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Invasion routes, current and historical distribution of the Chinese mitten crab (Eriocheir sinensis H. Milne Edwards, 1853) in Sweden
Abstract and Figures
Single specimens of the Chinese mitten crab, Eriocheir sinensis H. Milne Edwards, 1853, have been regularly reported along the western and eastern coasts of Sweden since the 1930´s. The crab has most likely been brought from overseas via the transfer of ship's ballast water or secondarily introduced from its key European distribution areas. Since 2001 a sharp increase in the occurrence of the mitten crab has been noticed in Swedish inland waters, but the dispersal routes and distribution of the species into Sweden remain poorly known. Here we document the current and historical distribution of the Chinese mitten crab in Sweden and assess possible invasion routes. A special focus is put on the historical occurrence of crabs in Lake Vänern, which empties into the Skagerrak/North Sea and Lake Mälaren, which connects to the Baltic Sea. The existing time series available for the mitten crab from the two lakes shows a large variation in dispersal pattern between different areas within each lake. In order to detect and monitor outbreaks of the mitten crab in Sweden, an internet based reporting system was created in 2007. Museum collections and reports from the general public throughout Sweden were compared with the known occurrence of mitten crabs in Lake Vänern and Lake Mälaren. During the study, the web-based reporting system was not advertised and the general public did not get paid for reporting the information. Population densities of the crab occurred "in peaks" and unevenly over the last decade in both lakes, suggesting a pulse invasion instead of a constant supply by migration. Significant difference in male and female occurrence together with few transport possibilities between lakes suggests different invasion routes for the crabs. Reports from the general public throughout Sweden coincide with the observations from local fishermen in Lake Mälaren and Lake Vänern. Data on occurrence and abundance are discussed in relation to a potential reproduction area on the western coast of Sweden.
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... However, there are publications about the occurrence, size or sex of individuals appearing each year in the western and other parts of the Baltic Sea (e.g. Normant et al. 2000;Czerniejewski & Wawrzyniak 2006;Ojaveer et al. 2007;Drotz et al. 2010). With regard to the south-eastern coast of the Baltic Sea, short communications concerning individuals caught in the Gulf of Gdansk and in Lithuanian waters are from and Bacevičius & Gasiūnaitė (2008). ...
... It spends most of its life cycle in fresh waters, and migrates to saline waters only for reproduction. It is also worth mentioning that during the last few decades, an increase in the number of E. sinensis individuals has been observed along the entire coastal zone of the Baltic Sea (Panov 2006;Ojaveer et al. 2007;Shakirova et al. 2007;Drotz et al. 2010). However this may be related to an increasing awareness of fishermen, who report E. sinensis specimens as a by-catch during their commercial fishing activities. ...
... Moreover, they seem to be related to an unrepresentative number of catches, which depends on fishermen's 'good will', but also on weather conditions, and thus the place and time of placing fyke-nets, and on this basis it is impossible to conclude that the number of E. sinensis individuals in the waters of the southern Baltic Sea was increasing. This research shows that individuals of E. sinensis caught in eastern Polish coastal waters had a similar carapace width range to individuals caught in Sweden and Germany, as well as to those in Latvian, Finnish and western Polish coastal waters (Szczecin Lagoon; Czerniejewski & Bełdowska 2003;Herborg et al. 2003;Czerniejewski & Wawrzyniak 2006;Ojaveer et al. 2007;Drotz et al. 2010). The carapace width of individuals from the Gulf of Gdansk was similar to the size of specimens described by . ...
The Chinese mitten crab Eriocheir sinensis is a non-native species that appeared in European waters more than 100 years ago. Size and sex structure as well as biological condition of populations of Eriocheir sinensis sampled annually between 1999–2014 from the eastern Baltic Sea coast (1999–2007 Gulf of Gdansk and 2008–2014 Vistula Lagoon, Poland) were analysed. Males were dominant over females, with a sex ratio of 1.6:1. Carapace width of all collected specimens (n = 467) ranged from 33.3 to 89.1 mm and the mean values for specimens from Gulf of Gdansk and Vistula Lagoon were 62.4 ± 8.1 mm (n = 171) and 66.6 ± 7.7 mm (n = 296) respectively. There were no statistically significant differences in carapace width between males and females. It is important to note that there were no individuals with a carapace width less than 30 mm, which may indicate a lack of an established population of this species from the eastern Polish coast. The wet weight of all specimens ranged from 30.9 to 321.9 g and the mean values for all specimens from the Gulf of Gdansk and the Vistula Lagoon were 119.4 ± 45.2 g (n = 101) and 141.8 ± 47.9 g (n = 223), respectively. The wet weight of an individual was significantly correlated to carapace width and the exponent b reaching values close to 3 may indicate their good condition.
... The present study shows that isolated E. sinensis individuals have been almost ubiquitously present in the basin of the eastern Gulf of Finland at least for the past two decades. It is noteworthy that the number of finds of this species finds has been on the rise over these decades both in the Russian waters and along the entire Baltic Sea coast (Panov, 2003;2006;Wójcik-Fudalewska and Normant-Saremba, 2016;Ojaveer et al., 2007;Drotz et al., 2010). ...
... In the present study, the carapace width varied between 46.6 and 85 mm, which is consistent with size of the individuals inhabiting nearshore waters of Sweden, Germany, Latvia, Finland, and Poland (Wójcik and Normant, 2014;Herborg et al., 2003;Ojaveer et al., 2007;Drotz et al., 2010;Czerniejewski et al., 2012). Although differences in carapace width between males and females were not statistically significant, the obtained results confirm occurrence of sexual dimorphism in this species (Semen'kova, 2003;Dittel and Epifanio, 2009;Wójcik-Fudalewska and Normant-Saremba, 2016;Czerniejewski and Wawrzyniak, 2006;Czerniejewski et al., 2007;de Giosa et al., 2013). ...
New data are presented on the distribution of the alien species the Chinese mitten crab Eriocheir sinensis in the basin of the eastern part of the Gulf of Finland, the Baltic Sea. The fact of widespread occurrence of E. sinensis in bottom communities has been confirmed. During the period from 2021 to 2023, 81 adult individuals of the mitten crab were recorded; 32 of them were studied in the laboratory. Of the studied individuals, males were dominant; the sex ratio (males : females) was 3.6 : 1; females with exterior egg sacs were not found. The carapace width of the studied crabs (n = 32) ranged from 46.6 to 85 mm, averaging to 63.2 ± 1.7 mm. Males were slightly larger than females; however, statistically significant differences in cara-pace width between males and females were not detected. The paper further discusses issues related to the origin of crabs inhabiting the eastern part of the Baltic Sea and the possibility of naturalization of this species in the basin of the eastern part of the Gulf of Finland, the Baltic Sea. The conclusion is drawn about the importance of systematic monitoring of E. sinensis in the Gulf of Finland basin.
... Настоящее исследование показывает, что единичные особи E. sinensis практически повсеместно присутствуют в бассейне восточной части Финского залива, по крайней мере, в течение последних двух десятилетий. Следует также отметить, что в российских водах, как и по всему побережью Балтийского моря [Panov, 2003;Ojaveer и др., 2007;Drotz et al., 2010;Wójcik-Fudalewska, Normant-Saremba, 2016], в эти десятилетия наблюдалось увеличение числа находок этого вида. ...
... В настоящем исследовании, ширина карапакса крабов варьировала от 46.6 до 85 мм, что соответствует размерам особей, обитающих в прибрежных водах Швеции, Германии, Латвии, Финляндии и Польши [Herborg et al., 2003;Ojaveer et al., 2007;Drotz et al., 2010;Czerniejewski et al., 2012;Wójcik, Normant, 2014]. Хотя различия в ширине карапакса самцов и самок не были статистически значимыми, полученные результаты подтверждают наличие полового диморфизма этого вида [Семенькова, 2003;Czerniejewski, Wawrzyniak, 2006;Czerniejewski et al., 2007;Dittel, Epifanio, 2009;de Giosa et al., 2013;Wójcik-Fudalewska, Normant-Saremba, 2016]. ...
Представлены новые данные о распространении чужеродного вида-китайского мохнаторукого краба Eriocheir sinensis в бассейне восточной части Финского залива Балтийского моря. Подтверждён факт повсеместного наличия E. sinensis в донных сообществах. В период с 2021 по 2023 г. отмечены находки 81 особи взрослого мохнаторукого краба; 32 из которых исследованы в лаборатории. Среди исследованных особей преобладали самцы; соотношение полов (самцы: самки) составило 3.6:1.0; самок с наружной икрой не обнаружено. Ширина карапакса исследованных крабов (n = 32) изменялась от 46.6 до 85.0 мм; составляя в среднем 63.2 ± 1.7 мм. Самцы были незначительно крупнее самок, однако статистически значимых различий в ширине карапакса между самцами и самками не выявлено. Обсуждаются вопросы о происхождение крабов, обитающих в восточной части Балтийского моря и о возможности натурализации данного вида в бассейне восточной части Финского залива Балтийского моря. Делается вывод о необходимости систематического мониторинга E. sinensis в бассейне Финского залива. Ключевые слова: Eriocheir sinensis, китайский мохнаторукий краб, Финский залив, Балтийское море, биологические инвазии, распространение, размерно-половой состав, адаптация, натурализация.
... Its ability to complete its life cycle in Norway remains uncertain. In Sweden, consistent sightings of this crab along coastal areas date back to the 1930s, and it is now prevalent in Vänern (Drotz et al. 2010;Drotz et al. 2012). The crab's small larval stages are easily transported in water, but mature crabs must migrate to estuaries for spawning. ...
Reintroducing a species to an area where it is locally extinct may contribute to reestablishing the ecosystem. However, we show that such reintroductions can pose a risk to biodiversity by introducing hitchhiking invasive organisms together with the donor population. This risk was caused by more severe impacts of invasive organisms in the habitat of the donor population than the receiving environment. The freshwater resident Atlantic salmon (Salmo salar) in Sweden's River Klarälven perform feeding migrations to Lake Vänern. The upper part of the watershed, in Norway, lost its salmon population due to hydropower development that obstructed upstream migration. We conducted a risk assessment of the potential impacts on native ecosystems from invasive organisms associated with reintroducing Atlantic salmon into the Norwegian part of the watershed by importing adult salmon spawners. This assessment is crucial due to differences in the development of invasive organisms in the Swedish and Norwegian parts of the watershed. The risk of impacts was evaluated for invasive species, parasites, bacterial pathogens, and viruses that are present or likely present in the lower part of the watershed, or at risk of being introduced. We found a high risk of negative impacts associated with the parasite Gyrodactylus salaris, viral hemorrhagic septicemia virus (VHSV), Aphanomyces astaci causing crayfish plague, Renibacterium salmoninarum causing bacterial kidney disease, and Tetracapsuloides bryosalmonae causing proliferative kidney disease. In addition, 20 invasive species and pathogens were associated with a medium risk and three with a low risk. The case study contributes to a deeper understanding of how reestablishing locally extinct or diminished species can influence biodiversity conservation efforts and the health of aquatic ecosystems, underlining the importance of comprehensive planning in restoration projects. We highlight the importance of risk assessment of invasive species when considering the reintroduction of native species or dam removal.
... ;Dannheim and Rumohr (2012);Gollasch et al. (2015);Kerckhof et al. (2007);Witbaard et al. (2017) Eriocheir sinensisDrotz et al. (2010);Herborg et al. (2003);Kerckhof et al. (2007); National Biodiversity Network (NBN) Atlas(2021); Nędzarek and Czerniejewski (2021); North Western Inshore Fisheries and Conservation Authority (2020); Otto and Brandis (2011); Schoelynck et al. (2020); Silvestre et al. (2006) Hemigrapsus sanguineus Boets et al. (2012); Gittenberger et al. (2014); Landschoff et al. (2013); Soors et al. (2010) Hemigrapsus takanoi Boets et al. (2012); Dauvin et al. (2009); Geburzi et al. (2015, 2020), Gittenberger et al. (2014); Gollasch (1999); Landschoff et al. (2013); Soors et al. (2010) ...
Global shipping facilitates the introduction of invasive species and parasites via ballast water and hull fouling. Regional management of invasives may be strengthened by identifying the major routes in a network, to allow for targeted ship inspections. This study used cargo shipping records to establish the connectivity of shipping routes between ports in Ireland and other nations. 9291 records were analysed, investigating vessel residence and journey times. On average, vessels spent up to five days in port and less than five days at sea. However, there was strong variation, with general cargo ships recording up to 13 days in port. A horizon scan for species likely to invade in Ireland was incorporated for five species and their associated parasites: American razor clam, Asian shore crab, Brush clawed shore crab, Chinese mitten crab and American slipper limpet. Routes of concern are highlighted and a general framework for effective management is outlined.
... This is an indication that the prevailing environmental conditions were suitable for the species and that individuals were in good health (Wójcik-Fudalewska & Normant-Saremba, 2016) and can therefore not explain differences between years. There have been some indications that the E. sinensis populations in Europe and America undergo some sort of cyclic population structure, with massive numbers found some years and very few in others, although mechanisms driving these fluctuations are currently unknown (Drotz, Berggren, Lundberg, Lundin, & Proschwitz, 2010;Gollasch et al., 1999;Rudnick et al., 2003;Rudnick, Halat, & Resh, 2000). The main possible reason which has some support basis is that of fluctuations in fresh water wash-out speed in estuaries: years with consecutively low freshwater flows due to drought are thought to be behind the establishment of a breeding E. sinensis population in the Thames, United Kingdom (Gilbey et al., 2008). ...
The Chinese mitten crab is one of the top invasive species in Europe. In Flanders (Belgium), they are associated with river ecosystem degradation, especially the loss of aquatic vegetation and associated ecosystem services. Management measures have therefore been put in place to reduce the number of crabs migrating between the sea and freshwater areas and ultimately control the population. Although we are still long way from the goal, a low‐cost method has been applied to successfully catch migrating crabs. In this article, we outline the design and functioning of the trap. We monitored the population in a lowland river, measured migration speeds and calculated crab densities. With over 1 million crabs caught in 2 years, the trap proved to be very effective. Median anadromous (spring) and catadromous (autumn) migration speeds were 0.69 and 0.96 km day⁻¹, respectively. Anadromous migrating crab density was calculated to be up to 3.20 ind. m⁻² river bed. Resident crab density was calculated to be up to 2.05 ind. m⁻² river bed. We conclude that this trap is a very useful tool for water managers to catch Chinese mitten crabs in rivers and discuss the pathways towards reducing the population and protect the entire freshwater catchment.
... The expected range expansion caused by this novel ecology has already been documented by the recent and widespread occurrence of ovigerous females in the Eastern Baltic Sea (Ojaveer et al. 2007). Similarly, the occurrence of mitten crabs throughout much of the freshwater system of Sweden was hard to explain, invoking long-distance migration of crabs from their North Sea spawning grounds (Drotz et al. 2010). We suspect that these crabs belong to the same physiological type as the crabs investigated by Otto (2012), and are able to complete their larval cycle in the Baltic Sea. ...
The Chinese mitten crab ( Eriocheir sinensis ) is a prominent aquatic invader with substantial negative economic and environmental impacts. The aim of the present study was to re-evaluate the genetic diversity of mitten crabs throughout their native and invaded ranges based on publicly available sequence data, and assess if multiple introductions or rapid adaptation could be responsible for biologically divergent mitten crabs in Northern Europe. We assembled available genetic data of a fragment of the mitochondrial cytochrome c oxidase subunit one gene (COI) for all species of the genus Eriocheir . We applied phylogenetic and population genetic analyses to compare native and invasive populations, and to identify possible source populations. The phylogenetic reconstruction revealed that five COI sequences from Europe, morphologically identified as Chinese mitten crab, actually belong to the Japanese mitten crab ( Eriocheir japonica ), representing the first indication of its presence in European waters. All other COI sequences from Europe could unambiguously be assigned to the Chinese mitten crab. In some Northern German populations of Chinese mitten crabs, genetic diversity was surprisingly high, due to seven unique haplotypes encoding several amino acid substitutions. This diversity may reflect a cryptic introduction from an unsampled native location, or rapid adaptation in the invaded range. Based on the genetic diversity shared between native and introduced range, Feiyunjiang, a tributary of the Yangtze River, emerges as a plausible source population for the original introduction of Chinese mitten crabs to Europe. This study highlights the complex and dynamic invasion processes of mitten crabs in Europe. We urge to further monitor mitten crab invasions using genetic tools.
... It was at first observed occasionally in the Baltic Sea (Ojaveer et al., 2007) and its breeding ecology suggested that no self-sustaining populations could be formed in low salinity waters (Anger, 1991). Today, however, the number of observations reported in Baltic waters has increased and an established population has been described (Drotz et al., 2010; Otto and Brandis, 2011). In our study, the PD map for E. sinensis shows suitable habitats in nearly the entire Baltic Sea (Fig. 3d). ...
... It was at first observed occasionally in the Baltic Sea (Ojaveer et al., 2007) and its breeding ecology suggested that no self-sustaining populations could be formed in low salinity waters (Anger, 1991). Today, however, the number of observations reported in Baltic waters has increased and an established population has been described (Drotz et al., 2010; Otto and Brandis, 2011). In our study, the PD map for E. sinensis shows suitable habitats in nearly the entire Baltic Sea (Fig. 3d). ...
Salinity is an ecological key factor in the life of estuarine and coastal plankton, and hence, also in the biology of meroplanktonic decapod crustacean larvae. Its influence has been documented in all principal aspects of larval biology including survival, development, morphology, the moulting cycle, growth, feeding, metabolism, energy partitioning, and behaviour. In this review, detrimental effects of osmotic stress on decapod larvae are exemplified; and interactions with other environmental variables such as temperature or toxic pollutants, or with intrinsic phenomena such as the moulting cycle are shown. Putative relationships between osmoregulatory patterns and the metabolic response to salinity variation are proposed.
The present paper reports the occurrence of the Chinese mitten crab, Eriocheir sinensis H. Milne Edwards, 1854, in Portugal and thus extends its known southerly distribution for Europe. Available Portuguese data are presented and discussed including a possible new size record for the northeastern Atlantic region.
The present paper reports the occurrence of the Chinese mitten crab, Eriocheir sinensis H. Milne Edwards, 1854, in Portugal and thus extends its known southerly distribution for Europe. Available Portuguese data are presented and discussed including a possible new size record for the northeastern Atlantic region.La presence du Crabe Chinois, Eriocheir sinensis H. Milne Edwards, 1854, est signalee au Portugal, ce qui etend sa distribution en Europe vers le sud. Les donnees portugaises sont fournies et discutees, y compris un possible record de taille pour la region atlantique nord-orientale.
The arrival of the Chinese mitten crab to the San Francisco Bay-San Joaquin Delta (Bay-Delta) ecosystem has been a source of widespread concern. This crab has spread from its native range, in China, to coastal ecosystems throughout Europe and, most recently, into North America. The Chinese mitten crab population in California has exploded within the last decade to cover hundreds of miles of the Bay-Delta and its tributaries. The Chinese mitten crab is a large, catadromous crab, moving from freshwater habitats where it spends its juvenile years to saltwater habitats in order to reproduce. In other countries into which this species has been introduced, the abundance and behavior of the crab has caused detrimental impacts to fisheries and loss of bank stability in areas where it burrows. Through a grant from the Water Resources Center, we set out to examine the ecology, distribution, and economic and ecological impacts of the Chinese mitten crab in the fresh and saline waters of San Francisco's South Bay. The Chinese mitten crab offers excellent opportunities to: 1) study the population dynamics of an invasive species; 2) examine differences and similarities for this organism between its native and new environments; and 3) use research findings to make recommendations for understanding and control of this organism. We surveyed the tributaries and main body of South San Francisco Bay in order to examine the ecology and impacts of the Chinese mitten crab. We studied distribution and abundance of juvenile crabs by establishing 72 monitoring sites throughout the salinity gradient of several major South Bay tributaries. These sites were used in 1995, 1996 and 1999 to collect population and habitat data. Adult crabs in the South Bay were monitored using otter trawls over the same three-year period. Population parameters of mitten crabs, including size and sex ratios, were examined. We quantified habitat preferences of the mitten crab by examining stream characteristics including substrate type, vegetation type, and salinity. Gut contents were analyzed in order to examine dietary habits and dietary shifts with age, and frequent behavioral observations of crabs were made to confirm dietary and habitat preference data. In order to examine impacts to banks and levees, we examined burrowing by juvenile crabs and quantified sediment removal from burrowing by estimating burrow density and sediment removed per burrow. The potential impacts of Chinese mitten crab on two species of freshwater crayfish were studied using a combination of behavioral observations, laboratory experiments and surveys of the commercial crayfish industry. We found mitten crabs to be broadly distributed throughout the freshwater tributaries of the South Bay, with the distribution spreading over the three years we monitored these sites. Adult mitten crabs were also found in the main body of the bay, with gravid (egg-carrying) females appearing between November and May of each year. Juvenile mitten crabs preferred intertidal sections of streams that had banks with high clay content and abundant vegetation overhanging or growing on the banks. Gut content analysis of mitten crabs revealed a high proportion of vegetative matter, with low amounts of invertebrates, regardless of the size of the crab or the habitat from which it was collected. Abundance of Chinese mitten crab also increased over time, as seen by a continuous increase in burrow densities: densities reached a high of 18/ m2 at one site in 1995 and 1996, and densities exceeded 30 burrows/ m2 at two sites in 1999. Densities exceeding 30 burrows/ m2 are considered to be damage-causing levels in other areas into which the crab has been introduced. Research into the impacts of Chinese mitten crabs on crayfish populations produced mixed results: based on behavioral observations, crabs and crayfish in the South Bay were found to co-occur; crayfish industry surveys revealed concern regarding potential competition of crayfish and mitten crabs; and experimental interactions suggested possible habitat competition between adults of crayfish and mitten crabs. We present these findings in coordination with studies occurring in the North Bay, the Delta and throughout California which show that the Chinese mitten crab is quickly spreading throughout all of northern California, and has recently reached southern California through the state's aqueduct system. In addition, the sheer abundance of the crab has created significant impacts on the state's water projects. In particular, efforts to minimize impacts to fish from water project turbines and pumps have been seriously impeded by the crabs clogging these systems during their fall migration. The results of our research include important findings for the spread of the organism, similarities and differences between its ecology here and in its native range, and impacts on physical and biological characteristics of San Francisco Bay. We have shown that the mitten crab population has exploded in the South Bay as well as throughout the Bay-Delta region. The highest densities of mitten crab burrows are currently restricted to intertidal segments of the banks and levees; however, at some locations within these areas, bank slumping and erosion already are significant. We believe that there is cause for concern for impacts on freshwater crayfish, although more research needs to be done to quantify these impacts. Given the widespread distribution, abundance, and lack of specialized predators for the Chinese mitten crab, we believe complete control of this species would be extremely difficult and costly. A more effective strategy will be to focus control in specific regions where the crab is producing costly and damaging effects, such as the fish protection programs at state water projects. State and private parties have discussed commercialization of the mitten crab for consumption here or in Asia, and this option could provide an effective, though controversial, method of control. Our findings suggest that the mitten crab is here to stay as yet another member of San Francisco's evolving non-indigenous communities.