Similar to other balaenopterids, the fin whale feeds intensively in summer, when an adult whale is estimated to consume up to 1 ton of euphausiids per day, and largely fasts in winter (see later). To demonstrate the stochastic death model defined above, an example is provided for the boreal marine copepod Calanus finmarchicus exposed to mercury (Øverjordet et al., 2014). (Permission from Huys and Boxshall, 1991. Calanoid copepods of the genus Calanus play a key role in marine food webs of the northern hemisphere as primary consumers and main source of food for many predators (Falk‐Petersen et al. These examples show how the application of the AARS method simplifies large-scale monitoring of zooplankton in the field, not only at the surface but also in deep waters. Harpacticoid copepods are predominantly marine, with only 10% of species being freshwater. results from a coupled biological−physical model of Calanus finmarchicus(the primary prey of right whales), satellite-derived sea surface temperature and chlorophyll, and bathymetry. Alex Aguilar, Raquel García-Vernet, in Encyclopedia of Marine Mammals (Third Edition), 2018. On the other hand, population persistence requiring active behavior on the part of the retained organisms does occur. [12] Both egg production and ATP composition were previously thought to have varied directly with food availability on a linear scale. [2], Adults reproduce almost exclusively in surface waters. "Functional genomics resources for the North Atlantic copepod, Comparative Biochemistry and Physiology D, http://www.scotland.gov.uk/Uploads/Documents/ME02Zooplankton.pdf, https://en.wikipedia.org/w/index.php?title=Calanus_finmarchicus&oldid=937872029, Articles with dead external links from October 2019, Articles with permanently dead external links, Creative Commons Attribution-ShareAlike License, This page was last edited on 27 January 2020, at 19:04. Distribution of Calanus finmarchicus and C. helgolandicus recorded in CPR samples from 1958 to 1994. Data from the literature document successful overwintering at depths ranging from about 2000 m to near the surface, and temperatures ranging from -1 to +11°C. Background. In its place a temperate species called Calanus finmarchicus has appeared, but it contains much less fat and that is of poorer quality. In August–September, adults of the two species were equally numerous in the 0–50 m depth range. and contamination of samples with the congener Calanus helgolandicus is highly unlikely due to its limited tolerance of low salinities (Hill 2009). The fin whale feeds on a wide variety of organisms, depending on availability (Kawamura, 1980; Fig. 2014). Distribution and habitat In the northern Atlantic, Calanus marshallae has been recorded from Spitsbergen , Saint Lawrence Island , the Chukchi Sea , the Bering Sea , the coasts of Greenland , the Beaufort Sea , Banks Island and the Aleutian Islands . In certain calanoid copepods such as Candacia armata, there is a unique presence of dimorphic spermatozoa inside the spermatophore (Heberer, 1932). During the last ice age (approx. comm.) Copyright © 2020 Elsevier B.V. or its licensors or contributors. K.S. The copepod Calanus finmarchicus dominates zooplankton biomass in the North Atlantic Ocean and adjacent seas, is a key food web component and the main prey for several pelagic fish and early life stages of demersal fish, and probably among the world’s most well‐studied zooplankton species (reviewed in Melle et al. Abstract. If we examine more typical situations, we find that simple gyral retention becomes a very incomplete explanation of how populations persist. Benthic substrate types are generally correlated with seafloor communities and constitute important geologic habitat components. In the absence of this rich population structure, passive dispersal would result in the encounter rate between individuals becoming too low for sexual reproduction to occur. In copepods, the spermatophore is an alternative to an intromittent organ inasmuch as it delivers the male gametes directly into the female opening. The resulting likelihood function was maximized to find the best-fitting parameter values. Habitat Endemic to arctic waters Most abundant on shelf areas deeper than 50 m, commonly advected off shelves into deep basins Concentrated in surface waters during late spring to early fall, found between 200 … In the cold limb of the Subarctic Gyre, Calanus glacialis and Metridia longa have their centers of distribution, while the warm limb is the habitat of C. helgolandicus and M. lucens. The North Atlantic Ocean as habitat for Calanus finmarchicus: Environmental factors and life history traits and Calanoides carinatus of upwelling regions persist by migrating down to the slower and even contrary flow below the newly formed pycnocline at the end of each upwelling event, thus avoiding longshore and offshore transport. Copepods and krill are often found as sound-scattering layers (SSLs) in the basin water of the fiord, and are heavily preyed upon both by demersal and pelagic fish. Parameter estimates are provided in Table 3.3. With the admission of water, during spermatophore transfer, the Q-sperm swell up and develop a strong pressure inside, causing expulsion of the functional B-sperm. 2007).In the North Atlantic and the Arctic Ocean, four species prevail: the boreal species Calanus helgolandicus, the boreal‐arctic Calanus finmarchicus … Preferred prey in the Northern Hemisphere seems to be krill composed of the euphausiid Meganyctiphanes norvegica, although other species of planktonic crustaceans (Thysanoessa inermis, Calanus finmarchicus), schooling fishes such as capelin (Mallotus villosus), herring (Clupea harengus), mackerel (Scomber scombrus), and blue whiting (Micromesistius poutassou), and even small squids are consumed. A pilot study” Background There are a number of indications that supplement with marine oils have positive health effects. The Cyclopoida include pelagic commensal and parasitic species (Figure 3). Larvae and juveniles from these species feed on Calanus finmarchicus during early life stages. During the long overwintering period a marked decrease in organic lipid-based reserves takes place in both copepods and krill, accounting for 40–70% of that present at the end of the primary production season. However, we need to realize the nature of the data. Studies in rats have shown that supplementation with oil from Calanus finmarchicus, In the same way, the AARS method allowed the broad-scale characterization of zooplankton production in Antarctic, Mediterranean, Indian and Pacific waters (Table 6). The mean abundance for locations with water depth >500 m was ∼37000 ind. To the extent that flow-fields of ocean currents are laminar, then purposive activity on the part of the organisms must be invoked to explain their persistence. Figure 3. [4], Mesozooplankton are among the most important components of their regional food web. Gunnerus’ sketches of Calanus. Later, subsequent to calibration in the laboratory, the AARS method was applied to monitor the growth of Calanus helgolandicus late developmental stages in the English Channel (Yebra et al., 2005). Further, the likelihood function can be profiled to construct robust confidence intervals on the estimates (Meeker and Escobar, 1995). Thanumalaya Subramoniam Ph.D, D.Sc, (Madras Univ); FNA, FNASc, FAAS, in Sexual Biology and Reproduction in Crustaceans, 2017. Calanus finmarchicus is the dominant link between phytoplankton and larvae of many commercial fish stocks, for example cod, haddock, herring and coalfish. A new species of marine diatom, Navicula planamembranacea Hendey, was first described from CPR samples taken in 1962. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. URL: https://www.sciencedirect.com/science/article/pii/B9780128033715000035, URL: https://www.sciencedirect.com/science/article/pii/B9780128093375000125, URL: https://www.sciencedirect.com/science/article/pii/B978012374473900196X, URL: https://www.sciencedirect.com/science/article/pii/B9780128010280000660, URL: https://www.sciencedirect.com/science/article/pii/B9780123744739000928, URL: https://www.sciencedirect.com/science/article/pii/B978012804327100128X, URL: https://www.sciencedirect.com/science/article/pii/B9780123744739003891, URL: https://www.sciencedirect.com/science/article/pii/S0065288116300323, URL: https://www.sciencedirect.com/science/article/pii/B9780123744739002885, Dynamic Modeling for Uptake and Effects of Chemicals, Spermatophore and Sperm Transfer Mechanisms, Thanumalaya Subramoniam Ph.D, D.Sc, (Madras Univ); FNA, FNASc, FAAS, in, Sexual Biology and Reproduction in Crustaceans, Pochon-Masson and Gharagozlou-van-Ginneken (1977), Gharagozlou-van-Ginneken and Pochon-Masson, 1979, Encyclopedia of Ocean Sciences (Second Edition), Encyclopedia of Marine Mammals (Third Edition). [12] Scientists look at these levels of ATP because they usually remain constant over a range of physiological conditions, making them useful indicators of biomass. An atlas of distribution of 255 species or groups (taxa) of plankton recorded by the CPR survey between 1958 and 1968 was published by the Edinburgh Oceanographic Laboratory in 1973. In certain regions where this odontocete is abundant, signs of past attacks of killer whales can be seen on the flippers, flukes, and flanks of fin whales. [11] Calanus eggs are typically 0.05 mm (0.0020 in) in diameter, and hatch in 2–3 days. Some scientific evidence suggests that copepods like C. finmarchicus are feeding on microzooplankton as well. Consequently, our objective is to quantify monthly variation in the Calanus finmarchicusprey field in Figure 5. Topex-Poseidon images of the elevation of the sea surface show that flow is nowhere laminar but instead comprises a complex field of cyclonic and anticyclonic eddies having internal flow rates greater than that of the mean current. Understanding the drivers of their relative geographic distributions is required in order to anticipate future changes. They tend to remain at rest until the following spring when they awake and return to the surface waters. During these starving periods C. finmarchicus has shown that it is able to maintain a consistent rate of egg production as well as a constant proportion of adenosine triphosphate (ATP) to carbon; granted their absolute amounts of carbon, nitrogen, and ATP vary significantly. ), Figure 3. Advances in Biochemical Indices of Zooplankton Production, Deep Sea Research Part II: Topical Studies in Oceanography. In Calanus finmarchicus, the outer covering of the spermatophore consists of seven concentric layers of amorphous material of medium electron density (Raymont et al., 1974). Copepodite stage V was used for this experiment, which is the final developmental stage before adulthood. The smallest shows the natural size. In calanoid copepods, only a sticky adhesive body has been found on the spermatophore neck enabling spermatophore attachment. At the onset of the next upwelling event, they are carried passively surfaceward and toward the coast. R. Harris, in Encyclopedia of Ocean Sciences (Second Edition), 2001. Animals were homogenized, prior to storage in liquid nitrogen (Acartia hudsonica, Calanus finmarchicus CV) or after freezing (Acartia tonsa, C. finmarchicus eggs, Temora longicornis, Eurytemora affinis, Calanus glacialis, Paraeuchaeta norvegica, Centropages spp. Hence, the sperm delivery mechanism from the spermatophore to the female orifice is highly complicated in copepods. "Sustained fecundity when phytoplankton resources are in short supply: omnivory by. In the spermatophoric layers of the harpacticoid copepod T. holothuriae, Pochon-Masson and Gharagozlou-van-Ginneken (1977) found a chitin–protein lamellar pattern, similar to arthropod cuticle. MS mRNA is expressed in the neurosecretory cells (NSCs) of the brain [4,6], frontal ganglion, neurons/NSCs of all ganglia of the ventral nerve cord, corpora cardiaca, link neuron 1 (L1) that are located at connections between the peripheral nerves, and midgut endocrine cells of insects [3,4]. In the nerve cord of M. sexta, mRNA levels fluctuate during development and increase during pupal and adult ecdysis [4]. It has been widely assumed by biogeographers that the oceanic gyral circulations are sufficiently closed that the conditions discussed above are generally satisfied; certainly, this assumption is valid for some gyral circulations. So any sample of plankton will comprise abundant individuals of populations that are characteristic of the region (the dominants) where the sample is taken, together with many less abundant species (the vagrants) transported from other regions, some very distant. The neck leads into a tube, through which the sperm passes into the vulva. Using Principal Component Analysis, Colebrook was able to distinguish five main geographical distribution patterns in the plankton – northern oceanic, southern oceanic, northern intermediate, southern intermediate, and neritic. [9] During this six-month period of hibernation, many of these organisms will sink to depths from 500-2,500m in the ocean. The community structure varies extensively between fiords but reflects mostly the shelf habitats found at similar latitudes (Figure 5). J Lubbock - Journal of Natural History, 1854. Hal ini juga ditemukan di seluruh perairan dingin Atlantik Utara, terutama di lepas pantai Kanada dan di Teluk Maine Meskipun organisme lebih memilih jenis habitat, telah menunjukkan bahwa ia mampu bertahan dalam … [11] This ability leads scientists to believe that they may be able to track some of the current changes in climate using the habits of these planktonic organisms. Only one single TK parameter was used, the elimination rate (ke), which determines the time needed to reach equilibrium. Calanus finmarchicus, the idea of organizing preda-tor–prey relationships at the patch, habitat and regional scales should apply generally to large preda-tors. This paper addresses relationships between the distribution and abundance of zooplankton and its habitat in the northern North Atlantic Ocean. of C. finmarchicus, the C5s, and their quality in the Bay of Fundy, arguably a critical feeding habitat frequented by the largest numbers of right whales over a protracted (nominally 4 mo) resident feeding-period. [2], Calanus finmarchicus is especially important ecologically because it shows rapid responses to climate variability, including shifts in species' distribution and abundance, timing of life history events, and trophic relationships. Oil from the marine zooplankton Calanus finmarchicus improves the cardiometabolic phenotype of diet-induced obese mice. How are such patterns maintained? They all spawn during spring, matching the spring bloom to variable degrees, and each has a restricted growth period within the time-window from April to October. In fact, some studies have shown that heterotrophic microplankton provide a "prey resource sufficient for net lipid synthesis as well as egg production". Repeating the experiment might lead to a very different outcome, simply because of the stochasticity in the death process. In the Southern Hemisphere, the diet is almost exclusively krill, mostly the euphausiid Euphausia vallentini but also other planktonic crustaceans such as E. superba, Parathemisto gaudichaudii, or C. tonsus. It can also live in waters as cold as −2 °C (28 °F) and as warm as 22 °C (72 °F). Calanus finmarchicus: COPEPEDIA is an in-development project. This includes diatoms, dinoflagellates, ciliates, and other photosynthetic marine organisms. Abstract Calanus finmarchicus (Copepoda) appears to be very flexible with respect to physical characteristics of the overwintering habitat. The ductal region with its chitinous wall continues with a spherule, which helps in its adhesion to the segmentary fold of the female genital opening. A. John, P.C. 3). We basically need to estimate survival probabilities from the observed death frequencies in a test population. This rice-sized planktonic crustacean is primarily an oceanic and subsurface species carried into coastal regions and open bays. But by crossing the shear-zone within the pycnocline and passing 12 h within the slow or even contrary transport of the deeper circulation, many diel migrants must significantly reduce their passive transport within the surface water. L. Yebra, ... S. Hernández-León, in Advances in Marine Biology, 2017. In subarctic waters, the zooplankton is composed of few species, but with high biomass. In another harpacticoid species, T. holothuriae, there are several secretory granules that constitute the “core” of the spermatophore (Gharagozlou-van-Ginneken and Pochon-Masson, 1979). Other environmental conditions and their ranges include salinity (18–36 pps), oxygen (1–9 mL/L), nitrate (0–45 μmol/L), phosphate (0–3 μmol/L) and silicate (1–181 μmol/L) levels. [10] Many scientists believe that C. finmarchicus use this strategy as a survival method by reducing physiological costs and predation risk. Lawrence. The copepod spermatophores possess well-defined spermatophore layers and a variety of secretory substances that enable spermatophore attachment and sperm expulsion during mating. Using these data, we trained seasonal habitat models and projected them onto environmental data for each 8 d period from January to … The aim was to study the effects of upwelling filaments and island-induced eddies on the growth of two copepod species abundant in the region. Many studies have indi-cated that the presence of large aggregations of the right whale’s primary prey, older stages of the calanoid copepod Calanus finmarchicus, is probably the single most important component of right whale habitat (Wat-kins & Schevill 1976, Wishner et al. In fact, these rates were strikingly similar to the egg production rates of those recorded in the lower St. Lawrence estuary, where the water had a much higher concentration of chlorophyll (indicating a larger presence of phytoplankton). Fin whales feeding in the North Atlantic. A generalized structure of the biological community from the shelf to the inner part of the fiord. Possibly, diet varies with season and locality. Sometimes confused with C. helgolandicus and C. glacialis, C. finmarchicus is a large planktonic copepod whose chief diet includes diatoms, dinoflagellates, and other microplanktonic organisms. Upper Loch Etive represents a habitat of pure C. finmarchicus (as confirmed with population genetic studies, Søreide pers. Since the scaled TK model (Eq. Given the encouraging results obtained in the assessment of C. finmarchicus growth, from both laboratory cultures and at-sea cruise experiments, the AARS method was applied to study natural zooplankton communities in the North Atlantic Ocean. The Platycopoida and Misophrioida are primarily benthopelagic groups, the latter having two pelagic species. The central part of the North Atlantic Subtropical Gyre notoriously retains a floating population of macro-algae (Sargassum muticans), and the gyre within the semienclosed Norwegian Sea retains a persistent population of Calanus finmarchicus. The first application of the AARS activity as a proxy for copepod growth in the field was in the subtropical waters of the Canary Islands (Yebra et al., 2004). ), Yoshiaki Tanaka, in Handbook of Hormones, 2016. Organisms with asexual reproduction, such as phytoplankon and perhaps some tunicates, have no such requirement, and consequently algal species are more cosmopolitan than metazoans. Of these, granule A, rich in mucopolysaccharides, corresponds to the Q-bodies in their capacity to increase in volume by water absorption for the expulsion of the gametes from the spermatophore ampulla. The North Atlantic copepods Calanus finmarchicus and C. helgolandicus are moving north in response to rising temperatures. For example, humpback whales Megaptera novaengliae feed mainly on planktivorous fish such as herring and sand lance. In the harpacticoid copepod, Diarthrodes cystoecus, Fahrenbach (1962) named the inner vesicular bodies (=core substance) responsible for the ejection of Q-bodies by analogy to Heberer’s Q-spermatozoa. The seasonal migrations of Calanus finmarchicus between the near-surface and 500–1000 m maintain enough individuals in suitable advective trajectories within the subarctic gyre for centers of persistence to be maintained. m −2).To our knowledge, this is the first report of massive overwintering of C. finmarchicus … ”Effects of oil from Calanus finmarchicus (Calanus Oil) in human subjects. Distributions of ten representative zooplankton taxa, from recent (2000-2009) Continuous Plankton Recorder data, are presented, along with basin-scale patterns of annual sea … The use of indirect indices allowed assessing how hydrography (mesoscale structures) affected the distribution and metabolic rates of copepods, including growth, with both vertical and horizontal mesoscale resolution. Small copepods may be abundant, especially during summer and autumn, and are not major pathways to the juvenile and adult fish. Data suggest measurable degradation of habitat quality over the past ten years, primarily due to direct impacts of bottom-contact gear used in commerci… (3.6)) was used, the scaled internal concentration has the dimensions of the external concentration, and in equilibrium, its value will equal the external concentration (see right panel of Fig. 3.6). The larger copepods forms (i.e., Calanus finmarchicus and Metridia longa), the chaetognath Sagitta elegans, and the two krill species (Thysanoessa spp.) It is also found throughout the colder waters of the North Atlantic, especially off the coast of Canada, in the Gulf of Maine, and all the way up to western and northern Svalbard. Habitat Copepoda Calanus Finmarchicus di Laut Utara danLautNorwegia. Right panel shows the predicted scaled internal concentration, as implied by the fit on the survival data. The data set comprises observations on survival over four days, with seven exposure treatments (30 animals each) and a control (60 animals). Several species of harvestable fish, including cod, herring and red fish (along with a plethora of other marine life) depend on C. finmarchicus for some form of nourishment. The cuticular envelope extends up to the thin duct, equivalent to the neck region of other copepod spermatophore. Further west, in the Labrador Sea, this biochemical proxy allowed the effect of mesoscale hydrography on zooplankton production during both spring and winter (when it is not possible to assess female EPR), and from surface to 1000 m depth, to be studied for the first time (Yebra et al., 2009b). Since there are no absolute boundaries in the ocean, all retention areas will be more or less leaky, and individuals will be lost into the general circulation. Dry weight and C/N ratio The exchange of the copepod Calanus finmarchicus between the Vestfjord and the Norwegian coastal current was studied by net sampling and hydrography. Reid, in Encyclopedia of Ocean Sciences (Second Edition), 2001. Also, AARS activity was validated as an index of Calanus finmarchicus somatic growth over a wide range of geographical areas, seasons and feeding regimes (Yebra et al., 2006b). Other secretion granules (B, C, and D), mainly proteinaceous and polysaccharidic in nature, may contribute to the attachment of the spermatophore to the female, by forming the spherule lodged in the vulval folds. It is common for disjunct populations to partition a single more-or-less closed gyre, as do species-pairs of North Atlantic copepods. In any case, it makes sense to also try the alternative model (individual tolerance) on this data set; this stage of copepodites can be variable in lipid content, which may translate into interindividual differences in sensitivity (Hansen et al., 2011). m −2 (range: 26700–49000 ind. Planktologists are reluctant to question the current paradigm that diel vertical migration of oceanic zooplankton is primarily a response to predation (as it undoubtedly is in lakes), so this possibility has been largely neglected. It is also found throughout the colder waters of the North Atlantic, especially off the coast of Canada, in the Gulf of Maine, and all the way up to western and northern Svalbard. Scientists working in Canada estimate that 90%–100% of larval redfish prey on Calanus eggs in the Gulf of the St. Fit of the TKTD model for survival to data for the marine copepod C. finmarchicus exposed to mercury (left panel). These layers are positive to histochemical tests for protein, carbohydrates, and lipids. For the same reason, the parameters for the threshold (c0) and killing rate (kk) also have external concentration in their units (see also Fig. 3.5). The persistence of local populations may be the mechanism by which bisexual organisms in the plankton maintain a sufficient population density for successful reproduction, as Sinclair has suggested. Although C. finmarchicushas been reported as widely distributed (Wilson 1932), it is likely most abundant in the North Atlantic … These products of the Calanus® Complete series are suitable as starter and weening feed for larval and juvenile shrimp in aquaculture, and as complete feed for ornamental fish. We use cookies to help provide and enhance our service and tailor content and ads. In the Irminger Sea, the AARS method showed that summer epipelagic zooplankton production distribution matched the major physical zones described in the area and that this distribution was mainly driven by food availability rather than temperature (Yebra et al., 2006a). Calanus finmarchicus - Taxon details on Interim Register of Marine and Non-marine Genera (IRMNG). form easily identifiable trophic links in the transfer of materials to higher trophic levels. Although the organism prefers these types of habitats, it has demonstrated that it is capable of surviving a wide range of environmental conditions. Höper AC, Salma W, Khalid AM, et al. The group includes the species Calanus finmarchicus (Gunnerus), a dominant component of North Atlantic boreal ecosystems, first named nearly 250 years ago as Monoculus finmarchicus by Johan Ernst Gunnerus, Bishop of Trondheim in Norway (Figure 2). C. finmarchicus is a cold-water species whose center of distribution lies in the north-west Atlantic gyre and the Norwegian Sea (‘northern oceanic’). The toxicokinetics of mercury were derived from the survival pattern over time (no body residues were determined in the experiment). Most significantly, do the almost ubiquitous diel migrations of many kinds of organisms also serve the same purpose? The most notable shift for E. glacialis was a sharp decline in sightings per unit effort (SPUE) in the Bay of Fundy critical habitat (Figure 2a,b). Seasonal patterns of E. glacialis and C. finmarchicus have shifted significantly from the early period (2004–2008) to the late period (2012–2016). Finally, the Monstrilloidaare exclusively marine, with parasitic juveniles, but a pelagic adult stage. Populations of Calanus spp. 18,000 years ago), the species migrated north in order to maintain its large populations. Zooplankton and Climate Change - The Calanus Story. In a statistical study of environmental properties defining C. finmarchicushabitat, Reygondeau and Beaugrand (Reygondeau and Beaugrand, 2011)suggest that the species will shift its biogeographic range in the western North Atlantic, following a northward shift in the eastern North Atlantic, and disappear from the Gulf of Maine … (A) Cyclopidae; (B) Cyclopinidae; (C) Oithonidae; (D) Thespessiopsyllidae; (E) Asidicolidae; (F) Archinotodelphyidae; (G) Mantridae. Calanus AS is also currently engaged in the development of other uses for C. finmarchicus in aquarium feed, health and nutritional products, dietary supplements, flavoring ingredients, ... and decompose,” thereby providing habitat unsuitable for C. finmarchicus (Werme and Hunt 2006). The Poecilostomatoida and Siphonostomatoida are commensal or parasitic groups. They include the Q-spermatozoa (quell = swell) which provide, by swelling, the propulsive force inside the spermatophore to expel the B (Befruchtungs = fertilization) spermatozoa. [13], On some Arctic species of Calanidæ. Two closely related species of calanoid copepod – Calanus finmarchicus and C. helgolandicus – which co-occur in the North Atlantic and are morphologically very similar, show very different distributions (Figure 3). Persistence can be maintained only if each local population reproduces at a rate faster than it loses individuals by passive transport out of its retention (or reproductive) area. Much of the early work of the survey focused on biogeography. [3], Calanus finmarchicus primarily feeds on different forms of phytoplankton. This is the concept of Alister Hardy that ‘vertical migration sets them striding through the sea with seven-league boots,’ although perhaps we should regard vertical migration as a mechanism to increase persistence rather than to enhance dispersion. More recently, it has been shown that despite low concentrations of phytoplankton (one of the organism's primary food sources), C. finmarchicus maintained relatively high rates of egg production.