Trophic Interactions and Impacts of Non-indigenous Species in Baltic Sea Coastal Ecosystems

Translocation of non-indigenous species is a global threat to the structure and functioning of coastal ecosystems. Coastal ecosystems and estuaries are particularly prone for invasions due to impacts from a variety of anthropogenic stressors and frequent propagule pressure, notably from shipping. In addition, species poor environments, especially when already impacted by multiple anthropogenic stressors, such as the Baltic Sea, are thought to be particularly susceptible to invasions. In the Baltic Sea, to date more than 130 non-indigenous species have been reported and about 80 have been able to become established. Few have become invasive, spreading rapidly and/or begun to impact the native ecosystem. In this thesis the aim was to study how invasive benthic non-indigenous species, specifically the Harris mud crab (Rhithropanopeus harrisii) and round goby (Neogobius melanostomus) have settled in their new environment, how they have affected the ecosystem and how this information of the species can in future be used in management practices (e.g., risk assessments) in the Baltic Sea. The results show that the interactions between the two non-indigenous species and the environment are highly complex and may involve both generic and strictly context-specific components. The native predators and parasites in the area have begun to exploit the new species, although they are currently unable to control the growing mud crab and round goby populations. Furthermore, the FISK (Fish Invasiveness Scoring Kit) risk assessment exercise for the southern coastal areas of Finland showed that many non-indigenous fish species, some of which have already established, do have potential for becoming pests in the area. However, the continuously changing environment (incl. due to climate change) modi- fies both the non-indigenous and invasive biota in the area as well as may alter the nature and magnitude of ecosystem changes caused by the non-indigenous species. The infor- mation gathered in the thesis can be used in further risk assessments and aiding future management decisions.Vieraslajeja pidetään yhtenä suurimmista uhkista rannikkoekosysteemien rakenteelle ja toiminnalle. Rannikot ovat erityisen herkkiä vieraslajeille koska ne ovat alttiina myös muille ihmistoiminnasta aiheutuville paineille ja niihin päätyy paljon vieraslajeja, erityisesti laivaliikenteen mukana. Lisäksi, on ajateltu, että vähälajiset alueet, erityisesti kun ne ovat jo ennestään muiden paineiden alla kuten Itämeri, saattavat olla erityisen herkkiä uusille vieraslajeille. Itämerellä on tähän mennessä havaittu 130 vierasperäistä lajia ja niistä noin 80 on asettunut. Muutama lajeista on arvioitu haittaa aiheuttaviksi, joko nopean lisääntymisen vuoksi ja/tai koska niillä on vaikutuksia ekosysteemien rakenteeseen tai toimintaan. Tässä väitöskirjassa tavoitteena oli tutkia miten kaksi mahdollisesti haitallista lajia, mustatäplätokko (Neogobius melanostomus) ja liejutaskurapu (Rhithropanopeus harrisii) ovat asettuneet uuteen ympäristöönsä ja millaisia vaikutuksia niillä on. Lisäksi väitöstutkimuksessa tarkastellaan, miten näitä tietoja voidaan käyttää päätöksenteon tukena (esim. riskinarvioinneissa) Itämerellä. Tuloksista käy ilmi, että lajien vuorovaikutussuhteet alkuperäislajiston kanssa ovat sekä monimutkaisia että ajallisesti ja paikallisesti vaihtelevia. Osa pedoista ja loisista ovat alkaneet hyödyntää näitä uusia lajeja, vaikka ne eivät vielä kykene hallitsemaan niiden populaatioiden kasvua. Lisäksi, FISK (Fish Invasiveness Scoring Kit) riskinarviointi Etelä-Suomen rannikkoalueilla osoittaa, että moni alueelle asettunut vieraskalalaji saattaa tulevaisuudessa muuttua haittaa aiheuttavaksi vaikka toistaiseksi haitallisia lajeja on vähän. Ympäristön jatkuva muutos (mukaan lukien ilmastonmuutoksen vaikutukset) vaikuttaa myös vieraslajeihin ja alkuperäislajeihin sekä muuttaa niiden keskinäisiä vuorovaikutussuhteita ja mahdollisesti voimistaa vieraslajien vaikutuksia ekosysteemissä. Väitöskirjassa kerättyä tietoa voidaan käyttää tulevissa vieraslajien riskinarvioinneissa sekä päätöksenteon tukena ympäristöhallinnossa

Citizen science provides added value in the monitoring for coastal non-indigenous species

Continuous and comprehensive monitoring is one of the most important practices to trace changes in the state of the environment and target management efforts. Yet, governmental resources are often insufficient for monitoring all required environmental parameters, and therefore authorities have started to utilize citizen observations to supplement and increase the scale of monitoring. The aims of the present study were to show the potential of citizen science in environmental monitoring by utilising citizen observations of the non-indigenous Harris mud crab Rhithropanopeus harrisii in Finnish waters, where coastal monitoring is insufficient to estimate the distribution and spread of non-indigenous species. Harris mud crab has shown measurable impact locally and is considered invasive. For reporting the status of invasions to national and European authorities and planning for potential eradication efforts, up to date knowledge on NIS ranges are needed. Citizen observations on the species were collected from the first observation onwards between 2009 and 2018, at first via email and later through an active citizen observation web portal (Invasive Alien Species Portal). The outcomes of the study indicate that species-specific citizen observations can be a beneficial addition to supplement national monitoring programs to fulfil legislative reporting requirements and to target potential management. Recognizable species and geographical areas with low biodiversity provide a good opportunity to utilize citizen observations. Moreover, citizen observations may enable distribution assessments for certain species that would otherwise require excessive resources and sampling efforts. Highlights • Citizen observations are cost-efficient addition to routine monitoring. • Citizen science can provide presence data on dist inctly recognizable species. • Citizen science provides important information to target management actions. • Citizen science enables estimates for species distribution

Infection rates and prevalence of metazoan parasites of the non-native round goby (Neogobius melanostomus) in the Baltic Sea

Studies in the Baltic Sea have identified over 30 parasite taxa infecting the invasive round goby (Neogobius melanostomus (Pallas, 1814). In this study, we aimed at comparing parasite assemblages and infection rates (prevalence and intensity) in different populations across the invasive range in the Baltic Sea (Denmark, Lithuania, Estonia and Finland). Infection rates were 56-60% across all locations except Lithuania (28%). However, the parasite assemblages in the sampled populations were dissimilar, each location having unique parasites. In addition, many of the parasites were generalists commonly infecting native fish species. Based on the results of this study and those previously conducted in the Baltic Sea, the round goby has not retained parasites from its area of origin, but instead has been successively colonized by native generalist parasites. Although variable, overall parasite richness is still quite low around the Baltic compared to the native areas (34 vs 71 taxa, respectively). Also, prevalence and mean infection intensities in the Baltic Sea are significantly lower than in the native areas. Therefore, the invasion success of the round goby in the Baltic Sea can at least partly be attributed to enemy release, in this case shedding a significant proportion of their native parasite load.Peer reviewe

A taste for aliens: contribution of a novel prey item to native fishes’ diet

Non-indigenous species (NIS) can alter food web structure and function in many ways. While the predatory and competitive roles of NIS in aquatic environments are commonly studied, their role as a prey item for native predators is often overlooked. As the northern Baltic Sea lacks native crabs, the omnivorous estuarine Harris mud crab (Rhithropanopeus harrisii) is a novel invader to the system and provides an opportunity to observe how the species enters the prey field of predatory fish. In fall 2013, 1185 stomachs from 17 fish species were dissected and analyzed for the presence of R. harrisii. Fishermen had previously reported finding crabs mostly in the stomachs of perch (Perca fluviatilis), a frequent catch in recreational and commercial fisheries, but our study also found large numbers of crabs in four-horned sculpins (Myoxocephalus quadricornis) and small numbers in other species’ stomachs (Rutilus rutilus, Leuciscus ide, Gymnocephalus cernuus, and Blicca bjoerkna). In the study area occupied by R. harrisii, four-horned sculpins were the most frequent predator, with 83% having at least one crab in their stomach. In comparison, 7% of perch and roach had consumed R. harrisii. Most crabs eaten were 10–12 mm (carapace width), despite broader size range available (1–26 mm). Predation on R. harrisii in this system may be limited by the predators’ gape size (i.e., physical feeding restriction). These results highlight the need to understand the role of novel invasive species as prey items for native species, ultimately increase understanding of whether native predators can control NIS populations.KeywordsNon-indigenous species Novel invasion Predation control Food web Baltic Sea Rhithropanopeus harrisii </div

A taste for aliens : contribution of a novel prey item to native fishes’ diet

Non-indigenous species (NIS) can alter food web structure and function in many ways. While the predatory and competitive roles of NIS in aquatic environments are commonly studied, their role as a prey item for native predators is often overlooked. As the northern Baltic Sea lacks native crabs, the omnivorous estuarine Harris mud crab (Rhithropanopeus harrisii) is a novel invader to the system and provides an opportunity to observe how the species enters the prey field of predatory fish. In fall 2013, 1185 stomachs from 17 fish species were dissected and analyzed for the presence of R. harrisii. Fishermen had previously reported finding crabs mostly in the stomachs of perch (Perca fluviatilis), a frequent catch in recreational and commercial fisheries, but our study also found large numbers of crabs in four-horned sculpins (Myoxocephalus quadricornis) and small numbers in other species’ stomachs (Rutilus rutilus, Leuciscus ide, Gymnocephalus cernuus, and Blicca bjoerkna). In the study area occupied by R. harrisii, four-horned sculpins were the most frequent predator, with 83% having at least one crab in their stomach. In comparison, 7% of perch and roach had consumed R. harrisii. Most crabs eaten were 10–12 mm (carapace width), despite broader size range available (1–26 mm). Predation on R. harrisii in this system may be limited by the predators’ gape size (i.e., physical feeding restriction). These results highlight the need to understand the role of novel invasive species as prey items for native species, ultimately increase understanding of whether native predators can control NIS populations.peerReviewe

Merialueemme vieraslajien seurannan, varhaisvaroitus-järjestelmän (VVJ) ja riskin-arvioinnin kehittäminen

Liitteessä 1 Suomessa (Itämeressä) ns. vakiintuneet vieraslajit (useammin kuin kerran havaitut). VISEVARIS-projektin yhteydessä toimineen työryhmän ehdottamat uudet/muutetut suomenkieliset lajinimet lihavoitu. (Työryhmän vetäjänä toimi Erkki Leppäkoski).VISEVARIS-hankkeen tavoitteena oli kehittää rannikkovesiemme vieraslajien seuranta- ja varhaisvaroitusjärjestelmä (VVJ), mihin kuuluu mm. tietoisuuden lisääminen, vieraslajien aikainen havainnointi, tiedonkulun nopea välittäminen haitallisten lajien havaitsemisen jälkeen sekä kansalaisten valistaminen lajien levittämisen estämiseksi. Hankkeessa tutkittiin miltä osin ja miksi nykyseuranta ei pysty havaitsemaan uusia vieraslajeja, etsittiin tehokkaampia menetelmiä vieraslajien havaitsemiseksi ja niiden elinympäristöjen ja alueiden kartoittamiseksi, selvitettiin ja kuvattiin merialueemme keskeiset biologiset seurannat sekä niiden tuottama tieto tavattujen vieraslajien levinneisyydestä ja runsaudesta. Työssä todettiin, etteivät seurannat tavoita suurinta osaa nykyisistäkään vieraslajeista. Havaituista lajeista vain parista saadaan riittävä kuva runsauden ja levinneisyyden suhteen. Matalat rannikkovedet ovat heikoimmin seuratut elinympäristöt. Niiden seurantaa pitäisi lisätä. Hankkeessa tuotettiin ehdotus tehostetun seurannan toteuttamisesta, sen keskittämisestä eri elinympäristöihin sekä velvoiteseurannan toteuttamisesta satamissa. Hanke tuotti nettipohjaisen tunnistus-oppaan suurimmasta osasta Suomen merialueella esiintyvistä ja mahdollisesti tänne saapuvista vieraslajeista helpottamaan niiden havaitsemista ja tunnistamista. Hankkeessa selvitettiin myös vieraslajien riskinarviointiin tarjolla olevia kansainvälisiä työkaluja, joista testattaviksi valittiin makeanveden selkärangattomille kehitetty Fi-ISK ja kaloille käytetty FISK riskinarviointi-työkalu. Niiden avulla saadaan numeerisia arvoja eri lajien haitallisuudelle, mikä auttaa ryhmittelemään vieraslajeja niiden torjunnan kannalta. Kehittämällä työkaluja paremmin murtovesiolosuhteet huomioiviksi riskinarviointeja voidaan toteuttaa Itämeren alueella. Varhais-varoitus- ja informaatiojärjestelmän kehittämiseen tuotetuista osista voidaan rakentaa raamiversio, jonka kehysten sisälle tarvittava lisätieto voidaan helposti koota. Hanke auttaa kehittämään ja monipuolistamaan nykyisiä seurantoja ottamaan huomioon myös vieraslajit. Suomen kansallinen VVJ voi toimia esimerkkinä muille Itämeren maille ja se voi toimia yhteydenpitoväylänä Itämeren valtioiden kesken. Hankkeessa kehitetyllä nettilomakkeella parannetaan vieraslajihavaintojen ilmoittamismahdollisuuksia. Lomakkeen avulla niin tutkijat, konsultit, hallintoviranomaiset kuin kansalaisetkin voivat helposti ilmoittaa havaitsemansa vieraslajit sekä tarkistaa jo tehdyt vieraslajiilmoitukset. Hankkeessa saatuja tuloksia hyödynnetään EU:n meristrategia-direktiivin hyvän tilan indikaattoreita kehitettäessä sekä direktiivin toimeenpanoa tukevien seurantojen kehityksessä. Hankkeen aktiviteettien ansiosta monen vieraslajin havainnot moninkertaistuivat ja levinneisyys osoittautui oletettua laajemmaksi.Maa- ja metsätalousministeri

Twenty five years of invasion: management of the round goby Neogobius melanostomus in the Baltic Sea

The round goby, Neogobius melanostomus (Pallas, 1814), is one of the most invasive non-indigenous species in the Baltic Sea. It dominates coastal fisheries in some localities and is frequently found in offshore pelagic catches. This paper identifies management issues and suggests actions to be considered for post-invasion management. Priority should be given to the establishment of a coordinated pan-Baltic monitoring programme and associated data storage and exchange, as well as the compilation of landing statistics of the round goby in commercial and recreational fisheries. While eradication is unrealistic, population control that leads to minimising the risk of transfer to yet uncolonised areas in the Baltic Sea and adjacent waterbodies is feasible. This should comprise the requirement that the species be landed in commercial fishery bycatch, the management of ships’ ballast water and sediments, and hull fouling of inland and sea-going vessels, including recreational boats. Extensive involvement of stakeholders is crucial at all phases of the management process

Marine invasive alien species in Europe: 9 years after the IAS Regulation

Biological invasions, resulting from human activities, exert substantial impacts on ecosystems worldwide. This review focuses on marine invasive alien species (IAS) in Europe, examining the current state, proposing strategies to address the problem, and offering recommendations for enhanced management. Effective management of biological invasions relies on accessible, accurate data to inform decision-making. Information systems such as the European Alien Species Information Network (EASIN), Aquatic Non-Indigenous and Cryptogenic Species (AquaNIS), and World Register of Introduced Marine Species (WriMS) provide comprehensive databases on IAS, but their sustainability requires long-term maintenance, continuous updates, and support. Most countries lack specific monitoring programs for marine IAS, and standardization and improvement of monitoring methods are needed. Port monitoring plays a vital role in the early detection of new arrivals, and recent advancements in molecular techniques show promise for effective IAS monitoring. Risk screening tools are commonly employed to rank taxa based on their invasiveness potential in European regions, but variations in protocols can yield inconsistent results. European impact assessments highlight resource competition, novel habitat creation, and predation as primary mechanisms for negative impacts on biodiversity, while the creation of novel habitats represents a key mechanism for positive impacts. Preventing IAS introductions is critical, and measures such as ballast water treatment systems are implemented to reduce the likelihood of marine introductions. However, understanding introduction pathways remains uncertain for many IAS. Eradication and control efforts for marine IAS have limited success, emphasizing the need for enhanced biosecurity measures. Climate change, especially ocean warming, can intensify IAS impacts on native species and ecosystems. In climate change hotspots, some tropical aliens may, however, compensate for the loss of thermally sensitive natives with similar traits. Therefore, it is imperative to consider the interactions between climate change and IAS in developing effective management and conservation strategies. Enhancing IAS management in Europe entails i) securing adequate funding, ii) expanding the list of IAS of Union Concern to adequately cover marine invasions, iii) learning from countries with successful biosecurity practices, iv) sustaining information systems, v) improving monitoring and early warning systems with innovative technologies, vi) enhancing prediction models, vii) conducting integrated impact assessments and mapping cumulative IAS impacts, and vii) considering the potential benefits of IAS in ecosystem functioning and services