Contenu archivé

L’information archivée est fournie à des fins de référence, de recherche ou de tenue de documents. Elle n’est pas assujettie aux normes Web du gouvernement du Canada et n’a pas été modifiée ou mise à jour depuis son archivage. Pour obtenir cette information dans un autre format, veuillez communiquer avec nous.

Bibliographie de l'Institut Maurice-Lamontagne

Crustacés - Euphausiacés / Meganyctiphanes norvegica / 

PLOURDE, S., G. WINKLER, P. JOLY, J.-F. ST-PIERRE, M. STARR, 2011. Long-term seasonal and interannuel variations of krill spawning in the lower St Lawrence Estuary, Canada, 1979-2009. J. Plankton Res., 33(5): 703-714.

[Résumé disponible seulement en anglais]
This study describes the long-term seasonal and interannual variations in krill spawning using abundance of krill eggs collected during an on-going long-term monitoring program at an anchor station in the lower St Lawrence Estuary from 1992 to 2009 and data collected in the same region in 1979 to 1980. The longterm seasonal semi-monthly climatology in egg abundance revealed that krill generally reproduced during two periods, i.e. in late spring (mid-May to late June) and in late summer (August to mid-September), when phytoplankton biomass in the upper 50 m was greater than 75 mg chlorophyll a m-2. The identification of krill eggs to the species level in 2007 revealed that Meganyctiphanes norvegica egg abundance was related to the biomass of phytoplankton averaged over the month prior to sampling, corresponding to the duration of one spawning cycle (two intermolt periods) known for this species. Overall krill egg abundance varied significantly between years, showing high abundance every 3–5 years with no long-term interannual trend. The annual mean egg abundance normalized for the duration of krill spawning showed the same interannual long-term pattern. Both egg abundance indices were independent of the annual phytoplankton biomass, indicating that interannual variations in krill spawning biomass would be the most likely candidate to explain interannual variability in egg abundance. We propose that such normalized annual egg abundance based on high-resolution seasonal sampling could be a useful index of interannual variations in krill spawning biomass which is otherwise difficult to sample.©2011 Oxford University Press

SIMARD, Y., M. HARVEY, 2010. Predation on Northern Krill (Meganyctiphanes norvegica Sars). Adv. Mar. Biol., 57: 277-306.

[Résumé disponible seulement en anglais]
We consider predation as a function of prey concentration with a focus on how this interaction is influenced by biological–physical interactions, and wider oceanographic processes. In particular, we examine how the anti-predation behaviour of Northern krill interacts with ocean-circulation process to influence its vulnerability to predation. We describe how three-dimensional (3D) circulation interacts with in situ light levels to modulate predator–prey interactions from small to large scales, and illustrate how the stability of the predator–prey system is sometimes perturbed as a consequence. Northern krill predators include a wide range of species from the pelagic and benthic strata, as well as birds. Many exhibit adaptations in their feeding strategy to take advantage of the dynamic physical–biological processes that determine the distribution, concentration and vulnerability of Northern krill. Among them, baleen whales appear to have developed particularly efficient predation strategies. A literature search indicates that Northern krill are a major contributor to ecosystem function throughout its distributional range, and a key species with respect to the flow of energy to upper trophic levels. A list of future research needed to fill gaps in our understanding of Northern krill predator–prey interaction is provided.©2010 Elsevier Ltd.

SIMARD, Y, M. SOURISSEAU, 2009. Diel changes in acoustic and catch estimates of krill biomass. ICES J. Mar. Sci., 66: 1318-1325.

[Résumé disponible seulement en anglais]
Krill-biomass estimates can be compromised by diel variabilities in acoustic backscatter and the catch efficiencies of various nets. This paper describes an effort to quantify these variabilities at fine temporal and spatial scales during a three-day experiment at a fixed location, using high-resolution, stratified Bioness samples and echo-integration, and assuming a fixed distribution of krill orientations. Night-time catches in the krill scattering layer (SL) were 15 times the acoustic estimates. The situation was reversed during daytime, when the acoustic estimates in the SL were 5 times larger than the catches. This collectively resulted in a ± 10–dB gradual diel cycle in the difference of vertically integrated biomass from both sampling methods. Use of a strobe light on the Bioness reduced avoidance of the net by krill and significantly increased (×10) daytime catches in the SL, but had no significant effect on night-time catches. The difference in volume-backscattering strength at 120 and 38 kHz (?Sv120 - 38) in the densest parts of the SL agreed with predictions using a target-strength (TS) model and an assumed normal distribution of tilt (mean ø = 11°; s.d. = 4°). The ?Sv120 - 38 was smaller for lower densities and during night-time. It appears that the ø and, therefore, TS distributions of krill significantly change during their diel vertical migrations. At twilight and at night, when they are feeding and swimming vertically, they exhibit lower mean TS and ?Sv120 - 38 and react less to strong strobe-light pulses, in contrast to daytime. Diel patterns in TS and net avoidance should be taken into account in krill-biomass assessments that use round the clock acoustic-survey data and multi-frequency TS models for target classification. ©2009 ICES Journal of Marine Science.

SOURISSEAU, M., Y. SIMARD, F.J. SAUCIER, 2009. Corrigendum : krill diel vertical migration fine dynamics, nocturnal overturns, and their roles for aggregation in stratified flows. Can. J. Fish. Aquat. Sci., 66: 509.

HARVEY, M., P. GALBRAITH, 2009. Macrozooplankton diel migration in the Estuary and Gulf of St. Lawrence : links to abiotic factors. AZMP Bull. PMZA, 8: 28-35.

Cliquer pour voir tout le texte

HARVEY, M., P.S. GALBRAITH, A. DESCROIX, 2009. Vertical distribution and diel migration of macrozooplankton in the St. Lawrence marine system (Canada) in relation with the cold intermediate layer thermal properties. Prog. Oceanogr., 80(1-2): 1-21.

[Résumé disponible seulement en anglais]
Vertical distribution of various species and stages of macrozooplankton (euphausiacea, chaetognatha, cnidaria, mysidacea, amphipoda) were determined for different times of the day and related to the physical environment. Stratified sampling with the BIONESS was carried out during seven cruises in spring and fall 1998, 2000, and 2001, and fall 1999, in two different habitats in the St. Lawrence marine system: the lower St. Lawrence Estuary and the NW Gulf of St. Lawrence. Our results indicate that the various macrozooplankton species were distributed throughout the whole water column including the surface layer, the cold intermediate layer (CIL), and the deep layer at different times of day and night in both areas during all periods. Moreover, three types of migrational patterns were observed within this zooplanktonic community: (1) nocturnal ascent by the whole population, (2) segregation into two groups; one which performed nocturnal accent and another which remained in the deep, and (3) no detectable migration. We also observed that the diel vertical migration (DVM) amplitude in most of the macrozooplankton species varied as a function of physical factors, in particular the spatio-temporal variations of the CIL thermal properties, including the upper and the lower limits of the CIL and the depth of the CIL core temperature. Finally, the different DVM patterns coupled with estuarine circulation patterns and bottom topography could place animals in different flow regimes by night and by day and contribute to their retention (aggregation) and/or dispersion in different areas, time of the day, and seasons. Crown Copyright ©2008 Published by Elsevier Ltd.

SOURISSEAU, M., Y. SIMARD, F. J. SAUCIER, 2008. Krill diel vertical migration fine dynamics, nocturnal overturns, and their roles for aggregation in stratified flows. Can. J. Fish. Aquat. Sci., 65: 574-587.

Un ensemble d’observations à haute résolution de la dynamique à court terme des migrations verticales nycthémérales (MVN) du krill dans l’estuaire du Saint-Laurent est présenté. Il incorpore des mesures de transfert de masse sur la verticale à partir d’échosondages multifréquences couplés à l’échantillonnage des strates au filet à nappe et le suivi des mouvements verticaux individuels par des mesures de pigments stomacaux sur une période de 72 h. Des séries temporelles des patrons circadiens des vitesses verticales de migrations déterminées à l’aide d’un ADCP (« acoustic Doppler current profiler »; profileur de courant acoustique à effet Doppler) complètent les mésures sur une période allant jusqu’à 3 mois. L’ensemble du krill migre toujours rapidement et en synchronie jusqu’en surface lors du coucher du soleil. Peu de temps après l’ascension, du krill nourri commence à nager vers le bas, ce qui se poursuit avec une intensité notable jusqu’au milieu de la nuit. Il forme alors une couche acoustique de rétrodiffusion à sa profondeur diurne, ce qui engendre une distribution verticale nocturne bimodale, souvent accompagnée de densités acoustiques notables aux profondeurs intermédiaires, particulièrement au milieu de la nuit. Une réorganisation dans la partie supérieure de la colonne d’eau survient ensuite, vraisemblablement pour une dernière période d’alimentation avant l’aube. A l’aube, la masse de krill s’alimentant toujours dans la partie supérieure de la colonne d’eau nage en synchronie vers sa profondeur diurne. Ce comportement vertical nocturne asynchrone, conforme à l’hypothèse de faim-satiété de la MVN, s’est répété entre les mois d’août et d’octobre à deux années différentes, la synchronisation de la MVN dépendant de la durée du jour.©2008 NRC Canada

DESCROIX, A., M. HARVEY, S. ROY, P.S. GALBRAITH, 2005. Macrozooplankton community patterns driven by water circulation in the St. Lawrence marine system, Canada. Mar. Ecol. Prog. Ser., 302: 103-119 .

[Résumé disponible seulement en anglais]
Six cruises were carried out in the lower St. Lawrence Estuary (LSLE) and the NW Gulf of St. Lawrence (NW GSL) in spring and fall 1998, 2000, and 2001 to study the species composition, abundance, and distribution of macrozooplankton in relation to the physical environment. Our results confirm that the LSLE and the NW GSL represent 2 different physical environments. These differences are likely due to different circulation patterns observed between the 2 regions: the estuarine circulation in the LSLE and a quasi-permanent cyclonic gyre in the NW GSL. The dominant species found in both environments (LSLE and NW GSL) is the mysid Boreomysis arctica, but we observed no significant regional and interannual variations in its abundance. In contrast, 2 distinct groups characterized the LSLE and the NW GSL when we examined the other macrozooplankton groups. Two euphausiid species, Meganyctiphanes norvegica and Thysanoessa raschii, dominated in the LSLE. Their abundances were 6 and 15 times higher in the LSLE than in the NW GSL, respectively. On the other hand, the NW GSL was dominated by chaetognaths, hyperiid amphipods, and siphonophores. These groups were twice as abundant in the NW GSL as in the LSLE. Such interregional variations were attributed to different circulation patterns and different trophic systems. Furthermore, important interannual variations in the abundance of the major macrozooplankton species were also observed between 1998 and 2001 in the LSLE and the NW GSL. In the NW GSL, the arctic and boreo-arctic species were more abundant in 1998 than in 2000 and 2001. In contrast, their abundance was lowest in 1998, and highest in 2000 and 2001 in the LSLE. We hypothesize that stronger inflow of Labrador Shelf waters in the GSL via the Strait of Belle Isle may increase the advection of macrozooplankton into the LSLE.©2005 Inter-Research