Nutrients and Primary Production in the Estuary of the Razdol’naya River (Amur Bay,Sea of Japan)

The behavior of the basic nutrients (NO₃, PO₄, SiO₂) was studied in the estuary of the Razdolnaya River in low and high water, the flow was 4.3 × 10⁶ m³/day and 10.8 × 10⁶ m³/day, respectively. It was shown that within the limits of the euphotic zone the nutrients were characterized by a pronounced nonconservative behavior caused by their removal by phytoplankton in primary production. It was determined that phytoplankton removal of nutrients occurred with ratios C : NO₃ : P : Si = 105 : 18 : 1 : 37 and C : NO₃ : P : Si = 93 : 11 : 1 : 29 at a respective ratio P : NO₃ : Si = 1 : 22 : 140 in low water and P : NO₃ : Si = 1 : 17 : 120 in high water. It was also determined that the maximum rate of nutrient removal was 4 times higher in the high water than in the low water. The maximum value of primary production of phytoplankton was 2.5–4.0 gC/m² day. The estuary area of the Razdolnaya River was specified by rather high production. Such a rate of estuarine primary production, caused by nutrients carried out by the river, being no less than 250 t of dry weight of phytoplankton a day, can provide daily production up to 800 t of biomass in the secondary chain of the ecosystem.Original Russian Text Copyright © 2005 by Biologiya Morya, Zvalinsky, Nedashkovsky, Sagalayev, Tishchenko, Shvetsova.     

Effect of the Razdol’naya River on structure of the free-living nematode community of the Amursky Bay,Sea of Japan

The effect of the Razdol’naya River on the littoral and sublittoral nematode community was studied in the innermost part of the Amursky Bay. Thanks to the seasonal abundance of juveniles of macrobenthic animals, pseudomacrobenthic species prevailed in the meiobenthos littoral community. Juvenile amphipods dominated (39.5%), the percentage of nematodes was 18.4% (45 species). The nematodes dominated in the meiobenthos community (65.7%, 71 species) at the sublittoral zone. The similarity of the species structure of littoral and sublittoral nematodes reached 36.5%. Low population density (2.6±1.7 thousand ind/m²) and poor species diversity of nematodes (7 species), the dominating form being Oncholaimium paraolium, were recorded at the littoral zone, which was subjected to direct riverine influence (1‰salinity). The correlation analysis revealed no relationship between salinity and population density of nematodes at the littoral zone. At the sublittoral zone (at stations of salinity less than 2.85‰) the parameters of population density (73.9±32.3 thousand ind/m²) and species diversity (12 species) of nematodes were the lowest, Parodontophora timmica dominated. A poor expressed dependence between the density of nematode populations and salinity was revealed. The correlation between the average size of ground particles and population density of nematodes was recorded. The greatest similarity of the species structure of littoral and sublittoral nematodes (26.67%) was recorded on gravel-sand bottoms.     

Distribution, abundance, and utilization of wild berries by the gwich’in people in the Mackenzie River Delta region

This paper examines the abundance and Aboriginal use of botanical non-timber forest products in the Gwich’in Settlement Area in the Northwest Territories, Canada. Informants indicated that wild berries are important to Gwich’in diets and an important factor in culture and traditional land use. People collected mostly cloudberries (Rubus chamaemorus), blueberries (Vaccinium uliginosum), and lingonberries (Vaccinium vitisidaea). The total quantities collected were estimated to be greater than other published accounts of berry gathering by northern Aboriginal peoples in North America. The total collected by the 450 households in the year 2000 was about 16,000 L. Inventories of wild berries on the landscape suggest that substantial quantities could be collected for commercial production, although the between-year supply can show considerable variation.     

Summer-autumn ichthyoplankton of the Sea of Okhotsk and the Sea of Japan and special traits of feeding of fish larvae and fry in 2003–2004

In summer-autumn of 2003–2004, the ichthyoplankton of the Sea of Okhotsk comprised 35 species. In this period the most widely distributed and numerous were larvae of the lord Hemilepidotus gilberti, the Pacific stout sand lance Ammodytes hexapterus, and the Sakhalin dab Limanda sakhalinensis. The maximum catches of fish larvae were attributed to coastal waters off eastern Sakhalin and to the shelf of the northern part of the Sea of Okhotsk. In November of 2003, the ichthyoplankton of the Sea of Japan was represented by fish larvae belonging mainly to the boreal ichthyocomplex. The catches consisted predominantly of larvae of the arabesque greenling Pleurogrammus azonus, the ronquil Bathymaster derjugini, and the rockfish Sebastes owstoni. Fish larvae and fry in the northwestern part of the Sea of Japan were caught principally within 43°–45° N and 137°–139° E above the depth 1500–2000 m. The food spectrum of fish larvae in the Sea of Okhotsk and the Sea of Japan comprised over 20 plankters of various size belonging to seven taxa. Irrespective of fish species, the food items common of all fish were copepods Pseudocalanus minutus and Oithona similis. The daily rations were calculated for mass species (Hemilepidotus gilberti, Ammodytes hexapterus, Hexagrammos stelleri, Pleurogrammus azonus, Bathymaster derjugini, and Sebastes owstoni). The larvae of all considered species in the Sea of Japan and in the Sea of Okhotsk fed predominantly in the light period of the day.     

Distribution and abundance of Indo‐Pacific humpback dolphins in Leizhou Bay,China

Abstract

The Indo‐Pacific humpback dolphin (Sousa chinensis) is under severe threat in Chinese waters. Only four small populations of this dolphin are known to survive in the East China Sea and South China Sea. We conducted exploratory surveys from June to September 2005, and found a population of humpback dolphins in Leizhou Bay. Thirty‐eight individuals were identified and catalogued, of which 26 were photographed and re‐identified on more than one occasion, and nine were sighted on five or more occasions each. Our preliminary estimate of the size of the Leizhou population is about 237 individuals, second only to the Pearl River estuary population. We suggest that Leizhou Bay has the potential to serve as a “humpback dolphin sanctuary” in Chinese waters.     

Temporal variability in abundance and biomass of ciliates and copepods in the eutrophicated part of Kaštela Bay (Middle Adriatic Sea)

Seasonal variations in abundance and carbon biomass of ciliated protozoa and micrometazoa were studied from May 1998 to November 1999 in the eutrophicated area of Katela Bay (Middle Adriatic Sea). Ciliates showed peaks in spring and autumn, primarily due to changes in the abundance and biomass of tintinnines, which participated in total ciliate abundance and biomass with 40.48 and 60.02%, respectively. The highest tintinnine density was 4,278 ind. l^–1, while their average biomass varied from 0.611 to 26.557 gC l^–1 . Maximal average density and biomass of non-loricates were 1,430 ind. l^–1 and 3.925 gC l^–1, respectively. The micrometazoa community was dominated by copepod nauplii, especially during the summer and autumn. The copepod biomass ranged between 3.47 and 26.75 gC l^–1 . High abundance and biomass values of the investigated zooplankton groups point to an important role of these organisms in the secondary production in the Bay, indicating that they may be (1) a crucial factor in controlling the populations of nano-/pico-phytoplankton and heterotrophic nanoflagellates, and (2) a significant prey for larger micrometazoans.     

Historical changes and inventory of macroalgae from Königshafen Bay in the northern Wadden Sea

Knowledge on the distribution, abundance and species richness of intertidal macroalgae occurring on sandy and muddy flats of the German Wadden Sea is still incomplete. We summarize published and unpublished information available on the presence of macroalgae on the tidal flats of Königshafen Bay (island of Sylt, North Sea), one of the more extensively studied areas of the Wadden Sea. A total of 46 green algal species, 36 brown algal species and 26 red algal species has been recorded within the last 120 years on soft and hard substrata of Königshafen Bay (disregarding species found unattached or drifting). Several of these species were only temporarily resident on the tidal flats. Today, at least 35 green, 15 brown and 12 red algal species occur within or close to Königshafen Bay. Significant long-term changes in species abundances have occurred in all three major groups of algae: Since the late 1970s, dense green algal mats dominated byEnteromorpha flexuosa, E. radiata andE. prolifera have occurred regularly on the intertidal flats, whereas a general decrease of brown and red algae has been documented. Two red algal species,Gracilaria verrucosa and its epiphyteCallithamnion corymbosum, were conspicuous members of the macroflora until the middle of this century. Although still present in the 1980s, they have now disappeared completely. On the other hand, the brown algaSargassum muticum has begun to colonize mussel beds. The causal background of long-term changes in the macroalgal flora of Königshafen Bay is discussed. Owing to substantial nomenclatural changes during the last 120 years, a revised species list with authors’ names and synonyms is included.     

Seasonal abundance estimates of cetaceans in the southern Black Sea (Sinop), Türkiye

The availability of reliable information on the abundance and distribution of threatened species is fundamental to evaluating their conservation status and taking the necessary measures to implement effective management. The seasonal abundance and distribution of cetaceans in the Sinop region, one of the essential fishing areas of the Black Sea, were estimated with line-transect data. Dedicated boat-based visual observations were conducted in four seasons between May 2019 and March 2020. Average estimates of abundance in the region over all seasons were 1,058 individuals for Black Sea harbor porpoises (Phocoena phocoena relicta; CV = 19.25%, 95% CI[725, 1,542]), 188 individuals for Black Sea bottlenose dolphins (Tursiops truncatus ponticus; CV = 21.67%, 95% CI[123, 289]), and 311 individuals for Black Sea common dolphin (Delphinus delphis ponticus; CV = 16.77%, 95% CI[123, 427]). The highest estimates for all three species were obtained in the spring. Harbor porpoises and bottlenose dolphins were present in the study area throughout the year, while common dolphins left the region in winter. These findings offer valuable insights that can guide and inform future conservation strategies, aligning with national and international frameworks for the protection of these cetacean species.     

Dynamics of biological parameters of nonmigratory and invader fish in the basin of the lower Tom’ River

The species composition and dominating complexes of fish in catches are considered. The fraction of mass fish species in catches is shown (for small rivers and the channel zone). The structural (size and age) and functional (fertility) parameters of some nonmigratory and invader fish species are characterized. Main biological parameters are considered in the time-space aspect over the widespread and numerous fish species.     

Dynamics of the Reproduction Period of the Sea Raven Hemitripterus villosus (Hemitripteridae) in the Southwestern Part of Peter the Great Bay: Results of 20-Year Monitoring (1997–2016)

Journal of Ichthyology - The reproduction period of the sea raven Hemitripterus villosus were studied by visual SCUBA-diving methods in 1997–2016 in Peter the Great Bay, the Sea of Japan. It...     

Ecological Monitoring of the Water Area of Port Vostochnyi (Wrangel Bay) in the Sea of Japan (1995–2002)

Benthic surveys carried out in 1989 (literature data), 1995, and 2001 (original data) revealed changes in the structure of soft bottom communities of Wrangel Bay (Peter the Great Bay, Sea of Japan), where a deep-water port of Vostochnyi is situated. The functioning of the port has caused no significant environmental pollution by heavy metals, hydrocarbons, and other pollutants. Bottom dredging and the siltation induced by it have drastically lowered the benthos biomass, changed benthic communities, and altered their trophic structure. Sestonophages have disappeared nearly altogether being replaced by detrivores. The ecological state of the benthos is characterized as unstable.     

Environmental DNA as a ‘Snapshot’ of Fish Distribution: A Case Study of Japanese Jack Mackerel in Maizuru Bay,Sea of Japan

Recent studies in streams and ponds have demonstrated that the distribution and biomass of aquatic organisms can be estimated by detection and quantification of environmental DNA (eDNA). In more open systems such as seas, it is not evident whether eDNA can represent the distribution and biomass of aquatic organisms because various environmental factors (e.g., water flow) are expected to affect eDNA distribution and concentration. To test the relationships between the distribution of fish and eDNA, we conducted a grid survey in Maizuru Bay, Sea of Japan, and sampled surface and bottom waters while monitoring biomass of the Japanese jack mackerel (Trachurus japonicus) using echo sounder technology. A linear model showed a high R² value (0.665) without outlier data points, and the association between estimated eDNA concentrations from the surface water samples and echo intensity was significantly positive, suggesting that the estimated spatial variation in eDNA concentration can reflect the local biomass of the jack mackerel. We also found that a best-fit model included echo intensity obtained within 10–150 m from water sampling sites, indicating that the estimated eDNA concentration most likely reflects fish biomass within 150 m in the bay. Although eDNA from a wholesale fish market partially affected eDNA concentration, we conclude that eDNA generally provides a ‘snapshot’ of fish distribution and biomass in a large area. Further studies in which dynamics of eDNA under field conditions (e.g., patterns of release, degradation, and diffusion of eDNA) are taken into account will provide a better estimate of fish distribution and biomass based on eDNA.     

Behavior and seasonal variation in the relative abundance of Commerson’s dolphin (Cephalorhynchus commersonii) in northern Patagonia, Argentina

Commerson’s dolphins (Cephalorhynchus commersonii) along the Patagonian coast of South America suffer incidental mortality in fisheries and are the target of a dolphin-watching industry. We describe the daily activity patterns and assess the variation in the relative abundance of the species near the northern boundary of its range. Information was gathered with a spotting scope from a cliff-top vantage point applying the method of scan sampling. Behaviors were categorized as individual feeding, cooperative feeding, directional swimming, socializing, and resting. These behaviors are similar to those observed in other species of small cetacean, but differences were found regarding the patterns of directional swimming and feeding techniques. Hunting tactics favored the association of terns with dolphin groups. No clear dial behavioral pattern was observed, but seasonal changes in the frequency of behaviors were recorded. Group and school sizes were larger during periods with colder sea surface temperature (SST). Seasonal abundance was correlated with SST, suggesting that at higher SST the species forsakes the area, probably in favor of coastal areas to the south with lower SST.     

Effects of decadal changes in the hydrological regime of the middle reach of the Paraná River (Argentina) on fish densities

Changes in fish densities recorded over 14 years (1996–2009) were studied for effects of long-term variation of the hydrologic regime. We collected field data with an echo sounder in scour holes of minor channels draining an area of floodplain in the middle reach of the Paraná River. Fish densities in 2000–2009 were significantly lower than in the previous decade. The decrease was associated with a marked reduction of water levels, flood magnitudes and connectivity of channels with the nearby floodplain lakes. This distortion of the flood pulse likely had an effect on the life history strategies of the fishes. The effects of damming in the upstream basin and other man-made perturbations are minor in the middle reach. However, the decadal alterations of regime are intimately linked to climate fluctuations in the Paraná River basin during the past century. Tendencies of observed fish densities are similar to results reported in literature on the influence on fishes for similar long-term alterations of the flood regime in river flood plain systems.     

Vertical distribution and abundance of gymnamoebae (Rhizopoda) in bottom sediments of the brackish water Nivå Bay (Baltic Sea,The Sound)

The sandy sediments of Niv? Bay (Baltic Sea, The Sound, Denmark) are often covered with the mats of sulphur bacteria and are temporarily anoxic. The vertical distribution and abundance of naked amoebae species in three sediment cores from this bay were studied. Amoebae were most abundant and diverse in the upper 1 cm of sediment, and their number and diversity decreased with increasing depth into the sediment. Amoebae were recovered from both upper oxygenated and deep anoxic layers of sediments. The species composition and abundance of amoebae was very heterogeneous, even at spatial scales of several centimeters, suggesting the existence of microhabitats selectively occupied by particular species. All species found were recorded from aerobic cultures and some of these amoebae occur in both the aerobic and anaerobic layers of the sediment. Minimal possible number of amoebae in the sediments, estimated for the first time as areal abundance integrated for depth was: core 1 -597 cm(-2); core 2 -1,110 cm(-2); core 3 -1,430 cm(-2). These abundances are probably best regarded as "potential" abundances of amoebae hidden in the sediments, as the question of the ratio between active and resting amoebae remains open.     

Biological monitoring of fish and crustaceans in the Wadden Sea — potential and problems

Monitoring of fish and crustaceans in the Wadden Sea (WS) must cope with rapid changes in distribution patterns, access to certain areas and gear efficiency. Application and limitations of a variety of fishing devices (fyke nets, gill nets, enclosures, stow nets, purse seines, beam trawls, push nets, beach seines, bottom trawls, pelagic trawls) are discussed with regard to different objectives of monitoring. Furthermore, the validity of data from three current monitoring programmes is also discussed. Presented at the VI International Wadden Sea Symposium (Biologische Anstalt Helgoland, Wattenmeerstation Sylt, D-2282 List, FRG, 1–4 November 1988)     

Length–weight relationships of six indigenous fish species from the River Cauvery and its estuary,India

The present study estimated length–weight relationships (LWRs) for six indigenous fish species (Barilius gatensis, Salmostoma acinaces, S. boopis, Puntius amphibius, Hemibagrus punctatus and Ambassis miops) based on specimens collected from River Cauvery (including estuary) during July 2017–January 2020. The sampling surveys were carried out in three distinct sampling seasons, viz., the pre-monsoon (March–May), the monsoon (July–October) and the post-monsoon (November–February). Majority of the fish specimens dealt in the study were collected from multi-meshed monofilament gill nets (mesh sizes 18, 30, 45, 60, 90, 110, 120 and 150 mm) operated by local fishers. For those sites situated in the protected areas, sampling was carried out by cast nets with prior permission from the local administration and the collected fishes were released back into river after length–weight measurements. The length measurements were noted as total length (TL) measured to the nearest 0.1 cm by using a digital Vernier caliper. A digital balance was used for weight measurements with an accuracy of 0.01 g. The study recorded a new maximum length of 48 cm for H. punctatus. The LWR data generated from the present study are significant for proper assessment of the stock status and their management, if collected together with other essential biological and physical parameters.     

Biomass and abundance of macrofauna in intertidal sediments of Königshafen in the northern Wadden Sea

Intertidal sediments of Königshafen (Island of Sylt, North Sea) were sieved for mesofauna (>0.25 mm) and macrofauna (>1 mm) in spring and autumn 1990. Although sediments are coarser than in other parts of the Wadden Sea, the macrobenthic fauna was very similar but with a tendency towards higher species density, abundance and biomass. Taking into account the areal size of sandy flats, seagrass beds, mud flats and mussel beds, the average biomass is calculated to be 65 g ash-free dry weight m^?2 The lugwormArenicola marina dominates the biomass (28%), followed by the bivalvesMytilus edulis (21%),Mya areanaria (16%),Cerastoderma edule (10%) and the mudsnailHydrobia ulvae (9%). While spring and autumn biomass are almost alike, abundance is highly variable and entirely dominated byH. ulvae. Mesofauna is mainly composed of oligochaetes, small and juvenile polychaetes. Abundance is similar to that of macrofauna, while biomass is only about 1 g m^?2. Macrophyte biomass amounted to 9% of that macrofauna. In the course of the centurym mussel beds expanded while muddy areas declined. The concomitant effects on biomass presumably compensated each other.