Southeastern Pacific Research Articles

Relationship between water mass characters to Sound velocity profiler (SVP) in the Sulawesi Sea

The Sulawesi Sea is the western entry point of the Indonesian throughflow, which brings water masses from the Pacific Ocean. This study aims to describe the relationship between water mass characteristics and Sound Velocity Profiler (SVP) in the Sulawesi Sea based on Marine Copernicus data from 2022 with a depth of up to 500 meters. Temperature and Salinity data were used to obtain water mass types from the Tpot-S diagram based on Emmery's classification and Sound Velocity Profiler (SVP) based on the Medwin empirical equation. The temperature, salinity, and SVP data were visualized using ODV 5.6.2 software. The data processing results have identified several water mass characteristics that are believed to be influenced by the Eastern North Pacific Central Water (ENPCW) water mass type found at depths ranging from 130 to 318 meters, Western North Pacific Central Water (WNPCW) water mass found at depths ranging from 130 to 500 meters, Eastern South Pacific Central Water (ESPCW) water mass found at depths ranging from 92 to 453 meters, and Western South Pacific Central Water (WSPCW) water mass found at depths ranging from 130 to 500 meters. The ENPCW water mass type on average has a smaller difference in SVP values compared to the WNPCW water mass type. Meanwhile, the ESPCW water mass type on average has a greater difference in SVP values compared to the WSPCW water mass type. The results indicate a positive relationship between temperature and SVP, meaning that the higher the temperature, the higher the SVP. However, there is a negative relationship between salinity and SVP, meaning that the higher the salinity, the lower the SVP.Keywords:Water MassTemperatureSalinitySound VelocitySulawesi Sea

Heterogeneous Diazotroph Communities in the Subtropical‐Subantarctic Transition and Aphotic Zones Off the Coast of Patagonia, Eastern South Pacific Ocean

AbstractSubtropical‐subpolar transition water is a potential domain for N2 fixation, but the understanding of N2 fixation in such waters remains incomplete. We simultaneously examined the N2 fixation activity and community structures of diazotrophs and all prokaryotes from the surface to just above the seafloor off Patagonia in the transitional region of the eastern South Pacific Ocean. N2 fixation activity was not detected in the surface waters, but was observed sporadically and only in subpolar bathypelagic waters (>1,000 m) at very low rates (0.02–0.06 nmol N L−1 d−1). By contrast, the nifH gene, a key gene involved in N2 fixation, was detected widely from the surface to the bottom waters. The majority of diazotrophs were classified as non‐cyanobacterial diazotrophs (NCDs), and the nifH amino acid sequences of major diazotrophs were similar to sequences detected in the Southern Ocean, the aphotic zone and sediment of other oceans, and estuarine waters, suggesting that the NCDs are distributed across diverse marine environments. The overall prokaryotic communities were generally similar to those in other open ocean regions at the phylum level (class level for Proteobacteria) and differed among water depths. Diazotrophs, in contrast, showed vertical and horizontal heterogeneity below the euphotic zone and little association with water depth, indicating a lack of cohesion within the community, which may characterize diazotroph community in the transitional surface water and aphotic zones. Elucidating this community heterogeneity may provide pivotal information about N2 fixation in these waters.

Proposal of Brotulella n. gen. for Monogeneans from the Gills of the Pacific Bearded Brotula Brotula clarkae Hubbs, 1944 (Ophidiiformes: Ophidiidae) Based on Morphological and Molecular Evidence

Based on morphological and molecular data, Brotulella n. gen. is proposed to accommodate the dactylogyrid monogeneans Brotulella laurafernandae n. sp. (type species) and Brotulella luisahelenae n. sp. on the gill filaments of the Pacific bearded brotula Brotula clarkae Hubbs, 1944 (Ophidiiformes: Ophidiidae) from Puerto Pizarro in the Tumbes region (northern Peru). Species of the new genus are distinguished from all other dactylogyrids by the combination of the following features: (1) anchors with a stocking-shaped sheath associated with the distal end of superficial and deep roots, (2) tandem gonads, (3) a vas deferens looping left intestinal caecum, (4) a distally twisted male copulatory organ (MCO) with a delicate membranous accessory piece articulated to the shaft of the MCO, (5) a U-shaped ovary, (6) an almost sigmoid seminal vesicle, and (7) two prostatic reservoirs with thick muscular walls. A 28S ribosomal DNA-based phylogenetic analysis (Maximum likelihood and Bayesian inference) of sequences of two new species of Brotulella n. gen. from the Southeastern Pacific Ocean, along with sequences from closely related genera of the marine Dactylogyridae, supports the establishment of the new genus for the dactylogyrid parasites on the gills of the Pacific bearded brotula.

Biosecurity baseline for a sustainable development of seaweed aquaculture in Latin America

Seaweed farming worldwide has increased considerably in the last century. Latin America (LATAM) has an enormous potential to contribute within the medium/long term to global seaweed production. However, the seaweed sector is not exempted by risks (e.g. diseases and pests) overall understudied in the region, reason why biosecurity and traceability measurements may be needed to some extent. In this study, policies concerning biosecurity in seaweed aquaculture in Argentina, Brazil, Chile, Colombia, Mexico and Peru were analyzed and classified for different categories. The results suggest that most of LATAM policies tend to focus on prevention measures, especially in ecological biosecurity problems, which are included mostly in general aquaculture legislations. Contrarily, economic and environmental risks are to a lesser extent covered. Furthermore, cryptic ecological aspects associated with farming such as introduction of host for diseases or genetic pollution are often overlooked, and therefore poorly managed. Within LATAM countries, Chile has the highest specificity in seaweed-exclusive legislation, likely associated to recent problems with pests and introduction of exotic species. Overall, there is a lack of information related to biosecurity risks of seaweed aquaculture in LATAM, similar to what had happened to other globally relevant producers in the southeastern Pacific that have experienced serious biosecurity problems in the recent years. Seaweed aquaculture is relatively incipient in LATAM region, but its sustainability as well as the associated food security systems may be at risk, unless new policies make compatible seaweed production and biosecurity practices.

First southeastern Pacific record of Balloon Alfonsin, Beryx mollis Abe, 1959 (Beryciformes, Berycidae), with notes on geographical meristic variations

Four specimens (151–156 mm in standard length) of Beryx mollis Abe, 1959 were collected from the Nazca Ridge, southeastern Pacific Ocean. These specimens represent the first record of the species from the south-eastern Pacific Ocean and extend the distributional range of the species eastward by ca. 10,000 km from New Caledonia, the previously known eastern limit. Comparison with specimens from other regions reveals geographical variations of some meristic characters in the species.

Nonlinear time series analysis of coastal temperatures and El Niño–Southern Oscillation events in the eastern South Pacific

Abstract. We carry out a nonlinear time series analysis motivated by dynamical systems theory to investigate the links between temperatures on the eastern South Pacific coast, influenced by the Humboldt Current System, and El Niño–Southern Oscillation (ENSO) events. To this aim, we use a set of 16 oceanic and atmospheric temperature time series from Chilean coastal stations distributed between 18 and 45∘ S. The spectral analysis indicates periodicities that can be related to both internal and external forcing, involving not only ENSO, but also the Pacific Decadal Oscillation, the Southern Annual Mode, the Quasi-Biennial Oscillation and the lunar nodal cycle. The asymptotic neural network test for chaos based on the largest global Lyapunov exponent indicates that the temperature dynamics along the Chilean coast is not chaotic. We use local Lyapunov exponents to characterize the short-term stability of the series. Using a cross-entropy test, we find that two stations in northern Chile, one oceanic (Iquique) and one atmospheric (Arica), present a significant positive cross-dependence between local Lyapunov exponents and ENSO. Iquique is the station that presents the greater number of regional characteristics and correlates with ENSO differently from the rest. The unique large-scale study area, combined with time series from hitherto unused sources (Chilean naval records), reveals the nonlinear dynamics of climate variability in Chile.

Subseasonal Variation Characteristics of Low-Cloud Fraction in Southeastern and Northwestern North Pacific

The subseasonal variability of the low-cloud fraction (LCF) over the southeastern North Pacific (SENP) and northwestern North Pacific (NWNP) was studied using satellite observations and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis. It is found that subseasonal variability of the LCF was closely related to variations in the estimated inversion strength (EIS), sea surface wind speed (SSW), sensible heat flux (SHF), sea surface temperature (SST), surface temperature advection (Tadv), relative humidity (RH), surface level pressure (SLP) and surface air temperature (SAT). An increase in the LCF over the SENP is associated with the development of an anomalous anticyclonic circulation, which is located on the west coast of America. The cold advection, together with the subsidence warming associated with the anticyclonic circulation, strengthens the temperature inversion, favoring the development of the LCF. In the NWNP, the maximum LCF anomaly was also correlated with the stable boundary layer. The southerly wind blows airflow over the Kuroshio Extension from the subtropics, which brings warm and moist air. When air flows to the colder sea surface, it is cooled and condensed by the intensified heat exchange. A lead-lag composite analysis indicates that the mechanisms are different between the SENP and the NWNP, possibly due to the different types of low-level clouds over these two regions. In the SENP, the trade cumulus dominates under a strong capping inversion over the subtropics, whereas fog and stratus often occur under a shallow capping inversion in the NWNP. The effects of atmospheric circulation are also discussed.

Evaluating the contribution of hydrothermal fluids and clay minerals to the enrichment of rare earth elements and yttrium (REY) in deep-sea sediments

Deep-sea REY-rich sediments have attracted considerable attention in recent studies because of their extremely high REY resource potential. Previous studies highlighted that hydrothermal precipitates (e.g., Fe-Mn (oxyhydr)oxides) have played an important role in REY enrichment in deep-sea sediments by scavenging REY from seawater. However, the exact extent of the contribution of hydrothermal scavenging to the REY accumulation has not yet been evaluated. In addition, REY enrichment generally occurred in the pelagic clays, and whether the clays have played a role in the REY accumulation is poorly constrained. We studied bulk-sediment geochemistry and mineral fractions of sediments from two sites in the Eastern South Pacific Ocean. The results show that both cores contain REY-rich sediments layers possessing average ΣREY contents of 989 ppm and 1563 ppm, respectively. The calculated REY resource amounts in the 1 km × 1 km × optimal recovery depth (m) of the two sites are summed to 4690 t-REO. Carbonate compensation depth is one of the factors controlling the REY contents in the sediments in our study area. The shale-normalized REY patterns and calculated simulation results suggest that direct input of REY from the hydrothermal sources to the sediments was not significant. The evaluation of the contributions of REY scavenged by hydrothermal Fe-Mn (oxyhydr)oxides suggests that for the metalliferous sediments in which Fe-Mn (oxyhydr)oxides are hydrothermal-dominated, the Fe2O3 and ΣREY contents show a pronounced positive correlation for all cores, implying hydrothermal scavenging of REY significantly contributed to the accumulation of REY. However, with the continuous addition of hydrothermal Fe-Mn (oxyhydr)oxides in the pelagic clay sediments, the ΣREY contents in the REY-rich sediments firstly exhibited an increase, and then when the total Fe2O3 components achieved a certain value (∼25 wt% in this study) they started to decline. This finding suggests the appropriate input of hydrothermal Fe-Mn (oxyhydr)oxides into the sediments certainly increases the ΣREY contents through a scavenging mechanism, but that excessive addition of them would, in turn, decrease the ΣREY contents of the sediments. Additionally, the amount of clay minerals exhibited a significant positive correlation with ΣREY contents, therefore, we inferred that clay minerals probably played an important role in REY accumulation in the sediments.

Peruvian nudibranchs (Mollusca, Gastropoda, Heterobranchia): an updated literature review-based list of species.

Nudibranchs, as a group, have received limited attention in terms of scientific study along the coastline of Peru. Here, an updated and comprehensive list of nudibranch species found in the Peruvian sea is presented, compiled through an extensive review of relevant literature. This compilation encompasses a total of 31 species, classified into two suborders, 10 superfamilies, 20 families, and 28 genera. With respect to the biogeographic provinces along the Peruvian coast, 23 species inhabit the Warm Temperate Southeastern Pacific province, 18 species occur in the Tropical Eastern Pacific province, and 10 species are found in both provinces, crossing the transitional zone between them. In terms of distribution patterns, two species exhibit a cosmopolitan distribution (Glaucusatlanticus and Fionapinnata), while two species display a circumtropical distribution (Cephalopygetrematoides and Phylliroebucephala). One species exhibits a bipolar distribution in the Eastern Pacific and possesses an amphi-South American distribution (Rostangapulchra). Additionally, six species exhibit an amphi-South American distribution (Rostangapulchra, Diaululapunctuolata, Dotouva, Tyrinnaevelinae, Tyrinnadelicata, and Dorisfontainii), and two species are endemic to Peru (Corambemancorensis and Felimaresechurana). This study provides comprehensive information on biogeographical aspects, geographical distributions, and taxonomic updates within the nudibranch species documented in Peru. Furthermore, we discuss the status of species listed in previous literature that have not been confirmed by collections, referring to them as potentially occurring species.

Observed Interannual Relationship between ITCZ Position and Tropical Cyclone Frequency

Abstract There are no well-accepted mechanisms that can explain the annual frequency of tropical cyclones (TCs) both globally and in individual ocean basins. Recent studies using idealized models showed that the climatological frequency of TC genesis (TCG) is proportional to the Coriolis parameter associated with the intertropical convergence zone (ITCZ) position. In this study, we investigate the effect of the ITCZ position on TCG on the interannual time scale using observations over 1979–2020. Our results show that the TCG frequency is significantly correlated with the ITCZ position in the North Atlantic (NA) and western North Pacific (WNP), with more TCG events in years when the ITCZ is farther poleward. The ITCZ–TCG relationship in NA is dominated by TCG events in the tropics (0°–20°N), while the relationship in WNP is due to TCs formed in the east sector (140°E–180°). We further confirmed that ENSO has little effect on the ITCZ–TCG relationship despite the fact that it can affect the ITCZ position and TCG frequency separately. In NA and WNP, a poleward shift of ITCZ is significantly associated with large-scale environment changes favoring TCG in the main development region (MDR). However, the basinwide TCG frequency has a weak relationship with the ITCZ in other ocean basins. We showed that a poleward ITCZ in the eastern North Pacific and South Pacific favors TCG on the poleward flank of the MDR, while it suppresses TCG on the equatorward flank, leading to insignificant change in the basinwide TCG frequency. In the south Indian Ocean, the ITCZ position has weak effect on TCG frequency due to the mixed influences of environmental conditions.

Cloud Properties of Cold Fronts Affecting Central Chile: Low and High Freezing Level Storms

AbstractThis study analyzes the cloud properties associated with cold fronts that affected central Chile during May–September 1998–2014 using observational and reanalysis data. Warmer, moister, and more unstable conditions in early winter favor the development of deeper mixed‐phased clouds in cold fronts, having larger rain and ice water contents. Late in the season, cooler, drier, and more stable conditions predominate, favoring the development of a larger percentage of shallower warm‐phased clouds. Years when cold fronts show large environmental humidity and high cloud tops were associated with stronger systems that produced the largest precipitation. The linear positive relationship between cloud tops and precipitable water reported in the Central and Eastern Pacific was also found in storms developing in the Eastern South Pacific. The intensity of cold fronts also determines their cloud development and observed rainfall. High freezing level (FL) cold fronts are more frequent in May and June, generally occur in very high humidity environments, are stronger, include more rain and ice water contents, and allow the development of the highest clouds compared to low FL storms, which are more frequent in August. The strength of low FL storms, instead of their available humidity seems to be the key factor controlling the rain they produce. On the other hand, the intensity of high FL storms seems not to be a decisive factor in controlling its rainfall. Finally, the presence of an atmospheric river seems not to guarantee the rainiest events among high and low FL cold fronts.

Chloeia rozbaczyloi, a new species of polychaete (Archinominae: Amphinomidae) and first record of the family for the Nazca Ridge, southeastern Pacific Ocean

The amphinomid polychaete Chloeia rozbaczyloi sp. nov., collected from seamounts of the Nazca Ridge (NR), northwest of Desventuradas islands, southeastern Pacific Ocean, is described. The new species was observed on only two of seven seamounts surveyed in the area (25.079°S, 82.006°W, and 25.408°S, 81.769°W, ∼220 m depth), being abundant on one of them.Specimens were observed under optical and scanning electron microscopes, and DNA was sequenced (COI, 16S, 18S, and 28S nucleotide alignment). Chloeia rozbaczyloi sp. nov. belongs to the venusta group of Chloeia and is distinguished mainly by: (i) the chromatic pattern of the dorsum (with a single middorsal dark band) and the caruncle (with 16–20 vertical folds and 12 to 14 black spots posteriorly decreasing in diameter), (ii) by the bi-annulated dorsum of the first ten chaetigers, each with a bean-shaped anterior pseudosegment, (iii) long neuropodial cirri, with a short ceratophore, at chaetiger 2 and reaching chaetiger 6, and (iv) bipinnate branchiae from chaetiger 4, with seven to nine lateral branches arising from the primary axis, each possing five pinnules; branchiae change progressively in size to the posterior end. The ciliated margin of the accessory dorsal cirri suggests a respiratory function that might be relevant considering that both seamounts in which the species was observed could be influenced by low-oxygen waters. DNA results further support that C. rozbaczyloi sp. nov. differs from the other five congeneric taxa (C. bimaculata, C. flava, C. parva, C. pocicola, and C. viridis) for which genetic information is available.This finding constitutes the first report of the genus for Chilean waters, increasing the number of species of Amphinomidae in this area to seven. It also confirms the presence of the family in the NR and increases the number of Chloeia species in the world to 43.The seamounts where the new species have been collected are within the newly created offshore Nazca-Desventuradas Marine Park. Information on potentially unique and endemic species, such as the one discussed here, is of utmost importance to preserve special ecological units, address ecosystem services, and implement management measures in the area.

Artificial Light at Night (ALAN) causes size-dependent effects on intertidal fish decision-making

Artificial Light at Night (ALAN) alters cycles of day and night, potentially modifying species' behavior. We assessed whether exposure to ALAN influences decision-making (directional swimming) in an intertidal rockfish (Girella laevisifrons) from the Southeastern Pacific. Using a Y-maze, we examined if exposure to ALAN or natural day/night conditions for one week affected the number of visits and time spent in three Y-maze compartments: dark and lit arms (“safe” and “risky” conditions, respectively) and a neutral “non-decision” area. The results showed that fish maintained in natural day/night conditions visited and spent more time in the dark arm, regardless of size. Instead, fish exposed to ALAN visited and spent more time in the non-decision area and their response was size-dependent. Hence, prior ALAN exposure seemed to disorient or reduce the ability of rock fish to choose dark conditions, deemed the safest for small fish facing predators or other potential threats.

Using DNA barcoding to link cystacanths and adults of the acanthocephalan Corynosoma australe of the Southeastern Pacific Ocean (off Peru coast).

The objective of this study is to use DNA barcoding to link cystacanths and adults belonging to the acanthocephalans Corynosoma australe found in the Southeastern Pacific Ocean off the coast central from Peru. We sampled three species of commercial fish (Paralichthys adspersus (Steindachner), Paralabrax humeralis (Valenciennes), and Cheilodactylus variegatus (Valenciennes)) and two South American sea lions, Otaria byronia, stranded on the beaches of the city of Huacho and Barranca, Lima province. A total of 509 acanthocephalan larvae were found in the body cavity of 95 fish (prevalence 54.28%, total mean intensity 8.64). A total of 127 adult worms were found in the large intestine from two South American sea lions (P= 100%, MI= 63.5). A total of 203 larvae from P. humeralis were isolates (P=65.71%; MI= 8.83; MA=5.8), 235 (P=54.29%; MI= 12.37; MA= 6.71) from C. variegatus, and 71 (P=42.86%; MI= 4.73; MA= 2.03) from P. adspersus. All adult and larval specimens were morphologically identified as C. australe. They were generated cytochrome c oxidase subunit 1 (cox1) gene sequences of specimens and were compared with available data from GenBank. Molecular phylogenetic analysis supported our morphological identification, where the Peruvian isolates formed a clade with other isolates of C. australe from other countries of the American continent. Of the sequences obtained, two haplotypes were detected and were not identical with previous reports. Based on both DNA barcoding and morphological analyses, our finding represents the first molecular data of C. australe from Peru and the report of Cheilodactylus variegatus as a new paratenic host on the central coast, extending the knowledge and distribution range of this acanthocephalan in Southeastern Pacific Ocean.

Trophic chain of the pelagic thresher, Alopias pelagicus, in the Southeastern Pacific Ocean: An approach through stable isotopes of carbon and nitrogen

The pelagic thresher, Alopias pelagicus, plays a vital role in coastal and marine ecosystems as a top predator that feeds on species from low trophic levels. It is a commercial species relevant in Ecuador. The feeding chain of A. pelagicus was analyzed through carbon and nitrogen stable isotopes in the Southeast Pacific Ocean. Considering the lack of studies regarding this topic, this would elucidate the flow of nutrients and energy from the base up to this predator. Its diet composition included 19 prey species, out of which 10 were cephalopods and nine Osteichthyes. The most relevant species were the squid Ommastrephes bartramii, Dosidicus gigas, Stenoteuthis oualaniensis, and the fish Merluccius gayi peruanus. The pelagic thresher is a carnivore predator, and its prey species belong to tertiary and quaternary trophic levels. The carbon and nitrogen male isotopic ratios were similar to those of females, as were immature and mature organisms. This suggests that this species feeds in oceanic regions of low depths and could be exploiting and sharing an area with similar feeding resources. According to the mixing models, squids were the most important prey group, in which the squid Ommastrephes bartramii contributed most to its diet. Furthermore, this shark was characterized as a specialist predator with a trophic overlap by sex and maturity stages.

Temporal and inter-individual changes in the integrated biochemical condition of the gonads of female swordfish (Xiphias gladius) from the Southeastern Pacific Ocean.

The integrated biochemical condition (IBC) of gonads is closely related to the reproductive success of highly migratory marine species. The IBC of gonads can be influenced not only by size and/or age, but also by environmental conditions. Here, female swordfish, Xiphias gladius, that migrate to temperate regions with a marked seasonality (e.g., the Southeastern Pacific Ocean, SEPO) were compared in relation to the IBCs (lipids, proteins, glucose and, fatty acid profiles) of their gonads; individuals with two body size ranges and distinct degrees of sexual maturity were evaluated, and considered as: small and/or virginal (SV: <170 cm lower jaw fork-length (LJFL), oocyte size (OS) <0.08 mm) vs large and/or maturing females (LM: >190 cm LJFL, OS >0.133 mm). This comparison was conducted in two environmentally contrasting seasons (winter vs spring). Our results showed that the gonadosomatic index (GSI) was significantly higher in LM than SV. Lipid contents varied significantly between seasons and body sizes. The highest lipid concentrations were recorded in the spring in large females. No significant differences were found when comparing the protein and glucose contents of the two evaluated seasons or body size ranges of the studied females. In turn, the fatty acid (FA) profiles of female gonads significantly varied for both seasons and body size ranges. A high content of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) and poly-unsaturated fatty acids (PUFAs) were recorded in female gonads in the spring. The SFAs C16:0 and C18:0, the MUFA C18:1n9, and the essential PUFA C22:6n3 were the main contributors to the observed differences between spring and winter. These results could be used as indicators of the nutritional condition and health status of swordfish individuals. Hence, the IBC of female swordfish gonads have great potential to aid in estimating survival rates and stock abundances of this species. The integration of this information constitutes an asset in fishery management models with an ecosystem approach.

Performance of GPCP Daily Products Over Oceans: Evaluation Using Passive Aquatic Listeners

AbstractPassive Aquatic Listeners (PALs) have been increasingly deployed to collect minute‐scale surface oceanic rainfall and wind information, with a sampling area similar to the spaceborne sensor footprints. This provides an unprecedented opportunity to validate satellite precipitation products over oceans. This study evaluates the Global Precipitation Climatology Project (GPCP) daily products, including the widely used GPCP v1.3 and the newly released GPCP v3.2, over oceans using 58 PALs as references. The study shows that the GPCP performance depends on time scale, region, and rainfall intensity. The two versions of GPCP perform similarly at multi‐year and monthly scales, while GPCP v3.2 shows substantial improvements in representing rain occurrence and rain intensity at daily scale. The results also highlight the challenge of precipitation measurement over certain regions such as the tropical Southeastern Pacific and extratropical North Pacific, where both versions of the GPCP products perform similarly but exhibit noticeable differences compared to PAL observations.

Biochemical-ecological composition and bio-stoichiometric ratios of swordfish (Xiphias gladius) gonads in the Southeastern Pacific Ocean

Swordfish (Xiphias gladius), a highly migratory fishery resource of great importance in the Southeastern Pacific Ocean (SEPO), is a species with late sexual maturation, high longevity, and a large body size that spawns and reproduces several times throughout its adulthood. In the present study, we hypothesized that the Biochemical-Ecological Composition (BEC) of the gonad (measured as the lipid, protein, glucose, and energy contents) and its bio-stoichiometric ratios (lipid/protein: L/P; lipid/ glucose: L/G) would be influenced by both female body size (lower jaw fork length in cm, LJFL: <180, 180–260, >260) and time (trimesters: 1,2,3; years: 2017, 2019). Our results revealed that in relation to their body size, female swordfish gonads varied significantly in their BEC, but not in their L/P and L/G ratios during their quarterly development within an annual cycle. These variations in the BEC were noticeable in females of medium (180–260) and larger (>260) sizes. Particularly, as the year progressed, females stored significant amounts of energy during their trophic migration, made evident by the increase in the lipid and protein contents of the gonads, which reached maximum levels towards the end of the year, during the second and third trimesters. These high energy reserves can be used for the reproduction during the last trimester of the year (i.e. austral spring–summer), when the warm temperature and high productivity in the SEPO are optimal for the successful development of oocytes. Future studies considering an ecosystem approach should analyze the classes of lipids and types of fatty acids that are involved in the reproduction of this species, and how they are acquired through the consumption of lipid-rich prey, and subsequently metabolized to be used in reproduction and during early ontogeny.

Towards an estimate of the Southeastern Pacific humpback whale stock

Between 1991 and 1997 a photo-identification study of Southeastern Pacific humpback whales was carried out on the central coast of Ecuador (1°26’S, 80°50’W), South America. During this period, a total of 219 whales were identified and catalogued by the colouration pattern on the ventral side of their flukes. Naturally marked whales were used to estimate the population through the Petersen’s mark-recapture method as modified by Bailey. With data from the final two seasons (1996-1997), the resultant estimate was 1,922 (95% CI = 77-3,767) whales. Pooling data from the first six years resulted in an estimate of 2,683 (95% CI = 397-4,969) whales. Sources of bias relate to violations of the assumptions of closure and equal catchability conditions. The low inter-yearly resighting rate and a high rate of new discoveries in the last season indicate that only a fraction of the population has so far been identified. Despite the broad confidence interval, these data provide an indication of the current number of whales.

Interannual variation of the onset of the Tibetan Plateau rainy season and its relationship with the sea surface temperature in the North Pacific

AbstractThe onset of the Tibetan Plateau rainy season (OTPRS) marks the transition from dry season to wet season in situ, which has a great impact on the water cycle and atmospheric heating in extensive areas. This analysis found that the earlier OTPRS is controlled by the weakened westerly wind, a dipole vortex pair with an anomalous anti‐cyclone over Lake Baikal but an anomalous cyclone over the Tibetan Plateau, the intensified southerly water vapour transportation on the southern edge of the Tibetan Plateau, the active convection and the increased humidity over the Tibetan Plateau in spring. And the opposite circulation anomalies correspond to the later OTPRS. The interannual variation in the OTPRS is closely related to sea surface temperature anomalies (SSTA) in the North Pacific in the previous winter, with the opposite phase between the ‘tongue’ extending eastward from the China East Sea and the surrounding ‘semi‐circle’ in the east. This pattern features the third leading mode of the winter SSTA in the North Pacific and can persist to spring. The vertical motion, convergence and divergence associated with the direct thermal effect from the significant SSTA centres in the southeastern and northwestern North Pacific form two opposite zonal circulation circles along 30°N. The zonal circulation circles bridge the SSTA in the North Pacific and the circulation anomalies over the Tibetan Plateau and have a delayed impact on convection over the Tibetan Plateau, thereby affecting the OTPRS.