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Torkel Gissel Nielsen - One of the best experts on this subject based on the ideXlab platform.
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reconciling behavioural bioenergetic and oceanographic views of bowhead whale predation on overwintering copepods at an arctic hotspot disko bay greenland
Frontiers in Marine Science, 2021Co-Authors: Neil S Banas, Kristin L Laidre, Eva Friis Moller, Malene Simon, Ingrid Ellingsen, Torkel Gissel NielsenAbstract:Bowhead whales (\textit{Balaena mysticetus}) visit Disko Bay, West Greenland in winter and early spring to feed on \textit{Calanus} spp., at a time of year when the copepods are still mostly in diapause and concentrated in near-bottom patches. Combining past observations of copepod abundance and distribution with detailed observations of bowhead whale foraging behaviour from telemetry suggests that if the whales target the highest-density patches, they likely consume 26--75\% of the \textit{Calanus} standing stock annually. A parallel bioenergetic calculation further suggests that the whales’ patch selection must be close to optimally efficient at finding hotspots of high density copepods near the sea floor in order for foraging in Disko Bay to be a net energetic gain. Annual \textit{Calanus} consumption by bowhead whales is similar to median estimates of consumption by each of three zooplankton taxa (jellies, chaetognaths, and predatory copepods), and much greater than the median estimate of consumption by fish larvae, as derived from seasonal abundance and specific ingestion rates from the literature. The copepods’ self-concentration during diapause, far from providing a refuge from predation, is the behaviour that makes this strong trophic link possible. Because the grazing impact of the whales comes 6--10 months later than the annual peak in primary production, and because Disko Bay sits at the end of rapid advective pathways (here delineated by a simple numerical particle-tracking experiment), it is likely that these \textit{Calanus} populations act in part as a long-distance energetic bridge between the whales and primary production hundreds or thousands of km away.
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genome and transcriptome assisted development of nuclear insertion deletion markers for Calanus species copepoda calanoida identification
Molecular Ecology Resources, 2014Co-Authors: Irina Smolina, Torkel Gissel Nielsen, Eva Friis Moller, Spyros Kollias, Marloes Poortvliet, Penelope K Lindeque, Claudia Castellani, Leocadio Blancobercial, Galice HoarauAbstract:Copepods of the genus Calanus are key zooplankton species in temperate to arctic marine ecosystems. Despite their ecological importance, species identification remains challenging. Furthermore, the recent report of hybrids among Calanus species highlights the need for diagnostic nuclear markers to efficiently identify parental species and hybrids. Using next-generation sequencing analysis of both the genome and transcriptome from two sibling species, Calanus finmarchicus and Calanus glacialis, we developed a panel of 12 nuclear insertion/deletion markers. All the markers showed species-specific amplicon length. Furthermore, most of the markers were successfully amplified in other Calanus species, allowing the molecular identification of Calanus helgolandicus, Calanus hyperboreus and Calanus marshallae.
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the effect of changes in temperature and food on the development of Calanus finmarchicus and Calanus helgolandicus populations
Limnology and Oceanography, 2012Co-Authors: Eva Friis Moller, Torkel Gissel Nielsen, Marie Maar, Sigrun Jonasdottir, Kajsa TonnessonAbstract:We studied the response in development times of Calanus finmarchicus and Calanus helgolandicus to changes in temperature and food conditions. Grazing experiments were performed at different temperatures for both species, and the results were implemented in a stage-resolved zooplankton population model that predicted development times from biomass increments controlled by ingestion and metabolic losses. Predictions were validated against development data from the literature, and show that C. finmarchicus develops faster than C. helgolandicus below 11uC and slower above. The different relative development rates of the species are related to different temperature responses in ingestion rates. A temperature increase of 1u Ct o 2uC may have consequences for the relative contribution of C. helgolandicus and C. finmarchicus to the copepod community, and both seasonal and spatial displacements of the Calanus populations can be expected under climate change. Copepods of the genus Calanus are key species in the North Atlantic Ocean. They are central for the trophodynamics of the system, and a change in abundance is likely to influence food web dynamics, energy transfer efficiency, and the biological carbon pump (Hirche and Kosobokova 2007; Beaugrand 2009; Falk-Petersen et al. 2009). Calanus has been shown to be a crucial prey for fish species such as cod (Gadus morhua), haddock (Melanogrammus aeglefinus), herring (Clupea harengus), and mackerel (Scomber scombrus) (Gaard and Reinert 2002; Gislason and Astthorsson 2002; Ringuette et al. 2002), as well as for marine birds and marine mammals (Laidre et al. 2007; Karnovsky et al. 2003). Four Calanus species exist in the North Atlantic. Calanus glacialis and Calanus hyberboreus dominate in Arctic waters, while Calanus finmarchicus has its center in the North Atlantic and Calanus helgolandicus prevails farther south (Beaugrand et al. 2002; Bonnet et al. 2005; Falk-Petersen et al. 2009). Here we consider the latter two species, their responses in feeding and development time to changing temperature and food conditions, and how this may affect the competition between them. In the North Atlantic, occurrence of cod has been shown to be associated with high abundances of C. finmarchicus (Beaugrand and Kirby 2010). In the North Sea, a shift in the spatial distribution of C. finmarchicus and C. helgolandicus is
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effects of pyrene on grazing and reproduction of Calanus finmarchicus and Calanus glacialis from disko bay west greenland
Aquatic Toxicology, 2008Co-Authors: Maj Holst Jensen, Torkel Gissel Nielsen, Ingela DahllofAbstract:The effects of pyrene on grazing and egg production of the ecologically important arctic copepods Calanus finmarchicus and Calanus glacialis were studied in the Disko Bay, Western Greenland. The effects of both passive uptake of pyrene by diffusion through membranes, and active uptake through ingestion of contaminated food were investigated for both species. Furthermore, the hatching success for eggs from exposed females and for eggs directly exposed to pyrene was also studied. There was no reduction in egg production in starved Calanus spp., which indicates that the uptake of pyrene through passive diffusion was limited. A significant reduction was observed in grazing and egg production for feeding C. finmarchicus exposed to the highest concentration of 100 nM pyrene within the experimental period. Furthermore, the time-dependent development in grazing and egg production was reduced for both species exposed to 100 nM, and we suggest that the effect of pyrene on these endpoints would increase with time. The observed difference in response time between the two species can be attributed to the differences in the amount of storage lipid and in their reproductive strategies. There was a lower hatching percentage for eggs from C. finmarchicus females exposed to 10 nM pyrene, whereas the egg hatching percentage was not reduced for eggs exposed directly.
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production of doc by Calanus finmarchicus c glacialis and c hyperboreus through sloppy feeding and leakage from fecal pellets
Marine Ecology Progress Series, 2003Co-Authors: Eva Friis Moller, Peter Thor, Torkel Gissel NielsenAbstract:Using 14 C-labeled phytoplankton as tracer, we investigated 2 mechanisms of immediate dissolved organic carbon (DOC) release during grazing activity of Calanus spp. — sloppy feeding and leakage from newly expelled fecal pellets. Half of the carbon cleared by Calanus spp. was released as DOC through sloppy feeding. Freshly expelled fecal pellets lost more than 20% of their carbon content within the first hour, corresponding to 6% of the carbon cleared. Thus, copepods should not only be considered as an essential link to higher trophic levels, but also as a feedback link to the microbial food web.
Stig Falkpetersen - One of the best experts on this subject based on the ideXlab platform.
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non consumptive mortality in copepods occurrence of Calanus spp carcasses in the arctic ocean during winter
Journal of Plankton Research, 2014Co-Authors: Malin Daase, Stig Falkpetersen, Oystein VarpeAbstract:During a research cruise to the Arctic Ocean in January 2012, we observed high occurrence of carcasses of Calanus spp. We analysed live samples to separate living from dead individuals. In Rijpfjorden, an Arctic fjord in north-eastern Svalbard, 9–14% of the Calanus population were observed to be dead. At Sofiadjupet, an oceanic basin located at 81.4N at the southern edge of the Arctic Ocean, 94% of the Calanus at depth (between 300 and 2000 m) were dead. This is the first estimation of the contribution of carcasses to high Arctic copepod populations. Lipid sacs were preserved in part of the observed carcasses and the lipid sac area was significantly smaller in dead Calanus than in living individuals. We discuss possible causes for the observed mortality, its implication for population dynamics and energy transfer and review previous accounts of non-predatory mortality of marine copepods. In our case, partial consumption by predators and death after reproduction are unlikely causes of mortality, thus other stressors (starvation, environmental conditions, parasitic or viral infection) may be responsible. Our analysis shows that we have a poor understanding of factors other than predation causing mortality in copepod populations.
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timing of reproductive events in the marine copepod Calanus glacialis a pan arctic perspective
Canadian Journal of Fisheries and Aquatic Sciences, 2013Co-Authors: Malin Daase, Stig Falkpetersen, Oystein Varpe, Anette Wold, Gerald Darnis, Janne E Soreide, Eva LeuAbstract:The timing of reproductive events of Calanus glacialis is closely coupled to the two major marine primary production events in the Arctic: the ice algal and phytoplankton blooms. Reproductive strat...
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lipids and life strategy of arctic Calanus
Marine Biology Research, 2009Co-Authors: Stig Falkpetersen, Patrick Mayzaud, Gerhard Kattner, John R SargentAbstract:Abstract The three Arctic Calanus species, C. finmarchicus (Gunnerus, 1765), C. glacialis (Jaschov, 1955), and C. hyperboreus, are the most important herbivores in Arctic seas in terms of species biomass. They play a key role in the lipid-based energy flux in the Arctic, converting low-energy carbohydrates and proteins in ice algae and phytoplankton into high-energy wax esters. In this paper we review the over-wintering strategy, seasonal migration, stage development, life span, feeding strategy, body size, lipid biochemistry and the geographic distribution of the three dominant Calanus species in Arctic waters. We then relate these parameters to other biotic and abiotic factors, such as the timing of the Arctic phytoplankton and ice algae bloom, sea ice cover and climate variability. We also present new data on fatty acid and fatty alcohol content in the three Calanus species in addition to reviewing the available literature on these topics. These data are analysed for species homogeneity and geographic ...
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trophic interactions of the pelagic ecosystem over the reykjanes ridge as evaluated by fatty acid and stable isotope analyses
Deep-sea Research Part Ii-topical Studies in Oceanography, 2008Co-Authors: Hildur Petursdottir, Astthor Gislason, Stig Falkpetersen, Jorundur SvavarssonAbstract:Abstract Trophic relationships of the important oceanic crustacean species Calanus finmarchicus, Meganyctiphanes norvegica and Sergestes arcticus, as well as the mesopelagic fishes Maurolicus muelleri, Benthosema glaciale and Sebastes mentella, were investigated over the Reykjanes Ridge in June 2003 and in June 2004. Measurements were performed of length, wet weight, dry weight, total lipid, lipid class, fatty acid and fatty alcohol profiles and stable isotopes (δ13C and δ15N). High amounts of the Calanus lipid markers, 20:1(n-9) and 22:1(n-11) in these species confirm the importance of Calanus spp. in this ecosystem. Comparisons of fatty acid/alcohol profiles by multivariate analysis revealed two main trophic pathways over the Reykjanes Ridge. In one pathway, Calanus spp. was an important part of the diet for the small mesopelagic fish species M. muelleri and B. glaciale and the shrimp S. arcticus, whereas in the other pathway, the euphausiid M. norvegica was the dominant food for the redfish S. mentella, and Calanus spp. were of less importance. M. muelleri and the smaller B. glaciale feed on C. finmarchicus, whereas the larger B. glaciale and S. arcticus select the larger, deeper-living C. hyperboreus. All investigated species are true pelagic species except for the shrimp S. arcticus, which seems to have a benthic feeding habit as well. The δ15N levels show that of the species investigated, C. finmarchicus occupies the lowest trophic level (2.0) and the redfish, S. mentella, the highest (4.2). All the species were lipid rich, typical for subarctic pelagic ecosystem. Calanus finmarchicus, S. arcticus and B. glaciale store wax esters as their lipid stores, while M. norvegica, M. muelleri and S. mentella store triacylglycerols.
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distribution of Calanus species in kongsfjorden a glacial fjord in svalbard
Journal of Plankton Research, 2003Co-Authors: Slawek Kwasniewski, Stig Falkpetersen, Haakon Hop, Gunnar PedersenAbstract:The distribution of Calanus species was investigated in Kongsfjorden in summer of 1996 and 1997. In both years Calanus finmarchicus and Calanus glacialis dominated, although the boreal C. finmarchicus was more abundant than the Arctic C. glacialis in 1997. This coincided with a 2°C higher water temperature at 50 m in 1997, indicating stronger influence of Atlantic origin water that year. Adverted Calanus finmarchicus occurred in deep and subsurface layers of the outer fjord in 1996 (200 ind. m 3 , mainly CIII). A less abundant local population aggregated in surface layers of the inner fjord (100 ind. m -3 ). Similarly, advected C. finmarchicus occurred in subsurface layers in 1997 (446 ind. m -3 , mainly CIII and CIV) and a local population in surface layers (183 ind. m -3 , mainly CI). Calanus glacialis in 1996 aggregated as CII and CIII in the deep layers of the outer ford (272 ind. m 3 ), whereas CIII-CV were abundant (216 ind. m -3 ) in cold surface waters of the inner fjord. In 1997 C. glacialis (mostly CIIII-CV) was more abundant in the outer than in the inner part of the fjord (40 and 192 ind. m -3 , respectively). Within Kongsfjorden, Calanus finmarchicus needs one year to complete its life cycle, whereas Calanus glacialis needs two. Calanus hyper-boreus seems to be an expatriate in the fjord system.
Eva Friis Moller - One of the best experts on this subject based on the ideXlab platform.
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reconciling behavioural bioenergetic and oceanographic views of bowhead whale predation on overwintering copepods at an arctic hotspot disko bay greenland
Frontiers in Marine Science, 2021Co-Authors: Neil S Banas, Kristin L Laidre, Eva Friis Moller, Malene Simon, Ingrid Ellingsen, Torkel Gissel NielsenAbstract:Bowhead whales (\textit{Balaena mysticetus}) visit Disko Bay, West Greenland in winter and early spring to feed on \textit{Calanus} spp., at a time of year when the copepods are still mostly in diapause and concentrated in near-bottom patches. Combining past observations of copepod abundance and distribution with detailed observations of bowhead whale foraging behaviour from telemetry suggests that if the whales target the highest-density patches, they likely consume 26--75\% of the \textit{Calanus} standing stock annually. A parallel bioenergetic calculation further suggests that the whales’ patch selection must be close to optimally efficient at finding hotspots of high density copepods near the sea floor in order for foraging in Disko Bay to be a net energetic gain. Annual \textit{Calanus} consumption by bowhead whales is similar to median estimates of consumption by each of three zooplankton taxa (jellies, chaetognaths, and predatory copepods), and much greater than the median estimate of consumption by fish larvae, as derived from seasonal abundance and specific ingestion rates from the literature. The copepods’ self-concentration during diapause, far from providing a refuge from predation, is the behaviour that makes this strong trophic link possible. Because the grazing impact of the whales comes 6--10 months later than the annual peak in primary production, and because Disko Bay sits at the end of rapid advective pathways (here delineated by a simple numerical particle-tracking experiment), it is likely that these \textit{Calanus} populations act in part as a long-distance energetic bridge between the whales and primary production hundreds or thousands of km away.
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genome and transcriptome assisted development of nuclear insertion deletion markers for Calanus species copepoda calanoida identification
Molecular Ecology Resources, 2014Co-Authors: Irina Smolina, Torkel Gissel Nielsen, Eva Friis Moller, Spyros Kollias, Marloes Poortvliet, Penelope K Lindeque, Claudia Castellani, Leocadio Blancobercial, Galice HoarauAbstract:Copepods of the genus Calanus are key zooplankton species in temperate to arctic marine ecosystems. Despite their ecological importance, species identification remains challenging. Furthermore, the recent report of hybrids among Calanus species highlights the need for diagnostic nuclear markers to efficiently identify parental species and hybrids. Using next-generation sequencing analysis of both the genome and transcriptome from two sibling species, Calanus finmarchicus and Calanus glacialis, we developed a panel of 12 nuclear insertion/deletion markers. All the markers showed species-specific amplicon length. Furthermore, most of the markers were successfully amplified in other Calanus species, allowing the molecular identification of Calanus helgolandicus, Calanus hyperboreus and Calanus marshallae.
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the effect of changes in temperature and food on the development of Calanus finmarchicus and Calanus helgolandicus populations
Limnology and Oceanography, 2012Co-Authors: Eva Friis Moller, Torkel Gissel Nielsen, Marie Maar, Sigrun Jonasdottir, Kajsa TonnessonAbstract:We studied the response in development times of Calanus finmarchicus and Calanus helgolandicus to changes in temperature and food conditions. Grazing experiments were performed at different temperatures for both species, and the results were implemented in a stage-resolved zooplankton population model that predicted development times from biomass increments controlled by ingestion and metabolic losses. Predictions were validated against development data from the literature, and show that C. finmarchicus develops faster than C. helgolandicus below 11uC and slower above. The different relative development rates of the species are related to different temperature responses in ingestion rates. A temperature increase of 1u Ct o 2uC may have consequences for the relative contribution of C. helgolandicus and C. finmarchicus to the copepod community, and both seasonal and spatial displacements of the Calanus populations can be expected under climate change. Copepods of the genus Calanus are key species in the North Atlantic Ocean. They are central for the trophodynamics of the system, and a change in abundance is likely to influence food web dynamics, energy transfer efficiency, and the biological carbon pump (Hirche and Kosobokova 2007; Beaugrand 2009; Falk-Petersen et al. 2009). Calanus has been shown to be a crucial prey for fish species such as cod (Gadus morhua), haddock (Melanogrammus aeglefinus), herring (Clupea harengus), and mackerel (Scomber scombrus) (Gaard and Reinert 2002; Gislason and Astthorsson 2002; Ringuette et al. 2002), as well as for marine birds and marine mammals (Laidre et al. 2007; Karnovsky et al. 2003). Four Calanus species exist in the North Atlantic. Calanus glacialis and Calanus hyberboreus dominate in Arctic waters, while Calanus finmarchicus has its center in the North Atlantic and Calanus helgolandicus prevails farther south (Beaugrand et al. 2002; Bonnet et al. 2005; Falk-Petersen et al. 2009). Here we consider the latter two species, their responses in feeding and development time to changing temperature and food conditions, and how this may affect the competition between them. In the North Atlantic, occurrence of cod has been shown to be associated with high abundances of C. finmarchicus (Beaugrand and Kirby 2010). In the North Sea, a shift in the spatial distribution of C. finmarchicus and C. helgolandicus is
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production of doc by Calanus finmarchicus c glacialis and c hyperboreus through sloppy feeding and leakage from fecal pellets
Marine Ecology Progress Series, 2003Co-Authors: Eva Friis Moller, Peter Thor, Torkel Gissel NielsenAbstract:Using 14 C-labeled phytoplankton as tracer, we investigated 2 mechanisms of immediate dissolved organic carbon (DOC) release during grazing activity of Calanus spp. — sloppy feeding and leakage from newly expelled fecal pellets. Half of the carbon cleared by Calanus spp. was released as DOC through sloppy feeding. Freshly expelled fecal pellets lost more than 20% of their carbon content within the first hour, corresponding to 6% of the carbon cleared. Thus, copepods should not only be considered as an essential link to higher trophic levels, but also as a feedback link to the microbial food web.
Malin Daase - One of the best experts on this subject based on the ideXlab platform.
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non consumptive mortality in copepods occurrence of Calanus spp carcasses in the arctic ocean during winter
Journal of Plankton Research, 2014Co-Authors: Malin Daase, Stig Falkpetersen, Oystein VarpeAbstract:During a research cruise to the Arctic Ocean in January 2012, we observed high occurrence of carcasses of Calanus spp. We analysed live samples to separate living from dead individuals. In Rijpfjorden, an Arctic fjord in north-eastern Svalbard, 9–14% of the Calanus population were observed to be dead. At Sofiadjupet, an oceanic basin located at 81.4N at the southern edge of the Arctic Ocean, 94% of the Calanus at depth (between 300 and 2000 m) were dead. This is the first estimation of the contribution of carcasses to high Arctic copepod populations. Lipid sacs were preserved in part of the observed carcasses and the lipid sac area was significantly smaller in dead Calanus than in living individuals. We discuss possible causes for the observed mortality, its implication for population dynamics and energy transfer and review previous accounts of non-predatory mortality of marine copepods. In our case, partial consumption by predators and death after reproduction are unlikely causes of mortality, thus other stressors (starvation, environmental conditions, parasitic or viral infection) may be responsible. Our analysis shows that we have a poor understanding of factors other than predation causing mortality in copepod populations.
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timing of reproductive events in the marine copepod Calanus glacialis a pan arctic perspective
Canadian Journal of Fisheries and Aquatic Sciences, 2013Co-Authors: Malin Daase, Stig Falkpetersen, Oystein Varpe, Anette Wold, Gerald Darnis, Janne E Soreide, Eva LeuAbstract:The timing of reproductive events of Calanus glacialis is closely coupled to the two major marine primary production events in the Arctic: the ice algal and phytoplankton blooms. Reproductive strat...
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Seasonal and diel vertical migration of zooplankton in the High Arctic during the autumn midnight sun of 2008
Marine Biodiversity, 2011Co-Authors: Ananda Rabindranath, Malin Daase, Stig Falk-petersen, Anette Wold, Margaret I. Wallace, Jørgen Berge, Andrew S. BrierleyAbstract:The diel vertical migration (DVM) of Calanus ( Calanus finmarchicus , Calanus glacialis and Calanus hyperboreus ) and Metridia longa was investigated in August 2008 at six locations to the north and northwest of Svalbard (Rijpfjorden, Ice, Marginal Ice Zone, Shelf break, Shelf and Kongsfjorden). Despite midnight sun conditions, a diel light cycle was clearly observed at all stations. We collected data on zooplankton vertical distribution using a Multi Plankton Sampler (200-μm mesh size) and an EK60 echosounder system (38, 120 and 200 kHz). These were supplemented by environmental data collected using a standard conductivity, temperature and depth (CTD) profiler. The sea ice had recently opened in Rijpfjorden, Ice and Shelf stations, and these stations exhibited phytoplankton bloom conditions with pronounced fluorescence maxima at approximately 30 m. In contrast, Kongsfjorden was more representative of autumn conditions, with the Arctic bloom having culminated 2–3 months prior to sampling. All three Calanus species were found shallower than 50 m on average at Rijpfjorden and the Ice station, while C. glacialis and C. hyperboreus were found deeper than 200 m on average at Kongsfjorden. Shallow water DVM behaviour (5,000 individuals/m^3). A bimodal depth distribution was observed among C. finmarchicus at the Shelf break station, with CI-CIII copepodites dominating at depths shallower than 100 m and CIV-adult stages dominating at depths exceeding 600 m. Statistical analyses revealed significant differences between the day and night 200-kHz data, particularly at specified depth strata (25–50 m) where backscatter intensity was higher during the day, especially in Rijpfjorden and at the Ice station. We conclude that DVM signals exist in the Arctic during late summer/autumn, when a need to feed and an abundant food source exists, and these signals are primarily due to mesozooplankton.
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dynamics of coexisting Calanus finmarchicus Calanus glacialis and Calanus hyperboreus populations in a high arctic fjord
Polar Biology, 2005Co-Authors: Gyda Arnkvaern, Malin Daase, Ketil EianeAbstract:We studied the population dynamics of Calanus finmarchicus, Calanus glacialis and Calanus hyperboreus in Billefjorden, Svalbard (78°40′N). All three species reproduced in the fjord with different timing. The maximum abundance of Calanus spp. copepodite stages peaked on the 11th of July (29,000 ind m−2). C. glacialis was the dominant species accounting for 60–80% of the total Calanus abundance. C. finmarchicus appear to thrive in the fjord despite the low temperatures (−1.86°C to 5°C) and accounted for 20–30% of the total population. C. hyperboreus contributed less to the total abundance (5–20%). A 1-year life cycle is suggested for C. finmarchicus and C. hyperboreus in the fjord, C. glacialis has a 1- to 2-year life cycle. Highest mortality rates were observed for copepodite stage CV in C. finmarchicus and C. glacialis (0.09 and 0.075 d−1, respectively) and for females in C. hyperboreus (0.149 d−1). Mortality of copepodite stages was substantially lower in C. glacialis than in the other species. This is particularly obvious in the early and numerous copepodite stages (CI + CII) during the period of recruitment to these stages. This suggests that differences in secondary production in Arctic pelagic ecosystems are controlled partly by population loss rates.
Peter C F Hurley - One of the best experts on this subject based on the ideXlab platform.
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distribution of early stage atlantic cod gadus morhua haddock melanogrammus aeglefinus and witch flounder glyptocephalus cynoglossus eggs on the scotian shelf a reappraisal of evidence on the coupling of cod spawning and plankton production
Canadian Journal of Fisheries and Aquatic Sciences, 1992Co-Authors: Keith Brander, Peter C F HurleyAbstract:In spring, Atlantic cod (Gadus morhua) spawned progressively later from southwest to northeast along the Scotian Shelf and matched the variation in peak abundance of Calanus finmarchicus. In fall, cod spawned in some, but not all, areas where Calanus were abundant. This is consistent with the hypothesis that cod spawning is coupled to copepod production, which is a part of the "match–mismatch" hypothesis proposed by D. H. Cushing. The timing of spawning was estimated from the distributions of early- and late-stage eggs of cod, haddock (Melanogrammus aeglefinus), and witch flounder (Glyptocephalus cynoglossus) collected during Scotian Shelf Ichthyoplankton Survey (SSIP) cruises in 1979–81.