Hydrographic Features, Cetaceans and the Foraging of Thick-billed Murres and Other Marine Birds in the Northwestern Barents Sea

The at-sea distribution of thick-billed murres (Uria lomvia) in southeastern Svalbard waters was studied during the summers of 1992, 1993, and 1996. The Storfjordrenna region south of Svalbard was confirmed as an important foraging area for thick-billed murres; murre aggregations were located at distances of 85 to 126 km from the closest breeding colonies. Fish, mainly polar cod (Boreogadus saida), but also capelin (Mallotus villosus), were the main prey found in 16 murres and 3 black-legged kittiwakes (Rissa tridactyla) collected from these aggregations. Murres were seen flying with fish in their beaks at four locations 78 to 102 km away from the colonies. Murre aggregations were associated with frontal zones between cold Arctic waters and warmer Atlantic water, and in areas with strong stratification in salinity at 15-30 m. A positive association was found between the abundance of murres and the occurrence of cetaceans. Murres and other marine birds were often seen near surfacing cetaceans. The most common cetaceans were minke whales (Balaenoptera acutorostrata) and white-beaked dolphins (Lagenorhynchus albirostris).Durant les étés de 1992, 1993 et 1996, on a étudié la distribution en mer de la marmette de Brünnich (Uria lomvia) dans les eaux du sud-est du Svalbard. La région Storfjordrenna au sud du Svalbard a été confirmée comme une zone importante de collecte pour la marmette de Brünnich; des concentrations de marmettes étaient situées à des distances allant de 85 à 126 km des colonies nicheuses les plus proches. Le poisson, en particulier la morue polaire (Boreogadus saida), mais aussi le capelan (Mallotus villosus), était la proie principale trouvée chez 16 marmettes et 3 mouettes tridactyles (Rissa tridactyla) prélevées dans ces concentrations. On a vu les marmettes voler avec du poisson dans leur bec à quatre endroits éloignés de 78 à 102 km des colonies. Les concentrations de marmettes étaient associées à des zones frontales entre les eaux froides de l'Arctique et l'eau plus chaude de l'Atlantique, et dans des régions ayant une forte stratification dans la salinité à une profondeur de 15 à 30 m. On a trouvé qu'il existait une association positive entre l'abondance des marmettes et la présence des cétacés. On voyait souvent les marmettes et d'autres oiseaux marins près des cétacés qui faisaient surface. Les cétacés les plus communs étaient les petits rorquals (Balaenoptera acutorostrata) et les dauphins à nez blanc (Lagenorhynchus albirostris)

Jellyfish, Forage Fish, and the World's Major Fisherie

A majority of the world’s largest net-based fisheries target planktivorous forage fish that serve as a critical trophic link between the plankton and upper-level consumers such as large predatory fishes, seabirds, and marine mammals. Because the plankton production that drives forage fish also drives jellyfish production, these taxa often overlap in space, time, and diet in coastal ecosystems. This overlap likely leads to predatory and competitive interactions, as jellyfish are effective predators of fish early life stages and zooplankton. The trophic interplay between these groups is made more complex by the harvest of forage fish, which presumably releases jellyfish from competition and is hypothesized to lead to an increase in their production. To understand the role forage fish and jellyfish play as alternate energy transfer pathways in coastal ecosystems, we explore how functional group productivity is altered in three oceanographically distinct ecosystems when jellyfish are abundant and when fish harvest rates are reduced using ecosystem modeling. We propose that ecosystem-based fishery management approaches to forage fish stocks include the use of jellyfish as an independent, empirical “ecosystem health” indicator.Fil: Robinson, Kelly L. State University of Oregon; Estados UnidosFil: Ruzicka, James J.. State University of Oregon; Estados UnidosFil: Decker, Mary Beth. University of Yale; Estados UnidosFil: Brodeur, RIchard. NOAA Northwest Fisheries Science Center; Estados UnidosFil: Hernandez, Frank. University Of Mississippi; Estados UnidosFil: Quiñones Dávila, Javier. Instituto del Mar del Perú; PerúFil: Acha, Eduardo Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata; ArgentinaFil: Uye, Shin-ichi. Graduate School of Biosphere Science; JapónFil: Mianzan, Hermes Walter. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata; ArgentinaFil: Graham, William M.. The University of Southern Mississippi; Estados Unido

Questioning the rise of gelatinous zooplankton in the World's oceans

During the past several decades, high numbers of gelatinous zooplankton species have been reported in many estuarine and coastal ecosystems. Coupled with media-driven public perception, a paradigm has evolved in which the global ocean ecosystems are thought to be heading toward being dominated by “nuisance” jellyfish. We question this current paradigm by presenting a broad overview of gelatinous zooplankton in a historicalcontext to develop the hypothesis that population changes reflect the human-mediated alteration of global ocean ecosystems. To this end, we synthesize information related to the evolutionary context of contemporary gelatinous zooplankton blooms, the human frame of reference forchanges in gelatinous zooplankton populations, and whether sufficient data are available to have established the paradigm. We conclude that the current paradigm in which it is believed that there has been a global increase in gelatinous zooplankton is unsubstantiated, and we develop a strategy for addressing the critical questions about long-term, human-related changes in the sea as they relate to gelatinous zooplankton blooms

CiannelliLorenzoCEOASLinkingChangesEastern_SupplementaryMaterial.pdf

The Bering Sea ecosystem has experienced significant climatic and biological shifts over the past 3 decades, including temporal and spatial fluctuations of jellyfish biomass. Jellyfish are important predators and competitors of fish; thus, it is critical to understand the effects of environmental factors on their population dynamics. We explored the effects of ocean bottom temperatures and circulation on jellyfish populations using a non-parametric, nonlinear multiple time series analysis of a 23 yr dataset. The study area was divided into 3 subregions that reflected distinct jellyfish catches and distributions. Aggregations and the influence of temperature and circulation on jellyfish biomass were found to differ in each of the 3 subregions. The northern region biomass was affected by central biomass, mediated by the strength of advection from the central region. In both the northern and central regions, current-year biomass was associated with lag-1 biomass, but was mediated by local bottom temperatures (colder temperatures strengthened the relationship with lag-1 biomass). However, in the central region, this relationship held only for the period after 1997. Prior to 1997, advection from the southern region drove central region biomass, suggesting that the primary source of jellyfish biomass to the central eastern Bering Sea shelf changed, coming from the southern shelf before 1997 and from the central shelf after 1997. The southern jellyfish biomass was affected by only the lag-1 southern jellyfish biomass. Transport from the south may have seeded the central region in the early 1990s, but once established, jellyfish polyp populations near islands in the central region may have supplied the area with medusae in the late 1990s.Keywords: Climate change, Scyphomedusae, Time series, Biophysical condition

Reconstructing Source-Sink Dynamics in a Population with a Pelagic Dispersal Phase

<div><p>For many organisms, the reconstruction of source-sink dynamics is hampered by limited knowledge of the spatial assemblage of either the source or sink components or lack of information on the strength of the linkage for any source-sink pair. In the case of marine species with a pelagic dispersal phase, these problems may be mitigated through the use of particle drift simulations based on an ocean circulation model. However, when simulated particle trajectories do not intersect sampling sites, the corroboration of model drift simulations with field data is hampered. Here, we apply a new statistical approach for reconstructing source-sink dynamics that overcomes the aforementioned problems. Our research is motivated by the need for understanding observed changes in jellyfish distributions in the eastern Bering Sea since 1990. By contrasting the source-sink dynamics reconstructed with data from the pre-1990 period with that from the post-1990 period, it appears that changes in jellyfish distribution resulted from the combined effects of higher jellyfish productivity and longer dispersal of jellyfish resulting from a shift in the ocean circulation starting in 1991. A sensitivity analysis suggests that the source-sink reconstruction is robust to typical systematic and random errors in the ocean circulation model driving the particle drift simulations. The jellyfish analysis illustrates that new insights can be gained by studying structural changes in source-sink dynamics. The proposed approach is applicable for the spatial source-sink reconstruction of other species and even abiotic processes, such as sediment transport.</p></div