Field examination of dispersion patterns of juvenile Iceland scallops (Chlamys islandica) in the northern Gulf of St Lawrence

2000 ◽  
Vol 80 (3) ◽  
pp. 501-508 ◽  
Author(s):  
David J. Arsenault ◽  
Martin C. Giasson ◽  
John H. Himmelman
Keyword(s):  
Experimental Evidence ◽  
Shell Height ◽  
Tidal Currents ◽  
Nursery Areas ◽  
Chlamys Islandica ◽  
Dispersion Patterns ◽  
Size Groups ◽  
The Mean ◽  
Spatial Size ◽  
Iceland Scallops

The movement of juvenile Iceland scallops, Chlamys islandica, was quantified in an inshore bed in the Mingan Islands, northern Gulf of St Lawrence, to examine whether the size partitioning over depth in this location, increasing scallop size with depth, results from a gradual downslope movement as scallops increase in size. Scallops of 30.0-44.9 mm and 45.0-59.9 mm in shell height were collected using SCUBA, tagged, and released in the centre of two 0.4-km2 grids at 15 m in depth. After 7 d and 48 d, the net distance moved by the scallops from the release points did not vary between the two size groups but varied significantly between grids. The majority of scallops (70-94%) moved downslope and the mean movement vectors were not orientated in the direction of tidal currents, but rather towards increasing depth. The downslope movement of the scallops was possibly explained by more prolonged swimming bouts when scallops swam downslope. The results suggest that the spatial size partitioning of Iceland scallops at this location is caused by a gradual downslope movement as the scallops increase in size. This study provides the first experimental evidence supporting the controversial hypothesis of recruitment into adult scallop populations involving swimming of juveniles from nursery areas.

Interspecific differences in the distribution of adult and juvenile ponyfish (Leiognathidae) in the Gulf of Carpentaria, Australia

1999 ◽  
Vol 50 (7) ◽  
pp. 643 ◽  
Author(s):  
J. Staunton-Smith ◽  
S. J. M. Blaber ◽  
J. G. Greenwood
Keyword(s):  
Linear Increase ◽  
Small Fish ◽  
Common Pattern ◽  
Widespread Species ◽  
Nursery Areas ◽  
Interspecific Differences ◽  
Coastal Species ◽  
The Common ◽  
The Mean ◽  
Coexisting Species

The distribution of leiognathids was investigated at 261 sites spread throughout the Gulf of Carpentaria. Eight species, Gazza minuta, Leiognathus decorus, L. equulus, L. fasciatus, L. leuciscus, L. smithursti, L. splendens and Secutor ruconius, were usually restricted to coastal areas, whereas four species, L. bindus, L. moretoniensis, Leiognathus sp. and S. insidiator, were not. Two other species, L. aureus and L. elongatus, were caught at only one site each. The relationships between size of fish and depth in Albatross Bay were investigated by examining the mean weight and minimum and maximum lengths of different species in 356 trawls. Six of the coastal species showed the common pattern of linear increase in size with depth. This pattern is consistent with the existence of estuarine and/or inshore nursery areas, and supports previous observations of these species. In contrast, three of the widespread species exhibited approximately quadratic relationships between size and depth. This unusual pattern resulted from small fish living in both the shallow inshore areas and deeper offshore areas, and it may reduce competition among the juveniles of the large number of very abundant, coexisting species of leiognathid.

scholarly journals Dynamics of stock for yesso scallop Mizuhopecten yessoensis (Jay, 1856) in the northwestern Tatar Strait from the beginning of its fishery to nowadays

2021 ◽  
Vol 201 (3) ◽  
pp. 533-546
Author(s):  
P. A. Dulenina ◽  
A. A. Dulenin
Keyword(s):  
Shell Height ◽  
Mizuhopecten Yessoensis ◽  
Tatar Strait ◽  
Yesso Scallop ◽  
The Mean ◽  
Commercial Value ◽  
Northwestern Tatar Strait ◽  
Commercial Stock

Settlements of yesso scallop Mizuhopecten yessoensis in the northwestern Tatar Strait (within the waters of Khabarovsk Region) are considered on the data of scuba (< 20 m depth) and dredge (> 20 m depth) surveys conducted in 2001–2018. To 2018, only two settlements remain in this area from 9–12 ones in 2010–2014; both remained settlements have no commercial value. Trend to decreasing of the settlements density is shown: the mean density was 3.0 ind./m2 in 2001, 0.20 ind./m2 in 2010, and 0.0005 ind./m2 in 2018. Commercially valuable scallops with the shell height > 120 mm prevailed in the settlements (86–100 %), whereas juveniles were rare or absent (1.6 %, on average) in all years of surveys. CPUE decreased from 200 kg/diver/hour in 2001–2003 to 10 kg/diver/hour in 2018. These changes are obviously reasoned by overexploitation of the population using dredging and scuba gathering. Total commercial stock of yesso scallop dropped to the minimal value in 2018: 200 t, that was in 4.5 times lower than the established limit. Thus, 5 years ban is established for M. yessoensis landing in the area.

scholarly journals Bakerian Lecture :─On the variation of the specific heat of water, with experiments by a new method

1912 ◽  
Vol 86 (587) ◽  
pp. 254-257 ◽  
Keyword(s):  
Specific Heat ◽  
Experimental Evidence ◽  
Electric Current ◽  
Heat Loss ◽  
Mean Value ◽  
Mechanical Method ◽  
Order Of Accuracy ◽  
Steady Current ◽  
Differential Pair ◽  
The Mean

The question of the variation of the specific heat of water is so fundamental in calorimetry, and the results of different observers and different methods are still so discordant, that no apology is needed for the publication of fresh experimental evidence. The continuous electric method, which I carried out in conjunction with Prof. Barnes, was specially designed to avoid the main sources of error of the older methods in which mercury thermometers and open calorimeters were employed. In this method. the rise of temperature of a steady current of water, heated by a steady electric current in its passage through a fine tube hermetically scaled in a vaccumjacket, was observed with a differential pair of platinum thermometers. Errors due to lag, or to uncertainty of water-equivalent, or to evaporation or heat-loss in transference, were thus eliminated, and a higher order of accuracy was secured in the temperature measurements. The results of the continuous electric method in the case of water showed a variation of specific heat amounting to less than one half of 1 per cent. between 10° and 80°C., with a minimum at 37.6°C., followed by a very slow and steady rise. The mean value from 0° to 100°C. agreed to 1 in 2000 with the experiments of Reynolds and Moorby by the mechanical method, and the values from 5° to 35° C. agreed to a similar order of accuracy with the experiments of Rowland. But the value at 80°C. was 1 per cent. lower than that found by Lüdin's (Zürich, 1895), employing the ordinary method of mixture with an open calorimeter and mercury thermometers. Lüdin's results for the variation over the range 30° to 100°C. agreed more closely with the continuous electric method than those of any previous observers; but showed a minimum at 25°C., and a maximum at 87°C., which could not be reconciled with the experiments of Reynolds and Moorby on the mean specific heat from 0° to 100°C., or with the most probable reduction of Regnault's experiments between 110° and 190°C.

A decadal study of biometric and imposex indices in two gastropods

2019 ◽  
Vol 99 (7) ◽  
pp. 1601-1614
Author(s):  
J. M. Ruiz ◽  
B. Carro ◽  
N. Albaina ◽  
L. Couceiro ◽  
M. Quintela ◽  
...  
Keyword(s):  
Vas Deferens ◽  
Shell Height ◽  
Chemical Analyses ◽  
Nucella Lapillus ◽  
Nw Spain ◽  
Potential Applications ◽  
Penis Length ◽  
The Mean ◽  
Tbt Biomonitoring ◽  
Tbt Pollution

AbstractWe have monitored tributyltin (TBT) pollution in Galicia (NW Spain) for more than a decade by means of assessing gastropod imposex in populations of Nucella lapillus (N ≥ 34) and Tritia reticulata (N ≥ 18) at regular intervals. Several thousand specimens were processed to obtain their shell height (SH), penis length (PL) and vas deferens sequence (VDS); imposex indices (including the VDS index, VDSI) were subsequently calculated. The regional mean SH of both females and males has not changed significantly in either species throughout the study. This also applies to the mean male PL in N. lapillus, but male T. reticulata penises surprisingly enlarged. On the contrary, the regional mean female PL (MFPL) and all imposex indices significantly decreased in both snails. Results confirm previous conclusions based on the chemical analyses of tissues and partial imposex observations. In addition, the close correlations between MFPL and VDSI show some potential applications to TBT biomonitoring.

scholarly journals Vertical structure of currents in the vicinity of the Iceland-Scotland Ridge

2005 ◽  
Vol 23 (6) ◽  
pp. 1963-1975 ◽  
Author(s):  
C. Carollo ◽  
I. Astin ◽  
J. Graff
Keyword(s):  
General Circulation ◽  
Bottom Topography ◽  
Acoustic Doppler Current Profiler ◽  
Tidal Currents ◽  
Residual Flow ◽  
Residual Currents ◽  
Tidal Motion ◽  
Dominant Component ◽  
Current Profiler ◽  
The Mean

Abstract. An analysis of current profiles carried out on moored Acoustic Doppler Current Profiler data sets recorded during the Variability of Exchanges In the Northern Seas project is presented here for several locations in three sections in the vicinity of the Iceland-Scotland Ridge: (1) north of the Faroes, (2) in the Faroe-Bank Channel and (3) in the Faroe-Shetland Channel. Total currents have been decomposed into three components, namely the mean residual flow, tide and surge. The mean residual flow is found to be dominant. Results for the major tidal constituents (M2, S2, N2, O1 and K1) are shown and discussed. It is found that the predominant tidal harmonic M2 becomes steered through depth to align with the bottom topography. The mean residual flow is found to be generally larger than the surge, particularly in the Faroe-Bank Channel below 500m depth where it is the dominant component. Here tidal rectification, i.e. the topographic rectification of tidal currents originating in nonlinearities that rectify the oscillatory tidal motion, is identified as the process enhancing the large mean residual currents found. From the current structure, two water masses are identified in the channel: the upper slowing moving inflow water and the colder outflow water characterised by a 3–6-day periodicity. In the Faroe-Shetland Channel the flow is characterised by large tidal currents, particularly in shallow waters. Instead, north of the Faroes none of the component was identified as dominant. The results show that the variability of the current components is strongly dependent upon topography and water depth. Keywords. Oceanography: Physical (Currents; General circulation; General or miscellaneous)

scholarly journals The Biology and Trematode Parasites of the GastropodLittorina Neritoides(L.) on the Plymouth Breakwater

1941 ◽  
Vol 25 (1) ◽  
pp. 41-67 ◽  
Author(s):  
Averil M. Lysaght
Keyword(s):  
Growth Rate ◽  
Life History ◽  
Experimental Evidence ◽  
Breeding Season ◽  
Water Discharge ◽  
Downward Migration ◽  
Size Groups ◽  
The Waves ◽  
Trematode Parasites

An account is given of the distribution, life history and trematode parasites ofLittorina neritoideson the Plymouth Breakwater; a few observations from other localities are included.The smaller snails are most abundant on the exposed southern slopes of the Breakwater. Many of the larger ones live more or less permanently in water in small cylindrical pits on the top of the Breakwater. This habitat is apparently very similar to that described by Fischer-Piette (1932) as occupied permanently by this species at Cap Martin; Lebour (1935) has sometimes found it in water in other places in the Plymouth area.The conditions necessary for metamorphosis of the larvae, the need of the adults for shelter from the force of the waves, and the requirements for spawning appear to be of more importance in determining the choice of habitat than the negatively geotactic and varying phototactic responses found in this species by Fränkel (1927).The breeding season lasts from September to April. The males are ripe about two months before most of the females. Experimental evidence is given which makes it most improbable that there is any downward migration for spawning. From the examination of plankton samples it appears that there is a fortnightly spawning rhythm coincident with high tides, and that even the snails living in water discharge their eggs only at these periods.The distribution of the size groups is discussed. The proportion of males decreases significantly in the larger size groups and it is probable that there is a difference in the growth-rate of the sexes.

Swimming behavior of juvenile giant scallop, Placopecten magellanicus, in relation to size and temperature

1991 ◽  
Vol 69 (8) ◽  
pp. 2250-2254 ◽  
Author(s):  
J. L. Manuel ◽  
Michael J. Dadswell
Keyword(s):  
Water Column ◽  
Significant Relationship ◽  
Size Range ◽  
Shell Height ◽  
Swimming Behavior ◽  
The Body ◽  
Placopecten Magellanicus ◽  
Body Angle ◽  
The Mean ◽  
Increasing Temperature

Juvenile scallops (shell height 4–35 mm) were stimulated to swim in an aquarium using a whelk, and their swimming was recorded and analyzed using a videocassette recorder. Scallops ascended in the water column in straight, spiral, or twisting patterns, and the majority never swam horizontally. Two types of swimming were observed. Stable swimming, with a consistent body angle (the angle that the scallop makes with the horizon), was recorded over the size range of scallops examined. In stepwise swimming, the body angle alternated between steep (98 ± 13 (SD)) and more horizontal angles (51 ± 9°). Stepwise swimming was observed among the smaller (mean ± SD = 8 ± 3 mm) scallops. Maximum and mean velocities were positively correlated with both shell height and temperature. Clap rate (Cr) increased with increasing temperature (Cr = 0.29T (°C) + 1.3). Body angle expressed a significant relationship with shell height. Below 10 mm shell height the mean angle was 82°; between 30 and 35 mm the mean angle was 38°.

scholarly journals Intracranial Aneurysms: Does Size Really Matter?

2020 ◽  
Vol 1 (4) ◽  
Author(s):  
Kashif Majeed ◽  
Srikanth R Boddu ◽  
Joseph Carnevale ◽  
Elif Ezgi Cenberlitas ◽  
Nicholas Williams ◽  
...  
Keyword(s):  
Intracranial Aneurysms ◽  
International Study ◽  
Surgical Clipping ◽  
Aneurysmal Rupture ◽  
Ruptured Aneurysms ◽  
Unruptured Intracranial Aneurysms ◽  
Risk Of Rupture ◽  
Brainstem Stroke ◽  
Size Groups ◽  
The Mean

Abstract BACKGROUND To stratify the risk of aneurysmal rupture, size remains the primary criterion as proposed by 2 ISUIA (International Study of Unruptured Intracranial Aneurysms) trials that recommend the observation of ≤7 mm aneurysms because of their low propensity to rupture. These recommendations are controversial, given the severe outcomes following hemorrhage. OBJECTIVE To retrospectively assess whether size correlates with aneurysmal rupture, and to analyze outcomes of endovascular and microsurgical procedures. METHODS All aneurysms presenting between 2016 and 2019 were reviewed. Age, gender, comorbidities, ruptured status, modes of treatment, and their outcomes were noted. Regression analysis was performed to correlate size with rupture. The type of intervention was based on clinical and aneurysmal characteristics and the likelihood of obliteration. RESULTS Of the 668 aneurysms, 116 had ruptured. In size groups 0 to 6 mm,  7 to 12 mm,  13 to 18 mm,  18 to 24 mm, and giant, the ruptured aneurysms were 60.3%, 30.2%, 1.7%, 0.9%, and 6.9%, respectively. The majority (423) were managed endovascularly, of which 84 (19.9%) were ruptured. A total of 97 (14.5%) underwent clipping, of which 31 were ruptured. The mean modified Rankin Scale for both treated groups was zero. One death in each group and a single brainstem stroke in the coiled group were noted. A total of 139 were followed, of which none had ruptured. The mean modified Raymond-Roy classification for endovascular therapy was 1.1, with 380 completely occluded; 15 had a score of 2, and 28 of score 3. CONCLUSION The ruptured aneurysms were mostly smaller than reported previously. Surgical clipping was at equipoise with endovascular treatments. Further studies to correlate aneurysmal characteristics to the risk of rupture are needed.

Growth of Juvenile Chum Salmon (Oncorhynchus keta) Under Different Feeding Regimes

1969 ◽  
Vol 26 (6) ◽  
pp. 1631-1645 ◽  
Author(s):  
R. J. LeBrasseur
Keyword(s):  
Growth Rate ◽  
Chum Salmon ◽  
Oncorhynchus Keta ◽  
Rate Of Growth ◽  
Total Length ◽  
Chum Salmon Oncorhynchus Keta ◽  
Feeding Regimes ◽  
Size Groups ◽  
Juvenile Chum Salmon ◽  
The Mean

Juvenile chum salmon were fed on six different concentrations of size-selected zooplankton for 8 weeks. Zooplankton were caught daily and sorted through sieves into size-groups roughly as follows: 6–20 mm total length, mainly euphausiids; 2.5–4.5 mm, mainly copepods; and ≤ 1.5 mm, mainly small copepods. The rate of growth in weight of the fish was found to be dependent upon the concentration of the ration. Fish which were offered no food lost weight, and fish which were offered excess food increased in weight by 5.4% per day. The mean growth rate of the fish held on fixed rations ranged from 2.2 to 5.7% per day and was found to be independent of the type of prey. Electivity experiments showed that all the fish selected copepods 1.6–4.5 mm long in proportion to their abundance and rejected copepods ≤ 1.5 mm. The euphausiids were selected only by fish which had previously fed on euphausiids. The effect of variations in the availability of prey is discussed.

scholarly journals DINÂMICA DA ZONA DE RASA DE SHOALING E O TRANSPORTE DE SEDIMENTOS NA DESEMBOCADURA SUL DO COMPLEXO ESTUARINO DE PARANAGUÁ – PR

2004 ◽  
Vol 54 ◽  
Author(s):  
Georgina Jacintho Martins ◽  
Eduardo Marone ◽  
Rodolfo José Angulo ◽  
Mauricio Almeida Noernberg ◽  
Clécio José Lopes De Quadros
Keyword(s):  
Complex Dynamics ◽  
Tidal Currents ◽  
Coastal Currents ◽  
Tidal Circulation ◽  
Wave Parameters ◽  
Tidal Changes ◽  
Hydrodynamic Potential ◽  
The Mean ◽  
The Waves

O presente trabalho caracteriza os parâmetros de ondas e analisa o potencial hidrodinâmico para o transporte de sedimentos por tração e de material particulado em suspensão, na costa adjacente à desembocadura sul do complexo estuarino de Paranaguá em decorrência do regime de ondas e das correntes de marés atuantes em períodos de mar calmo. A área estudada apresenta uma dinâmica complexa, devido à sua localização na saída de um grande estuário em uma costa com energia de onda relativamente elevada. Os objetivos principais foram os de caracterizar os parâmetros de ondas, avaliar o padrão de correntes junto à costa e estimar o potencial das correntes para o transporte de sedimentos. A caracterização dos parâmetros de ondas e das correntes paralelas à costa foi obtida através de correntômetro/ondômetro direcional eletromagnético InterOcean S4, fundeado imediatamente atrás da arrebentação das ondas na praia do Balneário Atami. Os fundeios foram realizados em períodos de baixa energia de ondas, quando era possível a sua instalação, sendo que os resultados são referentes a tais condições. Os resultados apontaram que a direção preferencial de chegada de ondas é de SE, sendo que a direção predominante de transporte médio longitudinal à costa foi de nordeste para sudoeste. As inversões das correntes associadas às variações da maré indicaram uma efetiva influência destas na direção do transporte. Com base nos resultados obtidos, são apresentadas sugestões visando incentivar a implementação de estratégias de monitoramento do fluxo de sedimentos costeiro. SHALLOW SHOALING ZONE DYNAMICS AND SEDIMENT TRANSPORT IN THE PARANAGUÁ BAY OUTLET Abstract This work presents a characterization of wave parameters and climate. It analyzes the hydrodynamic potential for sediments transport by traction as well by suspension (suspended particulate matter - SPM), carried out both by coastal currents, waves and the tidal circulation acting in the adjacent coast of the southern outlet of Paranaguá Estuarine Complex. This area presents a complex dynamics, due to its location, morphology and the interaction of several coastal processes acting among its limits. The main goal was to characterize the wave parameters and climate, to identify the coastal currents, and to understand the roles of these currents for the sediments transport, quantifying its magnitude. The characterization of the wave parameters and of the coastal currents was obtained through mooring a directional wave and current gauge InterOcean S4 immediately seaward of the surf of Atami beach, PR. The moorings were accomplished in periods of low wave energy, the only ones allowing the deployment, and the results are regarding such conditions. The results suggested that the preferential direction of wave propagation is SE and the predominant direction of the mean transport, longitudinal to the coast, was from Northeast to Southwest. The inversion of the longitudinal currents was associated to the tidal changes and they indicated an effective influence of the tidal currents, acting in the southern outlet of the Paranaguá estuary, in the direction of the mean mass transport. The hydrodynamic complexity of the place was directly related to these constraints, being linked to the net balance of the forcing of the tidal currents and the waves incidence. According to the obtained results, some suggestions were presented with the objective of suggesting strategies for the waves, currents and coastal transport studies, as a powerful tool for managing coastal zone problems.

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