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Zooplankton Communities and Pelagic Fish Diet in the Barents Sea During Recent Warming Period

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Zooplankton Communities and Pelagic Fish Diet in the Barents Sea During Recent Warming Period ICES/PICES 6th Zooplankton Production Symposium 9-13 May 2016, Scandic Bergen "New Challenges in a Changing Ocean" City, Bergen, Norway Zooplankton communities and pelagic fish diet in the Barents Sea during recent warming period A.V. Dolgov1, P. Dalpadado2, I.P. Prokopchuk1, A. S. Orlova1, A.S. Gordeeva1, A. N. Benzik1 1- Knipovich Polar Research Institute of Marine fisheries and Oceanography (Murmansk, Russia) 2- Institute of Marine Research (Bergen, Norway) 1 Background • The Barents Sea is arcto-boreal sea • > 300 zooplankton species • > 200 fish species, appr. 20 species plankton-feeders • Warm period had observed since late 1990s • Considerable changes in distribution and structure of plankton and fish communities were observed during 2000s 2 Objectives • To consider current state of zooplankton communities in the Barents Sea in recent warming period • To consider a possible effect of changes in zooplankton on diet of the most abundant planktivorous fishes in the Barents Sea in this period 3 Materials and methods • Data on mesozooplankton from the international ecosystem survey in the Nordic Seas (May-June 2008-2015) and PINRO-IMR ecosystem surveys (August-September 2004- 2015) • Data on macroplankton from Russian TAS (October-December 1959-2014) • Data on the diet of capelin (5 992 stomachs), polar cod (3 105 stomachs), herring (6 359 stomachs) and blue whiting (6 356 stomachs) 4 Total zooplankton biomass (g dw m-2) in August-September 2004-2015 2015 - 7.3 gm-2 (263 st.) 2014 - 6.7 gm-2 (232 st.) 2013 – 7.1 gm-2 (305 st.) 2012 – 7.6 gm-2 (287 st.) 5 Mesozooplankton • Main focus on taxons which are important prey species for pelagic fishes or which have ecological importance in the Barents Sea • Copepods • Euphausiids • Hyperiids • Chaetognaths (predators on zooplankton) • Jellyfish (predators on zooplankton and fish eggs and larvae) 6 IMR and PINRO standard sections 100000 the Fugløya-Bjørnøya 90000 2 m 80000 ./ 70000 ind , 60000 50000 40000 Abundance 30000 20000 10000 0 Calanus finmarchicus C. hyperboreus C.glacialis 1800000 the Kola 1600000 2 1400000 m ./ ind 1200000 , 1000000 • Total abundance of Calanus spp. 800000 on the Fugløya- Bjørnøya Abundance 600000 400000 section (IMR) and the Kola 200000 0 section (PINRO) 2008 2009 2010 2011 2012 2013 2014 2015 Calanus finmarchicus C. hyperboreus C.glacialis 7 Fugløya-Bjørnøya section Kola section 160000 3000000 140000 C. finmarchicus Calanus finmarchicus ) 2 - 120000 2500000 7030ºN -2 100000 2000000 (no. m (no. 80000 7200ºN 1500000 60000 7330ºN Abundance, ind. m ind. Abundance, 40000 7400ºN 1000000 Abundance 20000 500000 0 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 0 69°30' 70°00' 70°30' 71°00' 71°30' 72°00' 72°30' 73°00' 73°30' 74°00' 1992 2008 2009 2010 2011 2012 2013 2014 2015 3000 800 C. glacilais Calanus glacialis 2500 700 600 ) -2 2 2000 - 7030ºN 500 7200ºN 1500 400 7330ºN 1000 300 Abundance, ind. m ind. Abundance, 7400ºN 200 500 100 0 0 Abundance (no. m (no. Abundance 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 69°30' 70°00' 70°30' 71°00' 71°30' 72°00' 72°30' 73°00' 73°30' 74°00' 1992 2008 2009 2010 2011 2012 2013 2014 2015 • Relatively high abundances of C. finmarchicus along the FB section in 2014 and 2015 • Highest abundance of C. finmarchicus observed in 2010 for both sections 8 • Highest abundances of C. glacialis > 73º N in both sections • Low abundances of C. glacialis along FB section during 2012-2014 – more in 2015 Abundance of Calanus species on the Fugløya- Bjørnøya and the Kola sections Copepods abundance and biomass in the northern BS in August-September - Decrease in total abundance and biomass of copepods - Decrease in the portion of large species (Calanus. glacialis, C. finmarchicus, C. hyperboreus) - Increase in small species (Pseudocalanus minutus) abundance, but not biomass 10 Mesozooplankton abundance in 2014 Northern part – Copepods - 95 % Pteropods - 3,6 % P. minutus – 73 % M. longa – 12 % C. glacialis - 8 C. finmarchicus – 6 % C. hyperboreus – 1 % Southern part – Copepods – 94 %, Meroplankton – 2,1 % P.minutus – 47 % C.finmarchicus – 40 % M.longa – 13 % 11 Mesozooplankton biomass in 2014 Northern part – Copepods - 75 % Chaetognaths – 16,2 % Pteropods, hyperiids, euphausiids, hydromedusae – 2,0- 3,7% C. glacialis – 57 % P. minutus – 15 % M. longa – 11 % C. finmarchicus – 10 % C. hyperboreus – 7 % Southern part – Copepods – 68 % Chaetognaths – 24 % Euphausiids -4 % C.finmarchicus – 75 % M.longa – 15 % P.minutus – 7 % 12 Euphausiids Southern part 2014 – 1637 2013 – 675 mean – 568 ind./1000 m3 North-western part 2014 – 1656 2013 – 640 mean – 939 ind./1000 m3 13 Distribution and species composition of euphausiids abundance biomass T. inermis T. raschii - Distribution of euphausiids was rather similar to last warm years T. longicaudata M. norvegica (2004-2014) - Higher abundance and portion of warmwater species - Distribution area of warmwater species increased 14 Hyperiids 25 20 15 10 5 • Distribution area decreased Abundance, ind./1000 m3 Abundance,ind./1000 0 last years 2008 2009 2010 2011 2012 2013 2014 Years • Abundance of hyperiids October-December decreased during the last 2014 warm years and now is very low 15 Chaetognaths 1800 1600 1400 1200 1000 800 600 400 Abundance, ind./1000 м3 Abundance,ind./1000 200 0 2009 2010 2011 2012 2013 2014 Years October-December • Abundance of predatory 2014 chaetognaths increased during the last warm years and now is on rather high level • Possibly their high abundance resulted to decreasing of copepods abundance and biomass 16 Jellyfish - Increasing of jellyfish abundance since 2000s - Possibly negative impact on zooplankton abundance and fish recruitment Distribution of jellyfish, August-September 2013 (Eriksen, 2013) The total jellyfish biomass, mostly Cyanea capillata in 1980-2015, million tonnes (Eriksen et al., 2015) 17 Pelagic fishes in the Barents Sea • The most abundant pelagic fishes are 3 boreal species (capelin, herring and blue whiting) and 1 arctic species (polar cod) 8000 Capelin 7000 Herring Blue whiting 6000 Polar cod 5000 4000 3000 2000 Stock biomass, thous. tons thous. biomass, Stock 1000 0 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 Year 18 Polar cod - Main food – copepods, hyperiids and euphausiids - Decreasing of feeding intensity - Decreasing of copepod role in diet 19 Capelin - Main food – copepods and euphausiids - Decreasing of feeding intensity - Decreasing of copepod role in diet 20 Atlantic herring Polar cod Other food Capelin 0,1% 2,0% Herring 0,0% Other fish 0,1% Indeterminates 3,9% 1,0% Appendicularia 2,0% Pteropoda Chaetognatha 8,6% 0,2% - Main food – copepods and euphausiids Copepoda Euphausiidae 40,5% - No obvious changes in diet and feeding 38,8% intensity Hyperiida 2,6% 100% Indeterminates 90% Other food 80% Polar cod Capelin 70% Euphausiidae Herring 60% Other fish 50% Appendicularia Chaetognatha 40% % by weight Euphausiidae 30% Hyperiida Copepoda 20% Copepoda Pteropoda 10% Pteropoda Ctenophora 0% 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 21 Year Blue whiting Other fish Other food Cephalopoda 1,68% 0,01% 0,14% Redfish 0,00% Copepoda 0,11% Euphausiidae 42,23% Capelin - Main food – fish and euphausiids 55,28% - No obvious changes in diet and feeding intensity Pandalus borealis 0,55% 100% Other food 90% Other fish 80% Long rough dab Redfish Polar cod 70% Norway pout Haddock 60% Cod 50% Capelin Polar cod Capelin % by weight 40% Herring 30% Chaetognatha Euphausiidae Pandalus borealis 20% Euphausiidae Hyperiidae 10% Hyperiidae Copepoda 0% Cephalopoda 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 Ctenophora 22 Year Conclusions • Total biomass of zooplankton varied not so much in 2004- 2015 • Abundance and biomass of mesoplankton on the northern Barents Sea decreased since 2006-2007 • In mesoplankton communities shift from larger copepods (C. glacialis, C. finmarchicus, C. hyperboreus) to smaller copepods (Pseudocalanus minutus) was observed in the northern Barents Sea • Euphausiids abundance was higher than the long-term mean • The abundance of arctic hyperiids decreased • The abundance of predatory plankton (chaetognaths and jellyfish) increased • Feeding conditions for pelagic fishes, especially capelin and polar cod, became worse 23.
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