Trophic Dynamics of Marine Nekton and Zooplankton in the Northern California Current Ecosystem
Todd Miller1, Richard Brodeur2 and Greg Rau3 1Center for Marine Environmental Studies, Ehime University, Matsuyama, Japan 2NMFS Northwest Fisheries Science Center, Fish Ecology Division, Newport Oregon, USA 3Institute of Marine Sciences, University of California, Santa Cruz California USA Overview I. Background A. Upwelling ecosystems B. Northern California Current (NCC) ecosystem II. Objectives III. Methods A. Diet analyses B. Stable isotopes IV. Results & Discussion V. Conclusions I. Background - Major upwelling ecosystems • Highly productive (primary production to higher trophic levels) • Baitfish (sardine and anchovy), mackerel and hake • ~0.1% of world ocean with ~50% world fisheries catch • Direction of trophic control: (1) top-down (2) bottom-up (3) wasp-waist Northern CC Ecosystem • Upwelling ecosystem – High nutrients – Base production – Variable - Seasonal, interannual, interdecadal • Dominant nekton species – Planktivores – sardine, anchovy, herring, smelts – Plankt/Piscivores - jack mackerel, hake, salmonids – Piscivores – sharks, adult salmon • Strong seasonal, interannual, interdecadal variation in production • Spatially dynamic – shelf-near shore high primary production – slope-offshore lower production II. Objectives
(i) Determine the primary trophic links between fish and zooplankton in the NCC
(ii) Determine if there is structural evidence indicative of top-down, bottom-up or wasp- waist control
Diet Analysis (stomach content analysis)
Stable Isotope Analysis - Carbon (13C/12C) – tells source production (where food comes from) - Nitrogen (15N/14N) – relative trophic level (+3.4 o/oo per trophic level) III. Methods – Collection - Four GLOBEC cruises 45° N - June and August, 2000 and 2002 1 - 18 Jun 2002 1 - 17 Aug 2002
NH - Collected fish and zooplankton (including 1A 2A NH 44° N BOB 1A OREGON 2 OREGON 3A 2A POM) HH BOB 4A 3A UR HH 6 4A - Measured SSS, SST, Chl-a UR 43° N Latitude FM 6 7A Cape Blanco Cape Blanco 8 FM 7A 9 8 - Laboratory 9B RR 9 42° N RR CALIFORNIA CALIFORNIA - Diet analysis – 21 spp. nekton = >3000 10A CR 11 125° W 124° W 125° W 124° W stomachs Longitude CR Longitude - Isotopes – 31 spp., >1500 samples III. Methods – Measuring trophic patterns
1. Diet Analysis a) Percent wet wt. prey contribution to diet b) Analyzed spp. collected >4 hauls, n=10-30 individuals per haul c) Cluster Analysis (PRED X PREY matrix) - groups using MRPP d) Indicator Species Analysis – describe dominant prey within groups III. Methods – Measuring trophic patterns
2. Stable Isotopes a. 13C/12C Corrected for lipids b. 3-5 individual sampled per spp., per site c. δ15N compared to trophic cluster groups based on diets N
15 3.4/TL δ
δ13C IV. Results – Cluster and Indicator Species Analysis YR 2000 (June and August combined)
Information Remaining (%) 100 100 75 50 25 0
blueBlue shark sharkBlue shark adultCoho salmon Cohocoho (a)salmon (a) Market squidMarket squid squidSablefishSablefish (j) (j) WhitebaitWhitebait smelt smelt
whitebaitSurf smeltSurf smelt smelt Indicator Prey ChinooksurfChinook salmon smelt (s)salmon (s) Fish, juv-adult ChinookjuvChinook salmon sablefish (y)salmon (y) Cohojuv salmonCoho salmonids (y)salmon (y) Fish (l), Euph ChinookChinook salmon (a)salmon (a) CutthroatCutthroat trout trout Euph, Fish (l) jackJackmackerel mackerelJackmackerel Copepods chubPacific mackerel sauryPacific saury NorthernNorthern anchovy anchovy
sauryPacific sardnePacific sardne herringPacific herringPacific herring juvSteelhead steelheadSteelhead trout (j) trout (j) sardinePacific mackerelPacific mackerel SteelheadSteelhead trout (a) trout (a)
DarkblotchedrockfishDarkblotchedrockfish (j) (j)
juv rockfishLingcod Lingcod(j) (j)
YellowtailjuvYellowtail lingcod rockfish rockfish(j) (j) B. Results – Cluster and Indicator Species Analysis YR 2002 (June and August combined)
Information Remaining (%)
100 75 50 25 0 juv. BankRockfish rockfish (j) Canary rockfish (j) sand lanceLingcod (j) sauryWidow rockfish (j) Pacific saury surfDarkblotched smelt rockfish Pacific sand lance IndicatorIndicator Prey Prey anchovy Surf smelt sardine Northern anchovy Fish,Fish, adult juv-adult Pacific sardine Fish (l), Euph spiny dogfishSpiny dogfish Fish (l), Euph Blue shark Euph, Fish (l) hake Pacific hake Euph, Fish (l) adult cohoMarket squid Copepods Coho salmon (a) Copepods squid Jack mackerel Chinook salmon (y) Steelhead trout (j) juv salmonChinook salmon (a) herring Coho salmon (y) Chinook salmon (s) sablefishChum salmon (j) whitebait Pacificsmelt herring Sablefish (j) Cutthroat trout Whitebait smelt Diets June 2000 PREY
Jack mackerel Fish (adult) Pacific sardine
Darkblotched rockfish (j) Fish (larv-juv)
Yellowtail rockfish (j) Fish mat. Unidentified rockfish (j)
Chinook salmon (y) E. pacifica Coho salmon (y)
Steelhead trout (j) T. spinifera
Chinook salmon (a) Euphausiids Market squid
Surf smelt Copepods Whitebait smelt
Pacific herring Unident.
Sablefish (j)
Lingcod (j)
0% 20% 40% 60% 80% 100%
Wet Weight (%) Boxes = trophic cluster groups Diets August 2000 PREY
Whitebait smelt Fish (adult) Steelhead trout (a) Cutthroat trout Fish (larv-juv) Chinook salmon (s) Northern anchovy Fish mat. Sablefish (j) Blue shark E. pacifica Coho salmon (a) Surf smelt T. spinifera Coho salmon (y)
Chinook salmon (y) Euphausiids Chinook salmon (a) Pacific mackerel Copepods Pacific saury
Pacific sardine Unident. Jack mackerel Steelhead trout (j)
0% 20% 40% 60% 80% 100% Wet Weight (%) Wet Weight (%)
Boxes = trophic cluster groups Diets June 2002 PREY
Blue shark Fish (adult) Whitebait smelt
Surf smelt
Northern anchovy Fish (larv-juv)
Lingcod (j)
Darkblotched rockfish (j) Fish mat. Bank rockfish (j)
Canary rockfish (j)
Jack mackerel E. pacifica
Spiny dogfish
Chinook salmon (a) T. spinifera Pacific hake
Coho salmon (y)
Chinook salmon (y) Euphausiids
Chum salmon (j)
Pacific saury Copepods Market squid
Steelhead trout (j)
Pacific herring Unident.
Pacific sand lance (j)
Pacific sardine
Widow rockfish (j)
0% 20% 40% 60% 80% 100% Wet Weight (%)
Boxes = trophic cluster groups Diets August 2002 PREY
Pacific hake Fish (adult)
Whitebait smelt
Surf smelt Fish (larv-juv)
Chinook salmon (s)
Steelhead trout (j) Fish mat.
Cutthroat trout
Pacific sardine E. pacifica Blue shark
Market squid T. spinifera Pacific saury
Chinook salmon (y) Euphausiids Northern anchovy
Jack mackerel Copepods Chinook salmon (a)
Pacific herring Unident. Sablefish (j)
Coho salmon (y)
0% 20% 40% 60% 80% 100% WetWet Weight Weight (%) (%)
Boxes = trophic cluster groups 4 Prey Groups 16
N (‰)N (‰) Fish (adult)
1515 Yr 2000 Coho (y) Jack mackerel Whitebait smelt
δδ Coho (a) Chinook (s) August Chinook (a) Chinook (y) Fish (larv-juv) 14 Blue shark Euphausiids Pacific mackerel Pacific sardine Rockfish (j) Euphausiids 12 Pacific sand lance (j) Fish (larv-juv) Pacific sardine (j)* Flatfish (l)* T. spinifera Copepods
10 Copepods* Decapoda* E. pacifica C (o/oo) 15
δ Hyperiids (j)* 8 3.4
POM* 6 [NITROGEN ISOTOPE RATIO] [NITROGEN ISOTOPE
4 -24 -22 -20 -18 -16 -14 -12 δ13C (o/oo) [CARBONδ 13 ISOTOPEC (‰) RATIO] 4 Prey Groups
N (‰)N (‰) 16 Fish (adult)
1515 Chum (j) Yr 2002 Blue shark Coho (y) δδ August Jack mackerelChinook (y) Cutthroat trout Chinook (a) Fish (larv-juv) 14 Chinook (s) Whitebait smelt Euphausiids Sablefish (j) P. herring Northern anchovy Surf smelt Steelhead trout (j) Rockfish (j) Pacific saury Euphausiids Pacific sardine Market squid 12 Phacellophora Fish (larv-juv) Flatfish (l)* Pacific sand lance Aequorea Chrysaora Copepods T. spinifera 10 Copepods Decapoda* E. pacifica C (o/oo) Aurelia 15
δ Themisto 8 Hyperoche
6 POM [NITROGEN ISOTOPE RATIO] [NITROGEN ISOTOPE
4 -24 -22 -20 -18 -16 -14 -12 δ13C (o/oo) 13 [CARBONδ ISOTOPEC (‰) RATIO] Trophic BOTTOM Level BOTTOM TOP WASP UP Taxa UP DOWN WAIST (OMNIVORY)
Sharks, adult salmonids 4°C 4°C 4°C 4°C
Hake, mackerel, Juv salmonids 3°C 3°C 3°C 3°C ,
Sardine, anchovy, Herring, squid, smelt, 2°C 2°C ENV 2°C 2°C sand lance
Euphausiids (krill) Copepods, decapod 1°C 1°C 1°C 1°C larvae
Phytoplankton/microbial community PP PP PP PP
ENV ENV Market squid OFFSHORE NEARSHORE Pacific herring Northern anchovy* Surf smelt Steelhead trout (j) Chinook salmon (a) Pacific sand lance (j) Whitebait smelt Nekton Jack mackerel Spiny dogfish Pacific sardine Pacific saury Cuttroat trout Chum salmon (a)* Coho salmon (a) Sebastes spp. (j) Chrysaora fuscescens Aurelia aurita Gelatinous Aequorea victoria zooplankton Phacellophora camtschatica Beroe sp. Thysanoessa spinifera Euphausia pacifica Crustacean Cancer ant/grac (m) C. magister (m) zooplankton C. oreg/prod (m) Copepoda (shelf) Copepoda (slope) Particulate Organic POM (shelf) POM (slope) Matter (POM) -26 -24 -22 -20 -18 -16 -14 -12 -10 δ13C Division of NCC food web using δ13C and δ15N
SLOPE/OFFSHORE Blue shark 16 Cutthroat trout Saury SHELF/NEARSHORE Sardine (ad.) Soupfin shark 15 Jack mackerel Herring larval-juv. fish Smelts 14 Market squid Sardine (juv.) Anchovy 13
12 N (‰) 11 15 δ offshore copepods* 10 Thysanoessa spinifera*
9 Euphausia pacifica* nearshore copepods*
8 -22 -21 -20 -19 -18 -17 -16 -15 δ13C (‰) Assuming change of 0.80 per trophic level
*Mann-Whitney test – significant difference in δ13C between near shore and offshore sites Trophic Structure Conclusions
• Seasonally and interannually variable • Many species exhibited considerable dietary overlap (euphausiids and larval- juvenile fish) • Trophic structure more indicative of bottom-up control with omnivory prominent during this period • Cross-shelf spatial structure to the NCC food web