The ecological tourism in the islands of Peter the Great Bay (Sea of Japan)

The article considers the objects and main types of ecological tourism on the islands of Peter the Great Bay (Sea of Japan). The accelerated pace of socio-economic development in the Primorsky Krai, its strengthening cooperation with the countries of the Asia-Pacific region (ATR), the annual holding of economic summits in Vladivostok make the tourism industry a promising path of the economic development. The Primorsky Krai is a leader in the development of tourism and recreation in the Far East. Ecological tourism is a journey through nature. The main types of ecological tourism are scientific, educational and recreational ones. A trip to nature should be combined with respect for the latter, the study, protection, and restoration of unique landscapes. Ecological tours are offered to vacationers as an alternative to traditional long-distance travels to foreign countries. The Peter the Great Bay is the largest bay in the Sea of Japan at the coast of Russia. The large and small islands of the bay, the island territories of Vladivostok (Russkiy, Popova and Reineke) and the adjacent waters of the Sea of Japan are natural complexes with a unique nature and favorable climate. Sandy beaches and amazingly beautiful shores, convenient bays and inlets, are good objects for the development of various types of ecological tourism.

Growth and survival of the hatchery juveniles of pacific oyster Crassostrea gigas (Thunberg, 1793) in Peter the Great Bay

Growth and survival rates of juveniles of pacific oyster Crassostrea gigas are estimated for the first time in conditions of Peter the Great Bay (Japan Sea). The data were collected at artificial hatchery in the Aquaculture Center located on Popov Island in 2019. The juveniles were settled and reared on two types of substrate: 1) perforated plastic plates with the diameter of 30 cm (area 7.1 dm2), and 2) scallop shells with the height about 10 cm (average area 0.8 dm2) mounted in the western Peter the Great Bay (Voevoda Bay) in September 2019. Before placing in this site, the average height of the juveniles’ shells did not exceed 7 mm. In July 2020, after the 9-month exposure of the collectors with spat in the Voevoda Bay, the height increased in 12–18 times and reached 55–90 mm on the substrate 1 and 25–65 mm on the substrate 2. Then the oysters reared on the substrate 1 were replaced from the plastic plates to the cage shelves and the cages were moved to the Stark Strait. Difference in the growth rate became more apparent in September 2020, when the height of shells settled on the plastic plates reached 67 mm, on average (73 % in the range 50–85 mm) and for the shells settled on the scallops — 32 mm, on average (72 % in the range 20–45 mm). The shell height increased to 76.6 and 52.4 mm, respectively, to the end of October 2020. Finally, about 59 % of the oysters reared on the substrate 1 and cage shelves and 9 % of the oysters reared on the substrate 2 reached the commercial size (80–100 mm). Their survival in the period from mid-October 2019 to July 2020 is estimated as 46.9 % (28.8–98.2 %) for the substrate 1 and 33.5 % (4.0–78.3 %) for the substrate 2. On the substrate 1, survival of the mollusks attached to lower surface of the plates was twice higher. The survival had a tendency to decrease with increasing of the juveniles density. The experiment showed good viability for artificially hatched juveniles of pacific oyster in conditions of Peter the Great Bay. Their growth in the Voevoda Bay and the Stark Strait, with necessary technological measures, as replacing, thinning, and substrate cleaning from fouling, allows to produce oysters with the commercial size.

Сurrent state of artificial reproduction of chum salmon in Primorye Region

Results of 4 salmon hatcheries operation in Primorye Region are overviewed. Dynamics of chum salmon producers return to the rivers is presented for 4 last years. Recent tendency of shifting the peak of return from middle October to late September — early October is noted both for the rivers flowing into Peter the Great Bay (Barabashevka) and for the rivers of central Primorye (Verbnaya and Milogradovka). High percentage of producers aged 2+ was observed in the hatchery rivers in some years (32.9 % in the Barabashevka in 2019, 31.0 % in the Verbnaya in 2020, 37.8 % in the Bezymyanny in 2020). Interannual fluctuations in the number of producers return are possibly caused by malfunctions of hatcheries. A problem of water supply to the hatcheries is considered. Expediency of temperature control at hatcheries is shown. Data on release of chum salmon juveniles in the last decade are presented for each hatchery: the number of juveniles released, the average weight of juveniles, and the timing of release. Total release to the Barabashevka River was 119.29 . 106 juveniles, to the Ryazanovka — 114.24 . 106 juveniles, to the Poyma — 49.43 . 106 juveniles, to the Narva — 6.02 . 106 juveniles, to the Brusya — 3.11 . 106 juveniles, to the Verbnaya — 69.66 . 106 juveniles, to the Milogradovka — 1.00 . 106 juveniles, to the Lidovka — 1.71 . 106 juveniles, to the Bezymyanny — 69.45 . 106 juveniles, and 2.00 . 106 juveniles each to the Kievka and Margaritovka Rivers.

Hypoxia in Peter the Great Bay

Studies on hypoxia in Peter the Great Bay (Japan Sea) are reviewed. Seasonal hypoxia is observed in warm season at the bottom of three areas: Amur Bay, Ussuri Bay, and the southwestern part of Peter the Great Bay occupied by the Far-Eastern Marine Biosphere Reserve (FEMBR). Processes of the hypoxia forming are similar in all these areas. The main reason is the dissolved oxygen consumption by microbial degradation of organic matter within topographic depressions in conditions of limited ventilation because of strong summer stratification. The bottom depressions prevent horizontal water exchange and provide accumulation of organic and inorganic suspension, that is another factor important for development of hypoxia. The Amur Bay is the most subjected to hypoxia, being a semiclosed estuarine basin eutrophed by nutrients input from the Razdolnaya River and waste waters of Vladivostok city. The Ussuri Bay has better water exchange and less eutrophication, therefore there are scarce data about hypoxia in this area. FEMBR area has good water exchange and is only episodically influenced by nutrients discharge from the Tumen River, so hypoxia is observed there occasionally. Another consequence of microbial degradation of organic matter in these areas is acidification: pH decreased in 0.5 unit in the bottom water of the Amur Bay in eight decades from 1932 to 2013. Synchronism between regional and global processes of eutrophication, deoxygenation, and acidification of bottom waters is discussed.

Growth and survival of the hatchery larvae of pacific oyster Crassostrea gigas under different concentrations of microalgae and salinity in conditions of southern Primorye

Growth and survival rates for larvae of pacific oyster Crassostrea gigas (Thunberg, 1793) hatched in artificial conditions are estimated for the stages of development from D-veliger to pediveliger. The experiment was conducted in the Mariculture Center located on Popov Island (Peter the Great Bay, Japan Sea) for 2 regimes of feeding and water salinity of 26 and 32 ppt. Microalgae Isochrysis galbana, Chaetoceros muelleri and Phaeodactylum tricornutum cultivated in the Mariculture Center were used as a feed in both regimes, in different concentrations. The maximum concentration was 4-fold higher than the minimum one: daily doses of food were 20 and 5 thousand cells/mL for veligers, 40 and 10 thousand cells/mL for early veliconkhes, and 80 and 20 thousand cells/mL for late veliconkhes, respectively, whereas 80 thousand cells/mL for all larvae in transition to pediveliger stage. Statistically significant difference of the growth rate was found for cases with different food concentration (p < 0.05). The larvae with better feeding had higher growth rate under salinity of both 26 and 32 ppt. Besides, the lowered salinity (26 ppt) had some positive effect for growth in the regime of better feeding. Survival rate of the larvae from D-veliger to pediveliger was high under all regimes of the experiment and was estimated for the minimal diet as 77.4 and 64.7 % under salinity of 26 and 32 ppt, respectively, and for the maximum diet as 81.2 and 80.7 % under salinity of 26 and 32 ppt, respectively. According to the experiment results, deficit of food at early stages of the oyster larval development affects negatively on their growth but does not have significant impact on their survival.

Long-term mean biomass and dominant fish species in the bottom and near-bottom biotopes of Peter the Great Bay

Biomass and species composition of demersal fish in the bottom biotopes of Peter the Great Bay (Japan Sea) are considered on the data of 2428 trawl catches in 36 surveys conducted by Pacific Res. Inst. of Fisheries and Oceanography (TINRO) in 1978–2009. The most common 20 species are ranked, as the basis of ichthyocenoses, by areas of the bay. The long-term mean total biomass of fish in the bay is estimated as 75,500 t. Arabesque greenling Pleurogrammus azonus, japanese flounder Pseudopleuronectes yokohamae and saffron cod Eleginus gracilis are distinguished by the highest mean biomass. Mean density of fish distribution varied from 6.2 to 19.4 t/km2. It was the highest in the middle Ussuri Bay (13.95 t/km2; mean fish biomass in the area 18,230 t) and in the estuarine areas. Besides, the data on long-term mean biomass of benthos collected in the same trawl surveys and zooplankton sampled in 117 plankton surveys in 1988–2013 are presented.

Express Image and Video Analysis Technology QAVIS: Application in System for Video Monitoring of Peter the Great Bay (Sea of Japan/East Sea)

The article describes the technology of express analysis of images and videos, recorded by coastal video monitoring systems, developed by the authors. Its main feature is its ability to measure or evaluate in real time the signals of sea waves, sea level fluctuations, variations of underwater currents, etc., on video recordings or streaming video from coastal cameras. The real-time mode is achieved due to processing video information read not from files, but from the graphic memory of the screen. Measurements of sea signals can be carried out continuously for a long time, up to several days, with high sampling rate, up to 16 Hz, at several points of the observed water area simultaneously. This potentially allows studying the entire spectrum of wave movements, from short waves with periods of 0.3–0.5 s to multi-day fluctuations at the sea level of a synoptic scale. The paper provides examples of the use of this technology for analyzing images and videos obtained in the network of scientific video monitoring of the Peter the Great Bay (Sea of Japan/East Sea), deployed by the authors.

Acidification and Deoxygenation of the Northwestern Japan/East Sea

Seasonal hypoxia in the bottom waters of the Peter the Great Bay (PGB) of the Japan/East Sea (JES) occurs in summer. Using the empirical relationship between dissolved oxygen (DO) and pH obtained for hypoxic conditions and available historical DO data, acidification rates were estimated. Carefully sampled time-series observations from the northwestern part of the JES, carried out from 1999 to 2014 along the 132°20′ E and 134°00′ E longitudes, were chosen to determine the interannual variability of the sea’s hydrochemical parameters (DO, pH, and TA—the total alkalinity phosphates, nitrate, and silicates). To limit the effects of seasonal and spatial variability, only data obtained in the warm period were used. Additionally, all data from depths shallower than 500 m were discarded because they are affected by high natural variability, mostly due to strong mesoscale dynamic structures. Our results demonstrated that the pH and DO concentrations measured in the Upper Japan Sea Proper Water (750 m), Lower Japan Sea Proper Water (1250, 1750, 2250 m), and Bottom Water (3000 m) have been decreasing in recent years. On the other hand, calculated normalized dissolved inorganic carbon (NDIC), CO2 partial pressure (pCO2), and measured nutrient concentrations have been increasing. Maximum rates of acidification and deoxygenation are occurring at around 750 m. The annual rate of increase of pCO2 in the water exceeds the atmospheric rate more than 2-fold at a depth of 750 m. The observed variability of the hydrochemical properties can be explained by the combination of the slowdown ventilation of the vertical water column and eutrophication. However, the results obtained here are valid for the subpolar region of the JES, not for the whole sea. The synchronization of the deoxygenation of the open part of the JES and PGB has been found.