Pleuroncodes Planipes Research Articles

Spatial and Temporal Variability of Trace and Macro Elements in the Red Crab Pleuroncodes planipes in the Pacific Coast of the Baja California Peninsula, Mexico.

The red crab, Pleuroncodes planipes, is a decapod crustacean abundant off the Pacific coast of the Baja California Peninsula. This species is caught and used in preparing animal feed, such as flour, particularly for aquaculture. Levels of calcium (Ca), cadmium (Cd), copper (Cu), iron (Fe), lead (Pb), magnesium (Mg), manganese (Mn), nickel (Ni), phosphorus (P), and zinc (Zn) were measured in red crabs collected from three geographic zones during three cruises in different seasons. Significant differences were found in the levels of Ca, Cd, Cu, Fe, Mg, Ni, P, and Zn between the two El Niño years (cruises C1 and C3, based on a threshold of ±0.5 °C for the Oceanic Niño Index). The highest concentrations of most elements were observed in the south of the Baja California Peninsula, a highly productive area influenced by upwelling events. Our findings suggest that while environmental temperature plays a central role in the benthic or pelagic distribution of red crabs, their content and variability of trace and macro elements appear to be associated with the presence of oceanic conditions, such as upwelling and potential changes in the composition of their diet associated with the depth in which these crustaceans are collected.

Feeding habits of the sharpnose shark Rhizoprionodon longurio on the west coast of the Gulf of California, Mexico

Abstract The sharpnose shark (Rhizoprionodon longurio) is among the top three shark species captured by artisanal fisheries of the Gulf of California. This study includes information regarding the feeding habits of this species using the stomach contents of 70 individuals ranged from 54 to 109 cm in total length (TL). Out of the 16 prey items identified, fish of the families Scombridae (Scomber japonicus; prey-specific relative importance index [%PSIRI] = 6.3) and Batrachoididae (%PSIRI = 5.5), the cephalopod Lolliguncula spp. (%PSIRI = 6.3), and the crustacean Pleuroncodes planipes (%PSIRI = 4.3) were the most important prey. Only female stomachs were obtained (N = 19) in the central area of the gulf, and the PSIRI indicated that the preferred prey were the cephalopod Lolliguncula spp. (%PSIRI = 10.5) and fish of the Sparidae family (Calamus brachysomus; %PSIRI = 5.8). The number of stomachs was not sufficient to analyse differences by sex. Regarding its trophic position, R. longurio was a tertiary consumer (TL K = 4.4). A TL K = 4.4 was calculated for the central area, and a TL K = 4.3 for the southern area. According to Levin's index (Bi), this shark is a specialist predator in the whole study area (Bi = 0.19), including the centre (Bi = 0.29). Conversely, it was considered a generalist predator in the southern area (Bi = 0.63). The high quantity of empty stomachs could relate to the time the sharks were caught in fishing a gear.

Little evidence for bioaccumulation or biomagnification of microplastics in a deep-sea food web

Microplastic contamination is documented in marine organisms, but little is known about bioaccumulation or biomagnification of microplastics, especially in tissues external to the gastro-intestinal (GI) tract. The objective of this work was to explore microplastic contamination in GI tracts and other tissues (abdomen and tail in crustaceans; mantle in cephalopods; fillets in fishes) of species at different trophic levels sampled in a deep-sea food web in Monterey Bay, CA, USA. The species included are tuna crab Pleuroncodes planipes, market squid Doryteuthis opalescens, northern lampfish Stenobrachius leucopsarus, chub mackerel Scomber japonicus, California halibut Paralichthys californicus, and Chinook salmon Oncorhynchus tshawytscha. After chemical digestion, microplastics in GI tracts were quantified and identified to material type using μ-Raman spectroscopy and in other tissues using pyrolysis-GC/MS. The concentrations of microplastics in GI tracts were significantly different among species, and microplastic contamination was dominated by microfibers. The concentrations of microplastics (mainly polyethylene and polyvinyl chloride) in other tissues also varied among species. A significant positive correlation between body size and plastic concentration in other tissues was observed for halibut only, suggesting bioaccumulation may not be ubiquitous. The trophic magnification factor for microplastics beyond the GI tract was <1, suggesting that biomagnification is not occurring in tissues. However, we did observe evidence for biomagnification of microplastics in the GI tracts. Future studies are needed to better understand these patterns and the mechanisms for translocation, bioaccumulation, and biomagnification of microplastics in aquatic organisms.

Oxygen and irradiance constraints on visual habitat in a changing ocean: The luminoxyscape

Oxygen and irradiance constraints on visual habitat in a changing ocean: The luminoxyscape

Feeding guilds among batoids in the northwest coast of the Baja California Sur, Mexico

AbstractResearch on the feeding habits of batoids provides information of intra and interspecific interactions of this taxon in marine ecosystems. We analyzed 832 stomachs of nine ray species collected from the artisanal fishery on the Northwest coast of Baja California Sur (NBCS). We identified 79 prey items assembled in five trophic groups (crustaceans, fish, mollusks, polychaetes, and sipunculidae). Results indicated that the red crabPleuroncodes planipeswas the most important prey in the diet of the seven batoid species. A low dietary similarity of the rays was observed, which evidenced different feeding strategies. In this regard, we identified four well‐separated trophic guilds. Each guild was characterized by the consumption of specific prey: (1)Hypanus dipterurusandNarcine entemedorthat fed mostly on polychaetes; (2)Rostroraja veleziandGymnura marmoratafed mostly on fishes (Clupeidae and Batrachoididae); (3)Hypanus longus,Myliobatis californica, andPlatyrhinoidis triseriatafed on crustaceans (Munnidae) and Sipunculus worms; and (4)Pseudobatos productusandZapteryx exasperatafed on crustaceans (Portunidae) and fishes (Synodontidae and Batrachoididae). We concluded that batoids off the NBCS show prey sharing between the different species.

Pacific bluefin tuna, Thunnus orientalis, exhibits a flexible feeding ecology in the Southern California Bight.

Pacific bluefin tuna, Thunnus orientalis, migrates from spawning grounds in the western Pacific Ocean to foraging grounds in the California Current System (CCS), where they are thought to specialize on high energy, surface schooling prey. However, there has been substantial variability in estimates of forage availability in the CCS over the past two decades. To examine the foraging ecology of juvenile T. orientalis in the face this variability, we quantified the diet and prey energetics of 963 individuals collected in the Southern California Bight (SCB) from 2008 to 2016. Using classification and regression tree analysis, we observed three sampling periods characterized by distinct prey. In 2008, T. orientalis diet was dominated by midwater lanternfishes and enoploteuthid squids. During 2009–2014, T. orientalis consumed diverse fishes, cephalopods, and crustaceans. Only in 2015–2016 did T. orientalis specialize on relatively high energy, surface schooling prey (e.g. anchovy, pelagic red crab). Despite containing the smallest prey, stomachs collected in 2009–2014 had the highest number of prey and similar total energetic contents to stomachs collected in 2015–2016. We demonstrate that T. orientalis is an opportunistic predator that can exhibit distinct foraging behaviors to exploit diverse forage. Expanding our understanding of T. orientalis foraging ecology will improve our ability to predict its responses to changes in resource availability as well as potential impacts on the fisheries it supports.

Distribution of Hg and Se in Muscle and Liver of the Thornback Guitarfish Platyrhinoidis triseriata from the Eastern Pacific Ocean.

Human consumption of the thornback guitarfish (Platyrhinoidis triseriata) is concentrated in coastal populations of the Pacific coast of Mexico as its meat is prized for its high quality. This study analyzes the distribution of mercury and selenium in the muscle and liver of Platyrhinoidis triseriata and the risk to human health associated with its consumption. In order to conduct these estimates, specimens were collected from the Eastern Pacific Ocean in 2015 and 2016 and found mean concentrations (µg g-1 wet weight) of mercury ranging from 0.02 to 0.58 in muscle and 0.10 to 0.31 in liver. Selenium ranged from 0.14 to 1.31 in muscle and from 0.93 to 4.52 in liver. Mercury levels in the muscle of P. triseriata were significantly correlated (positive correlation) with the total length of the specimens. The predominant prey of P. triseriata was the shrimp Pleuroncodes planipes and according to the biomagnification factor, only mercury was biomagnified. The risk to consumers associated with the simultaneous presence of mercury and selenium in the muscle and liver of rays under the selenium health benefit value approach indicated that consumption of P. triseriata from this area is beneficial to human health.

Changes in the feeding habits of the bat ray Myliobatis californica (Gill 1865) during climatic anomalies off the west coast of the Baja California Peninsula, Mexico

The Mexican Pacific was influenced by “La Mancha” and “El Niño”, from 2014 and until 2016. The increase in sea surface temperature influenced the feeding habits of the bat ray (Myliobatis californica) in the northwest of Baja California Sur, Mexico. To evaluate possible changes in the diet, stomach content analysis and analysis of stable isotopes of carbon (δ13C) and nitrogen (δ15N) in muscle was performed during normal (2012 and 2013) and anomalous years (2014, 2015, and 2016). During the normal years, the main prey was the crab Dynomene spp. (% Prey Specific Relative Importance Index (PSIRI) = 29.3) and the stomatopod Hemisquilla californiensis (% PSIRI = 10.6). In contrast, during the anomalous years, these preys were replaced by the pelagic red crab Pleuroncodes planipes (% PSIRI = 28.5) and peanut worms Sipunculus spp. (% PSIRI = 7.9). During normal years the median isotopic values recorded were: δ13C = −16.2‰ and δ15N = 15.2‰. During the anomalous years, δ13C was −16.3‰ and δ15N was 15.1‰. Between the different periods no trophic (p (probability) > 0.05) or isotopic overlaps (p > 0.3) were found. The change in the diet of M. californica during the anomalous years is an adaptive response to the increase in water temperature caused by “La Mancha” and “El Niño”. The massive presence of P. planipes on the northwest coast of Baja California Sur is associated with the increase in water temperature, which makes P. planipes a food source for M. californica.

Feeding habits of Paralabrax nebulifer (Serranidae) during reproductive and non-reproductive seasons in an adjacent area to Magdalena Bay, Baja California Sur, Mexico

The barred sand bass Paralabrax nebulifer is a commercially important fish off the west coast of Baja California Sur. To assess the diet of this species and variations as a function of sex and reproductive condition, 60 specimens were captured using traps during seven seasonal sampling trips from August 2016 to August 2018 in an adjacent area to Magdalena Bay, Baja California Sur, Mexico. The stomach contents of 50 specimens were obtained (23 males and 27 females). Sex was diagnosed by direct observation of the gonads. Based on the gonadosomatic index, hepatosomatic index, and histological analyses, the reproductive season of the barred sand bass was corroborated for August 2016, April, August, and September 2017, and August 2018, and the non-reproductive season was corroborated for November 2016 and March 2018. The Index of Relative Importance (IRI) was used to classify the main diet components, which comprised three fish species, seven crustacean species, and one mollusk species. According to the IRI, the South American pilchard Sardinops sagax and the red pelagic crab Pleuroncodes planipes were the prey that contributed the most (55%) to the barred sand bass diet. The ANOSIM showed that there were significant differences in the amount and type of prey consumed by sex; the SIMPER analysis revealed that the species contributing the most to differences between the sexes were S. sagax (16.58%), Euphylax dovii (15.95%), Stenocionops ovata (12%), and P. planipes (11.82%) for females. There were significant differences in the amount and type of prey consumed between types of reproductive season; the species contributing the most to differences between seasons were Anchoa spp. (27.76%), and P. planipes for non-reproductive season (22.67%), and S. sagax (11.08%) for reproductive season. The feeding strategy of the barred sand bass was that of a specialist carnivorous predator that fed mainly on the fish Sardinops sagax during the reproductive season, which supply the dietary nutritional requirements of the lipids HUFA (arachidonic acid, 20:4n-6; eicosapentaenoic acid, 20:5n-3; docosahexaenoic acid, 22:6n-3), nutrients required to achieve reproductive success.

Diversity and life-cycle analysis of Pacific Ocean zooplankton by video microscopy and DNA barcoding: Crustacea

Determining the DNA sequencing of a small element in the mitochondrial DNA (DNA barcoding) makes it possible to easily identify individuals of different larval stages of marine crustaceans without the need for laboratory rearing. It can also be used to construct taxonomic trees, although it is not yet clear to what extent this barcode-based taxonomy reflects more traditional morphological or molecular taxonomy. Collections of zooplankton were made using conventional plankton nets in Newport Bay and the Pacific Ocean near Newport Beach, California (Lat. 33.628342, Long. -117.927933) between May 2013 and January 2020, and individual crustacean specimens were documented by video microscopy. Adult crustaceans were collected from solid substrates in the same areas. Specimens were preserved in ethanol and sent to the Canadian Centre for DNA Barcoding at the University of Guelph, Ontario, Canada for sequencing of the COI DNA barcode. From 1042 specimens, 544 COI sequences were obtained falling into 199 Barcode Identification Numbers (BINs), of which 76 correspond to recognized species. For 15 species of decapods (Loxorhynchus grandis, Pelia tumida, Pugettia dalli, Metacarcinus anthonyi, Metacarcinus gracilis, Pachygrapsus crassipes, Pleuroncodes planipes, Lophopanopeus sp., Pinnixa franciscana, Pinnixa tubicola, Pagurus longicarpus, Petrolisthes cabrilloi, Portunus xantusii, Hemigrapsus oregonensis, Heptacarpus brevirostris), DNA barcoding allowed the matching of different life-cycle stages (zoea, megalops, adult). The results show the utility of DNA barcoding for matching life-cycle stages as well as for documenting the diversity of this group of organisms.

Anomalous poleward advection facilitates episodic range expansions of pelagic red crabs in the eastern North Pacific

AbstractThe episodic stranding of millions of pelagic red crabs (Pleuroncodes planipes) along California beaches is a striking and puzzling phenomenon. Pleuroncodes planipes are usually abundant off Baja California, Mexico, and their appearance in central California is thought to coincide with anomalously warm waters and northward advection related to El Niño. This anecdotal association has stimulated many hypotheses, but no hypothesis has gained clear and convincing support. Motivated by an unprecedented number of P. planipes strandings and at‐sea observations in 2015–2019, we compiled 10 P. planipes datasets spanning 1950–2019, tested the anomalous advection hypothesis using a transport analysis from 1981 to 2010, and explored other compelling hypotheses. We found P. planipes presence off central California was related to anomalous advection of waters from Mexico, sometimes but not always associated with El Niño events, with P. planipes likely remaining residents of northern waters for several years without additional anomalous transport but potentially facilitated by warm waters. By identifying a mechanism behind episodic P. planipes range expansions, we show that a source water index could provide an early indicator for anomalous events in the future.

Mercury and selenium concentrations in different tissues of brown smooth-hound shark (Mustelus henlei) from the western coast of Baja California Sur, Mexico

A study on mercury (Hg) and selenium (Se) concentrations in the liver and muscle of brown smooth-hound shark Mustelus henlei and its principal prey items, was conducted in the western coast of Baja California Sur, Mexico. Average Hg concentrations were found to be high in the muscle than in the liver; however, Hg concentrations were below the maximum permissible limits, and hence, the consumption of this species does not constitute a risk to human health. The mean Se concentrations were higher in the liver than in the muscle. The results of Hg: Se molar ratio revealed that Se counteracts the toxicity of Hg in hepatic tissues, whereas the contrary occurs in the muscle. Significant differences in Hg and Se accumulation were observed between females and males. Biomagnification factor values >1 demonstrate a biomagnification process from its principal prey species (i.e., red crab, Pleuroncodes planipes and Pacific mackerel, Scomber japonicus).

Trophic interactions between shark species on the western coast of Baja California Sur: Inferences from stable isotopes

On the west coast of Baja California Sur, the shark species Mustelus henlei, Carcharhinus falciformis, Prionace glauca, Isurus oxyrinchus, and Sphyrna zygaena are of economic importance and coexist in the same ecosystem. However, the trophic role of each species in this ecosystem is poorly understood. Stable isotopes of nitrogen and carbon (δ15N, δ13C) have been used as an indicator of trophic habitat at different time scales, showing the foraging area and trophic position of sharks. The isotopic values in the muscle and blood of five shark species were analyzed on the southwest coast of Baja California Sur. The isotopic values of P. glauca, S. zygaena and C. falciformis indicated a trophic habitat in oceanic areas, which is a characteristic of these species considering that they feed mainly on mesopelagic cephalopods; whereas M. henlei and I. oxyrinchus showed a benthic diet in oceanic waters. The highest trophic position based on muscle and blood results was in S. zygaena, while the lowest trophic position was in the tissue of C. falciformis, probably because this species feeds on a higher proportion of the crustacean Pleuroncodes planipes. Some of these species share prey and forage in the same area.

The vertical distribution and biological transport of marine microplastics across the epipelagic and mesopelagic water column

Plastic waste has been documented in nearly all types of marine environments and has been found in species spanning all levels of marine food webs. Within these marine environments, deep pelagic waters encompass the largest ecosystems on Earth. We lack a comprehensive understanding of the concentrations, cycling, and fate of plastic waste in sub-surface waters, constraining our ability to implement effective, large-scale policy and conservation strategies. We used remotely operated vehicles and engineered purpose-built samplers to collect and examine the distribution of microplastics in the Monterey Bay pelagic ecosystem at water column depths ranging from 5 to 1000 m. Laser Raman spectroscopy was used to identify microplastic particles collected from throughout the deep pelagic water column, with the highest concentrations present at depths between 200 and 600 m. Examination of two abundant particle feeders in this ecosystem, pelagic red crabs (Pleuroncodes planipes) and giant larvaceans (Bathochordaeus stygius), showed that microplastic particles readily flow from the environment into coupled water column and seafloor food webs. Our findings suggest that one of the largest and currently underappreciated reservoirs of marine microplastics may be contained within the water column and animal communities of the deep sea.

Marine larval vision suffers in low oxygen

Human brains don't do well without oxygen. When mountaineer Thomas Hornbein ascended Everest in 1963, he described his vision dimming when his oxygen regulator jarred loose. Fortunately, few of us experience hypoxia in such dramatic situations, but Lillian McCormick, from the Scripps Institution of Oceanography, explains that many aquatic creatures routinely encounter potentially threatening oxygen levels. ‘In nearshore areas of the Pacific Ocean off southern California, organisms can be exposed to reduced oxygen even in 0–50 m depth,’ she says. And when she reviewed the literature, it was clear that species with complex eyes would be most at risk of visual impairment. However, she and her colleagues Lisa Levin and Nicholas Oesch noticed that little was known about the ill effects of hypoxia on the larvae of many of these species.To rectify the situation, McCormick went trawling for plankton. ‘I hand-sorted each tow to set aside the larvae that we were interested in’, says McCormick, who decided to test the vision of larvae of the two spot octopus (Octopus bimaculatus), the tuna crab (Pleuroncodes planipes) and the graceful rock crab (Metacarcinus gracilis). However, she had to wait for the first and new moons of each month, when the market squid (Doryteuthis opalescens) spawn, to collect freshly laid egg sacs, which she took back to the lab to wait for the youngsters to hatch. Then, she painstakingly inserted a minute electrode into the retina of each tiny larva to record the eye's responses to light. Gradually decreasing and then increasing the concentration of oxygen dissolved in the water, McCormick recorded the response of each larva's retina to 1 s flashes of light. And when the oxygen was at ∼21, ∼10 and ∼3%, she shone a series of increasingly dimmer 1 s flashes into their eyes. In addition, McCormick shone a flickering light that gradually speeded up until the flashes blurred into one into the eyes of the squid and tuna crab larvae to find out how well the tiny animals could see fast-moving objects as the oxygen dwindled.Shockingly, all of the larvae lost some or all of their vision as the oxygen declined, with the market squid and graceful rock crab larvae unexpectedly beginning to suffer vision loss as soon as the oxygen began dropping. In contrast, the light response of the two spot octopus and tuna crab larval retinas held out reasonably well until the oxygen fell to ∼13%. By the time the oxygen had dipped to ∼3%, most of the squid, octopus and graceful rock crab larvae had completely lost their vision, although the retinal response of the tuna crab larvae only dipped to 60%. And while the speed of the tuna crab larvae's vision barely faltered at the lower oxygen levels, the response time of the squid larvae's retina reduced significantly, suggesting that they may really struggle to see the fast-moving copepods, upon which they dine, when oxygen is scarce.‘We calculate that the decline in retinal function due to decreased oxygen availability in larvae that move from 0 to 30 m depth in spring in southern California would be 15–59%’, says McCormick; which means that these minute creatures may already be experiencing visual loss in their natural environment. And she is concerned that additional declines in oxygen availability could place the larvae at further risk. ‘If larvae are unable to detect small changes in light intensity, or the swimming movements of their prey, they may not survive’, she warns.

Vision is highly sensitive to oxygen availability in marine invertebrate larvae.

For many animals, evolution has selected for complex visual systems despite the high energetic demands associated with maintaining eyes and their processing structures. Therefore, the metabolic demands of visual systems make them highly sensitive to fluctuations in available oxygen. In the marine environment, oxygen changes over daily, seasonal and inter-annual time scales, and there are large gradients of oxygen with depth. Vision is linked to survival in many marine animals, particularly among the crustaceans, cephalopods and fish, and early life stages of these groups rely on vision for prey capture, predator detection and their distribution in the water column. Using in vivo electroretinogram recordings, we show that there is a decrease in retinal sensitivity to light in marine invertebrates when exposed to reduced oxygen availability. We found a 60-100% reduction in retinal responses in the larvae of cephalopods and crustaceans: the market squid (Doryteuthis opalescens), the two-spot octopus (Octopus bimaculatus), the tuna crab (Pleuroncodes planipes) and the graceful rock crab (Metacarcinus gracilis). A decline in oxygen also decreases the temporal resolution of vision in D. opalescens These results are the first demonstration that vision in marine invertebrates is highly sensitive to oxygen availability and that the thresholds for visual impairment from reduced oxygen are species-specific. Oxygen-impaired retinal function may change the visual behaviors crucial to survival in these marine larvae. These findings may impact our understanding of species' vulnerability to ocean oxygen loss and suggest that researchers conducting electrophysiology experiments should monitor oxygen levels, as even small changes in oxygen may affect the results.

Reproductive Biology of the Red Crab Pleuroncodes planipes (Anomuran, Galatheid) on the West Coast of the Baja California Peninsula, Mexico

The reproductive biology of the red crab Pleuroncodes planipes, an abundant but unfished galatheid species, was studied using specimens collected from the west coast of Baja California, Mexico, in November 2006 and March 2007. Crabs were caught with a bottom trawl at predefined stations. Sex ratios were not significantly different from 1:1 (P > 0.05). The six stages of oogenesis and 10 oocyte substages in P. planipes are described. Results suggest a synchronous maturation pattern with multiple spawnings during the breeding season. In males, spermatogenesis occurs as a continuous process. The estimated cephalothorax length (CL) at 50% sexual maturity for females was 23.6 mm and 22.3 mm for the November 2006 and March 2007 cruises, respectively; for males, it was 26.8 mm and 25.3 mm. Batch fecundity of females ranged from 267 to 25,674 eggs for red crabs 9.5–33.87 mm CL. Batch fecundity was positively correlated with CL (P < 0.05; r2 = 0.84 and 0.93).

Feeding habits of the swordfish (Xiphias gladius Linnaeus, 1758) in the subtropical northeast Pacific

With the aim to expand the understanding of the feeding ecology of the swordfish, two supplementary techniques were used: analysis of stomach contents, including 244 samples; and analysis of stable carbon (δ13C) and nitrogen (δ15N) isotopes, with 128 samples of muscle tissues from animals collected in the western coast of Baja California. Samples were obtained from swordfish captured by the longline fleet that operates along the western coast of Baja California peninsula. Thirty-three different prey types were identified through the analysis of stomach contents. Based on the index of relative importance (IRI), cephalopods accounted for 98.91%, fish 0.88%, and pelagic crustaceans 0.21%. The stable isotope analysis showed δ15N values between 13.05‰ and 19.66‰, and δ13C values between − 19.32‰ and − 15.60‰, indicating that the swordfish feeds primarily on oceanic species. The stable isotope mixing model (SIAR) established that prey species that most contribute to the diet of Xiphias gladius were cephalopods, followed by the crustacean Pleuroncodes planipes, and the fish Lagocephalus lagocephalus. The SIBER test corroborates similar diets between sexes and sex-maturity groups, indicating that all swordfish analyzed essentially occupied the same trophic niche.

Isotopic insights into migration patterns of Pacific bluefin tuna in the eastern Pacific Ocean

Understanding regional migration, residency dynamics, and associated trophic ecology can inform recovery strategies for pelagic species such as Pacific bluefin tuna (Thunnus orientalis) (PBFT). PBFT residency duration in the eastern Pacific is uncertain, particularly for larger individuals (here, &gt;100 cm or ∼3+ years of age). We applied a previously tested “chemical tracer toolbox” (Fukushima-derived radiocesium and 13C and 15N stable isotope signatures) to examine migratory and residency patterns and dietary inputs of 428 age 1–6+ PBFT collected from 2012 to 2015 in the eastern Pacific Ocean. Age 1–3 individuals were a mix of residents and recent (≤500 day) migrants, while 98% of age 3–4 and 100% of age 4–6.3 year old PBFT were resident for &gt;500 days in the eastern Pacific. Zooplanktivorous forage (e.g., sardine, anchovy, pelagic red crab, and trophically similar species) of the California Current Ecosystem constituted 57%–82% of diet across PBFT sizes. Migration timing estimates show that PBFT may spend 2–5 years in the eastern Pacific Ocean before returning to the western Pacific.

Metabolic suppression in the pelagic crab, Pleuroncodes planipes, in oxygen minimum zones.

The pelagic red crab, Pleuroncodes planipes, is abundant throughout the Eastern Tropical Pacific in both benthic and pelagic environments to depths of several hundred meters. The oxygen minimum zones in this region reaches oxygen levels as low as 0.1kPa at depths within the crabs vertical range. Crabs maintain aerobic metabolism to a critical PO2 of ~0.27±0.2kPa (10°C), in part by increasing ventilation as oxygen declines. At subcritical oxygen levels, they enhance anaerobic ATP production slightly as indicated by modest increases in lactate levels. However, hypoxia tolerance is primarily mediated via a pronounced suppression of aerobic metabolism (~70%). Metabolic suppression is achieved, primarily, via reduced protein synthesis, which is a major sink for metabolic energy. Posttranslational modifications on histone H3 suggest a condensed chromatin state and, hence, decreased transcription. Under hypoxia, p-H3S10, Ac-H3K9, Ac-H3K14 were 39, 68, and 36% of control values, respectively. We also report a net decrease in protein translation. In particular, eEF2 activity is reduced due to a ~5-fold increase in inhibitory phosphorylation and a significant decrease in protein level. Elevated heat shock proteins suggest that, despite impressive tolerance, the cellular stress response is triggered during hypoxia. We discuss the implications for pelagic ecology and biogeochemical cycles.