Nondestructive Monitoring of Soft Bottom Fish and Habitats Using a Standardized, Remote and Unbaited 360° Video Sampling Method

Lagoon soft-bottoms are key habitats within coral reef seascapes. Coral reef fish use these habitats as nurseries, feeding grounds and transit areas. At present, most soft-bottom sampling methods are destructive (trawling, longlining, hook and line). We developed a remote, unbaited 360° video sampling method (RUV360) to monitor fish species assemblages in soft bottoms. A low-cost, high-definition camera enclosed in a waterproof housing and fixed on a tripod was set on the sea floor in New Caledonia from a boat. Then, 534 videos were recorded to assess the efficiency of the RUV360. The technique was successful in sampling bare soft-bottoms, seagrass beds, macroalgae meadows and mixed soft-bottoms. It is easy to use and particularly efficient, i.e., 88% of the stations were sampled successfully. We observed 10,007 fish belonging to 172 species, including 45 species targeted by fishermen in New Caledonia, as well as many key species. The results are consistent with the known characteristics of the lagoon soft bottom fish assemblages of New Caledonia. We provide future users with general recommendations and reference plots to estimate the proportion of the theoretical total species richness sampled, according to the number of stations or the duration of the footage.

Long-term dynamics of biomass and dominant species of the bottom fish complex in Peter the Great Bay

Dynamics of demersal fish biomass is considered on results of trawl surveys conducted in Peter the Great Bay (Japan Sea) in 1977-2015. Fishery did not have a significant impact on this complex of fish species, including both fluctuating species (walleye pollock, arabesque greenling, pacific herring) and species with stable stock, because of low intensity. Annual landings in the bay were much lower than recommended volumes (TAC). However, a tendency to the total biomass decreasing was observed, accompanied with growth of the sculpins (Cottidae) portion in the ratio of species biomass. The sculpins prey on juveniles of many other species, so maybe their higher abundance was one of reasons for general depletion of the benthic fish community. Other predators, as marine mammals, were not abundant in Peter the Great Bay. For rational resource management, the fishery impact should be distributed proportionally between populations, taking into account their state, so both traditional commercial objects and predators with growing abundance should be landed. This ecosystem approach requires permanent monitoring to all groups of fish species.

INDEKS PERTUMBUHAN IKAN KAKAP MERAH DAN KERAPU LUMPUR PADA PERIKANAN BUBU DASAR DI PERAIRAN BUNYU

Pulau Bunyu di Propinsi Kalimantan Utara memiliki sumberdaya hayati ekosistem perairan laut yang berlimpah dan bernilai ekonomis yang tinggi, dimana masyarakat pulau Bunyu memanfaatkan potensi ekosistem perairan laut digunakan sebagai potensi perikanan dalam hal penangkapan dengan menggunakan alat tangkap bubu dasar (bottom fish pot). Hasil tangkapan yang bernilai ekonomis berupa ikan kakap merah dan ikan kerapu yang terdapat di perairan ekosistem laut pulau Bunyu. Tujuan penelitian adalah menganalisis pertumbuhan dan struktur ukuran ikan kakap merah (Lutjanus argentimaculatus) serta ikan kerapu lumpur (Epinephalus malabaricus) yang berasal dari perairan pulau Bunyu. Data yang diteliti berupa parameter pertumbuhan yaitu panjang total dan panjang standar, berat total, jenis kelamin, tingkat kematangan gonad, dan berat gonad. Hasil penelitian ikan kakap paling banyak tertangkap ukuran panjang 40,49-47,61 cm dan bobot 990,05-1.451,68 gram. Pada ikan kerapu lumpur dengan ukuran panjang 43,73-50,13 cm dan berat 800,94-1.308,70 gram. Sifat pertumbuhan pada ikan kakap merah adalah allometrik negatif. Nilai indeks kondisi berbentuk kurus pada sampel ikan kakap merah. Sifat pertumbuhan pada sampel ikan kerapu pada variabel panjang total dengan berat total bersifat allometrik positif dan pada variabel panjang standar dan panjang cagak dengan berat total bersifat allometrik negatif.

Hydraulic structures and devices works providing a non-contact technology for fish release, seining and transfer of fish cultivated in fish breeding complexes

Purpose: development of an outlet and fishing structures works, providing for fish release from fish-breeding reservoirs, their seining, transfer and inlet into feeding reservoirs using non-contact technology. Materials and methods. The basis of the research was the data of studying the applied technologies, structures and means of intra-complex fish transfer between fish-breeding facilities and during stocking of reservoirs. Results. When fish are cultivated in fish breeding complexes, it is necessary to transfer them from nursery reservoirs to wild or stocked objects for fish farming and their biological reclamation. When providing fish-breeding activities, fish are released from nursery reservoirs by means of water outlets, seined in fish-traps, transfered and released into a water body. The applied complexes of structures provide for a physical effect on fish, which leads to injury to a part of the fish planting material. To exclude this, design solutions for fish outlet and fish processing facilities and live fish containers operating in the complex, providing the release, seining, transfer and inlet of fish using non-contact technology with technical means are proposed. Conclusions. A layout and design solution for a unit of linearly spaced interconnected fish-breeding structures, including a bottom fish outlet and a container fish trap, providing, when they work together, release and seining fish fry cultivated in fish-breeding reservoirs, is proposed. The applied and proposed technological schemes of functioning of the complex of structures, devices and means for fish release from fish-breeding basins, their catching, transfer and admission to the feeding reservoir are presented. A constructive solution for a live fish container for non-contact fishing, movement and admission of fish stocking material into the reservoir to be stocked is proposed.

The influence of the climatic and oceanological conditions on the stock dynamics of some commercial species of pelagic and bottom fish communities of the eastern part of the Sea of Okhotsk

Stepwise multidimensional regressive analysis was carried out based on the long-term data (1971–2018), including biological statistics and series of observations on 10 climate indices, allowing to identify the most meaningful climatic factors affecting the numbers of some fish species at different stages of the ontogenesis in the Eastern part of the Sea of Okhotsk. All the results obtained indicate of existing true correlations with the number of the two-years-old individuals and the number of the fish reached the age of the mass (>50%) maturation. Threedimension regression models, describing the dynamics of the initial number of some fish satisfactorily. Were made, based on the obtained equations of multiple regression of the relationship between the number of the fish and the most effective climatic indices selected. The major indices affecting the abundance of different fish species are: SST, NPGO, SanSpot – Pacific herring; NPA – saffron cod; PDO – Pacific cod; NPA, SanSpot – great sculpin; SanSpot, PNA, AO – yellowfin sole; PDO, SSTa – Pacific halibut; Ice SanSpot, NPGO – Greenland turbot. Pelagic, demersal and bottom species are under the complex influence of the oceanographic, meteorological and planetary-space indices.

Bycatches of the red king crab in the bottom fish fishery in the Russian waters of the Barents Sea: assessment and regulations

An analysis of red king crab bycatch in bottom-trawl fisheries in the Russian exclusive economic zone (EEZ) in the Barents Sea based on data collected from 2010 to 2019 shows an annual range of 2.2–9.8 thousand tonnes of crab bycatch from 2010 to 2018, which is 0.7–2.9% of the total biomass of red king crab in the EEZ. It was found that the catch of commercially valuable male crabs in the bottom-trawl fishery ranged from 1.4 to 6.5 thousand tonnes, which is ∼0.7–3.3% of the total commercial stock. A protected area created in 2006 is estimated to prevent the catch of 1.1–4.8 thousand tonnes of crab; however, protective measures do not take into account the peculiarities of the current distribution of crab populations and the geography of the fishing area. This work offers suggestions for improving the regulatory measures to protect the king crab stock in Russian waters of the Barents Sea.

Species composition and distribution of fishes and prawns in the Amur River channel

istribution of fishes and prawns in the Amur River (40–960 km from the mouth) is described on results of the beam-trawl survey conducted in September-October, 2003 (57 trawl stations at the depth of 1.5–23.0 m). In total, 2584 ind. of 22 fish species and 1077 ind. of 1 invertebrate species (prawn Palaemon modestus) were caught. The highest species richness was registered for orders Cypriniformes (13 species) and Siluriformes (4 species). The fish and prawn stocks were evaluated as 32.161 . 106 ind. (583.8 t) for bottom and near-bottom fish and 4.887 . 106 ind. (8.8 t) for prawns. Two commercial fish species were the most abundant: catfishes Tachysurus brashnikowi (16.26 . 106 ind. or 32.9 % of total biomass) and T. sinensis (4.32 . 106 ind. or 24.0 % of total biomass); other 6 fish species with considerable biomass were lizard gudgeon Saurogobio dabryi (12.6 %), ussuri catfish T. ussuriensis (9.7 %), amur white-pinned gudgeon Romanogobio tenuicorpus (7.8 %), amur sturgeon Acipenser schrenckii (5.6 %), amur gudgeon Gobio cynocephalus (2.4 %), and kaluga Huso dauricus (0.6 %). Distribution density varied in the range of 0.01–2.57 g/m2 (on average 0.45 ± 0.27 g/m2) for fish and 0.005–0.044 g/m2 (0.021 ± 0.012 g/m2) for prawns. Abundance of both fish and prawns increased multifold towards the Amur mouth that correlated with increasing of forage benthos biomass in the same direction. So, the main portion of fish biomass (82.4 %) was distributed in the Amur River downstream (40–400 km from the mouth) and the prawn stock was concentrated completely in its lowermost part (50–150 km from the mouth).

PECULIARITIES OF BOTTOM FISH TRADE (HALIBUT, SKATE, GIANT GRENADIE, COD, LYCODES, BROADBANDED THORNYHEAD) IN THE NORTH OKHOTSK SEA FISHING SUBZONE OF THE SEA OF OKHOTSK IN 2019

Based on the materials collected in 2019, the authors consider some peculiarities of bottom fish fishing (halibut, stingrays, giant grenadie, cod, lycodes, and broadbanded thornyhead) in the North Okhotsk subzone of the Sea of Okhotsk. The accompanying problems are shown; the measures to optimize fishing are proposed.