomly-stratified bottom trawl and systematic acoustic/midwater trawl surveys. Atlantic herring were randomly selected for length distributions and systematically subsampled for biological metrics (e.g., weight, age, maturity, and sex). Broad similarities in Atlantic herring biological metrics between midwater and bottom trawl catches suggest both gear types provide comparable sampling of herring demographics in the Gulf of Maine and Georges Bank regions during autumn. Annual mean lengths and weights and temporal patterns of herring size were consistently similar between gear types. Similarity in age structure between Georges Bank and the Gulf of Maine suggest a similar response to intrinsic and extrinsic factors between herring stocks in these regions, but apparent asynchrony in spawning timing suggests some level of independence between these stocks. Overall similarities can mask interesting distinctions such as midwater trawls seem to sample younger, smaller, but heavier fish than do bottom trawls. Sampling of historical spawning sites appears to characterize the biological state of Atlantic herring in the Georges Bank region and could be utilized to design an efficient sampling scheme for Atlantic herring in the Gulf of Maine.