Ocean Feeding Grounds Research Articles

High historical movement rates of Antarctic blue whales on Southern Ocean feeding grounds estimated from Discovery mark data

High historical movement rates of Antarctic blue whales on Southern Ocean feeding grounds estimated from Discovery mark data

Song recordings suggest feeding ground sharing in Southern Hemisphere humpback whales

The Atlantic sector of the Southern Ocean (ASSO) has one of the highest densities of Antarctic krill (Euphausia superba) compared to other polar and subpolar regions, which attracts migratory baleen whale species to aggregate in this area for feeding. Humpback whales (Megaptera novaeangliae) also sing extensively while on the Southern Ocean feeding grounds which allows for the exploration of song similarity between feeding grounds and breeding populations which helps to understand population mixing. The results of comparative song analyses between the ASSO and the Ecuadorian and Brazilian breeding populations and recordings from the Chilean, South African and Namibian migration routes/mid-latitude feeding grounds revealed that individuals from at least three humpback whale breeding populations most likely migrate to shared feeding grounds in the ASSO. Humpback whales from different populations potentially mix at different times (i.e., years) at feeding hotspots in variable locations. The ASSO seems to provide sufficient prey resources and seems to present an important area for both cultural and maybe even genetic exchange between populations supporting the maintenance of large gene pools. Assuming that multi-population feeding hotspots are also suitable habitat for krill and other krill-dependent predators, these areas in the ASSO should be carefully managed integrating population, ecosystem and fisheries management.

How northern elephant seals mobilise blubber for fuel when fasting

When food is scarce, most animals go into survival mode, reducing their activity to conserve energy. But not northern elephant seals (Mirounga angustirostris). Leaving their ocean feeding grounds and hauling themselves onto Californian and Mexican beaches for weeks, the females give birth, nursing their pups, while the males posture as they protect their harems; all of which they do while fasting. Jane Khudyakov from the University of the Pacific, USA, explains that during this time the animals depend on their extensive fat reserves for survival. However, it wasn't clear how the animals coordinate their tissue energy use while going without. ‘The cellular mechanisms that regulate these adaptations are still not fully understood’, she says. Teaming up with collaborators Dan Crocker (Sonoma State University, USA) and Dan Costa [University of California, Santa Cruz (UCSC), USA], Khudyakov and Rachel Holser (UCSC) headed down to the elephant seals’ breeding grounds at Año Nuevo State Reserve, USA, when the animals returned to moult, to find out.‘They shed old skin and hair within several weeks’, says Khudyakov, adding, ‘it literally peels off in sheets, which makes the beach very smelly’. However, the moulting females are easier to approach than when fasting in the breeding season while protecting their pups. Surrounded by the colony, Holser with colleagues from Costa's lab gently anaesthetised five animals that had just returned from 3–4 month foraging trips, ready for Khudyakov to take small blood, muscle and fat samples at the beginning and end of the moult. In addition, the team weighed the females, recording that the animals lost ∼3 kg per day – totalling ∼28% of their body mass over the ∼33 day period – in the form of skin, hair and fat.Back in the lab, Khudyakov and University of the Pacific undergraduates Serena Ly and Theron Niel extracted proteins from the muscle and blubber before Craig Vierra and Basma Hasan (University of the Pacific) joined them to analyse the protein content, alongside that of the blood sample. ‘We identified 1053 proteins in blubber, 711 in muscle and 260 in blood, most of which have not been studied before in seals’, says Khudyakov. Yet, when the team compared the composition of the muscle and blubber over the month-long fast, they found they had changed little. ‘This suggests that protein turnover in these tissues may be tightly controlled’, says Khudyakov. However, the quantities of three key proteins involved in fat accumulation reduced in all three tissues as the animals switched from storing to consuming fat.In contrast, 53 blood proteins involved in controlling and transporting lipids around the body increased dramatically, including hormones that regulate the release and transport of lipids and those that control how the body uses lipids as a fuel. ‘We think that changes in these proteins may help seals quickly switch their metabolism between feeding and fasting without any of the adverse effects that such rapid fat gain and loss would cause in humans’, says Khudyakov. And when the team checked on the quantities of fat circulating in the animals’ blood, they found that triglycerides – a form of fat – and high-density lipoproteins – ‘good’ cholesterol – did not change significantly, ‘suggesting that seals very tightly regulate their fat reserves, despite using them for energy, during fasting’, says Khudyakov.So, fasting elephant seals are able to sustain an active lifestyle by mobilising fats from their blubber in a controlled way. And Khudyakov is keen to find out how the proteins that regulate fat use change when the females produce full-fat (60%) milk for their pups, although that will require running the gauntlet of the fiercely protective mothers’ teeth.

Humpback whale song recordings suggest common feeding ground occupation by multiple populations

Humpback whale males are known to sing on their low-latitude breeding grounds, but it is well established that songs are also commonly produced ‘off-season’ on the feeding grounds or during migration. This opens exciting opportunities to investigate migratory aggregations, study humpback whale behavioral plasticity and potentially even assign individual singers to specific breeding grounds. In this study, we analyzed passive acoustic data from 13 recording positions and multiple years (2011–2018) within the Atlantic sector of the Southern Ocean (ASSO). Humpback whale song was detected at nine recording positions in five years. Most songs were recorded in May, austral fall, coinciding with the rapid increase in sea ice concentration at most recording positions. The spatio-temporal pattern in humpback whale singing activity on Southern Ocean feeding grounds is most likely shaped by local prey availability and humpback whale migratory strategies. Furthermore, the comparative analyses of song structures clearly show a differentiation of two song groups, of which one was solely recorded at the western edge of the ASSO and the other song group was recorded throughout the ASSO. This new finding suggests a common feeding ground occupation by multiple humpback whale populations in the ASSO, allowing for cultural and potentially even genetic exchange among populations.

Multi‐tissue stable isotope analyses reveal temporal changes in the feeding patterns of green turtles in the Galapagos Marine Reserve

Knowledge of feeding patterns of highly migratory species is critical for understanding their habitat use and informing the management of their populations. The Galapagos Islands are one of the most important nesting and feeding areas for green turtles (Chelonia mydas) across the tropical eastern Pacific, yet little is known about the feeding patterns of this species. The isotopic composition of different tissues has been used to gain insight into the trophic dynamics of mobile aquatic consumers whose trophic behavior is difficult to directly measure. To elucidate the temporal feeding patterns and isotopic niche sizes of Galapagos green turtles, stable isotope analyses were performed on multiple tissues (skin and carapace) collected at the two most important nesting areas in the archipelago: Bachas and Quinta Playa. The δ13 C and δ15 N signatures on the skin and carapace samples from 56 adult femalesrevealed significant differences between tissues (p = .001 and p = .021, respectively) and nesting areas (p = .011 and p = .003, respectively). These differences suggest a shift from oceanic feeding grounds to neritic habitats before nesting. The carapace isotope values indicated an offshore feeding strategy and a greater isotopic niche (SEAc = 1.91‰2 ), whereas the skin isotope values represented an inshore feeding strategy with a narrower niche (SEAc = 1.37‰2 ), likely related to the consumption of specific coastal prey. Our results suggest that Galapagos green turtles feed across different habitats, and this information can be applied to improve the management ofthis endangered species.

Limits on performance and survival of juvenile sockeye salmon (Oncorhynchus nerka) during food deprivation: a laboratory-based study.

Long-distance migrations can be energetically demanding and can represent phases of high mortality. Understanding relationships between body condition and migratory performance can help illuminate the challenges and vulnerabilities of migratory species. Juvenile anadromous sockeye salmon (Oncorhynchus nerka) may migrate over 1000km from their freshwater nursery habitats to estuary and ocean feeding grounds. During the period corresponding to the seaward migration of sockeye salmon, we held smolts in the laboratory to ask the following: (i) Does non-feeding migration duration influence prolonged swim performance and survival? (ii) What are the relationships between individual body condition and swim performance and survival? Wild sockeye salmon were intercepted during their migration and held without food for up to 61days to represent the non-feeding freshwater migration and the extremes of poor estuary habitat. We conducted 40 sets of prolonged swim trials on 319 fish from 3 treatment groups that represented entrance to the marine environment on (i) an average,(ii) a delayed and (iii) a severely delayed migration schedule. Experimentally controlled freshwater migration duration did not impact swim performance or survival. Swim performance decreased concomitant with condition factor, where smolts with a Fulton's condition factor of <0.69 were less likely (<50% probability) to complete the swim test (90min swim test, at ~0.50m/s). Survival of salmon smolts in the laboratory was less likely at energy densities of less than 3.47MJ/kg. Swim performance decreased much sooner than survival, suggesting that swim performance, and therefore condition factor, may be a good indicator of survival of migratory smolts, as fish with reduced swim performance will likely be predated. These two relationships, one more ecologically relevant and one more clinical, help reveal the limits of long-distance migration for juvenile salmon and can be used to determine population-specific starvation risk associated with various freshwater and marine habitat conditions.

Distribution and abundance of humpback whales, Megaptera novaeangliae, off the coast of Mozambique, 2003

Humpback whales within the southwestern Indian Ocean undertake annual migrations from summer Antarctic/Southern Ocean feeding grounds towinter breeding grounds in the tropical and sub-tropical coastal waters of Mozambique, Madagascar and the central Mozambique Channel Islands.Little is known of the inter-relationship of humpback whales on each of these wintering grounds, or the inter-relationship of these wintering groundswith the summer Antarctic feeding grounds.A line-transect survey of cetacean species was carried out in Mozambique coastal waters between Cabo Inhaca (26°00’S, 33°05’E) and just northof Mozambique Island (14°26’S, 40°53’E) and between the 20 and 200m isobaths, over the period 26 August to 7 September 2003. The majority(98.1%) of 951.8 n.miles of search effort carried out on this survey was in passing mode due to the high densities of whales encountered. Humpbackwhales were the only large whales to be identified and the distribution of 691 sightings of an estimated 1,130 individual humpback whales and 132sightings of an estimated 154 large unidentified whales show distribution throughout the survey region. Two sightings of individual small whaleswere made in the region of Inhambane.In general, higher than expected sighting densities (based on survey effort) were recorded in the region between Cabo Inhaca and Xai-Xai, andin the region of the Pantaloon and David Shoals to the north east of Quelimane. Lower than expected sighting densities were recorded over theSofala Banks. No distribution trends could be ascribed to environmental parameters, apart from whales being distributed in waters of higher salinitiesthan expected, possibly due to turbidity associated with low salinity water arising from river input. Groups containing a cow and calf pair weredistributed across the entire region surveyed.Analyses of unstratified data result in a total abundance estimate of 6,808 (CV = 0.14) humpback and unidentified whales in the 14,029.5 n.mile2area surveyed. As a result of the differences in width of the coastal shelf area along the coast of Mozambique, the line transect survey data werefurther analysed in four strata. Pooling of estimates over these four strata results in a total abundance of 6,664 whales (CV = 0.16), with highestdensities in the southernmost stratum and the lowest densities in the narrow shelf region across the Sofala Banks. Similar analyses of humpbackwhales only resulted in abundance estimates of 5,930 (CV = 0.15) (unstratified data) and 5,965 whales (CV = 0.17) (data analysed by four strata).Although not directly comparable due to differing survey platforms, these estimates indicate the population to have increased since previous surveysin the early 1990s.

Regional variation in directed swimming by Atlantic salmon smolts leaving Scottish waters for their oceanic feeding grounds—a modelling study

Abstract An understanding of the migratory trajectories and behaviours of Atlantic salmon post-smolts during the early marine phase of their life cycle is needed for effective conservation and marine planning. A simulation study of post-smolt migration from Scottish shores was carried out, combining a high-resolution hydrodynamic model of the Scottish continental shelf with a Lagrangian particle tracking model. Various different notional swimming behavioural scenarios were simulated, including current-orientated and compass-directed movement across a range of swimming speeds. Current-following behaviours did not facilitate migration towards feeding grounds in the North Atlantic. In addition, modelled trajectories resulting from directed-swimming behaviours imply that populations around Scotland need to adopt different locally adapted migratory strategies to successfully reach their feeding grounds.

Application of a multi-disciplinary approach to reveal population structure and Southern Ocean feeding grounds of humpback whales

Obtaining direct measurements to characterise ecosystem function can be hindered by remote or inaccessible regions. Next-generation satellite tags that inform increasingly sophisticated movement models, and the miniaturisation of animal-borne loggers, have enabled the use of animals as tools to collect habitat data in remote environments, such as the Southern Ocean. Research on the distribution, habitat use and recovery of Oceania’s humpback whales (Megaptera novaeangliae) has been constrained by the inaccessibility to their Antarctic feeding grounds and the limitations of technology. In this multi-disciplinary study, we combine innovative analytical tools to comprehensively assess the distribution and population structure of this marine predator throughout their entire migratory range. We used genotype and photo-identification matches and conducted a genetic mixed-stock analysis to identify the breeding ground origins of humpback whales migrating past the Kermadec Islands, New Zealand. Satellite tracking data and a state-space model were then used to identify the migratory paths and behaviour of 18 whales, and to reveal their Antarctic feeding ground destinations. Additionally, we conducted progesterone assays and epigenetic aging to determine the pregnancy rate and age-profile of the population. Humpback whales passing the Kermadec Islands did not assign to a single breeding ground origin, but instead came from a range of breeding grounds spanning ∼3500 km of ocean. Sampled whales ranged from calves to adults of up to 67 years of age, and a pregnancy rate of 57% was estimated from 30 adult females. The whales migrated to the Southern Ocean (straight-line distances of up to 7000 km) and spanned ∼4500 km across their Antarctic feeding grounds. All fully tracked females with a dependent calf (n = 4) migrated to the Ross Sea region, while 70% of adults without calves (n = 7) travelled further east to the Amundsen and Bellingshausen Seas region. By combining multiple research and analytical tools we obtained a comprehensive understanding of this wide-ranging, remote population of whales. Our results indicate a population recovering from exploitation, and their feeding ground distribution serves as an indicator of the resources available in these environments. The unexpected Kermadec Islands migratory bottle-neck of whales from several breeding grounds, variable distribution patterns by life history stage and high pregnancy rates will be important in informing conservation and management planning, and for understanding how this, as well as other whale populations, might respond to emerging threats such as climate change.

Emperor penguins may snack to shorten record fast

The endurance of emperor penguins, trudging through the perpetual Antarctic night to their breeding colonies, is legendary. Many trek more than 100 km from their ocean feeding grounds to rookeries at inland locations in preparation for mating; and the male partners often face a lengthy fast of more than 100 days while mating and incubating their eggs before embarking on the lengthy return journey. However, Gerald Kooyman from the University of California, San Diego explains that not all emperor penguin colonies are as icebound. ‘The Ross Sea colonies are near the fast sea-ice edge (unbroken sea ice attached to the coastline), meaning that they are within easy walking distance [of the water]’, he explains. So when he was offered the opportunity to join an expedition heading south to the Ross Ice Shelf on the Icebreaker Nathaniel B. Palmer during the austral winter of 1998 to survey the region's animals, Kooyman snatched it up.Yet, the expedition's success was far from assured; no ship had ever reached the Ross Ice Shelf during winter. However, after successfully reaching their destination, Kooyman convinced the vessel's captain and the expedition Chief Scientist, Martin Jeffries, to make a detour west to Cape Washington to observe an emperor penguin colony during the return journey. As the ship approached the ice edge near the colony in late May, a member of the expedition noticed a group of 30 penguins unexpectedly swimming in the open water. They were diving in the dark, even though the birds were thought only to dive in light conditions in order to avoid predators and becoming entombed beneath the ice when air holes close. ‘If the birds can successfully hunt in the dark, it makes sense that they would feed during the prenuptial and pre-laying period’, explains Kooyman.Disembarking from the ship, Kooyman, Robert van Dam and several other members of the expedition set off in search of the colony. ‘In the rough ice at 6′4″, Robert was an excellent spotter of seals and penguins’, Kooyman recalls, adding that the team also encountered two groups of penguins returning to the colony from the open water during the moonless 4 km trek. And when the scientists reached the colony, they found countless tracks, indicating other recent departures for the nearby water. Also, Kooyman and his colleagues arrived while the mating season was still in full swing and before the males had begun incubating their eggs, despite the lateness of the season – when other colonies had already laid their eggs and the females departed.Considering all of the observations, Kooyman says, ‘The [Cape Washington] breeding males may have a shorter fast because they feed between arrival at the colony and over the ensuing 2 months during the pre-nuptial activities’. In contrast to the 115 day fast experienced by birds that head far inland to mate and incubate their eggs, he suspects that these emperor penguins may endure a shorter fast of a minimum of 65 days.After locating the colony, Kooyman collected and weighed four of the birds and attached satellite tags that would track their movements for several months. Later, when the satellite data began returning, he saw that the first bird departed the colony 9 days after the tag was fitted, followed by the three remaining penguins during the next fortnight. And when Luis Hückstädt analysed the paths taken by the birds, it was clear that they were all diving in dark conditions before the sun's return. Kooyman warns that as the rise in Antarctic temperatures persists, many more emperor penguins may be forced to dive in the dark if the ice around the northern perimeter of the continent continues thinning, driving colonies further south in search of more stable breeding grounds.

High habitat use plasticity by female olive ridley sea turtles (Lepidochelys olivacea) revealed by stable isotope analysis in multiple tissues

The marine habitat use of olive ridley sea turtles (Lepidochelys olivacea) from northeastern Brazil was analyzed via stable isotope analysis (SIA). Blood (red blood cells and serum), epidermis and scute samples from 46 nesting females were collected for SIA of carbon (δ 13C) and nitrogen (δ 15N) to infer the habitats used at distinct time windows. Such approach is possible because each tissue reflects consumer’s diet at different time scales due to different tissue turnover time. Prey representative of both neritic and oceanic realms was used as endpoints. Differences in the residence time of δ 13C and δ 15N among samples indicated a shift from oceanic feeding grounds to neritic habitats before nesting or effects of prolonged fasting on stable isotope values. However, two individuals seemed to have used neritic feeding habitats for longer timespans before the nesting period. Stable isotope mixing models demonstrated high individual variability, suggesting the variable use of non-breeding grounds. Moreover, serum indicated that olive ridleys might feed during the nesting season, most likely opportunistically on discards from trawl fisheries. Finally, through correlations of stable isotope values among tissues, this study provides equations for the conversion and adequate comparison between values from different tissues. Therefore, the habitats used by olive ridley sea turtles from Brazil are vast, encompassing both oceanic and neritic habitats, where they encounter pelagic longline and trawl fisheries, respectively. The high individual variability in the population results in turtles experiencing distinct and variable threats during their annual cycle.

Population genetic structure among feeding aggregations of humpback whales in the Southern Ocean

Humpback whales (Megaptera novaeangliae) undertake seasonal migrations between low-latitude breeding grounds in winter and high-latitude feeding grounds in summer. In the Southern Hemisphere, seven primary breeding stocks have been identified based on tropical distribution between which there is limited gene flow. In the summer, these stocks are distributed among six Management Areas (Areas I–VI) defined by the International Whaling Commission in the Southern Ocean feeding grounds. The extent to which different breeding stocks mix on these feeding grounds, and the genetic structure and relationships between them, remains unclear. This uncertainty has led to the review and development of hypotheses to refine stock boundaries in the Antarctic. This study is the first to analyse the circumpolar genetic structure of humpback whales in their feeding aggregations. Sequences of the mitochondrial control region and microsatellite DNA variation were obtained for 399 humpback whale samples, obtained within the six Antarctic Management Areas. Results from both sets of markers were consistent in showing a complex pattern of differentiation between feeding aggregations across the feeding range. Management Area I surrounding the Antarctic Peninsula, associated with Breeding Stock G in the south-eastern Pacific Ocean, was highly differentiated from all other feeding aggregations, suggesting strong fidelity towards the Peninsula. In contrast, adjacent feeding grounds showed much lower levels or no significant differentiation, suggesting interchange of individuals and overlap of breeding stocks on their summer feeding grounds. These results have important implications from the perspective of conservation and management, as failure to recognize overlapping distributions may result in misleading estimates of abundance and growth trends of particular recovering humpback whale populations.

Humpback Whale Song on the Southern Ocean Feeding Grounds: Implications for Cultural Transmission

Male humpback whales produce a long, complex, and stereotyped song on low-latitude breeding grounds; they also sing while migrating to and from these locations, and occasionally in high-latitude summer feeding areas. All males in a population sing the current version of the constantly evolving display and, within an ocean basin, populations sing similar songs; however, this sharing can be complex. In the western and central South Pacific region there is repeated cultural transmission of song types from eastern Australia to other populations eastward. Song sharing is hypothesized to occur through several possible mechanisms. Here, we present the first example of feeding ground song from the Southern Ocean Antarctic Area V and compare it to song from the two closest breeding populations. The early 2010 song contained at least four distinct themes; these matched four themes from the eastern Australian 2009 song, and the same four themes from the New Caledonian 2010 song recorded later in the year. This provides evidence for at least one of the hypothesized mechanisms of song transmission between these two populations, singing while on shared summer feeding grounds. In addition, the feeding grounds may provide a point of acoustic contact to allow the rapid horizontal cultural transmission of song within the western and central South Pacific region and the wider Southern Ocean.

The diets of humpback whales (Megaptera novaeangliae) on the shelf and oceanic feeding grounds in the western North Pacific inferred from stable isotope analysis

AbstractHumpback whales feed on a variety of prey, but significant differences likely occur between regional feeding grounds. In this study, the diets of humpback whales were analyzed by comparing stable isotope ratios in animal tissues at three humpback whale feeding grounds in the Russian Far East: Karaginsky Gulf, Anadyr Gulf, and the Commander Islands. Anadyr Gulf is a neritic zone far from a shelf break, Karaginsky Gulf is a neritic zone close to a shelf break, and the Commander Islands represent an open oceanic ecosystem where whales feed off the shelf break. Samples from the Commander Islands had the lowest mean δ13C and δ15N values (mean ± SE: δ13C = −18.7 ± 0.1, δ15N = 10.4 ± 0.1) compared to the samples from Karaginsky Gulf (δ13C = −17.2 ± 0.1, δ15N = 12.7 ± 0.2) and Anadyr Gulf (δ13C= −17.8 ± 0.1, δ15N = 14.0 ± 0.4). The samples from Anadyr Gulf had the highest δ15N values, while the samples from Karaginsky Gulf had the highest δ13C values. Both δ13C and δ15N values differed significantly among all three areas. Our data support the hypothesis that humpback whales tend to feed on fish in neritic areas and on plankton in deep oceanic waters.

Humpback whale song occurs extensively on feeding grounds in the western North Atlantic Ocean

Male humpback whales produce complex, patterned songs that are traditionally heard on their breeding grounds. Short-term studies demonstrated that they also sing along mi - gration routes and on higher-latitude feeding grounds. This study expands the current under- standing of feeding-ground song by providing yearlong views of singing activity. Acoustic record- ings were made in Stellwagen Bank National Marine Sanctuary, part of the western North Atlantic Ocean feeding grounds. Recordings were made in 2006 and 2008. Song occurred during all months except February 2006 and June 2008. Song occurred most frequently in November for both years (mean ± SE — 2006: 18.26 ± 0.66 h with song d -1 ; 2008: 18.59 ± 0.82 h with song d �1 ). The longest song sessions occurred in April for both years (2220 ± 348, 1430 ± 274 s, respectively) in November and December for 2006, and in May for 2008. This study demonstrates that song occurs often, when whales arrive at the feeding grounds in early April. The occurrence and length of song sessions decrease during July and August when whales are observed to be feeding in the sanctuary. Song occurrence and song session length increase when most males prepare to migrate southward in October to December. Such patterns are congruent with the hypothesis of seasonal hormonal activity and its potential role in song production.

Transcriptomics of environmental acclimatization and survival in wild adult Pacific sockeye salmon (Oncorhynchus nerka) during spawning migration

Environmental shifts accompanying salmon spawning migrations from ocean feeding grounds to natal freshwater streams can be severe, with the underlying stress often cited as a cause of increased mortality. Here, a salmonid microarray was used to characterize changes in gene expression occurring between ocean and river habitats in gill and liver tissues of wild migrating sockeye salmon (Oncorhynchus nerka Walbaum) returning to spawn in the Fraser River, British Columbia, Canada. Expression profiles indicate that the transcriptome of migrating salmon is strongly affected by shifting abiotic and biotic conditions encountered along migration routes. Conspicuous shifts in gene expression associated with changing salinity, temperature, pathogen exposure and dissolved oxygen indicate that these environmental variables most strongly impact physiology during spawning migrations. Notably, transcriptional changes related to osmoregulation were largely preparatory and occurred well before salmon encountered freshwater. In the river environment, differential expression of genes linked with elevated temperatures indicated that thermal regimes within the Fraser River are approaching tolerance limits for adult salmon. To empirically correlate gene expression with survival, biopsy sampling of gill tissue and transcriptomic profiling were combined with telemetry. Many genes correlated with environmental variables were differentially expressed between premature mortalities and successful migrants. Parametric survival analyses demonstrated a broad-scale transcriptional regulator, cofactor required for Sp1 transcriptional activation (CRSP), to be significantly predictive of survival. As the environmental characteristics of salmon habitats continue to change, establishing how current environmental conditions influence salmon physiology under natural conditions is critical to conserving this ecologically and economically important fish species.

Life History and Seasonal Stock‐Specific Ocean Migration of Juvenile Chinook Salmon

AbstractThe ocean feeding grounds of juvenile Pacific salmonOncorhynchusspp. range over several thousand kilometers in which ocean conditions, prey quality and abundance, and predator assemblages vary greatly. Therefore, the fate of individual stocks may depend on where they migrate and how much time they spend in different regions. Juvenile (n= 6,266) and immature (n= 659) Chinook salmonOncorhynchus tshawytschawere collected from coastal Washington to Southeast Alaska in coastal trawl surveys from February to November 1998–2008, which allowed us to reconstruct changes in stock composition for seasons and regions by means of DNA stock identification techniques. Individuals were allocated to 12 regional stocks. The genetic stock assignments were directly validated by showing that 96% of the 339 known‐origin, coded‐wire‐tagged fish were accurately allocated to their region of origin. Overall, the analyses performed in this study support the main findings of previous work based on tagging. However, given that the sample sizes for all stocks were larger and additional stocks were analyzed, we can extend those results; coastal residency of local stocks in their first year at sea with differences between smolt classes for southern stocks. Notably, yearling Chinook salmon moved quickly into waters north of the west coast of Vancouver Island, including Southeast Alaska. Furthermore, subyearling salmon were found over shallower bottom depths than yearling fish. Summer catches in all regions were dominated by Columbia River yearling fish, which suggests a rapid northward migration. In contrast, very few Columbia River subyearling fish were recovered north of Vancouver Island. Columbia River fish were a minor component of the catches in fall and winter, as fish originating from other southern stocks dominated catches off the west coast of Vancouver Island while northern British Columbia and Southeast Alaska stocks dominated northern regions during these time periods. In addition, we found no effect of hatchery origin on the distribution of fish.

Locations of marine animals revealed by carbon isotopes

Knowing the distribution of marine animals is central to understanding climatic and other environmental influences on population ecology. This information has proven difficult to gain through capture-based methods biased by capture location. Here we show that marine location can be inferred from animal tissues. As the carbon isotope composition of animal tissues varies with sea surface temperature, marine location can be identified by matching time series of carbon isotopes measured in tissues to sea surface temperature records. Applying this technique to populations of Atlantic salmon (Salmo salar L.) produces isotopically-derived maps of oceanic feeding grounds, consistent with the current understanding of salmon migrations, that additionally reveal geographic segregation in feeding grounds between individual philopatric populations and age-classes. Carbon isotope ratios can be used to identify the location of open ocean feeding grounds for any pelagic animals for which tissue archives and matching records of sea surface temperature are available.

CHANGES IN ODORANT RECEPTOR MESSENGER RNA EXPRESSION ASSOCIATED WITH MATURATION, REPRODUCTIVE HORMONES, AND HOMING IN SOCKEYE SALMON (ONCORHYNCHUS NERKA)

Event Abstract Back to Event CHANGES IN ODORANT RECEPTOR MESSENGER RNA EXPRESSION ASSOCIATED WITH MATURATION, REPRODUCTIVE HORMONES, AND HOMING IN SOCKEYE SALMON (ONCORHYNCHUS NERKA) Andrew Dittman1*, Darran May2, Larissa Felli2 and Penny Swanson1 1 Northwest Fisheries Science Center, NOAA Fisheries, United States 2 University of Washington, United States Seasonal migrations for reproduction are common in many mid-high latitude animals and for many species there are strong links between hormones, reproduction and migration. In addition, hormones associated with sexual maturation may modulate the sensory systems involved in migratory and reproductive behaviors. The homing migration of Pacific salmon from oceanic feeding grounds back to their river of origin to spawn provides an ideal model for studying the endocrine control of neuronal plasticity and sensory physiology involved in migration. The final stages of salmon homing migrations are governed by olfactory discrimination of homestream odors that juvenile salmon learn (imprint to) prior to their seaward migrations. One aspect of the imprinting and homing process involves long-term sensitization of the peripheral olfactory system to specific odorants associated with their natal stream. Concurrent with these homing migrations, salmon experience dramatic changes in hormones associated with gametogenesis and final maturation. In this study, we examined changes in odorant receptor (OR) mRNA expression in the olfactory epithelium of sockeye salmon exposed to specific odorants during sensitive periods for imprinting. We then examined the patterns of OR mRNA expression during final maturation, the period when salmon would be homing in the wild. Developmental increases in OR mRNA expression were correlated with surges in plasma luteinizing hormone (LH) and reproductive steroids that occurred just prior to final maturation. Differences in OR mRNA expression levels between imprinted and unimprinted fish were apparent prior to the surge in LH and final maturation and were consistent with increased sensitivity to imprinted odors during the period salmon would be homing to their natal streams. Acknowledgements Supported by the Bonneville Power Administration and the NWFSC) Keywords: imprinting, maturation, Olfaction, Salmon Conference: NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology, Ann Arbor, United States, 13 Jul - 16 Jul, 2011. Presentation Type: Invited Symposium Topic: Ectohormones Citation: Dittman A, May D, Felli L and Swanson P (2011). CHANGES IN ODORANT RECEPTOR MESSENGER RNA EXPRESSION ASSOCIATED WITH MATURATION, REPRODUCTIVE HORMONES, AND HOMING IN SOCKEYE SALMON (ONCORHYNCHUS NERKA). Front. Endocrinol. Conference Abstract: NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology. doi: 10.3389/conf.fendo.2011.04.00129 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 22 Jul 2011; Published Online: 09 Aug 2011. * Correspondence: Dr. Andrew Dittman, Northwest Fisheries Science Center, NOAA Fisheries, Seattle, United States, andy.dittman@noaa.gov Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Andrew Dittman Darran May Larissa Felli Penny Swanson Google Andrew Dittman Darran May Larissa Felli Penny Swanson Google Scholar Andrew Dittman Darran May Larissa Felli Penny Swanson PubMed Andrew Dittman Darran May Larissa Felli Penny Swanson Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Population structure and conservation implications for the loggerhead sea turtle of the Cape Verde Islands

The Cape Verde Islands harbour the second largest nesting aggregation of the globally endangered loggerhead sea turtle in the Atlantic. To characterize the unknown genetic structure, connectivity, and demographic history of this population, we sequenced a segment of the mitochondrial (mt) DNA control region (380 bp, n = 186) and genotyped 12 microsatellite loci (n = 128) in females nesting at three islands of Cape Verde. No genetic differentiation in either haplotype or allele frequencies was found among the islands (mtDNA FST = 0.001, P > 0.02; nDNA FST = 0.001, P > 0.126). However, population pairwise comparisons of the mtDNA data revealed significant differences between Cape Verde and all previously sequenced Atlantic and Mediterranean rookeries (FST = 0.745; P < 0.000). Results of a mixed stock analysis of mtDNA data from 10 published oceanic feeding grounds showed that feeding grounds of the Madeira, Azores, and the Canary Islands, in the Atlantic Ocean, and Gimnesies, Pitiuses, and Andalusia, in the Mediterranean sea, are feeding grounds used by turtles born in Cape Verde, but that about 43% (±19%) of Cape Verde juveniles disperse to unknown areas. In a subset of samples (n = 145) we evaluated the utility of a longer segment (~760 bp) amplified by recently designed mtDNA control region primers for assessing the genetic structure of Atlantic loggerhead turtles. The analysis of the longer fragment revealed more variants overall than in the shorter segments. The genetic data presented here are likely to improve assignment and population genetic analyses, with significant conservation and research applications.