Field Studies of the Population Dynamics of the Spotted Spiny Lobster Panulirus guttatus (Latreille) at Bermuda

Results of a study on the population dynamics of the spotted spiny lobster Panulirus guttatus (Latreille) at Bermuda are described. The annual growth coefficients (K) for male and female spotted spiny lobsters P. guttatus are estimated at 0.22 and 0.16 from size frequency analyses. Annual total mortality, fishing mortality, natural mortality, and recruitment coefficients (Z, F, M, and R) for 1987 were estimated at 0.79, 0.46, 0.33, and 0.79, respectively, based on length and weight data and the exploitation rate (E = 0.58) was estimated from population weight data. The catchability coefficient (q) for 1987 was estimated at 3.9 X 10-6/ trap-haul from the estimate of F and the 1987 data for total effort. The stock size (N1987) of trappable P. guttatus lobsters at the start of calendar year 1987 was estimated at approximately 71 X 103 individuals from q and industry catch and effort data. The population showed marked spatial preference with the density at the reef crest an order of magnitude greater than in the reef system as a whole

Summer Diet of the Bearded Seal (Erignathus barbatus) in the Canadian High Arctic

Stomach contents of 34 bearded seals taken in three High Arctic localities (Grise Fiord, Pond Inlet and Clyde) during the summers from 1978-1980 were examined. At least 12 species of fish were present but sculpins (Cottidae) and arctic cod (Boreogadus saida) comprised the bulk of the diet. Eelpouts (Lycodes spp.) and polar cod (Arctogadus glacialis) were also ingested in considerable amounts. In 15 of 19 stomachs containing > 1 kg food, fish contributed > 90% of the wet weight. The whelk Buccinem and the shrimp Sclerocrangon boreas accounted for most of the invertebrate component of the diet. Clams, cephalopods, anemones, sea cucumbers, polychaete worms and other invertebrates occurred in small amounts. The largest measured weight of stomach contents was 7.6 kg from a seal that had fed heavily on arctic cod. There were no significant differences amongst the three localities in the amount of food ingested; however, the proportions of arctic cod and sculpins varied considerably among localities. Bearded seals fed on the available size range of arctic cod but were limited to the smaller sculpins (<200 g), eelpouts (<200 g) and polar cod (<350 g).Key words: bearded seals, Canadian High Arctic, dietMots clés: phoques barbus, nord de l'Arctique canadien, régime alimentair

Critical Exponents and Stability at the Black Hole Threshold for a Complex Scalar Field

This paper continues a study on Choptuik scaling in gravitational collapse of a complex scalar field at the threshold for black hole formation. We perform a linear perturbation analysis of the previously derived complex critical solution, and calculate the critical exponent for black hole mass, $\gamma \approx 0.387106$. We also show that this critical solution is unstable via a growing oscillatory mode.Comment: 15 pages of latex/revtex; added details of numerics, in press in Phys Rev D; 1 figure included, or available by anonymous ftp to ftp://ftp.itp.ucsb.edu/figures/nsf-itp-95-58.ep

Dynamics of former ice lobes of the southernmost Patagonian Ice Sheet based on a glacial landsystems approach

Reconstructions of former ice masses from glacial geomorphology help to constrain the nature and timing of glaciation in relation to climatic forcing. This paper presents a new reconstruction of the glacial history of five ice lobes in southernmost South America: the Bahía Inútil − San Sebastián, Magellan, Otway, Skyring and Río Gallegos ice lobes. We use previous geomorphological mapping of glacial landforms to reconstruct former glacial limits and proglacial lakes, demarcate flow-sets from the distribution of glacial lineations, and evaluate glacial landsystem signatures and their palaeoglaciological implications. Evidence suggests that the ice lobes predominantly reflect active temperate glacial landsystems, which may have switched to polythermal systems when periods of cold-based ice developed ephemerally. This complex landsystem signature implies that the ice lobes were sensitive to regional climate variability, with active re-advances during overall retreat of the ice margins. There is also evidence for periods of fast ice flow and possible surge-like activity in the region, followed by the rapid retreat or even collapse of some of the ice lobes in association with proglacial lakes. Constraining our new reconstruction with published chronological information suggests that at least some of the ice lobes advanced before the global Last Glacial Maximum (gLGM: ca. 26.5–19 ka) during the last glacial cycle. Our new reconstruction demonstrates a more complex picture of ice dynamics than has previously been portrayed, and one in which the advance and retreat of the ice lobes was likely to have been primarily driven by changes in climate. As such, ice advances before the gLGM in the southernmost part of the Patagonian Ice Sheet are likely to indicate a wider climatic forcing at this time

Eccentric-orbit extreme-mass-ratio-inspiral radiation: Analytic forms of leading-logarithm and subleading-logarithm flux terms at high PN orders

We present new results on the analytic eccentricity dependence of several sequences of gravitational wave flux terms at high post-Newtonian (PN) order for extreme-mass-ratio inspirals. These sequences are the leading logarithms, which appear at PN orders x3klogk(x) and x3k+3/2logk(x) for integers k≥0 (x is a PN compactness parameter), and the subleading logarithms, which appear at orders x3klogk-1(x) and x3k+3/2logk-1(x) (k≥1), in both the energy and angular momentum radiated to infinity. For the energy flux leading logarithms, we show that to arbitrarily high PN order, their eccentricity dependence is determined by particular sums over the function g(n,et), derived from the Newtonian mass quadrupole moment, that normally gives the spectral content of the Peters-Mathews flux as a function of radial harmonic n. An analogous power spectrum g(n,et) determines the leading logarithms of the angular momentum flux. For subleading logs, the quadrupole power spectra are again shown to play a role, providing a distinguishable part of the eccentricity dependence of these flux terms to high PN order. With the quadrupole contribution understood, the remaining analytic eccentricity dependence of the subleading logs can, in principle, be determined more easily using black hole perturbation theory. We show this procedure in action, deriving the complete analytic structure of the x6log(x) subleading-log term and an analytic expansion of the x9/2 subleading log to high order in a power series in eccentricity. We discuss how these methods might be extended to other sequences of terms in the PN expansion involving logarithms

Eccentric-orbit extreme-mass-ratio-inspiral radiation. II. 1PN correction to leading-logarithm and subleading-logarithm flux sequences and the entire perturbative 4PN flux

In a recent paper we showed that for eccentric-orbit extreme-mass-ratio inspirals the analytic forms of the leading-logarithm energy and angular momentum post-Newtonian (PN) flux terms (radiated to infinity) can, to arbitrary PN order, be determined by sums over the Fourier spectrum of the Newtonian quadrupole moment. We further showed that an essential part of the eccentricity dependence of the related subleading-logarithm PN sequences, at lowest order in the symmetric mass ratio ?, stems as well from the Newtonian quadrupole moment. Once that part is factored out, the remaining eccentricity dependence is more easily determined by black hole perturbation theory. In this paper we show how the sequences that are the 1PN corrections to the entire leading-logarithm series, namely terms that appear at PN orders x3k+1logk(x) and x3k+5/2logk(x) (for PN compactness parameter x and integers k=0), at lowest order in ?, are determined by the Fourier spectra of the Newtonian mass octupole, Newtonian current quadrupole, and 1PN part of the mass quadrupole moments. We also develop a conjectured (but plausible) form for 1PN correction to the leading logs at second order in ?. Further, in analogy to the first paper, we show that these same source multipole moments also yield nontrivial parts of the 1PN correction to the subleading-logarithm series, and that the remaining eccentricity dependence (at lowest order in ?) can then more easily be determined using black hole perturbation theory. We use this method to determine the entire analytic eccentricity dependence of the perturbative (i.e., lowest order in ?) 4PN nonlog terms, R4(et) and Z4(et), for energy and angular momentum respectively

Universality in axisymmetric vacuum collapse

Evidence of universality is observed in the critical behavior of axisymmetric vacuum gravitational collapse. The threshold of black hole formation in the future development of time-antisymmetric initial data is found numerically and compared to previous results based on ingoing pulses of gravitational waves. The power-law behavior of the black hole mass is again found near the critical point and the critical exponent value β0.36 is consistent with our previous determination despite stark differences in the two sets of initial data. Similar evidence of universality is exhibited by the scaling factor Δ of the echoes in the gravitational field produced in the central region of collapse

Critical behavior and scaling in vacuum axisymmetric gravitational collapse

We report a second example of critical behavior in gravitational collapse. Collapse of axisymmetric gravitational wave packets is computed numerically for a one-parameter family of initial data. A black hole first appears along the sequence at a critical parameter value p*. As with spherical scalar-field collapse, a power law is found to relate black-hole mass (the order parameter) and critical separation: MBHp-p*β. The critical exponent is β0.37, remarkably close to that observed by Choptuik. Near-critical evolutions produce echoes from the strong-field region which appear to exhibit scaling

Trapping a geon: Black hole formation by an imploding gravitational wave

We describe the formation of a black hole via the implosion of an axisymmetric gravitational wave. Finite difference simulations of the vacuum Einstein equations are used to obtain these results. The initial data consist of nearly linear solutions to the vacuum constraint equations that represent even-parity, ingoing wave packets with quadrupole angular dependence. A black hole is demonstrated to form as a result of imploding a wave packet with a sufficiently large value of a strength parameter, 2Mp=1.06>crit0.80, where 2 is the radial width of the wave packet and Mp denotes its mass. Black hole formation is verified by observing (i) the exponential collapse of the central value of the lapse function , (ii) the formation of a trapped region and marginally outer-trapped surfaces, and (iii) the emission of quasi-normal-mode radiation. For the =1.06 case, just over 2% of the mass emerges in normal-mode radiation