Seasonal changes of biological condition and reproductive cycle of hampback shrimp Pandalus hypsinotus (Caridea, Pandalidae) in the Tatar Strait

Research and commercial trawl catches of humpback shrimp Pandalus hypsinotus from the Tatar Strait (Japan Sea) in 2004–2020 were investigated, with bioanalysis of about 45 thousand specimens. Average timing of group molting, spawning, and eggs laying are determined, terms of gonads and eggs development are estimated. Prespawning and molting of the females occur between January-April, with the peaks in early February and middle February, respectively. All oviparous females have 30–40 days to lay eggs, and molt during 50–55 days; the peak of the eggs laying occurs in late June. The males molt in July-August, afterwards the largest individuals change gender and new intersexes are formed. The males have the second molting in October-December, with the peak in late November. In January, after finish of the males molting, a new annual reproduction cycle starts from the prespawning molting of females. Both vitellogenesis and embryogenesis are observed through the year, though females with developing gonads prevail from August to January (because of a long time span between winter and summer moltings while the egg carrying continued 15 months) but oviparous females — from February to July. The individual reproductive cycle of Pandalus hypsinotus in the Tatar Strait lasts 24 months, with 9 months of vitellogenesis (quick growth of gonads) and 15 months of embryogenesis. During the 2-year reproductive cycle, most of females pass through the following stages: i) gonads development (just after eggs laying) when almost all oviparous females (up to 95 % in May) have green gonads under carapace that corresponds to the stage of development «eggs laid — gonads weakly developed»; ii) summer molting from August when females lose hairs on pleopods and the gonads growth accelerates; iii) respawning in January-March (together with the firstly spawning intersexes, with slight delay of the latter); iv) initial developing of eggs during summer; v) stage of «eyed eggs» from December to March; and vi) eggs laying and molting from late March to late May; then the 2-year reproductive cycle repeats.

The demersal fish composition and catch per unit effort of mini bottom trawl at the coast of Demak Regency Central Java

Demak is a coastal area on the North Coast of Java with a large enough potential for demersal fish resources. This research aimed to determine the composition, the length and weight distribution, and catch per unit effort (CPUE) of demersal fish caught using mini bottom trawl at the north coast of Demak Regency. The research was carried out in October-December 2020 by observation of ten trips of mini bottom trawl fishing. Each fish captured was then grouped by type, identified, and measured its length and weight. The result showed that 38 species consist of 31 fishes, four mollusks, and three crustaceans. The fish captured dominated by pony fish (Leiognathus equulus) as much as 31.23% and largehead hairtail (Trichiurus lepturus) of 23.52%. The catch per unit effort (CPUE) average of mini bottom trawl was 44.77 kg/trip. Mainly fish (more than 95%) caught in small size compared it’s the maximum attainable length (L-max), with all the weight ranges from 0.3 to 520 g and more than 98% sized 0.3-80 g. Mini bottom trawl catches many types of fish and small size; therefore, mini bottom trawl is classified as a type of fishing gear with a very low selectivity level.

New findings of light dusky rockfish Sebastes variabilis (Sebastidae) at the eastern coast of Kamchatka

Light dusky rockfish Sebastes variabilis is a rare fish species in the waters at East Kamchatka, rarely recorded in trawl catches. They aggregate in the areas with complicated bottom topography and active water dynamics with the depth from 118 to 316 m. Their maximum catches are recorded off Capes Gowen, Olyutorsky, and Kronotsky. The light dusky rockfish body length varies from 34 to 50 cm, and body weight — from 0.53 to 1.78 kg. Some issues related to the migration routes of this species to the shores of Kamchatka are discussed.

Preliminary results of fisheries research in the East Siberian Sea at the RV «Professor Levanidov» in September 2019

The results of complex research carried out in the East Siberian Sea on board of RV “Professor Levanidov” in September 2019 are presented. The formation of positive air temperature anomalies over the sea, the expansion of the zone of river flow influence in the central and southeastern parts of the shelf, and an abnormal decrease in sea ice cover were noted. Arctic water masses and the waters of the East Siberian Sea were dominant on the shelf. At depths of more than 180 m, waters of Atlantic origin were well traced by salinity more than 34.5 ‰, positive temperature and silicon content less than <10 μM. Photosynthesis processes were limited by nitrogen, whose concentrations in the photic layer were reduced to analytical zero. Summer phase of phyto- and zooplankton development was observed in most of the sea. The main contribution to the total biomass of mesoplankton was made by copepods and chaetognaths. Plankton biomass on the inner shelf was twice as high as on the outer shelf. The average benthic biomass in trawl catches was 15 kg per mile, of which up to 74 % was echinoderms and 9 % crustaceans.17 fish species from 6 families were registered in trawl catches. The dominant species was the polar cod Boreogadus saida found in small numbers almost everywhere at depths 33 to 250 m with bottom temperatures from –1.7 to 0.47 °C, kept sparse, without forming dense aggregations. Maximum concentrations were observed in the southeastern part of the study area. High intensity of fish feeding was noted. Diets of polar cod and snailfishes (Liraridae) consisted mostly of hyperiids, gammarids, and copepods. The diet of capelin Mallotus villosus was dominated by copepods. Polychaetes and gammarids formed the bulk of the diet of sculpins (Cottidae). Microplastics are found in small quantities in the southeastern and central part of the sea only. Tissue samples were collected for population-genetic analysis, DNA‑barcoding studies, and analysis of aquaDNA.

Distribution, fishery and some features of biology for Sclerocrangon salebrosa and Argis lar (Caridea, Crangonidae) in the northwestern Okhotsk Sea

Trawl fishery of shrimps Sclerocrangon salebrosa and Argis lar in the Sakhalin Bay of the Okhotsk Sea has started in 2014 and develops rapidly. Meanwhile, spatial distribution of these species is not known well and their biology and stock dynamics are not studied. State of the fishery and distribution patterns of S. salebrosa and A. lar in the northwestern Okhotsk Sea are investigated on the data collected by the authors aboaed commercial fishing vessels and in the accounting trawl survey conducted aboard RV Dmitry Peskov in summer of 2019, as well as some features of their biology are considered. In total, 542 commercial trawl catches collected in 2015–2019 with horizontal opening 36 m from the depth of 39–140 m and 147 trawl catches collected during the survey with horizontal opening 16 m from the depth of 11–321 m are analyzed; 21,590 shrimp specimens caught within the period from June 23 to November 2 are examined. During 2014–2019, the number of shrimp fishing vessels in the Sakhalin Bay has increased from 1 to 6, their annual landing — from 78.7 to 642.0 t (376 t of S. salebrosa and 266 t of A. lar in 2019). Their mean catch per unit effort varied from 48 to 108 kg/hr of trawling for S. salebrosa and from 40 to 87 kg/hr for A. lar, with the average catch per trawling 379 and 346 kg, and average daily catch 1380 and 1144 kg, respectively. Night catches of S. salebrosa were in 2.7 times higher than the daily catches, on average (104.7 ± 45.7 kg/hr vs 39.1 ± 31.8 kg/hr); night catches of A. lar were in 2.0 times higher than the daily catches (80.2 ± 39.0 kg/hr vs 39.6 ± 34.2 kg/hr). Portion of A. lar in the summary catches of two species varied from 4 to 88 %, on average 48 %; besides, by-catch of fish (flounders, saffron cod, pollock, cod, sculpins, herring) and humpy shrimp Pandalus goniurus was considerable. So, the portion of the most valuable species (sculptured shrimp S. salebrosa) did not exceed ⅓ of the total catch, on average. The actual annual catches exceeded significantly the recommended volumes in 2017–2019, up to 164 % for S. salebrosa and 156 % for A. lar. According to results of the trawl survey in 2019, spatial distribution patterns for S. salebrosa and A. lar coincide in details in the northern Okhotsk Sea: both species are distributed at the depth between 20–145 m, with the densest aggregations (> 60 % of both stocks) located between Bolshoi Shantar Island and the northern tip of Sakhalin, southward from 55о 30′ N, where their biomasses reach 434 kg/km2 for S. salebrosa and 68 kg/km2 for A. lar. Total commercial stocks of these species within the North Okhotsk Sea fishery district were assessed in 2019 as 16.0 . 103 t for S. salebrosa and 3.8 . 103 t for A. lar. Reproductive cycles of S. salebrosa and A. lar females in the Okhotsk Sea are fundamentally the same as the cycle of former species in Peter the Great Bay (Japan Sea), with their total duration of 48 months including 24 months for the gonads development until spawning and 24 months from the spawning to hatching of larvae. In the Okhotsk Sea, spawning of S. salebrosa and A. lar occurs most likely in spring; mass hatching of their larvae — in summer.

SPATIAL DISTRIBUTION AND ECOLOGY OF EELPOUT LYCODES BRASHNIKOVI (ZOARCIDAE) AT THE WESTERN COAST OF KAMCHATKA IN SUMMER SEASON

Eelpout Lycodes brashnikovi is a common species of bottom ichthyofauna in the waters at West Kamchatka. It distributes through the whole surveyed area, with sporadic dense aggregations at the depths of 50–150 and 200–300 m. It is an eurythermic species. Adult fish with the length 36–45 cm prevail in its trawl catches (on average 59.3 %); its maximum length is 52 cm. Catches of other species from the family Zoarcidae are insignificant on the shelf of West Kamchatka in summer, so Lycodes brashnikovi is considered as the most numerous representative of this family in this season.

PRODUKSI UDANG DAN POLA MUSIM PENANGKAPANNYA DI PERAIRAN KABUPATEN PANGKEP

Shrimp is a type of crustacean and is included in the marine fishery commoditywhich has important economic value and is currently hunted by fishermen and iscommonly found in coastal waters. The purpose of this study was to determine the ShrimpProduction and Seasonal Catching Pattern in the Waters of Pangkep Regency. Itsusefulness is as a foundation material in the use of shrimp resources in the waters ofPangkep Regency. Data collected consists of primary data and secondary data. Primarydata is obtained by direct observation in the field through a field survey method (visualrecall) to portray the conditions of crab resources. While secondary data was collectedfrom the relevant agencies according to the attributes that will be reviewed and recordeddata from collecting fishermen in the coastal areas and small islands of PangkepRegency. Shrimp production from trammel net and mini trawl catches in the waters of theSigeri District of Pangkep Regency in 2015 consisted of 706 tons of white shrimp anddogol shrimp 4,481 tons, while in 2016 706 tons of white shrimp and dogol shrimp 4,481tons. Analysis of the percentage of shrimp fishing season index in the waters of PangkepRegency, occurred in January, February, March and April. The highest percentage offishing season index occurs in January each year.