bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variations in food abundance for Japanese sardine larvae related to the Kuroshio meander
Authors: NAKATA KAORU , HADA AKIO , MATSUKAWA YASUO 
Published: October 2007

ABSTRACTLong‐term fluctuations of chlorophyll a concentration, and abundance of herbivorous or omnivorous small copepods during the spawning season of the Japanese sardine, Sardinops melanosticta, were examined in relation to the types of Kuroshio meander. The purpose was to clarify the influence of the meander on the production of food organisms for the sardine larvae and their survival in the Pacific coastal region of central Japan. During an A‐type meander of the Kuroshio, when the offshore and inshore movements of the Kuroshio path were small except at the beginning of the meander, the surface chlorophyll a concentration in the coastal region was lower than that during a non‐A‐type meander with frequent and prompt fluctuations of the Kuroshio path. The abundance of small copepods was also low during the A‐type meander except in the subsequent spring just after the beginning of an A‐type meander, but often high during the non‐A‐type meander. Prompt fluctuations of the Kuroshio path during the non‐A‐type meander probably cause local upwellings which stimulate primary and secondary production near the Kuroshio, and may enhance the survival of the sardine larvae. On the contrary, the quasi‐stationary state of an A‐type meander may be unfavourable for the production of phytoplankton and nauplii of herbivorous or omnivorous small copepods, and therefore the survival of the sardine larvae becomes poor.
Comparative analysis of ichthyoplankton sampling gear for early life stages of walleye pollock (Theragra chalcogramma)
Authors: SHIMA MICHIYO , BAILEY KEVIN M. 
Published: October 2007

ABSTRACTComparative gear tows were conducted during the summers of 1987–1990 in the Gulf of Alaska. Efficiencies of four types of ichthyoplankton sampling gear were compared with respect to total catch and size distribution of larval fish. Fish were sampled using the bongo net (333 and 505 μm mesh), 1 m Tucker net, 3 m Tucker net and the Methot frame net. Results indicate that the bongo and the 1 m Tucker nets caught similar numbers and size distribution of fish. The larger 3 m Tucker and Method frame nets caught a larger size class of fish but a smaller total catch. Although there was a slightly significant diel difference in total catch detected in the smaller nets, no diel differences in size distribution of fish caught were detected for any of the nets.
Fishery development in the eastern North Pacific: a natural‐cultural system perspective, 1888–1976
Authors: DEIMLING ELISABETH A. , LISS WILLIAM J. 
Published: October 2007

ABSTRACTCommercial fishery landings data spanning almost a century were examined from three regions within the eastern North Pacific: north‐central California, Oregon‐Washington, and Southeast Alaska. Fisheries in each region developed differently because each region had unique species, community trophic composition, and other community parameters related to differences in physico‐chemical characteristics. Fisheries also began at different times in each region. Despite differences, overall patterns of landings were similar among regions. A ‘fishing‐up’ sequence occurred in each region that included seaward expansion of the fishery and diversification of taxonomic composition of landings. Mean annual landed weights of several very desirable taxa fished continuously from the early years of the fisheries initially increased, peaked, then declined. These patterns are similar to those found in studies of long‐term fishery development in the Great Lakes. Other patterns of landings over time common to each region were: exclusions of particular taxa in more recent time periods; predominance of pelagic species; and shifts in trophic composition away from predominance of taxa at high trophic levels. In two regions there were initial increases, then declines in mean annual weights of total landings. Similarities in these patterns among regions that differ greatly in terms of physico‐chemical characteristics suggest the overwhelming importance of common cultural parameters. Management suggestions are made based on the common patterns of commercial fishery development.
Simulating the dispersion of vertically migrating sprat larvae (Sprattus sprattus (L.)) in the German Bight with a circulation and transport model system
Authors: BARTSCH JOACHIM , KNUST RAINER 
Published: October 2007

ABSTRACTA model system consisting of two three‐dimensional circulation models and a three‐dimensional transport model is used to simulate the dispersal of sprat larvae (Sprattus sprattus (L.)) in the German Bight. A Northwest European shelf sea model simulates the currents of the North Sea and provides sea surface elevation data for the open boundaries of the German Bight circulation model. The German Bight circulation model has a horizontal grid resolution of 2.75 km and a vertical resolution of 5 m except for the bottom layer. The driving forces of the circulation models are the M2‐tide, six‐hourly time‐dependent wind stress and air pressure fields as well as monthly climatological density fields. The simulated currents serve as input to the transport model. The model area, grid size and the vertical resolution of the transport model are in accordance with the German Bight circulation model. The transport model simulates advection and diffusion using a Monte Carlo method. Furthermore it incorporates a simulation of active vertical movement of the larvae. The vertical migration pattern is dependent on the time of day and size of the larvae and is based on field data from the German Bight. Horizontal larvae distribution data, gained from two out of five field surveys carried out in the German Bight during spring and summer 1991, are used as initial values for the starting points of the tracers in the transport model. Simulated tracer distributions are compared with larval distributions observed during subsequent cruises about 3 weeks later. Discrepancies and similarities between tracer and larval distributions are discussed.
Eulerian views of layered water currents, vertical distribution of some larval fishes, and inferred advective transport over the continental shelf off North Carolina, USA, in winter
Authors: GOVONI JOHN J. , PIETRAFESA LEONARD J. 
Published: October 2007

ABSTRACTCurrents that effect the shoreward transport of the larvae of estuarine‐dependent fishes spawned in winter in Onslow Bay, North Carolina, USA, were driven by winds and pressure gradients, and influenced by the Gulf Stream. Aside from storms, winds over the continental shelf in Onslow Bay blew predominantly alongshore with velocities approaching 14 m s‐1 during February and March 1986, and January and February 1989. Water masses and currents observed at two current‐meter moorings, one at mid‐shelf and the other on the outer shelf, reflected the onshore (or offshore) advection of interior water in compensation for the offshore (or onshore) advection of wind‐driven surface water. Winds and currents reversed direction approximately every 4 to 6 days. The larvae of Atlantic menhaden, Brevoortia tyrannus, spot, Leiostomus xan‐thurus, and Atlantic croaker, Micropogonias undulatus, were most abundant in 17–19oC and 20–21oC water of the outer shelf and Gulf Stream fronts. There was little indication of diel vertical migration; larval Atlantic menhaden were most abundant in mid‐ and surface water, while spot and Atlantic croaker were most abundant in mid‐ and deep water. Given this distribution, the inferred advective transport of larvae was at times onshore, but at other times it was offshore. Within a spawning season, the prevalence of either reciprocation could determine the number of larvae that reach coastal inlets.
Relationships among yellowfin and skipjack tuna, their prey‐fish and plankton in the tropical western Indian Ocean
Authors: ROGER CLAUDE 
Published: October 2007

ABSTRACTStomach contents of yellowfin (Thunnus albacares) and skipjack (Katsuwonus pelamis) tuna caught by trolling and purse seining in the tropical western Indian Ocean, together with those of the prey‐fish found in their stomachs, have been analysed. Epipelagic fish are the main prey of these tunas, whereas no vertically migrating fish, which inhabit subsurface layers at night, have been found in their stomachs. These tunas are thus considered day‐feeders. Purse‐seine‐caught tunas, which belong to large schools, have a much higher number of prey‐fish in their stomachs than tunas caught by trolling on small schools. Similarly, prey‐fish from purse‐seine tunas have a much higher number of plank‐tonic prey in their stomachs than those from troll‐caught tunas. Therefore, these tunas adopt a wandering strategy in small schools when food resources are scarce and form large schools when they are abundant. The planktonic organisms found in the stomachs of prey‐fish are described by taxa and sizes; they represent the fraction of the planktonic biomass actually supporting the stock of tuna. Size ratios between the three links tuna‐prey‐fish‐plankton are very high, suggesting that these tunas benefit from a short food chain which is probably efficient from the energetic point of view.
The influence of ocean climate on coastal plankton and fish production
Authors: ROBINSON CLIFFORD L. K. 
Published: October 2007

ABSTRACTThis study evaluates the influence of oceanic variability on plankton and fish production in a coastal upwelling system off southern Vancouver Island, British Columbia, Canada. A trophodynamics model is used to hind‐cast plankton and fish production as estimated by empirical seasonal patterns in upwelling, sea surface temperature, solar radiation, and by biomasses of Pacific hake (Merluccius productus) and Pacific herring (Clupea pallasi). Simulation results indicate that interannual and longer‐term variability in coastal plankton production occurs, and that the patterns are primarily determined by the dynamics in the initiation and intensity of coastal upwelling. Fish properties are greatly influenced by zooplankton, with simulated hake production being correlated with summer euphausiid production, and measured herring condition being correlated with autumn zooplankton production. An evaluation of transfer efficiencies indicates that interannual variability in the diatom‐to‐fish transfer is high (CV = 78%), with the majority of this variability occurring in the diatom‐to‐zooplankton component of the transfer. Seasonal dynamics of the diatom‐to‐zooplankton transfer result from the effects of upwelling on diatom production, and subsequent trophodynamic phasing with copepods and euphausiids.
Is there a role of ocean environment in American and European eel decline?
Authors: CASTONGUAY MARTIN , HODSON PETER V. , MORIARTY CHRISTOPHER , DRINKWATER KENNETH F. , JESSOP BRIAN M. 
Published: October 2007

ABSTRACTAmerican eel (Anguilla rostrata) recruitment has declined dramatically, in parallel with that of European eel (Anguilla anguilla). Since both species spawn in the Sargasso Sea and migrate as larvae to continental waters, the coincidence in recruitment failure implies an Atlantic‐wide cause, due perhaps to ocean climate. There is indirect evidence that the Gulf Stream has weakened in the 1980s. A slower Gulf Stream could interfere with larval transport and generate observed patterns of declining abundance of American eel only in northern North America and relatively uniform declines of European eel throughout Europe. While specific causes are still unclear, these data indicate a threat to both species and to their commercial fisheries.
A review of temperature and oxygen tolerance studies of tunas pertinent to fisheries oceanography, movement models and stock assessments
Authors: BRILL RICHARD W. 
Published: October 2007

ABSTRACTDetailed data on the physiological abilities and habitat requirements of some tuna species have now been collected. Laboratory and field studies show tunas are not strictly prisoners of their own thermoconserving mechanisms, but have rapid and extensive control over the efficacy of their vascular countercurrent heat exchangers. Skipjack tuna (Katsuwonus pelamis) are, therefore, probably not forced out of formerly suitable habitats as they grow because of the potential for overheating, as formerly thought. Because of their thermoregulatory abilities, bigeye tuna (Thunnus obe‐sus) apparently can exploit food resources well below the thermocline by minimizing rates of heat loss when in cold water, and then maximizing rates of heat gain from the environment during brief upward excursions into the warmer mixed layer.Widely cited estimates of limiting oxygen levels, based on estimated metabolic rates at minimum hydrostatic equilibrium swimming speeds, are not accurate because tunas have exceptionally high oxygen demands even at slow speeds. High metabolic rates, even at slow swimming speeds, most likely result from the high osmoregulatory costs engendered by tunas' large thin gills and/or their other adaptations for achieving exceptionally high maximum metabolic rates. Recent laboratory research and modelling efforts suggest the capacity of tunas' cardiorespiratory systems to deliver oxygen at extraordinarily high rates was evolved to allow rapid recovery from strenuous exercise, rapid digestion, and high rates of gonadal and somatic growth, not high sustained cruising speeds. The rate at which reduced ambient oxygen levels prolong the time required for tunas to recover from strenuous exercise appears to be a good index of habitat suitability, with respect to oxy‐een.
Simulation of juvenile sockeye salmon (Oncorhynchus nerka) migrations in the Strait of Georgia, British Columbia
Authors: PETERMAN RANDALL M. , MARINONE SILVIO G. , THOMSON KEITH A. , JARDINE IAN D. , CRITTENDEN ROBERT N. , LEBLOND PAUL H. , WALTERS CARL J. 
Published: October 2007

ABSTRACTPrevious research has documented two main migratory routes of juvenile sockeye salmon (Oncorhynchus nerka) through the Strait of Georgia, British Columbia, Canada, and large interannual variability in marine survival rates of the Chilko Lake stock. Simulation models were used to explore the influence of surface currents on the migratory route of juvenile sockeye salmon (smolts) through the Strait of Georgia. We used a model of downstream migration to generate daily numbers of Chilko Lake sockeye salmon smolts entering the Strait of Georgia, based on daily counts of smolts leaving the rearing lake. A numerical hydrodynamic model (driven by surface wind, tide, and Fraser River discharge) hindcasted surface currents in the Strait of Georgia on a 2 km × 2 km grid. A smolt migration model simulated fish moving through the Strait with different compass‐oriented migratory behaviours (i.e. swimming speed and directional orientation) within the time‐varying surface advection field. Results showed that surface currents within the Strait of Georgia can affect the migratory route of sockeye salmon smolts in spite of their large size (8 cm). Wind is the forcing mechanism primarily responsible for determining which migratory route would be used. Under prevailing wind conditions (i.e. toward the north‐west), most sockeye salmon smolts would use the eastern migratory route; however, relatively brief south‐eastward wind events (lasting about 2 days) would force most smolts into the western migratory route. Given the heterogeneity of food for salmon within the Strait, we hypothesize that wind‐driven variability in the annual proportion of smolts that use the western and eastern migratory routes in the Strait of Georgia affects early marine survival rates of Fraser River sockeye salmon.
Match/mismatch predictions of spawning duration versus recruitment variability
Authors: MERTZ G. , MYERS R. A. 
Published: October 2007

ABSTRACTAccording to the match/mismatch hypothesis, larval fish survival and eventual recruitment is dependent on the offset time between the peaks of abundance of larvae and their planktonic prey. A rudimentary larval food supply model is developed to determine the dependence of food availability on the mismatch between peaks. The model predicts that recruitment variability should increase as spawning duration decreases, a result which is moderately supported by an analysis of Atlantic cod (Gadus morhua) data.
Recruitment variability and oceanographic stability
Authors: MYERS RANSOM A. , PEPIN PIERRE 
Published: October 2007

ABSTRACTWe examine the hypothesis that recruitment is more variable in populations on isolated offshore banks than nearby shelf populations. Recruitment of cod (Gadus morhua) and American plaice (Hippoghssoides plates‐soides) on Flemish Cap is more variable than in any comparable population. Recruitment of haddock (Melanogrammus aeglefinus) on Rockall Bank is also more variable than in surrounding populations. These results are confirmed both by estimates obtained by virtual population analysis and by research surveys. Recruitment of haddock and herring (Clupea harengus) on Georges Bank is also more variable than in surrounding populations; however, the results for two other groundfish populations, cod and yellowtake flounder (Limanda ferruginae), on Georges Bank are ambiguous. We conclude that marine fish populations on isolated banks are more variable than those on nearby shelf regions.
Influence of a Sargassum forest on the spatial distribution of water flow
Authors: KOMATSU TERUHISA , MURAKAMI SHIN‐ICHI 
Published: October 2007

ABSTRACTThe influence of a Sargassum forest on the spatial distribution of water flow generated by waves and tidal currents was investigated. Water flow was measured horizontally and vertically by using plaster balls at a Sargassum forest in Saiki Bay facing the Bungo Channel, on the Pacific Coast of Kyushu Island, Japan, from 7 to 9 March 1989 during the luxuriant growth season of Sargassum species. Plaster balls were deployed at several depths at stations placed with horizontal scales of 10–100 m. Wet weight loss of plaster balls immersed in the field for 50 h was converted to the speed of steady flow (named intensity of water motion) that brought the equivalent loss in a tank experiment. The results clarified that the spatial distribution of water flow showed good correlation with that of the standing crop of Sargassum forest, and that the intensity of water motion was appreciably diminished in the Sargassum forest. We also discuss ecological implications of the reduction in water flow within the Sargassum forest for the growth and settlement of Sargassum species.
Plankton abundance and size structure in the northern North Pacific Ocean in early summer
Authors: ODATE TSUNEO 
Published: October 2007

ABSTRACTPhyto‐ and zooplankton abundance and size structure were investigated in the northern North Pacific Ocean (37.0–49.5oN along 180o longitude) during June of 1987. The area between 41.5oN and 47.5oN was expected to be abundant in phytoplankton since both water column stability and nutrient availability were favourable for phytoplankton growth. Actual phytoplankton abundance was, however, low between 41.5oN and 45.5oN. In particular, abundance of net phytoplankton (>10μm) was low although picophytoplankton (<2 μm) was abundant between 41.5oN and 43.5oN. The zooplankton community between 41.5oN and 45.5oN was characterized by a large amount of net zooplankton and a small amount of microzooplankton. This situation may be best explained by top‐down control; that is, net zooplankton grazing suppressed net phytoplankton and microzooplankton abundance. The diminished microzooplankton promoted the increase of picophytoplankton. Because planktivorous Pacific saury were abundant between 40.0oN and 41.0oN, it is further speculated that the low biomass of net zooplankton south of 41.0oN resulted from feeding by Pacific saury. The reduced grazing pressure of net zooplankton may have enhanced the growth of net phytoplankton and microzooplankton in this region.
A structured approach to using biological and environmental parameters to forecast anchovy recruitment
Authors: COCHRANE K. L. , HUTCHINGS L. 
Published: October 2007

Simulation studies have indicated that a valuable increase in mean annual yield could be achieved in the South African anchovy, Engraulis capensis, fishery if below‐average recruitment could be forecast at the start of the fishing season, 6 months before recruitment can he reliably measured. This paper reports on initial investigations into biological and environmental indicator‐ which could be used to make such forecasts. Valid estimates of recruitment strength in the species are available from 1985 to 1992 and the environmental and biological indicators of interest have been monitored for periods starting from between 1984 and 1988, to the present. Most of the data were obtained from monitoring on anchovy spawner biomass surveys which have been undertaken each November since 1984.A conceptual model of the factors influencing the recruitment process was constructed and the available data were examined for empirical evidence of the importance of each event included in the model. Fluctuations in copepod biomass and production on the spawning grounds, the incidence of oocyte atresia in adult females, the incidence of southerly winds at Cape Point and the distance offshore of the 16°C isotherm at Cape Columbine were associated with fluctuations in anchovy recruitment. It is suggested that particular attention should be paid to monitoring of these variables to investigate further these associations. If persistent relationships are found, it may be possible to construct an expert system to forecast recruitment from observed values of these variables at the start of a fishing season. A preliminary set of three decision rules is presented.
A century and a half of change in the climate of the NE Pacific
Authors: WARE D.M. 
Published: October 2007

ABSTRACTSpectral analysis of twenty‐one climate records indicates that NE Pacific temperatures and winter wind stress have fluctuated at four dominant time scales in this century: 2–3 years (quasi‐biennial oscillation), 5–7 years (El Ni&#x006e;̈o‐Southern Oscillation, ENSO), 20–25 years (bidecadal oscillation, BDO), and a poorly resolved, very‐low‐frequency (VLF) oscillation with a 50–75 year period. Forty‐four per cent of the low‐frequency variability in British Columbia air temperatures is associated with the strength of the Aleutian Low pressure system in winter. Only 42% of the ‘strong’ and 25% of the ‘moderate’ ENSO events in this century have produced large warm anomalies off BC. Interactions between the ENSO, bidecadal and very‐low‐frequency oscillations produce a pattern of alternating warm and cool climate states, with major warnings every 50 to 75 years. Since 1850 there have been seven warm periods, lasting an average of 11.4 years, and six cool periods lasting an average of 10.8 years. Sharp transitions from cool to warm climate states (as in 1977/78) occur when warming phases of the BDO and VLF oscillations coincide. Recent evidence suggests that the BDO may originate in either the tropical or the subtropical North Pacific. The NE Pacific has experienced a major warming since 1978. A long‐range forecast suggests that the BDO and VLF oscillations peaked in 1989 and are currently in a cooling phase. Consequently, coastal temperatures should moderate for the rest of this century. A transition to the next cool climate state could occur about the year 2001. The forecast for moderating temperatures could begin the first phase of the recovery of the southern BC coastal chinook and coho salmon and herring stocks, which are currently at low abundance levels.