Invasion status and potential impacts of bluegill Lepomis macrochirus Rafinesque, 1819 in the Kariega River, Eastern Cape, South Africa

The impact of alien invasive species is one of the greatest threats to biodiversity globally. All of the major drainages of South Africa are invaded by non-native fishes, yet little information is available on their impact. This thesis focusses on providing a better understanding of the potential impacts of bluegill Lepomis macrochirus Rafinesque, 1819, a species introduced into South Africa from the USA in 1938. The study assesses the distribution, establishment success and feeding ecology of L. macrochirus in an invaded South African River system in order to better understand and document its potential impacts. Specifically; this thesis (1) assesses the distribution and relative abundance of L. macrochirus in the Kariega System of the Eastern Cape, (2) determines the diet of the species in one of the major impoundments of the system, and (3) uses an experimental comparative functional response approach to assess whether this species has heightened predatory capabilities when compared with fishes with which it cooccurs. Ninety-six sites in the Kariega River system were sampled from the headwaters down to the estuary. Small native fish species (Enteromius anoplus and Enteromius pallidus) occurred mostly in the upper reaches, while in the middle and lower reaches, the centrarchid alien largemouth bass Micropterus salmoides and bluegill L. mocrochirus dominated. There was overlap between the centrarchids and introduced banded tilapia Tilapia sparrmanii and southern mouthbrooder Pseudocrenilabrus philander, but never with small-bodied native species. The stomach contents of L. macrochirus were examined during winter and summer and prey were identified to family level. Crustaceans and insects were an important component in their diet, but in summer fish eggs were common. Comparisons of bluegill diet with published literature indicated that there was potential for competition with largemouth bass, banded tilapia and southern mouthbrooder. Feeding experiments were conducted to compare the functional responses of these four species using a common prey item. Banded tilapia had significantly lower attack rates than the other species with no significant difference observed in other species. Bluegill has a similar impact to that of banded tilapia and southern mouthbrooder, but lower than that of largemouth bass. Results of the present study highlight that L. macrochirus introduced into dams will likely result in both upstream and downstream invasion of river systems. It is likely that this species does not, however, have as much of a predatory impact as M. salmoides in that its predatory capacity is relatively reduced and more comparable to South African native cichlids. These results are discussed within the context of invasion success/failure in other regions of southern Africa

Non-Native Black Bass: Potential Conflicts in Fisheries Management

Black bass (Micropterus spp.) are among the most highly sought after recreational fishes around the world, which has resulted in widespread introductions outside of their indigenous ranges. Non-native black bass can, simultaneously, imperil native biodiversity and bring economic benefits to local economies, thus highlighting the paradox of stocking sport fishes. In an effort to disentangle these fundamentally incompatible forces, I systematically reviewed the ecological and economic impacts of non-native black bass, which has not been updated in over 30 years. Considering the constant flux of human-mediated dispersal events, the distribution of the two most stocked species of non-native black bass, Largemouth (M. salmoides) and Smallmouth Bass (M. dolomieu), were reevaluated. Further, I administered a novel broad scale survey of U.S. fisheries biologists assessing current perceptions surrounding the ecological and economic impacts of non-native black bass. My updated distribution represents data from the most recently available sources and has filled a knowledge gap concerning the current range of these species. The establishment success rate between Largemouth Bass (76%) and Smallmouth Bass (22%) differed widely, suggesting that ecological and biological factors influence their distribution. The case studies highlighted within show a global reevaluation of socio-economic values and conservation priorities in relation to the level of risk associated with non-native species. My survey results indicate that non-native black bass are considered economically beneficial in both anthropogenic and natural waters. Contrastingly, non-native black bass were perceived to have significantly more negative ecological impacts in natural waters than in anthropogenic waters. Largemouth Bass, Smallmouth Bass, and Florida Bass (M. floridanus) were perceived to provide the most economic benefits, while Alabama Bass (M. henshalli), Smallmouth Bass, and Spotted Bass (M. punctulatus) were perceived to cause the most ecological imperilment. My findings suggest that habitat may be an important factor to partitioning the conflicting ecological-economic dynamic of non-native black bass. Implications of this study suggest that challenges remain for managers attempting to balance the paradoxical nature of non-native black bass as both a desired sport fish and as a potentially harmful invader

Fusão invasora : hierarquização da hipótese, avaliação experimental e "Framework" para teste e síntese

Orientador : Prof. Dr. Jean Ricardo Simões VituleCo-Orientador : Prof. Dr. André Adrian PadialTese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Biológicas, Programa de Pós-Graduação em Ecologia e Conservação. Defesa: Curitiba, 25/02/2016Inclui referências : f. 117-123;154-162Área de concentraçãoResumo: A introdução de espécies não-nativas possui reconhecido impacto em todos os níveis ecológicos e constitui hoje uma importante ameaça à diversidade biológica nos mais diversos ecossistemas. Com o elevado número de espécies não-nativas nos mais diversos ambientes, é esperado que muitas dessas formem novas interações positivas, facilitando umas as outras de diversas formas e causando então um aumento do impacto dessas e até mesmo acelerando o número de novas invasões. Esse processo foi chamado de fusão invasora. Dada a relevância teórica e prática da hipótese de fusão invasora, se faz necessária uma síntese das evidências existentes. Sendo assim, através do método de hierarquização de hipóteses foi realizada uma divisão da hipótese em sub-hipóteses mais facilmente testáveis. A maioria das sub-hipóteses apresentou um domínio de evidências a favor da hipótese de fusão invasora. Adicionalmente, ficou clara a escassez de estudos que avaliem experimentalmente o impacto sinérgico entre espécies não-nativas resultante de interações positivas entre essas. Aliando isso ao fato de que diversas espécies não-nativas começaram a ser registradas nas últimas décadas na planície do Alto rio Paraná, o impacto sinérgico de três espécies não-nativas foi avaliado através de um experimento em mesocosmos. Relações de facilitação entre as três espécies analisadas leva a crer que essas possam fazer parte de um processo de fusão invasora apesar de não ter sido encontrado impacto sinérgico entre elas. Apesar disso, alterações populacionais e ecossistêmicas foram encontradas, ressaltando a importância de entender como espécies não-nativas interagem no ambiente invadido. Após análise dos estudos sobre a hipótese de fusão invasora, de críticas e debates sobre essa, percebe-se a necessidade de um melhor detalhamento e distinção dos principais aspectos da hipótese. Para o processo de fusão invasora, especial atenção deve ser dada às espécies generalistas, facilmente engajadas em interações mutualísticas; engenheiras ecossistêmicas por causarem grandes mudanças que desestabilizam a comunidade nativa facilitando a chegada de outras não-nativas; e predadoras de topo que podem complementar o impacto uma das outras. Por fim foi criado um "framework" para o teste da hipótese, que distingue níveis de suporte de acordo com o tipo de evidência encontrado. Palavras-chave: espécies exóticas, interações interespecíficas, síntese, resistência biótica, invasibilidade.Abstract: Non-native species introduction has widely known impacts across all levels of biological organization and therefore is an important threat to biodiversity. With the large number of non-native species found in nearly all ecosystems it is expected that new positive interactions arise among them, facilitating one another in various ways, increasing their impacts and/or accelerating the number of new successful introductions. This process has been called invasional meltdown. Given the theoretical and practical relevance of the invasional meltdown hypothesis it is now necessary to synthetize existing evidence. To do so, we used the hierarchy of hypotheses method to separate the broad definition into more testable sub-hypotheses. The majority of sub-hypotheses selected had a dominance of evidence supporting the invasional meltdown hypothesis. It is clear that there is scarce evidence experimentally testing the synergistic impact of non-natives resulting from their positive interaction. Additionally, several non-native species have been detected in the last decades in the Alto rio Paraná floodplain, so we tested through a mesocosm experiment, the synergistic impact of three non-native species now occurring in the region. We found several ways through which these three species facilitate each other. Therefore these species might be part of an invasional meltdown process even though no synergistic impact was found among them. We also detected population and ecosystem alterations due to species invasions, which strengthen the importance of understanding how non-native species interact in the invaded range. After analyzing published evidence for the invasional meltdown hypothesis, critics and debates, it is necessary to distinguish main aspects of the hypothesis for a better understanding of the process, what will allow more accurate tests and detection of the problem. In regard to the invasional meltdown hypothesis, special attention should be given to generalist species which are more prone to form new mutualistic interactions; ecosystem engineers which might cause severe changes to the environment, disrupting the native community and facilitating the establishment of other non-natives; and top predators which can have synergistic impact upon shared native preys. At last a framework for testing the invasional meltdown hypothesis was created distinguishing level of support according to type of evidence found. Keywords: exotic species, interspecific interactions, synthesis, biotic resistance, invisibility

Ecosystem modelling in the Eastern Mediterranean Sea : the cumulative impact of alien species, fishing and climate change on the Israeli marine ecosystem

Firstly, I reviewed modelling approaches that were used to assess the impact of invasive alien species (IAS) in aquatic ecosystems. According to the review, multispecies/ecosystem mechanistic models dominated the applications, with dynamic and non-spatial models being the most prevalent. Most of the models included an additional human stressor, mainly fisheries, climate change and/or nutrient loading. I summarised the main features of these applications and analysed their capabilities and limitations. Based on my conclusions, I reflected on future directions of development and applications of suitable modelling tools. The review showed that the Ecopath with Ecosim (EwE) modelling approach was frequently used to assess the impacts of already established IAS and highlighted its capabilities to forecast existing, emerging and potential new IAS. As a second step, I developed two static Ecopath ecosystem models using the EwE approach and representing the food web of the Israeli Mediterranean coast in 1990s and 2010s. I characterized the structure and functioning of the ecosystem and assessed past and current impacts of IAS and fishing. I then used the time-dynamic Ecosim module of EwE to fit the 1990s model to available time series of observations between both periods and to explore the historical dynamics of the ecosystem considering the effects of IAS, fishing dynamics and sea warming. Finally, the time-dynamic ecosystem model was used to analyse alternative future simulations of ecosystem change. Particularly, and after interacting with key stakeholders, I assessed the future effects of a new set of fishing regulations currently being implemented in Israel, future changes in sea temperature following IPCC (Intergovernmental Panel on Climate Change) scenario projections and the potential increases in IAS biomass. I investigated the impacts of the stressors separately, and then I combined them to evaluate their cumulative effects. Results from the static Ecopath models highlighted that the Israeli marine ecosystem, despite productivity differences, shared some structural and functional traits with other Mediterranean ecosystems such as the dominance of the pelagic domain in term of flows, the important role of detritus through low trophic levels and the importance of the benthic-pelagic coupling. In both time periods investigated, the same keystone groups were identified with the exception of European hake in 2010s, which showed a decline in its keystone role. This may indicate that hake lost its ecological role due to population declines. Most of the functional groups identified as keystone species were previously identified as keystones in other Mediterranean ecosystems, such as dolphins, large pelagic fishes, sharks and squids. The temporal dynamic Ecosim model indicated that trophic interactions, ocean warming and fishing were important drivers of the ecosystem dynamics. In general, temporal biomass trends revealed that native demersal predators and native medium trophic level fishes largely declined over time, while an increase over time of alien species was observed. Results from ecological indicators suggested a degradation pattern of the ecosystem over time. Future scenarios using the temporal dynamic Ecosim model showed overall potential benefits of fishing effort reductions in the future, and detrimental impacts of increasing sea temperature and increasing biomass of alien species. Cumulative scenarios highlighted that the beneficial effects of fisheries reduction could be dampened by the impact of increasing sea temperature and alien species when acting together. These results support the need for reducing local and regional stressors, such as fishing and biological invasions, to retain marine ecosystems within a “safe operating space” and ensure ecosystem resilience in an ongoing warming and impacted sea.Los ecosistemas marinos del Mediterráneo oriental han sufrido cambios ecológicos importantes debido a múltiples presiones antropogénicas, incluido el impacto de especies invasoras, la sobrepesca y el calentamiento del mar. En primer lugar, he revisado los modelos que se han utilizado para evaluar el impacto de las especies invasoras en los ecosistemas acuáticos. De acuerdo con esta revisión, predominan los modelos mecanísticos de carácter multiespecífico/ecosistémico, siendo los modelos dinámicos y no espaciales los más frecuentes. La mayoría de los modelos incluyen un impacto antropogénico adicional, principalmente la pesca, el cambio climático y el aporte de nutrientes. Además, he resumido las principales características de estos modelos y he analizado sus capacidades y limitaciones. En base a las conclusiones de esta revisión, se han mostrado posibles direcciones para futuros desarrollos de los modelos y la aplicación de modelos adecuados. En esta revisión, he observado que el modelo Ecopath with Ecosim (EwE) ha sido utilizado frecuentemente para evaluar los impactos de las especies invasoras ya establecidas. Además, la revisión ha destacado las capacidades de EwE de pronosticar los futuros impactos de las especies invasoras establecidas, emergentes y potenciales. Otras revisiones disponibles en la literatura han demostrado las capacidades de EwE para evaluar los impactos de la pesca y el cambio climático. Por lo tanto, he desarrollado dos modelos estáticos Ecopath que representan la red trófica de la costa Mediterránea de Israel en los años 1990 y 2010 para caracterizar la estructura y funcionamiento del ecosistema y evaluar los impactos de las especies invasoras y la pesca en el pasado y en el presente. Después he utilizado el módulo dinámico-temporal Ecosim para ajustar el modelo de 1990 a series temporales de datos disponibles entre ambos periodos y para explorar la dinámica histórica del ecosistema considerando el efecto de las especies invasoras, la dinámica de la flota pesquera y el calentamiento del mar. Finalmente, el módulo dinámico-temporal ha sido utilizado para realizar simulaciones futuras de cambios en el ecosistema. En particular, he evaluado los efectos de un nuevo conjunto de regulaciones de pesca que se están implementando actualmente en Israel, futuros cambios en la temperatura del mar siguiendo las proyecciones del Panel Intergubernamental sobre el Cambio Climático (IPCC por sus siglas en inglés) y posibles aumentos de la biomasa de las especies invasoras. Primero he investigado los diferentes impactos por separado y, luego, los he combinado para evaluar sus efectos acumulativos. Los resultados de los modelos estáticos Ecopath han destacado que el ecosistema marino israelí, a pesar de un patrón de productividad diferente, comparte algunas características estructurales y funcionales con otros ecosistemas mediterráneos como el dominio del hábitat pelágico en términos de flujos tróficos, el importante papel del detritus a través de niveles tróficos bajos y la importancia del acoplamiento bentónicopelágico. Los mismos grupos funcionales clave fueron identificados en ambos periodos investigados, a excepción de la merluza en 2010, lo que puede indicar que la merluza ha perdido su papel ecológico debido al declive de su población. La mayoría de los grupos funcionales identificados como especies clave ya han sido identificados previamente como tales en otros ecosistemas mediterráneos como por ejemplo los delfines, los grandes peces pelágicos, los tiburones y los calamares. El módulo dinámico-temporal Ecosim indicó que las interacciones tróficas, el aumento de la temperatura del mar y la pesca jugaron un papel clave en la dinámica del ecosistema. En general, las tendencias temporales de la biomasa revelaron que los depredadores demersales nativos (por ejemplo, la merluza) y los peces demersal nativos de nivel trófico medio (por ejemplo, los salmonetes) disminuyeron en gran medida con el tiempo, mientras que se observó un aumento de las especies invasoras con el tiempo. Los resultados de los indicadores ecológicos sugirieron un patrón de degradación del ecosistema con el tiempo. Los escenarios futuros utilizando el módulo dinámico-temporal Ecosim mostraron los beneficios potenciales generales de las reducciones del esfuerzo pesquero y los impactos negativos del aumento de la temperatura del mar y el aumento de la biomasa de las especies invasoras. Los escenarios acumulativos resaltaron que los efectos beneficiosos de la reducción de la pesca pueden verse disminuidos por el impacto del aumento de la temperatura del mar y las especies invasoras cuando actúan al mismo tiempo. Estos resultados respaldan la necesidad de reducir los impactos antropogénicos locales y regionales como la pesca y las especies invasoras, para mantener los ecosistemas marinos dentro de un “espacio operativo seguro (SOS por sus siglas en inglés)” y promover la resiliencia de los ecosistemas en un mar en continuo calentamiento y altamente impactado.Els ecosistemes marins de la Mediterrànea oriental han patit canvis ecológics importants a causa de múltiples pressions antropogèniques, inclòs l’impacte d’especies invasores, la sobrepesca i el calentament del mar. En primer lloc, he revisat els models que s’han utilitzat per avaluar l’impacte de les espècies invasores en ecosistemes aquàtics. D’acord amb aquesta revisió, predominen els models mecanístics de caràcter multiespecífic/ecosistèmic, sent els models dinàmics i no espacials els més freqüents. La majoria dels models inclouen un impacte antropogènic adicional, principalment la pesca, el canvi climàtic i l’aport de nutrients. A més, he resumit les principals característiques d’aquest models i he analitzat les seves capacitats i limitacions. En base a les conclusions d’aquesta revisió, s’han exposat possibles direccions per futurs desenvolupaments dels models i l’aplicació de models adecuats. En aquesta revisió he observat que el model Ecopath with Ecosim (EwE) ha estat utilitzat freqüentment per avaluar els impactes de les espècies invasores ja establertes. A més, la revisió ha destacat les capacitats d’EwE de pronosticar els futurs impactes de les espècies establertes, emergents i potencials. Altres revisions disponibles a la literatura han demostrat les capacitats d’EwE per avaluar els impactes de la pesca i el canvi climàtic. Per tant, he desencolupat dos models estàtics Ecopath que representen la xarxa tròfica de la costa Mediterrànea d’Israel en els anys 1990 y 2010 per caracteritzar l’estructura i funcionament de l’ecosistema i avaluar els impactes de les espècies invasores i la pesca en el passat i el present. Després he utilitzat el mòdul dinàmic-temporal per ajustar el model de 1990 a sèries temporals de dades disponibles considerant l’efecte de les espècies invasores, la dinàmica de la flota pesquera i l’escalfament del mar. Finalment, el mòdul dinamic-temporal ha estat utilitzat per realitzar simulacions futures de canvis en l’ecosistema. En particular, he avaluat els efectes d’un nou conjunt de regulacions de pesca que s’estan implementant actualment a Israel, canvis en la temperatura del mar seguint les projeccions del panell intergovernamental sobre el Canvi Climàtic (IPCC per les seves sigles en anglès) i possibles augments de la biomass de les espècies invasores. Primer he investigat els diferents impactes per separat i, després, els he combinat per avaluar els seus efectes acumulatius. Els resultats dels models estàtics Ecopath han destacat que l’ecostema marí d’Israel, malgrat un patró de productivitat diferent, comparteix algunes característiques estructurals i de funcionals amd altres ecosistemes marins mediterrànis com el domini de l’hàbitat pelàgic en termes de fluxes tròfics, l’important paper del detritus a través de nivells tròfics baixos i la importància de l’acoplament bentònic-pelàgic. Els mateixos grups funcionals clau van ser identificats en els dos períodes investigats, a excepció del lluç en el 2010, que pot indicar que el lluç ha perdut el seus paper ecològic a causa del declivi de la seva població. La majoria del grups funcionals identificats com a espècies claus ja han estat identificats com a tals en altres ecosistemes mediterranis com ara els dofins, els gran peixos pelàgics, els taurons i els calamars. El mòdul dinàmic-temporal Ecosim ha indicat que les interaccions tròfiques, l’augment de la temperatura del mar i la pesca van jugar un paper clau en la dinàmic de l’ecosistema. En general, les tendències temporals de la biomasa van revelar que els depredadors demersals natius (per exemple, el lluç) i els peixos dersals natius de nivell tròfic mitjà (per exemple, els rogers) van disminuir en gran mesura amb el temps, mentre que es va observar un augment de les espècies invasores amb el temps. Els resultats dels indicadors ecològics van suggerir un patrò de degradació de l’ecosistema amb el temps. Els escenaris futurs van mostrar els beneficis potencials generals de les reduccions de l’esforç pesquer i els impactes negatius de l’augment de la temperatura del mar i ’augment de la biomasa de les espècies invasores. Els escenaris acumulatius van ressaltar que els efectes beneficiosos de la reducció de la pesca poden ser reduïts per l’impacte de l’augment de la temperatura del mar i les espècies invasores quan actuen al mateix temps. Aquests resultats recolzen la necessitat de reduir els impactes antropogènics locals i regionals com la pesca i les espècies invasores, per mantenir els ecosistems marins dins d’un “espai operatiu segur (SOS per les seves sigles en anglès)” i promoure la resiliència dels ecosistemes en un mar en continu escalfament i altament impactat