Showing papers by "Memorial University of Newfoundland published in 1984"
TL;DR: A centroid SAHN clustering algorithm that requires 0(n2) time, in the worst case, for fixedk and for a family of dissimilarity measures including the Manhattan, Euclidean, Chebychev and all other Minkowski metrics is described.
Abstract: Whenevern objects are characterized by a matrix of pairwise dissimilarities, they may be clustered by any of a number of sequential, agglomerative, hierarchical, nonoverlapping (SAHN) clustering methods. These SAHN clustering methods are defined by a paradigmatic algorithm that usually requires 0(n
3) time, in the worst case, to cluster the objects. An improved algorithm (Anderberg 1973), while still requiring 0(n
3) worst-case time, can reasonably be expected to exhibit 0(n
2) expected behavior. By contrast, we describe a SAHN clustering algorithm that requires 0(n
2 logn) time in the worst case. When SAHN clustering methods exhibit reasonable space distortion properties, further improvements are possible. We adapt a SAHN clustering algorithm, based on the efficient construction of nearest neighbor chains, to obtain a reasonably general SAHN clustering algorithm that requires in the worst case 0(n
2) time and space. Whenevern objects are characterized byk-tuples of real numbers, they may be clustered by any of a family of centroid SAHN clustering methods. These methods are based on a geometric model in which clusters are represented by points ink-dimensional real space and points being agglomerated are replaced by a single (centroid) point. For this model, we have solved a class of special packing problems involving point-symmetric convex objects and have exploited it to design an efficient centroid clustering algorithm. Specifically, we describe a centroid SAHN clustering algorithm that requires 0(n
2) time, in the worst case, for fixedk and for a family of dissimilarity measures including the Manhattan, Euclidean, Chebychev and all other Minkowski metrics.
877 citations
TL;DR: In this paper, trace-element analyses (Cr, Ni, V, Cu, Ti, Zr, Y) of flysch sandstones indicate that ophiolite obduction either did not occur or was of minor importance during the Taconic Orogeny in the United States Appalachians.
Abstract: Flysch generated along the Appalachian orogen during the Ordovician Taconic Orogeny ranges in age from late Arenig to early Caradoc (allochthonous flysch) and from late Llanvirn to Ashgill (autochthonous flysch). Sandstones in these units are dominantly lithic arenites, with a heavy mineral suite containing common to abundant Mg-rich chromite north of the Canada–United States border. The only reasonable sources for the chromite were the lower ultramafic units of obducted ophiolites. Trace-element analyses (Cr, Ni, V, Cu, Ti, Zr, Y) of flysch sandstones indicate a striking increase in Cr and Ni concentrations from the United States Appalachians to the Canadian Appalachians. In the United States units, Cr is in the range of 10 to 50 ppm; Canadian flysch units average an order of magnitude more Cr. These results suggest that ophiolite obduction either did not occur or was of minor importance during the Taconic Orogeny in the United States Appalachians. The difference in ophiolite abundance between the Canadian and United States Appalachians suggests a fundamental difference in tectonic style along the orogen, a feature that must be accommodated by plate-tectonic models. New models will probably need to consider both obliquity of subduction and geological complexity of the Ordovician collision zone in order to explain the spatial distribution of obducted ophiolite sheets.
187 citations
TL;DR: For 371 persons in 17 kindreds, at risk for APKD by virtue of having an affected first degree relative, the estimated probability of clinical diagnosis ofAPKD is calculated to be 0.011 by age 20, 0.041 by age 30, 1 by age 40, 2 by age 50, and 0.404 by age 60 years.
Abstract: Few reports are available on the age-related risk of relatives of affected persons to manifest adult polycystic kidney disease (APKD). For 371 persons in 17 kindreds, at risk for APKD by virtue of having an affected first degree relative, we calculated the estimated probability of clinical diagnosis of APKD to be 0.011 by age 20, 0.041 by age 30, 0.115 by age 40, 0.299 by age 50, and 0.404 by age 60 years (expected = 0.50). Ultrasonographic examination of 172 asymptomatic persons at risk showed definite APKD in 60. The probability of ultrasonographic detection of asymptomatic APKD is estimated as 0.222, 0.657, and 0.855 at age 5, 15, and 25 years, respectively. The probability of having APKD following normal ultrasonogram results (conservatively assuming 90% specificity) is estimated as 0.46, 0.28, and 0.14 for persons at 50% risk in their first, second, or third decade. The marginal benefit of ultrasound as a diagnostic test for APKD for persons in the second or third decade is estimated as 0.37 and 0.41, respectively for a "positive" test and 0.22 and 0.37 for a "negative" test.
160 citations
TL;DR: The prognosis for subjects with APKD is much better than most reports suggest and can be estimated from the time-to-event data presented.
133 citations
TL;DR: Heat shocks or hydrostatic pressure shocks, when completed within 20 min of fertilization at 10°C, were found to induce 100% triploidy with 70–90% survival (relative to controls) in landlocked Atlantic salmon.
122 citations
TL;DR: Greenland cod trypsin was isolated from the pyloric ceca of Greenland cod and had a molecular weight of 23,500; but it had less potential disulfide pairs, less alpha-helix and a lower H phi ave than other trypsins previously characterized.
Abstract: 1. Trypsin(ogen) was isolated from the pyloric ceca of Greenland cod. 2. Greenland cod trypsin catalyzed hydrolysis of Nα-benzoyl- dl -arginine p -nitroanilide, tosyl arginine methyl ester and protein and was inhibited by the serine protease inhibitor PMSF and other well-known trypsin inhibitors. 3. Greenland cod trypsin was more stable at alkaline pH than at acid pH; and was inactivated by relatively low thermal treatment. 4. Like other trypsins, the enzyme was rich in potential acidic amino acid residues but poor in basic amino acid residues and had a molecular weight of 23, 500; but it had less potential disulfide pairs, less α-helix and a lowerHΦ ave than other trypsins previously characterized. 5. Reactions catalyzed by Greenland cod trypsin were not very responsive to temperature change, such that specific activity was relatively high at low reaction temperature.
112 citations
TL;DR: The nucleus of triploid erythrocytes occupied a greater percentage of the corpuscular volume than did the diploid nucleus, and mean cytoplasmic haemoglobin concentration was found to be the same for diploids and triploids when this was taken into account.
Abstract: Triploid landlocked Atlantic salmon had a larger mean erythrocyte volume but lower erythrocyte count than diploids; the haematocrit was the same in diploids and triploids. Although the total blood haemoglobin content and the mean corpuscular haemoglobin concentration were lower in triploids than in diploids, the actual mean corpuscular haemoglobin content of triploid erythrocytes was higher than that of diploids. The increase in triploid mean erythrocyte volume was mainly due to an increase in cell length; there was only a minor increase in cell width and no increase in cell height. The nucleus of triploid erythrocytes occupied a greater percentage of the corpuscular volume than did the diploid nucleus. Mean cytoplasmic haemoglobin concentration was found to be the same for diploids and triploids when this was taken into account
111 citations
TL;DR: Gonad weight and reproductive output of urchins from habitats poor in food can be increased by providing preferred foods.
107 citations
TL;DR: Energy balance is positive at all times of the year, and conversion efficiency is high, suggesting that conditions are favourable.
Abstract: Mytilus edulis L. occupies a habitat in eastern Newfoundland, Canada, which is characterised by low temperatures and a lower concentration of particles in suspension than is found in estuarine locations. Gametogenesis occurs in the spring, and energy reserves from the previous year are not utilised in the synthesis of gametes. Oxygen uptake is not elevated during the winter, in contrast to most European populations, which undergo gamete development at that time. There is little seasonal variation in clearance rate. This may be attributable in part to the absence of the high particulate load which has been shown to depress feeding activity in some estuarine populations. Energy balance is positive at all times of the year, and conversion efficiency is high, suggesting that conditions are favourable. A number of physiological comparisons are made between Newfoundland mussels and those from European waters.
107 citations
TL;DR: The energetics of postnatal growth and development of wild and captive Northern Gannet chicks are described and net growth efficiency was 49% to 8 weeks of age and 33% to fledging at 13 weeks.
Abstract: We describe the energetics of postnatal growth and development of wild and captive Northern Gannet chicks. For 14 chicks 0-9 weeks old, a 24-week immature, and a
breeding female, we determined water, lipid, and nonlipid content. During the 13-week nestling period, mass increased over 40-fold. Accumulation of lipid caused the energy density of chicks to increase steadily through 9 weeks. Lipid eventually accounted for about 60% of energy in tissues. Two captive chicks grew at rates comparable to wild young and consumed, on average, about 24 kg of fish containing 190,000 kJ during the nestling period.
The energy density of chick guano was 13.3 ± 0.8 kJ/g. Estimated metabolizable energy (ME) rose rapidly from 952 kJ during week 1 to 19,318 kJ during week 6, after which ME
fluctuated between about 9,000 and 16,400 kJ/week. During week 1, the growth increment (GI) was 801 kJ; GI increased sharply to 9,667 kJ during week 4 and peaked at 12,711 kJ in
week 7. Net growth efficiency was 49% to 8 weeks of age and 33% to fledging at 13 weeks. The food requirement of the gannet population of Newfoundland is estimated.
104 citations
TL;DR: It is concluded that pelleted LHRH analog may be used to advance and synchronize ovulation in Atlantic salmon, especially in ripened females nearing the time for natural spawning.
TL;DR: A modified form of a “time trade-off” technique is used to estimate the patient's perception of the utility or worth of their ESRD health state to suggest factors other than form of treatment are important determinants of the quality of life for these patients.
Abstract: Survival in end-stage renal disease seems to depend more on age and associated diseases than on the form of treatment. Previously published comments on the quality of life experienced by patients t...
TL;DR: This paper presents efficient parallel algorithms for the following graph problems: finding the lowest common ancestors for vertex pairs of a directed tree; finding all fundamental cycles, a directed spanning forest, all bridges, all bridge-connected components, all separation vertices, all biconnected components, and testing the biconsnectivity of an undirected graph.
Abstract: In this paper, we present efficient parallel algorithms for the following graph problems: finding the lowest common ancestors for vertex pairs of a directed tree; finding all fundamental cycles, a directed spanning forest, all bridges, all bridge-connected components, all separation vertices, all biconnected components, and testing the biconnectivity of an undirected graph. All these algorithms achieve the $O(\lg ^2 n)$ time bound, with the first two algorithms using $n\lceil n /\lg n\rceil $ processors and the remaining algorithms using $n\lceil n/\lg ^2 n \rceil $ processors. In all cases, our algorithms are better than the previously known algorithms and in most cases reduce the number of processors used by a factor of $n\lg n$. Moreover, our algorithms are optimal with respect to the time-processor product for dense graphs, with the exception of the first two algorithms.The machine model we use is the PRAM which is a SIMD model allowing simultaneous reads but not simultaneous writes to the same memory...
TL;DR: Three different ways have been selected for analyzing a story's structure, each focusing on different types of information as mentioned in this paper, with the best narratives generally deemed sophisticated and complex in at least two of the three systems.
Abstract: Three different ways have been selected for analyzing a story's structure, each focusing on different types of information. (a) Episodic or story grammar approaches stories as problem-solving episodes, emphasizing goals and activities to achieve them. (b) Labov's high point structure emphasizes affective information and sees stories as organized around emotional high points or crisis events. (c) Deese's dependency analysis emphasizes linguistic complexity and, in particular, the way propositions are related to each other through a relationship of either coordination or subordination. Stories were scored according to how well they realized good structure in each system, and the three scoring systems were relatively independent of each other. Adults were asked to rate 3-to 9-year old children's personal narratives in terms of how good a story each was, and their ratings were compared to how the stories were scored in terms of all three systems. None of the systems completely explained the subjective quality ratings; rather, all three seemed to contribute in different ways to subjects' ratings, with the best narratives generally deemed sophisticated and complex in at least two of the three systems.
TL;DR: Restriction enzyme analysis of the plasmids, combined with measurements of specific activities of the enzymes in crude extracts of cells bearing recombinant plasmid pBR322, clarified the relative position of speA and speB.
TL;DR: Twelve transfer-derepressed plasmids from incompatibility groups I1, I5, B, K and Z were constructed and found to determine thin flexible and thick rigid pili constitutively, indicating that thin pili were apparently not involved directly in conjugation but were only used to stabilize mating aggregates.
Abstract: Eleven transfer-derepressed plasmids from incompatibility groups I1, I5, B, K and Z were constructed using the dnaG3 mutant Escherichia coli strain BW86. All were found to determine thin flexible and thick rigid pili constitutively. Immune electron microscopy was used to relate thick and thin pilus serotypes with incompatibility grouping. Mutant plasmids that determined only thick pili constitutively transferred efficiently on an agar surface but not in a liquid, whereas plasmids with both kinds of pili transferred equally well in both environments. A mutant of the Incl2 plasmid R721 determined thin pili constitutively, and thick pili at a repressed level, as indicated by electron microscopy. Experiments with this indicated that thin pili were apparently not involved directly in conjugation but were only used to stabilize mating aggregates.
TL;DR: It is concluded that this region contains premotor elements forming part of the internuncial network organizing oesophageal peristalsis, and the source of postulated cholinergic afferents to these neurones remains to be identified.
TL;DR: The ocean pout AFP do not contain the abundance of alanine found in winter flounder and shorthorn sculpin AFP nor the high half-cystine residues observed in sea raven AFP, suggesting that ocean p out AFP represent a new type of macromolecular antifreeze.
Abstract: Eight major antifreeze polypeptides (AFP) were purified from the sera of Newfoundland ocean pout. Except for their approximately identical size (6,000 Dalton), these components were shown to be separate entities by their behaviour on polyacrylamide gel electrophoresis, ion exchange chromatography, gel permeation and reverse phase high performance liquid chromatography. They could also be divided into two cross-reactive, yet distinct, immunological groups. Amino acid analysis demonstrated that ocean pout AFP are different from all of the other antifreezes studied to date. The ocean pout AFP do not contain the abundance of alanine (60 mol%) found in winter flounder and shorthorn sculpin AFP nor the high half-cystine residues (8 mol%) observed in sea raven AFP. It is suggested that ocean pout AFP represent a new type of macromolecular antifreeze.
TL;DR: The ARAL series as mentioned in this paper is a broad coverage of a multitude of areas in the field of applied linguistics, and the overall high quality of this series makes it essential not merely to research libraries, but also to the personal reference shelves of serious scholars involved in any way with language.
Abstract: According to Books in Print, a third issue of ARAL has appeared in 1983. This issue was not available for this review, but its appearance marks the significant fact that the publication is now more than half way through those crucial first five years of publication. I n fine, ARAL is not merely another specialised publication. It is directed to a diverse readership. Its particular forte lies in a broad coverage of a multitude of areas in the field of applied linguistics. The overall high quality of this series makes it essential not merely to research libraries, but also to the personal reference shelves of serious scholars involved in any way with language.
TL;DR: In this paper, the Davydov Hamiltonian is transformed into normal coordinates and the Fr\"ohlich Hamiltonians are canonically transformed into an equivalent from within the Hartree-Fock approximation.
Abstract: Two physical models to explain the unusual behavior of biological systems put forward by Fr\"ohlich and Davydov are reviewed. The Davydov Hamiltonian is transformed into normal coordinates and the Fr\"ohlich Hamiltonian is canonically transformed into an equivalent from within the Hartree-Fock approximation. A model Hamiltonian capable of relating both theories is proposed. The resulting analysis employs only one type of second-quantized operators which describe the effect on the active dipolar modes of vibration in biological cells. An equation of motion is derived for the creation and annihilation operators that are used. When the phenomenon of Bose condensation is taken into account, the field translation variable is shown to obey a nonlinear Schr\"odinger equation. Its solutions are provided and their significance is discussed. Some of the solutions are shown to correspond to properties already examined by Fr\"ohlich and Davydov. New solutions are found and interpreted as interfaces between either an ordered and a disordered phase or two ordered phases existing in the biosystem. The relationship between the two theories of biological order is demonstrated and discussed.
TL;DR: There was no difference between diploid and triploids Atlantic salmon in either oxygen consumption rate or P O 2 at asphyxiation, in spite of the increase in erythrocyte volume and lower blood haemoglobin content associated with triploidy.
TL;DR: Biomass and abundance at the edge of the Grand Banks are unexpectedly low, and larger animals, including fishes, that forage there must depend more on pelagic than on benthic food sources.
Abstract: The abundance, biomass and mean weight of macrofauna in the Carson Canyon region (Lat. 45°30′N, Long. 48°40′W) of the Grand Banks were estimated from 40 quantitative infaunal samples taken at 15 stations in June 1980. In contrast to other areas, there were no significant differences in these values between samples taken in and outside of the canyon. Abundance (\(\bar x\) = 716 individuals m-2), biomass (\(\bar x\) = 10.9 gm-2), and mean weight (\(\bar x\) = 0.03 g individual-1) displayed no consistent relationship with depth, but stations grouped according to sediment type had differing dominant taxa. Biomass and abundance at the edge of the Grand Banks are unexpectedly low. Larger animals, including fishes, that forage there must depend more on pelagic than on benthic food sources.
TL;DR: In this article, a review summarizes recent advances, problems newly illuminated by recent Earth rotation data (for example mantle anelasticity, core-mantle coupling) and problems still unresolved.
Abstract: Over the last decade considerable progress has been made in closing the gap between geophysical theory and the observed changes in the Earth9s spin rate and polar motion, which are affected by the Earth’s internal structure, properties and processes. New observational techniques and data have had a marked impact on understanding the short-term variations in the length of day and pole position, but we can expect between another 5 and 30 years to pass before they permit improved explanations of longer-term phenomena (18.6 year tidal effects, the Markowitz wobble, decade fluctuations in the length of day, etc.) This review summarizes recent advances, problems newly illuminated by recent Earth rotation data (for example mantle anelasticity, core-mantle coupling) and problems still unresolved.
TL;DR: It is argued in this paper that the mother monitors her pup's following by listening to the frequent, individually characteristic vocalization of her pup, which can be produced in air and water simultaneously and as such could serve as a precise location mechanism.
Abstract: The Harbour seal pup is predisposed to follow its mother's movements which helps to ensure that the pair stays together. The mother monitors her pup's following and it is argued in this paper that she does so primarily by listening to the frequent, individually characteristic vocalization of her pup. This call can be produced in air and water simultaneously and as such could serve as a precise location mechanism.
TL;DR: The immunologic abnormalities seen with acquired immune deficiency syndrome (AIDS) are reminiscent of the immune changes seen in various nutritional deficiency states as mentioned in this paper, and it is proposed that AIDS is an opportunistic infection with a retrovirus, such as the human T cell leukemia virus, that predominantly affects people at high risk due to a variety of underlying factors, including nutritional deficits.
TL;DR: The Lower Cambrian Bradore Formation rests unconformably on Precambrian gneiss and was deposited during a time of global sea-level rise as discussed by the authors, during which a large number of vertical burrows (Skolithos) obliterate all primary physical structures.
Abstract: The Lower Cambrian Bradore Formation rests unconformably on Precambrian gneiss and was deposited during a time of global sea-level rise The basal 30-m (Blanc-Sablon Member, new name) consist of pebbly, subarkosic, trough and planar-tabular crossbedded sandstone and pebble conglomerate The succeeding 20 m (Crow Head Member, new name) are similar in texture, but abundant vertical burrows (Skolithos) obliterate all primary physical structures The upper 10 m (L'Anse-au-Clair Member, new name) consist of quartzose coarse sandstone with polymodal crossbed orientations (trough and planar-tabular), locally common Skolithos, and scattered Conichnus, Dolopichnus and ?Monocraterion The Blanc-Sablon Member is a braided-fluvial deposit with easterly directed trough crossbedding indicating flow away from the centre of the craton Planar-tabular crossbed sets (up to 15 m thick) are commonly oriented at high angles to surrounding troughs (up to 90 degrees) and were probably deposited by migration of transverse or cross-channel bars Braid channels built directly to the coast, prompting comparison with fan deltas The river sands were extensively reworked by vertical burrowers (Skolithos, Lingulichnus) in distributary-mouth estuaries (Crow Head Member) The L'Anse-au-Clair Member is mineralogically more mature than the rest of the formation and rests sharply on the Crow Head Member It is also in sharp contact with shales and carbonates of the overlying Forteau Formation The L'Anse-au-Clair Member consists of sands that filled laterally migrating tidal inlets of a barrier coastline However, the upper parts of the barriers were removed by shoreface erosion during marine transgression The Bradore Formation and its equivalents around the North American craton indicate that the craton margin was covered by a blanket of immature alluvium prior to the Early Paleozoic transgression The alluvium resulted from denudation of the barren, unvegetated North American craton under wet, tropical conditions SEDIMENTOLOGIE ET ICHNOLOGIE DE LA FORMATION BRADORE (CAMBRIAN INFERIEU) DE LA COTE DE TERRE NEUVE: SERIE TRANSGRESSIVE FLUVIALE-MARINE PEU PROFONDE RESUME La Formation Bradore (Cambrien inferieur), deposee durant une montee globale du niveau marin, est discordante sur les gneiss precambriens Un gres subarkosique a galets et a stratification entrecroisee planaire et a creux (tabular and trough cross-bedded) forme les trente metres inferieurs (Membre Blanc-Sablon, nom nouveau) Les vingt metres sus-jacents (Membre Crow Head, nom nouveau), comporte des roches a texture semblable, cependant que de nombreux terriers (burrow) verticaux (Skolithos) ont tetruit toute structure physique Un gres quartzite grossier a stratification entrecroisee a orientation plurimodale (planaire et a creux), avec, localement, de nombreux Skolithos et Conichnus, Dolopichnus eparpilles et ?Monocraterion forment les dix metres superieurs (Membre L'Anse-au-Claire, nom nouveau) Le Membre Blanc Sablon est un depot de riviere anastomosee, a stratification entrecroisee a creux dont le pendage Est indique un ecoulement s'eloignant du centre du craton L'orientation des series de stratification entrecroisee planaire (jusqu'a 15 m d'epaisseur) est fortement oblique (jusqu'a perpendiculaire) a celle des stratifications entrecroisees a creux; les series planaires furent probablement deposees durant la migration de bancs transversaux Des chenaux anastomoses furent developpes directement en direction cotiere, suggerant la comparaison a un cone de dejection Les gres fluviaux furent restructures par des terriers (Skolithos, Lingulichnus) au sein des estuaires effluents (Membre Crow Head) Le Membre L'Anse-au-Clair comporte des roches mineralogiquement plus murs que le reste de la formation, et presente un contact aigu avec le Membre Crow Head sous-jacent, ainsi qu'avec les argiles et les roches calcaires de la Formation Forteau sus-jacente Les gres qui remplissent des chenaux de maree qui migrent sur en cordon littoral forment le Membre L'Anse-au-Clair Les cretes des cordons sableux furent cependant erodees durant la transgression marine qui suivit La Formation Bradore et ses equivalents en bordure de craton nord-americain indiquent que la marge cratonique fut couverte avant la transgression du paleozoic inferieur par un manteau d'alluvions peu evolues Les alluvions furent issus de l'erosion en regime tropical humide du craton nord-americain sterile et sans vegetation Traduit par A Zolnai End_Page 11-------------------------
TL;DR: It is suggested that the demonstrated dominance of brook trout in slow flows may be related to the species' preference for lentic habitats in natural stream environments and that this phenomenon may affect species segregation.
Abstract: An instream viewing facility was used to determine whether brook trout Salvelinus fontinalis or rainbow trout Salmo gairdneri show hierarchical dominance in slow- and fast-flow stream habitats. Nine trials with interspecific pairs of wild immature fish matched for length (mean fork length, 13.7 cm) were conducted in each flow regime. In the slow-flow habitat, brook trout dominated rainbow trout in five of the six trials in which dominance was established. No species advantage was observed in the fast-flow habitat; each species achieved dominance four times. Dominant fish, regardless of species or flow, initiated most of the aggressive behaviour and gained weight whereas subordinates lost weight. We suggest that the demonstrated dominance of brook trout in slow flows may be related to the species' preference for lentic habitats in natural stream environments and that this phenomenon may affect species segregation. Received September 26, 1983 Accepted August 25, 1984
01 Jan 1984
TL;DR: Northern (Labrador-eastern Newfoundland shelf) Atlantic cod (Gadus morhua) spawn in March-June and are joined by fish maturing for the first time in a fall migration back to the spawning grounds.
Abstract: Northern (Labrador-eastern Newfoundland shelf) Atlantic cod (Gadus morhua) spawn in March-June at depths in excess of 250 m and at bottom temperatures near 3 C. The eggs develop as they drift in the Labrador Current to shallow nursery grounds 600–1,000 km to the south. Spent adults also move southward and westward toward the coast of Labrador and Newfoundland, perhaps homing to the same areas where they grew up. The shoreward migration, through a layer of colder (-1.5 to 0 C) water, may be guided by migrating capelin (Mallotus villosus) on which the cod feed. Adults are joined by fish maturing for the first time in a fall migration back to the spawning grounds.