Spawning areas and spawning period of the North-east Arctic haddock [HELP 25}

Spawning of North-East Artic haddock occurs on the Norwegian continental slope. The location of the spawning grounds is, however, diffuse. This is mainly due to difficulties in identifying haddock eggs. In this work this problem is solved by using the biochemical genetical approach of electrophoresis. The results from haddock egg and trawl surveys in April -May 1987 and 1988 are analysed in relation to previous knowledge of haddock egg distribution and mature fish. Gonad maturity is compared to the distribution of egg developmental stages i n different regions. Both horizontal and vertical gradients in gonad maturity of haddock are revealed. Most of the Tromsøflaket area from Nordkapp to near the shelf edge bordering the Norwegian Sea (Norskehavet) are inhabited by immature haddock. An increase in abundance of mature fish takes place in the western part of the shelf. The main spawning areas of North-East Arctic haddock seems to be the southeastern part of the continental slope of Tromsgflaket at depths from 303 to 600 m and temperatures between 4ºand 6º C. Other spawning areas are found in Vestfjorden and over the continental slope from Tromsøflaket south to Rosttunga. The spawning in Vestfjorden seems to take place a t depths shallower than 200 m, but within the same temperature limits . Spawning seems to start at the beginning of April, reaches its maximum at the end of the month and ends during the first half of May. Very little spawning is recorded on the shelf and the continental slope from Røsttunga to 64º N. Spawning i n the area 62-64º N (Møre) is supposed to origin from a local stock. The onset of this spawning seems to take place a week or two earlier than what was observed further north. A distinct bimodal distribution of larvae sampled in July 1987 indicate a possible influx of haddock larvae to the Norwegian coast which might originate from a population different from the North-East Arctic haddock

Vertical distribution of fish and krill beneath water of varying optical properties

The distribution of acoustical scattering layers of fish and krill changed markedly in concert with fluctuating fluorescence (chlorophyll a) in upper waters, possibly due to a varying 'shadow effect'. Beneath clear waters on the outer Norwegian shelf (about 300 m depth), mesopelagic fish (Maurolicus muelleri) were located at approximately 150 to 200 m by day. Krill (mainly Thysanoessa inermis) was primarily found below the mesopelagic fish and above planktivorous demersal fish (Norway pout Trisopterus esmarkii). The vertical distributions changed abruptly across a front into water with less Light penetration associated with increased fluorescence (chlorophyll a). Mesopelagic fish ascended by about 100 m accompanied by a rise of krill. Demersal fish left the benthic boundary zone, with ascending Norway pout foraging in the lower part of the krill layer. We suggest that the intermediate light conditions inside the front provided an 'antipredation window' (sensu Clark & Levy 1988: Am Nat 131:271-290) and thereby favorable feeding conditions for the planktivore. These results indicate that properties of upper layers may impact plankton and fish distributions and their predator-prey interactions throughout the water column on continental shelves

Ecology of mesozooplankton across four North Atlantic basins

A comparative study of the mesozooplankton in four North Atlantic basins is presented. During a trans-Atlantic expedition with R/V G.O. Sars in May and June 2013, the Norwegian Sea, Iceland Sea, Irminger Sea and Labrador Sea was surveyed twice on a round trip from Bergen, Norway to Nuuk, Greenland. Mesozooplankton samples of biomass, species composition and vertical distribution were obtained with WP2 and MOCNESS plankton nets, in addition to in situ data obtained from a Video Plankton Recorder (VPR) and Optical Plankton Counter (OPC) mounted on a submersible towed vehicle. Size-fractionated biomass samples showed that the Norwegian Sea had the highest biomass of small mesozooplankton (180–1000 μm), while Irminger and Iceland Seas had the highest biomass of the medium (1000–2000 μm) and largest (>2000 μm) size fractions, respectively. The Icelandic Sea large fraction biomass was dominated by Amphipods, Chaetognaths, Krill and Calanus hyperboreus. The Labrador Sea had the lowest total mesozooplankton biomass. A total of 9 different species/groups were found to comprise the 5 most numerically dominant species/groups across all basins, with Oithona spp. being the most common genus in all basins. C. finmarchicus was, as expected, found to be the most numerically common species of the Calanus complex in all basins, but the stage composition varied markedly between basins with young copepodite stages dominating only in the Labrador and central Norwegian Seas. In terms of both abundance and biomass, the Iceland Sea had a higher fraction of dominating mesozooplankton distributed below 200 m. The highest average particle density per 25 m interval was registered in the Norwegian Sea during daytime between 25-50 m (OPC data). In the Labrador and Irminger Seas, total estimated particle densities in the upper 50 m were lower and the particle densities peaked at intermediate sizes (1–3 mm). In all basins there were differences in the particle densities estimated between day and night. Based on VPR data, the Irminger and Iceland Seas had the highest density of copepods registered in the upper 200 m, whereas in the Labrador Sea, the highest average copepod densities were registered at depth. Densities of gelatinous organisms were at least an order of magnitude higher in the Labrador and Irminger Seas than in the Iceland Sea.acceptedVersio

Vertical distribution and migration of mesopelagic scatterers in four north Atlantic basins

We studied vertical distribution and diel vertical migration (DVM) behaviour of mesopelagic acoustic scattering layers in relation to environmental conditions in the Norwegian Sea, the Iceland Sea, the Irminger Sea, and the Labrador Sea. Distinct mesopelagic scattering layers were found in all basins, but the daytime depth of the layers varied between basins. The results suggested that daytime vertical distribution across the four basins are strongly influenced by optical conditions. DVM occurred in all basins, and since daytime vertical distribution was influenced by optical conditions, it affected the amplitude of vertical connectivity. We used the proportion of the acoustic backscatter that migrated vertically into the epipelagic zone as a proxy for active vertical flux to the mesopelagic. The proportion of micronekton backscatter participating in the vertical migrations varied between the basins, with the highest and lowest vertical connectivity in the Norwegian Sea and the Iceland Sea respectively. We conclude that a more than 8-fold reduction in backscatter flux in the Iceland Sea was attributable to optical conditions there.publishedVersio

Modeling the target strength of Meganyctiphanes norvegica

Abstract only. Journal home page: http://scitation.aip.org/jasa

Multinational large scale krill synoptic survey in CCAMLR Area 48 in 2019-survey plan and protocol for consideration by SG-ASAM 2018

The objective for the Multinational Large-Scale Krill Synoptic Survey in CCAMLR area 48 3 in 2019 is to provide an updated estimate of the biomass of Antarctic krill (Euphausia 4 superba) used in models to estimate sustainable yield. The planned survey follows, as close 5 as possible, the design of the CCAMLR 2000 survey, that was undertaken in the year 2000. 6 The basis for comparisons will depend on the degree of coverage and methodology and 7 equipment available. The survey will involve the collaborative efforts of Norway, 8 Association of Responsible Krill fishing companies (ARK: companies from Norway, Korea, 9 China and Chile), United Kingdom, Ukraine, Korea and China, and hopefully also other 10 nations that still needs to confirm their participation. 11 The current survey plan organization is presented for consideration by SG-ASAM. Norway 12 has volunteered to co-ordinate the survey with other members dedicating personnel to 13 specific tasks. It is requested that members who has already made commitments on ship time, 14 also allocate contact personnel as proposed. 15 This paper has been developed after a wider consultation extending beyond the authors list. It 16 discusses some specific organizational and technical challenges to be considered by SG17 ASAM. We request advice from ASAM on “minimum requirements” regarding acoustic 18 instrumentation and sampling gear to achieve approximate consistency with the CCAMLR 19 B0 data collection protocol.Multinational large scale krill synoptic survey in CCAMLR Area 48 in 2019-survey plan and protocol for consideration by SG-ASAM 2018publishedVersio

Acoustic manual for the krill synoptic survey in 2019

The previously presented document at the 2018 ASAM WG meeting (ASAM-18-07) described a design and plans for a synoptic krill acoustic survey in CCAMLR area 48 in 2019. The survey involves the collaborative efforts of Norway, Association of Responsible Krill fishing companies (ARK: companies from Norway, Korea, China and Chile), the United Kingdom, Ukraine, Korea and China, all of whom have confirmed a commitment of survey ship time. With these commitments it is feasible to implement all transects occupied during the 2000 survey. This document is a draft survey manual, produced at the recommendation of the 2018 ASAM meeting, and describes acoustic procedures, acoustic reporting - analysis procedures and contingency plans.Acoustic manual for the krill synoptic survey in 2019publishedVersio

Comparison of two multiple plankton samplers: MOCNESS and Multinet Mammoth

To ensure an optimal continuation of a long time series of zooplankton monitoring surveys, two types of equipment for depth-stratified mesozooplankton sampling were compared. The Institute of Marine Research (Norway) has applied the MOCNESS with good results since 1985, but recent events have made it necessary to change to the Multinet Mammoth. During a cruise in March 2019, both sampling devices were calibrated before 17 paired deployments of the 2 gears were undertaken. During each deployment, three nets and depth-strata covering ~ 425–200, 200–100, and 100–0 m were sampled. All samples were size-fractionated or taxonomically fractionated into 10 different biomass categories. The results revealed no significant differences between the two gears when comparing total depth-integrated biomass (2.46 ± 0.36 vs. 2.61 ± 0.59 gDW m−2) or depth-integrated biomass of any specific biomass category. Running paired t-tests separately for all combinations of biomass categories and nets, the differences were only significant for zooplankton biomasses in the 180–1000 μm size fraction and only for Net 2. Possible reasons for this result are discussed in the paper. Gears produced similar catches whether sampling during day or night. We conclude that the MOCNESS and Multinet Mammoth in this study provided comparable results regarding abundances of various zooplankton categories.publishedVersio

Initial collateral measurements of some properties of Calanus finmarchicus

In general, acoustic quantification of zooplankton such as Calanus finmarchicus requires the use of models, among other reasons, to aid in the interpretations of data collected on animals whose scattering properties change with development stage, season, and other environmentally linked factors. In conjunction with a project to determine acoustic scattering signatures of zooplankton and fish, a study is being performed to measure physical, morphometric, and biochemical properties of selected euphausiid species and Calanus finmarchicus. An important feature of this study is the performance of a suite of measurements on animals collected at the same time and place. The measurement methods being used to study Calanus are presented here together with results from the initial field experiment. The criticism of interested parties is solicited