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ICES CM 1997fT:22

The Iife history of Calanusfinmarclzicus at the Norwegian coast: multiple generations orvariable timing of recruitment in an advective environment.

byO. P. Pedersen, K. Tande & D. Slagstad l

Norwegian College of Fishery ScienceUnivcrsity of Tromslf, 9037 Tromslf, Norway.

ISINTEF 7034 Trondheim, NorwaY.

ABSTRACTFor ealanoid eopepods living in seasonally pulsed environments, any predictive life history modelwill have to rely on our ability to understand the environmental signals responsible for the range .of generation patterns observed. The life history of Calanusfinmarclzicus in Norwegian waters iseonsidered to deviate between one and three generations per year. In the shelf region, Lofoten isoften referred to as the northernmost area where a two-generation eyde oeeurs. C. finmarclzicllSwhieh are introdueed to the Norwegian midshelf off M~re during the period of reproduetion, willpotentially be brought to higher latitudes through four different sub regions: the oeeanic, the shelfbreak, the plateau, and the inner shelf. All of these regions potentially exhibit different eurrentmagnitudes and environmental eonditions, e.g. food and temperature. The long term objeetive ofthis study is to investigate to what extent these four defined areas are so unique that they willenable the species to differentiate its life history in orie or several generations? In order toinvestigate these topies, a eoupled physieal-biologieal model for the area has been developed toseale and devise the plankton sampling program whieh is earried out in 1997. The adveetion ofthe population is drive~ by the physical eomponents, while the biological model deseribes vertiealmigration and stage developQ1enL Spatial distribution of the population varies extensively due tothe topography at the shelf. The numerieal abundanee of zooplankton in the four regions appearsto be strongly governed by the loeation of the initial population in the eurrent regime south of theV~ring plateau during the aseending period in spring. The present paper addresses thedevelopment and temporaVspatial distribution related to initial distribution and the eurrent regimealong the Norwegian shelf. This work is a eontribution to the Trans-Atlantie Study of Ca/anusfinmarchicus (TASC).

Keywords: adveetion, biological - physical modeling, Calanus finmarehicus

Ole-Petter Pedersen: Norwegian College ofFisheries Scienee, 9037 Troins~, Norway [tel:+ 4777646036, fax: +4777646020, email:olepp@nfh.uiLno]. Kurt Tande : Norwegian College ofFisheries Seienee, 9037 Troms~, Norway [teI:+ 4777644524, fax: +4777646020,email:kurtt@nfh.uiLno]. Dag Slagstad: SINTEF, 7034 Trondheim, Norway [tel: +47 73594397,email: Dag.Slagstad@eey.sintef.noj

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INTRODUCTIONFor calanoid copepods living in seasonally pulsed environments, any predictive life history modelwill have to rely on our ability to understand the environmental signals responsible for diapauseinduction arid termination. The diapause in C. finmarchicus is often identified by descent of CIVand CV to deep waters at some period in the productive season (Hirche 1996). This process caneither be very synchronized, or extend over considerable period of time, even with only a fractionof the cohort proceeding to a new generation. The life history of Calanus fimnarchicus inNoiWegian waters and the shelf seas is considered to vary between one and three generations peryear. Our current understanding is that the number of generations decreases from low to highlatitudes, and the literature indicates a two generation pattern around the British Isles, FaroeIsland and even up to the \Vestem Coast ofNorway (0stvedt 1955, Wiborg 1954). Lofoten isoften referred to as the northemmost area where this two-generation cycle occurs (Tande 1991).This contention has been developed from data obtained by conventional plankton samplingprograms, and rely on interpretations of the changes in life stage densities over time at selectedsites along the coast. Although Lofoten is termed a northem demarcation iine for a two gemirationpattern, earlycopepodite stages have been detected further north in late summer and early autumnboth outside Finnmark and Troms (Lie 1965, Halvorsen & Tande in prep).

This points to the fact that our current sampling strategies has not enabled us to understand thelife cycle of C.finmarchicus in strongly advective system like the Norwegian shelf. For instance,the datu from Lie (1965) and Halvorsen & Tande (in submission) could be a clear indication thatC. jinmarclzicus produces a second generation even north of Lofoten. However, the populationsampled in August and September in 1994 might have been advected as off-springs from a latespawned Go from the oceanic water outside Troms (Slagstad & Tande 1996). Altemativelytransported northwards as off springs from a GI in the fast flowing shelf break current from areassouth of Lofoten (Poulain et al. 1996).

How could this situation be substantiated? A first step would be to identify any consistentdifferences in population structure during the time period when recruitment occurs, together withsynoptic sampling of the physical and biological environment. This is not a straightforwardundertaking since advection will expose the cohorts io a continuously changing environment,depending on the interplay between individual growth, behavior, environmental variables,direction and magnitude of the water currents.

Populations of C.finmarchicus undergo ontogenetic migrations, which enable them to inhabit thesurface waters down to 50 m from nauplii to CHI. The more advanced stages adopt then agradually deeper depth distribution (Falkenhaug et al. 1997). This means that the surface currentspeed and direction to large extent direct the advection of C. finmarclzicus. Thus during theproductive period C. finmarclzicus which are introduced to the Norwegian midshelf off More,will potentially be brought to four different sub regions: the oceanic, the shelf break, the plateau,and the inner shelf all with potentially different current speeds and environmental conditions(such as food and temperature). We could then ask: are these four defined areas so unique duringthe productive season that they will enable C. finmarclzicus to differentiate its life history in oneor several generations? .

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In order to attack this problem successfully, a concerted modeling and field program are beingcarried out at the University ofTromsp. This integrated effort starts with a modeling study thatproceeds a large-scale plankton sampling program covering the Norwegian shelf from Mpre toLofoten. A coupled physical-biological model for the area wiII scale the effect of advection withregard to the population dynamics of C. finmarchicus as a guideline for designing the samplingstrategy for the area. The objectives of our modeling studies and field program are:

1) What is the source areas for C. finmarchicus being at the mid Norwegian shelf dtiring theproductive season?

2) What is the integrity of the various regions defined above with regard to the populationstructure of C. finmarclzicus?

3) What are the effects of advection along the shelfbreak far the population structures observediri the northem part of the Norwegian coast?

4) What are the across shelf distances needed in order to define differences in population agestructure due to environmentally controlled growth and developmental schemes?

PHYSICAL ENVIRONMENTAt the Norwegian coast (Fig. 1), the near surface circulation is in general thorough described (seePoulain et al. 1996). Drogued drifter tracks demonstrate that the ocean shelf region couldbasically be separated in four regions: the offshelf oceanic region (1), a fast moving (speed> 40einls) body of water following the shelf break eontinuing to the north of LofotenIVestera1f~n (2),another enters the shelfproper at Mpre and flows e10se to the continent ending in Vestfjorden (3).The surfaee water at the Helgeland and Vpring plateaus are eharacterized by slow moving water(speed< 40 cmls) indicating aseparate area with higher residenee time for plankton than in thefast moving water at the shelf edge (4).

MODEL FOMIULATIONPhysical modelThe flowfield used in the present work is simulations of the currents in the Nordic Seas covering

. the period from 1988 to 1991 (see Ädlandsvik & Eriksrpd in prep). The f10wfields have beenproduced within the EU funded project Trans-Atlantic Study of Calanusfinmarchicus (TASC),by the Princeton Ocean Model (POM) developed by Blumberg & Mellor (1987), modified by TheNorwegian Meteorological Institute (DNMI) and the Institute of Marine Research (IMR). Themodel set up has been described in details by Ädlandsvik & Eriksrpd (in prep), but abriefgeneral outline is given in the following.

The model is a 3D baroclinic ocean model, with the surface elevation, velocity, temperature andtwo variables for vertical mixing as model variables. In addition to the initial and boundarydescription of the model variables, the model forcing may include wind stress, air pressure, heatexchange with the atmosphere, tidal forcing and river run-off. The most important modification isthe use of the F10w Relaxation Scheme (FRS) as the open boundary condition. This method isand the implementation in POM are documented by Martinsen & Engedahl (1987) and Engedahl(1994).

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The model setup is derived from the setup used by Svendsen et al.(1995) to simulate thetransport of herring larvae along the Norwegian coast. The main differences are a longer modeldomain, more rivers, a different set of sections and simulations covering a whole year. The largescale model domain (Fig. 2) has a horizontal resolution of 20 km and the number of grid cells is208 x 120. The initial description of sea surface elevation, currents, salinity and temperature istaken from the DNMI-IMR diagnostic dimaiology (Engerdal et al. 1995), arid at the open,boundaries this is complemented by the four tidal constituents, Klo M2, N2 and S2 (see Flather1981, Gjevik & Straume 1989, Gjevik ei al. 1990). The meteorological forcirig is taken froll} thehindcast archive of DNMI (Eide et al. 1985). In order to compensate for the lack of heathexchange between the ocean and atmosphere a simple approach by Cox & Bryan (1984) has beenused.

The simulations used in the present paper started from the same climatology for each of the 4years, with a spin-up time from 15 November the proceeding year before saving of results startedat 1 January. The simulation continued to the end of each year. The variables stored are horizontalcurrent U and V, vertical current W and temperature T. These fields are stored at 12 depth levels,10,32,50, 75, 100,200,300,400,600, 1000 and 1500 m, respectively. In order to filter out moreof the tidal variability, the stored files are 25 hour averages from half an hour before midnight tohalf an hour after next midnight.

The flow field is interpolated horizontally and vertically. The horizontal interpolation follows theequation:

VI v2 v3 v4-+--+-+--(R ) = R/ R/ R/ R/

V -,~ 1 1 1 1,,-+-+-+­~RP R P R P R P

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The interpolation is performed in U and V direction, and V indicates magnitude of current definedat the boundaries of each grid cell, while the indices are assigned to the closest adjacent cells. Pindicates power of interpolation, and R provides euclidian distance to the point in the adjacentcells where the current is defined. In this model, the power of 2 is applied. The differencescompared to the power of 1 were significant, while the difference between power 2 and 3 wereminor.

The U and V current between the previously specified depth levels are calculated as a linearfunction between the subsequent layers. It should be noted that the algorithms calculatinginterpolation adapts to discrepancies between the flow field and the topography matrix.Additiorially the dass of interpolation algorithms handles interpolation in the adjacency tolandmasses. Temperature is interpolated in a similar manner as described above, with some minormodifications. For,each grid cell, the temperature is.assumed to specified in the center, which isdifferent compared to the current. The values describing the currents are defined at the edges ateach grid. These minor differences in the physical assumptions regarding the parametersintroduce a slightly different approach for interpolation. .

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Biological modelThe objectives posed for this work is highly dependent upon an adequate interaction of thepopulation dynamic and behavior of C. jinmarchicus with the flowfields during the four-monthmodel scenario. We have therefor emphasized two aspects in the biological concept and adetailed description is found below. Although c.jimnarchicus is considered to have more thanone generation per year in the target area (Tande 1991), the present approach has outlined onlyone cohort being produced during the 120 days simulation period. In order to meet the objectivesof the study, we have designed a preliminary concept consisting of a stage-structured populationmodel and a vertical behavior model. The model approach is to mirnic the developmentalschemes and the stage-specific vertical distributions as observed in C. jinmarchicus fromNorwegian waters. One should also realize that mortality has been reduced to zero, assuming thatthe advected particles are the survivors of an initially larger population.

Stage-structured population modelAs a first approximation, we simulated a one generation during the 120 days period in order toreflect the pattern observed from several Norwegian fjords (see Tande 1991). The timing oftheonset of reproduction was set to mirnic the introduction of the Gi as observed in Malangen in1992 (Fig. 3A).

Some uncertainties remain about the relative importance of temperature and food availabiIity indetennining the rates of growth and development in calanoid copepods (see Miller & Tande1993). Although food limitation cIearly can occur in the field, we only, for the moment have gooddata on the temperature conditions. We therefor developed our model on the basis of atemperature function for stage duration derived from Corkett et al. (1986). The functionalrelationship is tenned Belehnidek function (Belehnidek 1935), and is given by:

Stage duration(d) = a j(T+~)r

The values for Clj are provided in Miller & Tande (1993), and T is the vertically and horizontallyinterpolated temperature value. The parameters Sand yare fitted to a small set of rearing data,and the values 10.6 and -2.05 are used (Miller & Tande, 1993). The fitted values of Clj aremodified to approximate the growth patterns for C. marshallae (Peterson 1986) and C. pacificus(Vidal 1981). This approach is mainly due to the fact that these species are better studied, and itstill remains an unsolved task to obtain reliable estimates for C. jinmarchicus, resolved foroceanic and coastal regions.

At each time step (l hour), the growth is calculated for each particle, and the absolute stage valueis calculated by the equation:

A copepod living at temperature T will complete stage j in Clj(10.6r2.o5 days. One should realize

that due to ontogeny and advection, the temperature varies throughout the period of simulation. In

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the equation provided above, this fact has been taken into account. During the refinement of themodel, the parameter space [;,y] should be explored in order to determine its importance withregards to the stage development progress.

The development pattern of nauplii and copepodites (Fig. 3B) match cIosely those observations(Falkenhaug et al. 1997). Under these circumstances, the species enters diapause during thesummer period, and reside at depth as a proportion of 20 % CIV and 80 % CV (see Taride &Slagstad 1991). During the overwintering period, this proportion has been shown t9 vriry betweenfjords arid open waters, but the factors goveming these variations are largely unknown.

Vertical belzavior modelThe stage specific vertical distribution of C. jinmarclzicus is in general weIl described (MarshalI& Orr 1972), where the offsprings is confined to the upper water masses, and a progressivelydeeper depth distribution with age is observed with age. During the recruitment period in talespring, substantial local variation occurs, where, for instarice, differences thfough time at one .station can be as great as differences between stations in North Noiwegian fjords (Tande 1988)and in the Barents Sea (Unstad & Tande 1991). Although both diel and ontogenetic migrations doexist in C.jinmarclzicus, the proximate causes (Le. from the environment) driving the observedbehavior rire still dubious: In the present model study we have adopted data from Freroeses water(Heath et al. 1997) and a Norwegian fjord (Falkenhaug et al. 1997), which cover the eniireseasonal cycle in order to mimic the stage structured vertical distribution of the population in thewater column.

Ascending from diapause in deep waterThe onset of the termination of diapause might vriry along the latitudinal range (see Miller et al.1989). In Norwegian waters we have data indicating that sexual differentiation and molting toadults commences in Januriry arid Februriry (Tande & Hopkins 1981). It is considered that theascent migration takes pIace soon afterwards, and brings the adult population to the surfacelayers. \Ve lack detailed data of the migration timirig and speed of adult females from the area ofstudy, so we use the data from Freroese water obtained from depth stratified sampling by WP2nets during the first 6 months of 1994 (Heath 1997). These data shows that C. jinmarclzicus wasconcentrated at depths greater than 400 m until early March, and moved towards the surfaceduring March and April. Data from Norwegian waters indicate that ascending comrriences slightlyearlier than in Frereose water, where surface aggregations of females occurs already in mid Marchin Malangen (Falkenhaug et al. 1997). Since the low time resolution of the sampling programhampers a more detailed analysis of the ascending rate in these data sets, we decided to adopt theinformation provided by Heath (1997). In our model approach we have designed the verticalmigration as a normally distributed process. The literature (Diel & Tande 1992) indicates aspawning period of approximately 14 days, when reaching surface waters after the ascendingmigration. We have assumed the vertical migration period to be normally distributed with a meanof 40 days and the 95% CI of 14 days, N(40,3.5). The remaining 5% is uniformly distributedwithin 40±7 days. This explicitly ensures a spawning period of 14 days in the surface waters. On

.behalf of the vertical migration period calculated, avertical migration velocity (m1day) isassigned to each particle and applied throughout the entire ascending pefiod.

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Recent investigations have revealed that the vertical migration pattern in the spring containscertain periods of non-ascending behavior. It still remains unclear what the inducing physical andbiological mechanisms are, and to what extent this migration pattern is valid.

Summer surface aggregation and descending after diapause inductionThe population of C. jinmarclzicus studied in Malangen in 1992 formed the observational basisfor the veriical distribution of the modeled recruiting generation. It was sampled monthly with aMOCNESS with the following discrete depth strata: 0-20,20-50,50-100, 100-150, 150-200,200­250 and 250-360 (Falkenhaug et al. 1997). C.jinmarclzicus stages CI-Crn appeared in the top 50m in April, with younger stages found slightly higher than the next older stage. The depthdistribution was usually unimodal, with small migration amplitudes and little indication of anymigration on the scales sampled (Fig. 5 A). Stages IV and V were often bimodallydistributedwith small differences between day and night distributions. They tended to avoid the upper 20 mduring the day form lune onwards, and from lune to August the bimodal distribution changedgradually to an unimodal distribution at depth.

The surface aggregation is assumed to remain in the top layer, 0-10m, and no diurnal migration isintroduced. Each particle has a trajectory in the I-dimensional stage space, and at two thresholdsin this space, adecision is made whether to start the descent for diapause. Iriitially, 80% of thepopulation is assigned to remain in the surface until 80% of stage 5 is completed (CV.8), whilethe remaining 20% of the particles initiate a vertical migration behavior having completed 80% ofstage 4 (CIV.8). The fraction which decides the migration scheme (down as CIVs or CVs, 20/80)is selected to reflect our notion of the ontogeny encountered and detected in field studies. Thisinitial tunirig of the model is subject to be adjusted when further studies indicate that the fractionapplied is incorrect. The terminal depth for each particle is modeled as a uniform distributionhaving 150-350 m as the domain. No evidence substantiates that there are differences withrespect to preferred terminal depths between CIVs and CVs, thus this approach.

The model mimics the distribl,ltion pattern above, and demonstrates a time of descent betweenday 90 and 120 (Fig. 5B). The bimodality in the depth distribution is not so clearly retairied as inthe data from Malangen, but this might be due to aless homogenous behavior of the fieldpopulation (Le. due to advection of different age groups) compared to the model population.

RESULTS AND DISCUSSIONIn order to identify the source areas for C.jinmarclzicus being at the Mid-Norwegian shelf duringthe productive season, we performed three scenarios, as outlined in the following (Fig. 6). Sincethe drouged drifters indicate that a major entry area to the mid Norwegian shelf is located aroundM~re (Poulain et al. 1996), we defined three different source areas for the particle trackingschemes: an oceanic (Scenario n, a shelf break (Scenario IO and a true shelf (Scenario llI) region,each with the same location of four target boxes. In scenario I, the release box was defined alongthe bottom depth contours of> 620 m to the east. In scenario ll, the release box was shiftedonshelf and was defined between the 200 and 700 m bottom depth contours. In both theseschemes the particles were released at 200 m of depth. In the shelf scenario we defined the releasesite within depths < 200 fi, and the particles were released at 60 ni of depth. The simulation time

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was set to 120 days, the population of c.jinmarchicus was specified according to the outlineabove, and a total amount of 200 particles were released in each run.

Scenario INo particle trajectories were found to enter through the two target boxes located on the shelf (Fig.7). The majority of the particles in the northem and eastem region hit the two oceanic targetareas, although with a slightly different accumulation pattern.

Scenario IlParticles released at the shelfbreak appear to follow two paths, one across the shelf and anotheralong the shelf break (Fig. 8). An unimodal accumulation distribution with time was found in boxtwo. A two pulsed accumulation pattern was found in the target box at the shelf break, whichmirrors the two tracks that were followed. No particles were observed to leave offshelf into theoceanic realm during the period of simulation.

e Scenario IIIIn the most shore ward scenario, the hits in the target area on the shelf were all similar to thatgiven for box three (Fig. 9), with an accumulation pattern slightly northem delayed with time.A substantial amount of the particles were retained in the released area, and some of them weretrapped close to the mouth of the fjords.

Population structure 01developing colzorts.In order to test if the thermal regimes in oceanic, shelf break and shelf water is sufficient large toimpose differences in the population dynamics of C. jinmarc1zicus during the period ofsimulation, we have outlined the cohort development from the scenarios.

•The cohorts that were advected in the oceanic, shelf break (Fig. 10) and residing at the shelf atMpre (Fig. 11, upper panel) have similar developmental scheme. The cohort generated in theoceanic area has consistently longer stage duration than the other two. The oceanic populationreached the defined residing condition of20% CIVs and 80% CV's, in around 110 days, asopposed to the other two, which have reached a similar condition at day 85. A slightly differentdevelopmental schedule is attained in the population advected northward on the shelf, where thedevelopment scheme demonstrate a marked tailing off for CIIIs and CIVs (Fig. 1110wer panel).This clearly demonstrate that the trajectories of the advected particles on the shelf are exposed todifferent thermal regimes that the developmental schedules are clearly altered compared to theseformer scenarios.

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Initial settings ofthe model - assumptions and implicationsIn the present study we have assumed that the eurrent field is invariant with respeet to time, :indhave therefore released one eohort in order to deteet the major traeking routes of the population.Henee the souree areas for the particles found in the different regions is explicitly detected. Thevarying release depths for the simulated scenarios provide the opportunity to explore the effect ofdifferent ascending velocity on the distribution pattern of the cohort. The releaseof the particleswithin the same time wiridow is obviously a highly artificial setting. Field data elearly indicatethat a vertical ascending period extend over a longer time period, and might vary latitudinally(Falkenhaug et al 1997, Heath 1997). We have also modeled a similar timing of the onset ofspawning in the scenarios, which also is not in accordance with the obscrved variability in thearea of study. The spring spawning of C. finmarchicus in the offshelf/oceanic waters are found tobe delayed by several weeks compared to Norwegian fjords (Tande & Hopkins 1981, Aksnes &Magnesen 1983, Falkenhaug et al 1997, Ellertsen 1997). Gur approach has been taken in order tofacilitate identifications of source areas and the impact of spatial differences of advection aridtemperature on the population dynamics of C. finmarchicus as described in the above objectives.

Afraction of the cohort released in all scenarios experienced a high rate of advection along theshelf break. Dudng the simulation period, these particles were at several occasions transportedinto the Barents Sea, while others retained their positions in the strong current, splitting off to thewest of Spitsbergen. The fraction experiencing the highly advective field along the shelf breakhris a fast stage development compared to the oceanic scenario, although some of the partielesreleased in the oceanic scenario are trapped in the shelf break waters. The overall eontribution ofthese rapid movers to the population structure in the oceanic environment is negligible. The shelfpopulation exhibits a developmental pattern elose to that observed for the shelf break scenario.The development patterns are in elose resemblance with a tendency for later closing of the cyelein the latter population. This eould be explained due the fact that a more confined physical settingforms along the shelf break compared to the more heterogenous environment onshelf.

Scenario 3 contains particles released at the shelf off More, and a major fraction of the populationdoes not reach the shelf areas west of Helgeland. The southern part of the initial population istrapped ~ong the western coast ofNorway, while those released further north (gridpoint 67+) isadvected along the shelf and finally leaves the shelf through Trrenadjupet. This indicates that evenif the particles are released in broadly the same area, they are prone to experience majordifferences with respect to residing location through their life time. This fact is elearly indicatedhy the tailirig off for the copepodite stage development in scenario 3 (Fig. 11).

In the present paper, we have studied the likelihood of different generation patterns of C.finmarchicus in the oceanic, shelf and onshelf sites. It is obvious that the oceanic regions onlyfacilitate an annual genenition due to late eominencement of spawning and the generallow seatemperature. In the onshelf region, the long residence time in high temperate waters will enablethe species to develop two consequtive generations during the productive period. This has beenemphasized by the present simulations, where the onshelf generation time (Le. from egg to CV) isabout 80 days. The particles being advected along the shetf, has a similar stage progression, butthey are conveyed northwards at high velocity. Due to the conveyor belt effect, their maturestages are not encountered before they reach high latitudes. Thus the number of ge!1e~ations

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produced here is still obscure, and data obtained during the field prograrn in 1997 could providemore evidence for the seasonality of the stage structure in the area.

This paper has indicated the major transportation routes of zooplankton on the shelf and in theoceanic regions. It is demonstrated how the physical settings influence the population structure ofc.finmarchicus. One should bear in mind that population dynarnics observed are closely drivenby the Belehradek temperature function, and do not take into consideration any effect from thefood environment. The food environment is anticipated to differ between various regimes coyeredin these simulations, and a detailed evaluation of the phytoplankton data at hand is greatlyneeded. The source areas of C. finmarchicus for the shelf is of vital importance in the context ofseeding channels. The region west of M~re and south of the V~ring plateau appears to beexceptionally interesting in this content. The model indicates that this region 'feeds' the shelf withzooplankton, while other areas south of M~re and oceanic regions only provides minorcontributions to the shelf.

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Slagstad, D. & Tande, K.S. 1996: The importance of seasonal vertical migration in the acrossshelf transport of Calanus finmarchicus. Ophelia 44: 189-205

Svendsen, E., Fossum, P., Skogen, M.D., Eriksrpd, G., Bjprke, H., Nedraas, K, & Johannesen, A.1995: Variability of the drift patterns of spring spawned herring larvae and the transport ofwater along the Norwegian shelf. leES C.M. 1995/Q:25.

Tande, KS. & Hopkins, C.C.E. 1981: Ecological investigations on the zooplankton communityin Balsfjorden, northem Norway: the genital system in Calanusfinmarclzicus and the role ofthe gonad development in overwintering strategy. Mar. Biol. 63, 159-164.

12

I

I

Tande, K. S. 1991: Calanus in North Norwegian fjords and in the Barents Sea. In Sakshaug, E.•Hopkins. C.C.E. and 0ritsland. N.A. (eds). Proceedings o/the Pro Mare Symposium 0/PolarMarine Ecology, Trondheim. 12-16 May 1990. Polar Res. 10,389-407.

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Ädlandsvik, B. & Eriksr~d. G. 1997. A hindcast simulation of currents in the Nordic Seas.Report, MRI. Bergen.

•

13

0 ~ 8 0 0 0 0~ ~ g ~ ~~ - 0> '" t- '"

~

~

g

i2

g

0~

~

g

~

0 0

8

0 00> 0>

0

'"

0t-• 0

'"

~

~

0

'"

0

'"

~ ~

0 0 8 li\ 0 0 0 0 0 0 0

~CD t- '" U1 .. '" '"

Fig 2. Bottom topography of the Norwegian Sea with adjacent regions

6), m

Generation time Idaysl

Fig 3. Caumus finmarchicus. A one year generation cycle for the -species as described fromMa~angen, North Norway in 1992 (top - redrawn horn Fa1kenhaug et al 1997);Stage progression as modelIed in the standard run (bottom)

140

~C> 12:)(.)

c.. ~

-- 1CO::JJ:l<

•111"7 m.a m..5 m-4 m-3 m-2 m-1 m m+1 rr'l+2 m+3 m+4 m+5 m+6 m+7

Ascendance time [days]

Fig 4. Calanusfinmarchicus. The modeled ascendance time far adult females during the first 30 days oftheperiod of simulation. See text for further details.

ABUNDANCE (ind.· m 3)

CIV

CV

ClC>o

o

ClC>o

....oo

....o

t"ooo

'"oo

1\la)' Jun Jul Aug

CS Day 60 CS Day 90 CS Day 120

0-40

40-80

80·120

120·160

160·200

200·240

240-280

280·320

320·360

360-400

400-440

440-480

480·520

II------,------III------1------III------i------III------.,------I

•I------,------•II------ ... ------III------'1------•II------"1------III

------~------III

------~------II

I

------ ... ------•II

------~------,II

•I------,------•••------i------III------1------II

•------,------,I

I------,------III

I,I------ .. ------III------"1------I

II

-----_ .. _-----I

II

-----_ .... _-----III

I,-_.1_-----

IIII----,------,,I---1------I

•I-----'1'------III

------ .. ------II,•I,

------ .. ------I

•I______ .l _

,II

o 2 0 500 1000 0 100 200Abundance [#]

Fig 5. Calallusji1l11larc/ziclls. Top panel: Vertical distribution of copepodite stages IVand V from l\fay to August in l\falangen North Norway in 1992 (redrawn fromFalkenhaug Cl al 1997). BoUom panel: Modeled depth distribution of copepodite

00

70

10------­20 40 80 100

-

120

l

Fig 6. Release sites for oceanic, sbelf break and sbelf in tbe tbree test scenarios witb locationoftarget boxes (1-4)

4...!.{ i .$ .Si !7(' 0( ~:: :,. es I",.

11,0 120

,

\ ., . ~ ....,.

00

J

Fig 7. Origin sites of particles released in oceanic waters which hits the along shelf (top panel) and off shelf(bottom panel) target boxes together with the pattern of accumulation rate.

r-----------------------------

''ll' "'.' j •. ,. .. ~ • ~ _ ,,,•• t: I·. ~. ~ '" o>:t;. I'" I; ll> "" • ••• :. i;_ ... ., '< ••• tl • 1I to", I; I' .... 1.I • • ,

.... , , , • ., _ •• >0 .." ..: # " ... ., .

,.. ......1

. J••••. ":"J.

;y....~

/'

1.E

. .-.... .t " •• "',,"' ~ ~: ~ .. ~ ~•.• " " .. ~ .. ,· .· ,

. ,,- •• ~ " t- , .. K' " ~ ,. ~.• Jt .. I > .. '" ~ ', .. 'I ' .,. •• 1< ,· ." .

Fig 8. Origin sites of particles released on the shelf which hits the two northern most target boxes. Arrowsindicate the bifurcation of particles giving rise to two major tracking routes to target box 3 (lowerpanel). Pattern of accumulation rate also inserted

•

Accumulation

3- "---::::,....i~~... ~..-' :---. ---

,, I I • I I

... , r r " ',' "' .., , ,

"" .", _:~...... ._-. ~ "':'- .

. .. ~ :. ":'. - .."':'.~ .. .,.... ~- ./: I I

() .......:....,...-~-_ ........-_........--......----'4)

6() ,...----,---.,..---.----.---..,. . .

: j"\: ~l ...

.4() H ~,.. A~ •• A ~~ •••• ~ .. rr ; ., .

m "....... '''"f' .. ~ ...... ,-~ .... A ·'· .... "f····· -...... . .

I\ ' : /

~ ~ / :/ (. "' . \ . / /. \I ...... I , I ,

.. - . . :. . . . . . ). . .:.. ~ . . :..~ .~ . .<'..:. . . . . . . . . ~ . . . . . . . . . ~ . . . '. . . . . . . . . .'. :-.: .~. .7.*.~.F • • • •. ~ .". . . . . . . r..... '- '/ .... ......N. -- t'"

, "ii'~"'irF:--~5~~ ,/ 'E·········· ~'......... ~ ~ /-

............. .. IiIL_.'.~~ ~.~ I.~.~.! :./40

55

45

35

Fig 9. Origin sites of particles released on the shelf which hits target box three, together with thoseresiding on the shelf during 120 days period of simulation. Pattern of accumulation rate alsoinserted.

..

100

90

80

70

~ 60

~SO~

(l)iI::!lf. 40

30

20

10

20 40 60 SOStacls-; ems., N1-6, C1·6

100

1'\,1,)

90

6(l

70

~ EICl

§5Q

J40

3(1

~

10

40 6Q 80StadEJ: ews, N1~. C1·6

100

Fig 10. Calanus finmarchicus. Modeled population structure for the oceanic scenario(upper panel) and the shelf break scenario (lower panel).

..

100

11)­

Erof• .!n'~t4ii

«) SO 80Stad. egg.SI N1-C6

-40 so 80

Stad.eggs, N1..c6

1m

100

Fig 11. Calanus finmarchicus. Modeled population stucture for the on shelf scenario forthe assembly of those which reside in the areas around the release site (upperpanel) and particles which hit target box 3 (Iower panel).