European Continental Slope Research Articles

Studies of particle fluxes of sedimentary matter along multiyear transoceanic section in northern Atlantic and Arctic interaction area

New data on the particle fluxes of sedimentary matter and its main components at the meridional section along 59°30' N in the North Atlantic under the influence of multidirectional transfer of water masses are given. The material for the study was collected for two years from July 2015 to July 2017 using sediment traps installed as part of four automatic deep-water sedimentary observatories. In the subsurface layer, the annual variation of the fluxes and the change in the composition of the sinking matter are determined by the primary production. Near-bottom fluxes of sedimentary matter on the slopes of the Reykjanes ridge are formed under conditions of water masses and, respectively, suspended particulate matter transfer in a south-westerly direction along the ridge from the Iceland-Faeroe and Greenland-Iceland rises. There is a reverse directional transfer of matter at the foot of the European continental slope. The composition of the sinking matter is dominated by the biogenic component, the proportion of which decreases with depth due to dissolution, and in winter due to the weakening of the biological activity of the upper active layer. The role of lithogenic matter is maximal in the bottom layer, including due to the supply of material from the bottom.

Studies of Sedimentary Matter Fluxes along a Long-Term Transoceanic Transect in the North Atlantic and Arctic Interaction Area

New data are presented on sedimentary matter fluxes and its main components along a meridional transect (59°30′ N) in the North Atlantic under the effect of multidirectional transport of water masses. The material for the study was collected July 2015 to July 2017 using sediment traps installed as parts of four automatic deep-water sedimentary observatories. In the subsurface layer, the annual variation in fluxes and composition of sinking material are determined by primary production. Bottom sedimentary material fluxes on the slopes of the Reykjanes Ridge are formed under conditions of transport of water masses and, accordingly, suspended particulate matter to the southwest along the ridge from the Iceland–Faroe and Greenland–Iceland rises. There is back transfer of material at the foot of the European continental slope. Sinking material is dominated by the biogenic component, the proportion of which decreases with depth due to dissolution and to less biological activity in the upper layer in winter. The role of lithogenic material is maximum in the bottom layer, where material is additionally supplied from the bottom.

Nutrient-driven poleward expansion of the Northeast Atlantic mackerel (Scomber scombrus) stock: A new hypothesis

Abstract The Northeast Atlantic mackerel (Scomber scombrus) stock has increased and expanded its summer feeding migration west- and northwards since 2006, entailing large geopolitical challenges for the countries harvesting this species. A common perspective is that climatic warming opens up new regions for biota in the north. It has also been suggested that the presently large pelagic fish stocks deplete prey resources in the eastern North Atlantic during their summer feeding phase, forcing the stocks west towards the Irminger Sea in their search for food. Here, we suggest that the declining nutrient (silicate) concentrations observed along the northern European continental slope reduce primary and thus secondary production, exacerbating food scarceness in the east and adding to the incentive to migrate westward. The new westward feeding route requires that the fish cross the Iceland Basin, which during the summer season quickly becomes nutrient-depleted and thus might act as a barrier to migration after the spring bloom. Using mackerel and zooplankton abundance data from the International Ecosystem Summer Surveys in the Nordic Seas, we suggest that the oligotrophic waters in the central Iceland Basin force the fish to migrate through a narrow ‘corridor’ along the south Iceland shelf, where nutrients are replenished and both primary and secondary production are higher.

Springtime zooplankton size structure over the continental shelf of the Bay of Biscay

Abstract. Linking lower and higher trophic levels requires special focus on the essential role played by mid-trophic levels, i.e., the zooplankton. One of the most relevant pieces of information regarding zooplankton in terms of flux of energy lies in its size structure. In this study, an extensive data set of size measurements is presented, covering parts of the western European continental shelf and slope, from the Galician coast to the Ushant front, during the springs from 2005 to 2012. Zooplankton size spectra were estimated using measurements carried out in situ with the Laser Optical Plankton Counter (LOPC) and with an image analysis of WP2 net samples (200 μm mesh size) performed following the ZooScan methodology. The LOPC counts and sizes particles within 100–2000 μm of spherical equivalent diameter (ESD), whereas the WP2/ZooScan allows for counting, sizing and identification of zooplankton from ~ 400 μm ESD. The difference between the LOPC (all particles) and the WP2/ZooScan (zooplankton only) was assumed to provide the size distribution of non-living particles, whose descriptors were related to a set of explanatory variables (including physical, biological and geographic descriptors). A statistical correction based on these explanatory variables was further applied to the LOPC size distribution in order to remove the non-living particles part, and therefore estimate the size distribution of zooplankton. This extensive data set provides relevant information about the zooplankton size distribution variability, productivity and trophic transfer efficiency in the pelagic ecosystem of the Bay of Biscay at a regional and interannual scale.

“The Ekman Drain”: a conduit to the deep ocean for shelf material

A long (167 days) acoustic Doppler current profiler time series from the European continental slope west of Scotland has been analysed to investigate the influence of bathymetric steering on the slope current and the extent of down-slope transport in the bottom boundary layer. Within an interior region between the surface and bottom boundary layers, the direction of the flow is found to be remarkably consistent as required by the Taylor-Proudman theorem for geostrophic flow. The mean value of this interior flow direction is taken to be the effective direction of the bathymetry in controlling the geostrophic flow and so defines the rotation of coordinates required to determine along and cross-flow transports. Within a bottom boundary layer (BBL) of thickness ~100 m, the direction of the flow was deflected increasingly to the left with the mean veering angle ~12.5° at 12 mab and a down-slope speed of 2.6 cm s−1. The corresponding integrated transport (the “Ekman drain”) had an average value of ~1.6 m2 s−1 over the full observation period. This down-slope flow was significantly correlated (at 0.1 % level), with the stress applied by the along-slope flow although with considerable scatter (r.m.s. ~1 m2 s−1) which suggests the influence of other forcing mechanisms. Combining the BBL volume transport with an estimate of the mean concentration of suspended particulate material indicates an annual down-slope flux of 3.0 ± 0.6 tonnes m−1 year−1, of which ~0.36 ± 0.1 tonnes m−1 year−1 is carbon. Biogeochemical measurements indicate that the carbon flux in the Ekman drain predominates over settlement of organic material through the water column over the slope and provides for relatively rapid delivery of material to deep water.

Sediment community responses to marine vs. terrigenous organic matter in a submarine canyon

Abstract. The Whittard Canyon is a branching submarine canyon on the Celtic continental margin, which may act as a conduit for sediment and organic matter (OM) transport from the European continental slope to the abyssal sea floor. In situ stable-isotope labelling experiments were conducted in the eastern and western branches of the Whittard Canyon, testing short-term (3–7 days) responses of sediment communities to deposition of nitrogen-rich marine (Thalassiosira weissflogii) and nitrogen-poor terrigenous (Triticum aestivum) phytodetritus. 13C and 15N labels were traced into faunal biomass and bulk sediments, and the 13C label traced into bacterial polar lipid fatty acids (PLFAs). Isotopic labels penetrated to 5 cm sediment depth, with no differences between stations or experimental treatments (substrate or time). Macrofaunal assemblage structure differed between the eastern and western canyon branches. Following deposition of marine phytodetritus, no changes in macrofaunal feeding activity were observed between the eastern and western branches, with little change between 3 and 7 days. Macrofaunal C and N uptake was substantially lower following deposition of terrigenous phytodetritus with feeding activity governed by a strong N demand. Bacterial C uptake was greatest in the western branch of the Whittard Canyon, but feeding activity decreased between 3 and 7 days. Bacterial processing of marine and terrigenous OM were similar to the macrofauna in surficial (0–1 cm) sediments. However, in deeper sediments bacteria utilised greater proportions of terrigenous OM. Bacterial biomass decreased following phytodetritus deposition and was negatively correlated to macrofaunal feeding activity. Consequently, this study suggests that macrofaunal–bacterial interactions influence benthic C cycling in the Whittard Canyon, resulting in differential fates for marine and terrigenous OM.

Phylogeographical history of the white seabream Diplodus sargus (Sparidae): Implications for insularity

Partial sequences of the mitochondrial control region and its comparison with previously published cytochrome b (cyt-b) and microsatellite data were used to investigate the influence of island isolation and connectivity on white seabream genetic structure. To achieve this, a total of 188 individuals from four island localities (Castellamare and Mallorca, Mediterranean Sea; Azores and Canary Islands, Atlantic Ocean) and five coastal localities (Banyuls, Murcia and Tunisia, Mediterranean Sea; Galicia and Faro, Atlantic Ocean) were analysed. Results showed high haplotype diversity and low to moderate nucleotide diversity in all populations (except for the Canary Islands). This pattern of genetic diversity is attributed to a recent population expansion which is corroborated by other results such as cyt-b network and demographic analyses. Low differentiation among Mediterranean/Atlantic and coastal/island groups was shown by the AMOVA and FST values, although a weak phylogeographic break was detected using cyt-b data. However, we found a clear and significant island/distance effect with regard to the Azores islands. Significant genetic differentiation has been detected between the Azores islands and all other populations. The large geographical distance between the European continental slope and the Azores islands is a barrier to gene flow within this region and historic events such as glaciation could also explain this genetic differentiation.

Estimating Synaphobranchus kaupii densities: Contribution of fish behaviour to differences between bait experiments and visual strip transects

Kaup's arrowtooth eel Synaphobranchus kaupii is a small-bodied fish and an abundant inhabitant of the European continental slope. To estimate its local density video information using the remotely operated vehicle (ROV) Victor 6000 were collected at three locations in the Bay of Biscay slope. Two methods for estimating local densities were tested: strip transect counts and bait experiments. For bait experiments three behaviour types were observed in about equal proportions for individuals arriving near the seafloor: moving up the current towards the ROV, moving across the current and drifting with the current. Visible attraction towards the bait was the highest for individuals swimming against the current (80%) and about equally low for the other two types (around 30%); it did not depend on current speed nor temperature. Three main innovations were introduced for estimating population densities from bait experiments: (i) inclusion of an additional behaviour category—that of passively drifting individuals, (ii) inclusion of reaction behaviour for actively swimming individuals and (iii) a hierarchical Bayesian estimation framework. The results indicated that about half of individuals were foraging actively of which less than one third reacted on encountering the bait plume and the other half were drifting with the current. Taking account of drifting individuals and the reaction probability made density estimates from bait experiments and strip transects more similar.

The importance of the permanent thermocline to the cold water coral carbonate mound distribution in the NE Atlantic

A prominent feature of the NW European continental slope is the presence of numerous cold water coral carbonate mounds that are clustered in a number of provinces. These provinces occupy a relatively narrow depth range along the continental slope: 95% of all coral carbonate mounds identified on the Irish seabed have their mound bases between 500 and 1000 m water depths, with a peak in distribution at ∼ 650 m water depth. The distribution in mound base depths is skewed with a tail extending from the maximum at 650 m to deeper depths. This distribution brackets the depth of the permanent thermocline in the NE Atlantic (600–1000 m) formed below the base of the winter mixed layer. It is shown that the permanent thermocline is associated with the strongest residual near seabed current flow, with typical residual current speeds up to 2–3 times larger at the thermocline depth compared to other depths. The strong vertical density gradient associated with the permanent thermocline, together with the steep continental slope at those depths, also enhances the energy of certain periodic motions such as internal waves and baroclinic tidal currents. These dynamic conditions favour mound growth through the promotion of significant along-slope sediment transport and also provide large across-slope sediment movement and organic matter fluxes. The stability of the thermocline structure is likely the key in providing favourable conditions over long time scales that allow mound growth through sediment baffling processes.

The North Atlantic subpolar gyre regulates the spawning distribution of blue whiting (Micromesistius poutassou)

The spawning stock of blue whiting ( Micromesistius poutassou ), an economically important pelagic gadoid in the North Atlantic Ocean, increased threefold after 1995. The reproductive success of the stock is largely determined during the very early stages of life, but little is known about the spawning dynamics of this species. Here we show that the spawning distribution of blue whiting is variable, regulated by the hydrography west of the British Isles. When the North Atlantic subpolar gyre is strong and spreads its cold, fresh water masses east over Rockall Plateau, the spawning is constrained along the European continental slope and in a southerly position near Porcupine Bank. When the gyre is weak and conditions are relatively saline and warm, the spawning distribution moves northwards along the slope and especially westwards covering Rockall Plateau. The apparent link between the spawning distribution and the subpolar gyre is the first step towards understanding the reproduction variability, which currently is the main challenge for appropriate management of the blue whiting stock.

Interactions between sediment chemistry and frenulate pogonophores (Annelida) in the north-east Atlantic

The small frenulate pogonophores (Annelida: Pogonophora a.k.a. Siboglinidae) typically inhabit muddy sediments on the continental slope, although a few species occur near hydrothermal vents and cold seeps. We present data on the distribution and habitat characteristics of several species on the European continental shelf and slope from 48°N to 75°N and show how the animals interact with the chemistry of the sediments. The environments inhabited include: shallow (30 m), organic-rich, fjord sediments; slope sediments (1000–2200 m) and methane seeps at 330 m depth. All the species studied obtain nutrition from endosymbiotic bacteria. They take up reduced sulphur species, or in one case, methane, through the posterior parts of their tubes buried in the anoxic sediment. We conclude that most species undertake sulphide ‘mining’, a mechanism previously demonstrated in the bivalves Lucinoma borealis and Thyasira sarsi. These pogonophores participate in the sulphur cycle and effectively lower the sulphide content of the sediments. Our results show that the abundance of frenulate pogonophores increases with increasing sedimentation and with decreasing abundance of other benthos, particularly bioturbating organisms. The maximum sustainable carrying capacity of non-seep sediments for frenulate pogonophores is limited by the rate of sulphate reduction.

TAXONOMY AND DISTRIBUTION OF THE UVIGERINA PEREGRINA PLEXUS IN THE TROPICAL TO NORTHEASTERN ATLANTIC

Uvigerina peregrina Cushman 1923 and related taxa are extensively used for paleoceanographical studies. A high degree of inter- or intra-specific variability leaves the status of these species unclear and has hampered sound paleoenvironmental interpretations to date. The species concept and diagnostic features of Uvigerina peregrina and the closely related Uvigerina pigmea d’Orbigny 1826, Uvigerina peregrina parva Lutze 1986 are re-assessed in this paper. Uvigerina sp. 221 Lutze 1986 is formally described and named Uvigerina celtica n. sp. The overall size of the tests, the length/width ratio, and the morphology of costae are considered key diagnostic features while the presence or absence of spines is of minor importance for species characterization. Geographic and depth distributions of living Uvigerina taxa are described using faunal census data from the northwest African and western European continental shelf and slope from the 2 ° S to 70 ° N, and from the Caribbean. The regional distribution and inferred population dynamics reveal that Uvigerina peregrina, Uvigerina celtica n. sp. and Uvigerina pigmea are indeed different species. Uvigerina peregrina parva is most likely a subspecies of Uvigerina peregrina and not an ecophenotype.

Compositional variability of ice‐rafted debris in Heinrich layers 1 and 2 on the northwest European continental slope identified by environmental magnetic analyses

AbstractThe composition of ice‐rafted debris (IRD) within a sediment core from the European continental slope (core OMEX‐2K; 49° 5′ N, 13° 26′ W) has been examined using environmental magnetic analyses. The data demonstrate compositional variability of the IRD within Heinrich layers 2 (H2) and 1 (H1) and these differences are most readily explained by changes in the contribution of different IRD sources to the core site. Some IRD within the main Heinrich layers show magnetic signatures that are similar to IRD derived from the Laurentide ice sheet found in cores from within the main North Atlantic IRD‐belt. In contrast, other IRD‐rich layers, both prior to and within the main Heinrich layers, demonstrate different magnetic behaviour, suggesting a contribution from a non‐Laurentide sourced IRD, most likely derived from ice streams discharging from northeast Atlantic ice sheets such as the British and Fennoscandian ice sheets. These data are consistent with published compositional data from the same core and, given the rapid, highly sensitive and non‐destructive nature of the method, suggest that environmental magnetic analysis has considerable potential for characterising IRD materials within Heinrich layers for the purposes of defining provenance. Copyright © 2006 John Wiley & Sons, Ltd.

Integrated Use of 3D seismic in field development, engineering and drilling: examples from the shallow section

Abstract Examples from exploration acreage and field developments across the glaciated Northwest European Continental Shelf and Slope demonstrate the usefulness of conventional three-dimensional (3D) seismic data to spatially image geological features. Compared to previous grid-based two-dimensional (2D) seismic this allows fundamentally more confident identification, mapping and prediction of geotechnical conditions which is important to ensure safe, efficient engineering and drilling operations. Whilst of immense benefit, the paper argues that the 3D seismic data often do not meet the full expectations, particularly in terms of critical vertical resolution and accurate depth prediction requirements. To illustrate the limitations, direct comparison is made between conventionally acquired 3D and HiRes 2D seismic data. Whilst industry funding to support innovative HiRes 3D seismic acquisition remains sparse, much can be achieved by the careful integration and interpretative calibration of the 3D and HiRes 2D seismic datasets. Three field development case studies illustrate this. Short offset trace correction and reprocessing of the 3D seismic data followed by limited, target specific HiRes 2D seismic, calibrated where possible with drilling or other geological data, is an optimal cost-effective approach.

Ocean structure and climate (Eastern North Atlantic): in situ measurement and remote sensing (altimeter)

Structure and climate of the east North Atlantic are appraised within a framework of in situ measurement and altimeter remote sensing from 0°–60°N. Long zonal expendable bathythermograph/conductivity–temperature–depth probe sections show repeating internal structure in the North Atlantic Ocean. Drogued buoys and subsurface floats give westward speeds for eddies and wavelike structure. Records from longterm current meter deployments give the periodicity of the repeating structure. Eddy and wave characteristics of period, size or wavelength, westward propagation speed, and mean currents are derived at 20°N, 26°N, 32·5°N, 36°N and 48°N from in situ measurements in the Atlantic Ocean. It is shown that ocean wave and eddy-like features measured in situ correlate with altimeter structure. Interior ocean wave crests or cold dome-like temperature structures are cyclonic and have negative surface altimeter anomalies; mesoscale internal wave troughs or warm structures are anticyclonic and have positive surface height anomalies. Along the Eastern Boundary, flows and temperature climate are examined in terms of sla and North Atlantic Oscillation (NAO) Index. Longterm changes in ocean climate and circulation are derived from sla data. It is shown that longterm changes from 1992 to 2002 in the North Atlantic Current and the Subtropical Gyre transport determined from sla data correlate with winter NAO Index such that maximum flow conditions occurred in 1995 and 2000. Minimum circulation conditions occurred between 1996–1998. Years of extreme negative winter NAO Index result in enhanced poleward flow along the Eastern Boundary and anomalous winter warming along the West European Continental Slope as was measured in 1990, 1996, 1998 and 2001.

Circulation of the eastern North Atlantic and north‐west European continental shelf – a hydrodynamic modelling study

As part of the interdisciplinary investigation of Calanus finmarchicus migrations between oceanic and shelf areas off north‐west Europe (the ICOS project), a three‐dimensional, prognostic baroclinic circulation model system, consisting of a coarse and a nested fine scale model, was constructed. The aim was to simulate the flow fields around Iceland, the Faroe Islands and the north‐west European continental shelf and slope, including the northern North Sea. The coarse scale model covered the northern North Atlantic and provided the far field flow to the finer scale model. The latter was initialized and forced with climatological seasonal (winter and spring) means of temperature, salinity, river run‐off, and other parameters necessary for the calculation of heat fluxes. Seasonal average simulations of flow and hydrographic conditions were performed, together with simulations of specific scenarios of uniform wind forcing from different directions. A feature common to all the results was a topographically guided northwards flow along the continental shelf edge, with a southwards counter‐flow in the vicinity of the Faroe–Shetland Channel. The extent and strength of the shelf edge current, of its counter flow, and of the re‐circulation cell in the northern North Sea, were dependent on the prevailing wind direction. The modelling results were consistent with the accepted circulation patterns in the area, and a comparison with field measurements in the Faroe–Shetland Channel showed that the main characteristics of the flow were well replicated, although the estimated strength of the slope current was somewhat less than in the field observations.

Late-summer mass deposition of gelatinous phytodetritus along the slope of the N.W. European Continental Margin

In the period 1993–1995 the OMEX area has been visited 3 times to address the question of across-slope transport of suspended matter from the shelf to the deep sea. By analyzing phytopigments and nucleic acids in the sediment and water of the N.W. European Continental slope and rise seasonal patterns of benthic food input were investigated and relation between input and the structure and activity of the benthic community were explored. Chloropigments in the surface sediments indicated that a spring bloom effect could be traced down to about 2500 m. During late August 1995 heavy deposits of gelatinous matter, characterized by high concentrations of chloropigments and nucleic acids, were detected all over the ocean floor of the outer slope and continental rise below 3500 m. It is estimated that this mucus layer had a carbon load of 250 mmol C m −2 over an area of 50,000 km 2. The recent state of the mucus allowed us to search for its origin. Characteristic pigment composition and the presence of coccoliths pointed to prymnesiophytes (coccolithophorids) as a major contributor, but dinoflagellates (peridinin) and green algae (chlorophyll-b, lutein) must have contributed as well. Simultaneous observations of the overlying water column, deep chlorophyll maximum, revealed the presence of a coccolithophorid bloom in a recent stage of disintegration at St. III. An obvious relation with the mucus carpet, however, could not be indicated. This, and the significant differences in pigment composition and pigment ratios at the various deep stations lead us to understand that the extended mucus field at the Celtic slope originates from different, more or less synoptically occurring surface blooms. The presence of large `vacuum-cleaning' sea-cucumbers is considered indicative of the occurrence of phytodetritus pulses.

The boundary circulation along the European continental slope as transport vehicle for two calanid copepods in the Bay of Biscay

The copepod fauna south-west of the British Isles includes a number of species which have their centre of distribution in the subtropical or tropical Atlantic. Among these, some species appear to be faunistically linked with the Iberian continental slope or slope waters even farther south along the NE Atlantic margin. It seems that these species reach their north-eastern range by means of poleward-flowing currents. For example, Calanoides carinatus has deep-living resting stages and ascends to surface waters only during its reproductive period, which is short at northern latitudes. Its main dwelling layers along the west Iberian continental slope cover the poleward-flowing undercurrent and the Mediterranean outflow water underneath. Part of the poleward flow regime tends to follow the slope bathymetry, i.e. it bends eastwards into the Bay of Biscay along northern Spain. Another part separates from the continental slope at Cape Finisterre and crosses the Bay of Biscay, approaching the continental slope at about 47° N, where it joins the north-westward flowing slope currents again. Because of its preference for the deeper layers during the long resting phase it is assumed that resting C. carinatus drifts mainly with the northward branch of the Mediterranean outflow water and penetrates only slightly into the inner Bay of Biscay. In contrast, Calanus helgolandicus has, on average, a shallower vertical distribution. Reproductively active individuals occur in the surface layers off western Iberia throughout the year. Here it drifts presumably northwards during late autumn and winter, but is recirculated southwards during late spring and summer. Due to advection with both the intermediate undercurrent and the variable near-surface currents, Calanus helgolandicus occurs more commonly in the inner Bay of Biscay than C. carinatus.

Taxonomy of and biological notes on the bivalve genusMicrogloma, with comments on protobranch nomenclature

Abstract The protobranch bivalve genus Microgloma Sanders & Allen, 1973 includes 3 or 4 minute species, shell length 0.85–1.1 mm. They are progenetic and their systematic position proposed herein, in the Nuculanidae (Nuculanoidea), is concluded from their similarity to young specimens of that family and sperm morphology. The genus was hitherto classified in Pristiglomidae (Nuculoidea). Microgloma pusilla (Jeffreys, 1879) occurs on the European continental shelf and slope from Iceland and Norway to the Mediterranean Sea at depths between 200 and 1200 m. Microgloma lumidula (Monterosato, 1880) (new synonym: M. lumerae Sanders & Allen, 1973) occurs from the Bay of Biscay and the Mediterranean Sea to the Canary Islands at depths between 200 and 2351 m. Phaseolus guilonardi Hoeksema, 1993 from the Netherlands and Atlantic France, is tentatively included in Microgloma (new combination). A few live M. pusilla were kept in the laboratory for nearly four years and the development of five young born there, was foll...

Age and growth rates of North Atlantic eel larvae (Anguilla spp.), based on published length data

The age of glass eels arriving at the European coasts is estimated by different authors to range from 3/4 to 3+years; some of these estimates are based on counts of “daily rings”. The present study reviews published data on North Atlantic length frequency distributions. The only years for which larvae samples are available from the spawning area to the European continental slope are 1979 and, to a certain extent, also 1922. In the spring of both years, length frequency distributions exhibited two distinct maxima which are considered to belong to the AG 0 (mean lengths 12 and 18 mm for 1979 and 1922, respectively) and the AG I (47 and 44 mm). In addition, a third, less distinct maximum is visible and the existence of an AG II must be considered. Growth during the first year of life is calculated using the means of total lengths of sufficiently large samples, collected with progressing season, of the years 1920, 21, 22, 79, 81. From the resulting linear regressions forAnguilla anguilla until the beginning of winter, a daily length increase of 0.15 mm was estimated. Growth ofA. rostrata was faster (0.22 mm·day−1) Daily length increase ofA. anguilla in winter was only 0.03 mm; during a possible second summer 0.06–0.09 mm·day−1 and during a possible third summer considerably less. There is a length increase of the European eel larvae from south to north, known also from glass eels, which makes evaluation of length increase from west to east even more difficult. A higher age of glass eels in the north than in the south is therefore likely.