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In this study we present the most complete description of color variation, morphometric and mer� istic characters for the rare deep�sea North Atlantic Jensen’s skate Amblyraja jenseni, based on analyses of a wide range of accessible material. Comparisons of external morphological characters of male and female specimens of varying sizes and from different regions of the North Atlantic indicated regional morphological differences likely due to prolonged geographic isolation of local populations of this species. The vast majority of individuals exhibited a “dark” coloration, with a less common “light” coloration observed particularly among skates from the waters of the northeast and northwest Atlantic. Only dark�colored skates were found in the waters of the Mid�Atlantic Ridge. We also provide new data on the habitat, vertical distribution and size of the Jensen’s skate
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ISSN 00329452, Journal of Ichthyology, 2015, Vol. 55, No. 4, pp. 478–496. © Pleiades Publishing, Ltd., 2015.
478
12
INTRODUCTION
The Jensen’s skate
Amblyraja jenseni
(Bigelow and
Schroeder, 1950) is common among the deepwater
skate fauna of the North Atlantic, yet until recently
was not been well documented. Many species of deep
water skates were described in the second half of the
last century and until recently, many of these were
known only from a few specimens (Orlov et al., 2006;
Orlov and Cotton, 2013; Orlov, 2014). Likewise, the
Jensen’s skate was described from the waters of New
England and Nova Scotia as
Raja jenseni
in the middle
of the last century (Bigelow and Schroeder, 1950).
Subsequently, it was marked by occasional captures in
the waters of the Northwest Atlantic (NWA) (Bigelow
and Schroeder, 1953; Tempelman, 1965; Leim and
Scott, 1966; Moore et al., 2000; Alpoim et al., 2002;
Coad and Reist, 2004; Sulak et al., 2009; Halliday
et al., 2012; Kenchington et al., 2013, Vázquez et al.,
2013), the waters around Greenland (Karrer, 1976;
Nielsen and Bertelsen, 1992; Møller et al., 2010), the
Northeast Atlantic (NEA), to the west of the British
Isles (Gordon and Duncan, 1987, 1989; Quero et al.,
1
The article is published in the original.
2
Materials of the paper were presented at the 16th annual scien
tific conference of the European Elasmobranch Association
(Milan, Italy, November 22–25, 2012).
2000; George and Zidowitz, 2006; Neat et al., 2008;
Johnston et al., 2010; Séret, 2010; Silva et al., 2012)
and the MidAtlantic Ridge (MAR) (Orlov et al.,
2006; Cousins et al., 2013). The IUCN (World Con
servation Union) classifies Jensen’s skate as “Least
concern” (Kulka et al., 2008; Goodwin, 2012), i.e.
currently there are no potential threats to the species
and the population appears to be stable.
Information on the external morphology of
Jensen’s skate was initially limited to the description of
the holotype and two paratypes (Bigelow and
Schroeder, 1927, 1950, 1953), with additional mor
phometric data recently added from nine specimens
from the NWA and MAR (Orlov et al., 2006). Infor
mation on sexual dimorphism in external morpholog
ical characters was also described recently from seven
females and six males (Orlov and Cotton, 2011). Prior
to the present study, ontogenetic and geographic vari
ation in meristic and morphometric features and vari
ations of color remained largely undocumented for
this species. Such an analysis reveals intraspecific vari
ation in external morphology during ontogeny and
geographical variations, which is important for taxo
nomic studies, as well as the development of identifi
cation keys and field guides. Because the available tax
onomic information to date on the Jensen’s skate is
New Data on the Rare DeepSea Skate
Amblyraja jenseni
(Rajidae)
from the North Atlantic Ocean
1, 2
A. M. Orlov
a
,
b
and C. F. Cotton
c
a
Russian Federal Research Institute of Fisheries and Oceanography (VNIRO),
ul. Verkhnyaya Krasnosel'skaya 17, Moscow, 107140 Russia
b
Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences (IPEE RAS),
pr. Leninskii 33, Moscow, 119071 Russia
c
Florida State University Coastal and Marine Lab, 3618 Coastal Hwy 98, St. Teresa, FL, USA
email: orlov@vniro.ru
Received January 15, 2015
Abstract
—In this study we present the most complete description of color variation, morphometric and mer
istic characters for the rare deepsea North Atlantic Jensen’s skate
Amblyraja jenseni
, based on analyses of a
wide range of accessible material. Comparisons of external morphological characters of male and female
specimens of varying sizes and from different regions of the North Atlantic indicated regional morphological
differences likely due to prolonged geographic isolation of local populations of this species. The vast majority
of individuals exhibited a “dark” coloration, with a less common “light” coloration observed particularly
among skates from the waters of the northeast and northwest Atlantic. Only darkcolored skates were found
in the waters of the MidAtlantic Ridge. We also provide new data on the habitat, vertical distribution and size
of the Jensen’s skate.
Keywords
: Jensen’s skate,
Amblyraja jenseni
, external morphology, color, morphometrics, meristics, dimor
phism, North Atlantic
DOI:
10.1134/S0032945215040086
JOURNAL OF ICHTHYOLOGY
Vol . 55
No. 4
2015
NEW DATA ON THE RARE DEEPSEA SKATE
Amblyraja jenseni
479
extremely limited (Bigelow and Schroeder, 1927,
1950, 1953; Leim and Scott, 1966; Orlov et al., 2006,
2010; Sulak et al., 2009; Séret, 2010; Orlov and Cot
ton, 2011; Ebert and Stehmann, 2013), this type of
information is badly needed for this species.
Since the original reporting of this species from the
MAR (Orlov et al., 2006), other specimens have been
discovered in museum collections, thus expanding the
information available on the external morphology,
color, habitat, bathymetric distribution and sizes of the
Jensen’s skate. In this paper we examine and analyze
the full complement of available material to update the
information available for this rare skate.
MATERIALS AND METHODS
Between 2005 and 2010, we examined 19 speci
mens of Jensen’s skate from various field collections
and museums for the analysis of external morphologi
cal characters (Table 1). For comparison, we also
included data on the external morphological features
of the holotype and two paratypes (Bigelow and
Schroeder, 1927, 1950, 1953). Our analysis was based
on 42 morphometric and 11 meristic characters (Table 2).
All measurements were performed in accordance with
conventional techniques for skates (Bigelow and
Schroeder, 1953; Hubbs and Ishiyama, 1968) follow
ing the protocols used in other recent studies of exter
nal morphology of skates (Stehmann and Merrett,
2001; Orlov et al., 2006; Stehmann et al., 2008). Anal
ysis of color variation was performed on fresh speci
mens (from the MAR) as well as fixed specimens from
museum collections (from the NWA and NEA).
To analyze the spatial and vertical distribution and
size composition we used all available data from pub
lished and unpublished sources (of 114 captures,
>130 specimens). Unpublished data included infor
mation collected during scientific surveys on Scottish
and Irish vessels (Francis Neat and Graham Johnston,
unpublished data). In addition, we incorporated data
from the online databases, FishBase (http://www.fish
base.org), OBIS (Ocean Biogeographic Information
System, http://www.iobis.org) and GBIF (Global
Biodiversity Information Facility, http://www.
gbif.org), as well as imagery captured by the ROBIO
Lander (Cousins et al., 2013).
The following morphological abbreviations are
used throughout the manuscript:
V
,
C
,
DI
and
DII
rep
resent pelvic, caudal, first dorsal and second dorsal
fins (respectively) and
TL
represents the total length of
the body.
RESULTS AND DISCUSSION
General Characteristics of the External Morphology
Studies of external morphological characters of the
Jensen’s skate were previously limited to the descrip
tion of the type series (Bigelow and Schroeder, 1927,
1950, 1953), three specimens from the MAR, and six
specimens from the NWA (Orlov et al., 2006), as well
as the description of sexual dimorphism in seven
females and six males (Orlov and Cotton, 2011). The
Table 1.
Specimens of Jensen’s skate
Amblyraja jenseni
examined
No Catalogue
number
TL
, mm Sex Area
1MRI 851 845 NEA
2 MRI 803 686 NEA
3MRI 801 604 NEA
4 MRI 805 542 NEA
5MRI 878 833 NEA
6MRI 893 629 NEA
7 MCZ 138020A 369 NWA
8 MCZ 138020B 270 NWA
9MCZ 37899 615 NWA
10 MCZ 165045 na NWA
11 MCZ 132506 510 NWA
12 MCZ 155628 675 NWA
13 MCZ 165044 na NWA
14 MCZ 55011 473 NWA
15 MCZ 38354 691 NWA
16 ZMUB 19462 1065 MAR
17 ZMUB 19529 696 MAR
18 ZMUB 19463 1113 MAR
19 VIMS 11757 1035 MAR
20 USNM 35592* 541 NWA
21 USNM 23483* 850 NWA
22 USNM 33457* 223 NWA
NEA—NorthEast Atlantic, NWA—NorthWest Atlantic,
MAR—MidAtlantic Ridge; MRI—Marine Research Institute,
Galway, Ireland; MCZ—Museum of Comparative Zoology, Har
vard, USA; ZMUB—Zoological Museum of the University of
Bergen, Bergen, Norway; VIMS—Virginia Institute of Marine
Sciences, Gloucester Point, USA; USNM—United States
National Museum of Natural History, Washington, United States;
* data taken from published sources (Bigelow and Schroeder,
1927, 1950, 1953), na—not available.
480
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ORLOV, COTTON
Table 2.
Variations of morphometric and meristic characters in Jensen’s skate
Amblyraja jenseni
Character Both sexes (19) Females (11) Males (8)
min max mean
SE
min max mean
SE
min max mean
SE
TL
, mm 223.0 1113.0 671.3 56.9 369.0 1065.0 660.6 54.0 223.0 1113.0 686.0 118.3
Morphometrics, %
TL
1
67.2
81.3 73.1 0.8 67.2 81.3 72.8 1.2 70.2 77.2 73.6 0.9
2 51.9 60.0 56.6 0.5 54.7 60.0 57.0 0.5 51.9 59.5 56.1 0.9
310.3
17.0
15.1 0.3 14.0 17.0 15.6 0.3 10.3 15.8 14.4 0.6
4 11.6 16.9 14.1 0.3 11.6 16.3 13.9 0.5 12.6 16.9 14.4 0.5
57.4
12.7
10.3 0.4 7.5 12.7 10.5 0.6 7.4 11.8 10.2 0.6
6 1.8 5.8 3.8 0.3 2.5 5.8 4.1 0.3 1.8 5.4 3.5 0.5
7
6.0
11.1 7.2 0.3 6.0 7.9 7.1 0.2 6.2 11.1 7.4 0.6
82.3
3.9
3.2 0.1 2.3 3.9 3.2 0.1 2.5 3.8 3.2 0.1
9
10.1
15.8 11.3 0.3 10.1 12.0 11.1 0.2 10.2 15.8 11.5 0.6
10 4.8 7.2 6.1 0.2 5.3 6.9 6.2 0.2 4.8 7.2 6.1 0.3
11 1.5 4.9 2.1 0.2 1.5 4.9 2.1 0.3 1.7 2.3 2.0 0.1
12 3.9 5.4 4.5 0.1 4.3 5.4 4.6 0.1 3.9 5.0 4.4 0.1
13 1.3 3.3 1.9 0.1 1.3 3.3 1.9 0.2 1.5 2.7 2.0 0.1
14 3.3 5.8 4.7 0.1 4.1 5.8 4.9 0.2 3.3 5.2 4.6 0.2
15 0.0 3.4 0.6 0.2 0.0 3.4 0.8 0.3 0.0 1.1 0.4 0.2
16
2.1 4.1
2.8 0.2 2.1 4.1 3.0 0.2 2.2 4.0 2.7 0.2
17
1.9
5.5 3.2 0.3 1.9 5.3 3.2 0.3 2.2 5.5 3.1 0.4
18
1.9 3.0
2.3 0.1 1.9 3.0 2.4 0.1 2.0 2.5 2.2 0.1
19
2.6
3.6 3.0 0.1 2.6 3.6 3.1 0.1 2.8 3.6 3.0 0.1
20 0.8 1.3 1.0 0.0 0.9 1.2 1.0 0.0 0.8 1.3 1.0 0.1
21 0.9 1.6 1.3 0.0 0.9 1.6 1.3 0.1 1.1 1.6 1.3 0.1
22 30.5 39.6 35.4 0.8 31.6 38.8 36.1 0.9 30.5 39.6 34.7 1.3
23 26.4 34.5 30.5 0.6 26.4 33.3 30.4 0.7 27.8 34.5 30.7 0.9
24 11.9 15.9 13.1 0.3 11.9 15.9 13.2 0.4 12.3 14.5 13.0 0.3
25
11.1 14.0
12.5 0.2 11.7 14.0 12.6 0.3 11.1 13.7 12.4 0.3
26
3.4
6.7 5.3 0.2 3.7 5.9 5.2 0.2 3.4 6.7 5.4 0.4
27 13.3 15.3 14.3 0.4 13.3 15.1 13.9 0.4 14.6 15.3 15.0 0.4
28 1.5
4.2
2.4 0.2 1.5 3.2 2.3 0.2 1.9 4.2 2.6 0.3
29
7.8 12.1
9.6 0.3 8.2 10.1 9.5 0.2 7.8 12.1 9.8 0.6
30 1.3 1.7 1.4 0.0 1.3 1.4 1.3 0.0 1.3 1.7 1.5 0.1
31 1.3 2.0 1.6 0.0 1.3 1.6 1.5 0.0 1.6 2.0 1.7 0.1
32 0.9 1.5 1.2 0.0 0.9 1.4 1.1 0.0 0.9 1.5 1.2 0.1
33 16.3 24.8 20.4 0.4 17.5 22.1 20.3 0.4 16.3 24.8 20.6 1.0
34 10.5 18.1 15.0 0.5 13.1 18.1 15.6 0.5 10.5 16.4 14.1 0.9
35 10.7 15.2 12.7 0.3 11.5 15.1 12.6 0.3 10.7 15.2 12.9 0.6
36 16.3 20.6 19.0 0.3 16.3 20.2 19.0 0.4 16.7 20.6 19.1 0.6
37 7.6
23.2
15.6 2.8 7.6 23.2 15.6 2.8
38
51.1
60.9 55.5 0.7 52.8 58.7 55.6 0.7 51.1 60.9 55.4 1.3
39 31.4 42.6 38.1 0.7 33.6 42.6 38.5 0.9 31.4 40.5 37.5 1.3
40
17.1
34.8 31.1 0.9 30.4 34.8 32.2 0.4 17.1 33.6 29.5 1.9
JOURNAL OF ICHTHYOLOGY
Vol . 55
No. 4
2015
NEW DATA ON THE RARE DEEPSEA SKATE
Amblyraja jenseni
481
present study increased the sample size available for
examination (Table 2) and demonstrated that the fol
lowing morphological and meristic characters can
vary over a wider range than was previously reported
(Orlov et al., 2006): disc width, preorbital snout
length, prenasal snout length, interorbital width, spir
acle length, interspiracular width,
C
base length, post
dorsal tail length, width and height of the tail at the
V
tips, internasal width, nasal curtain length, width of
each lobe of the nasal curtain, the distance between
nasal curtain lobes, clasper length, distance between
snout tip and the center of the anus, distance between
the center of the anus and the
DI
origin, distance
between the center of the anus and the tip of the tail,
as well as the number of scapular thorns. These new
data are important to understand the extent of
intraspecific variation of morphological characters
and can be used for the development of dichotomous
keys for species identification.
Ontogenetic Changes
in External Morphological Characters
Ontogenetic differences in morphometric and
meristic characters in the Jensen’s skate were previ
ously undocumented. We examined individuals rang
ing in size from 223 to 1113 mm
TL
, i.e. including
small immature and large mature skates (Table 3). Our
analysis showed that as the Jensen’s skate increases in
total length, the following characters exhibit relative
increases in size: disc length,
DII
height, mouth width,
clasper length, and the distance between the snout tip
and the center of the anus. Contrastingly, an increase
in body length was accompanied by a relative decrease
Table 2.
(Contd.)
Character Both sexes (19) Females (11) Males (8)
min max mean
SE
min max mean
SE
min max mean
SE
TL
, mm 223.0 1113.0 671.3 56.9 369.0 1065.0 660.6 54.0 223.0 1113.0 686.0 118.3
41 30.2 39.7 36.2 0.5 35.4 39.7 36.9 0.4 30.2 38.5 35.2 1.0
42
32.4 48.5
43.5 0.9 32.4 47.4 43.4 1.3 38.1 48.5 43.6 1.1
43 85.0 103.0 92.4 1.7 85.0 102.0 90.9 2.1 87.0 103.0 94.2 2.7
Meristics
44 1.0 3.0 1.4 0.2 1.0 2.0 1.3 0.2 1.0 3.0 1.6 0.3
45 1.0 2.0 1.4 0.1 1.0 2.0 1.4 0.2 1.0 2.0 1.4 0.2
46 1.0 2.0 1.3 0.1 1.0 2.0 1.3 0.2 1.0 2.0 1.1 0.1
47
0.0 5.0
3.1 0.4 0.0 5.0 2.9 0.6 3.0 5.0 3.3 0.3
48 1.0 2.0 1.8 0.1 1.0 2.0 1.8 0.1 1.0 2.0 1.9 0.1
49 1.0 1.0 1.0 0.0 1.0 1.0 1.0 0.0 1.0 1.0 1.0 0.0
50 20.0 31.0 25.6 0.8 23.0 28.0 25.8 0.7 20.0 31.0 25.3 1.5
51 0.0 1.0 0.3 0.1 0.0 1.0 0.2 0.1 0.0 1.0 0.3 0.2
52 52.0 66.0 59.9 1.4 52.0 63.0 58.5 2.5 59.0 64.0 61.3 1.1
53 52.0 66.0 57.5 1.5 54.0 61.0 57.3 1.9 52.0 64.0 57.8 2.5
TL
—total length,
SE
—standard error, characters that varied in wider limits as compared to published data by Orlov et al. (2006) are in
bold, number of specimens examined is shown in parentheses. Morphometrics: 1—disc width, 2—disc length, 3—preorbital snout
length, 4—preoral snout length, 5—prenasal snout length, 6—horizontal orbit diameter, 7—interorbital width, 8—spiracle length,
9—interspiracular width, 10—orbit + spiracle length, 11—
DI
height, 12—
DI
base length, 13—
DII
height, 14—
DII
base length, 15—
interdorsal space, 16—
C
base length, 17—postdorsal tail length, 18—tail height at
V
tips, 19—tail width at
V
tips, 20—tail height at
DI
origin, 21—tail width at
DI
origin, 22—lateral fold length, 23—head length, 24—mouth width, 25—internasal width, 26—nasal cur
tain length, 27—nasal curtain width, 28—width of each lobe of nasal curtain, 29—distance between nasal curtain lobes, 30—1st gill
slit length, 31—3rd gill slit length, 32—5th gill slit length, 33—distance between 1st gill slits, 34—distance between 5th gill slits, 35—
length of
V
anterior lobe, 36—length of
V
posterior lobe, 37—clasper length, postanus (inner clasper length), 38—distance between
snout tip and center of anus, 39—distance between snout tip and maximum disc width, 40—distance between center of anus and
DI
origin, 41—distance between center of anus and
DII
origin, 42—distance between center of anus and tip of tail, 43—snout angle.
Meristics: 44—number of preorbital thorns, 45—number of postorbital thorns, 46—number of interspiracular thorns, 47—number of
scapular thorns, 48—number of nuchal thorns, 49—number of interscapular thorns, 50—number of median thorns, 51—number of
middorsal thorns, 52—number of tooth rows in upper jaw, 53—number of tooth rows in lower jaw.
482
JOURNAL OF ICHTHYOLOGY
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2015
ORLOV, COTTON
Table 3.
Differences of morphometric and meristic characters in Jensen’s skate
Amblyraja jenseni
of different size classes
Character
Total length, mm (number of specimens)
TL
<500 (4)
TL
500–700 (9)
TL
>700 (6)
min max mean
SE
min max mean
SE
min max mean
SE
TL
, mm 223.0 473.0 333.8 55.5 541.0 696.0 631.0 20.3 833.0 1113.0 956.8 52.1
Morphometrics, %
TL
1 70.2 75.5 72.9 1.2 67.2 81.3 72.3 1.4 71.0 77.2 74.5 1.1
2 53.7 56.7 55.5 0.6 51.9 60.0 56.7 0.8 55.7 59.5 57.1 0.6
3 14.4 16.6 15.5 0.5 10.3 17.0 15.0 0.7 14.0 15.6 14.9 0.3
4 13.7 16.9 15.1 0.7 11.6 16.3 14.2 0.6 12.5 14.2 13.2 0.3
5 10.5 11.1 10.8 0.2 8.1 12.7 10.5 0.6 7.4 11.8 9.7 0.9
6 2.9 4.7 3.8 0.4 2.2 5.8 4.2 0.3 1.8 5.4 3.2 0.7
7 6.2 7.5 7.1 0.3 6.2 11.1 7.7 0.5 6.0 7.7 6.7 0.3
8 2.5 3.8 3.1 0.3 2.3 3.9 3.1 0.2 3.2 3.6 3.4 0.1
9 10.6 11.6 11.0 0.2 10.1 15.8 11.7 0.5 10.2 11.2 10.8 0.2
10 5.7 7.2 6.3 0.5 5.2 6.9 6.3 0.2 4.8 6.9 5.9 0.4
11 1.6 2.1 1.8 0.1 1.5 2.1 1.8 0.1 1.9 4.9 2.7 0.5
12 4.5 5.0 4.8 0.1 3.9 5.4 4.5 0.1 4.1 4.6 4.3 0.1
13 1.5 1.9 1.6 0.1 1.3 2.0 1.7 0.1 1.9 3.3 2.4 0.2
14 3.3 5.3 4.6 0.5 4.1 5.8 4.9 0.2 4.1 5.2 4.7 0.2
15 0.6 1.1 0.9 0.1 0.0 1.0 0.5 0.1 0.0 3.4 0.7 0.6
16 2.3 4.0 3.3 0.5 2.1 4.1 2.9 0.3 2.2 2.9 2.5 0.1
17 2.3 5.5 4.1 0.7 1.9 3.9 2.8 0.2 2.2 5.3 3.1 0.5
18 2.4 2.5 2.5 0.0 1.9 3.0 2.4 0.1 2.0 2.4 2.1 0.1
19 3.0 3.6 3.2 0.2 2.6 3.6 3.1 0.1 2.8 2.9 2.8 0.0
20 1.1 1.3 1.2 0.0 0.8 1.2 1.0 0.0 0.9 1.0 0.9 0.0
21 1.3 1.6 1.5 0.1 0.9 1.6 1.2 0.1 1.1 1.4 1.3 0.0
22 37.0 39.6 38.5 0.8 30.5 37.7 35.5 1.1 30.5 37.2 33.5 1.2
23 28.5 34.5 30.6 1.9 29.1 33.3 31.3 0.5 26.4 32.5 29.4 1.2
24 12.3 12.5 12.4 0.1 11.9 15.1 12.8 0.4 12.5 15.9 14.2 0.5
25 12.1 13.7 12.8 0.3 11.7 14.0 12.7 0.3 11.1 13.1 12.0 0.3
26 5.6 6.7 6.0 0.3 3.7 5.9 5.1 0.2 3.4 6.2 5.1 0.5
27 na na na na 13.3 15.1 13.9 0.4 14.6 15.3 15.0 0.4
28 1.9 2.8 2.4 0.3 1.5 4.2 2.5 0.3 1.9 2.7 2.3 0.1
29 8.1 9.5 8.6 0.5 9.3 12.1 9.9 0.3 7.8 11.1 9.8 0.6
30 1.3 1.7 1.5 0.1 1.3 1.4 1.3 0.0 1.3 1.7 1.5 0.1
31 1.5 1.7 1.6 0.1 1.3 1.7 1.5 0.0 1.6 2.0 1.7 0.1
32 1.0 1.4 1.2 0.1 0.9 1.2 1.1 0.0 1.2 1.5 1.3 0.1
33 18.6 20.2 19.2 0.5 19.7 24.8 21.3 0.5 16.3 21.7 19.7 0.9
34 14.0 14.7 14.3 0.2 11.2 18.1 15.7 0.6 10.5 16.4 14.2 0.9
35 10.7 15.2 13.3 1.1 11.5 13.4 12.3 0.2 11.5 14.8 13.0 0.6
36 17.3 20.2 19.2 0.9 16.3 20.2 18.5 0.5 19.2 20.6 19.8 0.3
37 7.6 7.6 7.6 0.0 8.1 8.1 8.1 0.0 19.9 23.2 21.5 0.7
38 51.1 55.6 52.8 1.0 51.9 58.3 55.2 0.7 57.0 60.9 58.4 0.7
39 38.5 39.7 39.0 0.4 34.1 42.6 38.6 1.0 31.4 40.5 36.6 1.8
40 31.3 33.6 32.7 0.5 17.1 34.8 30.4 1.7 27.3 33.4 31.1 0.9
JOURNAL OF ICHTHYOLOGY
Vol . 55
No. 4
2015
NEW DATA ON THE RARE DEEPSEA SKATE
Amblyraja jenseni
483
in the following characters: preoral, preorbital, and
prenasal snout length,
DI
base length,
C
base length,
tail height and width at the
V
origin, tail height at the
DI
origin, lateral fold length, internasal width, dis
tance from the snout tip to the maximum disc width,
the distance from the center of the anus to the
DII
.
It has been suggested that meristic characters in
fish are not susceptible to ontogenetic variation
(Kirpichnikov, 1987). Our data show that the snout
angle, the number of pre and postorbital thorns, and
the number of tooth rows in the upper jaw decrease
with growth. Ontogenetic changes in some meristic
characters have also been documented for another
deepwater batoid, the MidAtlantic skate,
Rajella
kukujevi
(Orlov, 2014).
Our results can also convey information about mat
uration in male Jensen’s skates. The relative length of
the claspers increases from 7.6% in the smallest speci
mens to 23.2% in the largest. Previous studies have
shown that the majority of male skates reach sexual
maturity when their clasper length is about 20% of the
total length (Orlov, 2006). Based on our data, we can
estimate that male Jensen’s skates in the waters of the
NEA and MAR become sexually mature at a total
length of about 83 cm (we did not examine any adult
males from the NWA). Until now, the length at matu
rity for this species was unknown (Ebert and Steh
mann, 2013).
Regional Differences in the External Morphology
Differences in external morphological features
between specimens from the MAR and those from the
NWA suggest that these differences are due to long
term geographic isolation (Orlov et al., 2006). We
decided to test this hypothesis on a larger number of
specimens (9 from the NWA, 4 from the MAR, and 6
from the NEA). Since the size ranges of specimens in
the compared samples were significantly different
(mean sizes = 69.4, 95.1 and 50.8 cm, respectively),
the observed differences in external morphological
characters may be partly due to differences in size
(Table 4), and/or the small sample sizes of specimens
examined. Nevertheless, we can conclude that some
external morphological characteristics of the Jensen’s
skate in different regions vary considerably. In speci
mens from the MAR compared with those from the
NEA and NWA, we found a noticeably smaller relative
value for a number of characters: prenasal snout
length, the horizontal orbit diameter, the length of the
orbit + spiracle, interdorsal space, tail height at the
DI
origin, lateral fold length, head length, internasal
width, the distance between the 5th gill slits, the dis
tance between the snout tip and the maximum disc
width, distance between the center of the anus and the
DII
origin, the snout angle, and the number of mid
dorsal thorns. Likewise, specimens from the MAR had
a taller
DII
. It was notable that specimens from the
MAR had a distinctive lack of interdorsal space and
middorsal thorns. Skates from the NEA exhibited the
Table 3.
(Contd.)
Character
Total length, mm (number of specimens)
TL
<500 (4)
TL
500–700 (9)
TL
>700 (6)
min max mean
SE
min max mean
SE
min max mean
SE
TL
, mm 223.0 473.0 333.8 55.5 541.0 696.0 631.0 20.3 833.0 1113.0 956.8 52.1
41 36.6 38.5 37.6 0.6 30.2 39.7 36.0 1.0 34.3 37.4 35.9 0.5
42 44.4 48.5 46.7 0.9 32.4 47.2 42.2 1.7 42.5 44.1 43.1 0.3
43 91.0 103.0 99.3 2.8 86.0 102.0 92.8 1.6 85.0 101.0 91.4 2.9
Meristics
44 2.0 2.0 2.0 0.0 1.0 3.0 1.5 0.3 1.0 1.0 1.0 0.0
45 2.0 2.0 2.0 0.0 1.0 2.0 1.5 0.2 1.0 1.0 1.0 0.0
46 1.0 2.0 1.3 0.3 1.0 2.0 1.4 0.2 1.0 1.0 1.0 0.0
47 3.0 5.0 3.7 0.7 0.0 5.0 2.9 0.7 3.0 3.0 3.0 0.0
48 1.0 2.0 1.7 0.3 1.0 2.0 1.9 0.1 1.0 2.0 1.8 0.2
49 1.0 1.0 1.0 0.0 1.0 1.0 1.0 0.0 1.0 1.0 1.0 0.0
50 20.0 23.0 21.7 0.9 23.0 31.0 26.5 0.9 23.0 30.0 26.4 1.2
51 0.0 1.0 0.7 0.3 0.0 1.0 0.1 0.1 0.0 1.0 0.2 0.2
52 64.0 64.0 64.0 52.0 63.0 59.8 2.6 57.0 60.0 58.7 0.9
53 56.0 56.0 56.0 54.0 64.0 59.8 2.1 52.0 59.0 55.0 2.1
Definitions of characters and abbreviations are the same as in Table 2 (na—not available).
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Table 4.
Differences of morphometric and meristic characters in Jensen’s skate
Amblyraja jenseni
in different areas
Character
Area (number of specimens)
MAR (4) NEA (6) NWA (9)
min max mean
SE
min max mean
SE
min max mean
SE
TL
, mm 696.0 1113.0 977.3 95.1 542.0 845.0 689.8 50.8 223.0 850.0 523.0 69.4
Morphometrics, %
TL
1 71.0 75.2 73.6 0.9 67.2 77.2 71.6 1.4 69.5 81.3 73.9 1.3
2 51.9 56.8 55.1 1.1 54.7 59.5 57.5 0.7 53.7 60.0 56.6 0.6
3 10.3 15.6 13.7 1.2 14.4 17.0 15.8 0.4 14.0 16.6 15.2 0.3
4 12.6 15.4 13.5 0.7 12.8 15.3 14.2 0.4 11.6 16.9 14.3 0.6
5 7.4 11.1 8.5 0.9 10.0 12.7 11.3 0.5 10.1 11.1 10.6 0.2
6 1.8 2.5 2.1 0.1 3.7 5.4 4.2 0.3 2.9 5.8 4.4 0.3
7 6.2 11.1 7.6 1.2 7.0 7.9 7.5 0.2 6.0 7.8 6.9 0.2
8 2.9 3.4 3.2 0.1 3.0 3.9 3.5 0.1 2.3 3.8 3.0 0.2
9 10.2 15.8 11.9 1.3 10.1 11.8 11.1 0.2 10.6 12.0 11.2 0.1
10 4.8 5.8 5.3 0.2 5.6 6.9 6.4 0.2 5.7 7.2 6.5 0.2
11 1.7 2.7 2.2 0.2 1.5 2.1 1.9 0.1 1.5 4.9 2.2 0.4
12 3.9 4.6 4.3 0.2 4.1 4.8 4.3 0.1 4.3 5.4 4.8 0.1
13 1.8 2.7 2.3 0.2 1.5 2.1 1.8 0.1 1.3 3.3 1.8 0.2
14 4.2 5.1 4.6 0.2 4.1 5.3 4.7 0.2 3.3 5.8 4.8 0.3
15 0.0 0.0 0.0 0.0 0.0 1.0 0.5 0.2 0.3 3.4 1.0 0.3
16 2.2 2.7 2.5 0.1 2.1 4.1 2.8 0.3 2.3 4.0 3.2 0.3
17 2.2 2.9 2.6 0.2 1.9 3.9 2.7 0.3 2.3 5.5 3.8 0.5
18 2.0 2.4 2.2 0.1 1.9 3.0 2.2 0.2 2.4 2.7 2.5 0.0
19 2.8 3.1 2.9 0.1 2.6 3.6 3.0 0.2 2.7 3.6 3.2 0.2
20 0.8 1.0 0.9 0.0 0.9 1.0 1.0 0.0 0.9 1.3 1.1 0.1
21 1.1 1.3 1.2 0.0 1.1 1.4 1.3 0.1 0.9 1.6 1.3 0.1
22 30.5 33.3 31.5 0.7 33.4 37.7 35.8 0.7 37.0 39.6 38.1 0.5
23 26.4 31.2 28.5 1.0 29.1 32.5 31.0 0.5 28.5 34.5 31.5 1.0
24 12.9 14.7 13.9 0.4 11.9 15.1 13.1 0.5 11.9 15.9 12.8 0.4
25 11.1 12.2 11.8 0.2 11.7 14.0 12.8 0.4 12.0 13.7 12.7 0.2
26 3.4 5.9 4.9 0.5 4.7 6.2 5.4 0.2 3.7 6.7 5.4 0.4
27 na na na 13.3 15.3 14.3 0.4 na na na na
28 1.9 4.2 2.7 0.5 2.1 3.2 2.6 0.1 1.5 2.8 2.1 0.2
29 7.8 12.1 10.3 0.9 9.3 10.3 9.8 0.2 8.1 10.1 9.1 0.3
30 1.3 1.7 1.4 0.1 1.3 1.6 1.4 0.0 1.3 1.7 1.4 0.1
31 1.6 2.0 1.8 0.1 1.4 1.8 1.6 0.1 1.3 1.7 1.5 0.1
32 0.9 1.5 1.2 0.1 1.1 1.3 1.2 0.0 0.9 1.4 1.1 0.1
33 16.3 24.8 20.1 2.0 19.7 21.7 20.7 0.3 18.6 22.1 20.4 0.4
34 10.5 16.4 12.8 1.3 15.4 15.9 15.6 0.1 13.8 18.1 15.6 0.6
35 11.5 12.8 12.0 0.3 12.1 14.8 13.2 0.4 10.7 15.2 12.7 0.6
36 16.7 20.6 19.2 0.9 16.3 20.2 18.8 0.6 17.3 20.2 19.1 0.5
37 8.1 23.2 17.4 4.7 19.9 21.9 20.9 1.0 7.6 7.6 7.6 0.0
38 51.9 60.9 57.4 1.9 55.2 58.3 56.6 0.5 51.1 57.8 53.8 0.8
39 31.4 38.6 34.4 1.5 35.6 41.7 38.9 0.9 38.5 42.6 39.7 0.6
40 17.1 33.4 27.8 3.7 27.3 32.8 31.2 0.8 30.4 34.8 32.5 0.4
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485
lowest number of scapular thorns and the highest spir
acle length. For individuals from the NWA we found
the maximum ranges in the following characters:
DI
base length, postdorsal tail length, tail height at the
V
tips, lateral fold length, distance between the center of
the anus and the
DI
and
DII
origins, distance between
the center of the anus and the tip of the tail, and the
number of postorbital, interspiracular, and scapular
thorns. Likewise we found the minimum ranges in the
following characters for skates from the NWA: width
of each lobe of the nasal curtain, distance between
nasal curtain lobes, clasper length (due to the absence
of mature males in this region), distance between the
snout tip and the center of the anus, and the number of
median thorns. Thus, we identified regional differ
ences in external morphological characters in Jensen’s
skate likely due to longterm geographic isolation of
populations in waters of the NWA, NEA and MAR.
This finding supports the hypothesis that
Amblyraja
species colonized the North Atlantic from Arctic
waters and populations then spread along three pri
mary corridors, the American and European coasts
and the MAR (Dolganov, 2002; Orlov et al., 2006).
Sexual Dimorphism
in External Morphological Characters
A previous study of sexual dimorphism in external
morphological characters of the Jensen’s skate (Orlov
et al., 2010; Orlov and Cotton, 2011) was based on
13 specimens (7 females and 6 males). In that study,
the following characters were found to be sexually
dimorphic: disc length,
DII
base length, tail height at
the
V
tips, nasal curtain length, 1st and 3rd gill slit
lengths, distance between the 5th gill slits, and the
number of nuchal and middorsal thorns. The results of
the present study (Table 1) performed on a larger sam
ple size (19 specimens), showed that males and
females differ in seven morphological characters: pre
oral snout length, nasal curtain width, 1st and 3rd gill
slit lengths, distance between 5th gill slits, and the dis
tance between the center of the anus and the
DI
and
DII
origins. It is possible that in the future, with the
accumulation of more specimens, these results may be
further revised.
Coloration
Published information on the coloration of
Jensen’s skate is fairly sparse and sometimes contra
dictory. Originally it was reported that the dorsal sur
face in fixed specimens was a monochromatic light
brown with grayish or brown shades and darker edges
of the wings (Bigelow and Schroeder, 1927, 1950,
1953; Leim and Scott, 1966). Bigelow and Schroeder
(1927) described the ventral surface as somewhat
darker than the dorsal, with the edges of the wings dark
brown and large dark areas in the middle of the body
and on the ventral fins. Later, they (Bigelow and
Schroeder, 1950) described the color of the ventral
Table 4.
(Contd.)
Character
Area (number of specimens)
MAR (4) NEA (6) NWA (9)
min max mean
SE
min max mean
SE
min max mean
SE
TL
, mm 696.0 1113.0 977.3 95.1 542.0 845.0 689.8 50.8 223.0 850.0 523.0 69.4
41 30.2 37.4 34.2 1.5 35.7 37.3 36.3 0.2 35.4 39.7 37.3 0.5
42 38.1 44.1 41.8 1.3 32.4 44.8 41.8 1.9 42.7 48.5 45.6 0.7
43 85.0 90.0 87.8 1.1 86.0 102.0 94.3 2.6 90.0 103.0 96.5 1.8
Meristics
44 1.0 3.0 1.5 0.5 1.0 1.0 1.0 0.0 1.0 2.0 1.8 0.2
45 1.0 2.0 1.3 0.3 1.0 1.0 1.0 0.0 2.0 2.0 2.0 0.0
46 1.0 1.0 1.0 0.0 1.0 1.0 1.0 0.0 1.0 2.0 1.7 0.2
47 3.0 3.0 3.0 0.0 0.0 3.0 2.0 0.6 3.0 5.0 4.2 0.4
48 2.0 2.0 2.0 0.0 1.0 2.0 1.8 0.2 1.0 2.0 1.7 0.2
49 1.0 1.0 1.0 0.0 1.0 1.0 1.0 0.0 1.0 1.0 1.0 0.0
50 23.0 31.0 27.0 1.7 24.0 30.0 27.0 0.9 20.0 26.0 23.2 0.9
51 0.0 0.0 0.0 0.0 0.0 1.0 0.3 0.2 0.0 1.0 0.3 0.2
52 57.0 62.0 59.5 1.0 na na na na 52.0 64.0 60.3 2.8
53 52.0 64.0 57.3 2.7 na na na na 54.0 61.0 57.8 1.7
Definitions of characters and abbreviations are the same as in Table 2, those of the areas as in Table 1 (na—not available).
486
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surface as a brownishgray with dark patterns around
the anus and on the inner surface of the ventral fins. In
later publications, it was described yet again differently
as a brownishgray, grayishwhite, pure white (Bigelow
and Schroeder, 1953) or from white and yellowish to
gray (Leim and Scott, 1966).
The first information about ontogenetic changes in
coloration of Jensen’s skate was published in the mid
dle of the last century (Bigelow and Schroeder, 1953),
noting that in young animals the area around the anus
and the inner surface of the ventral fins was dark but
this color pattern spread with age across the abdomen
of large skates, which also have brown outer edges of
the wings. Sulak et al. (2009) stated that the ventral
surface of juveniles was predominantly white, while in
adults it was mostly dark, with the ventral surface
showing almost symmetrical patterns from gray to
black on a white background. Other authors have
noted that color variation with age is not only found on
the ventral surface, but also on the dorsal surface as
well. Séret (2010) indicated that the dark spots on the
dorsal surface disappear with age, but the predominant
coloration of the ventral surface (even in young skates)
was dark. Summarizing the available information
about the color of Jensen’s skate, Ebert and Stehmann
(2013) noted characteristic white areas around the
mouth, the nostrils, and the middle of the body and
Seret (2010) further noted the presence of white areas
around the gill slits and cloaca.
Incorporation of our new data facilitated a more
detailed analysis of the coloration of Jensen’s skate
and revealed how coloration varies with ontogeny as
well as with geographical origin (Table 5). The most
characteristic markings of the dorsal surface are the
presence of a dark edge of the wings (70.6% of individ
uals), dark spots on the disc (73.3%) and alternating
light and dark bands on the tail (68.8%). These mark
ings are most clearly expressed in the skates collected
from the MAR (Fig. 1), although in preserved speci
mens the markings may fade and be overlooked as
a result of fixation. The presence of dark spots on the
dorsal surface of the disc and the banding on the tail is
indicated in a number of publications (Sulak et al.,
2009; Séret, 2010), but our data do not support the
observations of Séret (2010) that the dark spots on the
disc disappear with age (Fig. 1b, Table 5).
Despite the high variation in ventral surface color
ation of the Jensen’s skate, there are two predominant
types: “light” and “dark” with corresponding dark or
light markings, respectively. The first type occurs in
about a third of specimens observed. These specimens
exhibit a light ventral background marked with dark
areas on the edges of the wings, in the posterior lobes
of the
V
, the sides of the abdomen, and in the central
part of the
V
and the tail (Fig. 2). Such coloration pat
(a) (b)
(c) (d)
Fig. 1.
Specimens of Jensen’s skate,
Amblyraja jenseni
, from the MidAtlantic Ridge: ZMUB 19529, male,
TL
696 mm (a, b);
ZMUB 19462, female,
TL
1065 mm (c, d).
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487
(a) (b)
(c) (d)
Fig. 2.
Specimens of Jensen’s skate,
Amblyraja jenseni
, exhibiting the “light” coloration: MCZ 138020A, female,
TL
369 mm,
NWA (a, b); MRI 803, female,
TL
629 mm, NEA (c, d).
terns are observed among the young and mature skates
of the NEA and NWA, but are not observed in speci
mens from the MAR. Most Jensen’s skates exhibit the
dark coloration on the ventral surface (68.4%). This
color morph is characterized by the presence of light
areas on the snout, around the mouth and nostrils (in
many specimens the light colored patch extends con
tinuously from the tip of the snout to the end of the
lower lip), around the gill slits, behind the gills in the
center of the abdomen, on the anterior lobe of the
V
and between the gills (Fig. 3), as well as on the claspers
(except for specimens from MAR).
Our data do not support previous findings that col
oration in Jensen’s skate varies with age (Bigelow and
Schroeder, 1953; Sulak et al., 2009; Séret, 2010). Dark
spots on the dorsal surface of the disc and the banded
tail can be present or absent, regardless of the size of
the skate. The predominant dark or lightcolored ven
tral surface also does not depend on the size of the
skate.
Our results also provide insight into the geographi
cal variation in coloration of the Jensen’s skate. The
“light” color morph is found in the NEA and NWA,
but is not observed on the MAR. In the NEA, light
coloring is noted in about half of the specimens,
whereas in the NWA it is much rarer. Skates from the
MAR exhibit a distinctive dark coloration, with the
ventral surface bearing a few light patches which are
restricted to the snout, around the nostrils, mouth and
gill slits, as well as a small triangle in the anterior abdo
men (in some specimens these patches on the snout
and around the gill openings are lacking). Ventral col
oration patterns in skates from the NEA and NWA
varies much more widely, but some patterns are com
mon among specimens. The “light” color morph is
us ually mar ked by dar k area s on the edges o f the wings ,
in the posterior lobes and central part of the
V
, and on
the sides of the abdomen and tail. The “dark” color
morph exhibits light areas on the snout, around the
nostrils, mouth and gill slits, between the gill slits, on
the ventral surface of the
V
and claspers (the latter fea
ture is not characteristic of skates from the MAR).
Underwater photographs (Fig. 4) indicate that the
Jensen’s skate
in situ
(at least in the waters of the
MAR) is a chocolatebrown color with contrasting
and unevenly scattered dark spots that become paler
when the skate is captured and taken out of water, and
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(a) (b)
(c) (d)
Fig. 3.
Specimens of Jensen’s skate,
Amblyraja jenseni
, exhibiting the “dark” coloration: MCZ 155628, female,
TL
675 mm,
NWA (a, b); MRI 851, male,
TL
845 mm, NEA (c, d).
after long storage in fixative may disappear. We also
noted the presence of a light area on the snout and two
symmetrical light strips along the body in mature
males photographed at depth (Fig. 4b), which were
not observed in freshly caught or fixed specimens.
Geographic and Vertical Distribution
The holotype of Jensen’s skate was caught off the
North American coast in the waters of New England
and Nova Scotia (Bigelow and Schroeder, 1950). Sub
sequent records were also reported from the waters of
the NWA (Bigelow and Schroeder, 1953; Tempelman,
1965; Leim and Scott, 1966; Moore et al., 2000;
Alpoim et al., 2002; Coad and Reist, 2004; Sulak et al.,
2009; Halliday et al., 2012; Kenchington et al., 2013,
Vázquez et al., 2013). The northern extent of the range
was reported to be the waters of Greenland (Karrer,
1976; Nielsen and Bertelsen, 1992; Møller et al.,
2010) to 64
°
47
N, and the southern extent of the
range is off the coast of Maryland to 38
°
47
N (Orlov
et al., 2006). New data suggest that the Jensen’s skate
can penetrate even further north, i.e. in the Davis
Strait, up to 67
°
51
N and further south to the waters
of North Carolina to 35
°
23
N (Fig. 5). In the NEA
this species has been reported from only a few speci
mens taken west of the British Isles (Gordon and Dun
can, 1987, 1989; Quero et al., 2000; George and Zid
owitz, 2006; Neat et al., 2008; Johnston et al., 2010;
Séret, 2010; Silva et al., 2012). Our data suggest that
this species in the NEA is not rare and is encountered
regularly during deepsea research. In the area along
the MAR, several specimens of Jensen’s skate were
collected by trawls and longlines (Orlov et al., 2006),
as well as photographed at baited landers, including in
the CharlieGibbs Fracture Zone (Cousins et al.,
2013).
Until now, published information on the vertical
distribution of Jensen’s skate was limited to the mini
mum and maximum depths of capture. Our data allow
for a more detailed analysis of the specific bathymetric
distribution of this species (Fig. 6). Despite the fairly
wide range of capture depths from 167 to 2548 m,
approximately half of all specimens were captured in
the ranges of 1400–1600 m (15.1% of all individuals)
and 1800–2200 m (33.0%). This deep distribution was
the basis of the designation of the “Least Concern”
category assessed by the IUCN Red List because fish
ing pressure at those depths is minimal and thus does
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NEW DATA ON THE RARE DEEPSEA SKATE
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489
Fig. 4.
Specimens of two Jensen’s skates,
Amblyraja jenseni
photographed by the ROBIO lander on the MidAtlantic Ridge
(photo credit: Nicola Cousins, Oceanic Laboratory, University of Aberdeen, Scotland).
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80°
60°
50°
40°
10°20°40°60°80° 50°70° 30°
70°
Fig. 5.
Collection locations of Jensen’s skate,
Amblyraja jenseni
, in the North Atlantic: (
)—holotype, (+)—published data,
(
)—new records.
not significantly impact populations of Jensen’s skate
(Kulka et al., 2008; Goodwin, 2012).
Previously, we (Orlov et al., 2006) showed that the
vertical distribution of the Jensen’s skate varies region
ally, with NEA specimens being the deepest dwelling
(average depth of 2052 m), the NWA specimens being
the shallowest dwelling (average 846 m) and specimens
from the MAR occupying intermediate depths (aver
age 1918 m). With the new records considered in the
present study from the NEA and NWA, as well as
observations from a baited lander on the MAR, the
previous characterization of vertical distribution has
changed somewhat (Fig. 7). The greatest mean depth
of occurrence is from the waters of the MAR (average
depth of 1996 m), specimens from the NEA occupy a
slightly shallower mean depth (average 1650 m), and
the average depth for specimens captured in the NWA
remained almost the same (864 m).
16
14
12
10
8
6
4
2
0
2000–2200
18002000
16001800
1000–1200
600–700
<300
9001000
300400
1400–1600
Depth, m
Number of specimens
18
20
>2200
12001400
700–800
800–900
400500
500–600
Fig. 6.
Depths of capture for individual Jensen’s skates,
Amblyraja jenseni
, from the North Atlantic.
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491
1600
1400
1200
1000
800
600
400
200
0NEAMAR
NWA
Depth, m
1800
2000
2200
2400
2600
2800 Mean
± SE
Min–Max
Fig. 7.
Mean depths of capture by region (NEA, NWA, and MAR) for Jensen’s skate,
Amblyraja jenseni
, in the North Atlantic.
Size Distribution
According to the previously available size data (66
records) taken from trawl and longline catches,
TL
ranged from 19.4 to 122 cm with a mean of 70.36 ±
2.99 cm (Fig. 8). The most abundant size classes were
46–55 cm
TL
(15.2%), 61–70 cm
TL
(19.7%) and
81–85
TL
cm (12.1%). Earlier, we noted that there
were regional differences in the size composition of
this species (Orlov et al., 2006), largely due to the fact
that most small specimens were caught in the waters of
NWA and NEA (average length 49.68 and 46.85 cm
TL
, respectively), while on the MAR, Jensen’s skates
were significantly larger (average 92.61 cm
TL
).
Recent records have updated this information. As
before, the smallest individuals were reported from the
NWA, with an average length of 49.55 cm
TL
. The
largest specimens were caught along the MAR (the
average length of 82.60 cm
TL
), and those from the
NEA were intermediate in size (average 72.62 cm
TL
).
Previously Orlov et al. (2006), based on limited
material, showed that the size of Jensen’s skate did not
8
7
6
5
4
3
2
1
0
96–100
9195
86–90
66–70
36–40
<20
61–65
21–25
81–85
Total length, cm
Number of specimens
9
>110
71–75
46–50
51–55
2630
31–35
106–110
56–60
7680
41–45
101–105
Fig. 8.
Size distribution (
TL
) of Jensen’s skates,
Amblyraja jenseni
, collected from the North Atlantic (mean = 70.36 ± 2.99 cm
TL
).
492
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ORLOV, COTTON
Table 5.
Variations of Jensen’s skate
Amblyraja jenseni
coloration
Character*
(individuals with expressed
character, %)
Material examined, sex (condition)
1
(P)
2
(P)
3
(P)
4
(P)
5
(P)
6
(P)
7
(P)
8
(P)
9
(P)
10
(P)
11
(P)
12
(P)
13
(P)
14
(P)
15
(P)
16
(F)
17
(F)
18
(F)
19
(F)
TL
, mm 845 686 604 542 833 629 369 270 615 na 510 675 na 473 691 1065 696 1113 1035
Dorsal surface
Overall coloration light
brown (10.5) –––––––+–––––+–––––
Overall coloration dark
brown (42.1) ––––––+–+–++––++–++
Overall coloration greyish
brown (47.4) ++++++–––+––+–––+––
Dark edge on wings (70.6)+–±+±+++–+–++–++++–
Dark spots on disc (73.3) ++±+–±+±–+––++±++++
Alternate dark and light
bands on tail (68.8) +–±±++na+–+––++–++++
Ventral surface
Overall coloration light
(31.6) –+––++––+–––++–––––
Dark edge on wings (31.6)–+––++––+–––++–––––
Dark areas on lower poste
rior
V
lobes (31.6) –+––++––+–––++–––––
Dark flank of abdomen
(31.6) –+––++––+–––++–––––
Dark areas in central part of
V
(15.8) ––––++––––––+––––––
Dark tail (18.8) –±––+±––+–––+±–––––
Overall coloration dark
(68.4) +–++––++–+++––+++++
JOURNAL OF ICHTHYOLOGY
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NEW DATA ON THE RARE DEEPSEA SKATE
Amblyraja jenseni
493
Table 5.
(Contd.)
Character*
(individuals with expressed
character, %)
Material examined, sex (condition)
1
(P)
2
(P)
3
(P)
4
(P)
5
(P)
6
(P)
7
(P)
8
(P)
9
(P)
10
(P)
11
(P)
12
(P)
13
(P)
14
(P)
15
(P)
16
(F)
17
(F)
18
(F)
19
(F)
TL
, mm 845 686 604 542 833 629 369 270 615 na 510 675 na 473 691 1065 696 1113 1035
Light areas:
from snout tip to lower
lip (31.6) +–++––+–––++–––––––
on snout (31.6) –––––––+–+––––+++–+
around nostrils (15.8) –––––––+––––––+–+––
around mouth (33.3) –––––––+–±––––+++++
around gill slits (63.2) +–++––++–+++––+++–+
as triangle on abdomen
down to anus (15.8) +–––––+–––+––––––––
as triangle in the part of
abdomen (52.6) ––++–––+ +–+––+++++
around anus (29.4) na–++––+na––++–––––––
above anus (21.1) –––––––+–+–+––+––––
on anterior
V
lobe (47.4)+–++––++–+++––+––––
on posterior
V
lobe
(35.3) +–++––+na–++±–––––––
in the central parts of
wings (31.3) +–++––+±–±+±–––––––
Between gills (50.0) +–++––++–+++––+–––±
On claspers (75.0 of males) + + + + + + ±
Characters: “+”—expressed, “–”—not expressed, “±”—weakly expressed; na—not available; specimens: P—preserved, F—fresh caught). Numbering of individual specimens
(
n
= 19) follows Table 1. * When calculating the percentage of individuals with a particular character, specimens with weakly expressed character (±) or without available data (na)
were excluded from the analysis.
494
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ORLOV, COTTON
vary with depth of capture, i.e. juveniles and adults of
the species were found at similar depths. Our analysis
in the present study included additional data (Fig. 9)
and confirmed these conclusions, i.e. immature and
mature skates were found in a wide depth range from
364 to 2548 m. Orlov et al. (2006) determined the rela
tionship between the length (
TL
) and body weight (
W
)
of Jensen’s skate, based on limited material (14 speci
mens) with the equation:
W
= 3.1
×
10
–3
TL
3.2284
(
R
2
= 0.976).
In the present study we used additional data
(30 specimens) to slightly adjust the relationship
(Fig. 10) with the following equation:
W
= 1.8
×
10
–3
TL
3.505
(
R
2
= 0.985).
Sexual Dimorphism
In our previous publication (Orlov et al., 2006), we
noted sexual dimorphism in size: mean male lengths
and weights were significantly larger than females
(means = 80.30 cm
TL
, 8302 g; 72.31 cm
TL
, 6445 g,
respectively). Reanalysis with new data revealed a
somewhat different picture (Table 6), with mean
female lengths and weights slightly larger than males
(73.55 cm
TL
, 5826 g; 68.30 cm
TL
, 5760 g, respec
tively), although these differences were statistically
insignificant. The previously reported depths of cap
ture for males and females differed, with average val
ues of 1860 and 1693 m, respectively. Considering new
data (Table 6) depths of capture for males and females
remain statistically insignificant.
ACKNOWLEDGMENTS
Preparation of this manuscript would have been
impossible without the help of many of our colleagues.
Ingvar Byrkjedal (Zoological Museum, University of
Bergen, Bergen, Norway), Karsten Hartel and
Andrew Williston (Museum of Comparative Zoology,
Harvard, United States), Maurice Clarke and Graham
Johnston (Marine Research Institute, Galway, Ire
land) made it possible to examine specimens and pro
vided collection data for this study. John Gordon
(Scottish Association for Marine Sciences, Oban,
Scotland), Pascal Lorance (IFREMER, Plouzané,
France), Graham Johnston, Francis Neat (Marine
Scotland Science, Aberdeen, Scotland), Richard
Haedrich (Memorial University, St. John’s, Canada),
Dave Kulka (Northwest Atlantic Fisheries Science
Table 6.
Differences between male and female Jensen’s skates
Amblyraja jenseni
in capture depths and sizes
Sex Depth, m Total length, cm Body weight, g
Females
N
= 30
N
= 31
N
= 13
Males
N
= 31
N
= 32
N
= 17
Variations of character above the line, mean value ±
SE
under the line,
N
—number of specimens.
3642548
1642 ± 91

25–112
73.55 ± 3.87

118–12 190
5826 ± 1104

4932311
1683 ± 81

58–11 610
5760 ± 884

120
100
80
60
40
20
300025002000150001000500
Depth, m
Total length, cm
Fig. 9.
Size distribution (
TL
) by depth for the Jensen’s
skate,
Amblyraja jenseni
, collected from the North Atlantic.
14000
12000
8000
6000
4000
2000
120100804006020
Total length, cm
Weight, g
10000
Fig. 10.
Length and weight relationship for Jensen’s skate,
Amblyraja jenseni
, in the North Atlantic.
JOURNAL OF ICHTHYOLOGY
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NEW DATA ON THE RARE DEEPSEA SKATE
Amblyraja jenseni
495
Center, St. John’s, Newfoundland & Labrador, Can
ada), Ralf Thiel (University of Hamburg, Biocenter
Grindel and Zoological Museum, Hamburg, Ger
many) and Peter Bartsch (Museum für Naturkunde,
Leibniz Institute for Evolution and Biodiversity Sci
ence, Berlin, Germany) provided data on individual
captures. Nicola Cousins (Oceanlab, University of
Aberdeen, Newburgh, Scotland) kindly shared under
water images of Jensen’s skates made by the ROBIO
lander.
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... Jensen's Skate is demersal on continental and insular shelves and slopes at depths of 165-2,550 m (Orlov andCotton 2015, Last et al. 2016). It reaches a maximum size of 122 cm total length (TL); females mature at 85 cm TL and males between 75-80 cm TL (D.W. Kulka unpubl. ...
... data 2019). Reproduction is oviparous, and the smallest free-swimming individual was 18 cm TL (Orlov andCotton 2015, D.W. Kulka unpubl. data 2019). ...
... Discard mortality is likely to be high in longline fisheries due to automatic hook removal. This species seems to be more abundant at depths of 1000 m or deeper on the Newfoundland and Labrador shelf and 1400 m for the North Atlantic, and therefore is beyond the reach of most fisheries in the region (Orlov andCotton 2015, D.W. Kulka unpubl. data 2019). ...
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Fishing trials with bottom fixed gears (primarily gillnets but also shrimp and crab traps and longlines) were conducted on the continental slope off Nova Scotia in August 1991. Fishing was conducted at several depths between 500 and 2800 m in two areas, one on the open slope south of Emerald Bank and the other at the mouth of The Gully, a large canyon. Catches by gillnets accounted for about 90% of the total and were predominated by deepwater chimaera (Hydrolagus affinis), black dogfish (Centroscyllium fabricii) and Portuguese shark (Centroscymnus coelolepis). The most frequently caught species in traps were snubnose eel (Simenchelys parasitica) and abyssal grenadier (Coryphaenoides armatus). Variations in catches by depth and area are described, and comparisons are made with catches from otter trawl surveys at similar depths with regard to the most prominent species caught and their size compositions.
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Recent studies show the need for defined methods of systematically studying and describing skates. Disc width is proposed as the basis for proportional measurements of various parts of the disc, tail, fins, and head; of distances between certain spines; and of dimensions of ocellus. Methods are proposed for measurements of the cranium and the egg-capsule, and for counting vertebrae, pelvic radials, tooth rows, numbers of spines, rows of alar and malar hooks, and turns in the valvular intestine. Suggestions are given for description of spines, of prickles in various specific regions, of coloration, of cranium, of clasper, and of egg-capsules.