Spatial distribution of digestive enzyme activities of Calanus finmarchicus and C.hyperboreus in Fram Strait/Greenland Sea

Digestive enzymes of copepodite V (CV) Calanus finmarchicusand C.hyperboreus from two different depths were compared duringMIZEX 1984 (June/July) at stations in the ice and open water.CV of both species from 500–200 m showed reduced enzymeactivity, indicating that they were in a resting stage. In moultingexperiments at the end of June using CV from 100–0 m moultingwas delayed and began only after 3 weeks in C.finmarchicus andafter 3 months in C.hyperboreus. These results suggest thatthe deep CV populations are the seed of the new overwinteringstock. In surface CV C.finmarchicus and C. hyperboreus enzymeactivities were generally much higher than in deep CV. In neitherspecies were enzyme activities correlated with chlorophyll concentrations.Activities in C.finmarchicus reflected overall phytoplanktondistribution and were highest in the marginal ice zone, whereasthey decreased under the ice except for polynya stations onthe East Greenland Shelf. In surface C.hyperboreus digestiveenzymes were not correlated with those of C.finmarchicus, pointingto different diets or regulatory mechanisms. Enzyme activitywas lowest in the marginal ice zone and increased under theice. High activities were found at polynya stations and otherclose pack ice. The utilization of ice algae by C.hyperboreuscould explain these discrepancies in digestive enzyme activitiesof both species.     

Density- and sound speed contrasts in sub-Arctic zooplankton

Summary The sound speed was determined for Meganyctiphanes norvegica, for a mixture of Thysanoessa raschii and Thysanoessa inermis and for a mixture of Calanus finmarchicus and Calanus hyperboreus. The sound speed contrasts ranged from 1.014 to 1.044. Seasonal variations in specific density were measured for Thysanoessa inermis, Thysanoessa raschii, Meganyctiphanes norvegica, Calanus finmarchicus and Calanus hyperboreus. The density of 20 mm T. inermis was lowest in November (1.052 g/cm³) and highest in February–March (1.065 g/cm³). For a 20 mm T. raschii the minimal density was determined in December (1.059 g/cm³) and the maximum in February–March (1.074 g/cm³). M. norvegica individuals of 35 mm also had their lowest density in December (1.060 g/cm³), but reached their maximum density in July (1.076 g/cm³).The density of the euphausiids was found to be size dependent. The density increases as the size decreases. C. finmarchicus and C. hyperboreus had densities less than seawater (1.026 g/cm³) during most of the year. Just before spawning the density increased to 1.028 g/cm³ and 1.036 g/cm³ for C. finmarchicus and C. hyperboreus respectively. The seasonal variations of the density were closely related to the lipid content of the animals.     

Life-cycle strategies and seasonal migrations of oceanic copepods in the Irminger Sea

Abundance and seasonal vertical distribution of dominant zooplankters in the Irminger Sea was studied from data collected during four cruises between November 1996 and June 1997. In addition, egg production of Calanus finmarchicus was measured during winter, spring and summer 1996–2001. Five taxa constituted >95% of the copepod biomass, C. finmarchicus, Pareuchaeta norvegica, C. hyperboreus, Oithona spp. and Oncaea spp. A seasonal migration pattern was evident for C. finmarchicus, P. norvegica and Oithona spp.: from December to February, they inhabited the deeper layers, whereas, from April to June, they were most abundant in the upper layers. Oncaea spp. also stayed deep during winter and only a very limited part of the population rose to the surface during summer. C. hyperboreus remained deep from December to April, but had virtually disappeared in June. Reproduction of C. finmarchicus took place in May in the surface layers and was linked to the phytoplankton spring bloom. In contrast, reproduction of P. norvegica occurred at depth in February and was uncoupled with the spring bloom. C. hyperboreus did not reproduce in the Irminger Sea. Data on Oithona spp. and Oncaea spp. indicated that the former reproduced between April and June in the upper layers, whereas the latter reproduced year-round at depth. Thus, data on vertical distribution and seasonal stage composition suggested that the dominant copepods are separated, at least partly, at spatial and temporal scales with regard to overwintering and development.     

Feeding ecology of the lantern fish Benthosema glaciale in a subarctic region

Summary The myctophid, Benthosema glaciale, was found to occur in the region of Davis Strait, but not in northern Baffin Bay. The factors that limited its northern range were believed to be the cold temperature and the long periods of day light in Baffin Bay. During the day B. glaciale was found at a depth of between 300 and 900 m with the population concentrating at about 500 m. At night about 46% of the population migrated to the upper 65 m to feed on copepods, primarily Calanus finmarchicus stage V and C. hyperboreus stage IV for which they showed a high degree of selectivity. The weight of stomach contents of fish with 100% full stomachs was equal to about 3% of their body weight. Feeding occurred mainly at night in the upper layers above the coldest layer of water with a temperature of about 0.5 °C. The biomass of zooplankton and myctophids m^-2 were similar to those for these groups on the Nova Scotia slope during June. The fish fed on the same size range of prey in Davis Strait as on the Nova Scotia slope even though the zooplankton species composition was different in the two regions.     

Integrating conventional microscopy and molecular analysis to analyse the abundance and distribution of four Calanus congeners in the North Atlantic

Analysis of the demographic structure of Calanus species inthe North Atlantic presents particular difficulties due to theoverlapping spatial distributions of four main congeneric species(Calanus finmarchicus, Calanus helgolandicus, Calanus glacialisand Calanus hyperboreus). These species have similar morphologies,making microscopic discrimination only possible between someof the species at late copepodite or adult stages. However,molecular techniques now offer the possibility of screeningsignificant numbers of specimens and unambiguously identifyingthem to species, regardless of developmental stage. Unfortunately,the processing rate of specimens by molecular methods is stilltoo low to offer a realistic alternative to microscopy for analysisof samples from large field surveys. Here, we outline and testan approach involving the use of molecular methodology in conjunctionwith conventional microscopy to assess the species assignmentof developmental stage abundances of Calanus congeners. Ourstudy has highlighted many important methodological issues.First, it cannot be assumed that the species composition ishomogeneous across the development stages; applying proportionalspecies composition of adults to morphologically undistinguishableearlier development stages can result in error. The second importantconclusion is that prosome length may be a highly unreliablediscriminator of C. finmarchicus and C. glacialis.     

Dynamics of coexisting Calanus finmarchicus, Calanus glacialis and Calanus hyperboreus populations in a high-Arctic fjord

We studied the population dynamics of Calanus finmarchicus, Calanus glacialis and Calanus hyperboreus in Billefjorden, Svalbard (78°40N). 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.     

Local variations in size and activity among Calanus finmarchicus and Metridia longa (Copepoda, Calanoida) overwintering on the west coast of Norway

Vertical net hauls were taken at thirteen stations between latitude6008'N – 6120'N and longitude 0304'E – 0700'Ein late November 1980. Size and activity characteristics ofCalanus finmarchicus and Metridia longa were studied. Significantdifferences were noted between C. finmarchicus from differentstations. Average body length, dry weight, protein and lipidcontents, gonad development, and ainylase and trypsin activitiesvaried but average gut fullness and trypsin/amylase ratio appearedconstant. M. longa from different stations showed significantdifferences in average body length, dry weight, protein content,amylase and trypsin activities and gut fullness, but there wereno apparent variations in lipid content and trypsin/ainylaseratio. Those animals inhabiting the most seaward station tendedto show the most specific local charactenstics. M. longa hadconsistently lower lipid proportion with higher gut fullnessand digestive-enzyme activities than C. finmarchicus. The resultstherefore indicate that C. finmarchicus had assumed a winterstate of low activity with dependence on stored energy, whileM. longo relied more upon utilization of available food.     

Feeding behaviour in Meganyctiphanes norvegica (M. Sars) (Crustacea: Euphausiacea)

Meganyctiphanes norvegica (M. Sars) will feed upon the centric diatom Thalassiosira weissflogii (Grunow) G. Fryxell & Hasle but cannot fulfil its energy requirement for metabolism on this food. Its daily metabolic requirement can be exceeded when the euphausiid feeds upon the copepods Calanus finmarchicus Gunner or Centropages typicus Krøeyer, but not when feeding upon the smaller copepods Pseudocalanus spp. or Acartia spp. When feeding upon a natural copepod assemblage Meganyctiphanes norvegica requires high concentrations of copepods to achieve its metabolic requirements, suggesting that the euphausiid may exploit vertically patchy concentrations of prey. Short-term predation rates on Pseudocalanus spp. were also used to estimate feeding rates. Feeding in Meganyctiphanes norvegica appears to be adapted to a spatially variable food supply and rapid exploitation of food sources concentrated into patches or layers. The filter area of the feeding basket of M. norvegica is proportionally smaller than the filter area of Euphausia superba Dana, but has the same allometric length exponent. The filter area probably reflects the difference between the primarily carnivorous diet of Meganyctiphanes norvegica and herbivorous diet of Euphausia superba.     

Egg production and hatching success in the calanoid copepods Calanus helgolandicus and Calanus finmarchicus in the North Sea from March to September 2001

Spatial and seasonal egg production rates (E_r) and egg hatchingsuccess in the copepods Calanus finmarchicus and Calanus helgolandicuswere measured in the North Sea from March to September. Foodavailability was monitored by chlorophyll and protist concentrationsand three size fractions of seston fatty acids. Seasonal andspatial distribution and production differed between the species.Calanus finmarchicus was found only offshore of the 50-m isobath,with decreasing E_r (37–28 eggs female^–1 day^–1)from March to July. Calanus helgolandicus had two abundancepeaks, in spring and autumn, with a low in May during whichtime the highest E_r were observed (38 eggs female^–1 day^–1).At other times, E_r in C. helgolandicus remained lower than inC. finmarchicus (     

Assimilation and biosynthesis of lipids in Arctic Calanus species based on feeding experiments with a C labelled diatom

The dominant Arctic Ocean and North Atlantic copepods Calanus hyperboreus, Calanus glacialis, and Calanus finmarchicus were collected in the Greenland Sea and fed ¹³C labelled diatom Thalassiosira weissflogii to follow the transfer and assimilation of carbon, lipid, and individual fatty acids and alcohols. The diatom was grown with ¹³C for 3 to 5 days and fed then to the copepods. During the feeding period of 14 days, total carbon increased in the copepodite stages V of C. hyperboreus and C. finmarchicus, whereas carbon remained almost constant in C. glacialis females. However, total lipid increased in all species and stages. Highest lipid accumulation occurred in C. hyperboreus in which nearly all lipids were exchanged already after 11 days of feeding. In the other species lipid accumulation made up between 22% (C. finmarchicus) and 45% of total lipid (C. glacialis). The proportion of wax esters was high ranging from 76% of total lipid in C. glacialis to 92% in C. finmarchicus. The fatty acid composition of the alga was dominated by 16:1(n-7), 16:0, 20:5(n-3), and 22:6(n-3). The composition of the copepods was similar because of feeding already on diatoms in the field. In addition, the monounsaturated fatty acids and alcohols, 20:1(n-9) and 22:1(n-11), were major components of the copepod lipids. During the feeding period the highest ¹³C labelling was always found in the C₁₆ polyunsaturated fatty acids and in the 16:1(n-7) alcohol. Because these components occurred only in trace amounts in the copepods they totally originated from the diet explaining the high labelling. It is noteworthy that the 16:1(n-7) alcohol originated only from the corresponding dietary and not from the abundant internal fatty acid. The long-chain monounsaturated fatty acids and alcohols, 20:1(n-9) and 22:1(n-11), are not existent in phytoplankton and have to be produced de novo. They were less labelled in the smaller species but highly ¹³C enriched in C. hyperboreus. Although dietary fatty acids were generally retained by the copepods it seems that fatty acids or even lipids were selectively accumulated and turned over due to bodily requirements, and thus, essential polyunsaturated fatty acids were preferentially retained. During feeding mixing, accumulation, and exchange of internal and dietary fatty acids and alcohols occurred as well as utilisation of lipids from both sources for metabolic requirements. The differences in lipid assimilation fit to the different life strategies of the copepods.     

Distribution of dominant calanoid copepod species in the Greenland sea during late fall

Summary Between 6 November and 12 December 1988, vertical distributions of Calanus finmarchicus, C. hyperboreus, C. glacialis and Metridia longa were studied at three stations in the Arctic water of the Greenland Sea Gyre (GSG) and compared with two stations in the Atlantic water (AW) of the Westspitsbergen Current. Nine depth strata down to 3,000 m were sampled. C.finmarchicus was most abundant in AW, C. hyperboreus in GSG, M. longa showed no preference and C. glacialis was rare everywhere. Stage composition differed with species and water mass. Vertical distribution varied also with water mass in all species but C. hyperboreus, which was always centered between 1,000 and 1,500 m. The other species were concentrated in the upper 300 m in AW and between 1,000 and 1,500 m in GSG, although not all stages followed this trend. Ontogenetic vertical migration leads to significant dislocations of organic matter from the euphotic zone to great depth in the Greenland Sea. In egg production experiments, C. hyperboreus spawned up to 149 eggs female^–1 day^–1. Implications of stage composition, sex ratio, and gonad maturation on copepod life cycles are discussed.     

Lipids and life strategies of Calanus finmarchicus, Calanus glacialis and Calanus hyperboreus in late autumn, Kongsfjorden, Svalbard

Stage IV and V copepodites were the dominant forms of Calanus finmarchicus, C. glacialis and C. hyperboreus in Kongsfjorden in late September 1997. Stage IV and V copepodites of C. glacialis and C. hyperboreus were rich in lipid, largely wax esters, and were well fitted to overwinter. Stage IV copepodites of C. finmarchicus were also rich in wax esters, but stage V copepodites of C. finmarchicus were less wax ester-rich. Large size increments between stage IV and V copepodites and between stage V copepodites and females were noted in C. finmarchicus. A very large increment between stage IV and V copepodites was noted for C. glacialis but the size difference between stage V copepodites and females was very small in this species. Particularly large increments were noted between stage IV and V copepodites of C. hyperboreus and also between stage V copepodites and females of this species. The very large, wax ester-rich C. hyperboreus is well adapted to survive the most extreme variations in the Arctic, in Arctic basin waters, whereas the smaller, wax ester-rich C. glacialis is adapted to survive less extreme Arctic variations, as in Arctic shelf waters. The smallest of the three, C. finmarchicus, is best adapted to survive the more predictable waters of the North Atlantic and the Barents Sea. Accepted: 3 January 2000     

Lipid composition of zooplankton in relation to the sub-arctic food web

Summary Seasonal changes in the lipid class composition and fatty acid and fatty alcohol composition of neutral lipids were determined for Calanus finmarchicus, Metridia longa and Sagitta sp. in Balsfjord, northern Norway. Similar analyses were obtained for C. hyperboreus and Parathemisto abyssorum in an adjacent fjord, Ullsfjord, in spring. C. finmarchicus, C. hyperboreus, M. longa, and Parathemisto abyssorum all contained large amounts of wax esters whereas Sagitta sp. contained small amounts of triacylglycerols and traces of wax esters. the levels of wax ester in C. finmarchicus and M. longa were highest in late autumn (respectively 88% and 84% of total lipid) and lowest in early spring (respectively 85% and 27% of total lipid). The accumulation of these neutral lipids in spring and summer is related to the feeding activity during the primary production period, while their decline in late winter is associated with the mobilisation of metabolic energy for production of gonads. The major fatty alcohols in the wax esters of C. finmarchicus and C. hyperboreus and Parathemisto abyssorum were 20:1 and 22:1 while those in the wax esters of M. longa were 14:0 and 16:0. The traces of wax esters in Saqitta were rich in 20:1 and 22:1 fatty alcohols. These analyses are consistent with C. finmarchicus and C. hyperboreus being strictly herbivorous, M. longa being more carnivorous and both Sagitta sp. and Parathemisto being highly carnivorous, probably ingesting substantial amounts of calanoid copepods.     

Distribution and diet of demersal Arctic Cod, <Emphasis Type="Italic">Boreogadus saida</Emphasis>, in relation to habitat characteristics in the Canadian Beaufort Sea

Arctic Cod (Boreogadus saida) occur throughout the circumpolar north; however, their distributions at localized scales are not well understood. The seasonal habitat associations and diet preferences across life-history stages of this keystone species are also poorly known, thereby impeding effective regulatory efforts in support of conservation objectives. The distribution of Arctic Cod in the Canadian Beaufort Sea was assessed using bottom trawling in shelf and slope habitats between 20 and 1000 m depths. Highest catch biomasses occurred at 350 and 500 m depth slope stations, coinciding with >0 °C temperatures in the Pacific–Atlantic thermohalocline and Atlantic water mass. Calanus glacialis, Calanus hyperboreus, Themisto libellula, and Themisto abyssorum were identified as key prey species in the diet of Arctic Cod, comprising approximately 86 % of total biomass in guts. Hierarchical cluster analysis with a SIMPROF test identified five statistically significant (p < 0.05) diet groups among gut samples. Arctic Cod shifted from a primarily Calanus diet at shelf stations (<200 m depth) to a Themisto diet in slope habitats (>200 m depth) coinciding with an associated increase in fish standard length with depth. Smaller Arctic Cod fed primarily on Calanus copepods and larger Arctic Cod fed primarily on the larger Themisto species. The habitat and diet associations presented here will inform knowledge of structural and functional relationships in Arctic marine ecosystems, aid in mitigation and conservation efforts, and will enhance our ability to predict the effects of climate change on the local spatial and depth associations of this pivotal marine fish.     

Feeding ecology of capelin (Mallotus villosus Müller) in West Greenland waters

Capelin (Mallotus villosus Müller) is a key pelagic mediator of energy from lower to higher trophic levels in arctic waters. This is also the case in Greenland waters, but little is known of its feeding behaviour in this region. By analysing stable nitrogen isotopes and stomach content of capelin collected along 1500?km of the Greenland west coast, this study aims to provide knowledge on capelin feeding ecology and the role that diet composition and biomass may have in generating the observed latitudinal growth differences in Greenland capelin. In total, 572 stomachs were sampled. The most dominant prey by wet weight was euphausiids (61?%) followed by amphipods (18?%) and copepods (10?%). The most common species were Thysanoessa raschii, Themisto libulla, Calanus finmarchicus and Calanus hyperboreus. Copepods dominated in smaller capelin but were replaced by euphausiids in larger fish. A similar prey shift towards euphausiids along with an increase in prey weight (relative and absolute) was seen with increasing latitude. The spatial variation in feeding pattern was supported by stable nitrogen analyses. The mean δ¹⁵N values of capelin muscle tissue for the south (60–64°N) and north (68–72°N) were 9.54?‰?±?0.72 and 12.47?‰?±?0.38 (mean?±?SD), respectively. However, when differences in isotopic baseline values (C. finmarchicus δ¹⁵N, 2.47?‰) in the two areas were taken into account, the isotope values suggest that capelin in the northern areas fed on a slightly higher trophic level higher than in the south, as would be expected with increasing importance of euphausiids. These significant feeding differences along the Greenland west coast are likely impacting capelin growth and condition as they show parallel trends along the same gradient.     

Spatial and temporal patterns of zooplankton on baleen whale feeding grounds in the southern Gulf of Maine

This study addresses the regional variation of zooplankton inthe Great South Channel area in the southern Gulf of Maine betweenCape Cod, Massachusetts and Georges Bank. This is a region ofparticular interest because of the intense concentrations ofthe copepod Calanus finmarchicus in the spring, along with theco-occurrence of right whales that feed upon these copepod aggregations.Zooplankton in the Great South Channel were sampled with theMOCNESS plankton sampler during spring 1988 and 1989 as partof the SCOPEX (South Channel Ocean Productivity Experiment)project. Zooplankton variation was addressed through comparisonsof taxonomic composition and water column abundances among towswithin and between years, and between locations with and withoutright whales. Results showed that zooplankton community compositionwas highly similar between tows within each year average percentsimilarity index (PSI) for pairwise comparisons of tows = 82.2and 88.8% in 1988 and 1989, respectively] as well as betweenyears (mean PSI = 84.4). The copepods C.finmarchicus and Pseudocalanusspp. dominated the zooplankton in terms of total water columnabundance (>94% of all zooplankton), with C.finmarchicuscomprising an average of 84% of the copepods. Highest abundancesof these copepods (particularly the younger life stages) coincidedwith a region of low-salinity transport from the north. In addition,these copepods had higher abundances in 1989, which may be relatedto the fact that low-salinity transport was approximately twiceas large in 1989 as in 1988. Given the physical dynamics ofthe region, it is possible that developing copepod populationswere adverted into the Great South Channel from the northwesternGulf of Maine via the low-salinity plume. Each year, whaleswere located in areas of both high and low copepod abundance,and tended to concentrate near the leading edge of the low-salinityplume. In 1988, there were no significant differences in zooplanktonabundance between right whale areas and non-whale areas forany taxon. In 1989, whale areas had a greater proportion ofC.finmarchicus relative to other zooplankton in 1989, whichsuggests that whales preferred regions enriched in C.finmarchicus.     

Distribution of <Emphasis Type="Italic">Calanus</Emphasis> populations in a glaciated fjord in the Arctic (Hornsund,Spitsbergen)—the interplay between biological and physical factors

The distribution and diversity of copepods of the genus Calanus were investigated in Hornsund Fjord (on the southwest coast of Spitsbergen) in summer 2001. The Bhattacharya method was used to sort individuals by species based on their prosome length. The established prosome length boundary values for the Calanus copepodid stages coincided with those defined for the Calanus species from Kongsfjorden (on the northwest coast of Spitsbergen). The predominant species in the main and inner fjord basins was Calanus glacialis, whereas Calanus finmarchicus was the prevailing species outside Hornsund. Younger copepodid stages (CI–CIII) of both species concentrated in the surface water layers (0–50∼70 m), while older copepodids (CIV–CVI females) that were ready for wintering stayed in deep layers (50∼70 m to bottom). Calanus hyperboreus was present in low numbers, predominantly as CIV, and in Hornsund deep water layers. The distribution and diversity of Calanus species complied with the notion that the marine fauna in Hornsund is of a more Arctic character than in Kongsfjorden, a fjord 260 km to the north on the west coast of Spitsbergen.     

Relationships between stomach contents and vertical migration in Meganyctiphanes norvegica, Thysanoessa raschii and T. inermis (Crustacea Euphausiacea)

Stomach contents of Thysanoëssa raschii, T. inermis andMeganyctiphanes norvegica collected in the Gulf of St. Lawrenceshowed the Thysanoëssa species fed primarily during thenight in the upper 75 m of water. M. norvegica fed on copepodswhile at their daytime depth of about 125 m and on phytoplanktonand copepods during the night above 75 m depth. M. norvegicafed on a wider range of organisms than the other two speciesduring the three sample periods of spring, fall and early winter.There was no difference in the minimum size of the cells ingestedbetween any of the species. No evidence was found of any ofthe species feeding on bottom deposits during the sample periods.     

Feeding ecology of the glacier lanternfish Benthosema glaciale (Actinopterygii, Myctophidae) in the Flemish Cap (North Atlantic Ocean)

The feeding dynamics of the glacier lanternfish Benthosema glaciale were studied during the summer of 2010 in the Flemish Cap. B. glaciale constituted a majority of the deep scattering layer (DSL), which was located between 300 and 650 m during daylight hours; at night, a part of the DSL migrated to the surface. B. glaciale is a zooplanktivore, feeding primarily on copepods (Calanus hyperboreus, Pareuchaeta norvegica, Metridia longa and Calanus finmarchicus), followed by amphipods (Themisto compressa) and krill (primarily Nematoscelis spp.). Although crustaceans dominated the diet, other invertebrates, such as chaetognaths, gastropods, polychaetes, ostracods and appendicularians, also contributed. The geographical differences in the composition of the diet resulted from the association of prey with distinct water masses. In the colder water at the north of the bank, Arctic species represented a higher proportion of the diet, but this situation was reversed in areas influenced by the warmer water from the south. B. glaciale fed more intensively towards the centre of the Flemish Cap. The diet of B. glaciale shifted ontogenetically, showing increasing prey size and prey diversity with increasing predator size.     

Food ingestion and digestive transit time in the euphausiid Meganyctiphanes norvegica as a function of animal size

Laboratory experiments with Meganyctiphanes norvegica of differentsizes (7 to 70 mg dry) fed on Artemia salina show that the dailyspecific ingestion rate varies with animal weight accordingto a power law with a negative exponent of -0.58. This relationis used to calculate the production rate of faeces which ishigher in the smaller individuals when expressed as a percentageof animal weight; a comparison of the M. norvegica data withpublished data for Calanus helgolandicus indicates that thisrate is higher for the smaller species. Under the experimentalconditions used the digestive transit time of food in M. norvegicais appreciably shorter in smaller animals (15 minutes versus30 minutes). The data, combined with other data previously obtainedfor the same ipecies, show that the metabolism of active, well-fedindividuals is about three times higher than the standard metabolism.