bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical analyses of intra‐ and interspecific density effects on recruitment of chub mackerel and sardine in Japan
Authors: KISHIDA TATSU , MATSUDA HIROYUKI 
Published: October 2007

ABSTRACTDensity effects of chub mackerel, Scomber japonicus, and sardines, Sardinops melanosticta, on the recruitment strength of each species were examined by multiple regression analyses of year‐class strengths and stock abundances or catch statistics compiled over nearly 30 y. The two species have become successively dominant in the pelagic fish assemblage in Japanese waters during the last few decades. Results suggested that both sardines and chub mackerel played suppressive roles on sardine recruitment (P < 0.01), and it seemed that such inhibition was brought about mainly by the dominant species of the two. A direct density effect on chub mackerel recruitment by either species was not clear, but analyses indicated that both species produced delayed density effects on chub mackerel year‐class strengths (P < 0.01). Year‐class strengths of chub mackerel were highly dependent upon annual egg production, which in turn was apparently affected by the stock abundance of the two species over the previous 2 or 3 y. Delayed intraspecific density effects on egg production seemed to operate strongly until the late 1970s. After the sardine stock increased significantly (i.e. 1980s), however, the per capita annual egg production of chub mackerel did not recover in spite of a decrease in the stock size, possibly owing to the delayed density effects of the sardine stock.
The ecological impact of the Great Salinity Anomaly in the northern North‐west Atlantic
Authors: MERTZ G. , MYERS R. A. 
Published: October 2007

ABSTRACTIn a number of recent papers Cushing has advocated that the Great Salinity Anomaly (GSA), which entered the northern North Atlantic in the early 1970s, adversely affected the recruitment of a number of deep‐water fish stocks of this ocean. Cushing envisages that a temperature anomaly accompanying the GSA slowed and/or delayed growth in the spring phytoplankton bloom which sequentially affected zooplankton growth and fish recruitment. We test a number of hypotheses relating to Cushing's picture, focusing on the waters of the West Greenland, Labrador and Newfoundland Shelves. We find that, south of Greenland waters, there were no significant temperature anomalies corresponding to the GSA. In addition we show that stability of the shelf waters increased during the GSA, casting doubt on the contention that the phytoplankton bloom was delayed by retardation of the spring stabilization of the water column due to the influence of cold water. Our analysis indicates that the food chain coupling of environment to recruitment (climate to phytoplankton to zooplankton to fish) is not strong in the study region.
Physical and biological consequences of a climate event in the central North Pacific
Authors: POLOVINA JEFFREY J. , MITCHUM GARY T. , GRAHAM NICK E. , CRAIG MITCHELL P. , DEMARTINI EDWARD E. , FLINT ELIZABETH N. 
Published: October 2007

ABSTRACTClimatic changes over the North Pacific which began in the mid 1970s, peaked in the early 1980s, and ended by the late 1980s, appear to have altered productivity at various trophic levels in the marine ecosystem in the central North Pacific. The climatic change resulted in increased mixed layer depth and the frequency of deep mixing events, particularly during January‐March. A number of biological time series for species ranging from primary to apex levels in the North‐western Hawaiian Islands, show corresponding declines in productivity of 30–50% from the early 1980s to the present. We hypothesize that during the early 1980s, increased mixing due to the climate event resulted in greater nutrient input into the euphotic zone and ultimately increased ecosystem productivity. Productivity over a range of trophic levels declined when the climate event ended.
Interannual variability in coastal Washington Dungeness crab (Cancer magister) populations: larval advection and the coastal landing strip
Authors: McCONNAUGHEY ROBERT A. , ARMSTRONG DAVID A. , HICKEY BARBARA M. , GUNDERSON DONALD R. 
Published: October 2007

ABSTRACTSubstantial and unexplained variations in abundance characterize US west coast populations of Dungeness crab,Cancer magister.It is likely that this variability reflects oceanic advection of larvae given the dynamics of the California Current system, the protracted (4–5 months) pelagic larval phase and the restrictive nature of juvenile habitat requirements. We compare 40 years of Ekman transport vectors during January‐May (1947– 1986) with time‐lagged and stratified commercial landings for coastal Washington (1951–1990). Persistent landward and net northward flow characterized the circulation of near‐surface waters during the larval periods studied. A mechanism for progressive seaward transport of larvae through ontogeny, as proposed by others, was not apparent. Overall, above‐ (below‐) average year classes were associated with relatively weak (strong) northward transport and, to a lesser degree, strong (weak) landward transport. Based on these analyses and in consideration of the prevailing coastal circulation, we propose that the relative magnitude of C.magisterjuvenile recruitment and, hence, incoming year class strength, reflects: (1) the proportion of larvae retained within a relatively narrow (≤ 15 km) and heterogeneous ‘coastal landing strip’, (2) the availability of suitable substrate within the coastal landing strip at time of settlement and (3) the magnitude of downstream advective losses (export) of larvae from the California‐Oregon‐Washington coastal system. Based on a consideration of the physics of the California Current system and the larval biology of the species, significant linkage of Dungeness crab populations along the west coast of North America is likely.
Modelling the transport of particles in the North Sea with reference to sandeel larvae
Authors: BERNTSEN JARLE , SKAGEN DANKERT W. , SVENDSEN EINAR 
Published: October 2007

ABSTRACTThe transport of particles representing sandeel larvae in the North Sea is simulated with a three‐dimensional circulation model for the years 1976 to 1990. A great year‐to‐year variability in drift patterns is demonstrated. The results may explain some of the observed differences in recruitment between the main sandeel areas in the North Sea. In the northern sandeel area it seems that strong year classes are unlikely if the retention due to unfavourable currents is poor, and that a high retention in the summer may favour a good year class. In the southern sandeel area no clear coupling between year class strength and larval drift is found, possibly because the retention always seems large enough for a potentially good year class. For more quantitative use of such models in relation to sandeel recruitment, more biological knowledge is obviously needed on larval vertical distribution and timing of sandeel hatching and settling.
Transport of larvae and juvenile fish into central and northern Norwegian waters
Authors: BJØRKE HERMAN , SAETRE ROALD 
Published: October 2007

ABSTRACTThe distribution of juvenile fish in Norwegian waters in spring and summer provides evidence that some of these are transported into Norwegian coastal waters from spawning grounds outside the ecosystems which comprise the central and northern Norwegian coast, the Barents Sea and the Spitsbergen area. The relevant species are capelin (Mallotus villosus Müller), haddock (Melanogrammus aeglefinus L.), herring (Clupea hareri' gus L.) and saithe (Pollachius virens L.). A substantial part of the saithe and haddock stock along the central and northern Norwegian coast is considered to be recruited from spawning grounds in the northern North Sea. A contribution of these species from the spawning grounds around the Faeroe Islands and west of Scotland may also occur in some years. Herring from the northern North Sea are found scattered off the Norwegian coast north to 70oN. It seems likely that pelagic species such as capelin and herring are transported by the prevailing currents from Iceland.
Distribution and reproduction of the planktonic copepod, Calanus pacificus, off southern California during winter‐spring of 1992, relative to 1989–91
Authors: MULLIN MICHAEL M. 
Published: October 2007

ABSTRACTAbundance and production of eggs by female Calanus pacificus off southern California were assessed in February and April, 1992, together with biomass of chlorophyll and abundance of larval anchovy. Because 1992 was an anomalous year as a result of a Californian El Nino, the patterns were compared with analogous data for 1989‐91. Female Calanus were much less abundant in both February and April of 1992 than in the earlier years, and the anomalies were negatively related to temperature anomalies, but the biomass of chlorophyll and per capita egg production were anomalously low only in February. The horizontal distribution of female Caianus was similar to that of chlorophyll in winter, but was more efficient (in the sense of permitting more complete utilization of the available chlorophyll) in April, 1992, than in the earlier springs. The abundances of larval anchovy were positively correlated with the reproduction of the Calanus population in 1992 and in the earlier years, but the larvae were poorly distributed with respect to Calanus spawning, in both 1992 and the earlier years, to take best advantage of the resulting nauplii as food.
On the relationship between the Oyashio front and saury fishing grounds in the north‐western Pacific: a forecasting method for fishing ground locations
Authors: YASUDA ICHIRO , WATANABE YOSHIRO 
Published: October 2007

ABSTRACTThe relationships between fishing ground locations of Pacific saury (Cololabis saira) and the two Oyashio fronts, the offshore front between 146oE and 155oE and the coastal Oyashio intrusion, before the saury fishing season, were examined using data from 1971 to 1991. Interannual geographical shifts of both the offshore Oyashio front and saury fishing grounds had a dominant interdecadal fluctuation. In years when the offshore front shifted north (south), the fishing grounds were formed relatively nearshore (offshore). When the offshore front shifted north, the fishing grounds were formed further nearshore in years the coastal Oyashio intrusion extended south. When the offshore front shifted south, on the other hand, the southward extension of the coastal intrusion did not necessarily cause formation of coastal fishing grounds. These results showed that locations of the fishing grounds depend not only on local and instantaneous oceanographic environments around the fishing grounds, but also on oceanographic conditions over an extensive range of the Oyashio area. This might indicate that the ecology of the saury's northward migration, through mixed water regions between the Kuroshio and Oyashio fronts in spring and summer, has a close relation to the shift of the offshore Oyashio front over a time range of months. A practical forecasting method for locations of saury fishing grounds is proposed based on the oceanography before the fishing season.
Ubiquitous eddies of the eastern Bering Sea and their coincidence with concentrations of larval pollock
Authors: SCHUMACHER J. D. , STABENO P. J. 
Published: October 2007

ABSTRACTBetween 1988 and 1993, 12 satellite‐tracked buoys were deployed in four eddies in the south‐eastern Bering Sea. Our success in finding eddies resulted from placing buoys in high concentrations of walleye pollock (Them‐gra chalcogramma) larvae. We utilize data from hydro‐graphic surveys, satellite‐tracked buoys and moored current meters to describe the eddies. Small (< 25 km diameter) eddies likely transit along the slope of the eastern Bering Sea every 45–60 days. In previous studies such small features were not observed because their size fell within typical separation of hydrographic stations and the weak sea surface temperature gradients are not resolved by satellite‐borne infrared imagery.
Relationships between temperature and landing patterns in the southern Labrador and eastern Newfoundland inshore cod fishery
Authors: CHEN XIAO HONG , SHELTON PETER A. , BATH ALISTAIR J. 
Published: October 2007

ABSTRACTThe temporal pattern of cod landings in the inshore trap fishery off the east coast of Newfoundland and Labrador is examined in this study. Unlike previous studies which have been broad scale or of a localized nature, this analysis looks at variations within fishing seasons and among fishing areas in trap landings. A significant relationship between water temperature and the weekly pattern is demonstrated. Significant spatial patterns in weekly landings are described and related to longshore differences in the seasonal variation in temperature.
Decadal‐scale regime shifts in the large marine ecosystems of the North‐east Pacific: a case for historical science
Authors: FRANCIS ROBERT C. , HARE STEVEN R. 
Published: October 2007

ABSTRACTThere are two fundamental ways of doing science: the experimental‐predictive and the historical‐descriptive. The experimental‐predictive approach uses the techniques of controlled experiment, the reduction of natural complexity to a minimal set of general causes, and presupposes that all times can be treated alike and adequately simulated in the laboratory. The historical‐descriptive approach uses a mode of analysis which is rooted in the comparative and observational richness of our data, is holistic in its treatment of systems and events, and assumes that the final result being studied is unique, i.e. dependent or contingent upon everything that came before. We suggest that one of the real difficulties we have in understanding ecosystem properties is our inability to deal with scale, and we show how historical science allows us to approach the issue of scale through the interpretation of pattern in time and space. We then use the techniques of the historical‐descriptive approach to doing science in the context of our own and other research on climate change and biological production in the North‐east Pacific Ocean. In particular, we examine rapid decadal‐scale shifts in the abundance and distribution of two major components–salmon and zooplankton ‐ of the large marine ecosystem of the North‐east Pacific, and how they relate to similar shifts in North Pacific atmosphere and ocean climate. We conclude that they are all related, and that climate‐driven regime shifts, such as those we have identified in the North‐east Pacific, can cause major reorganizations of ecological relationships over vast oceanic regions.
Predicting the dispersion of sprat larvae (Sprattus sprattus (L.)) in the German Bight
Authors: BARTSCH JOACHIM , KNUST RAINER 
Published: October 2007

ABSTRACTSprat (Sprattus sprattus (L.)) larval dispersal in the German Bight is predicted with a model system consisting of two three‐dimensional circulation models and a three‐dimensional transport model. Horizontal distribution data for specific length classes of larvae, obtained from field surveys carried out in the German Bight during summer 1991, are used as initial conditions for the starting points of the tracers in the transport model. Sprat larval distributions are predicted and are compared with distributions of the appropriate length class of larvae observed during a subsequent cruise about 3 weeks later. The predicted larval (tracer) distributions compare favourably to observed larvae distributions in the inner model areas but not in the areas close to the coast. Factors contributing to inaccurate predictions are uncertainties in horizontal and vertical larval distributions as well as the model grid resolution, which is too coarse in coastal areas.
Effects of temperature, wind and spawning stock biomass on recruitment of Arcto‐Norwegian cod
Authors: OTTERSEN GEIR , SUNDBY SVEIN 
Published: October 2007

ABSTRACTSea temperature has earlier been shown to have a large influence on the recruitment of Arcto‐Norwegian cod, Gadus morhua. We here hypothesize that this linkage is partly due to the direct effect of temperature on larval and juvenile growth. Secondly, temperature acts as a proxy for both biotic and abiotic factors influencing recruitment. Indices of abundance of early juvenile cod (2–3 months old), 0‐group cod (4–5 months old) and 3‐year‐old cod are analysed in more detail against the environmental temperature, wind stress components, wind‐induced turbulent energy and the spawning stock biomass. To deal with autocorrelation, non‐stationar‐time and nun‐normality, which complicate a statistical time series analysis, randomization and Box‐Jenkins methods are applied. In addition to the important effect of high sea temperature during the early life stage in forming strong year classes, the results show that the spawning stock biomass is nearly as important. Also, alongshore southerly wind stress anomalies during the period of pelagic drift (from April through summer) and offshore wind stress anomalies during egg and early larval stages (in April) act favourably on recruitment. The beneficial effect of southerly wind anomalies could he linked partly to high temperature, but the flux of zooplankton‐rich water from the Norwegian Sea into the feeding areas of the Barents Sea may also be increased. The favourable influence of offshore winds in April is less predominant and causal links are also less clear; possible explanations for this might be increased offshore spreading of eggs and early larvae, resulting in reduced risk of predation, and increased compensation inflow of intermediate Norwegian Sea water which, in this restricted period of time, has a high concentration of spawning copepods suitable as prey for the developing cod larvae.
On the variable subsurface environment of fish stocks in the Bering Sea
Authors: REED R.K. 
Published: October 2007

ABSTRACTData from 1971 to 1993 are used to examine characteristics and variability of the subsurface temperature maximum in the Aleutian Basin of the Bering Sea. The temperature of this feature varies from ∼3.5g̀C to 4.6d̀C at depths of ∼150–400 m, and sigma‐t density is usually in the range 26.6–26.9. The variability is caused mainly by the absence or presence of inflow of warm, low‐density Alaskan Stream water through Amukta Pass. Thus the environment offish stocks is far from uniform.
It's about time: new beginnings and old good ideas in fisheries science
Authors: SHARP GARY D. 
Published: October 2007

ABSTRACTViews about aquatic resource management are changing, particulaly now that resource yields from world fisheries have been shown to be not only unsustainable, but steadily declining under conventional management practice. There is ample reason for re‐examination, and more pragmatic definitions of what is meant by sustainability There have nearly always been clear, reasonable means for making appropriate decisions that would have safeguarded most of the ocean's living resources, hut in general greed and lack of societal will, as articulated it national governmental levels, have promoted the present resource deterioration. I also posit that the underlying science in support of sustainable fisheries decision‐making has been responsible for a great proportion of this deterioration. Revitalization of fisheries science, indeed rehabilitating the affected fisheries, will he required to regain the losses in credibility of the agencies and of the underlying science. This will depend upon resumption of integrated environmental monitoring, more enlightened application of what is already known, and reconnection of the science to the several industries involved, i.e. fishing, processing and marketing. Management implemented at the market place may be one of the few remaining options to secure the sustainability of natural resources
A spatially explicit fitness‐based model of capelin migrations the Barents Sea
Authors: FIKSEN Ø. , GISKE J. , SLAGSTAD D. 
Published: October 2007

ABSTRACTThe geographical distribution and production of the Barents Sea capelin (Mallotus villosus, Osmeridae) is modelled by the use of a state‐variable optimization technique (dynamic programming), where the main objective of individuals always is to maximize fitness, or total expected reproduction (RO), by selecting the most profitable habitats through time. Fitness is gained by successful reproduction (a function of size) during the spawning season on the breeding grounds off northern Norway. The environment (predators, temperature and zooplankton prey) is determined by a meteorologically forced circulation model for the year 1980, creating a spatial and seasonal fluctuation in the environment. Predation from cod is the main source of mortality, and the distribution of the cod (Gadus morhua) stock is assumed to vary with temperature. Growth is predicted from a bioenergetic model, incorporating the cost of swimming between feeding areas and spawning grounds. Field data of the capelin stock recorded during autumn cruises from 1979 is implemented at the start of the model, and then this stock is modelled through 1980 and the first months of 1981. Model predictions are compared with the observed distribution of capelin in autumn 1980. Habitat selection has consequences for the dynamics of the population and growth of individuals, demonstrating the importance of combining external (environmental) and internal (evolutionary) forcing to understand and predict the dynamics of fish populations. This study is the first application of dynamic programming to model the dynamics and ecologyof horizontal fish migration, and we suggest that the method may be developed into a useful tool for the management of short‐lived species.
Computer simulations of homeward‐migrating Fraser River sockeye salmon: is compass orientation a sufficient direction‐finding mechanism in the north‐east Pacific Ocean?
Authors: DAT CLAIRE G. , LEBLOND PAUL H. , THOMSON KEITH A. , INGRAHAM W. JAMES 
Published: October 2007

ABSTRACTComputer simulations were used to investigate whether compass orientation is a sufficient guidance mechanism for sockeye salmon migrating to the Fraser River from their ocean foraging grounds in the north‐east Pacific Ocean. Daily surface ocean currents, simulated by the ocean surface current simulations (OSCURS) model, were used to test the influence of currents on the return oceanic migration of Fraser River sockeye salmon. High seas tagging and coastal recover data of Fraser River sockeye salmon were used for the migration simulations. Surface currents were shown to increase the speed of the homeward‐migrating sockeye salmon, as well as to deflect the fish in a north‐eastward direction. In spite of ocean currents, all Fraser River sockeye salmon were able to reach their destination with a fixed direction and bioenergetically efficient swimming speed when migration was delayed until the last month at sea. Compass orientation alone was shown to be a sufficient direction‐finding mechanism for Fraser River sockeye salmon.
Sinking rate of loricae of some common tintinnid ciliates
Authors: SUZUKI TOSHIKAZU , TANIGUCHI AKIRA 
Published: October 2007

ABSTRACTSinking rate of empty loricae of seven tintinnid species was measured in settling chambers. The sinking rates normalized for 3% NaCl solution at 20d̀C are 0.25‐2.08 m day‐1 for five hyaline loricae and 1.90 and 15.9 m day‐1 for two agglutinated loricae. Positive relationships between sinking rate and size of hyaline loricae such as volume, surface area and nominal diameter were established, which favour the practical estimation of sinking rate of empty loricae discarded by natural tintinnid populations by measuring size composition. The slower sinking rate of hyaline loricae, compared with that of diatoms, indicates their availability as indicators of particular water masses in the ocean. Loricae incorporated into faecal pellets of zooplankton and marine snow also indicate the origin of these sinking particles.