The Shark Assemblage at French Frigate Shoals Atoll, Hawai‘i: Species Composition, Abundance and Habitat Use

Empirical data on the abundance and habitat preferences of coral reef top predators are needed to evaluate their ecological impacts and guide management decisions. We used longline surveys to quantify the shark assemblage at French Frigate Shoals (FFS) atoll from May to August 2009. Fishing effort consisted of 189 longline sets totaling 6,862 hook hours of soak time. A total of 221 sharks from 7 species were captured, among which Galapagos (Carcharhinus galapagensis, 36.2%), gray reef (Carcharhinus amblyrhynchos, 25.8%) and tiger (Galeocerdo cuvier, 20.4%) sharks were numerically dominant. A lack of blacktip reef sharks (Carcharhinus melanopterus) distinguished the FFS shark assemblage from those at many other atolls in the Indo-Pacific. Compared to prior underwater visual survey estimates, longline methods more accurately represented species abundance and composition for the majority of shark species. Sharks were significantly less abundant in the shallow lagoon than adjacent habitats. Recaptures of Galapagos sharks provided the first empirical estimate of population size for any Galapagos shark population. The overall recapture rate was 5.4%. Multiple closed population models were evaluated, with Chao Mh ranking best in model performance and yielding a population estimate of 668 sharks with 95% confidence intervals ranging from 289–1720. Low shark abundance in the shallow lagoon habitats suggests removal of a small number of sharks from the immediate vicinity of lagoonal islets may reduce short-term predation on endangered monk seal (Monachus schauinslandi) pups, but considerable fishing effort would be required to catch even a small number of sharks. Additional data on long-term movements and habitat use of sharks at FFS are required to better assess the likely ecological impacts of shark culling

Comparison of relative abundances of sharks determined from underwater visual surveys and longline fishing surveys.

<p>Species composition of the shark assemblage obtained by (A) towboarding (underwater visual census, adapted from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0016962#pone.0016962-Holzwarth1" target="_blank">[9]</a>) throughout the Papahānaumokuākea Marine National Monument and (B) shark longline fishing surveys at French Frigate Shoals atoll.</p

Sex ratios for the five most common species of sharks at French Frigate Shoals atoll.

<p>*P values in bold for χ² tests are statistically significant.</p

Spatial distribution of longline Catch Per Unit Effort (CPUE).

<p>In all panels, scaled circles indicate CPUE >0, crosses indicate CPUE  = 0. CPUE  =  sharks per 10 hook hours.</p

Map of Study Area.

<p>French Frigate Shoals atoll within the Papahānaumokuākea Marine National Monument (shaded area inset).</p

Population estimates for Galapagos sharks at French Frigate Shoals atoll from closed population models.

<p>Population estimates for Galapagos sharks at French Frigate Shoals atoll from closed population models.</p

Mean Catch Per Unit Effort (CPUE) for shark species within habitats and overall.

<p>Shaded bars represent CPUE within habitats, unshaded bars represent overall CPUE. OB: Outside barrier reef; DL: Deep lagoon; SL: Shallow lagoon; CPUE  =  sharks per 10 hook hours.</p

Summary of longline fishing data.

<p>Shark numbers indicate the sum of all sharks caught combined and by habitat. Values in parentheses are row percentages of all sharks.</p><p>*Other species include scalloped hammerhead and whitetip reef sharks,</p><p>*OB: Outside Barrier Reef,</p><p>*DL: Deep Lagoon,</p><p>*SL: Shallow Lagoon.</p

Higher harmonic non-linear flow modes of charged hadrons in Pb-Pb collisions at sNN\sqrt{s_{\rm{NN}}} = 5.02 TeV

International audienceAnisotropic flow coefficients, v$_{n}$, non-linear flow mode coefficients, χ$_{n,mk}$, and correlations among different symmetry planes, ρ$_{n,mk}$ are measured in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. Results obtained with multi-particle correlations are reported for the transverse momentum interval 0.2 < p$_{T}$< 5.0 GeV/c within the pseudorapidity interval 0.4 < |η| < 0.8 as a function of collision centrality. The v$_{n}$ coefficients and χ$_{n,mk}$ and ρ$_{n,mk}$ are presented up to the ninth and seventh harmonic order, respectively. Calculations suggest that the correlations measured in different symmetry planes and the non-linear flow mode coefficients are dependent on the shear and bulk viscosity to entropy ratios of the medium created in heavy-ion collisions. The comparison between these measurements and those at lower energies and calculations from hydrodynamic models places strong constraints on the initial conditions and transport properties of the system.[graphic not available: see fulltext