Michael P. SekiNOAA Fisheries

Pacific Islands Fisheries Science Center

Micronekton in the North Pacific … what do we know?

““micronekton” defined …micronekton” defined …

Small but actively swimming organisms ranging from ca. 2 to 10 Small but actively swimming organisms ranging from ca. 2 to 10 cm; mainly mesopelagic (200-1000 m depths)cm; mainly mesopelagic (200-1000 m depths)

Taxa too vagile to be caught with conventional plankton nets Taxa too vagile to be caught with conventional plankton nets yet too small to be retained by most large trawls.yet too small to be retained by most large trawls.• Fishes – mainly mesopelagics and juveniles of epipelagic Fishes – mainly mesopelagics and juveniles of epipelagic

nektonnekton• Crustaceans – includes adult euphausiids, pelagic Crustaceans – includes adult euphausiids, pelagic

decapods, mysids, hyperiid amphipodsdecapods, mysids, hyperiid amphipods• Cephalopods – small adults and subadults of large Cephalopods – small adults and subadults of large

oceanics oceanics Many undertake extensive diel vertical migrationsMany undertake extensive diel vertical migrations

Why do we care?Why do we care?

● Represents a substantial biomass in the Represents a substantial biomass in the world’s oceansworld’s oceans

● A critical but poorly understood A critical but poorly understood intermediate (missing?) trophic link intermediate (missing?) trophic link between the mesozooplankton & higher between the mesozooplankton & higher trophic levels (i.e., fish, marine mammals, trophic levels (i.e., fish, marine mammals, etc.)etc.)

● Significant contributors to the “biological Significant contributors to the “biological pump” (i.e., rapid transport of Cpump” (i.e., rapid transport of Csurfacesurface, as , as well as pollutants, to deep sea).well as pollutants, to deep sea).

Relatively scant attention paid to Relatively scant attention paid to micronekton as a wholemicronekton as a whole

In 1997, PICES establishes a WG to In 1997, PICES establishes a WG to assimilate knowledge of micronekton assimilate knowledge of micronekton & their sampling in the North Pacific& their sampling in the North Pacific

Broadly, much of what is known Broadly, much of what is known results from research of the 1960s & results from research of the 1960s & 70s70s

… … most focused on the marginal seas most focused on the marginal seas around the basin rim (i.e., we know around the basin rim (i.e., we know least about the open ocean)least about the open ocean)

… … and little effort expended in and little effort expended in comparing relative sampling comparing relative sampling efficiencies and selectivity of the gearsefficiencies and selectivity of the gears

Some history and milestones of micronekton Some history and milestones of micronekton research around Hawaii and the Central North research around Hawaii and the Central North Pacific:Pacific:

● King & Iversen (1962): oceanic Central Pacific & Hawaii – 6’ & 10’ King & Iversen (1962): oceanic Central Pacific & Hawaii – 6’ & 10’ IKMT; zIKMT; zmaxmax ~ 350 m ~ 350 m

● Clarke, Young, and others (1972-78): off Hawaii; 6’ & 10’ IKMT, Cobb Clarke, Young, and others (1972-78): off Hawaii; 6’ & 10’ IKMT, Cobb trawl; ztrawl; zmaxmax to 1200 m to 1200 m

● Wilson, Boehlert and others (1985-88): Hancock Smts – Wilson, Boehlert and others (1985-88): Hancock Smts – “engybenthic” micronektonic fauna; qualitative acoustics“engybenthic” micronektonic fauna; qualitative acoustics

● Reid et al. (1991): off Hawaii; Mesopelagic Boundary Community Reid et al. (1991): off Hawaii; Mesopelagic Boundary Community (MBC); IOS-RT 40 m(MBC); IOS-RT 40 m22, HU-200 m, HU-200 m22 trawl; z trawl; zmaxmax ~500-600 m ~500-600 m

● Benoit-Bird and Au: off Hawaii (2001-2003): MBC, quantitative Benoit-Bird and Au: off Hawaii (2001-2003): MBC, quantitative acoustics, horizontal migration, micro-patches)acoustics, horizontal migration, micro-patches)

● PICES (2004): off Hawaii; 6’ IKMT, Cobb trawl, HU-RT gear PICES (2004): off Hawaii; 6’ IKMT, Cobb trawl, HU-RT gear comparison; quantitative acousticscomparison; quantitative acoustics

SE Hancock Acoustic transects, July 1984SE Hancock Acoustic transects, July 1984(38 kHz Simrad echo sounder)(38 kHz Simrad echo sounder)

1941-h 0330-h 0430-h 0630-h

““Minimum no. species caught”Minimum no. species caught”

Summer ‘84Summer ‘84 Winter ‘85Winter ‘85 ‘ ‘on’ ‘off’ ‘on’ ‘off’on’ ‘off’ ‘on’ ‘off’

No. tows 12 6 12 10No. tows 12 6 12 10

Crustaceans Crustaceans 23 26 23 2923 26 23 29Fishes Fishes & cephalopods & cephalopods 21 2421 24 47 6147 61

Fishes & SquidFishes & Squid

Maurolicus muelleri

Species "on" "off" "on" "off"

Maurolicus muelleri 4.19 (2) 0.06 0.17 --Lampanyctus alatus 0.03 0.02 0.09 0.90 (5)Ceratoscopelus townsendi 0.20 0.20 0.20 0.60Vinciguerria nimbaria 0.80 0.03 0.39 0.73Vinciguerria attenuata 0.17 0.93 0.02 0.16

Iridoteuthis iris 0.35 0.03 0.25 --Onychoteuthis n. sp. D -- -- 0.24 0.46Megalocranchia cf. fisheri -- -- 0.10 0.20

Summer (Jul-Aug '84) Winter (Jan-Feb '85)

Mean densities (individuals/1000 m3 water filtered) of selected micronekton species in the vicinity of SE Hancock

(number in parentheses indicate rank among top five species)

Vinciguerria nimbariaVinciguerria nimbaria

Iridoteuthis irisIridoteuthis iris

CrustaceansCrustaceans

Gnathophausia longispina

Gennadas propinquus

Oplophorus spinosus

Euphausia gibboidesSpecies "on" "off" "on" "off"

Gnathophausia longispina 11.60 (1) 2.59 (4) 7.26 (1) --

Euphausia gibboides 1.23 (4) 5.50 (1) 6.98 (2) 3.27 (2)Euphausia hemigibba 0.82 (5) 1.93 2.65 (3) 4.28 (1)Euphausia mutica 1.38 (3) 2.24 (5) 0.24 0.28Thysanopoda monacantha 0.07 2.81 (3) 0.37 1.09 (4)Thysanopoda orientalis 0.15 3.75 (2) -- 0.06Thysanopoda tricuspidata -- 0.02 0.50 0.29Stylocheiron abbreviatum 0.19 0.91 0.76 1.57 (3)Thysanoessa gregaria -- -- 0.10 0.01

Gennadas incertus -- 0.2 -- 0.6 (5)

Oplophorus spinosus 0.01 0.29 0.03 0.29

Mean densities (individuals/1000 m3 water filtered) of selected micronekton species in the vicinity of SE Hancock

(number in parentheses indicate rank among top five species)

Summer (Jul-Aug '84) Winter (Jan-Feb '85)

Cobb trawls at large-scale frontal systems, SAFZ August 1991Cobb trawls at large-scale frontal systems, SAFZ August 1991

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Subarctic Frontal Zone

"Subarctic Boundary"

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Salinity (PSU)

32 33 34 35 36

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46°N

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38°N

F t = 23.0

F t = 24.0

Ft = 25.0

Ft = 26.0 Ft = 27.0 Ft = 28.0

F t = 22.0

179°30'W

Cobb trawls at large-scale frontal systems, STFZ February 1992Cobb trawls at large-scale frontal systems, STFZ February 1992

Salinity (PSS 78)33 34 35 36

Tem

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(°C)

5

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31°08.0'N152°55.6'W

29°18.7'N153°50.5'W

27°27.5'N 154°41.3'W

25°41.1'N155°42.3'W

23°40.1'N156°34.4'W

21°45.5'N157°14.6'W

Ft= 23.0

F t= 24.0

Ft= 25.0

Ft= 26.0 Ft= 27.0 Ft= 28.0

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dorsal mantle length (mm)

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freq

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Onychoteuthis borealijaponicaOnychoteuthis sp. D

Northern Transition Zone

0

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Subarctic Domainn = 5

n = 8

n = 99n = 23

n = 51

Onychoteuthis sp. D & O. borealijaponica

• South spawning – north feeding migrations

• Spatially complementary distributions

• Past reports of extensive distribution likely a composite of 2 species

Cruise objectives:Cruise objectives: to conduct the sampling for a to conduct the sampling for a

gear comparison and to gain gear comparison and to gain a subtropical perspective of a subtropical perspective of the micronekton communitythe micronekton community

use the benign weather and use the benign weather and sea conditions to evaluate sea conditions to evaluate and refine the protocols, and refine the protocols, logistics, and design of the logistics, and design of the experimentexperiment

PICES Micronekton Inter-calibration Experiment (MIE)NOAA ship Oscar Elton Sette cruise 04-13

October 6-13, 2004

Micronekton Intercalibration Experiment – 1 Cruise participants

Michael P. Seki Evgeny Pakhomov Daniel Curran Larissa PakhomovaDonald R. Hawn University of British ColumbiaReka Domokos Dept. Earth & Ocean Sciences National Marine Fisheries Service, NOAA Pacific Islands Fisheries Science Center

Richard Brodeur Hiroki Yasuma National Marine Fisheries Service, NOAA Masayuki AbeNW Fisheries Science Center, Newport OR Hokkaido University

Graduate School of Fisheries Sciences & Faculty of FisheriesDoug Yelland Institute of Ocean Sciences Andrei Suntsov Department of Fisheries & Oceans, Canada Harbor Branch Oceanographic Institution

140 m140 m22 “Stauffer modified” “Stauffer modified” pelagic Cobb trawlpelagic Cobb trawl

Sampling gears

1.8 m IKMT

2 m Hokkaido University Rectangular Frame Trawl

MIE-1, operations tracksMIE-1, operations tracks

EK-60 38 kHz echogram, 9 October 2004:EK-60 38 kHz echogram, 9 October 2004:

Day tows ≈ 550 m

Night tows ≈ 120 m

One series night tows ≈ 550 m

NightDayNightDayNightDay

321.254390.104318.828428.696288.191472.704

6' IKMTHU-RTCobb TrawlSimrad EK-60 38 kHz, avg Nautical Area Scattering Coefficients (m2•nmi-2)

Sampling Distribution:17 Cobb trawls19 IKMTs20 HU-RFTs

0.1

1

10

100

1000

Euphau

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Mysidac

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Decapoda

Stomatopoda

Oegopsid

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Tunicata

Myctophidae

Total fish

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Den

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(ind

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cobb HN IKTNight sampling

IKMT

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100

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Gear-types for Gear-types for intercomparison (what is intercomparison (what is micronekton?): micronekton?):

MIE-1 – “what one MIE-1 – “what one defines as micronekton defines as micronekton ≠ another”; enabled all ≠ another”; enabled all size range evaluation of size range evaluation of multiple acoustic multiple acoustic λλssMIE-2 – ‘appropriate’ MIE-2 – ‘appropriate’ gear of similar mesh gear of similar mesh sizes; standard gear sizes; standard gear (RMT 1+8, IKMT?); (RMT 1+8, IKMT?); towed acoustics (high towed acoustics (high frequencies)frequencies)

Opisthoproctus soleatus

Oplophorus gracilirostris

Abralia trigonura

What now?What now?

● Advances in technologyAdvances in technology● Signal strength (acoustics)Signal strength (acoustics)● Time series – observation systemsTime series – observation systems● Refined trophic linksRefined trophic links● Ecosystem rolesEcosystem roles