Content uploaded by A. M. Orlov
Author content
All content in this area was uploaded by A. M. Orlov on Mar 25, 2022
Content may be subject to copyright.
68
ISSN 0001-4370, Oceanology, 2022, Vol. 62, No. 1, pp. 68–79. © Pleiades Publishing, Inc., 2022.
Russian Text © The Author(s), 2022, published in Okeanologiya, 2022, Vol. 62, No. 1, pp. 85–97.
Mesopelagic Micronekton and Macroplankton and the Conditions
of Its Habitat in the Northeastern Pacific Ocean
A. S. Kurnosovaa, *, A. A. Somova, A. N. Kanzeparovaa, M. A. Zueva, S. Yu. Orlovab, c,
D. S. Kurnosova, and A. M. Orlovb, c, d, e, f, g
a Russian Federal Research Institute of Fisheries and Oceanography, Pacific Branch (TINRO), Vladivostok, Russia
b Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia
c Russian Federal Research Institute of Fisheries and Oceanography, Moscow, Russia
d Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia
e National Research Tomsk State University, Tomsk, Russia
f Dagestan State University, Makhachkala, Russia
g Caspian Institute of Biological Resources, Dagestan Federal Research Center, Russian Academy of Sciences,
Makhachkala, Russia
*e-mail: anna.vazhova@gmail.com
Received February 2, 2021; revised March 10, 2021; accepted April 8, 2021
Abstract—The article analyzes differences in the vertical structure of waters and hydrochemical parameters at
three oceanic stations in the northeastern Pacific. Data on the species composition of mesopelagic fishes,
squids, and gelatinous organisms making diurnal vertical migrations to the epipelagic zone are given. Differ-
ences in their ratio and size composition at different stations are analyzed. The species ratio and size and total
biomass of micronekton and macroplankton change in the southwestern direction, which is primarily deter-
mined by the variability of the oceanological characteristics of the subsurface layer.
Keywords: Northeast Pacific, hydrology, hydrochemistry, epipelagic zone, vertical water structure, mesope-
lagic fishes, cephalopods, gelatinous organisms, micronekton, macroplankton
DOI: 10.1134/S0001437022010076
INTRODUCTION
In the open ocean, the vertical and horizontal tem-
perature, salinity, light, and pressure gradients, and
the hydrochemical characteristics govern the peculiar
life features at different depths [14]. One of the most
densely populated and species-rich zones in the World
Ocean is the mesopelagic; mesopelagic micronekton
and macroplankton (fishes, squids, gelatinous organ-
isms, etc.) are widespread at depths of over 200 m from
Svalbard and the northern Bering Sea to the Antarctic
ice shelves [10, 14]. The mesopelagic zone fauna is
extremely rich in species [2, 18, 20, 23]. There are
about 200 mesopelagic fish species in the Subarctic
part of the Pacific Ocean alone [19]; among them,
there are over 50 lanternfish species (family Mycto-
phidae) in the Pacific [14].
Vertical diurnal migrations from the mesopelagic
to the epipelagic zone are a distinctive feature of many
mesopelagic species [9]; this determines the relation-
ship between the meso- and epipelagic zones via the
transfer of matter and energy [9, 17, 19, 25, 34, 36, 37,
39, 40].
According to the estimates of many authors, the
resources of the mesopelagic zone in the World
Ocean (except squids) are enormous and can reach 1
billion tons; in the Pacific Ocean, they are estimated
at more than 300 million tons [7, 23, 24, 27]. Taking
into account the most recent acoustic studies, their
abundance may be even higher, since estimates
derived by trawl may actually be two orders of mag-
nitude higher [26]. The resources of the mesopelagic
zone are currently considered promising for fisheries
as a source of feed for aquaculture [32].
Despite a high interest in mesopelagic micronec-
ton and macroplankton and a large volume of related
studies, the species of this group are still poorly stud-
ied. The features of their spatial distribution, biology,
state of stocks, species structure, and relationship with
certain water masses of mesopelagic fauna remain
largely unclear [2, 20, 25, 35, 36]. This is especially
typical of the open oceanic waters of the East Pacific,
where studies are carried out extremely rarely and
irregularly.
The objective of this research is to obtain new data
on the composition, ratio, and size of species and bio-
MARINE BIOLOGY
OCEANOLOGY Vol. 62 No. 1 2022
MESOPELAGIC MICRONEKTON AND MACROPLANKTON AND THE CONDITIONS 69
mass of mesopelagic micronekton and macroplankton
in the open waters of the northeastern Pacific, taking
into account their habitat conditions.
MATERIALS AND METHODS
This communication is based on the results of stud-
ies performed in March 2019 in the open waters of the
Northeast Pacific on the R/V Professor Kaganovsky
(Fig. 1), carried out while sailing between Vancouver
(Canada) and the area of the Emperor Seamounts [13].
CTD data were acquired with a Sea Bird Electron-
ics hydrological set (model 25) (SBE 25) at a depth of
up to 500 m; samples were collected at standard depths
to determine the concentration of dissolved oxygen,
silicates, and mineral forms of phosphorus and nitro-
gen. Chemical measurements were carried out accord-
ing to standard methods recommended for studying
waterbodies and World Ocean areas promising for
fishing [12]. Data were processed with the standard
SBE 25 software and Ocean Data View v.4.7.1. The
geostrophic map of the Northeast Pacific was made
using data from analysis of OSCAR satellite informa-
tion (https://podaac.jpl.nasa.gov/dataset/OSCAR_
L4_OC_third-deg), as well as Surfer 11 software
(Golden Software, Inc.).
To analyze the oceanological situation in the study
area, we also used the average monthly values from
analysis of satellite data on the physical parameters for
March 2019 from http://marine.copernicus.eu. Com-
parative analysis of the vertical water structure was
based on sounding data from stations 99 and 100. At
station 98, sounding was not carried out for technical
reasons; therefore, the vertical temperature and salin-
ity distributions at this station were estimated from
satellite data on the physical parameters of water
(GLOBAL_ANALYSIS_FORECAST_PHY_001_024).
To use the model data for the vertical structure at station
98, we compared the instrumental and model tempera-
ture and salinity data for stations 99, 100, and A.
The data of ichthyological studies are based on the
results of 1-h-long trawl hauls using a mid-water
RT 80/396 trawl with a fine-mesh (10 mm) insert;
trawls were successively performed at three strata (60–
90, 30–60, and 0–30 m), 20 min per stratum (Table 1).
Each station was sampled during the twilight period
(when mesopelagic fish and squids actively migrate to
the epipelagic zone).
A total of 1700 animals were studied: 201 specimens
were subjected to biological analysis and 1499 speci-
mens were measured. The relative abundance/bio-
mass of hydrobionts was calculated using the areal
method [1], which takes into account the opening of
the horizontal trawl, average trawl speed and duration,
abundance/weight of the particular species in the
catch, and catchability coefficient for each species [3].
Comparison of the species and numerical compo-
sition of squids was based on the materials from the
Marine Biology database, corresponding to the sta-
tions near the study area.
RESULTS
Hydrological and Hydrochemical Studies
Water dynamics. The study area is located in the
zone of the North Pacific (Subarctic) Current, which
slows down as it approaches North America (Fig. 2).
Weak cyclonic and anticyclonic gyres can be observed
in this zone due to slowing of the current. The current
map (see Fig. 2) in the Northeast Pacific makes it pos-
sible to determine the elements of the f ield of geos-
trophic currents (eddy formations) within the survey. All
the sampled stations are in areas with low current veloc-
ities. The highest current velocities (up to 0.15 m/s) were
recorded near station 100, while the lowest current
velocities (0.05 m/s) were observed near station 98.
The scheme of the geostrophic component of currents
on the surface of the study area shows that station 99 is
Fig. 1. Sketch map of stations in open waters of Northeast Pacific (numbers indicate number of integrated stations; A, oceano-
logical station for comparison of hydrological parameters).
60°
N
55°
50°
45°
40°
35°
140°140°160°160°180 °120°W E
Ocean data view
100
99
98
A
70
OCEANOLOGY Vol. 62 No. 1 2022
KURNOSOVA et al.
located on the border of the anticyclonic gyre with
current velocities within 0.1 m/s.
Spatial distribution of hydrological parameters.
Satellite data of temperature and salinity distribu-
tion on the surface, modeled to a 250 m depth,
demonstrate a wide range of thermohaline parameters
in the studied area (Fig. 3). Thus, the average tem-
perature values from the surface to 100 m varied from
7 to 12°C and average salinity values from 32.5 to
33.5‰, thereby forming a fairly uniform upper layer.
The map of spatial distribution of surface temperature
shows that the studied stations 98, 99, and 100 were
approximately in the same temperature field of 8.7–
9.2°C; however, the salinity in the surface layer varied
from 32.5 to 33.2‰. At station A, which was selected
for the comparison as a point with a Subarctic water
structure, the values of temperature and salinity on the
surface were 7.5°C and 32.5‰. In the subsurface layer
(250 m), the water masses clearly differed in tempera-
ture (from 6.5 to 8.5°C) but were almost homogeneous
in salinity (33.9–34.1‰) (see Fig. 3).
Vertical distribution of hydrological parameters. To
use the model data for the vertical structure at station 98,
we compared the instrumental and model data on
temperature and salinity for stations 99, 100, and A
(Fig. 4). The correlation coefficient of vertical varia-
tion of the parameters was 0.91–0.99 for temperature
and 0.94–0.99 for salinity. The model data are pre-
sented as average monthly averaging. Therefore,
although the values differed slightly, the vertical struc-
ture of the model thermohaline parameters for sta-
tions A and 98 proved to be very similar in the presence
of a homogeneous mixed layer up to the 100 m horizon
and in an increased subsurface salinity below the den-
sity jump. The model estimates and in situ thermoha-
line values also proved to be similar for stations 99 and
Fig. 2. Diagram of currents in Northeast Pacific (March 29, 2019), calculated using OSCAR model.
North Pacific
Current
Alaska Current
California Current
Current speeds, m/s
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
60
16516015 515015 5150 145135
140
N
55
50
45
40
E
100
99
98
A
Table 1. Characteristics of stations and trawls during studies in open waters of Northeast Pacific
Trawl num b er
Date
Trawl s tar t
time UTC Traw l
end time
Trawl
coordinates
Speed,
knots
Course, deg
Depth, m
Surface
temperature, °C
Vertical trawl
opening, m
Horizontal trawl
opening, m
98 26.03 18:32 (+14) 04:32 19:32 45°02.0 N
143°18.6 W
4.3 194 4500 9.2 32.7 45.2
99 28.03 18:37 (+13) 05:37 19.37 43°10.0 N
152 °24.0 W
3.9 258 5100 9.1 33.7 44.5
100 31.03 18:38 (+13) 05:38 19:38 41°16.2 N
161°20.0 W
4.0 253 5500 8.7 33.7 43.0
OCEANOLOGY Vol. 62 No. 1 2022
MESOPELAGIC MICRONEKTON AND MACROPLANKTON AND THE CONDITIONS 71
100, which makes it possible to compensate the
absence of model data with the respective values from
station 98.
The vertical temperature profiles at stations A, 98,
and 99 are interpreted as a Subarctic structure typical
of this area, although the SST and salinity values were
higher at station 99 than at station 100 which is located
southward (Fig. 5). However, the increase in salinity
values in the subsurface layer at stations 99 and 100
indicate the subtropical origin of waters. The surface
water at stations 99 and 100 had a rather low tempera-
ture (typical of Subarctic water) but still a high salinity
(typical of subtropical water).
At stations A and 99, the predominantly Subarctic
origin of water masses is also confirmed by the mea-
sured hydrochemical parameters: a high dissolved
oxygen concentration (6.5–6.9 mL/L) in the upper
100-m layer and a high concentration of mineral phos-
phorus typical of subpolar waters (0.6–1.5 μM/L) and
nitrogen (6.8–9.5 μM/L) (Table 2).
The features of the vertical thermohaline structure
at station 100 indicate a subsurface increase in the dis-
solved oxygen concentration (by 0.1–0.2 ml/L) at this
station due to the spread of Subarctic surface waters
causing subtropical waters to veer to the south. The
recorded southwestward decrease in the hydrochemi-
Fig. 3. Distribution of thermohaline parameters on surface (top) of studied area and at 250 m layer (bottom).
Surface
S, ‰
Т, °С
250 m 250 m
46°
N
42°
38°
165°145°160°150°155°140°W
100
99
98
A
Т, °С
46°
N
42°
38°
165°145°160°150°155°140°W
100
99
98
A
Surface
46°
N
42°
38°
165°145°160°150°155°140°W
100
99
98
A
S, ‰
46°
N
42°
38°
165°145°160°150°155°140°W
100
99
98
A
Fig. 4. Comparison of vertical profiles of temperature (left) and salinity (right) for stations A and 98 (dots indicate values on horizons).
0
50
100
150
200
250
300
350
400
450
500
45678910
Depth, m
98
Temp., model
Temp., in situ
Temp., model
А
0
50
100
150
200
250
300
350
400
450
500
32.3 32.8 33.3 33.8
98
Salinity, model
Salinity, in situ
Salinity, model
А
72
OCEANOLOGY Vol. 62 No. 1 2022
KURNOSOVA et al.
cal parameters below the thermocline (from station 98
to station 100) also indicates a change in the water
structure in the subsurface layer in the studied frontal
zone.
Species composition and ratio in catches. Catches
from the three oceanic stations included 14 f ish spe-
cies, six cephalopod species (squids), and three gelati-
nous species (jellyfish and ctenophore). The maxi-
Fig. 5. Vertical profiles of temperature (left) and salinity (right) at studied stations according to model estimates (top) and in situ
(bottom).
0
50
100
150
200
250
300
350
400
450
468
Temperature, °С
10
Depth, m
0
50
100
150
200
250
300
350
400
450
32.0 32.5 33.0 33.5
Salinity, ‰
34.0 34.5
0
50
100
150
200
250
300
350
400
450
46810
Depth, m
0
50
100
150
200
250
300
350
400
450
32.0 32.5 33.0 33.5 34.0 34.5
98
99
100
A
99
100
A
99
100
98
99
100
Tabl e 2. Values of hydrochemical parameters at studied stations (O2, dissolved oxygen; Si, dissolved silicon (silicates); DIP,
dissolved inorganic phosphorus (phosphates); DIN, dissolved inorganic nitrogen (nitrites + nitrates))
Depth, m
O2 mL/L O2% Si, μM/L DIP, μM/L DIN, μM/L
A 99 100 A 99 100 A 99 100 A 99 100 A 99 100
0 6.85 6.64 6.65 101.5 101.6 100.9 12.57 12.06 19.24 0.89 0.69 0.66 11.54 7.09 9.15
25 6.56 6.66 6.73 97.2 102.0 102.1 13.85 11.29 16.67 0.89 0.58 0.62 13.15 6.39 9.20
50 6.95 6.46 6.69 103.0 98.7 101.4 12.83 11.03 16.93 0.89 0.62 0.62 13.46 7.59 9.54
100 6.78 6.93 6.82 99.7 106.0 106.5 15.13 11.29 12.31 0.97 0.66 0.54 13.23 7.31 6.76
150 5.90 5.16 5.47 84.5 79.2 85.9 28.73 23.60 16.16 1.27 0.97 0.69 20.85 16.57 11.59
250 4.99 5.40 5.33 69.7 79.4 81.5 41.55 35.65 27.45 1.62 1.31 1.04 28.13 22.18 19.46
500 1.92 1.88 2.76 26.2 26.0 39.0 80.54 82.08 67.72 2.32 2.39 2.05 36.25 39.25 33.25
OCEANOLOGY Vol. 62 No. 1 2022
MESOPELAGIC MICRONEKTON AND MACROPLANKTON AND THE CONDITIONS 73
mum abundance and biomass of all hydrobionts were
recorded at the central station (99), except Onycho-
teuthis borealijaponica and Corolla calceola (Table 3).
Squids prevailed in all trawl catches both in abundance
and biomass; their maximum abundance was observed
at the easternmost station, while their biomass was
maximal at the westernmost station. The fish abun-
dance and biomass in catches was 16–45 and 25–41%,
respectively. The proportion of jellyfish was low in
catches; their abundance and biomass decreased from
east to west (Fig. 6).
Among captured fishes, Lestidium ringens (mainly
juveniles) dominated in abundance (31.8% of the total
number of individuals) and Nannobrachium ritteri
dominated in biomass (19.2%). Among squids, the
highest abundance and biomass in catches were
recorded for Abraliopsis felis (81.1 and 90.7% of the
total number and weight of squids in catches and 48.6
and 57.1% in the total catch, respectively). Among
gelatinous species, Corolla calceola dominated in
abundance and biomass—89.2 and 58.9%, respec-
tively.
Table 3. Species composition of catches and distribution density of micronekton and macroplankton in upper epipelagic
zo ne o f op en water s of nor thea stern Paci fi c on Mar ch 26– 31, 2019 ( relat ive ab und anc e, ind. /km 2/relative biomass, kg/km2)
Species
Station no.
98 99 100
Diaphus theta 2639/2.9 57340/102.9 27814/38.7
Nannobrachium ritteri 83/0.2 47073/150.7 628/0.6
Lestidium ringens 69/0.1 29884/15.5 16/0.2
Nansenia candida 1972/12.8 16490/50.8 2606/7.8
Notoscopelus japonicus – 6783/44.9 4175/24.0
Stenobrachius leucopsarus 1500/1.4 36713/73.5 –
Symbolophorus californiensis 28/0.1 560/1.4 22069/48.6
Tarletonbeania crenularis 1722/4.3 15307/48.9 1381/4.2
Congriscus megastomus 1667/75.3 2178/36.7 1570/36.4
Abraliopsis felis 37042/114.9 209 794/662.0 105585/453.8
Boreoteuthis borealis 7195/16.7 10236/22.1 188/11.3
Okutania anonycha 3612 /3 .1 31 735 /31. 7 27 9 40 /3 0.1
Onychoteuthis borealijaponica 83/2.2 31/0.8 157/6.2
Atolla wyvilei 28/0.3 62/0.1 31/0.3
Corolla calceola 5584/6.1 156/0.2 126/0.1
Hormiphora cucumis 306/2.2 124/0.4 157/1.3
Total 63531/242.8 431597/1227.2 194 442/663.5
Fig. 6. Ratio of main groups of organisms in catches by abundance (a) and biomass (b) at different stations.
Fishes Cephalopods Gelatinous species
15.3
46 31
75.4
53.9
68.8
9.3 0.1 0.2
0
10
20
30
40
50
60
70
80
90
100
(a)
%
98 99 100
40.2 42.22 24.6
56.3 57.73 75.1
3.5 0.05 0.3
0
10
20
30
40
50
60
70
80
90
100
%
(b)
98 99 100
74
OCEANOLOGY Vol. 62 No. 1 2022
KURNOSOVA et al.
The proportion of Nansenia candida in catches
consistently decreased from east to west both in abun-
dance and biomass, while the proportion of three spe-
cies, Diaphus theta, Notoscopelus japonicus, and Steno-
brachius leucopsarus, increased in this direction. High
abundance and biomass of Nannobrachium ritteri was
recorded at the central station (99). Symbolophorus
californiensis was almost completely absent at the first
two stations (98 and 99) (Fig. 7).
Among squids, the proportion of the dominant
species, Abraliopsis felis, did not significantly change
in all catches both in terms of abundance (77–82%)
and biomass (83–92%), while the proportion of other
squid species varied greatly. The abundance and
weight percentage of Boreoteuthis borealis gradually
decreased from east to west, while those of Okutania
anonycha, on the contrary, increased in this direction
(Fig. 7).
From east to west, the abundance and weight per-
centages of the jellyfish Corolla calceola decreased
from 94.4 to 40% and from 71.1 to 7.5%, respectively,
while those of ctenophore Hormiphora cucumis, on the
Fig. 7. Longitudinal changes in abundance (a) and biomass (b) of fishes, squids, and gelatinous organisms in catches.
Fishes
Squids
Gelatinous organisms
0
10
20
30
40
50
60
70
80
90
100
(a)%
98 99 100
0
10
20
30
40
50
60
70
80
90
100
(a)
%
98 99 100
0
10
20
30
40
50
60
70
80
90
100
(a)
%
98 99 100
Diaphus theta
Others
0
10
20
30
40
50
60
70
80
90
100
(b)%
98 99 100
Stenobrachius leucopsarus
Nansenia candida
Nannobrachium ritteri
Symbolophorus californiensis
Tarletonbeania crenularis
Notoscopelus japonicus
0
10
20
30
40
50
60
70
80
90
100
(b)
%
98 99 100
Abraliopsis felis
Boreoteuthis borealis
Okutania anonycha
Gonatus onyx
Chiroteuthis calyx
Onychoteuthis
borealijaponica
0
10
20
30
40
50
60
70
80
90
100
(b)
%
98 99 100
Hormiphora cucumis
Corolla calceola
Atolla wivillei
OCEANOLOGY Vol. 62 No. 1 2022
MESOPELAGIC MICRONEKTON AND MACROPLANKTON AND THE CONDITIONS 75
contrary, increased from 5.2 to 50% and from 24.4 to
77.4%, respectively. The weight percentage of the jel-
lyfish Atolla wivillei also increased from 3.5 to 15.1%
(Fig. 7).
Size composition. The largest known body length of
California headlightfish Diaphus theta is about 9 cm [2].
In our catches, this is the second largest species with
respect to the relative abundance and biomass, repre-
Fig. 8. Size composition of hydrobionts in catches at different stations (N, number of measured individuals; M, their average
length).
0
20
40
60
80
100
120
2.5 3.5 4.5 5.5 6.5
Body length, cm
Total series
98
99
100
N = 273 ind.
М = 5.1 cm
0
5
10
15
20
25
30
35
40
45
50
345678
Body length, cm
Total series
98
99
N = 127 ind.
М = 5.9 cm
0
10
20
30
40
50
60
5.5
6.5
7.5
8.5
9.5
10.5
11. 5
12.5
13.5
14.5
15.5
16.5
17. 5
18.5
19.5
20.5
21.5
Fish number, ind. Fish number, ind. Fish number, ind.
Fish number, ind.Fish number, ind.Squid number, ind.
Squid number, ind.
Squid number, ind.
Body length, cm
Total series
98
99
100
N = 175 ind.
М = 9.2 cm
0
10
20
30
40
50
60
70
80
90
100
345678
Body length, cm
Total series
98
100
N = 207 ind.
М = 7.3 cm
0
10
20
30
40
50
60
7.5 8.5 9.5 10.5 11.5 12.5
Body length, cm
Total series
99
100
N = 106 ind.
М = 9.5 cm
0
5
10
15
20
25
30
35
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5
Mantle length, cm
Total series
98
99
N = 76 ind.
М = 3.8 cm
0
10
20
30
40
50
60
70
80
2.0 2.5 3.0 3.5 4.0 4.5 5.0
Mantle length, cm
Total series
98
99
100
N = 205 ind.
М = 3.1 cm
0
200
400
600
800
1000
1200
1400
3.0 3.5 4.0 4.5 5.0 5.5
Mantle length, cm
Total series
98
99
100
N = 3405 ind.
М = 4.1 cm
Diaphus theta Stenobrachius leucopsarus
Nansenia candida Tarletonbeania crenularis
Notoscopelus japonicus Boreoteuthis borealis
Okutania anonycha Abraliopsis felis
76
OCEANOLOGY Vol. 62 No. 1 2022
KURNOSOVA et al.
sented by individuals 2.5 to 6.5 cm long (mean 5.1 cm)
(Fig. 8). Individuals with a length of 4.5–5.5 cm dom-
inated in catches (76.2%). The average fish length was
lower at the eastern and western stations (4.6 and
5.0 cm) than at the central one (5.8 cm).
The largest known body length of northern lamp-
fish Stenobrachius leucopsarus is about 9 cm [2]. It was
the third largest species in catches with respect to the
relative abundance and biomass and represented by
individuals from 3 to 8 cm long (mean 5.9 cm), among
which the size group of 5–7 cm prevailed (84.3% of
the total fish abundance) (Fig. 8). The average body
length increased from east to west. It was 5.1 cm at the
eastern station (99) and 6.4 cm at station 98.
The maximum known length of bluethroat argen-
tine Nansenia candida is 24 cm [28]. Its proportion in
catches consistently decreased from east to west; it was
represented by individuals with a length from 5.5 to
21.5 cm and dominated by the size group of 6.5–8.5 cm
(69.7%). The proportion of larger individuals with a
length of 14.5–15.5 cm was also noticeable (8.6%)
(Fig. 8). The average body length of N. candida
decreased from east to west. Thus, it was 10.1 cm at th e
eastern station, 8.5 cm at the central station, and 8 cm
at the western station. At the same time, there was a
clear sexual dimorphism in body length and weight:
females were much longer and heavier than males.
Thus, their average length was 14.3 and 10.3 cm and
body weight was 24.4 and 8.4 g, respectively.
The western blue lanternfish Tarletonbeania crenu-
laris reaches the maximum length of 8.4 cm [21]. In
our catches, this species was represented by individuals
from 3 to 8 cm long (mean 7.3 cm) and dominated by
the size group of 7–8 cm (86.5%) (Fig. 8). The lowest
average body length of the fish was recorded at the
eastern station (6.9 cm), while it was the same at the
central and western stations (7.6 cm). The females pre-
vailed in catches (76%); at the same time, there was no
significant sexual dimorphism in size: the average
length of males and females was 7.3 and 7.2 cm and
body weight was 3.4 and 3.5 g, respectively.
The largest known body length of Japanese lan-
ternfish Notoscopelus japonicus is about 15 cm [2]. In
catches, this species was represented by individuals
from 7.5 to 12.5 cm long (mean 9.5 cm); among them,
individuals of the size group of 8.5–9.5 cm dominated
numerically (94.3%) (Fig. 8). Japanese lanternfish
occurred at two stations and its average length
decreased from east to west. Thus, it was 10.1 cm at th e
central station and 9.4 cm at the western station. At the
same time, females were slightly longer than males (on
average, 9.4 and 9.0 cm, respectively) at an equal body
weight (on average, 6.0 g).
Being a polymorphic species, boreopacific squid
Boreoteuthis borealis in the North Pacific is repre-
sented by two intraspecific groups, the small-sized
and large-sized groups [29]. The maximum mantle
length (ML) of mature squids reaches 17.9 cm in the
small-sized group and 30.0 cm in females and 27.8 cm
in males from the large-sized group [6]. In our
catches, this species was represented by immature
individuals with ML from 2.4 to 7.2 cm (Fig. 8). The
average ML was almost the same in boreopacific squid
from the eastern and central stations, being 3.9 and
3.7 cm, respectively, while it was significantly longer at
the western station (5.2 cm). In addition, three larger
feeding females with mantle lengths of 12.5, 14.7, and
14.9 cm and one male with ML 13.7 cm were caught at
station 100.
Okutania anonycha is characterized by a small size;
its maximum mantle length is 15.0 cm [30]. At all sta-
tions, it was represented by juveniles with ML from 2.0
to 4.8 cm (Fig. 8). An increase in the average length of
the mantle of this squid was observed from east to
west. Thus, its average ML was 2.7 cm at the eastern
station, 2.9 cm at the central station, and 3.3 cm at the
western station.
The maximum length of the mantle of Abraliopsis
felis is 5.7 cm [16]. The catches contained individuals
with ML from 2.8 to 5.3 cm (Fig. 8); its average value
increased from east to west. It differed little at the east-
ern and central stations (3.9 and 4.0 cm, respectively)
and was 4.4 cm at the western station.
DISCUSSION
The sampled stations were a great distance from
each other on different sides of the Subarctic front, in
the dynamic frontal zone of mixing of Subarctic and
subtropical waters. Geographically, the study area
belongs to the Subarctic front, which is a boundary
between different water mass structures [4]. In this
frontal zone, waters of different structures mix with
each other, which leads to a transfer of warm surface
waters to the Subarctic zone and a reverse transfer of
deep cold Subarctic waters [11].
Vessel and satellite sounding data from the study
area show that the stations were in the high-gradient
part of the Subarctic front: at the northern station (98),
water masses had a clearly defined Subarctic structure,
station 99 was located in the water mixing zone, and
the southernmost station (100) was on the southern
periphery of the front with the transition to the transit
domain [22]. It is the subsurface layer that was charac-
terized by the main differences; as will be shown below,
this is more important than the characteristics of near-
surface waters during estimates of the composition and
abundance of micronekton and macroplankton.
The features of the vertical thermohaline structure
at stations 99 and 100 may be determined by the fact
that the surface Subarctic waters in this area were dis-
tributed far to the south and covered subtropical waters.
As shown above, the surface water at stations 99 and 100
had a rather low temperature (typical of Subarctic water)
but still a high salinity (typical of subtropical water). This
results from the “double diffusion” effect [8], i.e., when
OCEANOLOGY Vol. 62 No. 1 2022
MESOPELAGIC MICRONEKTON AND MACROPLANKTON AND THE CONDITIONS 77
the temperature exchange under the condition of hor-
izontal turbulence interaction is faster than the salinity
exchange due to the difference in the coeff icients of
turbulent exchange. On the whole, analysis of the
water structure at all studied stations indicates the
crossing of the dynamic frontal zone during the study
period.
As shown on the geostrophic map, the velocities of
the current on the surface in the frontal zone, where all
the stations were located, varied from 0.05 to 0.15 m/s
during the study period; however, it should be borne in
mind that currents are not so clearly defined below the
100-m layer, where mesopelagic migrants generally
live [8]. Therefore, it can be assumed that the species
distribution is more influenced by the vertical struc-
ture of waters below 100 m: subtropical waters at sta-
tions 99 and 100 and Subarctic waters at station 98.
Th e un steady an ticy cloni c eddy formed nea r station 9 9
can influence the quantitative composition of
micronekton, since planktonic organisms serving as
food items for different pelagic fishes are concentrated
in eddy systems [5, 31].
Therefore, it is likely that the vertical structure of
subsurface layer waters has a greater effect on the spe-
cies composition of micronekton and macroplankton.
At the same time, the biomass and size distribution is
partially influenced by currents and eddies, since these
species rise to the upper epipelagic layer at night, when
trawlings were conducted.
The results of ichthyologic studies suggest that the
features of the vertical structure of waters in the sub-
surface layer and eddy formations on the surface of the
studied area influenced the characteristic longitudinal
variability in the composition of catches. Thus, the
data on the species biomass and ratio indicate the vari-
ability in the composition of catches, which was
expressed in the biomass/abundance ratio both
between the main groups (fishes, squids, and gelati-
nous organisms) (see Table 3, Fig. 6) and within the
particular group. These longitudinal changes can be
illustrated by the example of the fish group and are
most clearly seen from the example of gelatinous mac-
roplankton (see Fig. 7).
Although it is difficult to assess the significance of
the influence of a certain environmental factor on the
composition of micronekton and macroplankton
catches based on the data from the three stations, our
own and literature data suggest the relationship
between the abundance and composition of their
communities and pattern of water masses. Thus, com-
parable data on mesopelagic fishes from the Pacific
Ocean were obtained in 1989 during the cruise of the
research fishery vessel (RFV) Poseidon [7]. Analysis of
the resources of the mesopelagic fishes from the North
Pacific based on the classification of water masses [22]
identified cenotic complexes. According to this classi-
fication, five domains were identified in the study
region. Our stations were apparently located between
the zones of the central Subarctic domain and transit
domain (according to [22]) or between the northern and
southern zones of the Pacific drift (according to [7]).
The main characteristics of this section between the Sub-
arctic and transit domains are extensive incursions of
cold freshened water along the northern boundary and
warm saline water along the southern boundary [22]. We
observed similar phenomena in our section; in partic-
ular, this was typical of the subsurface layer, since the
near-surface temperature was almost identical at all
stations.
Comparable data on squids were also obtained
during the already mentioned cruise of RFV Poseidon
in 1989; however, these data were not highlighted in
the literature. According to the materials of the
Marine Biology database, O. anonycha generally pre-
vailed in catches in 1989 (in contrast to our data); its
concentration in the water area covered by our study
varied from 22 to 480 kg/km2 during that time. In
2019, cephalopods were dominated by A. felis; their
concentrations varied from 114.9 to 662 kg/km2. In
both 1989 and 2019, the maximum squid and mesope-
lagic fish concentrations were observed in zones with
the highest gradient.
According to Karedin [7], the following dominant
species were identified for the studied water masses:
Diaphus theta (53%), Stenobrachius leucopsarus (22%),
and Nannobrachium ritteri (13%) in the zone of the
North Pacific drift and Ceratoscopelis warmingi (49%),
Diaphus perrspicillatus (21%), and Stenobrachius leu-
copsarus (5%) in the zone of the South Pacific drift.
According to our data, the species composition of
mesopelagic fishes differed slightly. The ratio of meso-
pelagic fishes at the three stations was as follows: Nan-
nobrachium ritteri (22%), Diaphus theta (21%), Steno-
brachius leucopsarus (16%), and Notoscopelus japoni-
cus (15%). If we compare only the data from trawl
hauls performed in 1989 near our stations, the similar-
ity of the species composition increases significantly.
However, the proportion of Tarletonbeania crenularis
and Nansenia candida, which were recorded among
the dominants in 2019, was insignificant in 1989. It
should be noted that the results of research in the Gulf
of Alaska in February–March 2019 also showed the
biomass dominance of T. c re n u l a ri s among mesope-
lagic fishes.
The average concentration of mesopelagic fishes
was 236 kg/km2 (21.8–488.6 kg/km2) at three stations
in 2019, while it was 442 kg/km2 at stations located
close to our stations in 1989. However, it should be
noted that catches on RFV Poseidon in 1989 were per-
formed using an experimental RT 93/500 mid-water
trawl with a small-mesh insert (10 mm) along the
entire length of the trawl net [7], rather than only in
the codend (as in our case), which might affect the
trawl catchability. In addition, trawl hauls in 1989 were
performed in summer, while we conducted them in
March. Although seasonal changes are not so clearly
78
OCEANOLOGY Vol. 62 No. 1 2022
KURNOSOVA et al.
defined in the remote areas of the ocean (the Subarctic
front zone) [15] as in the marginal seas, this might also
influence the abundance of mesopelagic fishes.
Since longitude and water masses are of great
importance among various factors influencing the
geographical distribution of interzonal species in the
open ocean [33, 38], analysis of the species structure
of mesopelagic fish catches [19] revealed its clear cor-
respondence to the characteristic water masses. How-
ever, trawls in our study covered the boundary zone
with an extremely high variability of oceanological
characteristics. Although the stations were at a rela-
tively close distance from each other (400 NM is a rel-
atively small distance on the oceanic scale), the hydro-
logical and hydrochemical parameters differed rather
significantly at the sampling points, especially in the
subsurface layer (deeper than 100 m), which is more
important than the characteristics of the surface layer
during estimates of the composition and abundance of
micronekton and macroplankton. This probably
determined significant variations in the abundance
and species and size composition of catches, although
trawl hauls were performed according to the same
scheme and at the same time. Based on the results of
our research, we believe that, in addition to the ran-
dom component, the species abundance and ratio in
catches were largely determined by the water structure.
REFERENCES
1. Z. M. Aksyutina, Elements of Mathematical Assessment
of the Observation Results in Biological Fishery Studies
(Pishchevaya Prom-st’, Moscow, 1968) [in Russian].
2. V. E. Bekker, Lanternfishes (Myctophidae) of the World
Ocean (Nauka, Moscow, 1983) [in Russian].
3. I. V. Volvenko, “Quantitative assessment of fish abun-
dance according to trawl surveys,” Izv. Tikhookean.
Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr. 124,
473–500 (1998).
4. L. I. Galerkin, M. B. Barash, V. V. Sapozhnikov, and
F. A . P a s t e r n ak , The Pacific Ocean (Mysl’, Moscow,
1982) [in Russian].
5. V. V. Zavoruev, E. N. Zavorueva, and S. P. Krum,
Plankton Distribution in the Areas of Frontal Zones of
Aquatic Ecosystems: Monograph (Siberian Federal Univ.,
Krasnoyarsk, 2012) [in Russian].
6. M. A. Zuev, O. N. Katugin, G. A. Shevtsov, et al.,
“Distribution and differentiation of the northern squid
Boreoteuthis borealis (Sasaki, 1923) (Cephalopoda: Go-
natidae) in the Sea of Okhotsk and northwestern part of
the Pacific Ocean,” Tr. VNIRO 147, 266–283 (2007).
7. E. P. Karedin, “Resources of mesopelagic fishes in the
northern part of the Pacific Ocean,” Izv. Tikhookean.
Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr. 124,
391–415 (1998).
8. V. N. Malinin, General Oceanology, Part 1: Physical
Processes (Russian State Hydrometeorological Univ.,
St. Petersburg, 1998) [in Russian].
9. N. V. Parin, Ichthyofauna of the Ocean Epipelagial
(Nauka, Moscow, 1968) [in Russian].
10. N. V. Parin, Fishes of the Open Ocean (Nauka, Moscow,
1988) [in Russian].
11. V. A . Ro z h ko v , Statistical Hydrometeorology: Manual
(St. Petersburg State Univ., St. Petersburg, 2015) [in
Russian].
12. V. V. Sapozhnikov, A. I. Agatova, N. V. Arzhanova,
et al., Manual on Chemical Analysis of Marine and Fresh
Waters during Environmental Monitoring of Fishery Res-
ervoirs and the Regions of the World Ocean Prospective for
Commercial Fishery (VNIRO, Moscow, 2003) [in Rus-
sian].
13. A. A. Somov, A. N. Kanzeparova, A. S. Vazhova, et al.,
“Some preliminary results of research on Emperor Sea-
mounts in April, 2019,” Tr. VNIRO 175, 208–219
(2019).
14. The Pacific Ocean, Vol. 7: Biology of the Pacific Ocean,
Book 3: Fishes of the Open Waters (Nauka, Moscow,
1967) [in Russian].
15. K. N. Fed oro v, Physical Nature and Structure of the
Ocean Fronts (Gidrometeoizdat, Leningrad, 1983) [in
Russian].
16. G. A. Shevtsov, O. N. Katugin, and M. A. Zuev, “Dis-
tribution of cephalopods in the subarctic frontal zone of
the northwestern part of the Pacific Ocean,” Issled.
Vodn. Biol. Resur. Kamchat. Sev.-Zap. Chasti Tikhogo
Okeana, No. 30, 64–81 (2013).
17. M. V. Angel, “Does mesopelagic biology affect vertical
flux?” in Productivity of the Oceans: Present and Past,
Ed. by W. H. Berger, V. S. Smetacek, and G. Wefer (Wi-
ley, New York, 1989), pp. 155–173.
18. V. Andersen, J. Sardou, and B. Gasser, “Macroplank-
ton and micronekton in the northeast tropical Atlantic:
abundance, community composition and vertical dis-
tribution in relation to different trophic environments,”
Deep Sea Res., Part I 44, 193–222 (1997).
19. R. J. Beamish, K. D. Leask, O. A. Ivanov, et al., “The
ecology, distribution, and abundance of midwater fish-
es of the Subarctic Pacific gyres,” Prog. Oceanogr. 43,
399–442 (1999).
20. R. D. Brodeur, M. P. Seki, E. A. Pakhomov, and
A. V. Suntsov, “Micronekton—what are they and why
they important?” PICES 13, 7–11 (2005).
21. Z. E. Bystydzieńska, J. A. Phillips, and T. B. Linkows-
ki, “Larval stage duration, age and growth of blue lan-
ternfish Tarletonbeania crenularis (Jordan and Gilbert,
1880) derived from otolith microstructure,” Environ.
Biol. Fish. 89, 493–503 (2010).
22. F. Favorite, “Oceanography of the Subarctic Pacific re-
gion 1960–1971,” Bull. Int. N. Pac. Commun. 33, 1–
187 (1976).
23. J. Gjøsæter and K. Kawaguchi, “A review of the world
resources of mesopelagic fish,” FAO Fish. Tech. Pap.
193, 1–151 (1980).
24. X. Irigoien, T. A. Klevjer, A. Røstad, et al., “Large me-
sopelagic fishes biomass and trophic eff iciency in the
open ocean,” Nat. Commun. 5, 3271 (2014).
https://doi.org/10.1038/ncomms4271
OCEANOLOGY Vol. 62 No. 1 2022
MESOPELAGIC MICRONEKTON AND MACROPLANKTON AND THE CONDITIONS 79
25. S. Kaartvedt, D. L. Aksnes, and A. Aadnesen, “Winter
distribution of macroplankton and micronecton in
Masfjorden, western Norway,” Mar. Ecol.: Prog. Ser.
45, 45–55 (1988).
26. S. Kaartvedt, A. Staby, and D. L. Aksnes, “Efficient
trawl avoidance by mesopelagic fishes causes large un-
derestimation of their biomass,” Mar. Ecol.: Prog. Ser.
456, 1–6 (2012).
27. V. W. Y. Lam and D. Pauly, “Mapping the global bio-
mass of mesopelagic fishes,” Sea Around Us Proj.
Newsl. 30, 4 (2005).
28. C. W. Mecklenburg, T. A. Mecklenburg, and L. K. Tho-
rsteinson, Fishes of Alaska (American Fisheries Society,
Bethesda, MD, 2002).
29. K. N. Nesis and N. P. Nezlin, “Intraspecific groupings
of gonatid squids,” Russ. J. Aquat. Ecol. 2 (2), 91–102
(1993).
30. T. Okutani, Cuttlefish and Squids of the World in Color
(Okumura, Tokyo, 1995).
31. A. M. Orlov, “Impact of eddies on spatial distributions
of groundfishes along waters off the northern Kuril Is-
lands, and southeastern Kamchatka (north Pacific
Ocean),” Ind. J. Mar. Sci. 32 (2), 95–113 (2003).
32. A. M. Orlov and N. I. Rabazanov, “Past, present and
future of deep-sea fisheries in the global oceans,” Mod.
App. Ocean. Petr. Sci. 3 (2), 255–257 (2019).
33. R. Proud, M. J. Cox, and A. S. Brierley, “Biogeography
of the global ocean’s mesopelagic zone,” Current Biol.
27, 113 – 11 9 ( 2 0 17 ) .
34. V. I. Radchenko, “Mesopelagic fish community sup-
plies “biological pump,” Raffles Bull. Zool. Suppl. 14,
265–271 (2007).
35. B. H. Robinson, “Deep pelagic biology,” J. Exp. Mar.
Biol. Ecol. 300, 253–272 (2004).
36. E. H. Sinclair and P. J. Stabeno, “Mesopelagic nekton
and associated physics of the southern Bering Sea,”
Deep Sea Res., Part II 49, 6127–6145 (2002).
37. H. Sugisaki and A. Tsuda, “Nitrogen and carbon stable
isotopic ecology in the ocean: the transportation of or-
ganic materials through the food web,” in Biogeochem-
ical Processes and Ocean Flux in the Western Pacific, Ed.
by H. Sakai and Y. Nozaki (Terra Scientific, Tokyo,
1995), pp. 307–317.
38. J. E. van Noord, R. J. Olson, J. V. Redfern, et al.,
“Oceanographic inf luences on the diet of 3 surface-mi-
grating myctophids in the eastern tropical Pacific
Ocean,” Fish. Bull. 114 (3), 274–287 (2016.
39. H. Watanabe, M. Moku, K. Kawaguchi, et al., “Diel
vertical migration of myctophid fishes (family Mycto-
phidae) in the transitional waters of the western North
Pacific,” Fish. Oceanogr. 8 (2), 115–127 (1999).
40. M. J. Willis and W. G. Pearcy, “Vertical distribution
and migration of fishes of the lower mesopelagic zone
of Oregon,” Mar. Biol. 70 (1), 87–98 (1982).
Translated by D. Zabolotny
