Abundance of Belugas, Delphinapterus leucas, in Cook Inlet, Alaska, 1994–2000

Annual abundance estimates of belugas, Delphinapterus leucas, in Cook Inlet were calculated from counts made by aerial observers and aerial video recordings. Whale group-size estimates were corrected for subsurface whales (availability bias) and whales that were at the surface but were missed (detection bias). Logistic regression was used to estimate the probability that entire groups were missed during the systematic surveys, and the results were used to calculate a correction to account for the whales in these missed groups (1.015, CV = 0.03 in 1994–98; 1.021, CV = 0.01 in 1999– 2000). Calculated abundances were 653 (CV = 0.43) in 1994, 491 (CV = 0.44) in 1995, 594 (CV = 0.28) in 1996, 440 (CV = 0.14) in 1997, 347 (CV = 0.29) in 1998, 367 (CV = 0.14) in 1999, and 435 (CV = 0.23, 95% CI=279–679) in 2000. For management purposes the current Nbest = 435 and Nmin = 360. These estimates replace preliminary estimates of 749 for 1994 and 357 for 1999. Monte Carlo simulations indicate a 47% probability that from June 1994 to June 1998 abundance of the Cook Inlet stock of belugas was depleted by 50%. The decline appears to have stopped in 1998

Observations and Predictions of Arctic Climatic Change: Potential Effects on Marine Mammals

Recent analyses have revealed trends over the past 20-30 years of decreasing sea ice extent in the Arctic Ocean coincident with warming trends. Such trends may be indicative of the polar amplifications of warming predicted for the next several decades in response to increasing atmospheric CO2. We have summarized these predictions and nonuniform patterns of arctic climate change in order to address their potential effects on marine mammals. Since recent trends in sea ice extent are nonuniform, the direct and indirect effects on marine mammals are expected to vary geographically. Changes in the extent and concentration of sea ice may alter the seasonal distributions, geographic ranges, patterns of migration, nutritional status, reproductive success, and ultimately the abundance and stock structure of some species. Ice-associated seals, which rely on suitable ice substrate for resting, pupping, and molting, may be especially vulnerable to such changes. As recent decreases in ice coverage have been more extensive in the Siberian Arctic (60 E-180 E) than in the Beaufort Sea and western sectors, we speculate that marine mammal populations in the Siberian Arctic may be among the first to experience climate-induced geographic shifts or altered reproductive capacity due to persistent changes in ice extent. Alteration in the extent and productivity of ice-edge systems may affect the density and distribution of important ice-associated prey of marine mammals, such as arctic cod, Boreogadus saida, and sympagic ("with ice") amphipods. Present climate models, however, are insufficient to predict regional ice dynamics, winds, mesoscale features, and mechanisms of nutrient resupply, which must be known to predict productivity and trophic response. Therefore, it is critical that mesoscale process-oriented studies identify the biophysical coupling required to maintain suitable prey availability and ice-associated habitat for marine mammals on regional arctic scales. Only an integrated ecosystems approach can address the complexity of factors determining reproductivity and cascading trophic dynamics in a warmer Arctic. This approach, integrated with monitoring of key indicator species (e.g., bowhead whale, ringed seal, and beluga), should be a high priority.Des analyses récentes ont fait apparaître des tendances, au cours des 20 à 30 dernières années, à la diminution de l'étendue des glaces de mer dans l'océan Arctique qui coïncident avec des tendances au réchauffement. Ces tendances pourraient être symptomatiques de l'amplification polaire du réchauffement prédit pour les prochaines décennies suite à la hausse de CO2 dans l'atmosphère. Cet article offre un résumé de ces prédictions et des schémas non uniformes de changement climatique dans l'Arctique, en vue d'examiner leurs retombées potentielles sur les mammifères marins. Vu que les tendances récentes de l'étendue des glaces de mer ne sont pas uniformes, les retombées directes et indirectes sur les mammifères marins devraient varier sur le plan géographique. Des changements dans l'étendue et la concentration de la glace de mer peuvent modifier les distributions saisonnières, les aires géographiques, les schémas de migration, l'état nutritionnel, le succès de la reproduction, et, en fin de compte, l'abondance et la structure de la population de certaines espèces. Les phoques associés à la glace, qui dépendent d'un support glaciel pour le repos, la mise bas et la mue, seraient particulièrement affectés par de tels changements. Vu que les diminutions récentes de couverture de glace ont été plus importantes dans l'Arctique sibérien (de 60° E. à 180° E.) que dans la mer de Beaufort et les secteurs occidentaux, on pense que les populations de mammifères marins dans l'Arctique sibérien pourraient être les premières à faire l'expérience de variations géographiques dues au climat ou d'une modification de leur capacité de reproduction causée par des changements chroniques dans l'étendue de glace. Une modification de l'étendue et de la productivité des systèmes de la marge glaciaire pourrait affecter la densité et la distribution de proies associées à la glace importantes pour les mammifères marins, comme la morue arctique Boreogadus saida et les amphipodes vivant en contact avec la glace. Les modèles climatologiques actuels ne sont toutefois pas en mesure de prédire les dynamiques régionales de la glace, les vents, les caractéristiques à mésoéchelle ainsi que les mécanismes de réapprovisionnement en éléments nutritifs, tous éléments que l'on doit connaître pour pouvoir prédire la productivité et la réponse trophique. Il est par conséquent critique que des études à mésoéchelle axées sur les processus identifient les interactions du milieu naturel nécessaires pour maintenir, à des échelles arctiques régionales, une disponibilité de proies et un habitat associé à la glace appropriés aux mammifères marins. Seule une approche intégrée des écosystèmes peut envisager la complexité des facteurs déterminant la productivité et les dynamiques trophiques qui en résultent dans un Arctique plus tempéré. Cette approche, intégrée avec la surveillance d'espèces indicateurs clés (p. ex., la baleine boréale, le phoque annelé et le bélouga), devrait constituer une haute priorité

Cetacean Habitat Selection in the Alaskan Arctic during Summer and Autumn

Ten years (1982-91) of sighting data from aerial surveys offshore of northern Alaska were analyzed to investigate seasonal variability in cetacean habitat selection. Distinct habitats were described for bowhead whales (Balaena mysticetus), white whales (Delphinapterus leucas), and gray whales (Eschrichtius robustus) on the basis of habitat selection ratios calculated for bathymetric and ice cover regimes. In summer, bowheads selected continental slope waters and moderate ice conditions; white whales selected slope and basin waters and moderate to heavy ice conditions; and gray whales selected coastal/shoal waters and open water. In autumn, bowheads selected inner shelf waters and light ice conditions; white whales selected outer shelf and slope waters and moderate to heavy ice; and gray whales selected coastal and shoal/trough habitats in light ice and open water. Habitat differences among species were significant in both seasons (ANOVA F > 28, p < 0.00001). Interseasonal depth and ice cover habitats were significantly different for bowhead whales (p < 0.00002), but not for gray whales (p > 0.35). White whale depth habitat was significantly different between seasons (p < 0.00002), but ice cover habitat was not (p < 0.08). Des données d'observation réalisées sur dix années (1982-1991) grâce à des relevés aériens au large de l'Alaska septentrional ont été analysées dans le cadre de recherches sur la variabilité saisonnière dans la sélection de l'habitat des cétacés. On a décrit des habitats distincts pour la baleine boréale (Balaena mysticetus), la baleine blanche (Delphinapterus leucas) et la baleine grise de Californie (Eschrichtius robustus) en se fondant sur les taux de sélection de l'habitat calculés pour le régime bathymétrique et celui de la couverture de glace. En été, la baleine boréale choisissait les eaux de la pente continentale et des conditions de glace modérée; la baleine blanche choisissait les eaux de la pente continentale et du bassin océanique, et des conditions de glace allant de modérée à épaisse; et la baleine grise choisissait des eaux côtières et de hauts-fonds ainsi que l'eau libre. En automne, la baleine boréale choisissait les eaux intérieures du plateau continental, où se trouvait une faible concentration de glace; la baleine blanche choisissait les eaux à l'extérieur du plateau et sur la pente, ainsi qu'une glace allant de modérée à épaisse; et la baleine grise choisissait des habitats côtiers et de hauts-fonds ou des fossés à faible concentration de glace et à eau libre. Les différences d'habitat entre les espèces étaient importantes durant les deux saisons (ANOVA F > 28, p < 0,00001). D'une saison à une autre, les habitats différaient sensiblement quant à la profondeur et à la couverture de glace pour la baleine boréale (p < 0,00002), mais pas pour la baleine grise (p > 0,35). La profondeur de l'habitat pour la baleine blanche variait sensiblement d'une saison à une autre (p <0,00002), mais pas la couverture de glace (p < 0,08).

The Great Whales: History and Status of Six Species Listed as Endangered Under the U.S. Endangered Species Act of 1973

In the history of whaling from prehistoric to modern times, the large whales, sometimes called the “great whales,” were hunted most heavily owing in part to their corresponding value in oil, meat, and baleen. Regional populations of North Atlantic right whales, Eubalaena glacialis glacialis, were already decimated by 1700, and the North Atlantic gray whale, Eschrichtius robustus, was hunted to extinction by the early 1700’s (Mitchell and Mead1)

U.S. Pacific Marine Mammal Stock Assessments

Under the 1994 amendments to the Marine Mammal Protection Act, the National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service (USFWS) were required to produce stock assessment reports for all marine mammal stocks in waters within the U.S. Exclusive Economic Zone. This document contains the stock assessment reports for the U.S. Pacific marine mammal stocks under NMFS jurisdiction. Marine mammal species which are under the management jurisdiction of the USFWS are not included in this report. A separate report containing background, guidelines for preparation, and .a summary of all stock assessment reports is available from the NMFS Office of Protected Resources. This report was prepared by staff of the Southwest Fisheries Science Center, NMFS and the Alaska Fisheries Science Center, NMFS. The information presented here was compiled primarily from published sources, but additional unpublished information was included where it contributed to the assessments. The authors wish to thanks the members of the Pacific Scientific Review Group for their valuable contributions and constructive criticism: Hannah Bernard, Robin Brown, Mark Fraker, Doyle Hanan, John Heyning, Steve Jeffries, Katherine Ralls, Michael Scott, and Terry Wright. Their comments greatly improved the quality of these reports, We also thanks the Marine Mammal Commission, The Humane Society of the United States, The Marine Mammal Center, The Center for Marine Conservation, and Friends of the Sea Otter for their careful reviews and thoughtful comments. Special thanks to Paul Wade of the Office of Protected Resources for his exhaustive review and comments, which greatly enhanced the consistency and technical quality of the reports. Any ommissions or errors are the sole responsibility of the authors. This is a working document and individual stock assessment reports will be updated as new information becomes available and as changes to marine mammal stocks and fisheries occur; therefore, each stock assessment report is intended to be a stand alone document. The authors solicit any new information or comments which would improve future stock assessment reports. This is Southwest Fisheries Science Center Technical Memorandum NOAA-TM-NMFS-SWFSC- 219, July 1995. 11

Geochemical and Visual Indicators of Hydrothermal Fluid Flow through a Sediment-Hosted Volcanic Ridge in the Central Bransfield Basin (Antarctica)

In the austral summer of 2011 we undertook an investigation of three volcanic highs in the Central Bransfield Basin, Antarctica, in search of hydrothermal activity and associated fauna to assess changes since previous surveys and to evaluate the extent of hydrothermalism in this basin. At Hook Ridge, a submarine volcanic edifice at the eastern end of the basin, anomalies in water column redox potential (Eh) were detected close to the seafloor, unaccompanied by temperature or turbidity anomalies, indicating low-temperature hydrothermal discharge. Seepage was manifested as shimmering water emanating from the sediment and from mineralised structures on the seafloor; recognisable vent endemic fauna were not observed. Pore fluids extracted from Hook Ridge sediment were depleted in chloride, sulfate and magnesium by up to 8% relative to seawater, enriched in lithium, boron and calcium, and had a distinct strontium isotope composition (87Sr/86Sr = 0.708776 at core base) compared with modern seawater (87Sr/86Sr ?0.70918), indicating advection of hydrothermal fluid through sediment at this site. Biogeochemical zonation of redox active species implies significant moderation of the hydrothermal fluid with in situ diagenetic processes. At Middle Sister, the central ridge of the Three Sisters complex located about 100 km southwest of Hook Ridge, small water column Eh anomalies were detected but visual observations of the seafloor and pore fluid profiles provided no evidence of active hydrothermal circulation. At The Axe, located about 50 km southwest of Three Sisters, no water column anomalies in Eh, temperature or turbidity were detected. These observations demonstrate that the temperature anomalies observed in previous surveys are episodic features, and suggest that hydrothermal circulation in the Bransfield Strait is ephemeral in nature and therefore may not support vent biota