Chaetognaths and oceanography on Georges Bank

A dense breeding population of chaetognaths, Sagitta elegans, was observed on northeastern Georges Bank during autumn, 1978. Four grid surveys conducted on the northeast region of the Bank over the period 17-30 October 1978 revealed that the high concentration patch of adult S. elegans. about 56 km on long axis, remained essentially on the eastern part of the grid in weakly stratified water of 67 m average depth. Current meter measurements indicated residual flow to the southeast sufficiently high to transport a passively drifting organism out of the area over the two weeks of study. Discrete vertical sampling showed that the reproductively mature adults underwent extensive migration from surface to near bottom by day in response to the solar cycle. The smaller immature stages did not migrate vertically or only had limited range; they were found throughout the water column, both day and night, and were spread across the shallow well-mixed as well as deeper weakly stratified waters. Using current meter records, transport of the migrating adults and essentially nonmigrating immature stages of the S. elegans population at different sites within the study area was modeled. The simulations revealed that the migration of adults to near bottom for several hours of the day, where the current was assumed to approach zero, resulted in a longer residence time on the Bank than for nonmigrating immatures. More importantly, it is shown how the strong lunar tidal regime characteristic of Georges Bank may be an important mechanism for generating smaller scale variability on the order of \u3c50 km and \u3c2 weeks

Distribution of Short-finned Squid (IIlex illecebrosus) Larvae and Juveniles in Relation to the Gulf Stream Frontal Zone Between Florida and Cape Hatteras

Catches of rhynchoteuthion type C' larvae, which are considered to be II/ex illecebrosus, and I. il/ecebrosus juveniles over the edge of the continental shelf between Cape Hatteras and Florida are examined in relation to the water masses and their dynamics along the Gulf Stream~Slope Water frontal zone. All larvae and juveniles were captured at stations where the temperature~salinity (T-S) properties of the upper 50 m of the water column were closely grouped, with temperatures of 21.0° to 23.5° C and salinities of 36.30 to 36.80, which are very similar to those of Continental Edge Water. Although the actual depths of capture of the larvae and juveniles in the bongo and midwater trawl tows are unknown, it is likely that the majority were taken in the upper 50 m. Larvae and juveniles were intermixed along the entire frontal zone, but there are indications of some differences in microscale distribution. Although juveniles were nearly always captured at stations where larvae were taken, larvae were captured at only 44% of the stations where juveniles were found. The intermixture of larvae and juveniles with a broad range of size (mantle length) indicates that spawning occurs either along the Gulf Stream~Slope Water frontal zone south of Cape Hatteras or in a relatively small area to the south of the surveyed area. The possible role of frontal eddies in causing the intermixture of larvae and juveniles is discussed

Dive, food and exercise effects on blood microparticles in Steller sea lions (Eumetopias jubatus) : exploring a biomarker for decompression sickness

Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here by permission of American Physiological Society for personal use, not for redistribution. The definitive version was published in American Journal of Physiology - Regulatory, Integrative and Comparative Physiology 310 (2016): R596-R601, doi:10.1152/ajpregu.00512.2015.Recent studies of stranded marine mammals indicate that exposure to underwater military sonar may induce pathophysiological responses consistent with decompression sickness (DCS). However, DCS has been difficult to diagnose in marine mammals. We investigated whether blood microparticles (MPs, measured as number/μl plasma), which increase in response to decompression stress in terrestrial mammals, are a suitable biomarker for DCS in marine mammals. We obtained blood samples from trained Steller sea lions (Eumetopias jubatus, 4 adult females) wearing time-depth recorders that dove to predetermined depths (either 5 or 50 m). We hypothesized that MPs would be positively related to decompression stress (depth and duration underwater). We also tested the effect of feeding and exercise in isolation on MPs using the same blood sampling protocol. We found that feeding and exercise had no effect on blood MP levels, but that diving caused MPs to increase. However, blood MP levels did not correlate with diving depth, relative time underwater, and presumably decompression stress―possibly indicating acclimation following repeated exposure to depth.Funding for this project was provided by the Office of Naval Research to MM (ONR Award # N00014-12-10388) and SRT (ONR Award # N00014-13-10614). Additional support was provided by the National Oceanic and Atmospheric Administration through the North Pacific Marine Science Foundation and the North Pacific Universities Marine Mammal Research Consortium.2017-02-0

Trade-offs between foraging efficiency and pup feeding rate of lactating northern fur seals in a declining population

Foraging strategies and their resulting efficiency (energy gain to cost ratio) affect animals’ survival and reproductive success and can be linked to population dynamics. However, they have rarely been studied quantitatively in free-ranging animals. We investigated foraging strategies and efficiencies of wild northern fur seals Callorhinus ursinus during their breeding season to understand potential links to the observed population decline in the Bering Sea. We equipped 20 lactating females with biologgers to determine at-sea foraging behaviours. We measured energy expenditure while foraging using the doubly-labelled water method, and energy gained using (1) the types and energy densities of prey consumed, and (2) the number of prey capture attempts (from acceleration data). Our results show that seals employed 2 foraging strategies: one group (40%) fed mostly in oceanic waters on small, high energy-density prey, while the other (60%) stayed over the shallow continental shelf feeding mostly on larger, lower quality fish. Females foraging in oceanic waters captured 3 times more prey, and had double the foraging efficiencies of females that foraged on-shelf in neritic waters. However, neritic seals made comparatively shorter trips, and likely fed their pups ~20 to 25% more frequently. The presence of these strategies which either favor foraging efficiency (energy) or frequency of nursing (time) might be maintained in the population because they have similar net fitness outcomes. However, neither strategy appears to simultaneously maximize time and energy allocated to nursing, with potential impacts on the survival of pups during their first year at sea

High Natality Rates of Endangered Steller Sea Lions in Kenai Fjords, Alaska and Perceptions of Population Status in the Gulf of Alaska

Steller sea lions experienced a dramatic population collapse of more than 80% in the late 1970s through the 1990s across their western range in Alaska. One of several competing hypotheses about the cause holds that reduced female reproductive rates (natality) substantively contributed to the decline and continue to limit recovery in the Gulf of Alaska despite the fact that there have been very few attempts to directly measure natality in this species. We conducted a longitudinal study of natality among individual Steller sea lions (n = 151) at a rookery and nearby haulouts in Kenai Fjords, Gulf of Alaska during 2003–2009. Multi-state models were built and tested in Program MARK to estimate survival, resighting, and state transition probabilities dependent on whether or not a female gave birth in the previous year. The models that most closely fit the data suggested that females which gave birth had a higher probability of surviving and giving birth in the following year compared to females that did not give birth, indicating some females are more fit than others. Natality, estimated at 69%, was similar to natality for Steller sea lions in the Gulf of Alaska prior to their decline (67%) and much greater than the published estimate for the 2000s (43%) which was hypothesized from an inferential population dynamic model. Reasons for the disparity are discussed, and could be resolved by additional longitudinal estimates of natality at this and other rookeries over changing ocean climate regimes. Such estimates would provide an appropriate assessment of a key parameter of population dynamics in this endangered species which has heretofore been lacking. Without support for depressed natality as the explanation for a lack of recovery of Steller sea lions in the Gulf of Alaska, alternative hypotheses must be more seriously considered

New Protocetid Whale from the Middle Eocene of Pakistan: Birth on Land, Precocial Development, and Sexual Dimorphism

BACKGROUND: Protocetidae are middle Eocene (49-37 Ma) archaeocete predators ancestral to later whales. They are found in marine sedimentary rocks, but retain four legs and were not yet fully aquatic. Protocetids have been interpreted as amphibious, feeding in the sea but returning to land to rest. METHODOLOGY/PRINCIPAL FINDINGS: Two adult skeletons of a new 2.6 meter long protocetid, Maiacetus inuus, are described from the early middle Eocene Habib Rahi Formation of Pakistan. M. inuus differs from contemporary archaic whales in having a fused mandibular symphysis, distinctive astragalus bones in the ankle, and a less hind-limb dominated postcranial skeleton. One adult skeleton is female and bears the skull and partial skeleton of a single large near-term fetus. The fetal skeleton is positioned for head-first delivery, which typifies land mammals but not extant whales, evidence that birth took place on land. The fetal skeleton has permanent first molars well mineralized, which indicates precocial development at birth. Precocial development, with attendant size and mobility, were as critical for survival of a neonate at the land-sea interface in the Eocene as they are today. The second adult skeleton is the most complete known for a protocetid. The vertebral column, preserved in articulation, has 7 cervicals, 13 thoracics, 6 lumbars, 4 sacrals, and 21 caudals. All four limbs are preserved with hands and feet. This adult is 12% larger in linear dimensions than the female skeleton, on average, has canine teeth that are 20% larger, and is interpreted as male. Moderate sexual dimorphism indicates limited male-male competition during breeding, which in turn suggests little aggregation of food or shelter in the environment inhabited by protocetids. CONCLUSIONS/SIGNIFICANCE: Discovery of a near-term fetus positioned for head-first delivery provides important evidence that early protocetid whales gave birth on land. This is consistent with skeletal morphology enabling Maiacetus to support its weight on land and corroborates previous ideas that protocetids were amphibious. Specimens this complete are virtual 'Rosetta stones' providing insight into functional capabilities and life history of extinct animals that cannot be gained any other way