bluuebunny/crossref_metadata_2025_split huggingface dataset:
A numerical analysis of population dynamics of the sand lance (Ammodytes personatus) in the eastern Seto Inland Sea, Japan
Authors: KIMURA SHINGO , KISHI MICHIO J. , NAKATA HIDEAKI , YAMASHITA YOH 
Published: October 2007

ABSTRACTThe Japanese sand lance (Ammodytes personatus) population in the Seto Inland Sea shows large fluctuations every few years. Its recruitment to the fishery resources is much more dependent on the survival rate of 0‐age fish than is the case for other fish species because 0‐age fish directly recruit to next‐year spawning adults. Since the 0‐age fish population depends on its larval population, which is easily influenced by natural and human impacts, high larval mortality due to predation by adults and high dispersion of larvae by wind‐driven currents from spawning grounds to other locations can have very important effects on stock fluctuations. A numerical model of population dynamics of the sand lance in the eastern Seto Inland Sea was developed that focuses on wind‐induced transport and adult predation of the larvae. The model successfully simulated the two‐year periodic fluctuation and was consistent with actual fluctuations in fishery catches. It suggests that the various coefficients given in the model are appropriate to explain the actual population dynamics of the sand lance. The model shows that adult predation on the larvae plays a very important role in the two‐year periodic fluctuation, and the maximum predation rate is estimated to be ten individuals per day. Wind‐induced transport modifies the impact of this predation. Variances in the two‐year periodic fluctuation become smaller with weaker westerly wind velocity. The appropriate transport rates from Bisan Strait and the Harima‐nada Sea are estimated to be 0.04 d‐1 and 0.01 d‐1, respectively.
Sardine and anchovy regime fluctuations of abundance in four regions of the world oceans: a workshop report
Authors: LLUCH‐BELDA D. , SCHWARTZLOSE R. A. , SERRA R. , PARRISH R. , KAWASAKI T. , HEDGECOCK D. , CRAWFORD R. J. M. 
Published: October 2007

ABSTRACTRegimes of high abundance of sardine (Sardinops sagax and Sardina pilchardus) have alternated with regimes of high abundance of anchovy (Engraulis spp.) in each of the five regions of the world where these taxa co‐occur and have been extensively fished. When one taxon has been plentiful, the other has usually been at a reduced level of abundance, and vice versa. Changes in the four heavily fished regions that support S. sagax–the Japanese, Californian, Humboldt, and Benguela systems–from a regime dominated by one taxon to a high level of abundance of the other have occurred more or less simultaneously. In the Pacific Ocean, sardines have tended to increase during periods of increasing global air and sea temperatures and anchovies to decrease. The Japanese system is dominated by sardines to a greater extent than the other systems, and sardines off Japan appear to increase as the Kuroshio Current cools. At the eastern edge of the Pacific Ocean, sardines colonize cooler areas during periods of warming. The Benguela system is out of phase with the three Pacific systems. The four systems all appeared to be in a state of flux in the 1980s. Increased abundance of the subdominant taxon is often one of the first signs of change. Sardines are relatively sedentary in refuge areas when scarce but change behavior to become highly migratory and colonize cooler areas when abundant. Anchovies, by contrast, expand around a fixed geographic center.
Modeling the transport and survival of Japanese sardine larvae in and around the Kuroshio Current
Authors: KASAI AKIHIDE , KISHI MICHIO J. , SUGIMOTO TAKASHIGE 
Published: October 2007

ABSTRACTWe have numerically modeled the advection and diffusion of sardine eggs and larvae to investigate the larval transport processes of Japanese sardine from the spawning grounds by the Kuroshio.The results indicated that the offshore drift current induced by the winter monsoon and the location of the spawning ground have significant effects on the survival of the Japanese sardine. The contribution of the drift current, the distance of the spawning ground from the Kuroshio axis, and the eddy diffusivity to the larval retention in the coastal area is approximately expressed by the following equation: where R is the retention rate in the coastal area, a the variance of initial distribution of eggs, T the time after the eggs were spawned, – V0 the velocity of the wind‐induced offshore current, y0 the distance of the center of the spawning area from the Kuroshio axis, and K the coefficient of horizontal eddy diffusivity.The year‐to‐year variation in larval survival rates stimulated by the two‐dimensional model are consistent with those estimated previously by using field data of egg and larval abundance during 1978–1988.
Observation and analysis of fishery processes: larval pollock at Shelikof Strait, Alaska
Authors: VASTANO ANDREW C. , INCZE LEWIS S. , SCHUMACHER JAMES D. 
Published: October 2007

ABSTRACTConditions affecting distributions of larval walleye pollock (Theragra chalcogramma) were examined at Shelikof Strait, Alaska, during springtime, 1986 and 1987. Abundance and distribution of larval pollock southwest of the Strait's southern entrance was determined with oblique plankton tows taken each year in May. Infrared images of sea surface temperature patterns were derived from AVHRR scenes obtained by NOAA satellites during each April and May. Pattern displacements between 24‐hour‐interval images were used to estimate surface motion. Each spring, measurements were taken by remote weather stations and ships, and a nearsurface current meter record was obtained during 1987. Treated as quasi‐synoptic, spatial relations between sets of surface temperature, surface flow, and larval pollock distributions show coincidences between submesoscale physical and biological features. The highest larval abundances occurred as patches within a cold plume (1986) and an eddy (1987). These confirm that physical features can retain larval pollock on the continental shelf. Observations are examined for evidence of physical and biological events that jointly can cause such coincidences and foster alternatives for survival during transport to nursery grounds. Explanations for presence of cohorts observed within the 1987 eddy are given in terms of spatial and temporal relationships evident between spawning and hatching areas, hatch date distributions, meanders, eddy generation and movement, background flow, and advection times. The observations, analyses, and results are consistent with the concept of a coupled, fluctuating biophysical process that can emulate variations in larval abundance and provide a multiplicity of system pathways for early‐life stages representations.
Long‐term variability in zooplankton biomass in the subarctic Pacific Ocean
Authors: BRODEUR RICHARD D. , WARE DANIEL M. 
Published: October 2007

ABSTRACTZooplankton collections from the subarctic Pacific were analyzed from two periods (1956–1962 and 1980–1989). In this report, we document: 1) a positive correlation between the intensity of winter winds and subsequent summer zooplankton biomass in the subarctic gyre within these periods; and 2) a doubling of zooplankton biomass and a similar increase in pelagic fish and squid abundance between these two periods of time. Some possible explanations for these changes are considered.
Environmental influences on the recruitment of Newfoundland/Labrador Cod*
Authors: HELBIG J. , MERTZ G. , PEPIN P. 
Published: October 2007

ABSTRACTThis paper investigates possible linkages between the environment and year‐class success of Newfoundland/ Labrador cod. Aspects of the physical environment relevant to recruitment are reviewed and the current knowledge of the patterns of spawning and larval occurrence is summarized. A critical review of investigations aimed at correlating recruitment with climactic fluctuations is made and concludes that these studies have been largely fruitless. A series of numerical simulations of particle drift are presented to investigate the potential importance of storms and to try to identify nursery grounds. These simulations suggest that Labrador Shelf eggs and larvae are segregated from Grand Banks eggs and larvae. Favorable storm tracks appear to be required for significant numbers of eggs and larvae to reach the bays of Northeast Newfoundland.
Size‐dependent predation on marine fish larvae by Ctenophores, Scyphomedusae, and Planktivorous fish
Authors: COWAN JAMES H. , HOUDE EDWARD D. 
Published: October 2007

ABSTRACTSize‐dependent predation rates on marine fish larvae by the ctenophore Mnemiopsis leidyi, scyphomedusa Chrysaora quinquecirrha, and planktivorous fish Anchoa mitchilli were estimated via experiments in 3.2 m3 me‐socosms. Predation rates on larvae of the goby Gobio‐soma bosci were estimated in relation to 1) length of larval prey, 2) presence or absence of alternative < 1 mm zooplankton prey, and 3) a predator‐prey interaction between the scyphomedusa and ctenophore. The consumption rate of larvae by the three predators generally declined as larval length increased. The ctenophore ate fewer (1.0 d‐1 per predator) larvae than did the medusa (7.8 d‐1 per predator) or bay anchovy (4.0 d‐1 per predator), but it consumed larvae in all size classes tested (3.0–9.5 mm SL). Predation by bay anchovy and the medusa was more size‐dependent: 3.0–5.0 mm larvae were most vulnerable. Fewer larvae were eaten by the ctenophore and bay anchovy when zooplankton alternative prey was available, but predation on larvae by the medusa was not influenced by alternative zooplankton prey. Consumption rate of fish larvae by the medusa was reduced 20–25% when the ctenophore was present as its alternative prey. An encounter‐rate model was developed and its parameters estimated from the experimental results. Model simulations indicated that the relationship between larval size and vulnerability is dependent on size, swimming speed, and behavior of both predators and larvae, and that bigger or faster‐growing fish larvae are not always less vulnerable to predation.
Changes in body growth of northern fur seals from 1958 to 1974: density effects or changes in the ecosystem?
Authors: TRITES ANDREW W. , BIGG MICHAEL A. 
Published: October 2007

ABSTRACTAnalysis of morphometric measurements collected from northern fur seals (Callorhinus ursinus) between 1958 and 1974 suggests a periodicity in growth rates and physical condition that may reflect underlying, large‐scale environmental changes. The data further suggest that fur seals attained larger body sizes as the breeding population on the Pribilof Islands declined over this 16‐year period. These conclusions are based on changes observed in the mean body size and condition index of mature females, changes in the annual growth rates of immature females, and changes in male and female growth curves. Interpreting annual changes in physical growth is complicated by inconsistencies in sampling between years and by large natural variations in body mass and body length within years. Commercial fisheries may influence the abundance of prey, and alter the physical growth of pinnipeds, but other physical and biological factors are probably more important determinants. Changes in body length and mass are useful indicators of per capita prey abundance and offer useful insights into conditions experienced by fur seals. Unfortunately, it is not possible to determine whether changes observed in growth are due entirely to changes in population density or whether they reflect changes in the ecosystem, or some combination of both.
Acoustic observations of fish schools and scattering layers in a Kuroshio warm‐core ring and its environs
Authors: AOKI ICHIRO , INAGAKI TADASHI 
Published: October 2007

ABSTRACTBiological sound scattering characteristics in a frontal region between warm and cold waters were examined at the southern edge of a Kuroshio warm‐core ring off Sanriku, the northeast coast of Japan. The scattering strength was low in the surrounding cold water and high in the warm‐core ring. The depth and thickness of sound‐scattering layers changed in accordance with the vertical structure of the water mass during the day or at night. Intense, thick scattering layers were observed on the warm‐water side of the front and farther inside the warm‐core ring. Fish schools were distributed in the mixed layer warmer than 17°C at depths of 10‐30m above the scattering layers on the warm‐water side of the front.
Considerations of stock structure of yellowfin tuna (Thunnus albacares) in the Indian Ocean based on fishery data
Authors: NISHIDA TSUTOMU 
Published: October 2007

ABSTRACTYellowfin stock structure in the Indian Ocean was studied by using industrial tuna longline fishery data. Three types of test variables were used to detect stock structure, i.e., CPUE, age‐specific CPUE, and coefficient of variation for size. Time‐series data of test variables were compiled for six sub‐areas that were arranged by dividing the whole region systematically along longitude lines every 20 degrees. Then time‐series data were smoothed by moving averages, and regressed by simple models. Patterns of time‐series trends were graphically and statistically compared to classify homogeneous sub‐area groups. Two assumptions were (a) that homogeneous stocks exist longitudinally and overlap in adjacent waters, and (b) that test variables within homogeneous sub‐area groups are equally affected, and hence patterns of the time‐series trends are similar. After graphical screening for significant sub‐area groups, analysis of covariance was applied to test homogeneity of regression parameters representing patterns of the time‐series trends. By classifying homogeneous sub‐area groups, stock structures were determined at the P <0.05 and P <0.50 levels. The P<0.50 level was recognized as a useful criterion for ‘weak’ test variables since masked or vague structures at the P <0.05 level were likely cleared at this level in many cases. Results of this study and past stock structure studies were reviewed and compared. It was concluded that there are two major and two minor stocks of yellowfin tuna. The two major stocks (the western and the eastern) are located at 40o‐90oE and 70o‐130oE respectively. The minor stocks are the far western and the far eastern stocks (the latter possibly being a part of the Pacific stock), which are located westward of 40oE and eastward of 110oE respectively. Neighboring stocks are intermingled in adjacent waters.
Hydrography and spatial variability in the size distribution of phytoplankton along the Kurile Islands in the western subarctic Pacific Ocean
Authors: TAGUCHI SATORU , SAITO HIROAKI , KASAI HIROMI , KONO TOKIHIRO , KAWASAKI YASUHIRO 
Published: October 2007

ABSTRACTSpatial variability in the size distribution of the phytoplankton community along the Kurile Islands, in the western subarctic Pacific Ocean, was investigated in terms of chlorophyll a concentrations in August and September, 1990. Analysis of dynamic height relative to 1,500 db and temperature–salinity diagrams at 50 m depth revealed five major oceanographic regions in this study area. The characteristic hydrography was clearly related to the surface distribution of chlorophyll a concentrations. As a warm core ring originating from the Kuroshio water was cooled by the surrounding water and meteorological conditions, its physical, chemical, and biological characteristics changed. Dominant picoplankton were replaced by a 10‐2 μm size fraction in the warm core ring. In the Oyashio region, physical structures were less variable but concentrations of chlorophyll a were most variable and cells larger than 10 μn dominated. An anticlockwise eddy found in the Oyashio water showed the highest concentration of chlorophyll a. In the Okhotsk region, the chlorophyll standing stock was small with a low percentage of cells larger than 10 μm in spite of high nitrate concentrations. Along the Kurile Islands and Hokkaido Island, the surface mixed layer was not well defined; surface nitrate concentrations were relatively high, and the chlorophyll standing crop was also high with low percentages of picoplankton. The spatial heterogeneity in the dominance of cells larger than 10 μm in phytoplankton assemblages seems to be clearly associated with the effect of nitrate availability determined by water structure.
δ13C‐δ15N values as indicators of trophic position and competitive overlap for Pacific salmon (Oncorhynchus spp.)
Authors: WELCH DAVID W. , PARSONS TIMOTHY R. 
Published: October 2007

ABSTRACTAnalysis of δ13C and δ15N isotope values for five species of Pacific salmon indicate that they form a trophic hierarchy on the high seas. On the basis of an analysis of these stable isotope ratios, chinook salmon feed at the upper end of the food chain and pink salmon at the lower end, in the sequence pink → sockeye → coho → chinook, with chinook and pink salmon separated by ca. 0.8 of a trophic level. Chum salmon occupy a peculiar position, with low δ13C values and high δ15N values, possibly reflecting an unusual diet that includes large amounts of gelatinous zooplankton (salps, ctenophoi;s, and medusae). Chum appear to occupy a unique trophic position, at a trophic level nearly as high as that of chinook but at the end of a different branch of the food chain. If true, the potential for trophodynamic competition with other salmon species is small. Our results suggest that the greatest potential for trophodynamic competition occurs within the pink‐sockeye‐coho grouping. A similar analysis, restricted to five stocks of North American sockeye, shows that four widely separated stocks have similar heavy isotope compositions but that the separation between these stocks is still statistically significant. The Chilko stock is strikingly different, however, suggesting that it is located in the central Gulf of Alaska, a region of intense upwelling. Circumstantial evidence supporting the possibility that the Chilko and other sockeye stocks are geographically separated within the Gulf of Alaska is reviewed.
The distribution of cod (Gadus morhua) in relation to temperature and oxygen level in the Gulf of St. Lawrence
Authors: D'AMOURS DENIS 
Published: October 2007

ABSTRACTBottom temperature and oxygen level were measured in the northern Gulf of St. Lawrence during a ground‐fish trawl survey held in August and September 1991. Cumulative relative frequencies of temperature and oxygen level and cumulative relative frequencies of temperature x cod and oxygen X cod were computed with consideration of the random stratified sampling scheme. A total of 84‐3% of temperature x cod frequency cumulated from 2oC to 4oC, but only 25% of the frequency of temperature alone cumulated from 2oC to 4oC. At an oxygen level of 3.4 mg/1, only 2.6% of the oxygen X cod frequency had cumulated, while 24.3% of the cumulative frequency of oxygen alone was already observed at the same oxygen level. A comparison of the cumulative relative frequencies of temperature and of temperature X cod indicates that cod choose intermediate temperatures in the available range. A comparison of the cumulative relative frequencies of oxygen and of oxygen x cod indicate that cod avoid water with an oxygen level below 3.4 mg/1. This oxygen level is known to cause physiological stress in captivity. Data from the stations with oxygen levels ± 3.4 mg/1 were ignored, and the cumulative relative frequency of temperature was recomputed. As a result, the avoidance of cold water by cod was emphasized: 23% of the cumulative frequency of temperature alone was below 2oC, and 47.8% was above 4oC, in contrast to 17.2% and 57.5%, respectively, prior to removal of data from hypoxic stations.
Predation on walleye pollock (Theragra chakograrnma) eggs and yolk‐sac larvae by pelagic crustacean invertebrates in the western Gulf of Alaska
Authors: BAILEY KEVIN M. , BRODEUR RICHARD D. , MERATI NAZILA , YOKLAVICH AND MARY M. 
Published: October 2007

ABSTRACTImmunological detection of yolk protein was used to assess predation by pelagic amphipods (gammarid and hyperiid), mysids, and euphausiids on eggs and yolk‐sac larvae of walleye pollock Theragra chalcogramma during 1988 and 1989. Consumption estimates were made on the basis of frequency of positive immunoassays, assay detection times (gut clearance time), predator abundance, and spatial overlap of predators and prey. From our results gammarid amphipods and euphausiids were important predators on eggs and yolk‐sac larvae, respectively. Gammarid amphipods alone consumed about 14% of the standing stock of pollock eggs in 1989. These results were compared with those from clearance rate experiments of predators feeding on pollock eggs in 300‐1 bags. In general, clearance rate estimates of egg consumption were lower than those determined from gut contents.
Cod spawning in relation to physical and biological cycles of the northern North–west Atlantic
Authors: MYERS R. A. , MERTZ G. , BISHOP C. A. 
Published: October 2007

ABSTRACTAll the available, reliable cod (Gadus morhua) spawning data for the northern North–west Atlantic (the Grand Banks of Newfoundland, the Labrador and West and East Greenland Shelves) have been analysed to update older, often unpublished, reports of spawning dates. The derived spawning times are examined for latitudinal trends and it is shown that no consistent, general pattern exists. The spawning dates are compared with seasonal cycles of plankton abundance, ocean temperature, water column stability and oceanic transport. The latitudinal trends in spawning dates and timing of the plankton peak are found not to correspond.
The use of satellite imagery to direct research ship sampling operations
Authors: BROWN R. M. , DENMAN K. L. , BORSTAD G. A. , PARKS J. R. 
Published: October 2007

ABSTRACTOceanographic processes on the continental shelf adjacent to Vancouver Island are energetic, highly variable and dominated by eddies, upwelling jets and shelfbreak baroclinic instabilities. Consequently, areas of enhanced planktonic production are patchy and ever‐changing, making them difficult to study and map from ship. We have developed a technique for transmitting interpreted thermal AVHRR satellite imagery to research ships, where we use the imagery to direct CTD sampling lines, acoustic Doppler current profiling and deployment of drifting buoys. The AVHRR satellite images are geo‐referenced, masked and interpreted to produce a contoured sea surface temperature field in the area of interest. The contour field image is transferred between personal computers equipped with matching facsimile subsystems. The compressed image is transmitted via HF radio link or Inmarsat. The preprocessing of the image ashore provides for significant data compression and allows for operational use of the image to direct research of fishing within 12 h of the satellite pass.
The North Atlantic turbine: views of production processes from a mainly North Atlantic perspective
Authors: WYATT T. , JENKINSON I. R. 
Published: October 2007

ABSTRACTA brief account is given of the ‘agricultural hypothesis’, the key studies which led to its replacement by the ‘grazing hypothesis’, and early models of the classical planktonic food chain. The budgetary problems posed by these views led to interest in the roles of dissolved and particulate components of planktonic ecosystems, and to discovery of the ‘microbial loop’. The balance between these alternative pathways is seen to reflect processes at the interface between hydrodynamics and ecology.