Ichthyoplankton and pelagic fish assemblages in the Greenland Sea in 2017. Technical Report No. 110

Ichthyoplankton and pelagic fish assemblages in the Greenland Sea in 2017 Caroline Bouchard Technical Report no. 110 Greenland Institute of Natural Resources 12 February 2020 1 Title: Ichthyoplankton and pelagic fish assemblages in the Greenland Sea in 2017 Author: Caroline Bouchard Publisher: Greenland Institute of Natural Resources Date of publication: 2020 Financial support: Northeast Greenland Environmental Study Program Danish Centre for Environment and Energy at Aarhus University Greenland Institute of Natural Resources Government of Greenland - Environmental Agency for Mineral Resource Activities Cover photo: Caroline Bouchard ISSN: 1397-3657 ISBN: 87-91214-88-2 EAN 9788791214882 Web: http://www.natur.gl/publikationer/tekniske rapporter Citation: Bouchard (2020) Ichthyoplankton and pelagic fish assemblages in the Greenland Sea in 2017. Technical report no. 110, Greenland Institute of Natural Resources, Greenland. ISBN 87-91214-88-2 24 pp. 1 English Summary Following a Strategic Environmental Study Plan for Northeast Greenland commissioned by the Danish Centre for Environment and Energy (DCE), the Greenland Institute of Natural Resources (GINR) and The Bureau of Minerals and Petroleum Greenland (BMP), a scientific cruise was conducted onboard the R/V Dana from 23 august to 11 September 2017. The main objective of the cruise was to provide environmental information for the planning and the regulating of oil exploration activities in the Greenland Sea. The specific objective of the present report is to provide information on ichthyoplankton and pelagic fish in the region. The methods used include ichthyoplankton nets, pelagic trawl and hydroacoustics. The ichthyoplankton collected belong to a very low number of species, predominantly polar cod (Boreogadus saida), a key species in arctic marine ecosystems. Spatially, polar cod dominated the assemblage on the continental slope and offshore while the other species dominated the shelf assemblage. Preliminary investigations suggested an apparent shift towards earlier hatching for polar cod, which could be associated with a relaxation in the extreme environmental conditions typical of the region (long sea-ice season and freezing sea surface temperature) over the past 25 years. This shift, if confirmed, could represent an increase in the recruitment of polar cod populations in the Greenland Sea. To investigate further this issue, a study based on otolithometric measurements of the polar cod larvae collected will be initiated in the coming months, and the results will be published in a peer-reviewed scientific journal such as Polar Biology. Combining the data from the echosounder with those of the trawl allowed to associate different echo patterns to specific organisms in the water column. Spatially, the acoustic data showed that the northeastern part of the study area appeared as a region of high biomass for the entire water column. The area encompassed the shelf break, an habitat polar cod is known to occupy in large biomass in other Arctic regions. Further analyses linking the acoustic data will with environmental parameters such as salinity, temperature and sea-ice dynamics will be done, compared with similar studies from other arctic seas, and synthesized in a publication to be submitted in a peer-reviewed scientific journal such as Progress in Oceanography. 2 Greenlandic Summary – Kalaallisut Naalisarneqarnera Kalaallit Nunaata kangiani avatangiisitigut misissuinissamut qitiusumik pilersaarutip Danmarkimi Nationalt Center for Miljø og Energimit (DCE), Pinngortitaleriffimmit kiisalu Bureau of Minerals and Petroleumimit (BMP) inniminnerneqartup kingorna umiarsuarmik R/V Danamik ilisimatusarneq augustip 23-anit septembarip 11-at 2017-ip tungaanut ingerlanneqarpoq. Umiarsuarmik angalanermi Kalaallit Nunaata imartaani uuliamik misissuinerit pilersaarusiarinissaat malittarisassiuunneqarnissaallu pillugit avatangiisinut paasissutissanik tunniussinissaq pingaarnertut siunertaavoq. Nunap imartaani aalisakkanut ikerinnarsiortunut suaannullu tunngasunik paasissutissiinissaq nalunaarusiami matumani pingaarnertut siunertaavoq. Periutsit atorneqartut ilaatigut tassaapput suannut qassutit, ikerinnarsiortunik kilisanneq kiisalu imaani nipit. Suaat katersorneqartut uumasoqatigiinniit ikittuinnarneersuupput, amerlanertigut eqalugaanerupput (Boreogadus saida), issittup imartaani uumasoqatigiinni ataqatigiiaartuni pingaarnersaasut. Immap itileriarneraniit itinersaanut eqalukkat amerlanerusimapput imarmili sinerissap qanittuani ikkattumi uumasoqatigit allat amerlanerusimallutik. Misissuigallarnerit takutippaat eqalukkat suaat siusinnerusukkut tukertalersimasut, tamanna ukiuni 25-ni avatangiisit nunap imartaani avatangiisitigut pissutsini imaannaanngitsuni (sivisuumik sikuusarnera immallu qaavata qerisarnera pissutigalugu) eqqissisimatitaanermit pissuteqarsinnaavoq. Tamanna allanngoriarneq uppernarsarneqassappat taava Kalaallit Nunaata imartaani eqalukkat amerleriassapput. Tamanna misissoqqinniarlugu eqalukkat suaasa/eqalukkat utoqqaassusaannik uuttukkat tunngavigalugit misissuineq qaammatini aggersuni aallartinneqassaq, misissuinermilu inernerit ilisimatusarnikkut allagaateqarfikkut soorlu Polar Biologykkut tamanut saqqummiunneqassapput. Akisuartaammit itissusersiummit paasissutissat kilisaatiniillu taamatut paasissutissat katinnerisigut imarmi itissutsini assigiinngitsuni uumassusillit paasineqarsinnaasimapput. Nipitigut paasissutissat takutippaat imarmi tamarmiusumi itissutsini assigiinngitsuni misissuiffigineqartumi avannaani kangiani amerlasuunik uumasoqarfiusoq. Imartaq misissuiffigineqartoq itileriarneqarsimavoq, Issittullu imartaanni allani itileriarnerit taama ittut eqalukkat uumaffigisartagaattut ilisimaneqarput. Misissueqqissaarnerit allat nipinik paasissutissanut atassutillit, avatangiisini uuttuinerit, soorlu tarajoqassutsimik, kissassutsimik sikullu aalaasianik misissuinerit atorlugit ingerlanneqassapput, matumani issittup imartaani allani misissuinerit sanilliunneqassapput ilisimatusarnikkullu allagaateqarfimmut soorlu Progress in Oceanographymut saqqummiunneqarnissaanut katinneqassallutik. 3 Danish Summary - Dansk Oversigt Efter en strategisk miljøstudieplan for Nordøstgrønland bestilt af Nationalt Center for Miljø og Energi (DCE), Grønlands Naturinstitut (GINR) og den Bureau of Minerals and Petroleum (BMP) blev der gennemført et videnskabeligt krydstogt ombord på R/V Dana fra 23. august til 11. september 2017. Hovedformålet med krydstogt var at levere miljøoplysninger til planlægning og regulering af olieudforskningsaktiviteter i Grønlandshavet. Det specifikke formål med denne rapport er at give information om fisk og deres larver i regionen. De anvendte metoder omfatter planktonnet, fisketræl og hydroakustik. Den opsamlede fisk larver tilhører et meget lavt antal arter, overvejende polar torsk (Boreogadus saida), en nøgleart i arktiske marine økosystemer. Polar torsk larver dominerede på den kontinentale hældning og offshore, mens de andre arter dominerede nær kysten. Præliminære undersøgelser foreslog et tilsyneladende skift i retning af tidligere udklækning for polar torsk, hvilket kunne være forbundet med en afslapning i de ekstreme miljøforhold, der er typiske for regionen (lang havis sæson og frysning temperatur) i løbet af de sidste 25 år. Dette skifte, hvis det bekræftes, kunne repræsentere en stigning i rekrutteringen af polar torsk populationer i Grønland. For yderligere at undersøge dette problem vil der blive indledt en undersøgelse baseret på otolithometriske målinger af polar torsk larverne i de kommende måneder, og resultaterne vil blive offentliggjort i et videnskabelige tidsskrift som Polar Biology. Kombination af data fra ekkoloddet med trawlerne tillades at forbinde forskellige ekko mønstre med bestemte organismer i vandkolonnen. Akustiske data viste, at den nordøstlige del af undersøgelsesområdet optrådte som en region med høj biomasse til hele vandkolonnen. Området omfattede den kontinentale hældning, en habitat polar torsk er kendt for at optage i stor biomasse i andre arktiske regioner. Yderligere analyser, der forbinder de akustiske data, vil med miljøparametre som saltholdighed, temperatur og havis dynamik udføres sammenlignet med lignende undersøgelser fra andre arktiske have og syntetiseres i en publikation, der skal indsendes i et videnskabelige tidsskrift som Progress in Oceanography. 4 Table of Content English summary ....................................................................................................................... 1 Danish summary - Dansk Oversigt ............................................................................................ 2 Table of Content ........................................................................................................................ 4 List of Tables ............................................................................................................................. 5 List of Figures ............................................................................................................................ 6 1. Introduction ............................................................................................................................ 7 2. Materials and Methods ........................................................................................................ 8 2.1. Field sampling ................................................................................................................ 8 2.2. Data analysis .................................................................................................................. 8 3. Results ................................................................................................................................. 10 3.1. Ichthyoplankton .......................................................................................................... 10 3.2. Pelagic fish and other fauna ....................................................................................... 11 3.3. Hydroacoustics ............................................................................................................ 12 4. Discussion ............................................................................................................................ 20 4.1. Ichthyoplankton .......................................................................................................... 20 4.2. Pelagic fish and other fauna ....................................................................................... 20 5. Acknowledgements .............................................................................................................. 21 6. References ............................................................................................................................ 22 5 List of Tables Table 1. Main taxa collected in the FOTÖ mesopelagic trawl………………………………10 6 List of Figures Figure 1. Example of acoustic data before (left panel) and after (middle and right panels) signal conditioning combining a background, impulse and transient noise removal algorithms and smoothing with a median filter and ping resampling. ............................................................................................... 9 Figure 2. Abundance and taxonomical composition of ichthyoplankton sampled during the 2017 survey in Northeast Greenland. ............................................................................................................. 10 Figure 3. Localization of the stations sampled with the FOTÖ mesopelagic trawl during the 2017 survey in Northeast Greenland. Color scale indicates bathymetry. ...................................................... 11 Figure 4. Echogram at 38 Khz recorded during the pelagic trawl deployment at station 14. The thick scattering layer between ca. 300-500 m was associated with aggregations of the Myctophid fish Benthosema glaciale. ............................................................................................................................ 12 Figure 5. Echogram at 38 Khz recorded during the pelagic trawl deployment at station 24. The thin scattering layers between ca. 60-120 m were associated with aggregations of the squid Gonatus fabricii. .................................................................................................................................................. 13 Figure 6. Echogram at 38 Khz recorded during the pelagic trawl deployment at 30 m at station 76 which resulted in an empty net. ............................................................................................................ 13 Figure 7. Echogram at 38 Khz recorded during the pelagic trawl deployment at station 83 which yielded a mix of krill, the amphipod Themisto libellula, polar cod, squids and Myctophids. .............. 14 Figure 8. Echogram at 38 Khz recorded at 500 m bottom depth near the continental shelf break) showing an upwelling. Black color indicates periods of unusable data. ............................................... 14 Figure 9. Maps indicating acoustic backscatter (log NASC at 38 Khz) along the ship’s route (top panel) and interpolated over the study area (bottom panel) for the surface layer. Grey contour lines show 50, 100, 250, 500, 1000, 1500, and 2000 m isobaths. ................................................................. 16 Figure 10. Maps indicating acoustic backscatter (log NASC at 38 Khz) along the ship’s route (top panel) and interpolated over the study area (bottom panel) for the epipelagic layer. Grey contour lines show 50, 100, 250, 500, 1000, 1500, and 2000 m isobaths. ................................................................. 17 Figure 11. Maps indicating acoustic backscatter (log NASC at 38 Khz) along the ship’s route (top panel) and interpolated over the study area (bottom panel) for the mesopelagic layer. Grey contour lines show 50, 100, 250, 500, 1000, 1500, and 2000 m isobaths. ......................................................... 18 Figure 12. Maps indicating acoustic backscatter (log NASC at 18 Khz) along the ship’s route (top panel) and interpolated over the study area (bottom panel) for the demersal layer. Grey contour lines show 50, 100, 250, 500, 1000, 1500, and 2000 m isobaths. ................................................................. 19 7 1. Introduction This report was commissioned by the Danish Centre for Environment and Energy (DCE), the Greenland Institute of Natural Resources (GINR) and The Bureau of Minerals and Petroleum Greenland (BMP) as part of the Strategic Environmental Study Plan for Northeast Greenland 2016-2019 to provide environmental information for planning and regulating oil exploration activities and oil spill response in the Greenland Sea. The main objective consisted in documenting the horizontal and vertical distribution of ichthyoplankton and pelagic fish assemblages in the Greenland Sea using ichthyoplankton nets, a pelagic trawl and hydroacoustics. 14 Figure 7. Echogram at 38 Khz recorded during the pelagic trawl deployment at station 83 which yielded a mix of krill, the amphipod Themisto libellula, polar cod, squids and Myctophids. Figure 8. Echogram at 38 Khz recorded at 500 m bottom depth near the continental shelf break) showing an upwelling. Black color indicates periods of unusable data. 15 To show the vertical and horizontal distribution of the acoustic signal, maps of the nautical area scattering coefficient (NASC in unit m2 nmi−2) at 38 Khz were prepared for three depth strata: the surface (5-25 m), the epipelagic (25-200 m), and the mesopelagic (200-800 m) layer. Additionally, part of the acoustic data at 18 kHz were clean near the bottom, and were used to build a map of demersal acoustic backscatter (bottom 50 m). Each map is presented both along the ship’s route and interpolated over the study area (Fig. 9-12). Acoustic backscatter in the surface was higher in the northeastern part of the study area (Fig. 9), coinciding with the are where the most larval and juvenile Gadidae were collected in the nets (Fig. 2). For the epipelagic layer, the strongest acoustic backscatter was found on the shelf at ca. 76-77°N (Fig. 10). Areas of strong epipelagic backscatter also included the coastal south of the Wollaston Foreland peninsula, the continental shelf break above 76°N, and deep water regions in the northeastern part of the study area (Fig. 10). Acoustic backscatter in the mesopelagic layer was higher near the shelf break in the northeastern part of the study area (Fig. 11). The demersal acoustic backscatter varied little among the available data along the ship’s route (Fig. 12). 16 Figure 9. Maps indicating acoustic backscatter (log NASC at 38 Khz) along the ship’s route (top panel) and interpolated over the study area (bottom panel) for the surface layer. Grey contour lines show 50, 100, 250, 500, 1000, 1500, and 2000 m isobaths. 17 Figure 10. Maps indicating acoustic backscatter (log NASC at 38 Khz) along the ship’s route (top panel) and interpolated over the study area (bottom panel) for the epipelagic layer. Grey contour lines show 50, 100, 250, 500, 1000, 1500, and 2000 m isobaths. W F W F 18 Figure 11. Maps indicating acoustic backscatter (log NASC at 38 Khz) along the ship’s route (top panel) and interpolated over the study area (bottom panel) for the mesopelagic layer. Grey contour lines show 50, 100, 250, 500, 1000, 1500, and 2000 m isobaths. 19 Figure 12. Maps indicating acoustic backscatter (log NASC at 18 Khz) along the ship’s route (top panel) and interpolated over the study area (bottom panel) for the demersal layer. Grey contour lines show 50, 100, 250, 500, 1000, 1500, and 2000 m isobaths. 20 4. Discussion 4.1. Ichthyoplankton With very few species, the taxonomical composition of the larval and juvenile fish assemblages collected during the present study was similar to that of another survey carried out in the Greenland Sea in 1993 (Michaud et al. 1996). However, the early life dynamics of polar cod Boreogadus saida, a key species in this ecosystem, may have changed since then. Considering the size range of the individuals collected in the present study, their capture date, and growth rates typical of the species in the circumpolar Arctic (Bouchard and Fortier 2008; 2011), it appears that the hatching season was from mid-March to mid-July in 2017, compared to midMay to the end of July in 1993 (Fortier et al. 2006). As documented in the Canadian Arctic, the apparent shift towards earlier hatching could result from an increase in the survival of early hatchers following a relaxation in the extreme environmental conditions typical of the region (long sea-ice season and freezing sea surface temperature) over the past 25 years (Bouchard and Fortier 2011). This change may be synonymous with a transient increase in recruitment (Bouchard et al. 2017), although no conclusion can be drawn from the data currently available. 4.2. Pelagic fish and other fauna The most abundant fish species collected with the pelagic trawl was the Myctophid Benthosema glaciale. The other fish species collected in the pelagic trawl corresponded to the species captured as larvae and juveniles in the MIKnet: polar cod, Triglops nybelinii and Liparis fabricii. Euphausids (krill) was the taxa collected in the highest biomass in the pelagic trawl and was also collected in large quantities by the MIKnet. From the acoustic data, the northeastern part of the study area appeared as a region of high biomass for the entire water column. The area encompassed the shelf break, an habitat polar cod is known to occupy in large biomass in other Arctic regions, such as the Canadian and the Alaskan Beaufort Sea (Geoffroy et al. 2016, Parker-Stetter et al. 2011). The acoustic data also provided anecdotal evidence of upwelling at the shelf break in this area, a feature that could enrich surface waters with nutrients and support relatively high biomass of phyto-, zoo-, and ichthyoplankton and create a local pelagic ‘’hotspot’’. 21 5. Acknowledgements The funding of this study was provided by the Northeast Greenland Environmental Study Program. The Northeast Greenland Environmental Study Program is a collaboration between DCE – Danish Centre for Environment and Energy at Aarhus University, the Greenland Institute of Natural Resources, and the Environmental Agency for Mineral Resource Activities of the Government of Greenland. Oil companies operating in Greenland are obliged to contribute to knowledge regarding environmental matters. The Strategic Environmental Impact Assessment and the background study program is funded under these commitments administered by the Mineral Licence and Safety Authority and the Environmental Agency for Mineral Resource Activities. The acoustic data collected were analyzed by Julek Chawarski at Memorial University of Newfoundland under the supervision of Dr. Maxime Geoffroy. 22 6. References Akima, H. and Gebhardt, A. 2016. Akima: Interpolation of Irregularly and Regularly Spaced Data. 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