Article

Mass mortality of Short-tailed Shearwaters in the South-Eastern Bering Sea during summer 1997

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Abstract

During summer 1997, hundreds of thousands of emaciated short-tailed shearwaters (Puffinus tenuirostris) died in the south-eastern Bering Sea. Using strip transect methodology, we documented the distribution and abundance of short-tailed shearwaters during cruises conducted prior to, during, and after the die-off, as well as the distributions and abundances of floating carcasses. The distributions and abundances of short-tailed shearwaters in 1997 were similar to those found during the 1970s and early 1980s. In August–September 1997, we observed 163 floating shearwater carcasses, most of which were between St Paul Island and Nunivak Island. We estimated ≈ 190 000 carcasses were afloat in the study area, about 11% of the surveyed population. Between spring (June) and autumn (August/September), mean net body mass of shearwaters decreased by 19%, mean pectoral muscle mass decreased by 14%, and mean percentage body lipid content decreased by 46%, from 15.6% in spring to 8.4% in autumn. Compared with spring, short-tailed shearwater diets broadened in autumn 1997, to include, in addition to adult euphausiids Thysanoessa raschii, juveniles of T. inermis, T. raschii and T. spinifera, crab megalops, fish and squid. We discuss how the ecosystem anomalies in the south-eastern Bering Sea during spring and summer 1997 relate to the mortality event and suggest possible implications of long-term climate change for populations of apex predators in the south-eastern Bering Sea.

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... In the late 1990s, the southeastern Bering Sea exhibited a number of anomalous conditions, including unusually warm surface temperatures in 1997 and a recurring coccolithophore bloom that increased turbidity in the water column (Vance et al., 1998;Hunt et al., 1999;Napp and Hunt, 2001;Stabeno et al., 2001;Stockwell et al., 2001). In the Bering Sea in fall 1997, hundreds of thousands of short-tailed shearwaters starved, and in fall 1998, short-tailed shearwaters were emaciated, though moribund birds were not encountered (Baduini, 2000;Baduini et al., 2001a). In spring 1999, short-tailed shearwaters in Bristol Bay had body masses intermediate between those in 1997 and 1998, and in summer 1999, body masses were greater than those measured in either fall 1997 or fall 1998 (Baduini et al., 2001b). ...
... In spring 1999, short-tailed shearwaters in Bristol Bay had body masses intermediate between those in 1997 and 1998, and in summer 1999, body masses were greater than those measured in either fall 1997 or fall 1998 (Baduini et al., 2001b). In comparison to past studies of short-tailed shearwater foraging ecology in the southeastern Bering Sea, in August and September 1997, short-tailed shearwater diets included a wider variety of prey than expected (Baduini et al., 2001a). Baduini et al. hypothesized that the more diverse diets than expected were a response to the unavailability of adult euphausiids, the previously dominant prey of short-tailed shearwaters over the middle and inner shelf domains. ...
... For the most part, we lack sufficient data, particularly the historical data, necessary to test these hypotheses. Elsewhere (Baduini et al., 2001a), we have argued that the warm surface water in fall 1997 may have inhibited surface swarming of adult euphausiids. While this explanation may be relevant for 1997, it is not adequate to explain why there was an apparent lack of nearsurface swarms in 1998 and 1999, when surface temperatures were cooler. ...
Article
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In the late 1990s, the southeastern Bering Sea exhibited a number of anomalous conditions, including a major die-off of short-tailed shearwaters (Puffinus tenuirostris), a trans-equatorial migrant that constitutes a major portion of the marine bird biomass in the southeastern Bering Sea. As part of a larger study of the ecological role of the inner or structural front over the southeastern Bering Sea shelf, in 1997–1999, we collected short-tailed shearwaters to determine diet composition. In spring 1997, we found that short-tailed shearwaters were consuming predominately the euphausiid Thysanoessa raschii, a diet expected on the basis of past studies. However, in subsequent years, short-tailed shearwater diets in spring contained increasingly larger proportions of fish, in particular, sandlance (Ammodytes hexapterus), as well as other species of euphausiids (T. inermis in 1999). In summer and fall collections, short-tailed shearwater diets were more varied than in spring, and included both fish (age-0 gadids, 21–35% by weight) and a wider variety of euphausiid species (T. inermis and T. spinifera). In summer and fall, crab zoea (August 1998) and copepods (August 1999) were eaten by shearwaters collected while feeding within the inner front. Diets in 1997–1999 were broader than those found in previous studies of short-tailed shearwaters over the inner shelf and Bristol Bay, which had documented diets composed almost solely of T. raschii. Our data are consistent with the hypothesis that euphausiids were less available to short-tailed shearwaters foraging over the middle and coastal domains of the southeastern Bering Sea in 1997–1999 than has previously been true. Our results are also consistent with hypothesis that the inner front can affect the availability of prey to shearwaters.
... The proportion of zooplankton consumed at the front decreased from summer 1997 to summer 1999, while the consumption of sandlance increased in this area. Calm weather conditions (Stabeno et al. 2001, Kachel et al. 2002 and water turbidity due to the presence of a coccolithophore bloom (Vance et al. 1998, Stockwell et al. 2001 contributed to high mortality of shearwaters in 1997 (Baduini et al. 2001a). Light attenuation resulting from the coccolithophore bloom probably had a negligible influence on underwater foraging; however, greater turbidity and backscatter of light may have impaired the birds' ability to locate prey from the air (Lovvorn et al. 2001), thus increasing their in-flight energy demand (Baduini et al. 2001a). ...
... Calm weather conditions (Stabeno et al. 2001, Kachel et al. 2002 and water turbidity due to the presence of a coccolithophore bloom (Vance et al. 1998, Stockwell et al. 2001 contributed to high mortality of shearwaters in 1997 (Baduini et al. 2001a). Light attenuation resulting from the coccolithophore bloom probably had a negligible influence on underwater foraging; however, greater turbidity and backscatter of light may have impaired the birds' ability to locate prey from the air (Lovvorn et al. 2001), thus increasing their in-flight energy demand (Baduini et al. 2001a). Our results support the idea that birds may not be able to forage successfully inside a coccolitophore bloom even when prey is readily available in the area. ...
... In summer 1998, shearwaters were feeding on euphausiids, and more nutrients were available to enhance production at the inner front; however, we did not find more birds and flocks of shearwaters in this area. Stormier conditions (Stabeno et al. 2001, Kachel et al. 2002 probably decreased energy demand for flight in 1998, but the coccolithophore bloom was still there , reducing their ability to find prey (Baduini et al. 2001a). There was but a minor die-off of shearwaters in 1998 (Hyrenbach et al. 2001), even though their overall body condition was lower than in 1997 (Baduini et al. 2001b). ...
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We examined the hypothesis that short-tailed shearwaters Puffinus tenuirostris aggregate to forage at the inner front of the SE Bering Sea because of enhanced production there. We tested this hypothesis by comparing primary production, the distribution of euphausiids and the distribution of shearwaters relative to the front during late spring and late summer/early fall of 1997, 1998 and 1999. We found enhanced primary production at the front and offshore of the front during summer but not during spring. Primary production varied between seasons and years. Major differences were related to anomalous conditions in 1997 and 1998. The density of euphausiids was higher at the front and offshore of the front during summer, but there were no differences among regions during spring. Foraging shearwaters aggregated in high densities at the front during summer, but foraged close to shore during spring. At the front, shearwaters foraged on euphausiids Thysanoessa raschii and T. inermis as expected, and on copepods that accumulated in the area. The proportion of zooplankton consumed at the front decreased from summer 1997 to summer 1999, while consumption of sandlance Ammodytes hexapterus at this feature increased. Our results show that, during summer, the inner front supports aggregations of euphausiids and their seabird predators. The means by which the frontal system supports enhanced production and the subsequent trophic transfers is dependent on the availability of nutrients at depth in the frontal region and the aggregation of small zooplankton organisms in this feature.
... Although this foraging strategy most likely evolved to utilize the timing in peak availability of prey resources, which alternates seasonally between the northern and southern hemispheres, shearwaters occasionally starve by the thousands while adhering to this strategy (Douglas & Setton 1955, Serventy 1967, Oka & Maruyama 1986. While short-tailed shearwaters were being studied along the inner frontal region of the southeastern Bering Sea in 1997, a large-scale mortality event occurred (July to September; Baduini et al. 2001). Large scale die-offs of shearwaters are infrequent in the Bering Sea because this is a highly productive area, with C fixation of ~200 mg m -2 yr -1 on the shelf (McRoy et al. 1986) and usually has abundant prey resources of euphausiids and fish. ...
... Few studies of birds have been able to show severe nutritional stress in a natural setting (Owen & Cook 1977, Jenni-Eiermann & Schifferli 1989, Fournier & Hines 1994, Jeske et al. 1994, Lovvorn 1994, and few have determined the relation between lipid and protein mobilization during starvation. The observed dieoff of short-tailed shearwaters in the southeastern Bering Sea in 1997 was unusual not only for its magnitude of ~200 000 individuals and up to 11% of the total population (live and dead shearwaters surveyed during fall 1997) but also for its timing and location (Baduini et al. 2001). Most major mortality events of short-tailed shearwaters occurred where the transequatorial migrations terminate. ...
... Usually, the diet of short-tailed shearwaters in the southeastern Bering Sea is dominated by adult euphausiids, primarily Thysanoessa raschii (Hunt et al. 1996, Ogi 1980. A lack of euphausiids in nearshore surface waters or a shift in their horizontal and vertical distribution in 1997 may have made it difficult for short-tailed shearwaters to obtain sufficient resources (Baduini et al. 2001). In 1997 and 1998 a shift was observed in the diet of shorttailed shearwaters from primarily a euphausiid diet in spring, to an almost complete diet of fish, juvenile pollock, and sandlance Ammodytes hexapterus (Hunt et al. in press, C. Baduini pers. ...
Article
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Short-tailed shearwaters Puffinus tenuirostris migrate annually from breeding areas in southeast Australia and Tasmania to the Bering Sea to feed on abundant prey aggregations, mainly euphausiids. Occasionally thousands of shearwaters die of starvation en route, within, or on return from the Bering Sea. Collection of live and dead shearwaters in the southeastern Bering Sea in 1997, 1998, and 1999 allowed us to measure seasonal changes in energy reserves during a major mortality event. As birds lost body mass, lipid mass initially decreased faster than that of pectoralis muscle, but loss of pectoralis mass increased markedly at a body mass around 500 g when lipids were almost depleted (∼33 g remaining). Death occurred as body mass approached 426 g. Individuals near this body mass had lipid values permitting estimated flight ranges of 140 to 400 km, a range less than that potentially covered in 1 d by shearwaters searching for prey (440 to 1124 km d-1). Seasonal differences in body composition were most striking among body and bone marrow lipid contents, with the lowest values occurring during the die-off in fall 1997 and in fall 1998. The lack of shearwater mortality in fall 1998 may have resulted from more consistent winds that decreased flight costs and from greater availability of alternative fish prey. Our data allow estimates of usable energy stores and flight ranges based on lipid reserves in short-tailed shearwaters. Estimated flight ranges suggest that if feeding conditions are poor near Japan or near other termination points of the transequatorial migration routes shearwaters may have few reserves available to support foraging for food and starvation events may occur. Our findings suggest how their energetic strategies and migration are shaped by seasonal and annual variability of prey during transglobal movements of short-tailed shearwaters between oceanic regions.
... Similarly, the different phases of PDO (i.e. warm and cool phase) are strongly linked to variations in SST, which have also been shown to influence the distribution of zooplankton in the water column (Baduini et al., 2001;Coyle et al., 2008;Jin et al., 2009;Bond et al., 2011). This could potentially influence prey availability to STSH, resulting in annual variations in the body mass and breeding participation of migrating birds arriving at the Furneaux Island Group. ...
... The trade winds weaken during ENSO, and warm surface water supresses the thermocline and nutrient upwelling, decreasing primary production, with repercussions throughout the food chain (Schreiber and Schreiber, 1984;Jenouvrier, 2013). During these events, adult seabirds may face starvation as food resources become scarce and there is a reduced capacity to replenish body reserves (Schreiber and Schreiber, 1984;Baduini et al., 2001). ...
Article
Biotic responses to large-scale climate processes are scale-dependant and can influence population trajectories of highly migratory species such as short-tailed shearwaters Ardenna tenuirostris. In this study, we quantified changes in climate, measured through large-scale climate indices (i.e. Northern Pacific Index, Pacific Decadal Oscillation, El Niño–Southern Oscillation and Southern Annular Mode) and local weather conditions (i.e. rainfall) on the breeding performance of short-tailed shearwaters at four of their breeding colonies within the Furneaux Island Group, Tasmania, Australia, from 2010 to 2018. There was inter-colony variability in adult body mass and breeding participation, which were influenced by climate conditions in the preceding year. In contrast, breeding success was influenced by climate conditions in the preceding three to four months and by local weather conditions at the time of breeding. These findings demonstrate that variation in the breeding performance of short-tailed shearwaters are explained both by large-scale climate indices and local environmental conditions. The outcomes of this study provide a better understanding of the environmental factors affecting short-tailed shearwaters.
... This pattern was strongly influenced by seasonal variability in the numbers of the most abundant family observedshearwaters (Procellariidae). Shearwaters were also found to be the most numerous seabirds recorded in previous studies in coastal south-eastern Australian waters (Dann et al., 2003;Gorta et al., 2019), with peak numbers occurring in spring and summer linked to breeding migrations to this region (Weimerskirch & Cherel, 1998;Baduini et al., 2001;Dann et al., 2003). ...
... entire state and multiple years) to capture potentially important variability in seabird interactions with the fishery. For example, interannual variation in environmental conditions and food availability during the southward shearwater migration to this region (e.g.Baduini et al., 2001; ...
Article
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1. Bycatch in fishing gear is a threat to the conservation of seabird populations globally. Factors affecting interactions with commercial fisheries are well documented; however, little comparable information exists for recreational fisheries. High participation rates in many recreational fisheries globally mean that interactions with seabirds may have population-level impacts. 2. This study specifically assessed factors affecting seabird interactions with a recreational hook-and-line fishery in New South Wales (NSW), Australia. Observers on 'for hire' nearshore charter vessels collected data on seabird abundance, interactions and various fishing and environmental variables which could affect the numbers of seabirds in attendance at vessels. 3. In 2017/18, observers were present on 135 fishing trips spanning $33-36 S off coastal NSW recording 3,183 seabirds, including 10 species from seven families. The majority consisted of shearwaters (Procellariidae; 76%), albatrosses (Diomedeidae; 8%) and gulls/terns (Laridae; 10%), including several species of conservation concern. 4. Significant seasonal variation in the abundances of the three main seabird families were recorded; however, none of the fishing or environmental variables influenced abundances of seabirds (except for the positive effect of inclement weather on shearwaters). 5. Eleven direct interactions and a single incidence of (shearwater) bycatch were recorded in over 630 h of observed fishing (1.74 and 0.16 per 100 h fishing, respectively); these rates were likely due to the active fishing methods used which allows fisher behaviour to minimize interactions. 6. Despite this, these rates indicate that the nearshore charter fishery does have the potential to present a threat to the conservation of seabird populations in this region. Furthermore, globally, for regions with high recreational fishing participation rates, increased and ongoing monitoring of seabird interactions with recreational fisheries is required. 7. This study also highlights that such interactions are likely to be rare events and future monitoring may require utilization of existing broadscale recreational
... As abundant, visible, upper-trophic organisms, seabirds have been proposed as indicators of marine ecosystem shifts due to climate, with documented effects of climate variability on both reproduction [28][29][30] and adult survival [31][32][33]. Large-scale shifts in climate have been punctuated by large mortality events of marine birds [34][35][36][37][38]. These "massive mortality events" (MME)-defined as catastrophic, but often short-lived, periods of elevated mortalitycan affect substantial proportions of a population, occasionally with long-term consequences to population size [39]. ...
... Mass mortality events of marine birds are often linked to food stress [38,90,91]. Within the Bering Sea, large-scale mortality events in 1983 and 1997 were linked to changes in prey phenology (primarily zooplankton), abundance and composition, as a result of ocean-climate anomalies [1,34,36]. Massive shifts in North Pacific marine ecosystems have been observed from 2013 to 2017 as a result of anomalous atmospheric conditions [92], including the sustained presence of the northeast Pacific marine heatwave [10]. Thus far, these shifts have been linked directly to two seabird MMEs [38,45]. ...
Article
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Mass mortality events are increasing in frequency and magnitude, potentially linked with ongoing climate change. In October 2016 through January 2017, St. Paul Island, Bering Sea, Alaska, experienced a mortality event of alcids (family: Alcidae), with over 350 carcasses recovered. Almost three-quarters of the carcasses were unscavenged, a rate much higher than in baseline surveys (17%), suggesting ongoing deposition and elevated mortality around St Paul over a 2–3 month period. Based on the observation that carcasses were not observed on the neighboring island of St. George, we bounded the at-sea distribution of moribund birds, and estimated all species mortality at 3,150 to 8,800 birds. The event was particularly anomalous given the late fall/winter timing when low numbers of beached birds are typical. In addition, the predominance of Tufted puffins (Fratercula cirrhata, 79% of carcass finds) and Crested auklets (Aethia cristatella, 11% of carcass finds) was unusual, as these species are nearly absent from long-term baseline surveys. Collected specimens were severely emaciated, suggesting starvation as the ultimate cause of mortality. The majority (95%, N = 245) of Tufted puffins were adults regrowing flight feathers, indicating a potential contribution of molt stress. Immediately prior to this event, shifts in zooplankton community composition and in forage fish distribution and energy density were documented in the eastern Bering Sea following a period of elevated sea surface temperatures, evidence cumulatively suggestive of a bottom-up shift in seabird prey availability. We posit that shifts in prey composition and/or distribution, combined with the onset of molt, resulted in this mortality event.
... Anomalous cloud-free conditions, increased solar heating, decreased onshore transport of slope water and reduced number of energetic storms all acting in consonance during that year, contributed to the formation of a warm (~12 o C) and stable water column on the shelf in which few nutrients remained to support diatoms (Egge and Aksnes, 1992). These conditions caused a dramatic switch in phytoplankton populations, with profound effects on the rest of the food chain (Baduini et al., 2001;Stockwell et al., 2001). ...
... The paucity of nutrients in the upper layer of the two layered middle shelf waters was in all likelihood responsible for the termination of the diatom bloom. The presence of cryptophytes and chlorophytes in the sinking bloom and the relative increase in prasinophytes at the sea surface suggest a pattern of succession of phytoplankton that is consistent with a transition from colder nutrient rich waters to warmer nutrient impoverished waters (Baduini et al., 2001;Stockwell et al., 2001;Boerse et al., 2003). In general, nutrient poor waters at the surface were associated with cryptophytes, haptophytes and prasinophytes which accounted for a significant fraction of the low phytoplankton biomass. ...
Article
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Spectral fluorescence measurements of phytoplankton chlorophyll a (Chl a), phytoplankton phycobilipigments and variable fluorescence (Fv/Fm), are utilized with High Performance Liquid Chromatography (HPLC) estimates of phytoplankton pigments and microscopic cells counts to construct a comprehensive picture of summer-time phytoplankton communities and their photosynthetic competency in the eastern Bering Sea shelf. Although the Bering Sea was ice-free during our study, the exceptionally cold winter that preceded the summer of 2008 when our cruise took place, facilitated the formation of a “Cold Pool” (<2 °C) and its entrapment at depth in the northern middle shelf. The presence of a strong pycnocline over the entire middle and outer shelves restricted inorganic nutrient fluxes into the surface waters resulting in phytoplankton populations that were photo-physiologically stressed due to nutrient limitation. Elevated Chl a concentrations recorded in the Green Belt along the shelf edge of the Bering Sea, were due to Phaeocystis pouchetii and nano-sized cryptophytes. Although inorganic nutrients were not limiting in the Green Belt, Fv/Fm values were low in all probability due to iron limitation. Phytoplankton communities in the low biomass surface waters of the middle shelf were comprised of prasinophytes, haptophytes, cryptophytes and diatoms. In the northern part of the middle shelf, a sinking bloom made up of the centric diatoms Chaeotoceros socialis, Thalassiosira nordenskioeldii and Porosira glacialis was located above the Cold Pool. The high biomass associated with this senescent bloom and its accretion above the pycnocline, suggests that the Cold Pool acts as a barrier, preventing sinking phytoplankton from reaching the bottom where they can become available to benthic organisms. We further posit that if summer-time storms are not energetic enough and the Cold Pool is not eroded, its presence facilitates the transfer of the large spring phytoplankton bloom to the pelagic ecosystem.
... Recently, this region has undergone large biological/environmental changes ( Jin et al., 2009;Stabeno et al., 2010). In 1997, a coccolithophore (Emiliania huxleyi) bloom was observed ( Napp and Hunt, 2001;Stockwell et al., 2001;Sukhanova and Flint, 1998), and mass mortality of short-tailed shearwaters (Puffinus tenuirostris) occurred near the Pribilof Islands ( Baduini et al., 2001). In 1998, a climate regime shift was reported ( McFarlane et al., 2000), and the biomass of the jellyfish Chrysaora melanaster was observed to peak ( Brodeur et al., 2008). ...
... During the 1997 El Niño/Southern Oscillation (ENSO) event, there were anomalous atmospheric conditions over the southeastern Bering Sea shelf ( Overland et al., 2001), a warm surface layer, a bloom of the coccolithophorid E. huxleyi ( Sukhanova and Flint, 1998) and mass mortality of short-tailed shearwaters (P. tenuirostris) ( Baduini et al., 2001). Short-tailed shearwaters prey on large zooplankton, especially adult euphausiids ( Hunt et al., 1996), and the starvation of shearwaters that occurred during the summer of 1997 may have been due to low densities of adult euphausiids ( Stockwell et al., 2001) or difficulty in finding prey patches due to low water transparency caused by the coccolithophore blooms ( Lovvorn et al., 2001). ...
Article
On the southeastern Bering Sea shelf, mesozooplankton plays an important role in material transfer between primary producers and fisheries resources. The biomass of mesozooplankton in this region is known to vary annually, but little is known about annual changes in community structure and species composition. In the present study, regional and long-term changes in abundance, biomass and community structure of copepods and chaetognaths on the shelf were evaluated based on NORPAC net samples collected during summers of 1994-2009. During the study period, regime shifts occurred from high interannual variability regime (1994-1999) to low interannual variability regime with high temperature (2000-2005), then to a low interannual variability regime with low temperature (2007-2009). A total of 24 calanoid copepod species belonging to 21 genera were identified from samples. Copepod abundance ranged from 150 to 834,486 inds. m-2, was greatest on the Middle shelf, and was higher in cold years, than in warm years. Copepod biomass ranged from 0.013 to 150 g DM m-2, and was also higher in cold years than in warm years. Based on the results of cluster analysis, the copepod community was divided into six groups (A-F). The regional and interannual distributions of each group were distinct. Interannual changes in abundance of the dominant copepod on the Outer shelf and Middle shelf were highly significant (p<0.0001), and their abundances were negatively correlated with temperature and salinity. Interannual changes in copepod community that occurred between cold and warm years are thought to have been caused by differences in the magnitude and timing of the spring phytoplankton bloom between the two regimes. Abundance and biomass of the chaetognath Parasagitta elegans ranged from 30 to 15,180 inds. m-2 and from 11 to 1559 mg DM m-2, respectively. Chaetognath abundance was significantly correlated with the abundance of the dominant copepods (p<0.0001). Differences in cold and warm years may also affect recruitment of walleye pollock. We conclude that on the southeastern Bering Sea shelf, the magnitude and timing of primary production, which is related to climate change, may significantly affect how it is transferred through the food web.
... include a large decrease of deep nitrate concentrations This further affects the growth and survival of larval during June 1997 [27,37], an unprecedented bloom of and juvenile fish and recruitment of large piscivorous coccolithophores (Emiliania huxleyi) beginning in July fish [8,22]. The location of the Aleutian Low is closely 1997 [12,38], low retums of sockeye salmon (Oncorhyn related to large-scale atmospheric variations, such as chus nerka) to Bristol Bay during 1997 and 1998 [12] the El Nino/Southem Oscillation (ENSO) and the (recuning in 1998 and 1999 [J 2]), and a massive mortauty Pacific DecadaJ Oscillation (PDO) of the N01th Pacific of short-tailed shearwaters during [997 [3]. sea surface temperature (20, 34J. ...
... The fluorescence data from the mooring station indicated the occurrence of an ice related bloom in late April at the M2 site over the mid dle shelf [34], which presumably resulted in an exten sive utilization of nutrients in the surface layer during early May 1997 In the early spring of 1998 and 1999, an early retreat of the sea ice (February) and strong wind mixing prevented the development of density driven stratification, which may cause high nitrate con centrations (Figs. [2][3][4][5]. Unfavorable physical condi tions were responsible for the Lack of an obvious spring bloom. The fluorescence data from mooring station 2 clearly show no apparent increase in the early spring of 1998 and 1999, except for an increase in early March 1999 [13]. ...
Article
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The southeastern Bering Sea shelf experienced dramatic changes in Jarge-scale climate conditions and local weather conditions during 1997,1998, and 1999. We investigated the changes in the nutrient distri­ bution and primary production in response to the changing physical condition over the shelf region. The tem­ perature and salinity profiles showed that sea ice conditions and wind-mixing events strongly influenced the hydrographic conditions. BiologicaJ utilization and physical process, such as hOlizontaJ advection below the pycnocline, played an important role in the distribution and interannual variation of nutrients. The distribution of temperature and ammonium across the shelf suggested that there was offshore transport of the middle shelf water at mid-depths over the outer shelf, which may export materials from the middle shelf to the outer shelf and shelf break. The distribution of the carbon and nitrogen uptake rates showed large interannual differences due to variations in t.he development of stratification and nutrient concentrations that resulted from variations in the sea ice dynamics and wind mixing over the shelf region. The occurrence of a high amount of ammonium in the early spring may affect the nitrate utilization and result in an increase of the total primary production.
... , shifts in recruitment of groundfish and salmon species (Walther et al., 2002;Grebmeier et al., 2006), massive seabird die-offs (Baduini et al., 2001), and shifts in distribution and abundance of marine mammal species (Kovacs et al., 2011). ...
Article
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Alaska’s Bering Sea ecosystem is changing rapidly, and the people and animals living in this area must quickly adapt. The US National Oceanic and Atmospheric Administration’s Ecosystems and Fisheries-Oceanography Coordinated Investigations program has been monitoring the Bering Sea ecosystem for more than 20 years with a multidisciplinary toolbox of biophysical moorings, ship-based operations, and satellite-tracked drifters. Physical and biological time-series data collected from a series of three-to-seven-year programs have supported foundational ecosystem science and provided great insight into how climate can influence fisheries recruitment. In this article, we highlight the major discoveries made during nearly two decades of observations in the Bering Sea.
... Most seabirds are migratory or dispersive during the nonbreeding season and are dependent upon the availability of prey resources while on migration or away from nesting sites. During the non-breeding season many seabirds moult and may lose 50 % of their pre-moult body mass while in moult (Baduini et al. 2001;Cherubini et al. 1996;Knox 2007). The timing of moult has been shown to influence breeding timing and to be influenced by it (Paredes et al. 2002;Wolfaardt et al. 2009a). ...
Article
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Seabirds are one of the most threatened groups of birds globally and, overall, their conservation status is deteriorating rapidly. Southern hemisphere countries are over-represented in the number of species of conservation concern yet long-term phenological data on seabirds in the southern hemisphere is limited. A better understanding of the implications of changes in the marine and terrestrial environments to seabird species is required in order to improve their management and conservation status. Here we conducted a meta-analysis of the phenological drivers and trends among southern hemisphere seabirds. Overall there was a general trend towards later phenological events over time (34 % of all data series, N = 47; 67 % of all significant trends), though this varied by taxa and location. The strongest trends towards later events were for seabirds breeding in Australia, the Laridae (gulls, noddies, terns) and migratory southern polar seabirds. In contrast, earlier phenologies were more often observed for the Spheniscidae (penguins) and for other seabirds breeding in the Antarctic and subantarctic. Phenological changes were most often associated with changes in oceanographic conditions, with sea-ice playing an important role for more southerly species. For some species in some locations, such as the Little Penguin Eudyptula minor in south-eastern Australia, warmer oceans projected under various climate change scenarios are expected to correspond to increased seabird productivity, manifested through earlier breeding, heavier chicks, an increased chance of double brooding, at least in the short-term.
... Climatic change has had both negative and positive effects on seabirds (Veit et al. 1996) depending on species' location, life history and ecology. Climatic change has had reported effects on foraging success (Erwin and Congdon 2007), chick growth (Hedd et al. 2002), breeding success (Frederiksen et al. 2004a;, juvenile/adult survival (Baduini et al. 2001;Votier et al. 2004;Sandvik et al. 2005;Bertram et al. 2005;Barbraud et al. 2008;Jenouvrier et al. 2009a) and population sizes of seabirds (Thompson and Ollason 2001 In this chapter, only the effects of climatic variation on seabird breeding success and population size will be considered, as effects of climatic variation on parameters such as foraging success and chick growth do not necessarily result in changes in seabird demographics or distribution. For example, in Alaska, decreased availability of food during an ENSO event resulted in decreased chick growth and earlier fledging of horned puffins (Fratercula corniculata) but had no effect on fledging success (Harding et al. 2003). ...
Research
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This file contains the contents, references, general introduction and discussion. Please refer to the individual files for the chapters. For chapter 3 "How does climatic variation affect seabird population sizes?" please refer to Russell et al. 2015 in Diversity and Distributions.
... The biomass of zooplankton and micro-nekton are infl uenced not only by physical parameters but also by animals at higher trophic levels such as anadromous salmon, non-salmonid fi shes, and birds (Baduini et al. 2001;Davis et al. 2009;Coyle et al. 2011). Shiomoto et al. (1997) reported that year-to-year variation in pink salmon abundance plays a large part in controlling the summer biomass of macrozooplankton and phytoplankton in the central subarctic North Pacifi c. Kaga et al. (2013) reported that analysis of stomach contents of chum salmon indicated non-crustacean zooplankton (appendicularians, chaetognaths, hydrozoans, polychaetes and pteropods) were consumed at a higher frequency when pink salmon were more abundant. ...
... During anomalous weather and oceanic conditions in the Bering Sea in 1997 and 1998, the shearwaters failed to accumulate sufficient energy, storing only a mean of 31 g and 45 g body fat by each North Pacific autumn, respectively. They also had lighter pectoral masses (Baduini et al. 2001a) at the time when the shearwaters usually commence their southward migration to Australia. In the North Pacific autumn of 1997, up to 200 000 individuals were estimated to have starved to death (Baduini et al. 2001 b). ...
... , shifts in recruitment of groundfish and salmon species (Walther et al., 2002;Grebmeier et al., 2006), massive seabird die-offs (Baduini et al., 2001), and shifts in distribution and abundance of marine mammal species (Kovacs et al., 2011). ...
... Although most euphausiids occur at depths of more than 100 m in daytime, during the summer months members of the genus Thysanoessa may form daytime near-surface and surface swarms for mating (Hanamura et al. 1989). It has been shown that the summertime near-surface foraging of shearwaters may be associated with euphausiid mating swarms (Hunt et al. 1996, Baduini et al. 2001). Baleen whales have been shown to feed on surface swarms of krill (Gendron 1992, de Guevara et al. 2008); however, it is possible that the shearwaters were aggregating around the foraging whales because the whales drive euphausiids closer to the surface, making the prey accessible to the birds. ...
Article
Humpback whales feed on a variety of prey, but significant differences likely occur between regional feeding grounds. In this study, the diets of humpback whales were analyzed by comparing stable isotope ratios in animal tissues at three humpback whale feeding grounds in the Russian Far East: Karaginsky Gulf, Anadyr Gulf, and the Commander Islands. Anadyr Gulf is a neritic zone far from a shelf break, Karaginsky Gulf is a neritic zone close to a shelf break, and the Commander Islands represent an open oceanic ecosystem where whales feed off the shelf break. Samples from the Commander Islands had the lowest mean δ13C and δ15N values (mean ± SE: δ13C = −18.7 ± 0.1, δ15N = 10.4 ± 0.1) compared to the samples from Karaginsky Gulf (δ13C = −17.2 ± 0.1, δ15N = 12.7 ± 0.2) and Anadyr Gulf (δ13C= −17.8 ± 0.1, δ15N = 14.0 ± 0.4). The samples from Anadyr Gulf had the highest δ15N values, while the samples from Karaginsky Gulf had the highest δ13C values. Both δ13C and δ15N values differed significantly among all three areas. Our data support the hypothesis that humpback whales tend to feed on fish in neritic areas and on plankton in deep oceanic waters.
... mm) even when small krill (5.0-8.4 mm) were present, though shorttailed shearwaters associating with a tidal front tended to feed on smaller krill (Vlietstra et al., 2005). In the southeastern Bering Sea, short-tailed shearwaters consumed almost exclusively the mature females of T. raschii carrying spermatophores (Hunt et al., 1996;Baduini et al., 2001), indicating that they fed on the mating swarm of krill. Thus, 20 short-tailed shearwaters fed on larger and mature krill perhaps because larger krill contain more gross energy than small krill (Färber-Lorda et al., 2009). ...
Article
Short-tailed shearwater Puffinus tenuirostris is one the of abundant marine top predators in the Pacific; this seabird spend its non-breeding period in the northern North Pacific during May–September and many visit the southern Chukchi Sea in July–September. We examined factors affecting this seasonal pattern of distribution by counting short-tailed shearwaters from boats. Their main prey, krill was sampled by NORPAC net in the southeastern Bering Sea/Aleutian Islands and in the Bering Strait/southern Chukchi Sea. Short-tailed shearwaters mainly distributed in the southeastern Bering Sea/Aleutian Islands (60 ± 473 birds km−2) in summer (July) but in the Bering Strait/southern Chukchi Sea (19 ± 91 birds km−2) in fall (September). In the Bering Strait/southern Chukchi Sea size of krill was greater in fall (9.6 ± 5.0 mm in total length) than in summer (1.9 ± 1.2 mm). Within the Bering Strait/southern Chukchi Sea in fall, short-tailed shearwaters occurred more frequently in cells (50 km × 50 km) where large krill was more abundant. Our results suggest that the seasonal northward movement of short-tailed shearwaters could be associated with the seasonal increase of large krill in the Bering Strait/southern Chukchi Sea. This study substantiates the importance of krill, which is advected from the Pacific, as a prey of top predators in the Arctic marine ecosystem.
... Extreme changes in the spatial and temporal availability of food can have dramatic effects on the survival of adult seabirds (Baduini et al., 2001;Piatt and van Pelt, 1997). However, seabirds are able to travel great distances and so are insulated to some extent from environmental variability.They are able to exploit locally and ephemerally favorable conditions during much of the year quite freely. ...
... The biomass of zooplankton and micro-nekton are infl uenced not only by physical parameters but also by animals at higher trophic levels such as anadromous salmon, non-salmonid fi shes, and birds (Baduini et al. 2001;Davis et al. 2009;Coyle et al. 2011). Shiomoto et al. (1997) reported that year-to-year variation in pink salmon abundance plays a large part in controlling the summer biomass of macrozooplankton and phytoplankton in the central subarctic North Pacifi c. Kaga et al. (2013) reported that analysis of stomach contents of chum salmon indicated non-crustacean zooplankton (appendicularians, chaetognaths, hydrozoans, polychaetes and pteropods) were consumed at a higher frequency when pink salmon were more abundant. ...
... mm) even when small krill (5.0-8.4 mm) were present, although they tended to feed on smaller krill at a tidal front (Vlietstra et al., 2005). In the southeastern Bering Sea, short-tailed shearwaters consumed almost exclusively the mature females of T. raschii carrying spermatophores (Hunt et al., 1996;Baduini et al., 2001), indicating that they fed on mating swarms of krill during daytime. Thus, short-tailed shearwaters tended to feed on Toge et al. (2011) larger and more mature krill, perhaps because larger krill contain more gross energy than smaller krill (Färber-Lorda et al., 2009). ...
Article
Full-text available
The short-tailed shearwater (Ardenna tenuirostris) is one of the abundant marine top predators in the Pacific; this seabird spends its non-breeding period in the northern North Pacific during May–October and many visit the southern Chukchi Sea in August–September. We examined potential factors affecting this seasonal pattern of distribution by counting short-tailed shearwaters from boats. Their main prey, krill, was sampled by net tows in the southeastern Bering Sea/Aleutian Islands and in the Bering Strait/southern Chukchi Sea. Short-tailed shearwaters were mainly distributed in the southeastern Bering Sea/Aleutian Islands (60 ± 473 birds km⁻²) in July 2013, and in the Bering Strait/southern Chukchi Sea (19 ± 91 birds km⁻²) in September 2012. In the Bering Strait/southern Chukchi Sea, krill size was greater in September 2012 (9.6 ± 5.0 mm in total length) than in July 2013 (1.9 ± 1.2 mm). Within the Bering Strait/southern Chukchi Sea in September 2012, short-tailed shearwaters occurred more frequently in cells (50 × 50 km) where large-sized krill were more abundant. These findings, and information previously collected in other studies, suggest that the seasonal northward movement of short-tailed shearwaters might be associated with the seasonal increase in krill size in the Bering Strait/southern Chukchi Sea. We could not, however, rule out the possibility that large interannual variation in krill abundance might influence the seasonal distribution of shearwaters. This study highlights the importance of krill, which is advected from the Pacific, as an important prey of top predators in the Arctic marine ecosystem.
... It has been suggested that population regulation of marine birds may be related to winter food supplies (Lack 1966, Gaston 2003, but this theory has not been fully investigated in different marine regions. There is increasing evidence that environmental factors do affect adult mortality (Nur & Sydeman 1999, Jones et al. 2002, Kitaysky et al. 2007, Parrish et al. 2007, Lavers et al. 2008, and episodic catastrophic mortality events likely play a role in population regulation (Harris & Wanless 1996, Baduini et al. 2001). However, more research is needed on the effects of prey availability on adult survival of marine birds during the non-breeding season, and effects this mortality may have on population regulation. ...
Article
Patterns of spatial and temporal co-occurrence or avoidance among different species of marine birds and mammals can provide insights into the degree to which these top predators compete for prey. I conducted at-sea surveys in nearshore waters of Monterey Bay, California, USA, and used a randomization technique to assess co-occurrence patterns of marine birds and mammals in 1 km transect segments. As expected, strongest positive associations were among members of 3 different foraging guilds: pursuit-divers, surface-feeders, and plunge-divers. Within guilds, pursuit- divers exhibited marked avoidance of one another (negative co-occurrence), although surface- feeders often co-occurred with each other. The study was conducted during 2 yr, 1999 and 2000; during 2000, when predator abundance was greater and prey abundance may have been decreased, pursuit-divers exhibited more avoidance of one another than in 1999. These data suggest that competition reduces foraging ability for pursuit-diving species, making it more profitable for them to disperse more widely, whereas surface-feeding species (primarily gulls) benefit from flock foraging under most conditions. Larger animals tended to frequently co-occur, while the smallest member of each guild tended to avoid other species, indicating competitive exclusion of smaller predators.
... These findings suggest that this region, during the austral winter of 2009, was atypical for prey availability/abundance to penguins and other predators in the region. Indeed, anomalous oceanographic, sea-ice and/or weather conditions can cause changes in prey availability [12,47,48] and are known to have negative impacts on populations of seabirds, including mass mortalities (also known as "wrecks" of seabirds) [49][50][51][52]. ...
Article
Full-text available
Knowledge about sexual segregation and gender-specific, or indeed individual specialization , in marine organisms has improved considerably in the past decade. In this context, we tested the " Intersexual Competition Hypothesis " for penguins by investigating the feeding ecology of Gentoo penguins during their austral winter non-breeding season. We considered this during unusual environmental conditions (i.e. the year 2009 had observations of high sea surface and air temperatures) in comparison with the long term average at Bird Island, South Georgia. Through conventional (i.e. stomach contents) and stable isotopic values from red blood cells, plasma and feathers of both male and female Gentoo penguins, we showed that there were significant differences between sexes, with males feeding mainly on fish (54% by mass) followed by crustaceans (38%) whereas females fed mainly on crustaceans (89% by mass) followed by fish (4%). Themisto gaudichaudii was the most important crustacean prey for males (64% by mass; 82% by number; 53% by frequency of occurrence) and females (63% by mass; 77% by number; 89% by frequency of occurrence), contrasting with all previous studies that found Antarctic krill Euphausia superba were generally the main prey. Stable isotopic data showed that, in terms of habitat use (based on δ 13 C), there were significant differences in short-term carbon signatures between males and females (based on plasma and red blood cells), suggesting that both sexes explored different habitats, with females exploring more offshore pelagic waters and males feeding more in coastal benthic waters. Based on δ 15 N, males fed on significantly higher trophic level than females (based on plasma and red blood cells), in agreement with our diet results., Thus, Gentoo penguins behave in a similar manner to other non-breeding penguins species (e.g. king, macaroni and rockhopper penguins)
... A second theme emerging in the progress of biological oceanography of the North Pacific Ocean is variation or deviation from traditional food webs along with recognition of woefully understudied groups of organisms. A striking example of a change in food web structure is the unusual appearance of coccolithophore blooms in the Bering Sea (Fig. 3), concurrent changes in relative abundances of copepods and euphausids Hunt 2001, Stockwell et al. 2001), and massive die-off of short-tailed shearwaters (Puffinus tenuirostris), an apex predator in the south-eastern Bering Sea (Baduini et al. 2001). Another example of a major change in foob web structure is the seven-fold increase in gelatinous zooplankton in the Bering Sea (Fig. 4) that may result from a competitive interaction between jellyfish and walleye pollock (Brodeur et al. 1999(Brodeur et al. , 2002. ...
... Since the 1980s, extreme warming events have had far-reaching effects on the survival, phenology and breeding success of many seabird species. For example, a strong El Niño in 1997 led to the starvation of thousands of shorttailed shearwaters (Puffinus tenuirostris), which washed up emaciated on shorelines of the southern Bering Sea and Gulf of Alaska (Baduini et al., 2001). More recently, the Blob was correlated with breeding failures and mass mortalities of common murres (Uria aalge), Cassin's auklets (Cerorhinca monocerata) and red phalaropes (Phalaropus fulicarius) in the Northeastern Pacific Ocean (Drever et al., 2018;Jones et al., 2018;Piatt et al., 2020). ...
Article
Full-text available
‘The Blob’, a mass of anomalously warm water in the Northeast Pacific Ocean peaking from 2014 to 2016, caused a decrease in primary productivity with cascading effects on the marine ecosystem. Among the more obvious manifestations of the event were seabird breeding failures and mass mortality events. Here, we used corticosterone in breast feathers (fCort), grown in the winter period during migration, as an indicator of nutritional stress to investigate the impact of the Blob on two sentinel Pacific auk species (family Alcidae). Feathers were collected from breeding females over 8 years from 2010 to 2017, encompassing the Blob period. Since Pacific auks replace body feathers at sea during the migratory period, measures of fCort provide an accumulated measure of nutritional stress or allostatic load during this time. Changes in diet were also measured using δ15N and δ13C values from feathers. Relative to years prior to the Blob, the primarily zooplanktivorous Cassin’s auklets (Ptychoramphus aleuticus) had elevated fCort in 2014–2017, which correlated with the occurrence of the Blob and a recovery period afterwards, with relatively stable feather isotope values. In contrast, generalist rhinoceros auklets (Cerorhinca monocerata) displayed stable fCort values across years and increased δ15N values during the Blob. As marine heatwaves increase in intensity and frequency due to climate change, this study provides insight into the variable response of Pacific auks to such phenomena and suggests a means for monitoring population-level responses to climatological variation.
... Since an unknown but likely large proportion of birds will never wash up on land and will instead sink or be predated at sea, the reported values are conservative (Camphuysen et al., 1999). Most articles with quantifiable data cite the recorded number of beach-washed birds, with only Baduini et al., (2001a) estimating the total number of birds floating at-sea based on numbers observed along at-sea transects. They estimated that birds counted during beach surveys equated to only~10% of the total wreck, although they did not undertake a systematic beach survey; we can easily hypothesize that the numbers of birds that wash-up will be substantially fewer than the total numbers involved. ...
Article
There is an absence of quantitative criteria and definitions for unusual or anomalous mortality events involving birds, often referred to as “wrecks”. These events most commonly involve seabirds, although terrestrial bird wrecks have also been documented. Typically, the peer-reviewed literature investigating wreck events lacks the details necessary to further our understanding of the circumstances and potential causes of these events. This study reviewed the peer-reviewed literature for wrecks involving Ardenna seabirds (shearwaters), and included grey literature and data collected by citizen science (community) groups. Our results showed a significant time-lag between wreck events and when the data was published in the peer-reviewed literature, which did not occur in the grey literature. Both the grey and peer-reviewed literature were often skewed towards reporting larger wreck events, with only the citizen science dataset capturing smaller wrecks. We outline a proposed framework for reporting mortality events, including the use of quantitative categories to document the numbers of birds involved and taxon-specific thresholds. In doing so, we aim to establish a framework to aid in the quantitative reporting and analyses of future seabird wrecks.
... We were able to detect a functional relationship between the distribution of group B and C and the distribution of at least one of the prey groups we tested, however this was not the case for group A. A large proportion of the diet of short-tailed shearwaters and fairy prions is comprised of large zooplankton species such as krill and large copepods (Morgan and Ritz, 1982), although they also feed on fish larvae and squid (Prince and Copestake, 1990). In Tasmania and the Bering sea both species are highly reliant on near-shore stocks of euphausiids (Bartle, 1976;Weimerskirch and Cherel, 1998;Baduini et al., 2001). Euphausiids were previously abundant in this region; O'Brien (1988) characterised schooling behaviour of Nyctiphanes australis off south-east, east and northern Tasmania, and describes these schools as being highly abundant with a density of between 3000 and >450,000 individuals m -3 . ...
Thesis
The land-sea interface provides some of the world’s most valuable and biodiverse habitats, despite being exposed to anthropogenic pressures. Marine predators which cross this interface are particularly vulnerable, with human activities in coastal zones diminishing both the quality and availability of suitable breeding and foraging areas. These predators are constrained to forage in smaller oceanic regions while rearing young on-land, therefore their reproductive success is intrinsically linked to the productivity of nearshore waters. Changing environmental conditions, as a direct and indirect consequence of climate change, can alter the structure, distribution and community composition of lower-trophic level prey. In order to predict the response of ecosystems to this change, and to changes as a result of extreme events such as marine heatwaves (MHW), an in depth understanding of the links between environmental factors, prey-field dynamics and predator behaviour is needed. The continental shelf to the south-east of Tasmania is a hotspot of biodiversity, where seasonal productivity supports a large and diverse array of marine birds and mammals. However, this region is also subject to rapid environmental change, being situated within the south-east Australian climatic-hotspot. Due to the intensification and increasing southward penetration of the East Australian Current (EAC), a major western boundary current running from the sub-tropical Coral Sea to the south-east coast of Australia, warming is occurring at an accelerated rate. Quantifying how prey-field dynamics respond to these changing environmental conditions, and the flow-on effects to the behaviour of apex predators, formed the main objective of this study. Surveys were conducted over a three-year period (2015-2018), during which a prolonged marine heatwave (MHW) event occurred that increased water temperatures of the entire western Tasman Sea by a mean of 2.9°C above climatology for 251 days. To develop an integrated understanding of ecosystem dynamics through a period of high environmental variability, zooplankton prey-field dynamics, fish school presence, little penguin (Eudyptula minor) foraging behaviour, and the distribution and abundance of key bird species were analysed in relation to local environmental factors. Zooplankton community composition and abundance were examined in relation to environmental drivers. Generalised additive models (GAMs) indicated a significant decrease in community abundance during the MHW, with a shift in species assemblages away from temperate species and towards EAC-associated species. The size structure of the zooplankton community was also analysed using the normalised biomass size spectra (NBSS). The NBSS is an effective way to demonstrate the variability present in a community, in terms of gains and loss of energy through respiration, predation and mortality. It can also be indicative of changes to the equilibrium of a community. Strong seasonality was detected in the results, with temperature, current velocity and mixed-layer depth being significant drivers of variability in the NBSS. These lower trophic level dynamics were linked to the behaviour of top predators through a detailed case study of the at-sea habitat preference of little penguins breeding in south-east Tasmania (n=13). Tracking was conducted over two summer periods, in 2016 during the MHW, and in 2018 under cooler and more stable environmental conditions. Habitat models (species distribution models) were developed to asses spatial distribution patterns and examine the bio-physical factors influencing foraging trips at fine-scale. Regions of higher sea-surface temperature gradients and cooler than average temperatures were found to increase the probability of penguin presence. The predictability of little penguin habitat-use according to prey-type was also assessed by including covariates for the general distribution of resources in the region; e.g. total zooplankton abundance, and the abundance of Australian krill (Nyctiphanes australis), which forms part of little penguin diet. Little penguin foraging areas were more influenced by the distribution of Australian krill than by general zooplankton abundance. The response of local predators to changes in bio-physical parameters were measured by modelling the distribution of 10 species of seabirds using boosted regression trees. Key species ranged from small planktivores, such as the common diving petrel (Pelecanoides urinatrix), to albatross (family Diomedeidae). Therefore, to encompass the range of prey that underpins the distribution of these species, biological covariates included zooplankton biomass, and the presence (and absence) of fish schools (determined using hydro-acoustics during surveys). Seabird species were separated into feeding groups using multivariate analysis and modelled separately to reveal potential drivers for each group. Despite different biological predictors influencing the distribution of different groups, sea surface temperature was found to explain the greatest amount of variation across all feeding groups. This influence is thought to be prey-mediated, as both biological covariates tested exhibited negative correlations with increasing SST. Through considering the complex links which exist between predators, their prey and the physical environment, this study produces new insights into the potential effects of extreme events. Further, it improves our understanding of how general warming trends affect prey structure and the possible flow-on effects for predators. Modelling the distribution of apex predators enables the identification of important foraging regions with favourable bio-physical characteristics. We highlight how detailed assessments of ecosystem and environmental interactions can be pivotal to informing the effective management of these vulnerable and biodiverse ecosystems into the future.
... The same prey alterations that affect breeding success may also affect the survival rate of adult birds. Mass mortality as a result of potentially climate-induced large-scale fluctuations of prey has been reported in piscivorous seabirds feeding on schooling fish in the Barents Sea (Barrett & Krasnov 1996), the Bering Sea (Baduini et al. 2001) and the North Sea (Blake 1984), but have yet not been observed for the Baltic Sea. Trends in surface and mid-water salinity in the Baltic Sea show influences from the cold winter in 1987 in southern parts (lower salinities due to ice conditions) and from the large-scale intrusion of high-saline water masses in at depth in 1993 ( Figure 22). ...
Book
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This report outlines the results of the coordinated census of wintering waterbirds in the Baltic Sea 2007–2009 undertaken under the SOWBAS project (Status of wintering Waterbird populations in the Baltic Sea). The international co-ordination and analyses of the waterbird census was funded by a grant from the Nordic Council of Ministers, and the surveys were funded by the regional and national authorities and organised by the involved governmental agencies, universities, NGOs and private consulting companies.
... On St. Lawrence Island, large numbers of dead murres were reported washing up on beaches starting in late May and early June, at the beginning of the 2018 breeding season (Romano et al., 2020). Previously reported mortality events, both in Alaska and elsewhere in the Northern Hemisphere, have occurred primarily in mid-winter (Piatt and Van Pelt, 1997;Furness and Tasker, 1999;Baily and Davenport, 2016), or have included short-tailed shearwaters (Puffinus tenuirostris) which were overwintering from the Southern Hemisphere and occurred later in the summer (Baduini et al., 2001). One possible explanation for the unusual timing of the 2018 die-off is that birds arrived in the Arctic in poor condition after migrating from their lower latitude overwintering locations. ...
Article
Die-offs of seabirds in Alaska have occurred with increased frequency since 2015. In 2018, on St. Lawrence Island, seabirds were reported washing up dead on beaches starting in late May, peaking in June, and continuing until early August. The cause of death was documented to be starvation, leading to the conclusion that a severe food shortage was to blame. We use physiology and colony-based observations to examine whether food shortage is a sufficient explanation for the die-off, or if evidence indicates an alternative cause of starvation such as disease. Specifically, we address what species were most affected, the timing of possible food shortages, and food shortage severity in a historical context. We found that thick-billed murres (Uria lomvia) were most affected by the die-off, making up 61% of all bird carcasses encountered during beach surveys. Thick-billed murre carcasses were proportionately more numerous (26:1) than would be expected based on ratios of thick-billed murres to co-occurring common murres (U. aalge) observed on breeding study plots (7:1). Concentrations of the stress hormone corticosterone, a reliable physiological indicator of nutritional stress, in thick-billed murre feathers grown in the fall indicate that foraging conditions in the northern Bering Sea were poor in the fall of 2017 and comparable in severity to those experienced by murres during the 1976–1977 Bering Sea regime shift. Concentrations of corticosterone in feathers grown during the pre-breeding molt indicate that foraging conditions in late winter 2018 were similar to previous years. The 2018 murre egg harvest in the village of Savoonga (on St. Lawrence Is.) was one-fifth the 1993–2012 average, and residents observed that fewer birds laid eggs in 2018. Exposure of thick-billed murres to nutritional stress in August, however, was no different in 2018 compared to 2016, 2017, and 2019, and was comparable to levels observed on St. George Island in 2003–2017. Prey abundance, measured by the National Oceanic and Atmospheric Administration in bottom-trawl surveys, was also similar in 2018 to 2017 and 2019, supporting the evidence that food was not scarce in the summer of 2018 in the vicinity of St. Lawrence Island. Of two moribund thick-billed murres collected at the end of the mortality event, one tested positive for a novel re-assortment H10 strain of avian influenza with Eurasian components, likely contracted during the non-breeding season. It is not currently known how widely spread infection of murres with the novel virus was, thus insufficient evidence exists to attribute the die-off to an outbreak of avian influenza. We conclude that food shortage alone is not an adequate explanation for the mortality of thick-billed murres in 2018, and highlight the importance of rapid response to mortality events in order to document alternative or confounding causes of mortality.
... There is no direct evidence, but observations of ecosystem effects in the vicinity of a coccolithophore bloom (potentially initiated by anomalous weather conditions), point to a sea-bird mass mortality event in the SE Bering Sea (Baduini et al., 2008). GESAMP Clouds form when water droplets gather on dust or other particles in the air. ...
Technical Report
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The report provides an initial high-level review of twenty-seven proposed marine geoengineering techniques - with its potential subsets - for climate mitigation that focuses on their efficacy, practicality, side-effects, knowledge gaps, verification and potential environmental and socio-economic impacts.
... The predicted changes in the marine environment are likely to influence prey density and availability, and potential decreases in prey populations may ultimately result in lowered breeding success or increased susceptibility to mortality for Short-tailed Shearwaters (Baduini et al. 2001a). ...
Article
Full-text available
Establishing appropriate conservation management objectives and actions for seabirds requires timely detection of changes in their populations. However, obtaining regular accurate measures of seabird population size and trends can be difficult due to logistical and financial constraints in accessing remote breeding sites. The Short-tailed Shearwater (Ardenna tenuirostris) is a wide-ranging, burrow-nesting Procellariiform with an estimated breeding population size of ca 23 million individuals. Despite its ecological significance, there is currently limited monitoring of the species. In the present study, eight acoustic data loggers were deployed across six sites over two breeding seasons to assess the efficacy of acoustic monitoring. Five acoustic indices were used to investigate vocal activity over the breeding season, detect phenology events, and to determine the most accurate period to assess the density of occupied nests. The general pattern over the breeding season was similar for several of the acoustic indices and reflected colony attendance patterns. Linear regressions fitted to the normalised difference soundscape index values and density of occupied nests (burrows·m⁻²) revealed significant relationships in both the incubation and chick-rearing. The results suggest that passive acoustic monitoring could be used as an effective method to predict nesting density in Short-tailed Shearwater breeding colonies. Used in conjunction with information on the breeding colony area, this could enable regular estimates of colony population size. Such information is crucial for the early detection of population trajectory changes. The method may also be applicable for other burrow- or surface-nesting seabirds for which regular wide-spread monitoring currently proves difficult.
... Anomalous rises in seawater temperature associated with ENSO have also caused severe reductions in food supplies, leading to starvation and mass mortality of marine birds (109)(110)(111). More recently, ocean warming associated with climate change has precipitated bottom-up trophic cascades, analogous to those proposed here for terrestrial systems, which have restructured both benthic and pelagic food webs and driven declines in shearwaters and auklets (112)(113)(114). ...
Article
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A number of studies indicate that tropical arthropods should be particularly vulnerable to climate warming. If these predictions are realized, climate warming may have a more profound impact on the functioning and diversity of tropical forests than currently anticipated. Although arthropods comprise over two-thirds of terrestrial species, information on their abundance and extinction rates in tropical habitats is severely limited. Here we analyze data on arthropod and insectivore abundances taken between 1976 and 2012 at two midelevation habitats in Puerto Rico’s Luquillo rainforest. During this time, mean maximum temperatures have risen by 2.0 °C. Using the same study area and methods employed by Lister in the 1970s, we discovered that the dry weight biomass of arthropods captured in sweep samples had declined 4 to 8 times, and 30 to 60 times in sticky traps. Analysis of long-term data on canopy arthropods and walking sticks taken as part of the Luquillo Long-Term Ecological Research program revealed sustained declines in abundance over two decades, as well as negative regressions of abundance on mean maximum temperatures. We also document parallel decreases in Luquillo’s insectivorous lizards, frogs, and birds. While El Niño/Southern Oscillation influences the abundance of forest arthropods, climate warming is the major driver of reductions in arthropod abundance, indirectly precipitating a bottom-up trophic cascade and consequent collapse of the forest food web.
... The formation of 'white waters' as a result of the production and shedding of coccoliths has also been suggested to impact higher marine trophic levels. For example, E. huxleyi blooms in the Eastern Bering Sea have coincided with widespread seabird mortality (Baduini et al. 2001) and poor salmon runs (Vance et al. 1998), while visual predators and zooplankton grazers seem to avoid bloom areas (Eisner et al. 2005). Here we showed that although the amount of CaCO 3 per E. huxleyi cell did not vary significantly between exponentially growing cultures, exposure to oil impacted the appearance and shedding of E. huxleyi coccoliths. ...
... Mees (1976) described a mass mortality event of Great Shearwaters in Surinam in June 1974. Mortality of Short-tailed Shearwaters Ardenna tenuirostris in the North Pacific has been linked to annual variability of prey abundance during migration between the southern hemisphere breeding grounds and feeding areas in the Bering Sea, leading to differences in body mass with the lowest values in the years of high mortality (Baduini et al. 2001a, Oka & Maruyama 1986. Reduced prey abundance in equatorial waters reduces the flight range and, therefore, the ability to locate new feeding areas, leading to starvation (Baduini et al. 2001b). ...
Article
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We report at least 103 Great Shearwaters Ardenna gravis found between 22 and 27 June 2011, washed up along 7 km of beach between Tanji Bird Reserve and Tranquil Beach, Coastal Western Region, The Gambia. This discovery represents the first Gambian record of this species and at a time of the year that it was not expected in Senegambian waters. A photographic record was made in situ each day of the numerous shearwater remains, most of which had been scavenged by ghost crabs Ocypode spp. and some by Hooded Vultures Necrosyrtes monachus. Measurements of 18 cleaned skulls are presented. We summarise published sightings of Great Shearwater for Senegal, Mauritania and the Cape Verde islands and provide new information for Senegal. Movements of satellite-tracked Great Shearwaters from their breeding grounds in the southern hemisphere to the North Atlantic are discussed as well as their foraging strategies during this migration. Starvation is proposed as the probable cause of the wreck. Pelagic studies during the rainy season and discussions with artisanal fishermen operating in Senegambian waters are needed to reveal the status of many seabirds in these under-explored waters.
... Diets of pink salmon and short-tailed shearwaters overlap (49)(50)(51)(52)(53)(54), and the biennial pattern in shearwater body condition has been linked to competition with pink salmon for common prey (47). These patterns are distinct from occasional mass mortalities (wrecks), which are comprised primarily of immature birds that occur off Japan in spring as they arrive from the Southern Hemisphere (55), and in the Bering Sea, where wrecks have occurred at least twice in late summer, in 1983 and 1997 (56,57). Both years were odd years but were further beset by strong El Niño conditions. ...
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Pink salmon (Oncorhynchus gorbuscha) in the North Pacific Ocean have flourished since the 1970s, with growth in wild populations augmented by rising hatchery production. As their abundance has grown, so too has evidence that they are having important effects on other species and on ocean ecosystems. In alternating years of high abundance, they can initiate pelagic trophic cascades in the northern North Pacific Ocean and Bering Sea and depress the availability of common prey resources of other species of salmon, resident seabirds, and other pelagic species. We now propose that the geographic scale of ecosystem disservices of pink salmon is far greater due to a 15,000-kilometer transhemispheric teleconnection in a Pacific Ocean macrosystem maintained by short-tailed shearwaters (Ardenna tenuirostris), seabirds that migrate annually between their nesting grounds in the South Pacific Ocean and wintering grounds in the North Pacific Ocean. Over this century, the frequency and magnitude of mass mortalities of shearwaters as they arrive in Australia, and their abundance and productivity, have been related to the abundance of pink salmon. This has influenced human social, economic, and cultural traditions there, and has the potential to alter the role shearwaters play in insular terrestrial ecology. We can view the unique biennial pulses of pink salmon as a large, replicated, natural experiment that offers basin-scale opportunities to better learn how these ecosystems function. By exploring trophic interaction chains driven by pink salmon, we may achieve a deeper conservation conscientiousness for these northern open oceans.
... Conversely, in the Gulf of Alaska large numbers of common guillemots (Uria aalge) were found dead in 1993, apparently having died from starvation most probably due to the offshore unavailability of food (Piatt and van Pelt 1997). In the southeast Bering Sea, hundreds of thousands of emaciated shorttailed shearwaters died in 1997—a phenomenon quite likely due to long-term climatic changes (Baduini et al. 2001). These climatic effects could either be severe weather that hampered foraging, or anomalous oceanographic conditions that change the distribution and abundance of prey (Harris and Wanless 1996; Piatt and van Pelt 1997 ). ...
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This chapter shows how climate might influence seabirds directly through variations in temperature and wind. It also provides an overview of the potential indirect impact of climate variability on North Atlantic seabird populations. Seabirds are sensible to climate change either positively as shown by the extension of the fulmar population, or negatively as shown by the Atlantic puffins. Thanks to their position as top predators, their response to climate change is a good index of its effect on the whole food web.
... Climate regime shifts have been repeatedly reported in the area since at least the 1970's [2]. Warm water was observed in the area from the late 1990's to the middle of the 2000's [3,4], along with several biological changes, such as a low biomass of copepods, a coccolithophorid (Emiliania huxleyi) bloom, the mass mortality of short-tailed seabirds (Puffinus tenuirostrises), and a sudden and significant increase in large jellyfish (Chrysaora melanasters) [4][5][6][7]. ...
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The eastern Bering Sea has a vast continental shelf, which contains various endangered marine mammals and large fishery resources. Recently, high numbers of toxic A. tamarense resting cysts were found in the bottom sediment surface of the eastern Bering Sea shelf, suggesting that the blooms have recently occurred. However, little is known about the presence of A. tamarense vegetative cells in the eastern Bering Sea. This study's goals were to detect the occurrence of A. tamarense vegetative cells on the eastern Bering Sea shelf and to find a relationship between environmental factors and their presence. Inter-annual field surveys were conducted to detect A. tamarense cells and environmental factors, such as nutrients, salinity, chlorophyll a, and water temperature, along a transect line on the eastern Bering Sea shelf during the summers of 2004, 2005, 2006, 2009, 2012, and 2013. A. tamarense vegetative cells were detected during every sampling year, and their quantities varied greatly from year to year. The maximum cell densities of A. tamarense observed during the summers of 2004 and 2005 were much higher than the Paralytic shellfish poisoning warning levels, which are greater than 100–1,000 cells L⁻¹, in other subarctic areas. Lower quantities of the species occurred during the summers of 2009, 2012, and 2013. A significant positive correlation between A. tamarense quantity and water temperature and significant negative correlations between A. tamarense quantity and nutrient concentrations (of phosphate, silicate, and nitrite and nitrate) were detected in every sampling period. The surface- and bottom-water temperatures varied significantly from year to year, suggesting that water temperatures, which have been known to affect the cell growth and cyst germination of A. tamarense, might have affected the cells' quantities in the eastern Bering Sea each summer. Thus, an increase in the Bering Sea shelf's water temperature during the summer will increase the frequency and scale of toxic blooms and the toxin contamination of plankton feeders. This poses serious threats to humans and the marine ecosystem.
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The northern fulmar Fulmarus glacialis is one of the most visible and widespread seabirds in the eastern Bering Sea and Aleutian Islands. However, relatively little is known about its abundance, trends, or the factors that shape its distribution. We used a long-term pelagic dataset to model changes in fulmar at-sea distribution and abundance since the mid-1970s. We used an ensemble model, based on a weighted average of generalized additive model (GAM), multivariate adaptive regression splines (MARS), and random forest models to estimate the pelagic distribution and density of fulmars in the waters of the Aleutian Archipelago and Bering Sea. The most important predictor variables were colony effect, sea surface temperature, distribution of fisheries, location, and primary productivity. We calculated a time series from the ratio of observed to predicted values and found that fulmar at-sea abundance declined from the 1970s to the 2000s at a rate of 0.83% (+/- 0.39% SE) per annum. Interpolating fulmar densities on a spatial grid through time, we found that the center of fulmar distribution in the Bering Sea has shifted north, coinciding with a northward shift in fish catches and a warming ocean. Our study shows that fisheries are an important, but not the only factor, shaping fulmar distribution and abundance trends in the eastern Bering Sea and Aleutian Islands.
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Puffinus tenuirostris mortality in the south-eastern Bering Sea, 1997–1999. Marine Ornithology 29: 11–18. During 1997, hundreds of thousands of Short-tailed Shearwaters Puffinus tenuirostris starved to death in the Bering Sea. We surveyed the distribution and abundance of floating carcasses during a cruise between 27 August–12 September, and estimated that over 95 000 carcasses were afloat within three survey grids covering approximately 52 400 km 2. We repeatedly surveyed the same areas during two subsequent cruises in 1998 and 1999, and used standard population sampling techniques to evaluate the background levels of shearwater mortality during additional years when a die-off did not occur. The mortality event we observed in 1997 was unusual due to its extent and magnitude. During the die-off, dead shearwaters were sighted within all three survey grids. Conversely, we only encountered carcasses at one of these sites in 1998. Moreover, carcass densities in 1997 were at least one order of magnitude higher than those recorded during the following year. Surveys of seabird mortality at sea can account for floating carcasses before they are lost through advection and scavenging. Therefore, vessel-based surveys are likely to improve the accuracy of seabird mortality estimates based solely on counts of beach-cast carcasses. Here we describe the use of line transects to estimate seabird mortality at sea, and offer suggestions to standardize future surveys. Standardized
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Climate change impacts are pronounced at high latitudes, where warming, reduced sea-ice-cover, and ocean acidification affect marine ecosystems. We review climate change impacts on two major gateways into the Arctic: the Bering and Chukchi seas in the Pacific and the Barents Sea and Fram Strait in the Atlantic. We present scenarios of how changes in the physical environment and prey resources may affect commercial fish populations and fisheries in these high-latitude systems to help managers and stakeholders think about possible futures. Predicted impacts include shifts in the spatial distribution of boreal species, a shift from larger, lipid-rich zooplankton to smaller, less nutritious prey, with detrimental effects on fishes that depend on high-lipid prey for overwinter survival, shifts from benthic- to pelagic-dominated food webs with implications for upper trophic levels, and reduced survival of commercially important shellfish in waters that are increasingly acidic. Predicted changes are expected to result in disruptions to existing fisheries, the emergence of new fisheries, new challenges for managing transboundary stocks, and possible conflicts among resource users. Some impacts may be irreversible, more severe, or occur more frequently under anthropogenic climate change than impacts associated with natural variability, posing additional management challenges.
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On the basis of the CTD data obtained within the Bering Sea shelf by the Second to Sixth Chinese National Arctic Research Expedition in the summers of 2003, 2008, 2010, 2012 and 2014, the classification and interannual variation of water masses on the central Bering Sea shelf and the northern Bering Sea shelf are analyzed. The results indicate that there are both connection and difference between two regions in hydrological features. On the central Bering Sea shelf, there are mainly four types of water masses distribute orderly from the slope to the coast of Alaska: Bering Slope Current Water (BSCW), MW (Mixed Water), Bering Shelf Water (BSW) and Alaska Coastal Water (ACW). In summer, BSW can be divided into Bering Shelf Surface Water (BSW_S) and Bering Shelf Cold Water (BSW_C). On the northern Bering Sea shelf near the Bering Strait, it contains Anadyr Water (AW), BSW and ACW from west to east. But the spatial-temporal features are also remarkable in each region. On the central shelf, the BSCW is saltiest and occupies the west of 177°W, which has the highest salinity in 2014. The BSW_C is the coldest water mass and warmest in 2014; the ACW is freshest and mainly occupies the east of 170°W, which has the highest temperature and salinity in 2012. On the northern Bering Sea shelf near the Bering Strait, the AW is saltiest with temperature decreasing sharply compared with BSCW on the central shelf. In the process of moving northward to the Bering Strait, the AW demonstrates a trend of eastward expansion. The ACW is freshest but saltier than the ACW on the central shelf, which is usually located above the BSW and is saltiest in 2014. The BSW distributes between the AW and the ACW and coldest in 2012, but the cold water of the BSW_C on the central shelf, whose temperature less than 0°C, does not exist on the northern shelf. Although there are so many changes, the respond to a climate change is synchronized in the both regions, which can be divided into the warm years (2003 and 2014) and cold years (2008, 2010 and 2012). The year of 2014 may be a new beginning of warm period.
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On 24 March 1989, the oil tanker 'Exxon Valdez' spilled 260,000 barrels of crude oil in Prince William Sound, Alaska. Oil eventually drifted over $30,000\ {\rm km}^{2}$ of coastal and offshore waters occupied by approximately one million marine birds. More than 30,000 dead birds of 90 species were retrieved from polluted areas by 1 August 1989. Of those identified, murres (74%), other alcids (7.0%), and sea ducks (5.3%) suffered the highest mortality from oil, and most (88%) birds were killed outside of Prince William Sound. A colony of 129,000 murres at the Barren Islands was probably devastated. Another 7,000 birds were retrieved between 1 August and 13 October, but most of those birds appeared to have died from natural causes. This later die-off was composed largely of shearwaters and other procellariids (51%), gulls (22%), and puffins (14%). Based on aerial and ship-based surveys for populations at risk, and extrapolating from the number of dead birds recovered, we estimate that the total kill from oil pollution was from 100,000 to 300,000 birds.
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We review the methods used to study seabirds at sea from ships, discuss the problems posed in making reliable observations in relation to the design of research pro-grams, and describe a method currently in use around the seas of Great Britain. We suggest a framework for future studies, incorporating features likely to stabilize bias. The key items in this recommendation are (1) the use of a band transect in order to provide density esti-mates, and (2) a method to correct for movement of flying birds in the band transect in order to minimize bias caused by such movement.
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In 1998, anomalous conditions in the Bering Sea included elevated heat content of the water, cross-shelf advection of zooplankton and larval fish, major changes in the structure of the zooplankton community, and an unprecedented second observation of a large-scale bloom of the coccolithophorid phytoplankton, Emiliania huxleyi. Some of these anomalies appear to be related to the unusual weather patterns of 1997 and 1998, while the causes of others remain unknown. The Bering Sea is located in the northernmost part of the North Pacific Ocean, and its broad eastern continental shelf constitutes approximately 44%of its area. Because Pacific water must pass through the Bering Sea before entering the Arctic, climatic events in the Bering affect heat and biogeochemical transport to the Arctic. The Bering Sea, in particular its broad eastern shelf region, is also the site of some of the worlds major fisheries. It contributes over half of the U.S. fishery production, with a commercial catch worth one billion dollars in 1997.
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It has been hypothesized that differentiation in food web structure occurs across the Bering Sea continental shelf as a result of seasonal differentiation of water masses. We tested this idea using an apex predator, pelagic birds. Seasonal abundance of birds in central Bristol Bay was estimated from counts made while underway between hydrographic stations. Prey and body mass were determined from birds collected at sea. Daily intake was estimated as an allometric function of body mass. Annual occupancy was estimated as the integral of a normal curve fit to seasonal data. Estimated carbon flux to seabirds in the middle domain was 0.12 gC m-2 y-1 in 1980, 0.18 gC m-2 y-1 in 1981. Carbon flux to seabirds in the adjacent waters of the outer shelf domain was 1.8 times higher than in the middle domain in 1980, 1.6 times higher in 1981. Carbon flux to seabirds in the inner domain was 1.2 times higher than in the middle domain in 1980, and 3.3 times higher in 1981. Carbon flux to seabirds in the outer domain was due primarily to non-diving species, principally northern fulmars (Fulmarus glacialis) during the summer and autumn, and Larus gulls in the autumn and winter. Flux to seabirds in the inner domain was due to diving birds, principally murres (Uria sp.) in the spring and shearwaters (Puffinus sp.) during the summer. The euphausiid Thysanoessa raschii was the primary food source of shearwaters in shallow waters of the inner shelf domain. A more diverse set of prey, including squid, jellyfish, hyperiids, and fish, was taken by shearwaters and fulmars in the deeper waters of the outer and middle shelf domains. This result suggests that prey diversity is higher in seasonally stratified waters of outer Bristol Bay than in mixed waters of inner Bristol Bay. Greater energy flux to diving species in shallow water, and greater energy flux to non-divers in deep water may be a function of topographic control of prey patchiness.
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We studied short-tailed shearwaters Puffinus tenuirostris foraging near the Pribilof Islands, Alaska, USA, during the summers of 1987, 1988, and 1989. Their foods were almost exclusively the euphausiid Thysanoessa raschii, which they obtained both from near-surface swarms and from epibenthic layers. Near-surface mating swarms of euphausiids occurred in areas of elevated phytoplankton standing stocks near inshore tidal fronts. Many of these euphausiids had attached spermatophores. Shearwaters also obtained euphausiids over shallow reefs and inshore of the fronts where euphausiids were trapped in water shallower than 40 m by irregularities in bottom topography ('bathymetric traps'). We hypothesize that the largely inshore distribution of shearwaters in the southeastern Bering Sea described by previous workers is the result of attraction of shearwaters to frontal areas where euphausiids may forage on phytoplankton stocks throughout the summer. These areas, when shallower than 40 m, would also permit shearwaters to access epibenthic aggregations of euphausiids during daylight, when euphausiids not engaged in mating swarms usually migrate to depth.
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Bays and semi‐enclosed seas provide a natural spatial scale at which to characterize the trophic organization of marine communities. This article summarizes the information available on the trophic organization (species number, relative abundance, seasonal abundance, foraging style, and diet) of the marine bird community at the spatial scale of the entire Bering Sea. This required synthesizing work in English (pertaining to the east) and Russian (pertaining to the west), much of it published after 1980. A total of 51 seabird species (not counting loons, grebes, and seaducks) regularly inhabit the Bering Sea. Based on work available (to 1990), the minimum number of breeding seabirds in the western Bering Sea is 3–1 × 10 along the Asian coast (Cape Kamchatskiy to the Bering Strait), 10 in the Commander Islands, 1.1 × 10 in the Aleutian Islands, and 1.2 × 10 along the North American coast (Uriimak Pass to the Bering Strait). Nonbreeding seabirds include 3 species of albatross, 3 pagophilic gulls, and on the order of 3–3 × 10 Pufftnus shearwaters. Seasonal movements are primarily meridional (north‐south) and strongly tied to the breeding cycle. Major foraging styles include surface gleaning (as in fulmars), bottom gleaning (as in cormorants), and mid‐water pursuit (as in murres). Major prey resources include euphausiids, squid, immature fish (notably Walleye pollock), and copepods. The data show that less than five avian species account for most of the energy flux to the avian community. The data indicate that this flux is strongly seasonal and highly localized in space. Localized seasonal concentrations of invertebrates (notably euphausiids and copepods) appear to be more important sources of energy flux to birds in this ecosystem than at lower latitudes.
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Various bird species regularly fast in connection with breeding, migration, or drastic climatic conditions. The metabolic response of penguins and domestic geese to fasting has been studied in detail. These large birds, in contrast to small species, do not become torpid when they are fasting. Nevertheless, they reduce their rate of energy expenditure by decreasing both resting metabolic rate and locomotor activity. From changes in the loss of body mass, the fast of penguins and geese has been divided into three phases: I, the loss of body mass decreases; II, it remains at a minimum level; and III, it increases. These phases reflect metabolic adjustments. Phase I is a rapid phase of adaptation, marked by a decrease in protein catabolism and mobilization of lipids. Phase II is a phase of economy, during which more than 90% of the energy expenditure derives from lipids, while protein catabolism remains at a minimum level. In phase III there still are lipid reserves and this phase is reversible; it is, however, critical because proteins are no longer spared. Data in the literature suggest that these three phases may also be used to describe how a wide variety of wild and domestic birds adapt to fasting.
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Variability in apparatus, solvent type, and extraction time for lipid extractions is common in the literature. To investigate the effect of this methodological variability on the amount and type of material extracted, equal subsamples of snow goose (Chen caerulescens) homogenate were extracted in Soxhlet and Goldfisch fat extractors with petroleum ether, diethyl ether, chloroform–methanol, and a petroleum ether–chloroform–methanol mixture for 3, 6, 12, and 24 h. The type of solvent used had the largest effect on the amount of material that was extracted. Petroleum ether and diethyl ether extracted few nonlipids, but chloroform–methanol extracted relatively large amounts of nonlipids. We conclude that chloroform–methanol, when used in a Goldfisch or Soxhlet fat extractor, is an inappropriate solvent for studies dealing with body composition.
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Measurements of the spectral scattering and attenuation properties of coccolithophores (Emiliania huxleyi; clone 88E) and their associated coccoliths were made for three growth phases as well as for acidified cultures. These measurements allow a clean separation and determination of the optical effects of the various components. The beam attenuation cross sections (m2 particle-1) were found to be 8.4E-12, 2.6E-10, and 4.9E-11 for coccoliths, plated cells, and naked cells, respectively, at 440 nm. The spectral dependence of these factors followed a power law dependence, with a wavelength exponent of -1.9, 0.42, and -0.52 for the coccoliths, plated cells, and naked cells. The volume scattering functions for all appeared similar; however, the backscattering cross sections (m2 particle-1) at 456 nm were 1.4E-13, 6.7E-12, and 9.9E-13, respectively. The wavelength dependence of this parameter also followed a power law and was -1.4, -1.2, and -1.0. Overall, these results show that optical properties of a coccolithophore bloom are sensitive to the coccolith:cell ratio and can vary between and within blooms.
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Complexity in modeling would seem to be an issue of universal importance throughout the geosciences, perhaps throughout all science, if the debate last year among groundwater modelers is any indication. During the discussion the following questions and observations made up the heart of the debate.As scientists trying to understand the natural world, how should our effort be apportioned? We know that the natural world is characterized by complex and interrelated processes. Yet do we need to explicitly incorporate these intricacies to perform the tasks we are charged with? In this era of expanding computer power and development of sophisticated preprocessors and postprocessors, are bigger machines making better models? Put another way, do we understand the natural world better now with all these advancements in our simulation ability? Today the public's patience for long-term projects producing indeterminate results is wearing thin. This increases pressure on the investigator to use the appropriate technology efficiently. On the other hand, bringing scientific results into the legal arena opens up a new dimension to the issue: to the layperson, a tool that includes more of the complexity known to exist in the real world is expected to provide the more scientifically valid answer.
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Thysanoessa inermis was the dominant euphausiid species observed over the outer shelf region; it began spawning in early April while T. raschi dominated the euphausiids over the middle shelf and began spawning in mid or late May. The seasonal progression in spawning followed the seasonal development of temperature, but spawning did not begin earlier in 1981 which was a warmer year than 1980. Average egg production of T. raschi ranged from 3.4-3.8% dry body weight of the female per day during the first three days after capture. Secondary production estimates for T. raschi females ranged from 4.2-5.2% dry body weight per day in 1980 and 5.9-6.0% dry body weight per day in 1981. A sharp decline in the abundance of adolescent and adult euphausiids over the middle shelf during the spring bloom period when food appeared to be abundant suggests that predation effectively controls the euphausiid population. -from Author
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Stomach contents from a total of 439 Short-tailed Shearwaters taken at 94 stations in the Okhotsk Sea, North Pacific Ocean and Bering Sea during the summer, 1970-1978, were examined in order to determine the food and feeding habits of this seabird.The diet for Short-tailed Shearwaters varied according to sea area. Overall it consisted mainly of small-sized organisms such as larval and juvenile fish and squid, euphausiids, amphipods, copepods, shrimp, and Thecosomata, all of which are usually abundant in the surface layer of the pelagic environment. The occurrence of the herbivorous copepod, Calanus cristatus (Copepodite V stage), in some stomach samples suggests that the Short-tailed Shearwater sometimes also depends upon zooplankton of lower trophic levels.Based on the results of this study the feeding biotope of the Short-tailed Shearwater, when wintering in the Subarctic Pacific Region, demonstrates high adaptability in prey and pelagic environment. These features enable this species to attain an immense population size in the Northern Hemisphere.
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Mass-mortalities of short-tailed shearwaters ( Puffinus tenuirostris) occurred in 1983-1985, along the Pacific coast of central and northern Honshu, Japan, from late May to mid June. The carcass numbers were annually counted along three 20 km courses at three localities on the Pacific coasts; Atsumi Peninsula in Aichi Prefecture, Kujukuri Beach in Chiba Prefecture and Ogawara Coast in Aomori Prefecture. At Kujukuri Beach, annual carcasses were 32.5, 44.0 and 26.8/km from 1983 to 1985; these were two to four times as many as in the previous years, 12.3±5.7/km (1977-1982). Similarly, high values of 16.4 and 47.6/km were recorded at Atumi in the first two years, with lower number in 1985. At Ogawara Coast few carcasses were found in the first two years, but increased in 1985. This northward shift of mortality was likewise indicated by answers to our questionnaire issued to wildlife divisions of Pacific coast prefectures from Okinawa to Hokkaido. Of 2, 258 carcasses collected, more than 99% were considered to be young of the year with a mean weight of 286.4±22.3 (SD) gr. (n=59), about 110 g lighter than that of the live birds, 399.4±32.7 (SD) gr. (n=22), captured in fishing nets. The main cause of mass-mortality of young birds was due to emaciation. Since the mass-mortality of this species has been recorded in 1964 and 1973-1975 in Japan and in 1934, 1942 and 1954 in Australia, a rough ten-year periodicity could be expected, and the recent one of 1983-1985, reported here, supports this theory.
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Measurements of the spectral scattering and attenuation properties of coccolithophores (Emiliania huxleyi; clone 88E) and their associated coccoliths were made for three growth phases as well as for acidified cultures. These measurements allow a clean separation and determination of the optical effects of the various components. The beam attenuation cross sections (m² particle⁻¹) were found to be 8.4E-12, 2.6E-10, and 4.9E-11 for coccoliths, plated cells, and naked cells, respectively, at 440 nm. The spectral dependence of these factors followed a power law dependence, with a wavelength exponent of −1.9, 0.42, and −0.52 for the coccoliths, plated cells, and naked cells. The volume scattering functions for all appeared similar; however, the backscattering cross sections (m² particle⁻¹) at 456 nm were 1.4E-13, 6.7E-12, and 9.9E-13, respectively. The wavelength dependence of this parameter also followed a power law and was −1.4, −1.2, and −1.0. Overall, these results show that optical properties of a coccolithophore bloom are sensitive to the coccolith:cell ratio and can vary between and within blooms.
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1) The mortality of the Shearwaters in 1975, especially the Slenderbilled Shearwaters, were surveyed by the questionnaire method. The questionnaires were recovered from 263 persons (Recovery rate 13%), and more than 80% of them were from the members of Japan Wild Birds Society and Japanese Association for Preservation of Birds.2) The number of the dead shearwaters, according to the questionnaire of 1975, was approximately 19.768, the number of birds found in emaciated condition was 787, and the number found afloat was 14, 924. The recorded species were Slender-billed Shearwater Puffinus tenuirostris (account for 76, 2% of all dead and emaciated Shearwaters), Streaked Shearwater Calonectris leucomeas (account for 0.8%), Sooty Shearwater Puffinus griseus (account for 0.6%), Pale-footed Shearwater Puffinus carneipes and Wedged-tailed Shearwater Puffinus pacificus. (Among these, the species account for 22.4% of all the dead and emaciated birds were indistinct.)3) The dead Shearwaters were distributed in the districts along the Pacific Coast, from Kagoshima Prefecture to Hokkaido. The distribution of the dead Slender-billed Shearwaters that have the highest death rate cover 15 Prefectures from Kagoshima Prefecture to Hokkaido.4) According to the survey, most of the dead Slender-billed Shearwaters were recorded from the beginning of May to the beginning of July, and the time of great mortality seems to lag in the northern districts.Throughout the country, the times of highest shearwater mortality were from the beginning (56.2%) to the middle (26.2%) of June.5) Many of the people who have answered the questionnaires reported that the stomachs were empty when they dissected the dead shearwaters. However, few of them reported that such things as coal tar, sand, pebbles, piece of wood and styrofoam etc. were found in the stomach. According to the result of the dissection in 5 cases, there were no external wounds, and all were juveniles.6) It was reported that the shearwaters were found feeding in the corfs in some part of the districts.7) The mortality of the Slender-billed Shearwaters before 1975 has been recorded mainly in 1973 and 1974, and in 1962, 1964, 1969, 1970 and 1971, mortality was recorded only in one part of the district (City of Sendai). Especially, the record of 1964 accord with the report of Dr. Nagahisa Kuroda on the mortality of the Shearwaters (1967).Also, the record of 1964 showed that the dead Shearwaters were distributed as far north as the Tohoku District.8) The distribution of the dead Slender-billed Shearwaters in 1974 and 1975 further extended to Tohoku and Hokkaido compared with the record of the distribution of 1966 and 1973, and there seemed to be a tendency that the time of the mortality lag according to the extension of the distribution.
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During the late summer of 1997, for the first time ever recorded, most of the continental shelf of the eastern Bering Sea was covered by aquamarine waters (Figure 1), resulting from a massive bloom of coccolithophores (Figure 2). Light reflecting off the calcium carbonate plates of the flagellated coccolithophores gave the water its anomalous color, which was first observed in July. The bloom was also clearly visible from space, as shown by some of the first images from the multispectral sea-viewing wide-field-of- view sensor (SeaWiFS) scanner in September.Light penetration into the water column, essential for primary production by diatoms and other phytoplankton, was markedly reduced. This shift potentially altered the trophic dynamics throughout the food web of one of world's most productive ecosystems.
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Starlings (Sturnus vulgaris) collected during mid-winter from a 2,800-km longitudinal range in the eastern United States showed significant geographic variation in body weight, feather weight, wing length, culmen length, tarsus length, dry weight, lean dry weight, lipid weight and lipid index. Total lipid reserves and indices were greatest at middle latitudes. Starlings from the central part of the study area were significantly larger than those at either northern or southern extremes as measured by wing length, body weight and lean dry weight. Insulation, as measured by weight of body feathers per unit of surface area, increased with isophane, an index of regional temperature, but morphometric measures were generally less interpretable.
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For the Hooded Crow (N = 537), the ratio between body weight and bill height proved to be a better indicator of the amount of abdominal fat than either body weight alone, or the ratio of body weight to other size dimensions, e.g. wing, tail, tarsus, or bill lengths. The ratio of body weight to bill height, in particular, is to be recommended if either the age or sex, or both, of a bird are unknown, and the possible reason for this is discussed.
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Dead gulls marked either with leg rings or bill tags were dropped in the North Sea to simulate a mortality incident. Recovery rates were 0.3% for rings and 19.3% for the more durable and conspicuous tags. Recovery places were mainly in Norway but spread between 58° and 70°N. Reports were also spread over a long time with a median interval of 142 d. Most bodies had probably decomposed in six months and many in less so many reports probably referred to plastic markers alone. The distribution of recoveries was broadly in line with that predicted by wind vector analysis. Bodies moved at 11.9% of the wind speed as measured at Bergen, but it was 3.0 times more windy in the North Sea, so the real relative drift rate was 4.0%. It is concluded that a major bird mortality incident in the North Sea would not readily be detected or measured by emergency beached bird surveys.
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Total body electrical conductivity (TOBEC) and near infrared interactance (IRI) are noninvasive techniques with potential utility for monitoring body composition of free-ranging birds or captive experimental subjects. I used live Northern Bobwhites (Colinus virginianus) to validate these methods for estimation of total body lipid. Total body electrical conductivity and IRI measurements were compared with body composition as determined by solvent extraction of carcasses. I measured IRI at three body sites (subscapular, pectoralis, and subfemoral) on 42 bobwhites. Only the subscapular and pectoralis sites yielded IRI measurements that were significantly correlated with percent body lipid, but IRI from these sites explained only 17.5% and 10.0% of the variation in percent body lipid, respectively. The cause of the low correlations is unknown, but it was not a function of differences in subject posture or light-wand position between replicate measures on the same subject. Total body electrical conductivity measurements explained 92% of the variation in lean body mass in a sample of 62 bobwhites. Measurements were affected by small differences in subject movement and position in the measurement chamber. There was no significant difference in TOBEC of subjects with or without aluminum leg bands. Measurements obtained from the same subjects with two different SA-1 TOBEC analyzers were not significantly different. The residuals about the regression of TOBEC against lean body mass were not correlated significantly with body temperature, but were significantly correlated with hydration. Total body electrical conductivity explained 99.1% of the variation in lean body mass when only those data from normally hydrated and properly restrained subjects were included (n = 38). Estimated body lipid from TOBEC measurements was highly correlated with total body lipid (R = 0.96) as determined by solvent extraction. The 95% confidence limits from the inverse regression procedure for the estimate of total body lipid from TOBEC measurements were ±4.75 g at 25 g lipid, ±4.85 g at 10 g lipid, and ±5.62 g at 50 g lipid. Estimated total body lipid from TOBEC measurements was on average within 10% of total body lipid from solvent extraction. Although IRI analysis failed to yield a suitable index to body composition, TOBEC analysis provided an accurate estimate of total body lipid in live bobwhites.
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On May 30 and 31, 1964, Umitaka Maru, a training ship of Tokyo University of Fisheries, cruised from Uraga, Kanagawa Prefecture to Osaka. On and after May 20, newspapers reported that great numbers of Slender-billed Shearwater, Puffinus tenuirostris have been washed ashore between Kiushiu and Mie Prefectures, western Pacific coast of Japan.Comparatively abundant Slender-billed Shearwaters were observed during the cruise and four specimens were obtained, of which two were weakened birds strayed on board and two others were dead birds drifted on the sea east of Kashinozaki, Wakayama Prefecture.
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The authors found a great number of dead or dying Slender-billed Shearwaters, Puffinus tenuirostris, in Suruga Bay from May 23 to 26, 1964, when the plankton survey was made on the "Tansei Maru" of Ocean Research Institute, University of Tokyo. This phenomenon was observed almost in all parts of the bay, especially in the inner part. Fourteen dead or dying birds were observed in area, 150m in width and 10km in length, in the inner part. From this observation the total number of birds in this inner part was estimated at more than 4, 000. Four specimens were used for dissection. One of these was alive and three were dead when they were collected. Blood was vomitted in two specimens. Stomach contents were absent in three specimens and stomach bleeding was found in two and cloaca was filled with feces in one. The southern wind blew ashore frequently in this period, especially strongly on May 23 and the Kuroshio current was shifted to the south and water temperature was lower than usual. The cause of this mass martality could not perfectly be clarified, but judging from the results of dissection and meteorological and oceanographical data, the unusual sea current of this year caused the scarcity of food in the normal distribution sea area of this shearwater and would have forced them to prostraction, while the strong southern winds that followed drifted exhausted birds to the shore. The authors have no definite evidence to conclude whether this mass mortality was caused by some diseases.
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The diet of the Short-tailed Shearwater Puffinus tenuirostris was studied over two breeding seasons. Of 307 food samples collected, 74% contained fish, 56% crustaceans, and 13% cephalopods. Birds ate at least seven species of euphausiids, seven species of fish and two species of cephalopods. Most commonly encountered prey were Nyctiphanes australis, a euphausiid; and Paraprone clausi, a pelagic amphipod. In both years the diet changed from a crustacean diet befo