Sandy Bottom Research Articles

New Material of Thylacocephala from the Early Ladinian (Middle Triassic) of Northern Grigna (Lecco, Lombardy, Northern Italy)

Here we report and describe a new assemblage of Thylacocephala (Crustacea) from the Early Ladinian Buchenstein Fm. (Middle Triassic) of Grigna, Northern Italy. The assemblage consists of at least four species from three different genera: Ankitokazocaris lariensis sp. n., Ankitokazocaris sp., Austriocaris sp., Stoppanicaris grignaensis gen. et sp. n. This thylacocephalan assemblage is rather diverse compared to the others of the Triassic. The largest size and ornamentation type of thylacocephalan species is compared among different periods of the Triassic and indicates that taxa with ridges on the carapace are generally smaller than those with smooth carapaces. This may be related to their different modes of life, such as inside or above the sediment with low oxygen levels. Large and smooth taxa were possibly more adapted to a life above sandy bottoms in shallow waters, under a somewhat high wave energy, while small, ornamented taxa are better suited for deeper environments with muddy bottoms, inside which they could move freely. The EDS analysis of Austriocaris sp. reveals that the cuticle mainly consists of apatite, which is in accordance with previous interpretations.

Sandy bottoms have limited species richness but substantially contribute to the regional coastal fish β-diversity: A case study of the Central Mediterranean Sea

Global marine biodiversity loss impairs entire ecosystems and their stability. Robust biodiversity estimates are key to inform policies and management strategies, and need to consider the contribution of diverse habitats, including those for which estimates of biodiversity are scattered or totally absent. This study assessed the fish diversity associated with three main coastal habitats (rocky bottoms, Posidonia oceanica meadows, sandy bottoms), and their role in shaping the overall coastal fish diversity, also in relation to potential environmental and anthropogenic drivers affecting patterns of fish diversity in coastal areas. Using underwater visual census, we sampled 62 sites distributed on the three habitats, for a total of 496 replicates. We assessed the contribution of each habitat to β-diversity, divided into Local Contribution to β-diversity (LCBD), a comparative indicator of the contributions to β-diversity of each habitat, and Species Contribution to β-diversity (SCBD), which measures the relative importance of each species in affecting β-diversity. Finally, we modelled species diversity in relation to potential environmental and anthropogenic drivers. Overall, 72 species were recorded, with the highest species richness observed on rocky bottoms (56 species, 16 unique to this habitat), followed by P. oceanica (38 species, 0 unique) and sandy bottoms (32 species, 14 unique). Sandy bottom assemblages had a significantly higher contribution to LCBD than P. oceanica meadows and rocky bottoms, and two of the five species with the highest contribution to SCBD are exclusively associated with sandy bottoms. Finally, sea surface temperature, sea surface salinity, and habitat were highlighted as significant predictors of species richness. Our findings, aside from highlighting the environmental drivers of coastal fish diversity in the Mediterranean Sea, unravel the potential key role of sandy bottoms in contributing to overall coastal fish diversity and can inform conservation planning.

Diversity, composition and potential roles of sedimentary microbial communities in different coastal substrates around subtropical Okinawa Island, Japan

BackgroundMarine benthic prokaryotic communities play crucial roles in material recycling within coastal environments, including coral reefs. Coastal sedimentary microbiomes are particularly important as potential reservoirs of symbiotic, beneficial, and pathogenic bacteria in coral reef environments, and therefore presumably play a core role in local ecosystem functioning. However, there is a lack of studies comparing different environments with multiple sites on the island scale, particularly studies focusing on prokaryotic communities, as previous investigations have focused mainly on a single site or on specific environmental conditions. In our study, we collected coastal sediments from seven sites around Okinawa Island, Japan, including three different benthic types; sandy bottoms, seagrass meadows, and hard substratum with living scleractinian corals. We then used metabarcoding to identify prokaryotic compositions and estimate enzymes encoded by genes to infer their functions.ResultsThe results showed that the three substrata had significantly different prokaryotic compositions. Seagrass meadow sites exhibited significantly higher prokaryotic alpha-diversity compared to sandy bottom sites. ANCOM analysis revealed that multiple bacterial orders were differentially abundant within each substratum. At coral reef sites, putative disease- and thermal stress-related opportunistic bacteria such as Rhodobacterales, Verrucomicrobiales, and Cytophagales were comparatively abundant, while seagrass meadow sites abundantly harbored Desulfobacterales, Steroidobacterales and Chromatiales, which are common bacterial orders in seagrass meadows. According to our gene-coded enzyme analyses the numbers of differentially abundant enzymes were highest in coral reef sites. Notably, superoxide dismutase, an important enzyme for anti-oxidative stress in coral tissue, was abundant at coral sites. Our results provide a list of prokaryotes to look into in each substrate, and further emphasize the importance of considering the microbiome, especially when focusing on environmental conservation.ConclusionOur findings prove that prokaryotic metabarcoding is capable of capturing compositional differences and the diversity of microbial communities in three different environments. Furthermore, several taxa were suggested to be differentially more abundant in specific environments, and gene-coded enzymic compositions also showed possible differences in ecological functions. Further study, in combination with field observations and temporal sampling, is key to achieving a better understanding of the interactions between the local microbiome and the surrounding benthic community.

Firts records of Bursatella leachii de Blainville 1817 (Mollusca; Gastropoda; Aplysiidae) in Black Sea

ABSTRACT This study reports, for the first time, the discovery of the ragged sea hare Bursatella leachii de Blainville 1817 in the Black Sea. The observations were made during the month of September 2023 at depths varying between 1,0 and 4,0 meters by scuba and snorkeling. A total of 484 specimens of this species were found. Of these, a part were observed in the sandy-muddy bottom of Kumbaba beach and a part in the sandy bottom of Uzunkum beach, in the Sile district (Istanbul province). The estimate of the density of individuals per square meter of seabed made it possible to highlight how the high number of individuals was present on the Kumbaba beach near the mouth of the Türknil river. It could be hypothesized that the introduction of this species into Black Sea could have occurred through natural means. This may have been possible for two reasons; the first is that the beaches of Sile are a few kilometers from the Bosphorus Canal while the other reason lies in the fact that the report of B. leachii closest to the town of Sile dates back to January 2020, when the species was observed in the seabed of the coast southern Dardanelles (Çanakkale Strait). To be certain of what has been stated, monitoring should be carried out on a regular basis but, at this moment, this hypothesis appears to be the most real. Keywords: Bursatella leachii, Black Sea, Turkey, AIS, NIS

Octopus diet during the settlement period using DNA metabarcoding

The settlement phase is a challenging period for meropelagic octopus, as they adapt to their new life in the sea bottom after a planktonic period. Their ecology and trophic interactions with the surrounding fauna in the wild are practically unknown. To understand their predatory role in the littoral zone, the diet of recently settled Octopus vulgaris from a Mediterranean sandy bottom was studied through molecular methods. Amphipods were present in all the analysed stomach contents, with a total of 20 amphipod taxa recorded as prey. Jassa slatteryi and Microprotopus maculatus were the most commonly found amphipod species. Hydrozoans, decapod crustaceans, cephalopods and bivalves followed amphipods in importance. Niche breadth index assigned to small recently settled octopus the role of a specialised predator, increasing the diversity of prey as they grow. Larger juveniles displayed a higher number of prey taxa suggesting a decreasing predatory specialisation with octopus size and an ontogenetic shift in trophic ecology from diet mainly based on amphipods to a richer diet. The considerable arm elongation and the strong muscular arm crown development after settlement probably allow the juvenile benthic octopus to develop ambush predation and speculative hunting, increasing the range of potential benthic prey species along its adaptation to the benthos.Graphic abstract

Late Cretaceous marine flooding and installation of a mangrove swamp environment in the Prebetic (Betic External Zones, SE Spain)

AbstractThe Cenomanian (Upper Cretaceous) sedimentary rocks of the External Prebetic (Betic Cordillera) in the Sierra de Montearagón-Carcelén (SE Spain) record the transgression and flooding of continental deposits and the subsequent development of an inner shallow carbonate platform. The transgressive surface is densely colonized by infaunal trace-makers of the Glossifungites ichnofacies (Gastrochaenolites and Glossifungites), which indicate sediment starvation and erosion as well as colonization of a firmground. The first deposits were a thick calcarenite bar (2 to 11 m) with large-scale cross-bedding pointing to a high-energy environment in a shallow carbonate platform. The record of the Rosselia ichnofacies (Rosselia and Ophiomorpha) confirms a loose sandy bottom under high-energy conditions. The overlaying stratigraphic succession is characterized by subtidal laminated marly limestones and intertidal limestones with rhizoliths interpreted as a mangrove swamp environment. These facies are organized in shallowing-upwards sedimentary sequences. An episodic high-energy event is represented by bivalve-rich limestones representing shell lags of disarticulated valves. This facies could be related to a climatic perturbation evidenced by a negative excursion of δ13C and δ18O. The successive shallowing-upwards sedimentary sequences persisted thanks to subsidence related to the tectonically controlled depocenters located in the south of the Sierra de Montearagón-Carcelén. The differential subsidence, evidenced by the increasing thickness towards the south of the sector under study, suggests the activity of listric faults that controlled the depocenters. This is the first report of the Cenomanian transgression in this sector of the External Prebetic and the first record of the very extensive mangrove swamp that developed close to the land that emerged.

Preliminary Conceptual Model of Hydrogeological System in The Pandanduri Dam and its Surrounding Area on the Lombok Island

Abstract the availability of water resources is increasingly limited and even tends to be increasingly scarce; an in-depth study of geological-hydrogeological analysis of springs and groundwater is needed to support various community activities. This research was conducted to determine the hydrogeological system in the Pandanduri Dam area and its surroundings. Geological conditions and geomorphology determine the hydrogeological system and groundwater flow direction patterns. Geological conditions were obtained by conducting field investigations, and groundwater level data was obtained by measuring dug wells from 36 points and measuring 13 points of spring locations. Volcanic sedimentary rocks and volcanic breccia dominate the study area. Three (3) rock units can be distinguished, namely (1) the Andesite tuff breccia – pumice unit is located in the southern part of the study area, precisely in the reservoir area, and (2) the Andesite tuff breccia unit dominates located in the southern part of the study area. The study area’s eastern, western, and northern parts and (3) alluvial deposit units located in the study area covered the andesite volcanic breccia. The aquifer consists of volcanic sedimentary rock and volcanic breccia with a sandy bottom. The 2D interpretation of the dam area shows that the sandy volcanic breccia unit has a resistivity value between 5 ohms - 25 ohms in the form of lapilli tuff sand interspersed with fine tuff, located at a depth of 8 meters below the surface. The pattern of the direction of groundwater flow indicates that the movement of groundwater follows the shape of the topography that flows from the hilly area west-northwest of Santong Village to the southeastern river valley of Pandanduri Village; geological and geomorphological conditions affect this groundwater flow pattern.

On the presence of an unexpected meadow of Penicillus capitatus Lamarck (Bryopsidales: Chlorophyta) in Mallorca, Balearic Islands, Western Mediterranean

An unexpected meadow of the warm-water alga Penicillus capitatus was found thriving in sandy bottoms between 16 and 21 m depth in Mallorca, Balearic Islands. Plant densities and benthic coverage were very high when compared to most Mediterranean meadows of this species. As it is common in tropical meadows of this species, all the individuals were found in a Penicillus morphological state, whereas most Mediterranean individuals are always found in the filamentous (Espera) state. Due to the high biomass of the populations, the contribution to the primary productivity of the sandy bottoms it colonizes should be far from negligible. If the expansion of these species continues, the annual calcium carbonate production of the Balearic continental shelf will increase and previous estimated budgets will have to be reconsidered. Since no genetic analysis of the specimens have been performed so far, it is still early to know if the studied populations have been originated by native Mediterranean specimens or from a cryptic lineage of Western Atlantic or Macaronesian origin. Whatever the answer is, the current bloom of this population in an environment completely devoid of this species in the recent past, provides new evidence of the current tropicalization of the Mediterranean caused by global warming.

Discovering the ecological structure of different macrophyte groups in rivers using non-parametric and parametric multivariate ordination techniques

This paper analyses various methods of ecological ordering that are often used in modelling the relationship between vegetation and habitat. The results of direct gradient ordination by Canonical correspondence analysis (CCA), which is based on correlation, were compared with Non-metric multidimensional scaling (NMDS), which is based on rank analyses. Both tools were also compared with Detrended correspondence analysis (DCA), which is a popular indirect gradient analysis method. The macrophyte assessment was conducted at 98 river locations in the lowland regions of Poland. Each of the surveyed locations falls within a consistent abiotic category: small to medium-sized lowland rivers with a sandy bottom. Habitat elements analysed included limnological variables and geographic parameters, and the botanical survey focused on submerged macrophytes, including vascular plants, as well as bryophytes and algae. Firstly, it was shown that various analytical tools for determining the importance of ecological factors (Monte Carlo test, BIOENV) identify slightly different significant factors responsible for the development of macrophytes in rivers. Secondly, considerable similarity was found in the structure of macrophyte communities generated on NMDS and DCA biplots, while macrophyte communities were presented very differently based on CCA. Thirdly, the ecological preferences of aquatic plants based on one-dimensional analyses primarily reflected the results of CCA, whereas they did not always follow the ecological pattern revealed by NMDS. Finally, by conducting separate studies for non-vascular plants and vascular macrophytes, it was confirmed that different ecological drivers are responsible for the development of particular groups of macrophytes

Some like it hot: Is the recent presence of the meadow-forming Penicillus capitatus in the Azores connected to global warming?

Specimens found in a tide pool on Santa Maria Island (Azores) were identified in situ as the green alga Penicillus capitatus (Halimedaceae, Bryopsidales). DNA-based analyses of two genetic markers (rbcL and tufA) confirmed the identification and indicated that the Azorean population is closely related to those from the Western Atlantic. P. capitatus is newly reported for the Azores, with the nearest population in the Madeiran archipelago since 1978. The present record expands the species distribution further north outside the Mediterranean basin. Simulation of particle dispersal indicates that the species could reach the Azores within a year from any place in the North Atlantic where it is known to occur. Therefore, P. capitatus most likely arrived by rafting through marine currents, though anthropogenic introduction has not been excluded. While its natural arrival in the Azores may have occurred multiple times, its current successful establishment is likely related to the recent warmer conditions of the Azorean waters, estimated to have increased by 1.05º C over the last four decades. Prospection on sandy bottoms should be performed to assess the distribution of the species in the archipelago. DNA sequence analyses, including representatives of other P. capitatus populations, are necessary to enable further studies at a phylogeographical level.

First records of two species of snake eels, Aplatophis chauliodus and Ophichthus hyposagmatus (Actinopterygii: Anguilliformes: Ophichthidae), from Mexico

We report herewith the presence of two species of rare snake eels, Aplatophis chauliodus Böhlke, 1956 (499 mm in total length [TL]) and Ophichthus hyposagmatus McCosker et Böhlke, 1984 (486 mm TL), in Mexican waters of the Gulf of Mexico. Both species were caught using bottom longline at a depth of 50 to 100 m in sandy bottoms in Veracruz, Mexico. Both records are the first for Mexico and the westernmost in the Gulf of Mexico.

Dislodgement and mortality challenges when restoring shallow mussel beds (Mytilus edulis) in a Danish estuary

In recent decades, mussel beds in the northern Atlantic and Scandinavia have declined rapidly in extent due to anthropogenic impacts, similar to many other marine habitats. In this study, a large‐scale restoration experiment was conducted to identify major challenges that arise during restoration efforts on shallow subtidal mussel beds. Suspension‐grown mussels (Mytilus edulis) were relayed in two different treatments either directly on bare bottom sandy sediments, or on coir nets (Net), used as a proxy for suitable byssal attachment substrate. The treatments were monitored for 1.5 years and coverage (%), biomass (WW), and population dynamics were quantified. Two main challenges of shallow bed restoration were identified: (1) Lack of suitable attachment substrate resulting in dislodgment of individuals during storm events. The Net treatment had significantly higher coverage and biomass of Mytilus at the end of the monitoring period, clearly demonstrating the importance of suitable substrate at physically exposed locations. (2) High mortality of juvenile mussels. Population dynamics revealed a high mortality of juvenile Mytilus, which resulted in almost complete loss of relayed Mytilus individuals less than 30 mm within the first season. This was most likely due to high meso‐predator densities, as a result of declining top‐predator populations. The high mortality of juvenile Mytilus prevented successful annual recruitment, thereby making the population unsustainable long‐term. Both challenges need to be addressed to create stable beds during restoration. Additionally, the experiment demonstrated the viability of using suspension‐grown Mytilus as a seed‐source when restoring mussel beds.

Low-cost methodology to study the settlement of solid blocks on sandy bottoms

A low-cost methodology is proposed to provide settlement data for solid blocks in order to improve the design of future coastal structures. Two methods were used to determine how far the block was sinking at the sandy bottom: topographically (four field campaigns) and continuously (with two pressure sensors) for 7.5 months. Settlement values obtained were similar in both cases. The difference between both methods at most 2 cm. Half of the sink occurred in the first week. Over the next month, the rate of sinking slowed down until a storm ended it all. Subsequently, the blocks remained stable. A comparison with other researchers’ data was performed and significant differences were found. This heterogeneity in behaviour necessitate the use of these types of low-cost tests that would help calibrate both physical and numerical models.

A new cryptic species of Polybiidae (Crustacea: Decapoda: Portunoidea) from the East Atlantic, with considerations on the genus Polybius

The use of integrative taxonomy has confirmed the existence of a new distinct crab species, cryptic, within the group of the former genus Liocarcinus, now Polybius, closely related to P. holsatus, P. vernalis and P. marmoreus. Previous reports have considered it to be the Atlantic form of P. vernalis, or as a species “affinis” or “comparable to” P. holsatus. Diagnostic morphological characters are presented for identification and the morphological variability in these species, mainly within P. vernalis (the most related) is analysed. Furthermore, based on molecular and other previous data, a new combination (genus change) is proposed. This new species, Polybius dioscurus sp. nov., lives on infralittoral sandy bottoms, coexisting with the other species mentioned, in the temperate and subtropical zone of the North Atlantic Ocean, including the Alboran Sea (westernmost Mediterranean).

Fluxes of nitrogen and phosphorus in fouling communities on artificial offshore structures

The number of offshore artificial structures in the North Sea is continuously increasing. Apart from the structures that have been added to the marine environment accidentally (e.g., shipwrecks), structures are also deliberately developed to meet the increasing needs for renewable energy. These structures provide habitat for fouling organisms. The fouling communities vary in abundance and composition based on location, depth, and structure age. Most fouling species filter particles from the water column, changing phytoplankton production and affecting larval settlement success, while releasing ammonium that can fuel phytoplankton growth as well as (pseudo)faeces that enriches the seabed, changing local biogeochemical cycles.Our study used in-situ incubation chambers to investigate oxygen, nitrogen, and phosphate fluxes associated with fouling organisms to improve understanding of these changes in biogeochemical cycles. Divers used incubation chambers (domes) on shipwrecks in the southern North Sea where over 55 years mature fouling communities have established. A series of water samples was collected from each dome during deployment to measure the change in concentration of ammonium, nitrite, nitrate, and phosphate. All fauna enclosed in the domes was collected after each measurement for further analysis.The full macrofauna dataset contained 65 unique species on 4 shipwrecks (25 to 50 species per sample). Abundance ranged from 2187 to 59,427 individuals per sample (683 cm2). On average, a decrease in oxygen concentration of 126 μmol/g ash free dry weight/h was found. The sequential water samples also showed clear changes in nutrient concentration with time in all incubations. The largest changes were observed with high fouling community abundances and biomass. Ammonium, nitrite, and phosphate always increased, with 1.5-to-5-fold increases from start to end of the incubation, while for nitrate both an efflux and influx were measured. Oxygen decreased in all incubations. Mean fluxes (all in μmol per m2 per hour with standard error) were significant for ammonium (945 ± 300), nitrite (80 ± 30), phosphate (61 ± 8), and oxygen (−11,794 ± 3289), but not for nitrate (−206 ± 122). Per gram AFDW, only ammonium (12.7 ± 3.5) and oxygen (−126 ± 48) had fluxes that differed significantly from zero.Compared to average seabed (sandy bottom) oxygen demand and community fluxes from previous studies, the observed fluxes were high. Our findings resembled those from temperate biogenic reef studies. Further data collection across a larger spatial and temporal scale is needed to fully understand offshore structure effects on marine environments.

Untangling Coastal Diversity: How Habitat Complexity Shapes Demersal and Benthopelagic Assemblages in NW Iberia

Understanding species–habitat relationships is essential for ecosystem-based conservation. This study explores the significance of habitat characteristics and complexity for demersal and benthopelagic communities within a patchwork of coastal habitats, including rocky seabed, macroalgae formations, sandy bottoms, and a combination of rock and sand areas. Species and habitats were surveyed along the north-west (NW) Iberian continental shelf area of Viana do Castelo using baited remote underwater video stations (BRUVS). We found significant differences (p < 0.05) in species assemblages across habitats, with rocky substrates showing the highest diversity and abundance. Sand habitats showed the lowest species richness and abundance, underscoring the importance of habitat complexity to support marine life. Our study also emphasises the role of specific species in shaping the communities, identifying key species such as Trisopterus luscus, Diplodus vulgaris, and Ctenolabrus rupestris as the three most abundant in the region and significant contributors to the observed dissimilarities between habitats. By elucidating the impact of habitat complexity on marine life, our results offer essential baseline data, which serve as a kick-start point to inform sustainable management and conservation strategies for the long-term health and productivity of these vital ecological systems in the North-East Atlantic.

Impacts of Desalination Brine Discharge on Benthic Ecosystems.

Seawater reverse osmosis (SWRO) desalination facilities produce freshwater and, at the same time, discharge hypersaline brine that often includes various chemical additives such as antiscalants and coagulants. This dense brine can sink to the sea bottom and creep over the seabed, reaching up to 5 km from the discharge point. Previous reviews have discussed the effects of SWRO desalination brine on various marine ecosystems, yet little attention has been paid to the impacts on benthic habitats. This review comprehensibly discusses the effects of SWRO brine discharge on marine benthic fauna and flora. We review previous studies that indicated a suite of impacts by SWRO brine on benthic organisms, including bacteria, seagrasses, polychaetes, and corals. The effects within the discharge mixing zones range from impaired activities and morphological deformations to changes in the community composition. Recent modeling work demonstrated that brine could spread over the seabed, beyond the mixing zone, for up to several tens of kilometers and impair nutrient fluxes from the sediment to the water column. We also provide a possible perspective on brine's impact on the biogeochemical process within the mixing zone subsurface. Desalination brine can infiltrate into the sandy bottom around the discharge area due to gravity currents. Accumulation of brine and associated chemical additives, such as polyphosphonate-based antiscalants and ferric-based coagulants in the porewater, may change the redox zones and, hence, impact biogeochemical processes in sediments. With the demand for drinking water escalating worldwide, the volumes of brine discharge are predicted to triple during the current century. Future efforts should focus on the development and operation of viable technologies to minimize the volumes of brine discharged into marine environments, along with a change to environmentally friendly additives. However, the application of these technologies should be partly subsidized by governmental stakeholders to safeguard coastal ecosystems around desalination facilities.

Spawn and development of the olivid gastropod Olivancillaria carcellesi from north Patagonia, Argentina

AbstractOlivancillaria carcellesi occurs in shallow sandy shores from north Patagonia, in intertidal and subtidal sandy bottoms. Females of O. carcellesi exhibited a remarkable specificity for spawning on the shells of living males and females, indiscriminately, of the buccinanopsid Buccinastrum deforme, measuring 26.9 ± 4.7 mm in shell length. The egg capsule was semispherical and attached to B. deforme shells by a small elliptical and wide base. The capsule was translucid when spawned, with a thick and semirigid wall and a hatching aperture of 1.8 ± 0.1 mm (n = 111) in diameter. Each egg capsule contained a single egg that measured 1367 ± 34 μm (n = 5) in diameter before cleavage. The embryo developed a small bilobed velum and an operculum, which were both lost before hatching as a crawling juvenile of 1762 ± 47 μm (n = 28) in shell length. As in other species in the genus, the eggs of O. carcellesi are among the largest in the caenogastropods with direct development. The time from oviposition to hatching is estimated to be approximately 6 months.

ANALISIS KANDUNGAN PROTEIN DAN LEMAK PADA TERIPANG PASIR (Holothuria scabra) YANG DIPEROLEH DARI PERAIRAN DESA SULI DAN APLIKASINYA KEPADA MASYARAKAT MELALUI PENYULUHAN

Background: One kind of animals with spines are sea cucumbers. Sandy waters, rocky or muddy beaches, and coral reefs are common habitats for these species. Clear, clean waters with a fine sandy bottom, away from pounding waves, are ideal for the growth of sand sea cucumbers. Sea cucumbers are found in great number across Maluku. One such location is the waters surrounding Suli village, where sand sea cucumbers, or Holoturia scabra, are particularly common. Methods: Descriptive approaches are used in this study. The laboratory study findings served as the basis for the data sources. Results: In samples of sand sea cucumbers (Holothuria scabra), the protein yield was greater than the fat content. Conclusion: The protein content is 15.3544 and the fat content is 0.1816. This protein level figure is still below the maximum protein threshold of 72.93%.

Spatial distribution of northern shrimp Pandalus eous in the Sea of Japan in relation to the seafloor environment

Abstract To explore relationships between spatial distributions of northern shrimp Pandalus eous and environmental factors along the coastline of Honshu Island in the Sea of Japan, we built delta-type two-step generalized additive models (delta-GAM) based on bottom trawl surveys conducted in 2013–2022. The models provide the first quantitative analysis of the species’ habitat, showing that its distribution is associated with bottom sediment type, depth, slope and topographic position index (TPI) alongside the effects of year and region. From the delta-GAM response plots, species habitat preferences in the Sea of Japan were estimated as follows: seafloor deeper than 283 m; muddy rather than sandy bottoms; gently sloped to flat bottoms (<0.8° in slope); and valleys rather than ridges (TPI < 0.9). These results were reviewed in detail along with previously reported distribution records of northern shrimp. Standardized density (s-density) per fishing grid cell (10′ square latitude–longitude mesh) estimated from the delta-GAM results indicated that this species is widely distributed on the continental slope along the coast of Honshu Island. To test plausibility of the s-density analysis, we compared s-density per fishing grid cell with nominal CPUE (kg per haul) per fishing grid cell based on official logbook data from large offshore trawl fisheries. The two were generally positively correlated by year, and the delta-GAM results were assumed to be fairly robust. Finally, potential fishing grounds were explored based on the delta-GAM results.