Patagonian grenadier (Macruronus magellanicus) is widely distributed around the austral zone of South America. Contrary to the South Atlantic, a large number of eggs and larvae have been observed in the Chilean Patagonia. The spatial and temporal stability of these spawning areas, however, has not been confirmed, nor have their environmental features been detailed. To characterize the spawning and nursery areas of M. magellanicus, we analyzed zooplankton samples and hydrographic data collected during winter and spring in the inner sea (inshore) and its adjacent continental shelf (offshore) of the Chilean Patagonia between 1995 and 2019. The results indicate that northern Chilean Patagonia is a key spawning and nursery area for this species. Peak spawning occurs in winter, most eggs are found offshore, and secondarily inshore, between 44°-46°S, whereas toward southern Patagonia, the limited spawning observed appears to occur within the inshore zone areas. A fraction of the spawn located offshore in the northern Patagonia enters the inshore areas and, as their larvae grow, they return to the offshore zone. A linear relationship was found between salinity and egg abundance, coinciding with a deeper vertical distribution, whereas a non-linear (dome-shaped) effect of temperature on larval abundance indicated a wider spatial distribution. Overall, both egg and larval abundances declined over the 25-year study period.

Key aspects of the trophic ecology of small pelagic fishes are not fully understood along the Humboldt Current. Here we examined the trophic seasonal dynamics, their relationships with oceanographic conditions, and interactions among cohabiting species (anchoveta Engraulis ringens and common sardine Strangomera bentincki) in the central (20 degrees S) and southern (36 degrees S) Humboldt Current System (HCS), using stable isotopes (delta 13C, delta 15N) measured at different levels of the food web (particulate organic matter, copepods, and fish). Anchoveta showed narrow delta 13C seasonal variations in both zones but marked differences between zones. A wider inter-seasonal range in delta 15N values, and a wider trophic amplitude (size of the isotopic niche) were observed in anchovies from the central HCS zone. In the southern HCS, the trophic positions (TPs) of both species showed slight variation during the year (anchoveta: 3.15-3.43, common sardine: 3.08-3.28), with those of common sardine slightly lower than those of anchoveta. However, the isotopic niche size in both species changed seasonally, as did the trophic overlap between them. The lowest trophic overlap between species occurred in winter, suggesting a trophic partitioning mechanism to overcome periods of reduced food availability. Overall, the seasonal variation in stable isotopes in the components of the food web seem closely associated with large-scale atmospheric and oceanographic processes (coastal upwelling) that affect both areas but with different intensity and duration during the year. Local geographic differences between zones also influence the input of organic carbon and nitrogen from certain sources, and interactions between species become significant during specific seasons.

The Northern Patagonia Estuarine Zone (NPEZ) of Chile, characterized by its complex geography and natural physical barriers, plays a crucial role in the spatial dynamics of small pelagic fish (SPF) spawning. This study was aimed at evaluating the non-stationary (barrier) spatial structure of spawning of three SPF species: anchoveta (Engraulis ringens), common sardine (Strangomera bentincki), and southern sardine (Sprattus fuegensis) in the NPEZ. Non-stationary barrier models explicitly treat coastlines, islands, and archipelagos as physical barriers that interrupt spatial autocorrelation across land, in contrast with conventional stationary, isotropic geostatistical models that assume spatial dependence is uniform in all directions. Egg count data from 128 systematically distributed stations during the 2014 spawning season were analyzed using non-stationary spatial models fitted with the Integrated Nested Laplace Approximation. Two models were compared: one assuming correlated realizations among species (M1) and another assuming independent realizations (M2). Model M2 showed better performance based on the Watanabe–Akaike Information Criterion and Deviance Information Criterion, indicating that the spawning of the three species tends to be spatially segregated. The results revealed that physical barriers significantly influenced the spatial distribution of spawning, with anchoveta concentrated near freshwater-influenced areas, common sardine in coastal areas with high topographic heterogeneity, and southern sardine in eastern coastal and central areas in the NPEZ. The spatial segregation observed in this study has important ecological and management implications, highlighting the need to consider habitat heterogeneity and the spatial dynamics of spawning when designing conservation and fishery management strategies in the NPEZ, such as delimiting species-specific, seasonally restricted spawning closures around key barrier-associated habitats (e.g., river mouths, sheltered bays, and channels).

Zooplankton are a key component of food webs in upwelling systems. Their distribution is influenced not only by mesoscale and climate dynamics but also by topography and local currents. Submarine canyons that incise the continental shelf can act as conduits, transporting deep, nutrient-rich waters to shallower regions and promoting coastal biological productivity. Consequently, these canyons facilitate the advection and accumulation of zooplankton. We aimed to describe the spatio-temporal variability in zooplankton distribution (using net samples and acoustic data) and their association with local currents in a long, narrow submarine canyon located in the highly productive continental shelf off central Chile. The backscattering strength (Sv), a proxy for zooplankton biomass, was highly variable on both diurnal and spatial scales. Higher Sv and abundances were found at night, following the classic diel vertical migration pattern. Zooplankton were not uniformly distributed within the canyon. In the surface and mid-depth layers, the canyon walls accumulated more zooplankton than the center, particularly during the nighttime. Within the canyon, the currents were asymmetrical and frequently reversed direction. When the positive along-canyon current was stronger on the northern slope, Sv was also higher on that wall. This pattern was especially evident in the section closer to the canyon head. We show that the Biobio Canyon is a highly dynamic environment where oceanographic conditions can rapidly shift. Our findings suggest a feasible mechanism for zooplankton retention driven mainly by along-canyon flow asymmetry and vertical migrations.

Using hydrographic and zooplankton sampling along with stable isotope analyses, we determined the influence of freshwater input and of oceanic water ingress at the Golfo de Penas to the Baker Channel (47°S), central Patagonia, on the zooplankton community during mid-spring. Our results show that different taxonomic and functional groups occurred within the mesozooplankton community along an offshore-inshore-oriented transect. Some groups occurred mostly offshore (i.e. euphausiids, fish larvae, stomatopods, amphipods), while others occurred in higher abundance inshore (i.e. medusae, chaetognaths, siphonophores, ostracods). Early life stages of ecologically key species, such as Euphausia vallentini and pelagic stages of Munida gregaria, occurred mostly at the Golfo de Penas. Higher trophic positions estimated from δ15N occurred in mesozooplankton groups inshore (Baker Channel) and lower at the Golfo de Penas, coinciding with the decrease in C:N ratio in zooplankton and with an increase in chlorophyll-a values in the seawater seawards. The δ13C distribution in the zooplankton groups along the offshore-inshore transect showed a positive gradient from the inshore most stations towards the Baker Channel mouth, suggesting a negative relationship with freshwater carrying terrestrial organic carbon and a positive relationship with seawater. However, from the channel mouth seawards, a decrease in δ13C in most zooplankton groups occurred. Within the Baker Channel, low δ13C values occurred in particulate organic matter (POM) at the surface layer, higher values at intermediate depths, and low values at the deepest zones. This uneven distribution of δ13C values in POM and zooplankton, along with the presence of different water masses at different depths suggest an along-basin transport of organic carbon of different sources at different layers: of terrestrial origin at surface, marine origin at mid depth, and from degraded organic matter from offshore entering at higher depths. Thus, a complex scenario of lateral transport of water of different characteristics modulates the presence of zooplankton in different locations and their food sources along the area. These findings resemble others observed in further south in the Beagle Channel (57°S) also in spring but the relative contribution of different carbon sources may differ between Patagonian systems.

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The effect of the combination of marine toxins produced by algal blooms, in conjunction with varying environmental characteristics on organisms in the water column, is a poorly explored research field. Pelagic fish species of commercial importance, such as anchoveta (Engraulis ringens) in central Chile, may be exposed to these combined factors in a climate change scenario. This is observed from documented changes in the length of the upwelling season, frequency of upwelling events, and the increased frequency of atmospheric rivers affecting the southern spawning zone of this species. This study evaluated the integrity of hair cells in neuromasts, mechanosensory organs present in fish larvae, under exposure to different combinations of the algal bloom-produced okadaic acid OA (1 ng mL−1), and two temperature (12 and 14°C), and salinity treatments (historically more frequent: 34 PSU- 12°C; expected: 32 PSU - 14°C). Viable hair cells were counted in newly hatched larvae from the Biobío region, central Chile. Results showed a significant decrease in the average number of viable hair cells per neuromast (from 6.1 ± 1.6 to 4.0 ± 1.2) under lower salinity treatments (32 PSU) compared to normal conditions. Additionally, a seasonal trend was observed with fewer viable cells (from 7.4 ± 1.2 to 4.4 ± 1.1) as the fish species’ reproductive period progressed. The combined effect of OA exposure and modifications with the environmental factors also resulted in a significant decrease of up to 70% in the number of viable hair cells in larvae exposed to OA and high temperatures, indicating damage influenced by the toxin along with a synergistic and/or additive role of temperature. These findings reveal how the lipophilic toxin okadaic acid, produced by harmful algal blooms, interacts with abiotic environmental factors affecting coastal ecologically and socio-economically important organisms. This emphasizes the need to consider multiple factors when studying the effects of marine toxins.

Patagonian grenadier migrates from the southwest Atlantic and southeast Pacific to reproduce in the northern Chilean Patagonia. Spawning occurs mainly in winter at the continental shelf break (CSB), but eggs and larvae are also collected inshore of the Chilean Patagonian Estuarine System (PES) during winter and spring. In order to evaluate whether the ontogenetic changes in distribution of early life stages was part of the reproductive strategy of Patagonian grenadier, we analyzed the distribution and transport of eggs and larvae in spring and winter in three channels of the PES (Ninualac, Darwin and Pulluche channels). Ichthyoplankton stratified sampling showed the highest abundances of eggs in the deepest strata, whereas larvae were heterogeneously distributed along the entire water column. Residual current velocities obtained from ADCP indicated seaward (westward) fluxes at the surface in all channels, except in Pulluche in winter. At depth (50-100 m) fluxes were eastward (inshore) in the northern 2 channels but seaward in the southernmost channel. These differences in residual velocities, with variations in the distribution of eggs and larvae, resulted in different landward and oceanward flows of eggs and larvae among channels and strata. Estimated net fluxes in winter suggested that eggs within the channels would either enter the PES from the continental shelf, mainly at the subsurface layer of the Darwin channel, or come from a secondary spawning within this same channel. Eggs and small larvae would be retained at the inshore zone of the Darwin channel, and the more advanced developed stages would be exported through the Pulluche channel back to the continental shelf. The inshore high abundance of eggs and larvae of M. magellanicus in winter, along with the reduced primary production and microbial-based plankton community previously reported, suggest that entering the channels in winter is not a major part of the reproductive strategy of the species. The exportation of larvae from the channels to the shelf in winter, instead, might promote better feeding conditions in offshore waters where larger zooplankton occurs.

This study aimed to characterize the energy density (ED), using a micro-bomb calorimeter, of different plankton fractions: microplankton (23-67 mu m; including phytoplankton and small heterotrophs), microzooplankton (67-200 mu m), mesozooplankton (200-2000 mu m), and fish larvae, at two micro-basins separated by a sill (the Mackinlay Strait) and with different topography and hydrography in the Beagle Channel. For that purpose, two sampling sites (west (F1) and east (F2) of the Mackinlay Strait), two strata (surface and near-bottom layers) and diel variations (diurnal and nocturnal hours) were considered. Also, patterns among plankton fractions' ED and water properties (temperature, salinity, total alkalinity, pH, and dissolved inorganic carbon) were analysed by redundancy analysis. ED values of the plankton fractions differed among sites, strata and sampling time. Surface microplankton at F1 showed higher ED than at F2. A trend of higher ED values of microzooplankton was observed at the surface than at the near-bottom layer of F1, whereas similar values between both layers (surface and near-bottom) were observed at F2. Mesozooplankton was the plankton fraction that most contributed to the site-depth-time of sampling differences in ED. For instance, the ED of mesozooplankton was higher at the near -bottom than the surface layer during diurnal and nocturnal hours of F1, while the opposite was observed for nocturnal hours at F2. ED of microplankton was associated with conditions of lower values of total alkalinity and salinity but higher temperature, whereas microzooplankton was associated with the opposite conditions. The ED of mesozooplankton was associated with conditions of higher pH and diurnal hours. It is proposed that the energy flow patterns of the plankton community in the Beagle Channel differ in the two micro-basins formed by the MacKinlay Strait (east and west of it), with lower and more homogeneous ED values between fractions and layers east of the Strait characterised by depleted-in-nutrients waters.

Off the central-southern Chilean coast (35°–38°S), the Gulf of Arauco is one of Chile's largest semi-enclosed coastal areas. It hosts industrialized activities within a highly productive zone of the Southern Humboldt Current System. One of the principal hydrodynamical forcings of the region is the Biobio River, whose discharge significantly influences coastal dynamics in the Gulf. The present work aims to study the impact of the Biobio River freshwater discharge on the circulation patterns in the Gulf of Arauco, using a high-resolution interannual simulation of the period 2013–2018. The simulation includes monthly interannual discharge from the significant four rivers for the study zone (Mataquito, Maule, Biobío, and Itata). The focus is primarily on wintertime (June–September), the highest freshwater discharges period. The modeled temperature and salinity fields were consistent with in-situ observations, presenting a moderate bias. The water masses highlighted in the TS diagrams, the temperature time series, and especially the currents near the Biobio River mouth were well represented in the simulation. It was found that the Biobio River strongly impacted the circulation in the Gulf of Arauco, intensifying the currents and causing a notable salinity decrease. Offshore zonal currents were intensified west of the Biobio River mouth, whereas southward alongshore currents were enhanced, especially during August. The influence of the Biobio River in the Gulf of Arauco was closely related to discharge strength. A strong relation between predominant southward downwelling-favorable wind stress and meridional currents was found, probably due to the formation of a buoyant coastal current strengthened by the wind-driven current during winter. Finally, surface buoyant waters associated with the river discharge generated a strong baroclinic zonal pressure gradient equilibrating the sheared meridional flow and enhancing the meridional ageostrophic pressure gradient, Reynolds stress, and near-surface vertical mixing of momentum.

High-latitude marine environments, such as the Beagle Channel, are highly vulnerable to modifications related to climate change and anthropogenic impacts, which can rapidly affect the ecological attributes of plankton communities and thus alter ecosystem trophodynamics. This study compares the mesozooplankton community structure in the inner and outer (eastern) Beagle Channel during spring and assesses the interactions of the main mesozooplankton trophic groups with lower and higher trophic level organisms under an isotopic approach. Oceanographic data and biological samples, ranging from sediment and phytoplankton to pelagic squat lobsters (Grimothea gregaria), were collected along the channel during two research cruises conducted in November 2019. Mesozooplankton abundance and taxonomic composition differed between sectors, in agreement with their distinct environmental conditions. The inner sector was dominated by copepods, mainly Clausocalanidae spp., followed by cirripede and echinoderm larvae and appendicularians. In the outer sector, with shallower, saltier, and warmer waters than the inner one, mesozooplankton abundances were notably higher and both copepods and decapod larvae, mainly Peltarion spinosulum and G. gregaria zoeae, were dominant. This pattern in meroplankton abundance was consistent with the bathymetric distribution reported for benthic adults. Betweensector differences in taxonomic composition, e.g., Macruronus novaezelandiae (hake) larvae occurring only in the outer sector, may be attributed to the higher connectivity between this sector and the open ocean and the semi-enclosed character of the inner channel. Mesozooplankton spatial variability was partially reflected in the isotopic niche width of their different trophic groups such as copepods, euphausiids and decapod larvae. However, at the community level, trophic attributes (i.e., baseline resources, trophic positions, isotopic diversity metrics) were quite similar in the two sectors, suggesting similar basal and vertical trophic structures. According to Bayesian stable isotope mixing models, most trophic groups, including pelagic G. gregaria, rely on phytoplankton as their main carbon source. This reveals a weak predation pressure on mesozooplankton by the squat lobster and reinforces a bottom-up regulation during the spring season. This study contributes to our knowledge of trophic interactions in plankton communities and how they are regulated by bottom-up and top-down forces, which is imperative for monitoring and management purposes.

Forage fish play the crucial role of transferring energy from lower to upper trophic levels. These small pelagic fish feed on plankton and can compete with each other for food, leading to potentially complex interactions. Three forage fish species ( Sprattus fuegensis , Strangomera bentincki , and Engraulis ringens ) are commonly found in the inshore waters of Northern Chilean Patagonia, a region with large spatial variability in oceanographic conditions and in the zooplankton community. To better understand what factors may explain coexistence among these three forage fish species, we examined differences in resource availability (zooplankton community and abundances) in three locations (Chiloé, Cordillera, and Aysén regions) within Northern Patagonia. We compared the diet of the three fish species using both stable isotope and stomach content analyses, and we measured their gill rakers. S. fuegensis , the only species found in all three regions, had flexible diets which lent it greater success than the other two species at foraging in waters with fewer prey. We found little diet differentiation among the three species in the copepod-rich Cordillera region, but the diverging diets of S. bentincki and S. fuegensis in the copepod-poor Chiloé region suggest that diet partitioning in areas with fewer resources is due to competition. The small differences in diet facilitates coexistence among the three species, which may help explain the lack of correlation between the three species’ population abundances in the Cordillera region over the past 6 years. Finally, our results show that the high degree of oceanographic heterogeneity in Northern Patagonia may encourage species separation based on their specific environmental requirements.

Zooplankton is the primary production consumer in the aquatic food web in fjords and channels of western Patagonia. In this study, the role of vertically migrating and not-vertically migrating crustacean mesozooplankton (collected in a 300 μm mesh net) as potential consumers of spring phytoplankton was assessed in an inshore gulf of central Patagonia through repeated stratified zooplankton sampling during the day and night, over a 30 h cycle. Results show that while a group of copepods remained close to the surface where chlorophyll-a concentrations were higher, other copepod groups and euphausiids exhibited diel vertical migrations. The maximum depth of migration appeared to be limited by very low oxygen concentrations in the water column (< 0.2 mL O2 L−1). Meanwhile, the abundance of not-migrating copepods (62%) was higher than that of vertically migrating copepods and euphausiids combined (38%). The latter two groups doubled their carbon consumption at night (37.0%) compared to daytime (18.8%) but their contribution continued to be lower than that of not-vertically migrating groups at night (63%). Over the 24 h cycle, the carbon consumption carried out by all vertically migrant groups together accounted for almost one-third (28.8%) of the total daily carbon consumption by the mesozooplankton crustacean community. In most areas surveyed along Patagonia, total community respiration exceeded the estimated gross primary production when autotrophic and microheterotrophic respiration was pooled, suggesting that external subsidies of carbon (e.g., allochthonous, terrestrial) and/or recycling of fecal pellets are required to support the micro- and meso-zooplankton communities of these sub-Antarctic fjord systems.

We report the first record of Siphonops paulensis predation by Burrowing Owl occurred in a Cerrado fragment. In addition to describing the predation event, we discuss the owl's ability to hunt for fossorial species and the presence of poison glands on the amphibian's skin, which can act as a defense against predators.

In habitats impacted by bottom trawling that influences the resilience of few and widely distributed abundant species, it is relevant to analyze how populations are structured according to their niche and niche overlap, and hence contributing to the ecosystem-based management approach. We evaluated and compared the isotopic niche width and determined the isotopic niche overlap for target and bycatch species of crustaceans and demersal fish caught with bottom trawling on the continental shelf and upper slope of the central-southern zone of Chile. Stable isotope analysis relied on carbon and nitrogen isotopes (13C and 15N) and Bayesian statistics of niche size and community metrics. Crustaceans and fish species are structured in three clusters according to the stable isotope values and the Chilean hake Merluccius gayi, which was probably clustered isolated due to its pelagic stable isotope values due to diel vertical migrations associated with feeding on euphausiids in the water column. The first group was constituted by demersal fish, that showed higher δ15N (19‰) and narrower δ13C (−16‰). The two other groups constituted a mix of crustaceans and fish, with access to different carbon sources. There were degrees of specialization for most species within the groups and overlap in the isotopic niche between populations. The benthic and demersal macrofauna species are structured by sharing resources in the habitat, probably on available sources supported by the productive pelagic system.

Marine Mammal ScienceVolume 37, Issue 3 p. 1116-1127 NOTE Prey items of baleen whale species off the coast of Chile from fecal plume analysis Susannah J. Buchan, Corresponding Author Susannah J. Buchan sjbuchan@gmail.com orcid.org/0000-0003-2180-1432 Centro de Estudios Avanzados en Zonas Áridas, Coquimbo, Chile COPAS Sur-Austral Center, Departamento de Oceanografía, Universidad de Concepción, Concepción, Chile Woods Hole Oceanographic Institution, Woods Hole, Massachusetts Correspondence Susannah J. Buchan, Centro de Estudios Avanzados en Zonas Áridas, Raúl Bitrán 1305, La Serena, Chile. Email: sjbuchan@gmail.com Contribution: Conceptualization, Funding acquisition, ​Investigation, Methodology, Resources, Writing - original draft, Writing - review & editingSearch for more papers by this authorPaulina Vásquez, Paulina Vásquez Caliptopis Consultoría Limitada, Santiago, Chile Contribution: Data curation, Formal analysis, Writing - original draft, Writing - review & editingSearch for more papers by this authorCarlos Olavarría, Carlos Olavarría Centro de Estudios Avanzados en Zonas Áridas, Coquimbo, Chile Contribution: Conceptualization, Funding acquisition, Resources, Writing - review & editingSearch for more papers by this authorLeonardo R. Castro, Leonardo R. Castro COPAS Sur-Austral Center, Departamento de Oceanografía, Universidad de Concepción, Concepción, Chile Contribution: Data curation, Methodology, Resources, Supervision, Writing - review & editingSearch for more papers by this author Susannah J. Buchan, Corresponding Author Susannah J. Buchan sjbuchan@gmail.com orcid.org/0000-0003-2180-1432 Centro de Estudios Avanzados en Zonas Áridas, Coquimbo, Chile COPAS Sur-Austral Center, Departamento de Oceanografía, Universidad de Concepción, Concepción, Chile Woods Hole Oceanographic Institution, Woods Hole, Massachusetts Correspondence Susannah J. Buchan, Centro de Estudios Avanzados en Zonas Áridas, Raúl Bitrán 1305, La Serena, Chile. Email: sjbuchan@gmail.com Contribution: Conceptualization, Funding acquisition, ​Investigation, Methodology, Resources, Writing - original draft, Writing - review & editingSearch for more papers by this authorPaulina Vásquez, Paulina Vásquez Caliptopis Consultoría Limitada, Santiago, Chile Contribution: Data curation, Formal analysis, Writing - original draft, Writing - review & editingSearch for more papers by this authorCarlos Olavarría, Carlos Olavarría Centro de Estudios Avanzados en Zonas Áridas, Coquimbo, Chile Contribution: Conceptualization, Funding acquisition, Resources, Writing - review & editingSearch for more papers by this authorLeonardo R. Castro, Leonardo R. Castro COPAS Sur-Austral Center, Departamento de Oceanografía, Universidad de Concepción, Concepción, Chile Contribution: Data curation, Methodology, Resources, Supervision, Writing - review & editingSearch for more papers by this author First published: 27 February 2021 https://doi.org/10.1111/mms.12782 Funding information: Agencia Nacional de Ciencia y Tecnología (ANID), Grant/Award Numbers: R16A10003, PIA AFB170006; Office of Naval Research Global, Grant/Award Number: N00014-17-2606 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume37, Issue3July 2021Pages 1116-1127 RelatedInformation

The Peruvian anchoveta Engraulis ringens is one of the most important commercial fishes along the Humboldt Current. Previous studies have shown that egg quality (volume, protein and lipid content) and hatching rates decrease during the spawning season, from the rainy winter to late spring. In this study, we assessed whether changes in atmospheric condition that led to an intense drought over a decade modified the freshwater river fluxes and seawater salinity at an E. ringens coastal spawning zone off central Chile (36° 30’ S), and determined if changes in salinity affect the hatching-gene expression, hatching-enzyme expression, and hatching success in eggs incubated at a range of salinities (27-35 psu) normally occurring during the reproductive season. Results showed that hatching-enzyme expression increased as the embryo developed. The highest expression of the hatching-enzyme gene and of the enzyme itself, along with hatching success were obtained at the lowest incubating salinity (27 psu). In the field, hatching success decreased from late winter to late spring, the start of the upwelling period at the end of the reproductive season. Thus, variations in salinity of the seawater during the spawning period are coincident with changes in gene expression of the hatching enzyme, the hatching enzyme expression, and hatching success. Spawning late in winter when rainfall is higher and seawater salinity in the coastal area is lower may increase hatching success, a reproductive strategy that might be affected by the observed climate changes and severe drought in central Chile.

In southern Patagonia, the Beagle Channel shows very low production during winter but simultaneously sustains very dense aggregations of the pelagic stage of squat lobster ( Munida gregaria ), a benthic decapod whose pelagic juveniles have the largest body size within the chitinous pelagic community. To assess the coexistence of the mesozooplankton community and the pelagic M. gregaria stage under the harsh feeding winter conditions, we conducted a research cruise at two locations connected to the Beagle Channel, Yendegaia Bay (land terminating-glacier) and Pia Fjord (marine-terminating glacier). Our results showed that the zooplankton communities were similar in these two fjords, that a single pelagic group dominated in terms of biomass (pelagic Munida gregaria ), and that differences in vertical distribution existed between most of the principal crustacean zooplankton and pelagic M. gregaria . All groups showed consumption of terrestrially derived organic matter, as revealed by their δ 13 C values. However, the isotopic composition, trophic positions (TP), and isotopic niche areas of the groups separated pelagic M. gregaria , presenting some of the lowest δ 15 N and the highest δ 13 C values, and the narrowest isotopic niche width. Pelagic M. gregaria was dominated by a single body size class along the 0–100 m water column, with no diel changes in vertical distribution, remained mostly in the upper layers (0–50 m), and benefited from the slightly higher phytoplankton concentrations at shallower depths as revealed by their higher δ 13 C values and low trophic position. In contrast, the other groups, including zoea M. gregaria stages, developed changes in distribution between day and night or remained deeper in the water column. These groups showed higher δ 15 N values, higher TP, and lower δ 13 C values, most of which probably fed on a nanoheterotrophs and terrestrial particulate organic matter mixture at deeper layers. Thus, the different vertical distributions, different trophic level food sources, and slightly different organic carbon sources apparently reduced any potential competence for food resources and form part of the feeding strategy that may facilitate the coexistence of the different large pelagic crustaceans under harsh feeding winter conditions in this high latitude austral region.