bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comment on transfer efficiencies
Authors: BAUMANN MICHAEL 
Published: October 2007

ABSTRACTThis paper discusses the validity of several assumptions in a recent publication on the primary production required to sustain the annual world fish catch of £120 million t. A transfer efficiency between trophic levels in aquatic ecosymms of 15% results in the primary production requirement of 2.6% of the total primary production to sustain the world fish catch, not 8% as reported from calculations with a transfer efficiency of 10%. The importance of accurate estimates of predation efficiency and trophic level is shown.
Species associations of epipelagic nekton of the North Pacific Ocean, 1978–1993
Authors: PEARCY WILLIAM G. , FISHER JOSEPH P. , ANMA GEN , MEGURO TOSHIMI 
Published: October 2007

ABSTRACTStrong latitudinal gradients in species composition were revealed by two‐way indicator species analysis (TWINSPAN) and detrended correspondence analysis (DCA) of 41 species of epipelagic fishes and squids in 513 gillnet collections by research vessels of Hokkaido University over a huge area of the northern North Pacific during the summers of 1978–1993. Salmonids inhabited northern subarctic water and skipjack tuna (Euthynnus pelamis) and flying squid (Ommastrephes bartrami) inhabited the region of the Subarctic Boundary, but distinct boundaries between species groups and sample groups were lacking, largely because abundant species, such as Pacific saury (Cololabis saira) and Pacific pomfret (Brama japonica), migrated across most of this region during the summer. Longitudinal differences were not pronounced, but some species, including Japanese sardine (Sardinops melanostictus) and Japanese anchovy (Engraulis japonicus), were only found in the western Pacific. Pacific saury was more common in the western Pacific, whereas sockeye salmon (Oncorhynchus nerka) was concentrated in the eastern Pacific. Interannual fluctuations in the latitude of species groups were most closely correlated with changes in sea surface temperatures. In the western Pacific, 1982, 1983, 1985, 1987‐88, and 1992‐93 were cool years when subarctic and transitional assemblages were found farther to the south than other years. Temperature and salinity at various depths were highly correlated with each other and with first‐axis DCA ordinations scores. Long‐term trends in community structure were not apparent during the 1.6 decades.
New data about communities of plankton and nekton of the far‐eastern seas in connection with climate‐oceanological reorganization
Authors: SHUNTOV V. P. , DULEPOVA E. P. , RADCHENKO V. I. , LAPKO V. V. 
Published: October 2007

ABSTRACTThe present condition of the pelagic communities of the far‐eastern seas is considered. From the beginning of the 1990s, significant changes, caused by a replacement of the climate‐oceanological period, have occurred in the structure of plankton and nekton communities. The current situation is assumed to be the beginning of a period similar to one in the 1940s‐1960s.
Sea birds as proxies of marine habitats and food webs in the western Aleutian Arc
Authors: SPRINGER ALAN M. , PIATT JOHN F. , VLIET GUS VAN 
Published: October 2007

ABSTRACTWe propose that ocean conditions of the Near Islands in the western Aleutian Arc mimic those of the shallow continental shelf of the eastern Bering Sea to the extent that the marine community, including assemblages of forage fishes and their avian predators, has distinctly coastal characteristics. In contrast, marine avifauna and their prey at neighbouring Buldir Island are distinctly oceanic. For example, at the Near Islands, the ratio of thick‐billed to common murres, Vria lomvia and U. aalge, is low and black‐legged kittiwakes, Rissa tridactyla, but not red‐legged kittiwakes, R. brevirostris, nest there. Diets of murres and kittiwakes are dominated by sand lance, Ammodytes hexapterus, an abundant coastal species. At Buldir Island, thick‐billed murres greatly outnumber common murres, red‐legged kittiwakes and black‐legged kittiwakes are both abundant, and diets of the birds consist primarily of oceanic squid and lantern‐fish (Myctophidae). This mesoscale difference in food webs is apparently a consequence of the local physiography. A broad escarpment on the Near physiographic block creates a comparatively expansive, shallow, shelflike habitat around the Near Islands, where a pelagic community typical of coastal regions flourishes. Buldir Island is the only emergent feature of the Buldir physiographic block, with little shallow water surrounding it and, apparently, little opportunity for other than oceanic species to exist. Patterns in the distribution of fishes, and thus of sea birds, throughout the Aleutian Islands might be largely explained by the presence or absence of shelf‐like habitat and the relationship between physical environments and food webs. In the larger context of fisheries oceanography, this model for the Aleutian Islands improves our ability to interpret physical and biological heterogeneity in the ocean and its relationship to regional community dynamics and trends in the abundance and productivity of individual species at higher trophic levels.
Survival and growth of sardine larvae in the offshore side of the Kuroshio
Authors: ZENITANI HIROMU , NAKATA KAORU , INAGAKE DENZO 
Published: October 2007

ABSTRACTAfter 1984 the major spawning of the Japanese sardine, Sardinops melanostictus, has been observed to occur in the offshore waters, where the survival of early‐stage larvae (4–10 mm in length) is questionable. The main objective of this study is to estimate the growth and survival rates of the early‐stage larval cohort in the offshore side of the Kuroshio Current.A radar‐reflecting buoy with a surface drogue was launched to tag a patch of larvae, and the patch was traced for 3 days in March 1991. The survival rate of the early‐stage larval cohort was calculated from the change in density during the survey. The range of the instantaneous mortality rate was from 0.83 to 1.11 day, a survival rate of32‐44%day‐1.The mean density of the smaller larvae (4–6 mm in length) decreased more rapidly than that of the larger larvae (6–10 mm in length) during the sampling period.The survival rate of the first‐feeding larvae in the offshore region seemed to be lower than that of the post‐flrst‐feeding larvae. However, the growth rates of the first‐feeding larvae's survivors in the region were higher than those of the post‐first‐feeding larvae's survivors. The first‐feeding larvae in the offshore region seemed to survive when the growth rate of the larvae was high.
Walleye pollock recruitment in Shelikof Strait: applied fisheries oceanography
Authors: KENDALL ARTHUR W. , SCHUMACHER JAMES D. , KIM SUAM 
Published: October 2007

ABSTRACTFisheries‐Oceanography Coordinated Investigations (FOCI) is a National Oceanic and Atmospheric Administration (NOAA) research programme seeking to understand recruitment processes of commercially exploited Alaskan fishes. The FOCI is mainly comprised of scientists at the Pacific Marine Environmental Laboratory and the Alaska Fisheries Science Center who study both the biotic and abiotic environment, including processes within larval patches through integrated field, laboratory, and modelling studies. The initial focus of studies was walleye pollock (Theragra chakogramma) spawning in Shelikof Strait, Gulf of Alaska. The choice of this population for our research was based on development of a large fishery and the substantial variation in recruitment that was observed in the late 1970s and early 1980s. Also, the early life history of this population is quite predictable and restricted both temporally and spatially. Walleye pollock spawn consistently in a small part of Shelikof Strait in early spring from which a large patch of eggs and later larvae is produced. In most years this concentration of larvae drifts to the south‐west through the strait during April and May. Large numbers of larvae are often found in eddies which frequent the area and we have observed improved feeding conditions for larvae, in as opposed to out of eddies. We have found that first‐feeding larvae have higher survival rates during calm periods, rather than in storms, and that in many years recruitment is largely set by the end of the larval period, although in some years age‐0 juvenile mortality is also important. FOCI now generates information that is being used for management of this resource.
The plankton of Shelikof Strait, Alaska: standing stock, production, mesoscale variability and their relevance to larval fish survival
Authors: NAPP JEFFREY. M. , INCZE LEWIS S. , ORTNER PETER B. , SIEFERT DEBORAH L. W. , BRITT LISA 
Published: October 2007

ABSTRACTPhysically‐mediated variations in production, standing stock and distribution of plankton have a significant impact on the growth and survival of larval fishes in Shelikof Strait. We integrate descriptions of mechanisms that control the distribution and regional production of planktonic organisms with mechanisms that influence survival of early life history stages of marine fish, especially the locally abundant walleye pollock, Theragra chalcogramma.The timing of the spring phytoplankton bloom is more variable than the regular appearance of pollock larvae, and is affected by variability in the winter to spring storm season transition, stratification in the Alaska Coastal Current (ACC), and cloudiness. The spring bloom occurs first in the ACC, fuelling local production of copepod nauplii, the main prey item of early larval pollock. Shelikof Strait zooplankton standing stock is higher in the ACC than the surrounding Coastal Water (CW) throughout the spring. This is the result of local production as well as regional production which occurs upstream of the strait. Mesoscale features associated with the ACC (fronts, meanders, and eddies) determine the distribution of plankton through physical convergence, and reduced dispersion and transport. Evidence for enhancement of planktonic production in these features is lacking. Thus the ACC plays a strong role in determining plankton production, standing stock, and distribution in the Shelikof region.The strength of the relationship among plankton, planktonic production, larval pollock growth and survival, and fisheries recruitment is variable. The plankton is only one of several key variables that affect eventual recruitment to the pollock fishery.
Physical transport of young pollock larvae (Theragra chalcogramma) near Shelikof Strait as inferred from a hydrodynamic model
Authors: HERMANN ALBERT J. , RUGEN WILLIAM C. , STABENO PHYLLIS J. , BOND NICHOLAS A. 
Published: October 2007

ABSTRACTAn advective model was used to simulate the drift of larval walleye pollock (Theragra chalcogramma) over a 40‐day period (late April through early June) near Shelikof Strait, Alaska. This model was used: (i) to assess how much of the observed change in larval positions during that period can be explained by transport at fixed depth; (ii) to demonstrate that observed change can be related to mean large‐scale meteorological forcing; and (iii) to investigate accumulation of larvae in specific areas near the coast. Based on availability of larval and circulation data, three years were studied: 1988, 1989 and 1991. Velocity fields generated from a hydrodynamic model driven by winds and runoff were used to advect particles seeded in accordance with observed larval distributions in late April of each year. The modelled larvae were tracked at 40 m depth, corresponding to the mean depth of sampled larvae and the depth of neutrally buoyant drifters employed in field studies. Specific features observed in late May larval surveys were reproduced by the model, such as the accumulation of larvae in a shoal area downstream of the strait. Differences among the modelled years include extensive flushing of larvae to the south‐west in 1988 and 1991, vs. limited flushing in 1989. These differences appear related to the mean large‐scale atmospheric pressure patterns for April‐May of those years.
Observed patches of walleye pollock eggs and larvae in Shelikof Strait, Alaska: their characteristics, formation and persistence
Authors: STABENO PHYLLIS J. , SCHUMACHER JAMES D. , BAILEY KEVIN M. , BRODEUR RICHARD D. , COKELET EDWARD D. 
Published: October 2007

ABSTRACTUsing observations from 38 ichthyoplankton surveys conducted near Shelikof Strait, Alaska between 1979 and 1992, we characterized the horizontal distribution and spatial patchiness of the early life stages of walleye pollock (Theragra chalcogtamma). Lloyd's index of patchiness ranged from 3.9‐6.1 for eggs and 3.9–16.2 for larvae. This index was size (age) dependent: low for eggs, high for newly hatched larvae, then decreasing through late larval stage. By the early juvenile stage, patchiness increased as pollock began to school. The percentage of larvae in a patch (defined as the percentage of larvae present at stations where larval counts exceeded the mean by one standard deviation during the given survey) varied greatly (26–92%). Larval distributions were used to deduce physical mechanisms responsible for patches. Three categories of patches were identified: those created by interaction of larvae with time‐dependent currents, those in the vicinity of Sutwik Island, and those associated with eddies. Simulation experiments were utilized to examine processes influencing patch formation and the role of larval swimming. Between 5 and 6 weeks after hatching, larvae have swimming abilities that enable them to maintain a patch already created by physical mechanisms.
Walleye pollock egg distribution and mortality in the western Gulf of Alaska
Authors: BRODEUR RICHARD D. , PICQUELLE SUSAN J. , BLOOD DEBORAH M. , MERATI NAZILA 
Published: October 2007

ABSTRACTWe examine the distribution and mortality of walleye pollock (Theragra chakogramma) eggs in the western Gulf of Alaska. Most pollock eggs were found in mid‐water, with low proportions in the neustonic and epibenthic layers during all years of sampling. A silhouette camera towed through a high egg density region provided new information on small‐scale spatial distributions and provided density estimates at two depth layers similar to those of depth‐discrete net sampling. Annual egg production curves and natural mortalities were estimated for 1987‐92 based on the abundance of several cohorts relative to their production rate. Production during 1989 and 1990 was lower than in the other four years but 1988 was the only year to show markedly different (higher) mortality than the rest. Fertilization rate was generally very high (>99%) but several collections early in the season contained a substantial fraction of unfertilized eggs. Invertebrate egg predation was mainly due to euphausiids and was variable among locations and years. Egg cannibalism by adult pollock on the spawning grounds was inconsequential (< 1% for all years) compared to invertebrate predation.
Mortality of larval walleye pollock Theragra chalcogramma in the western Gulf of Alaska, 1988–91
Authors: BAILEY KEVIN M. , PICQUELLE SUSAN J. , SPRING STELLA M. 
Published: October 2007

ABSTRACTMortality rates of larval walleye pollock Theragra chakogramma were estimated from larval survey data from 1988 to 1991. Mortality estimates were based on cohort‐specific losses between occupations of survey grids. Interannually, estimates of early feeding stage larval mortality rates ranged over an order of magnitude, from 0.045–0.43 day‐1, and declined sharply with age. There is some evidence that mortality rates of early feeding larvae tend to be negatively correlated with temperature and postively correlated with wind mixing.
A review of the distribution, ecology and population dynamics of age‐0 walleye pollock in the Gulf of Alaska
Authors: BRODEUR RICHARD D. , WILSON MATTHEW T. 
Published: October 2007

ABSTRACTThis review paper synthesizes published research and unpublished data on the abundance and distribution patterns, ecology and population dynamics of walleye pollock (Theragra chalcogramma) during their first year of life (age‐0) in the Gulf of Alaska. Distribution patterns have been described using mainly trawl catches, but recently, acoustic methodology has been employed, especially in examining vertical distributions. Although age‐0 pollock are found throughout the Gulf, the highest catches occurred west of Kodiak Island. Pollock are pelagic for at least their first 6 months of life but show an ontogenetic increase in depth distribution superimposed on a pronounced diel vertical migration at a larger size. Daily growth rates are variable depending on year, season and area, and growth generally ceases during the winter. The diet of age‐0 pollock shifts from mainly copepods in early juveniles to euphausiids by fall, with epibenthic organisms becoming important during the winter months. Feeding occurs mainly at night in surface waters. Age‐0 pollock are most frequently associated with gelatinous zooplankton (medusae) and older pollock. Many predators on age‐0 pollock have been identified; the most important are arrowtooth flounder (Atheresthes stomias), adult pollock, puffins (Fratercula spp.), murres (Una spp.), harbor seals (Phoca vitulina richardsi) and Steller sea lions (Eumetopiasjubatus). Modelling provides some insight into the population dynamics of these juveniles and environmental conditions which interannually affect their survival. These results are discussed relative to the importance of age‐0 pollock in the recruitment of this species and to their role in the pelagic ecosystem.
Cohort survival patterns of walleye pollock, Theragra chalcogramma, in Shelikof Strait, Alaska: a critical factor analysis
Authors: BAILEY KEVIN M. , BRODEUR RICHARD D. , HOLLOWED ANNE B. 
Published: October 2007

ABSTRACTA series of age‐specific life tables for walleye pollock (Theragra chalcogramma) in the western Gulf of Alaska was compiled for the 1980‐91 year classes. The life tables were utilized to perform an exploratory key factor analysis to examine the timing of critical periods in the recruitment process, evidence of density‐dependence at different stages and trends in mortality rates. Early larval mortality was significantly correlated with generational mortality (In recruits/spawning bio‐mass), but patterns in juvenile mortality also were similar to generational mortality and in some years were clearly dominant in determining the fate of a cohort. Density‐dependent mortality, based on the correlation between mortality and initial abundance, was indicated only for the late larval to early juvenile stage. Time trends were marginally significant for juvenile mortality. It is speculated that the observed increase in juvenile mortality is associated with increasing abundance of arrowtooth flounder. Weaknesses in the data base are discussed; these along with the short time series involved make our conclusions tentative and subject to further study. We hypothesize that pollock recruitment levels can be established at any life stage depending on sufficient supply from prior stages, a type of dynamics which can be termed supply dependent multiple life stage control.
Change in chum salmon (Oncorhynchus keta) stomach contents associated with fluctuation of pink salmon (O. gorbuscha) abundance in the central subarctic Pacific and Bering Sea
Authors: TADOKORO KAZUAKI , ISHIDA YUKIMASA , DAVIS NANCY D. , UEYANAGI SHOJI , SUGIMOTO TAKASHIGE 
Published: October 2007

ABSTRACTThe abundance and stomach contents of salmonids (Oncorhynchus spp.) and the biomass of prey organisms were examined in the central subarctic Pacific and Bering Sea in the summer of 1991 and 1992. Salmonids were caught by surface longline using the same level of fishing effort. Chum (O. keta) and pink (O. gorbuscha) salmon were the predominant species, representing 44% and 36% sof the total catch (n = 1275) in 1991. In 1992, chum salmon composed 85% of the total catch (n = 603), but the catch of pink salmon decreased to 1% of the total catch due to the odd/even year fluctuation of Asian pink salmon abundance in the study area. It was found that chum salmon changed their dominant diet from gelatinous zooplankton (pteropods, appendicular‐ians, jellyfishes, chaetognaths, polychaetes and unidentified materials) in 1991, when pink salmon were abundant, to a diet of crustaceans (euphausiids, cope‐pods, amphipods, ostracods, mysids and decapods) in 1992, when pink salmon were less abundant. Local crustacean biomass (wet weight; mg m‐3) had significant negative correlation with the CPUE (catch number per 30 hachi) of pink salmon in 1991 (r = ‐0.586; P = 0.026) and that of chum salmon in 1992 (r =–0.616; P = 0.014). There may be a limitation in the available prey resource for production of salmonids.
Decadal variation in the trans‐Pacific migration of northern bluefin tuna (Thunnus thynnus) coherent with climate‐induced change in prey abundance
Authors: POLOVINA JEFFREY J. 
Published: October 2007

ABSTRACTNorthern bluefin tuna, Thunnus thynnus, apparently spawn only in the western Pacific and a portion of the juveniles migrate to the eastern Pacific. During the past decade, catches of northern bluefin in the eastern Pacific have declined. One possible cause for this decline, proposed by bluefin stock assessment studies, is a decline in the proportion of bluefin that migrate out of the western Pacific. This hypothesis is examined with several indices of the relative abundance of bluefin tuna in the western and eastern Pacific. These indices suggest a decline in the proportion of bluefin migrating to the eastern Pacific since 1977. This period of reduced bluefin migration coincides with a period when a prey of bluefin, Japanese sardine, Sardinops melanosticta, were abundant off Japan. It is hypothesized that in years when sardines are abundant off Japan, a higher proportion of bluefin stay in the western Pacific compared with years when sardines are scarce. Currently, the adun‐dance of sardines off Japan is declining. If this decline continues, this hypothesis predicts an increase in bluefin migrating north of Hawaii and into the eastern Pacific.
Feeding success and survivorship of Arctic cod larvae, Boreogadus saida, in the Northeast Water polynya (Greenland Sea)*
Authors: MICHAUD JOSÉE , FORTIER LOUIS , ROWE PETER , RAMSEIER RENÉ 
Published: October 2007

ABSTRACTWe tested the hypothesis that enhanced feeding success and survivorship of Arctic cod larvae in the Northeast Water polynya (Greenland Sea) are associated with high densities of their zooplankton prey in areas of low sea ice concentration. From late May to early August 1993, first‐feeding yolk‐sac larvae (6.5–8.5 mm long) were collected primarily along the coast and over shallow banks in the polynya, whereas post yolk‐sac larvae (8.5–14 mm) were more uniformly dispersed over the sampling area. Arctic cod larvae < 14 mm fed almost exclusively on copepod nauplii (74% of total prey number) and copepod eggs (16%). Feeding success was defined as the residuals of the regression of the number of prey ingested against larval length. Nauplii density varied from 9600 to 731300 nauplii m‐2(equivalent to 0.16 to 12.2 nauplii 1‐1) but, contrary to our hypothesis, seldom limited the feeding success of Arctic cod larvae. Water temperature was the best predictor of feeding success in larvae of all sizes. First‐feeding success and survivorship were low for larvae hatched before mid‐July, and improved thereafter as surface temperatures increased in the open waters of the polynya. There was no relationship between feeding success and irradiance or wind. Assuming a fixed spawning season, it is concluded that a larger fraction of the newly hatched larvae would experience adequate temperatures in years when the polynya opens early. Based on this conclusion, we propose that the timing of the opening of polynyas is a critical determinant of year‐ class strength in Arctic cod, a key species in the Arctic food web.