Identity of stock of redfish
Sebastes mentella in the pelagic Irminger Sea and adjacent waters
(from results of Russian investigations)
by
V.N. Shibanov, S.P. Melnikov, Yu.I. BakayKnipovich Polar Research Institute of Marine Fisheries
and Oceanography (PINRO),Murmansk, Russia
Stroganov A.N. and G.G.Novikov Moscow State University, Moscow, Russia
slide 1
Single-stock hypothesis: All S. mentella in the Irminger Sea and adjacent waters is one stock and is segregated according to age/size/maturation.
The extruded larvae are found over one big area.
Main nursery area on the shelf of West- and East-Greenland. .That all the morphological and biological characters used to phenotype the redfish, incl. parasite infestation, are related to growth, age and/or the environment. The overall genetic distances are small among locations and depthsMorphometric data/results did not reveal any clear stock structure in the area (except Flemish Cap)Otolith shape and trace element analyses did not reveal any stock structure in the areaParasitological data did not reveal any clear stock structure in the areaConsider to keep it a single stock until better (improved) sampling has been conducted and more conclusive evidences have been put forward
slide 1 continue
Three-stocks hypothesis: The three described components are biologically different stocks.
•Microsatellite test on material from shelf deep-sea S. mentella at Iceland shows significant difference to pelagic deep-sea S. mentella in deeper pelagic waters of the northern Irminger Sea.
•If distribution of females and males in maturity stage 3 is representative for showing the area of larvae extrusion and mating, respectively, then the distribution maps of this maturity stage show separate larvae extrusion and mating areas for oceanic phenotyped S. mentella, pelagic deep-sea phenotyped S. mentella, and Icelandic shelf deep-sea phenotyped S. mentella (in the latter case, to a lesser extent).
•Deviations from Hardy-Weinberg law, statistical tests of microsatelite genetic data (those data sets containing samples from all areas and depths), AFLP genetic data and fatty acid data show up to three different, and statistically significant, groups. Fatty acid results also group the fish significantly into three groups in this area.
slide 2
The principal criteria to distinguish a population/stock/management unit are as follows:
•stability in time; •full range of age groups/ life cycle stages;•self-reproduction;•spatial and/or temporal isolation from analogous groups of the same species.
For the majority of widespread fish species, which population habitat area has a complex functionally divided structure, an extra criterion is: functionally divided population habitat area with all subareas (reproduction, feeding, wintering and nursery areas).
slide 3Scheme of functional structure of the habitat and ontogenetic migration of S. mentella in the North Atlantic: 1 – direction of larvae and fry drift; 2 – direction of immature individuals migration; 3 – direction of return migration of maturing and mature individuals; 4 – area of reproduction; 5 – distribution area of immature individuals; 6 - feeding area.
- 4
- 5
- 6
slide 4 Scheme of the North Atlantic Currents:
-7 0° -6 5° -6 0° -5 5° -5 0° -4 5° -4 0° -3 5° -3 0° -2 5° -2 0° -1 5°4 5°
5 0°
5 5°
6 0°
6 5°
7 0°
0,8
0,8
0,8
1-3
1-3
1-3
4-54-5
4-5
4-5
1-3
4-6
5,3
5,6
5,4
8-11
8-12
6-12
6-126-13
6-13
6-13
6-13
Distribution and mean
length (cm) of larvae, fry and juveniles
of S. mentella
in the North Atlantic.
Warm currents (1): NaC - North Atlantic; IC - Irminger; Cold currents (2): EgC - East Greenland; WgC - West Greenland; LC - Labrador; boundary of subpolar cyclonic gyre (3); isobathes (4).
slide 5slide 5 Length composition of redfish in the layers 0-500 m (A), Length composition of redfish in the layers 0-500 m (A),
500-500- 1000 m (B) in the Irminger Sea in 1995-2003.1000 m (B) in the Irminger Sea in 1995-2003.
Age composition of redfish in the layers 0-500 m (A), 500-1000 m (B) in the Irminger Sea in 1995-2003.
0
5
10
15
20
25
%
6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
a Males n=4444
Females n=3425
0
5
10
15
20
25
%
6 8 10 12 14 16 18 20 22 24
Age, years
b Males n=40603
Females n=55907
a
0
5
10
15
20
22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
%
Males n=13326 L=34,9
Females n=8671 L=35,8
b
0
5
10
15
20
22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Length, cm
%
Males n=40603 L=39,4
Females n=55907 L=40,0
slide 6 Linear growth of redfish males and females in the layers 0-500 m (1), 500-1000 m (2).
Males
0
10
20
30
40
50
60
7 9 11 13 15 17 19 21 23 25Age, years
Leng
th, c
m
1 n=575
2 n=1968Females
0
10
20
30
40
50
60
7 9 11 13 15 17 19 21 23 25Age, years
Leng
th, c
m
1 n=4102 n=2126
Weight growth of redfish males and females in the layers 0-500 m (1), 500-1000
m (2)
Females
0200
400600
8001000
12001400
1600
7 9 11 13 15 17 19 21 23 25Age, years
Wei
ght,
g
1 n=4102 n=2126
Males
0
200
400
600
800
1000
1200
1400
1600
7 9 11 13 15 17 19 21 23 25Age, years
Wei
ght,
g
1 n=5752 n=1968
slide 7 Maturation of redfish by length groups in the layers 0-500 m (A), 500-1000 m (B)
Redfish maturation by age groups in the layers 0-500 m (A), 500-1000 m (B).
a
0
20
40
60
80
100
6 8 10 12 14 16 18 20
%
Males n=575
Females n=410
b
0
20
40
60
80
100
6 8 10 12 14 16 18 20Age, years
%
Males n=1968
Females n=2126
a
0
20
40
60
80
100
25 27 29 31 33 35 37 39 41 43 45 47 49
%
Males n=2435
Females n=1695
b
0
20
40
60
80
100
25 27 29 31 33 35 37 39 41 43 45 47 49
Length, cm
%
Males n=8941
Females n=8090
Collection areas
Irminger sea Polymorphic systems
0-500 м N 501-1000 м N Rosengarten
bank N
Outer- Bailey bank
N SW slope of Iceland
N Collection
years
0,494 170 0,711 200 - - - - - - 1999 0,606 80 0,796 120 - - - - - - 2000 0,574 781 0,687 308 0,548 177 0,716 74 0,610 355 2001
MEP-2*
0,550 300 0,572 479 - - - - - - 2002 average 0,560 1331 0,653 1107 0,548 177 0,716 74 0,610 355
1,000 170 0,990 200 - - - - - - 1999 1,000 80 0,975 120 - - - - - - 2000 0,996 781 0,957 308 1,000 177 1,000 74 0,983 355 2001
MDH*
0,998 300 0,992 479 - - - - - - 2002 average 0,997 1331 0,980 1107 1,000 177 1,000 74 0,983 355
1,000 170 0,992 200 - - - - - - 1999 1,000 80 0,996 120 - - - - - - 2000 0,994 781 0,997 308 0,994 177 1,000 74 0,997 355 2001
PGI*
0,998 300 1,000 479 - - - - - - 2002 average 0,996 1331 0,997 1107 0,994 177 1,000 74 0,997 355
1,000 170 0,992 200 - - - - - - 1999 PGM-1* (muscle) 1,000 80 1,000 120 - - - - - - 2000 average 1,000 250 0,995 320 - - - - - -
0,997 170 1,000 200 - - - - - - 1999 1,000 80 1,000 120 - - - - - - 2000 1,000 781 1,000 308 1,000 177 1,000 74 1,000 355 2001
IDH*
0,998 300 1,000 479 - - - - - - 2002 average 0,999 1331 1,000 1107 1,000 177 1,000 74 1,000 355
slide 8
Frequency of dominant allele in polymorphic
loci of Sebastes mentella (1999-2002).
100100
100100
100
100100
6060
60
60
6060
60
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
6-8 9-11 12-14 15-17 18-20 21-23 24-25
Age groups
ob
serv
ed a
llel
e fr
equ
ency
, %
slide 9Maturation of males and females of redfish by age groups in the layers 0-500 m (A),
500-1000 m (B)
slide 10
S. mentella infestation with Sphyrion lumpi and occurrence of fish with pigment patches on the skin in different areas of the Irminger
Sea and adjacent waters in 2001Infectiousness NEAFC NAFO Significance
of differences
(P)
Southwestern Iceland
Zone
Open part of the Irminger Sea
South-eastern
GreenlandZonenorth south
Level of infestation
with Sphyrion
lumpi copepod *
Prevalence,%
males 43,4 38,2 37,9 28,9 31,2 > 0,05
females 59,9 49,5 58,4 44,1 44,3 > 0,05
males+ females
52,3 42,7 46,2 36,6 37,1 > 0,05
Abundanceindex
males 0,6 0,6 0,6 0,5 0,6 > 0,05
females 1,6 1,3 1,4 1,0 1,2 > 0,05
males+ females
1,1 1,0 1,0 0,8 0,9 > 0,05
Occurrence of redfish with pigment patches
(spots) on the skin, %
males 15,8 15,5 20,1 13,8 15,8 > 0,05
females 22,5 23,8 32,7 23,0 24,6 > 0,05
males+ females
19,2 20,2 24,9 18,7 18,8 > 0,05
* - prevalence (%) and abundance index taking into account the remains of the copepod parasitizing (alive S. lumpi + old cephalothoraxes of S. lumpi).
ConclusionsConclusions
1.1. During the study of the intra-species structure in During the study of the intra-species structure in the North Atlantic it was ascertained that there the North Atlantic it was ascertained that there exists a single population of S. mentella.exists a single population of S. mentella.
2.2. The habitat is subdivided into two functional areas. The habitat is subdivided into two functional areas. The area of reproduction and feeding is in the The area of reproduction and feeding is in the oceanic pelagic waters of the Irminger and oceanic pelagic waters of the Irminger and Labrador seas and is inhabited with mature Labrador seas and is inhabited with mature individuals. The main reproduction area is above individuals. The main reproduction area is above the slopes of the Reykjanes Ridge. Immature and the slopes of the Reykjanes Ridge. Immature and maturing individuals are distributed in the margins maturing individuals are distributed in the margins of the population habitat on the slopes of of the population habitat on the slopes of Greenland and Canada, in the nursery area.Greenland and Canada, in the nursery area.
3.3. The population habitat of The population habitat of S. mentellaS. mentella is contained is contained within the sub-polar cyclonic gyre.within the sub-polar cyclonic gyre.
4.4. The fishable stock of The fishable stock of S. mentellaS. mentella in the pelagic in the pelagic waters of the Irminger and Labrador seas is the waters of the Irminger and Labrador seas is the spawning stock of the spawning stock of the S. mentellaS. mentella population. population.
5.5. When working out management measures for When working out management measures for S. S. mentellamentella fisheries in the Irminger Sea and adjacent fisheries in the Irminger Sea and adjacent waters it is biologically grounded to keep the waters it is biologically grounded to keep the current regime of the stock exploitation and two current regime of the stock exploitation and two practical management units, in the pelagic waters practical management units, in the pelagic waters and on the shelf. and on the shelf.
