Patterns of variability of species composition of catches from the russian fishing vessels in the south-eastern Pacific ocean for 2015–2022

Impact of El Niño events on pelagic fisheries in Peruvian waters

Abstract. Mesoscale eddies are important, frequent, and persistent features of the circulation in the eastern South Pacific (ESP) Ocean, transporting physical, chemical and biological properties from the productive shelves to the open ocean. Some of these eddies exhibit subsurface hypoxic or suboxic conditions and may serve as important hotspots for nitrogen loss, but little is known about oxygen consumption rates and nitrogen transformation processes associated with these eddies. In the austral fall of 2011, during the Tara Oceans expedition, an intrathermocline, anticyclonic, mesoscale eddy with a suboxic (< 2 µmol kg−1 of O2), subsurface layer (200–400 m) was detected ∼ 900 km off the Chilean shore (30° S, 81° W). The core of the eddy's suboxic layer had a temperature-salinity signature characteristic of Equatorial Subsurface Water (ESSW) that at this latitude is normally restricted to an area near the coast. Measurements of nitrogen species within the eddy revealed undersaturation (below 44 %) of nitrous oxide (N2O) and nitrite accumulation (> 0.5 µM), suggesting that active denitrification occurred in this water mass. Using satellite altimetry, we were able to track the eddy back to its region of formation on the coast of central Chile (36.1° S, 74.6° W). Field studies conducted in Chilean shelf waters close to the time of eddy formation provided estimates of initial O2 and N2O concentrations of the ESSW source water in the eddy. By the time of its offshore sighting, concentrations of both O2 and N2O in the subsurface oxygen minimum zone (OMZ) of the eddy were lower than concentrations in surrounding water and “source water” on the shelf, indicating that these chemical species were consumed as the eddy moved offshore. Estimates of apparent oxygen utilization rates at the OMZ of the eddy ranged from 0.29 to 44 nmol L−1 d−1 and the rate of N2O consumption was 3.92 nmol L−1 d−1. These results show that mesoscale eddies affect open-ocean biogeochemistry in the ESP not only by transporting physical and chemical properties from the coast to the ocean interior but also during advection, local biological consumption of oxygen within an eddy further generates conditions favorable to denitrification and loss of fixed nitrogen from the system.

Feeding conditions of the main commercial fish species are assessed and their feeding relationships are considered on the materials collected aboard RV Professor Levanidov and RV TINRO in the Pacific waters at Kuril Islands in July-August of 2015 and 2016 in the surveys targeted on evaluation of the subtropical species migrations, as Scomber japonicus, Scomber australasicus, Sardinops melanostictus , and Todatodes pacificus , as well as pre-anadromous migrations of salmons Oncorhynchus gorbusha and Oncorhynchus keta . Copepods, euphausiids, and hyperiids dominated in the diet of subtropical species, with exception of Scomber japonicus and Scomber australasicus with fish as a significant part of the diet and Sardinops melanostictus with phytoplankton in the diet. In the salmons diet, copepods, euphausiids, hyperiids, and pteropods prevailed for pink salmon and euphausiids, pteropods, hyperiids, and medusas for chum salmon. Daily and monthly rations were calculated for fish species and their ratio with the stock of large-sized zooplankton was determined. The main consumers of zooplankton were Scomber japonicus (49 % of total consumption in 2016) and Sardinops melanostictus (40 %) and the main consumers of nekton - Scomber japonicus , too (86 % of total consumption in 2016) and Scomber australasicus (13 %). Salmons consumed no more than 1 % in sum. In 2015, Scomber japonicus also was the main consumer (73-71 % of the total consumption of zooplankton and nekton) and salmons’ consumption was even lower. The stock of zooplankton, being in 18 times larger than the fish biomass, provided full feeding demand of the consumers. The stocks of the preferable preys, as euphausiids, copepods, and amphipods, exceeded their consumption in 15-25 times in 2016, though slight deficit of euphausiids was observed in 2015, compensated by high abundance of copepods, hyperiids, medusas and small-sized nekton.

The Peruvian Marine Research Institute — IMARPE, has been conducting scientific hydroacoustic survey since 1983 in order to estimate the biomass of the main pelagic resources for fishing management. The multifrequency analysis used for species identification was recommended in 2000 by the International Council for the Exploration of the Sea (ICES). From 2014 IMARPE began to use multifrequency acoustic (18, 38, 70, 120 and 200 kHz). The calibrated data was collected during the hydroacoustic assessment cruise of pelagic resources conducted in spring 2016. Multifrequency analyzes were performed with Echoview 5.2, which allowed the identification of pelagic species with similar acoustics properties with the use of different frequencies. The results showed that the anchovy juvenile (Engraulis ringens) (< 12 cm of total length) presented a greater resonance in the frequency of 18 kHz compared to the adult counterpart. Pacific chub mackerel (Scomber japonicus) and south jack mackerel (Trachurus murphyi) have similar curves, however, jack mackerel has higher energy values. Coastal species such as samasa (Anchoa nasus) and catfish (Galeichthys peruvianus) present an energy differentiation at the 18 and 70 kHz frequencies. The carrot squat lobsters (Pleuroncodes monodon) show an upward increase in energy from the frequency of 18 kHz, unlike the other species. For mesopelagic species, such as lightflsh (Vinciguerria lucetia), showed a similar tendency curve to the juvenile anchovy with slightly higher values. These analyses will continue to be carried out in order to increase the accuracy of the identification of pelagic resources, especially in the records detected during daytime hours.

The spawning grounds of the chub mackerel (Scomber japonicus) and spotted mackerel (Scomber australasicus) in the East China Sea were estimated based on catch statistics of the Japanese large- and medium-type purse seine fishery from 1992 to 2006. Biometric data were obtained from specimens caught by purse seiners in the East China Sea from 1998 to 2006. Gonadosomatic index (GSI) at 50% sexual maturity of chub mackerel and spotted mackerel females was 2.5 and 2.6, respectively. Using this criterion for GSI, chub mackerel larger than 275 mm and spotted mackerel larger than 310 mm in fork length were considered to be mature. Mature chub mackerel was observed in the area of 15–22°C sea surface temperature (SST), and mature spotted mackerel was observed in the area of 17–25°C SST. The spawning period of chub mackerel ranged from February to June, and that of spotted mackerel ranged from February to May in the East China Sea. The spawning grounds were estimated from the distributions of catch per unit effort (CPUE) of spawners and SST. As a result, the spawning ground of chub mackerel was estimated to be in the central and southern part of the East China Sea and the area west of Kyushu in February, March, and April, and in the central part of the East China Sea, the area west of Kyushu and Tsushima Straight in May, and in Tsushima Straight and western part of the Sea of Japan in June. The spawning ground of spotted mackerel was estimated to be in the central and southern part of the East China Sea and southern coastal area of Kyushu in February, March, and April, and the central and southern part of the East China Sea and the area west of Kyushu in May.

To characterize production from and to provide reserve estimates for low-permeability gas reservoirs in the Travis Peak Formation, East Texas Basin, reservoir parameters, such as permeability, porosity, water/gas saturation, and formation pressure, were calculated and analyzed. Production characteristics, such as absolute open flow potential, maximum production rate, decline rate, and gas/condensate production ratio, were examined. In addition to the results from completed studies of six gas producing fields, some data from incomplete field studies and from public records were also included in the regional interpretations. The study area lies within the central and eastern parts of the East Texas Basin and includes the western flank of the Sabine Uplift. Thickness-weighted average permeabilities and median permeabilities, which both represent the upper limits of gas permeability in the study area, are less than 0.1 md. Thickness-weighted field-average permeability ranges from 0.006 md in the southeastern part of the study area to 0.1 md in the northern part, with the exception of one field in the central part of the study area, which measured 2 md. About 57 percent of wells that have been completed in the six selected fields have permeabilities of less than 0.1 md. Field-average porosity ranges from 8 percent to 11 percent, with the exception of a field in the central part of the study area, which measured 14 percent. Water saturation varies from 24 percent to 43 percent and decreases from the northeastern part to the southwestern part of the study area. Gas fields in the northern and central parts of the study area are characterized by relatively high productivity and a weak water drive production mechanism, which contrasts with low productivity and a gas expansion production mechanism only in the southern and southeastern parts. Production decline curves from Travis Peak gas fields may be empirically characterized as having two linear sections with different slopes. The first linear section, which represents early production (a period of 3 to 5 years), is followed by a linear section of lesser slope representing later production. For the early years of production, the average production decline rate of the first linear section in the northern part of the study area (0.46 cycle/year) is lower than that of the southern part (1.28 cycle/year). A production decline rate of 0.3 cycle/year characterizes the central part of the study area. Maximum production rate decreases from 82,300 Mcf/month in the northern part of the study area to 11,700 Mcf/month in the southern part with the exception of a rate of 40,890 Mcf/month for a field in the southeastern part. About one-third of the gas wells in the northern area and more than one-half of the gas wells in the southern and western areas initially produced wet gas (gas to condensate ratio between 5 to 100 Mcf/bbl). In the study area, specific gravity of produced gas ranges from 0.62 to 0.66 (air = 1), and API gravity of produced condensate ranges from 50° to 60°. Formation temperature ranges from 200° F to 245° F. Some wells in gas fields in the northern and central parts of the study area produce oil. Potential fluid migration in the study area in the Travis Peak Formation may be from the southwest toward the northwest, in part because initial average formation pressure decreases from 4,540 psi in the southwestern parts of the study area to 3,076 psi in the northeastern parts.

The Tug Hill aquifer, in northern New York, is a 47-mile-long, 0.25-to-3.5-mile-wide, crescent-shaped Pleistocene sand and/or gravel deposit. The northern and central parts of the aquifer are under water-table conditions; the southern part has both water-table and discontinuous confined conditions. Groundwater and streams in the northern and central parts flow westward; those in the southern part flow from the edges of the valley to West Branch Fish Creek, which flows southeastward along the center of the valley. Principal sources of aquifer recharge are (1) infiltration of precipitation on the aquifer, estimated to be 137 million gallons per day, (2) infiltration form small streams that cross the north half of the aquifer, estimated to be 4.9 million gallons per day, and (3) seepage of runoff from adjacent till and bedrock, estimated to be 11.4 million gallons per day. Groundwater discharges from the aquifer (1) by evapotranspiration, (2) through pumping, (3) as subsurface flow the southern end of the aquifer at McConnellsville, (4) as seepage to springs, wetlands, and streams along the western margin of the central and northern parts of the aquifer, and (5) as seepage to tributary streams and West Branch Fish Creek on the valley flat. Good-quality water thatmore » is suitable for drinking and most other uses is found in most parts of the aquifer. The pH of the groundwater in the study area ranges from 5.9 to 8.0, with a median of 7.5. Water in the northern part, which is underlain by limestone, has a specific conductance and higher concentrations of hardness, alkalinity, calcium, and sulfate than water in other parts of the aquifer, which are underlain by shale, siltstone, and sandstone. Median concentrations of hardness, dissolved solids, chloride, and sulfate in the Tug Hill aquifer were less than those in six other upstate New York aquifers.« less

The Pan-African NE–SW elongated Bandja granitic pluton, located at the western part of the Pan-African belt in Cameroon, is a K-feldspar megacryst granite. It is emplaced in banded gneiss and its NW border underwent mylonitization. The magmatic foliation shows NE–SW and NNE–SSW strike directions with moderate to strong dip respectively in its northern and central parts. This mostly, ferromagnetic granite displays magnetic fabrics carried by magnetite and characterized by (i) magnetic foliation with best poles at 295/34, 283/33 and 35/59 respectively in its northern, central and southern parts and (ii) a subhorizontal magnetic lineation with best line at 37/8, 191/9 and 267/22 respectively in the northern, central and southern parts. Magnetic lineation shows an ‘S’ shape trend that allows to (1) consider the complete emplacement and deformation of the pluton during the Pan-African D 2 and D 3 events which occurred in the Pan-African belt in Cameroon and (2) reorganize Pan-African ages from Nguiessi Tchakam et al. (1997) compared with those of the other granitic plutons in the belt as: 686 ±17 Ma (Rb/Sr) for D 1 age of metamorphism recorded in gneiss; and the period between 604–557 Ma for D 2–D 3 emplacement and deformation age of the granitic pluton in a dextral ENE–WSW shear movement.

Background. In Mexico, the Gulf of Mexico snapper’s fishery contributes 30% of the national snapper landings through a multi-species fishery where red Lutjanus campechanus (Poey, 1890), yellowtail Ocyurus chrysurus (Bloch, 1791) and lane Lutjanus synagris (Linnaeus, 1758) are the main target species. Goals. To evaluate the stock status of the three main species and to calculate reference points: Catch at Maximum Sustainable Yield (MSY), Biomass associated with MSY (BMSY) and Fishing Mortality associated with MSY (FMSY) for the management of these fisheries in the Gulf of Mexico. Historical official landings records were used in the application of the Monte Carlo method C-MSY. Results. The most probable maximum intrinsic rate of population increase (r) and carrying capacity of environment population (k) values for the C-MSY method were for L. campechanus 0.56 and 35,109 t, for O. chrysurus 0.56 and 13,814 t; and for L. synagris 0.55 and 1,932 t. MSY values found were 4,964 t, 1,953 t and 269 t respectively. BMSY values were 17,554 t, 6,907 t and 966 t respectively. FMSY values were 0.28 for L. campechanus and O. chrysurus, and 0.27 for L. synagris. Conclusions. This study shows that only the L. synagris stock is overfished, while O. chrysurus is the only stock experiencing overfishing. To maintain the L. campechanus stock at healthy levels we recommend a total allowable catch (TAC) of 4,467 t per year. To reduce overfishing and maintain the O. chrysurus stock at healthy levels we recommend a TAC of 1,562 t. Finally, to rebuild the L. synagris stock and prevent overfishing, we recommend a TAC of 215 t.

Marine protected areas have become one of the main tools in the battle to curb marine biodiversity loss and habitat degradation. Yet, implementation of permanent fishery closures has often generated resource user conflicts that ultimately undermine conservation goals. Here we assessed the influence of an alternative and often more accepted measure – seasonal fish spawning closures – on large predatory fish and coastal food webs in the western Baltic Sea (Sweden). In spring 2017, we conducted a multivariable field survey in 11 seasonal closures and 11 paired references areas open to fishing. In each area, pike was sampled through angling, and perch and mesopredators through gillnet surveys. To assess trophic cascades, we measured zooplankton abundance and loss of tethered gammarids from predation. Catches per unit effort of northern pike (Esox lucius) – the main target species in recreational fisheries – were ca. 2.5 times higher per unit effort in closures than reference areas; an effect that may be caused by higher abundance and/or higher catchability of pike in the absence of fishing. Catch and weight per unit effort of the more common predator European perch (Perca fluviatilus), and the mesopredators roach (Rutilus rutilus) and three-spined stickleback (Gasterosteus aculeatus) in survey nets were, however, unaffected by closures. Moreover, a previously hypothesized trophic cascade from perch to zooplankton via three-spined stickleback was supported by the analyses, but appeared independent of closures. Yet, predation risk for tethered gammarid amphipods (a prey of stickleback and an important grazer on macroalgae) was three times higher in fished areas than in closures; a cascading closure effect that may potentially be caused by small predatory fish being less active in protected areas to avoid pike predation. Overall, our results suggest that spawning closures impact pike abundance and/or behavior and could help limit the effects of fishing, but that more research is needed to disentangle i) what mechanism(s) that underlie the protection effect on pike catches, ii) the apparently weaker closure impacts on other fish species, as well as iii) the potential for cascading effects on lower trophic levels. Therefore, new seasonal spawning closures should be implemented in addition to (and not instead of) much-needed permanent closures, which have well-known effects on the wider ecosystem.

A series of studies were conducted during two cruises between Tokyo and Honolulu in September 2010 and from February to March 2012. The aims of the studies were to (1) compare the distribution of three species of Halobates oceanic skaters, H. germanus, H. micans, and H. sericeus, with respect to their temperature limits; (2) identify the lower temperature limit of H. sericeus, the species that displays the widest distribution range (40°N–35°S) latitude; and (3) test the hypothesis that H. sericeus can change their temperature tolerance to adapt to seasonal changes in sea surface temperatures. The heat coma temperature (HCT) was measured during the two cruises and the values were compared between the two populations of H. sericeus. The species collected in September 2010 were H. germanus, H. micans, and H. sericeus. H. sericeus was dominant, occupying more than 90% of the collecting sites. H. germanus and H. micans were collected in the northern and western part of the cruise track (29–34°N, 141–151°E), and not in the southern and eastern part. The population density of these two species was 9000–150,000/km2 in the first cruise, which took place in summer. On the other hand, H. sericeus was collected throughout the cruise track during that cruise. The population density of H. sericeus was relatively high, at 4000–310,000/km2, in the southern and eastern part of the cruise track (19–29°N, 152°E–165°W). In February and March 2012, only H. sericeus was collected at a density of 17,000–80,000/km2 and only in the eastern and southern part, at 25°–28°N, 169°E–178°W. No Halobates oceanic skaters were found in the western or northern part (30°N and further north, 159°E and further west) during that cruise. The lower limit for the inhabitation of sea surface temperatures appeared to be 27.8 °C or slightly lower for H. germanus and H. micans, but was 22.1 °C or slightly lower for H. sericeus. H. sericeus specimens, mostly adults, that had been collected during the two cruises were used in heat coma experiments. Summer specimens showed significantly higher heat coma temperatures (HCTs) than the winter specimens. This difference in HCTs may be the result of relatively long term temperature acclimation in the summer or winter for the adults that inhabit the temperate and subtropical areas along the cruise tracks between Tokyo and Honolulu in the Pacific Ocean. This temperature plasticity of H. sericeus may be related to the wider latitude area inhabited by this species (main range: 40°N–25°S).

The Lago Sofia conglomerate in southern Chile is a deep-marine gravelly deposit, which is hundreds of meters thick and kilometers wide and extends laterally for more than 100 km, filling the foredeep trough of the Cretaceous Magallanes Basin. For understanding the depositional processes and environments of this gigantic deep-sea conglomerate, detailed analyses on sedimentary facies, architecture and paleoflow patterns were carried out, highlighting the differences between the northern (Lago Pehoe and Lago Goic areas) and southern (Lago Sofia area) parts of the study area. The conglomerate bodies in the northern part occur as relatively thin (< 100 m thick), multiple units intervened by thick mudstone-dominated sequences. They show paleoflows toward ENE and S to SW, displaying a converging drainage pattern. In the southern part, the conglomerate bodies are vertically interconnected and form a thick (> 400 m thick) conglomerate sequence with rare intervening fine-grained deposits. Paleoflows are toward SW. The north-to-south variations are also distinct in sedimentary facies. The conglomerate bodies in the southern part are mainly composed of clast-supported conglomerate with sandy matrix, which is interpreted to be deposited from highly concentrated bedload layers under turbidity currents. Those in the northern part are dominated by matrix- to clast-supported conglomerate with muddy matrix, which is interpreted as the products of composite mass flows comprising a turbidity current, a gravelly hyperconcentrated flow and a mud-rich debris flow. All these characteristics suggest that the Lago Sofia conglomerate was formed in centripetally converging submarine channels, not in centrifugally diverging channels of submarine fans. The tributaries in the north were dominated by mass flows, probably affected by channel-bank failures or basin-marginal slope instability processes. In contrast, the trunk channel in the south was mostly filled by tractive processes, which resulted in the vertical and lateral accretion of gravel bars, deposition of gravel dunes and filling of scours and channels, similar to deposits of terrestrial gravel-bed rivers. The trunk channel developed along the axis of foredeep trough and its confinement within the trough is probably responsible for the thick, interconnected channel fills. The large-scale architecture of the trunk-channel fills shows an eastward offset stacking pattern, suggesting that the channel migrated eastwards most likely due to the uplift of the Andean Cordillera.

SummaryTo quantify the major environmental drivers of stream bacterial population dynamics, we modelled temporal differences in stream bacterial communities to quantify community shifts, including those relating to cyclical seasonal variation and more sporadic bloom events. We applied Illumina MiSeq 16S rRNA bacterial gene sequencing of 892 stream biofilm samples, collected monthly for 36‐months from six streams. The streams were located a maximum of 118 km apart and drained three different catchment types (forest, urban and rural land uses). We identified repeatable seasonal patterns among bacterial taxa, allowing their separation into three ecological groupings, those following linear, bloom/trough and repeated, seasonal trends. Various physicochemical parameters (light, water and air temperature, pH, dissolved oxygen, nutrients) were linked to temporal community changes. Our models indicate that bloom events and seasonal episodes modify biofilm bacterial populations, suggesting that distinct microbial taxa thrive during these events including non‐cyanobacterial community members. These models could aid in determining how temporal environmental changes affect community assembly and guide the selection of appropriate statistical models to capture future community responses to environmental change.

The stomach contents of 1261 striped marlins caught from 2007 to 2010 by the sport-fishing fleet of Cabo San Lucas, Baja California Sur, Mexico, were analysed, taking into account sea surface temperatures estimated using satellite images of the study area and the Oceanic Niño Index (ONI). The analysis allowed the identification of three anomalously cold periods during 2007, 2008 and 2010 and a warm period in 2009. The stomach content results showed 89 different prey items eaten during the study period. Of the specimens captured, 868 (69%) stomachs contained food items. The most important prey items were cephalopods (Dosidicus gigasandArgonautaspp.) and fish (Scomber japonicus,Selar crumenophthalmusandSardinops caeruleus). Despite having a broad trophic spectrum, the striped marlin was classified as a specialist consumer, withBi = 0.03. Based on the diet breadth value and the prey-specific index of relative importance (PSIRI), the jumbo squid,D. gigas, was the main prey species, coinciding with cold periods. On the other hand, the fishesS. caeruleusandS. japonicusshowed the highest PSIRI values during the 2009 warm anomalies. Analysis of similarity showed the formation of four groups in relation to PSIRI values. According to a non-metric multidimensional scaling ordination, these groups were formed with a similarity of 30% and a stress of 0.17. These results demonstrate inter-annual variation in the diet as well as in the availability and abundance of prey items.

رودخانه‌ها به عنوان یکی از مهم‌ترین ابزارهای شناسایی حرکات فرایشی یک منطقه شناخته می‌شوند. رشته‌کوه داوران حد فاصل شهرهای زرند و رفسنجان، از سوی شمال محدود به گسل جرجافک است. این گسل با طول 160 کیلومتر به دو صورت قابل ردیابی است، در نیمه شمال باختر با طولی نزدیک به 100 کیلومتر مرز میان کوه و دشت را می‌سازد و در 60 کیلومتر جنوب خاور به‌صورت درون کوهستانی در می‌آید. در نیمه شمال باختر، راندگی واحدهای سنگی پیش از نئوژن به روی واحدهای نئوژن- کواترنر نشان از فعالیت‌های جوان این گسل دارد، در صورتی که هیچ‌گونه اثری از فعالیت لرزه‌ای روی این گسل ثبت نشده است. به منظور بررسی حرکات فرایشی این گسل، مطالعات ریخت‌زمین‌ساختی رودخانه‌های جاری در این رشته‌کوه و منتهی به گسل جرجافک انجام شد. برپایه این مطالعات، مقادیر پیچ‌و‌خم رودخانه برای 21 رودخانه محاسبه و مقدار میانگین 11/1 برای آنها به‌دست آمد که حرکات فرایشی با نرخ کم را برای این گسل به‌دست می دهد. میانگین شاخص شیب رودخانه، برابر 5/165 برای 15 رودخانه اصلی این رشته‌کوه به‌دست آمد که نرخ فرایش کم را برای این گسل تأیید می‌کند. مقادیر شاخص v برای 7 رودخانه مقادیر کمتر از 1 را نشان داده که ناشی از حرکات فرایشی است. با تهیه مقاطع طولی 7 رودخانه یاد‌شده، کوژی نیمرخ‌های یادشده به همراه اثرات دندانه‌ای ناشی از تغییرات سنگ‌شناسی سنگ بستر آشکار شد. به‌گونه‌ای که بالاترین کوژی وابسته به رودخانه شماره 5 است که در میانه نیمه شمالی گسل قرار دارد. از این مطالعات مشخص شد که مقادیر فعالیت فرایشی در پایانه‌های این نیمه، فعالیتی با نرخ کم و در بخش میانی آن و در نزدیکی روستای حصن مقدار بیشتر و تا حد متوسط دارد.