bluuebunny/crossref_metadata_2025_split huggingface dataset:
Remote sensing and geographical information systems: Their past, present and future use in global marine fisheries
Authors: SIMPSON JAMES J. 
Published: October 2007

ABSTRACTHistorically, the fishing community (e.g., fishermen, resource managers) has used remotely sensed products either in the form of direct Automatic Picture Transmission (APT) reception on a ship or FAX charts transmitted from land‐based stations. Both these products have severe limitations within the context of near real‐time support/management of an operational fishery. Moreover, relatively little use of geographical information systems (GIS) technologies has been made by either the fishing industry, fishery resource managers, or by the general oceanographic community. This latter omission is unfortunate because GIS has the potential to overcome two long‐standing problems associated with satellite‐directed fisheries: 1) the absence of information due to clouds; and 2) the general lack of support for nonpelagic fisheries. This report gives the background, motivation, and essential design elements for use of a combined remote sensing/geographical information system (RS/GIS) in an operational fishery and illustrates how a combined RS/GIS approach can be used to mitigate some of the traditional limitations in satellite‐directed fisheries. Finally, an attempt is made to provide some possible directions this new technology may take during the 1990s.
The effect of environment on puerulus settlement of the western rock lobster (PanuUrus cygnus) in Western Australia
Authors: CAPUTI NICOLAVITO , BROWN RHYS S. 
Published: October 2007

ABSTRACTThe level of puerulus settlement has proven to be a reliable predictor of the recruitment to the western rock lobster (Panulirus cygnus) fishery three and four years later. It is generally accepted that the early larval stages are moved offshore by wind‐driven surface currents. Previous studies have shown that coastal sea level, used as an indicator of the strength of the Leeuwin Current flowing down the west coast of Australia, was positively related to the level of puerulus settling on the inshore reefs after a 9‐ to 11‐month larval life. In this paper a significant relationship is also demonstrated between winter/spring storms, which are usually associated with onshore westerly winds, and the level of puerulus settlement (multiple correlation of 0.83, R1= 0.68, n = 22). Rainfall from coastal localities was used as an index of the storms. The residuals from this relationship showed a significant positive autocorrelation. The autocorrelation was incorporated into the relationship by using time series analysis with a transfer function model and a first‐order autocorrelation (R2= 0.76).The possible relationship between storms and the Leeuwin Current and their effect on the puerulus settlement are considered, and the potential for the environmental variables to bias or obscure the spawning stock recruitment relationship is discussed.
Influences of mean advection and simple behavior on the distribution of cod and haddock early life stages on Georges Bank
Authors: WERNER FRANCISCO E. , PAGE FRED H. , LYNCH DANIEL R. , LODER JOHN W. , LOUGH R. GREGORY , PERRY R. IAN , GREENBERG DAVID A. , SINCLAIR MICHAEL M. 
Published: October 2007

ABSTRACTResults of a modeling study designed to explore the influences of physical advection and certain biological mechanisms on the distribution of cod (Gadus morhua) and haddock (Melarwgrammus aeglefinus) early life stages on Georges Bank are described. Using a late‐winter/early‐spring 3‐D circulation field driven by the M2 tidal current, mean wind stress and Scotian Shelf inflow, we examine the distribution of cod and haddock larvae spawned on the Northeast Peak of the Bank. The sensitivity to a March‐April baroclinic field is also explored. Results indicate that larvae remaining in the surface Ekman layer are generally advected off‐bank. However, downwelling associated with Ekman layer convergence near the shelf break provides a mechanism for larvae to exit from the off‐bank surface drift. Larvae below the surface layer are transported south‐westward along the southern flank of Georges Bank and are retained on the Bank if their position immediately upstream of the Great South Channel is shoalward of (roughly) the 70 m isobath. Within the Great South Channel region and between the 50 and 70 m isobaths, retention can depend on the phase of the tide. Spawning shoalward of the 50 m isobath on the Northeast Peak greatly increases the chances of retention. These results apply to passive larvae and to those with specified vertical distributions and migration based on observations. Directional on‐bank swimming at rates of 0.5 to 1 body length per second would substantially enhance shoalward displacement, resulting in larval distributions during the first 2 months that are consistent with field observations.
Does water temperature determine year class strength in New Zealand snapper (Pagrus auratus, Sparidae)?
Authors: FRANCIS MALCOLM P. 
Published: October 2007

ABSTRACTThe abundance of 1+ snapper(Pagrus auratus)was estimated by trawl surveys and was found to vary 17‐fold over 7 years. There was a strong positive correlation between year class strength and autumn (April‐June) sea surface temperature during the 0+ year, with the latter explaining 94% of the variability in year class strength. The underlying mechanism is unknown, but three hypotheses relating snapper growth and survival to temperature are discussed. The strengths of the 1991 and 1992 year classes are predicted to be below average and extremely weak, respectively.
A study of spring‐and autumn‐spawned herring (Clupea harengus L.) larvae in the Norwegian Coastal Current during spring 1990
Authors: FOSSUM P. , MOKSNESS E. 
Published: October 2007

ABSTRACTAn intensive sampling program for yolk‐sac herring larvae and microzooplankton was carried out in the main spawning area of Norwegian spring‐spawning herring during March to April 1990 (between 62o and 63o30'N) to estimate their hatching period and the abundance of copepod eggs and nauplii. Additional investigations were carried out in the Skagerrak area during January‐March and on the Norwegian Shelf in May to study the otolith microstructure of the herring larvae. In May both autumn‐ and spring‐spawned herring larvae were found in the samples from the Norwegian Shelf. They were easily distinguished by differences in otolith microstructure. The pattern in increment widths in the otoliths of the autumn‐spawned larvae indicated that these larvae had not been transported through the Skagerrak area, but more likely were carried directly from the northern North Sea across the Norwegian Trench and into the Norwegian Coastal Current system. The calculated hatching of the spring‐spawned larvae sampled in May occurred significantly later than the observed hatching over the spawning grounds. The results suggest a mismatch between the abundance of first‐feeding herring larvae and their prey organisms, resulting in a higher survival of those herring larvae hatching during the latest part of the spawning period. This coincides with a general increase towards the middle of April in the abundance of prey organisms, from 1 to 4 1_1. There were no differences in otolith microstructure among spring‐spawned herring larvae sampled on the shelf in May, indicating that these larvae originated from the same cohort and were well mixed throughout the whole shelf area.
Distribution and abundance of two species of codlet (Teleostei, Bregmacerotidae) larvae from the south‐eastern Brazilian Bight
Authors: MATSUURA YASUNOBU , GARCIA ANA CLAUDIA DE SILVA , KATSURAGAWA MARIO , SUZUKI KAZUKO 
Published: October 2007

ABSTRACTTwo species of codlet (Bregmacerotidae) larvae were collected during nine survey cruises conducted in the south‐eastern Brazilian Bight between 23oS and 30oS in 1985‐91. Of 4846 codlet larvae collected during nine cruises, 99.2% were identified as Bregmaceros canton and only 0.8% were B. athanticus. The two species were more abundant during winter in the neritic region (60–135 m depth). Vertical distribution of codlet larvae was studied using the BIOMOC net, and vertical profiles of temperature/salinity and chlorophyll a concentration were recorded by CTD and fluorescent sonde. Only 9.0% of larvae were collected in the upper 30 m and 91.0% were found deeper (> 40 m). The depths of highest density of larvae bore a close relationship to the subsurface chlorophyll maximum layer. Some B. canton larvae were found in the upper 30 m layer at night, but no larva was found during the day. Water temperatures where B. canton larvae occurred ranged from 16 to 23oC, but most larvae were found at 18–20oC and in salinities of 35.5–36.5 psu.
Preparation of hatchery—reared chum fry for life at sea: osmoregulation dynamics
Authors: ZAPOROZHEC O. M. , ZAPOROZHEC G.V. 
Published: October 2007

ABSTRACTThe development of saltwater tolerance was studied in chum fry reared in the Malkinsky hatchery (central Kamchatka, 200 km from the Sea of Okhotsk). Hypo‐osmoregulatory ability of fry was assessed by dynamics of plasma sodium concentration, 24 and 48 h after their transfer from fresh water to seawater (30%o), and by fry survival in seawater of 40%o salinity. Complete osmoregulation function in young chum was developed in seawater only in late June, despite their earlier development of silver body color and fairly high migration activity. No correlation was found between the weight of fish and their osmoregulatory abilities. The reasons for late smoltification of hatchery‐reared chum have not yet been clearly defined. One explanation might be the combined effect of low nocturnal temperatures and considerable daily fluctuations in temperature (more than 8oC) during the period of egg incubation (in fall), as well as during smoltification of chum juveniles (spring‐early summer). Data on the osmoregulatory ability of chum smolts could be useful in forecasting their survival in the early marine period of life.
Occurrence of an exceptional catch of pelagic juvenile lingcod (Ophiodon elongatus) off Point Reyes, California
Authors: ADAMS PETER B. , RALSTON STEPHEN , LAIDIG THOMAS E. 
Published: October 2007

ABSTRACTAn exceptionally large catch of pelagic juvenile lingcod (Ophiodon elongatus) was made just offshore of Point Reyes, California in 1990. Results of 678 midwater trawls from annual surveys from 1983 to 1990 show that pelagic juvenile lingcod have a strong nearshore distribution and were most abundant in the Gulf of the Farallones, with a mean abundance of 5.0 per trawl. Otoliths from fish taken in the large catch were used to estimate parameters of a log‐transformed Gompertz growth model, which was then used to calculate hatch dates. Hatching peaked around 24 March and ranged from 10 March to 19 April, implying a January‐February spawning season for lingcod off central California. The large catch was associated with an anticyc‐lonic eddy which would lead to water being trapped near the coast; convergence of fish associated with the eddy may have been due to either physical or biological effects.
Sperm whales associated with Gulf Stream features off the north‐eastern USA shelf
Authors: WARING GORDON T. , FAIRFIELD CAROL P. , RUHSAM CYNTHIA M. , SANO MARGARET 
Published: October 2007

ABSTRACTMarine mammal surveys were conducted during sum Mer 1990 and 1991 in shelf‐edge and off‐shelf waters between Cape Hatteras and Georges Bank. Sperm whales were the most frequently sighted large whale in both years, constituting 27.9% and 12.7% of total sightings in 1990 and 1991, respectively. Sighting rates of sperm whales that were within a 9.3 km buffer (5 n.m.) of the Gulf Stream north wall were not significantly different (x2= 2.86, P > 0.05) from those within the Gulf Stream during 1990. In 1991, however, significantly more (x2= 51.0, P < 0.05) sightings were associated with shelf‐edge areas where warm core rings were located.
Causes of spatio‐temporal variation in the patchiness of larval fish distributions: differential mortality or behaviour?
Authors: FRANK KENNETH T. , CARSCADDEN JAMES E. , LEGGETT WILLIAM C. 
Published: October 2007

ABSTRACTWe studied age‐ and size‐related patterns in the patchiness of distributions of larval capelin (4–21 mm TL) on the Newfoundland Grand Bank. The distribution of yolk‐sac larvae was highly contagious, and was consistent with the distribution of spawning capelin. Lloyd's patchiness index declined fivefold from the yolk‐sac (4–6 mm) to the small post‐yolk‐sac (9–11 mm) stage. The patchiness index then increased steadily and by 2.5‐fold through the medium (14–16 mm) and large (19–21 mm) post‐yolk‐sac stages. This increase in patchiness was accompanied by a steady increase in the strength of the correlation between the abundance of larvae and of the edible zooplankton, and between the centre of mass of the larval and zooplankton vertical distributions through these length classes. In an attempt to distinguish between the alternative hypotheses of differential mortality or behavioural aggregation as the cause of the changes in larval capelin patchiness observed, we compared these changes with changes in the patterns of vertical migration, patchiness, and correlation with food abundances in a co‐occurring, non‐schooling zooplanktivore, Sagitta ekgans. Sagitta vertical migration and correlations between predatodprey abundance were similar to those observed in capelin. However, patchiness indices calculated for Sagitta were similar to the lowest values observed for capelin larvae. We conclude that the initial decline in patchiness observed in small larvae was due primarily to advection and diffusion away from the spawning site. The subsequent increase in larval patchiness, which did not occur in the non‐schooling Sagitta, was attributed to active behaviours of the larvae in response to the vertical and horizontal distributions of their prey. The implications of these findings for the interpretation of larval early life history are discussed.
Effects of a changing windfield on cod stocks of the North Atlantic
Authors: DICKSON R. R. , BRANDER K. M. 
Published: October 2007

ABSTRACTThis paper reviews the impacts of climatic change on six North Atlantic cod stocks during the present century – at Iceland, Greenland, Labrador, Faroes, the Barents Sea and the Baltic. Though the relevant changes in each region can all be set in the context of the same slow shifts in the large–scale Atlantic windfield, the mechanism and scale of the response is varied, operating through changes in the interstock exchange of larvae by ocean currents, direct effects of windiness on stratification, direct and indirect effects on environmental temperature and, in the special case of the Baltic, via the effects of westerly wind events on the inflow/ stagnation cycle of the Baltic Deeps. In certain places and times, these climatic influences have constituted the dominant control on the success of a stock.
Tintinnid ciliates as indicator species of different water masses in the western North Pacific Polar Front
Authors: KATO SATOSHI , TANIGUCHI AKIRA 
Published: October 2007

ABSTRACTDistributions of 10 dominant tintinnid taxa and groups in the western North Pacific Polar Frontal Zone or the Sanriku Waters were analysed on T‐S‐Plankton diagrams to estimate their values as indicator species of water masses. Because it is difficult to identify the origin of water by conventional T‐S analysis in areas such as this where three currents such as the warm Kuroshio, the Tsugaru Warm Current and the cold Oyashio are converging, reliable indicator species can be of great help in identification of the water masses. Normal cells of tintinnids with a soft body together with empty loricae were plotted separately on T‐S diagrams. Because empty loricae of most species were distributed over wider ranges of temperature and salinity, or empty loricae might remain suspended in a particular water mass for a fairly long time, tintinnid species including empty loricae were recognized as reliable indicator species. Because contrastingly different tintinnid faunas were derived from the Kuroshio and the Oyashio, water masses originating from both currents were clearly traced by the indicator species as would be expected. Furthermore, by employing the appropriate indicator species defined on the T‐S‐Plankton diagram, it was also possible to identify the most similar pair of water masses, i.e. the Tsugaru Warm Current and mixture of the Kuroshio and the Oyashio, which cannot be identified by conventional T‐S analysis.
What controls the distribution of the coccolithophore, Emiliania huxleyi, in the North Sea?
Authors: HOLLIGAN PATRICK M. , GROOM STEPHEN B. , HARBOUR DEREK S. 
Published: October 2007

ABSTRACTSatellite data show that the distribution of Emiliania huxleyi in the North Sea is characterized by considerable spatial patchiness as well as large annual differences in abundance within any particular area. The causes of this variability are largely unknown, and therefore unpredictable, reflecting a paucity of information on the ecophysiology of the species.
Photosynthesis characteristics of the phytoplankton in the Celtic Sea during late spring
Authors: PLATT TREVOR , SATHYENDRANATH SHUBHA , JOINT IAN , FASHAM MICHAEL J. R. 
Published: October 2007

ABSTRACTDuring a three‐week cruise to the Celtic Sea in late spring, the photosynthesis characteristics of the phytoplankton were followed at a single, nominal station. Observations were made on size–fractionated samples as well as on whole samples. The properties of the small (<1 μm fraction) and large (>1 μm fraction) differed with respect to the parameters aB (initial slope) and PBm (assimilation number) of the photosynthesis‐light curve and to the dependence of these parameters on environmental covariables. These differences account for some of the difficulty in explaining fluctuations in properties of unfractionated samples. Optical analysis leads to a method for estimation of photic depth, with high confidence, for days on which underwater irradiance measurements were not available. The shape of the vertical profile of photosynthetic pigments changed in a systematic way throughout the cruise. The implications for calculation of water‐column primary production are discussed. In the Celtic Sea, during late spring, use of a non‐spectral model assuming uniform water column for computation of primary production will lead to differences of up to 20% compared with the results of a fully spectral model that admits vertical stratification.
Diatom demography in winter – simulated by the Lagrangian Ensemble method
Authors: WOODS JOHN , BARKMANN WOLFGANG 
Published: October 2007

ABSTRACTAccording to Sverdrup's (1953) model of the spring bloom, phytoplankton biomass decreases in winter when the mixed layer depth exceeds the critical depth. We have used a one‐dimensional mathematical model integrated by the Lagrangian Ensemble method to simulate a population of diatoms during the winter between two growing seasons off the Azores. The model allows us to diagnose the demographic changes in the simulated diatom population from a variety of perspectives. The total population falls to a minimum of 70 million diatoms m‐2 at the end of February. The vertical distribution of the population dynamics is first analysed in terms of daily Eulerian averages over 1 m depth intervals. Growth starts in February when the diurnal thermocline becomes shallower than 50 m, but while the mixed layer is still 200 m deep. The natural mortality has a minimum in winter because it is reduced (in the model) with temperature and population density. Eulerian analysis suggests that in winter, diatoms have a life expectancy of more than 3 months, so a significant number will survive the months of December, January and February when there is very little growth. Losses to grazing are negligible in winter. Lagrangian analysis shows how an individual diatom responds to its changing ambient environment caused by variation in depth (due to turbulent mixing) and the diurnal and seasonal changes in the photosynthetically active radiance. The different trajectories followed by the thousands of plankton particles simulated by the model produce diversity in growth rate ranging over several orders of magnitude, so care has to be taken in statistical analysis.The paper ends with a re‐assessment of the value of the critical depth and compensation depth as predictors for onset of the spring bloom. The compensation depth was computed by Eulerian averaging over 1 m depth inter‐vals each day. For 1 month after the vernal equinox the compensation depth follows the ascent of the mixed layer as it rises from a depth of 100 m to 40 m. Lagrangian analysis reveals that this is due to the photo‐adaptation better matching the ambient irradiance experienced by diatoms in the mixed layer compared with those at the same depth in the seasonal thermo‐cline. By mid‐April the spring bloom has already ad‐vanced so far that self shading influences the compensation depth, which then rises into the mixed layer. We conclude that Sverdrup's criterion is not useful for predicting changes in the diatom population simulated by our model.
Generation of a phytoplankton maximum in a grazing‐extended logistic model
Authors: ROTHSCHILD B. J. , PATRICK E. V. 
Published: October 2007

ABSTRACTThe cause of variability in the vertical distribution of phytoplankton has been a subject of considerable interest, particularly in the development of various ‘global change’ scenarios. The classic two‐layer explanation for the phytoplankton maximum form of vertical variability derives from physical considerations: a switching in the sign of production owing to a stepwise reduction in irradiance with increasing depth. This paper shows how quasi‐periodicity in the vertical distribution of phytoplankton and the special case of a ‘maximum’ can arise from zooplankton grazing. To show this we employ the dynamics of the grazing‐extended logistic model.
Alternative methods for the estimation of immigration to the Icelandic cod stock
Authors: SHEPHERD J. G. , POPE J. G. 
Published: October 2007

ABSTRACTPeriodic migrations offish from Greenland are known to have augmented the Icelandic cod stock on many occasions during the last 50 y. These immigrations have been observed both in the catch‐at‐age compositions, and through tagging experiments. Two new and independent methods for estimating the extent of immigration have been developed, based on (a) analysis of weight‐at‐age data; (b) comparison of virtual population analyses for a restricted range of ages and the full range of ages in the available data. Both methods confirm recent strong immigration of the 1973 and 1984 year classes, but also suggest that significant immigration was a fairly regular event throughout the 1970s, and also occurred in 1985. It appears that immigration is quite strongly correlated with the year‐class strength at Greenland, and that between 20% and 60% of the Greenland fish eventually return to rejoin the Icelandic stock.
Stock'related changes in biological parameters of the Icelandic summer'Spawning herring
Authors: JAKOBSSON J. , GUØMUNDSDÓTTIR A. , STEFÁNSSON G. 
Published: October 2007

ABSTRACTDuring the period 1960–1992 the stock size of Icelandic summer‐spawning herring varied from about 300 000 t in the early 1960s to just above 10000 t in the early 1970s. Since then the stock size has increased to about 400 000 t in 1992. Examination of the mean weight at age and length at age as well as condition factor of the herring revealed that these parameters have fluctuated slightly, but without a trend, over a wide range of stock abundance, but increased when the stock was at extremely low level of stock abundance. Examination of the stock‐recruitment relationship revealed that there were clear positive signs of increased recruitment at high stock levels. Similarly there were signs that the recruitment level was greatly affected by the cold period 1964–1971. Comparison of the VPA stock estimates and acoustic stock estimates indicated that the natural mortality is in the range of 0.1‐0.15.