Hydrobiologia

, Volume 590, Issue 1, pp 115–121

The genetic variability of the red king crab, Paralithodes camtschatica (Tilesius, 1815) (Anomura, Lithodidae) introduced into the Barents Sea compared with samples from the Bering Sea and Kamchatka region using eleven microsatellite loci

Authors

    • Institute of Marine Research
  • Christian Smith
    • Gene Conservation Laboratory, Alaska Department of Fish and Games
  • Zac Grauvogel
    • Gene Conservation Laboratory, Alaska Department of Fish and Games
  • Lisa Seeb
    • Gene Conservation Laboratory, Alaska Department of Fish and Games
Invasive Crustacea

DOI: 10.1007/s10750-007-0763-x

Cite this article as:
Jørstad, K.E., Smith, C., Grauvogel, Z. et al. Hydrobiologia (2007) 590: 115. doi:10.1007/s10750-007-0763-x

Abstract

The intentional introduction of red king crab, Paralithodes camtschatica (Tilesius, 1815) in the Barents Sea represent one of a few successful cases and one that now supports a commercial fishery. Introductions of alien species into new environments are often associated with genetic bottlenecks, which cause a reduction in the genetic variation, and this could be important for the spreading potential of the species in the Atlantic Ocean. Red king crab samples collected in the Varangerfjord located on the Barents Sea (northern Norway) were compared with reference crab samples collected from the Bering Sea and Kamchatka regions in the Pacific Ocean. All samples were screened for eleven microsatellite loci, based on the development of species-specific primers. The observed number of alleles per locus was similar, and no reduction in genetic variation, including gene diversity and allelic richness, was detected between the Varangerfjord sample and the reference sample from Okhotsk Sea near Kamchatka, indicating no genetic bottlenecking at least for the microsatellite loci investigated. The same results were found in comparison with the sample from Bering Sea. The level of genetic differentiation among the samples, measured as overall FST across all loci, was relatively low (0.0238) with a range of 0.0035–0.1000 for the various loci investigated. The largest pairwise FST values were found between the Bering Sea and Varangerfjord/Barents Sea samples, with a value of 0.0194 across all loci tested. The lowest value (0.0101) was found between the Varangerfjord and Kamchatka samples. Genetic differentiation based on exact tests on allele frequencies revealed highly significant differences between all pairwise comparisons. The high level of genetic variation found in the Varangerfjord/Barents Sea sample could be of significance with respect to further spreading of the species to other regions in the North Atlantic Ocean.

Keywords

Paralithodes camtschaticaRed king crab introductionBarents SeaBering SeaKamchatka regionGenetic variabilityMicrosatellites

Introduction

Paralithodes camtschatica (Tilesius, 1815) is valuable commercial species. The Russians initially introduced the species into the Barents Sea during the 1930’s (Orlov & Karpevich, 1965) to improve the economy of the coastal fishery and increase the living standards of the local population (Orlov & Ivanov, 1978). But this translocation was unsuccessful. In 1961, when the transportation method was improved, 1.5 million stage I zoea collected as eggs off Vladivostok were released mainly in Kol’skij Zaliv and Kolsky Bay close to Murmansk. About 10,000 juveniles from 1 to 3 years old, and 2,609 adults (1,655 females and 954 males) were released in the same area from 1961 to 1969 (Orlov & Ivanov, 1978). They were mainly caught in Peter the Great Bay and off the southeastern coast of Kamchatka in the Sea of Okhotsk. Later (1977–1978) a further 1,200 adults were transferred from the Far East and released in Kolsky Bay (Kuzmin et al., 1996).

A period between 10 and 15 years was expected before the crabs were fully acclimatised in the Barents Sea (Orlov & Karpevich, 1965). But the first red king crab was caught in Kolsky Bay during 1974, and then 2 years later, about 150 km from the original release area, from in the inner part of Varangerfjord, Norway (Kuzmin & Olsen, 1994; Rafter et al., 1996). Reports indicated that red king crabs were common in Norwegian by-catches by the 1980’s and more frequent from the beginning of 1990 in those of the Russian region (Kuzmin et al., 1996). In 1992, the red king crab was so numerous in the south of the Varangerfjord that it became a nuisance to the local fishermen. By November the same year, the Joint Russian-Norwegian Fisheries Commission became aware of the increasing population of red king crab in the area and requested both countries to intensify and co-ordinate further investigations (Kuzmin et al., 1996). Since that time the Institute of Marine Research in Bergen and the Polar Research Institute of Marine Fisheries and Oceanography in Murmansk have conducted investigations focused on geographic distribution, stock size and recruitment of the species.

Introductions of alien species into new environments are often associated with genetic bottlenecks, which lead to a reduction in the genetic variation. Recent examples include the intentional introduction of Atlantic salmon (Reilly et al., 1999) and rainbow trout (Ward et al., 2003) into Australia as aquaculture species. For unintended introductions via ballast water (Carlton, 1985), a number of genetic methods have been developed to improve the understanding of the invasion process (Geller et al., 1994, 1997; Stoner et al., 2002; Ward & Andrew, 1995; Andrew & Ward, 1996). Estimates of the level of genetic diversity and allele frequencies of genetic markers can be used to look for potential source of the invaders by comparing with samples from the species natural distribution. Thus estimates of the genetic relationship to potential populations of origin will provide important genetic and biological information about the spreading potential of the introduced species (Ward & Andrew, 1995).

Earlier studies, using allozymes (Seeb et al., 1989; Jørstad et al., 2002) revealed a low level of polymorphism and therefore limited possibility to compare the introduced Barents Sea red king crab with reference populations from the Pacific. Recent development in microsatellite DNA analyses (Seeb et al., 2002), however, provided new and more sensitive tools for genetic studies in this species. In this study eleven microsatellites have been used to compare samples taken from the Barents Sea with reference samples from the western Pacific. The main focus here was to compare the level of genetic variability, which could be crucial with regard to future spread of the introduced Barents Sea red king crab in the northeast Atlantic.

Materials and methods

Sample collection

On the Norwegian side the fishery for the Barents Sea red king crab started at Varangerfjord in northeast Norway. The first samples (white muscle from legs; see Jørstad et al., 2002) were collected from commercial catches delivered at Buøynes during the fishery in 1995. Some additional samples were collected in 2002. A combined sample (N = 49) from the Varangerfjord region (69.99 °N; 30.32 °E) was set up and used in comparisons with the reference samples. DNA was extracted from the samples with a Qiagen DNA extraction kit at Institute of Marine Research in Bergen.

Gene Conservation Laboratory at Alaska Department of Fish and Games, Anchorage, has a large collection of samples of red king crab from the northern Pacific Ocean. Two reference samples were selected for comparison with the Barents Sea population. One sample (N = 49) was collected from Pribilof Islands (56.82 °N; 170.00 °E) and was representative for the Bering Sea, while the second sample (N = 70) was from the Okhotsk Sea (53.50 °N; 155.63 °E) in the Kamchatka region, Russia. The latter sample were actually DNA extractions provided by Russian contacts and transferred to Gene Conservation Laboratory in Anchorage. The sample locations are numbered and given on the map in Fig. 1.
https://static-content.springer.com/image/art%3A10.1007%2Fs10750-007-0763-x/MediaObjects/10750_2007_3612_f1.gif
Fig. 1

Introduction of red king crab (Paralithodes camchaticus) from the Pacific Ocean into the Barents Sea in the northeast Atlantic. Donor areas were Peter the Great near Vladivostock (A) and west Kamchatka in Okhotsk Sea (B). Release site was near Murmansk on the Kola Peninsula, Russia. Samples of Barents Sea red king crab were collected in Varangerfjord in northern Norway (1) and compared with reference samples from Okhotsk Sea (2) and Bering Sea (3)

Microsatellite analyses

Two groups of microsatellite primers specific for red king crab were used. The first group consisted of six primers, which have been described more in details earlier (Seeb et al., 2002). The second group were developed recently and consisted of five primers. The details of those primer sequences, PCR conditions and multiplexing of microsatellite primers are described elsewhere consisted of six dinucleotide primers (Seeb et al., unpublished). The PCR reactions were carried out in 10 ul reaction volumes using an MJ research PTC-225 Thermalcycler.

Microsatellites were size fractionated using an ABI 3730 capillary sequencer with v2.0 collection software (ABI 2002c). Samples were prepared for injection following instructions included with the GeneScan500LIZ standard. Data were analyzed using the local Southern sizing algorithm in the GeneMapper software v3.5 (ABI 2002b). Alleles for each of the eleven loci were scored and data were tabulated for importing into statistical software also using GeneMapper v3.5.

Statistical comparisons

The samples were compared using the GENEPOP computer package (Raymond & Rousset, 1995), version 3.3, March 2001. The exact tests in GENEPOP were used for testing for population differentiation and F-statistics were calculated according to Weir & Cockerham (1984) as implemented in GENEPOP. FSTAT (Goudet, 1995) was used for calculation of gene diversity and allelic richness. The program BOTTLENECK was used to test the data for evidence of recent bottlenecks (Luikart & Cornuet, 1998).

Results

Comparisons of different estimates of genetic variability are given in Table 1. These are given as gene diversity and allelic richness for each loci for the three samples analysed and there are no indications of reduction in the level of genetic variation in the Barents Sea red king crab. As shown in Table 2, the sample from Varangerfjord/Barents Sea has approximately the same total number of alleles at the eleven microsatellite loci as the two reference samples: 196 alleles in the Barents Sea sample and 198 and 194 in the Bering Sea and Okhotsk Sea, respectively, indicating no loss of genetic variation in the introduced population. There was no evidence of a genetic bottleneck in the Barents Sea sample.
Table 1

Comparison of genetic variability (gene diversity, allelic richness, Fis) in the Barents Sea red king crab (Varangerfjord) with two reference areas in the Pacific Ocean (Okhotsk Sea; Bering Sea)

Locus

Gene diversity

Allelic richness

Fis

Varangerfjord (N = 49)

Okhotsk Sea (N = 49)

Bering Sea (N = 70)

Varangerfjord (N = 49)

Okhotsk Sea (N = 49)

Bering Sea (N = 70)

Varangerfjord (N = 49)

Okhotsk Sea (N = 49)

Bering Sea (N = 70)

PCA13

0.973

0.972

0.951

38.056

36.000

31.650

0.035

0.083

0.159

PCA24

0.933

0.897

0.908

20.288

18.662

19.685

0.111

0.131

0.096

PCA4

0.946

0.970

0.936

28.663

36.721

24.126

0.166

0.386

0.229

PCA14

0.715

0.835

0.793

15.993

14.926

15.455

0.366

0.267

0.337

PCA20

0.056

0.078

0.048

1.998

2.000

1.967

0.020

0.032

0.019

PCA5

0.932

0.952

0.938

21.736

26.553

22.816

0.518

0.622

0.617

PCA101

0.886

0.891

0.865

14.453

15.598

12.945

0.022

0.098

0.090

PCA103

0.723

0.792

0.818

8.718

8.919

8.624

0.086

0.085

0.038

PCA100

0.734

0.742

0.658

5.991

5.999

6.770

0.332

0.207

0.107

PCA104

0.880

0.860

0.855

11.848

11.795

10.695

0.100

0.065

0.035

PCA107

0.921

0.896

0.927

22.120

18.483

18.394

0.078

0.094

0.094

Table 2

Comparison of the number of alleles per locus in the Barents Sea red king crab (Varangerfjord) with two reference areas in the Pacific Ocean (Okhotsk Sea; Bering Sea)

Locus

Alleles per locus

Fst–value

P–value

Varangerfjord (N = 49)

Okhotsk Sea (N = 49)

Bering Sea (N = 70)

All samples

PCA13

39

36

37

57

0.0153

<0.0001

PCA24

21

19

22

24

0.0035

<0.0001

PCA4

30

37

28

47

0.1

<0.0001

PCA14

17

15

18

24

0.0303

<0.0001

PCA20

2

2

2

2

−0.0061

0.0033

PCA5

22

27

25

36

0.0855

<0.0001

PCA101

15

16

14

17

0.0684

<0.0001

PCA103

9

9

9

11

−0.001

<0.0001

PCA100

6

6

7

7

0.0014

0.0049

PCA104

12

12

11

15

0.0308

0.0008

PCA107

23

19

21

28

0.0089

<0.0001

All loci

196

198

194

268

0.0238

<0.0001

Estimates of Fst obtained in global test at each locus are given and corresponding P values from the exact test for genetic differentiation (see Materials & methods)

A large range in the number of alleles at the 11 microsatellite loci was detected in the three samples. Most extreme was the PCA20 locus where only two alleles were found (Table 2). On the other hand as many as 57 alleles were identified at the PCA13 locus. The overall FST estimates across samples for each locus (Table 2) ranged from −0.001 (PCA103,) to 0.1000 (PCA4), with an average value of 0.0238 across all loci and samples. Global tests for genetic differentiation, however, revealed highly significant values for all loci analyzed as well as across loci.

Pairwise exact tests on allele frequencies revealed significant values for individual loci as well as across all loci (Table 3). The largest differentiation was detected between Varangerfjord and the Bering Sea, where ten of eleven comparisons were significant. On the other hand Varangerfjord and Okhotsk Sea were significant different at 6 loci. These observations were also confirmed by the pairwise FST values (Table 3). The overall (across all loci) FST value was 0.0101 for the comparison between Varangerfjord and Okhotsk Sea, while the highest value (0.0194) was found between Varangerfjord and the Bering Sea.
Table 3

Pairwise estimates of Fst value (below diagonal) and P values (above diagonal) from exact tests of population differentiation among the Barents Sea red king crab (Varangerfjord) and two reference areas in the Pacific Ocean (Okhotsk Sea; Bering Sea)

 

Varangerfjord

Okhotsk Sea

Bering Sea

Varangerfjord

 

<0.0001

<0.0001

Okhotsk Sea

0.010

 

<0.0001

Bering Sea

0.019

0.010

 

Discussion

Intentional introduction of red king crab into the Barents Sea more than 40 years ago by Russians was an attempt to establish an economically viable crab fishery in this region (Orlov & Karpevich, 1965; Orlov & Ivanov, 1978). The increase of crab abundance both in the Barents Sea and adjacent Norwegian fjords in the 1990s, demonstrate that this introduction has been successful (Kuzmin et al., 1996) and that the population is still increasing and extending its distribution range.

The extension of a species natural distribution area is usually accomplished by a few founding specimen which successfully adapt to the new environment. In such cases there is a risk of genetic bottlenecking and genetic drift, which normally decrease the level of genetic variability within a newly introduced population. Such characteristics are also expected in cases where species are intentionally introduced into new environments like the red king crab introduction into the Barents Sea. The results of this study found no indication of loss of genetic variability when comparing samples of the Barents Sea red king crab with two reference populations in the Pacific. In earlier studies on the genetics of this species, mainly based on allozymes (Seeb et al., 1989), low levels of genetic variation were detected, with limited power to reveal population genetic structure. In the preliminary allozyme analyses of the Barents Sea red king crab only 3 heterozygotes were totally detected in analyses of 96 specimens for eleven allozymes loci (Jørstad et al., 2002). Of course, this extreme low level of variation was of no use in a genetic comparison with the Pacific red king crab populations.

The eleven microsatellite loci that were used in this study revealed a high level of genetic variation (number of alleles) at most loci and as such offers a much more sensitive tool for detecting genetic differences as well as reductions in genetic variability. The results obtained from these comparisons, however, demonstrated the same level of genetic variation in the introduced crab population in Barents Sea as in the two Pacific reference samples. This was unexpected considering the failure in the early attempts in the 1930s (Orlov & Karpevich, 1965), but may be explained by the magnitude of the Russian introduction experiment in the 1960s (Orlov and Ivanov, 1978). All crabs, independent of stage and size, were released in the same location. Even though experienced high mortalities, there have been sufficient number of survivors that reproduced successfully to maintain the same level of genetic variation.

In recent years the population and distribution of red king crab in the Barents Sea has increased. In particular, large individuals are often found in new areas of the open Barents Sea and in new fjord systems along the Norwegian coast, indicating a western migration pattern. In the future, the crab will possibly establish self-reproducing units in new areas. And when considering the high level of genetic variability as observed in the present work, there seems to be no genetic constrains that will limit the colonization power of the Barents Sea red king crab. Russian scientists have evaluated the future spreading potential of the red king crab in western and southern directions of the northeast Atlantic. According to Ivanov (2001) the environmental conditions present no barriers for the establishment of crab populations as far south as the British Islands and Biscay Bay.

The environmental conditions in the eastern Barents Sea are different compared with Norwegian coastal habitats and fjords where the introduced red king crab has become established. The data presented here have been obtained from a relatively small number of crabs collected in Varangerfjord near the Russian border. However, the crab is now spreading over a large area in the Barents Sea, as well as along the northern regions of the Kola Peninsula and a number of the large fjords in Finnmark, Norway. Therefore it is important to investigate if minor genetic differentiation has already occurred in these different geographic regions, or if it is likely to occur in the future. Establishing genetic profiles throughout the distribution areas will be fundamental for evaluation of management strategies of the introduced crab population.

So far the environmental consequences of the red king crab introduction into the Atlantic have not been studied in detail. During the last decades, however, there has been an increasing awareness about the potential effects of intended and accidental introduction of alien species around the world (Carlton & Geller, 1993; Carlton, 2002). With reference to the potential ecological effects of such introductions, it is natural to consider both intended and accidental introductions as one of the serious threats to the present biodiversity. One example of accidental introductions of crab species on global scale involves the green crab, Carcinus maenas (Grosholz & Ruiz, 1996; Grosholz, 2002). This crab has adapted rapidly to new environments and in many cases they are aggressively competing for food, shelter and habitat with significant ecological consequences (Grosholz & Ruiz, 1996; Cohen et al., 1995). With respect to the Barents Sea red king crab there is an urgent need for detailed knowledge of ecological effects of this introduction.

Acknowledgements

This work was supported with grants from the Norwegian Ministry of Foreign Affairs.

Copyright information

© Springer Science+Business Media B.V. 2007