Signal crayfish in Lake Saimaa could be maladapted to the local conditions due to Aphanomyces astaci infection: A seven-year study

Abstract We conducted a seven-year survey (years 2009 - 2015) of the Lake Saimaa signal crayfish population. Lake Saimaa is the largest single waterbody in Finland, with a productive fishery and crayfishery. The signal crayfish were introduced to Lake Saimaa in mid-1990’s and a commercial fishery was initiated in the mid-2000s. At first, there was a small proportion of noble crayfish among the catch, but after 2007, an acute crayfish plague epidemic eradicated them, and the signal crayfish stock started showing frequent gross symptoms of chronic crayfish plague infection (e.g., melanised lesions, eroded uropods and pleopods, lost appendages with melanised stumps). This stock now shows gross symptoms of the infection at a rate of 45% to 79% of the annual trap catch, in addition to showing signs of eroded swimmeret symdrome (ESS) at a rate of 2.8 to 15.4%. The CPUE has remained rather low, between one and three crayfish throughout the survey, while the proportion of the commercial grade catch has been between 35% and 68% of the total catch. The signal crayfish populations in Lake Saimaa are still rather fragmented, and production is low. It appears that the Lake Saimaa signal crayfish population has developed slowly and is producing less than expected.

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Chronic crayfish plague infection and eroded swimmeret syndrome in Lake Saimaa (Finland) signal crayfish

Freshwater Crayfish ◽

10.5869/fc.2017.v23-1.23 ◽

2017 ◽

Vol 23 (1) ◽

pp. 23-28

Author(s):

Japo Jussila ◽

Vese Tiitinen ◽

Lennart Edsman

Keyword(s):

Chronic Infection ◽

Reproductive Output ◽

Catch Per Unit Effort ◽

Egg Hatching ◽

Signal Crayfish ◽

Aphanomyces Astaci ◽

Unit Effort ◽

History Of ◽

Crayfish Population ◽

Lake Saimaa

Abstract We present data and results from a 9-year survey (2009 – 2017) of the Lake Saimaa signal crayfish population in Finland. This population has a history of chronic infection with Aphanomyces astaci. It has now been discovered that female signal crayfish from Lake Saimaa suffer from various stages of eroded swimmeret syndrome (ESS), and male crayfish also show symptoms of ESS-like trauma (i.e., eroded swimmerets and gonopods). Our data demonstrates the prevalence of A. astaci infection, with gross symptoms prevailing throughout the duration of the entire 2009 – 2017 survey, and that prevalence of ESS among female signal crayfish is correlated with the prevalence of A. astaci infection in the population. The data shows that an increasing proportion of female crayfish suffer from ESS, and have regenerated swimmerets, however, our observations indicate that partially regenerated swimmerets do not fully function during egg hatching. Based on data and observations during the survey, we speculate that low production levels, as indicated by the low catch per unit effort (CPUE), within the Lake Saimaa signal crayfish population could be related to both high A. astaci infection levels and ESS prevalence among females. The former could be causing increasing mortality among adult crayfish and the latter could be lowering Lake Saimaa signal crayfish reproductive output.

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Fluctuations in harvest of native and introduced crayfish are driven by temperature and population density in previous years

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f09-170 ◽

2010 ◽

Vol 67 (1) ◽

pp. 157-164 ◽

Cited By ~ 10

Author(s):

Karin Olsson ◽

Wilhelm Granéli ◽

Jörgen Ripa ◽

Per Nyström

Keyword(s):

Time Lag ◽

Mating Season ◽

Astacus Astacus ◽

Growth Season ◽

Signal Crayfish ◽

Noble Crayfish ◽

Crayfish Population ◽

Effects Of Temperature ◽

Parsimonious Model ◽

Large Adult

The effects of temperature and density on annual fluctuations in catches of large adult crayfish are evaluated using time series analysis. We tested if temperature during different stages of the crayfish life cycle influenced observed catches from 1946 to 2007 in Lake Bunn (Sweden). From 1946 to 1974, native noble crayfish ( Astacus astacus ) inhabited the lake, but then, crayfish plague wiped out the whole population. In 1985, the exotic signal crayfish ( Pacifastacus leniusculus ) was introduced and is still present. This made it possible to model the two species separately and compare how temperature and density influence the abundance of large adult crayfish. The best models indicate that both climatic- and density-dependent factors influence the observed fluctuations and there was a time lag for most factors included in the best models. Winter temperature had the strongest influence on fluctuations of both species. Also, density dependence was included in the best model for both species. Growth season for noble crayfish and temperature during the mating season for signal crayfish were also present in the most parsimonious model. Based on our findings, it is difficult to predict how further climate warming will affect crayfish population dynamics in freshwaters.

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Relaxed attitude towards spreading of alien crayfish species affects protection of native crayfish species: case studies and lessons learnt from a Fennoscandian viewpoint

Freshwater Crayfish ◽

10.5869/fc.2020.v25-1.039 ◽

2020 ◽

Vol 25 (1) ◽

pp. 39-46

Author(s):

Japo Jussila ◽

Lennart Edsman

Keyword(s):

Competitive Advantage ◽

Pacifastacus Leniusculus ◽

Astacus Astacus ◽

Signal Crayfish ◽

Aphanomyces Astaci ◽

Noble Crayfish ◽

Native Crayfish ◽

Chronic Carrier ◽

Highly Virulent ◽

Crayfish Species

Abstract The spreading of the alien signal crayfish (Pacifastacus leniusculus) is posing an ongoing threat to native European crayfish species in Fennoscandia, like the native noble crayfish (Astacus astacus). The signal crayfish is commonly a chronic carrier of the crayfish plague (Aphanomyces astaci), thus, in addition to being more competitive than noble crayfish, it also has a competitive advantage in this disease over the noble crayfish. The challenges rising from the introduction of the alien signal crayfish to Sweden, Finland and finally also Norway, are similar in nature. The licensed and unlicensed spreading of this species also has a similar history in these countries. In this paper we describe some of the patters of the spread of alien signal crayfish and highlight the detrimental nature of an alien crayfish, accompanied by a highly virulent disease, to native Fennoscandian crayfish and also to native Fennoscandian ecosystems. A halt to the further spreading of alien signal crayfish in Fennoscandia is the only means to ensure successful conservation outcomes for the noble crayfish.

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The prevalence of Aphanomyces astaci in invasive signal crayfish from the UK and implications for native crayfish conservation

Parasitology ◽

10.1017/s0031182016002419 ◽

2017 ◽

Vol 144 (4) ◽

pp. 411-418 ◽

Cited By ~ 9

Author(s):

J. JAMES ◽

S. NUTBEAM-TUFFS ◽

J. CABLE ◽

A. MRUGAŁA ◽

N. VIÑUELA-RODRIGUEZ ◽

...

Keyword(s):

Average Rate ◽

Signal Crayfish ◽

Aphanomyces Astaci ◽

Virulent Strains ◽

Pathogen Prevalence ◽

Crayfish Population ◽

To Come ◽

Group B ◽

The Uk ◽

Native Crayfish

SUMMARYThe crayfish plague agent, Aphanomyces astaci, has spread throughout Europe, causing a significant decline in native European crayfish. The introduction and dissemination of this pathogen is attributed to the spread of invasive North American crayfish, which can act as carriers for A. astaci. As native European crayfish often succumb to infection with A. astaci, determining the prevalence of this pathogen in non-native crayfish is vital to prioritize native crayfish populations for managed translocation. In the current study, 23 populations of invasive signal crayfish (Pacifastacus leniusculus) from the UK were tested for A. astaci presence using quantitative PCR. Altogether, 13 out of 23 (56·5%) populations were found to be infected, and pathogen prevalence within infected sites varied from 3 to 80%. Microsatellite pathogen genotyping revealed that at least one UK signal crayfish population was infected with the A. astaci genotype group B, known to include virulent strains. Based on recent crayfish distribution records and the average rate of signal crayfish population dispersal, we identified one native white-clawed crayfish (Austropotamobius pallipes) population predicted to come into contact with infected signal crayfish within 5 years. This population should be considered as a priority for translocation.

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Lake Hańcza – a new site for signal crayfish (Pacifastacus leniusculus Dana) occurrence in Poland

Archives of Polish Fisheries ◽

10.2478/aopf-2018-0015 ◽

2018 ◽

Vol 26 (2) ◽

pp. 141-147

Author(s):

Dariusz Ulikowski ◽

Łucjan Chybowski

Keyword(s):

Total Body Length ◽

Pacifastacus Leniusculus ◽

Catch Per Unit Effort ◽

Large Signal ◽

Signal Crayfish ◽

Orconectes Limosus ◽

Noble Crayfish ◽

Crayfish Population ◽

Total Body ◽

Average Body

Abstract Crayfish catches were conducted using traps in Lake Hańcza, which is the deepest lake in Poland. Two crayfish populations were found to co-exist in the lake: spiny-cheek crayfish (Orconectes limosus Raf.) and signal crayfish (Pacifastacus leniusculus Dana), which is a new species for this lake. Signal crayfish dominated the samples at 98.5% of the specimens caught. The crayfish occurred at depths of 1-10 m. The mean total body length of the male and female signal crayfish (TL) was 99.5 ± 17.8 mm and 96.5 ± 11.7 mm, respectively, while the average body weight (BW) was 38.7 ± 24.9 g and 26.8 ± 9.5, respectively. Chelae were damaged in 4.5% of the individuals. Fishing efficiency (catch per unit effort – CPUE) was 0.96 crayfish trap−1 night−1. Selected characteristics of the population and of individual signal crayfish from Lake Hańcza were compared with those of the two closest neighboring populations of this species in lakes Mauda and Pobłędzie. The confirmed occurrence of the relatively large signal crayfish population in Lake Hańcza excludes this lake as a possible site for native noble crayfish (Astacus astacus L.) restoration.

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Eroded Swimmeret Syndrome: Update of the Current Knowledge

Freshwater Crayfish ◽

10.5869/fc.2021.v26-1.63 ◽

2021 ◽

Vol 26 (1) ◽

pp. 63-68

Author(s):

Jappo Jussila ◽

Vesa Tiitinen ◽

Jenny Makkonen ◽

Harri Kokko ◽

Patrik Bohman ◽

...

Keyword(s):

Species Complex ◽

Current Knowledge ◽

Fusarium Species ◽

Pacifastacus Leniusculus ◽

Multiple Infection ◽

Signal Crayfish ◽

Aphanomyces Astaci ◽

Disease Agent ◽

Lake Saimaa ◽

Swedish Data

Abstract Eroded swimmeret syndrome (ESS) was first described in 2014 from Swedish signal crayfish (Pacifastacus leniusculus (Dana)), and later also from Finland, with gross symptoms and disease agent candidates identified and described by 2015. The ESS was first discovered affecting alien signal crayfish in Fennoscandia. The ESS is caused by a multiple infection involving Aphanomyces astaci (Schikora) and Fusarium species complex (SC). The ESS symptoms include first melanised spots in swimmerets, then partial swimmeret erosion and finally loss of a swimmeret. There could be a total loss of all swimmerets in the most severe cases. Both females and males can be affected by the ESS. In females, the ESS lowers reproductive success while in males the ESS often causes erosion of the gonopods and thus possible partial failure in mating. The ESS is more frequent among mature females that have reproduced once compared to immature females or those that are mature but have not yet reproduced. The proportion of females with ESS has ranged from 10 to 50% among Lake Saimaa signal crayfish in Finland and in a wider survey from Sweden the range was from 0 to 38%. Among Lake Saimaa male signal crayfish, the ESS proportion has been less than 10%, while it was only 0.6% in the Swedish data. The ESS has also been observed among alien signal crayfish in Switzerland. There are recent observations of ESS affecting narrow-clawed crayfish, Pontastacus leptodactylus (Eschscholtz), in Croatia and Romania (i.e., among native European crayfish stocks). Here, we summarise current knowledge about the ESS and speculate on a few potentially crucial impacts of this syndrome.

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Narrow-clawed crayfish in Finland: Aphanomyces astaci resistance and genetic relationship to other selected European and Asian populations

Knowledge and Management of Aquatic Ecosystems ◽

10.1051/kmae/2020022 ◽

2020 ◽

pp. 30

Author(s):

Japo Jussila ◽

Ivana Maguire ◽

Harri Kokko ◽

Vesa Tiitinen ◽

Jenny Makkonen

Keyword(s):

White Sea ◽

Phylogenetic Reconstruction ◽

Phylogenetic Position ◽

Finnish Population ◽

Genetic Studies ◽

Aphanomyces Astaci ◽

Asian Populations ◽

Noble Crayfish ◽

Crayfish Population ◽

Southeastern Region

The narrow-clawed crayfish (Pontastacus leptodactylus) is an alien species in Finland with only a few populations reported from the southeastern region during the last century. We discovered a productive population in the lake Jängynjärvi, which is upstream from the previously reported wild narrow-clawed crayfish population in that region. Preliminary studies indicated that this population is not infected with Aphanomyces astaci. We collected narrow-clawed crayfish samples from the lake Jängynjärvi population for both infection challenge and genetic studies, in order to investigate possible A. astaci resistance among this Finnish population and to evaluate their phylogenetic position that would enable us to speculate different scenarios of distribution pathways or origin of the population. The infection studies indicated that the narrow-clawed crayfish in this population were more resistant against A. astaci infection (B haplogroup A. astaci) compared to the noble crayfish (Astacus astacus) from the lake Rytky in North Savo, while all crayfish of both species in the B haplogroup A. astaci challenged groups died within 58 days post-infection. Results of the phylogenetic reconstruction indicate that the lake Jängynjärvi narrow-clawed crayfish are closely related to narrow-clawed crayfish from the lake Bolshoye near Krasnoye, located on the White Sea island of Solovestky and also populations from Tyumen region, both in Russia. This could confirm previous speculations about introduction of the narrow-clawed crayfish from Russia into Finland or could indicate previous hydrological connection.

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Signal crayfish, Pacifastacus leniusculus, as a vector for Psorospermium haeckeli to noble crayfish, Astacus astacus

Aquaculture ◽

10.1016/s0044-8486(96)01400-7 ◽

1996 ◽

Vol 148 (1) ◽

pp. 1-9 ◽

Cited By ~ 7

Author(s):

Rolf Gydemo

Keyword(s):

Pacifastacus Leniusculus ◽

Astacus Astacus ◽

Signal Crayfish ◽

Noble Crayfish

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Crayfish plague affects juvenile survival and adult behaviour of invasive signal crayfish

Parasitology ◽

10.1017/s0031182020000165 ◽

2020 ◽

Vol 147 (6) ◽

pp. 706-714 ◽

Cited By ~ 1

Author(s):

John Rhidian Thomas ◽

Chloe V. Robinson ◽

Agata Mrugała ◽

Amy R. Ellison ◽

Emily Matthews ◽

...

Keyword(s):

North American ◽

Native Species ◽

North American Species ◽

Juvenile Survival ◽

Signal Crayfish ◽

Aphanomyces Astaci ◽

The North ◽

High Infection ◽

Oomycete Pathogen ◽

The Impact

AbstractThe spread of invasive, non-native species is a key threat to biodiversity. Parasites can play a significant role by influencing their invasive host's survival or behaviour, which can subsequently alter invasion dynamics. The North American signal crayfish (Pacifastacus leniusculus) is a known carrier of Aphanomyces astaci, an oomycete pathogen that is the causative agent of crayfish plague and fatal to European crayfish species, whereas North American species are considered to be largely resistant. There is some evidence, however, that North American species, can also succumb to crayfish plague, though how A. astaci affects such ‘reservoir hosts’ is rarely considered. Here, we tested the impact of A. astaci infection on signal crayfish, by assessing juvenile survival and adult behaviour following exposure to A. astaci zoospores. Juvenile signal crayfish suffered high mortality 4-weeks post-hatching, but not as older juveniles. Furthermore, adult signal crayfish with high-infection levels displayed altered behaviours, being less likely to leave the water, explore terrestrial areas and exhibit escape responses. Overall, we reveal that A. astaci infection affects signal crayfish to a much greater extent than previously considered, which may not only have direct consequences for invasions, but could substantially affect commercially harvested signal crayfish stocks worldwide.

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