Introduction, spread and establishment of the invasive clam "Corbicula" spp. in Switzerland

Invasive species are of great concern in conservation biology, in economy and as well as in human health. River and lakes are vulnerable ecosystems and are prone to human-caused introductions of non-indigenous species. Research on the ecology of invasive species, their impact on native communities and the introduction pathways is needed to manage these invasive species and to prevent further introductions. The present thesis concentrates on aquatic invasive invertebrate species and documents the spread of the Asian clam Corbicula spp. into Switzerland. In particular, we focused on Corbicula fluminea and examined its ecological preference, population structure and dispersal in the river Rhine. Furthermore, we analysed the clam’s and other non-indigenous molluscs’ possible impact on the native biodiversity in a sandy flat in Lake Neuchâtel. A literature survey about the influence of invasive non-indigenous species on the biodiversity in the river Rhine documented great changes in river morphology, water quality and species composition during the last century. River engineering, pollution and the opening of canals connecting formerly separated river systems, allowed the invasion of many new species. Some of them reached extraordinary densities and hampered the development of native taxa. Many typically riverine species were replaced by large numbers of euryoecious and non-indigenous species. Competition for food and space, the hosting of parasites and intraguild predation were the main biological mechanisms underlying the alteration of the river community. Most studies on invasive species showed negative correlations between introduced invasive species and native biodiversity but experimental evidence is so far lacking. The Asian clam C. fluminea has been introduced in the Lower Rhine with ballast water of cargo ships in the second half of the 1980ties and was first recorded in Basel, Switzerland, in 1995. There, the clam established a well-structured population. It occurred initially in the internationally navigable section of the river Rhine and in the Canal de Huningue, which obtains water containing clam larvae from the river Rhine. Our field survey showed that the clam preferred slowly flowing, shallow water sites with fine-grained sediment, mainly sand. A substratum-choice experiment in the river Rhine confirmed the empirical evidence. In spring 2011, there is still no evidence that the clam has colonized any tributaries of the Rhine in the region of Basel. However, in 2003, C. fluminea passed a weir and was found 22 km upstream of Basel where cargo shipping is absent. In the same year, records were made in Lake Constance and in Lake Neuchâtel and subsequently in other Swiss lowland lakes. Today, their interconnecting rivers have not yet been colonized apart from some river sections near lake outlets and the river Aare between Aarau and its confluence with the river Rhine. We present evidence for separate introductions of an identical haplotype of C. fluminea into five lakes in Switzerland based on mitochondrial DNA-sequences of the COI in specimens sampled. This indicates passive dispersal of the clam by human activities and/or waterfowl. All but one of the 72 genetically analysed individuals were assigned to a single haplotype of C. fluminea. A second haplotype belonging to the sister species Corbicula fluminalis was found only in the river Rhine near Basel. Recent records of specimens which were not genetically analysed all showed the shell morphology of C. fluminea, confirming the dominance of this clam in Swiss rivers and lakes. Passive dispersal by waterfowl, recreational boating and other human activities may facilitate the further spread of C. fluminea in Switzerland. However, the clam might be less successful in colonizing rivers with rapid current, which might be important refuges for native species. We investigated a sandy flat in Lake Neuchâtel using SCUBA diving to assess the abundance of macroinvertebrate species, and to analyse the impact of non-indigenous mollusc species (C. fluminea, Dreissena polymorpha, Potamopyrgus antipodarum and Lithoglyphus naticoides) on the native macroinvertebrate community. The non-indigenous molluscs dominated the sand flat in numbers and influenced the composition and diversity of native macroinvertebrates, mostly by transforming the sandy substratum into a partly hard substratum habitat. Differences observed in community composition between shallow (< 3.5 m) and deep sites (≥ 5 m) resulted to a certain extent from the reduced abundance of D. polymorpha at shallow sites most probably due to depth-selective feeding of ducks. A shell decay study showed that the shells of C. fluminea and D. polymorpha persist for a longer period in the sediment than those of native molluscs. Therefore, shells of these non-indigenous molluscs have a long-lasting impact through modification of sandy habitat. Several native taxa benefit from such ecosystem engineering, but for other taxa with more specific habitat requirements it might be harmful. In Lake Neuchâtel, high densities of C. fluminea negatively influenced the abundance of sand preferring native taxa. Negative impacts of C. fluminea in industrial facilities such as clogging of water pipes along the river Rhine are also known. Consequently, we recommend classifying C. fluminea as an invasive species in Switzerland and further monitoring and studying this clam

The management of coral reef resource systems

Coral reefs, Resource management, Conferences

Linking Local Knowledge & Community Science in Support of Coastal Marine Stewardship

In the last two decades, there has been a shift towards more integrated, ecosystem-based approaches to marine management, including fisheries. At the same time, there have been calls for greater inclusion of diverse perspectives in conservation science and practice. For these reasons, there is renewed interest in the integration of indigenous and local knowledge into science, management, and environmental decision making. Despite these developments, local knowledge often is poorly integrated or treated as something of lesser value than knowledge generated or curated by professional researchers. Novel methods that integrate social and ecological data and prioritize local knowledge and community-based approaches are needed to meet this challenge. This thesis explores how linking local knowledge and community science approaches can bolster ecosystem-based management and coastal stewardship. Here I define community science as inquiry that is community-led, place-based, and aimed at improving governance processes with the goals of stewardship and social-ecological sustainability (after Charles et al., 2020). Together, local knowledge and community science can generate robust social and ecological data. I highlight the connections among these approaches and model how they can be applied to small-scale coastal fisheries. Using participatory mapping and interviews, I demonstrate how local knowledge can complement scientific knowledge by generating ecosystem hypotheses that can inform scientific inquiry and long-term monitoring. Local knowledge is critical because this holistic information is uniquely able to support actionable and responsive research and management by: (1) characterizing the social-ecological system at a fine spatial scale; (2) highlighting stakeholders’ priorities and observations; and (3) generating hypotheses about how and why the system is changing, and what drivers may be influencing these changes. I explore how local knowledge can inform the development of community science initiatives and examine the community science process through a case study in the Damariscotta River estuary, Maine, USA. I use a typology to assess the conditions for community science and how it can generate ecosystem-level information. The assessment revealed two primary conclusions: (1) community science can be an effective approach to studying co-managed fisheries and (2) community science is, by its nature, an ecosystem-scale approach to research. Integrating diverse knowledges and community partners can contribute to holistic understandings of dynamic marine coastal systems. These approaches can be applied to fisheries locally and regionally and have the potential to support ecosystem-based approaches to stewardship and management in marine coastal environments in Maine and beyond

A genome-wide investigation of the worldwide invader Sargassum muticum shows high success albeit (almost) no genetic diversity

Twenty years of genetic studies of marine invaders have shown that successful invaders are often characterized by native and introduced populations displaying similar levels of genetic diversity. This pattern is presumably due to high propagule pressure and repeated introductions. The opposite pattern is reported in this study of the brown seaweed, Sargassum muticum, an emblematic species for circumglobal invasions. Albeit demonstrating polymorphism in the native range, microsatellites failed to detect any genetic variation over 1,269 individuals sampled from 46 locations over the Pacific-Atlantic introduction range. Single-nucleotide polymorphisms (SNPs) obtained from ddRAD sequencing revealed some genetic variation, but confirmed severe founder events in both the Pacific and Atlantic introduction ranges. Our study thus exemplifies the need for extreme caution in interpreting neutral genetic diversity as a proxy for invasive potential. Our results confirm a previously hypothesized transoceanic secondary introduction from NE Pacific to Europe. However, the SNP panel unexpectedly revealed two additional distinct genetic origins of introductions. Also, conversely to scenarios based on historical records, southern rather than northern NE Pacific populations could have seeded most of the European populations. Finally, the most recently introduced populations showed the lowest selfing rates, suggesting higher levels of recombination might be beneficial at the early stage of the introduction process (i.e., facilitating evolutionary novelties), whereas uniparental reproduction might be favored later in sustainably established populations (i.e., sustaining local adaptation).Agence Nationale de la Recherche - ANR-10-BTBR-04; European Regional Development Fund; Fundacao para a Ciencia e a Tecnologia - SFRH/BPD/107878/2015, UID/Multi/04326/2016, UID/Multi/04326/2019; Brittany Region;info:eu-repo/semantics/publishedVersio

Status and conservation of the reef gastropod Trochus niloticus in the Philippines

The most commercially important reef gastropod Trochus niloticus mainly harvested for the production of mother-of-pearl buttons, is highly susceptible to over- exploitation. Although conservation measures began shortly after the start of its commercial harvest in the early 1900s, their populations have been severely depleted prompting some countries like the Philippines to declare it as a threatened species. With the country's limited success in conserving trochus, this thesis explores the status of trochus in the wild, on-going conservation measures and some aspects of its biology in Palawan, Philippines. Field surveys show that abundance was very low in marine protected sites (MPAs) in mainland Palawan in spite of their proximity to law enforcing bodies. Natural recruits occurred in heavily exploited MP As, but the fates of released juveniles produced from a decade of artificial propagation are unknown. The breeders have high survival rates in intertidal tanks and were successfully induced to spawn after nearly a year of rearing. The growth rates of hatchery produced juveniles in cages on the reef were as fast as in the wild. Translocated wild trochus had high survival rates but growth rates varied among sites. Elasticity analyses of age-based matrix models revealed that survival of sub- and young adults has the greatest contribution to intrinsic population growth rate, so enhancing the survival of these age groups should be preferred over "head starting" when conserving trochus. Efforts to revive the trochus populations should focus on effective long term management/protection of MPAs. Captive rearing of broodstock in subtidal tanks could be a much cheaper alternative to hatchery propagation. Acclimation to predators of hatchery- produced trochus prior to release is hoped to increase their chances of survival. The translocations of wild trochus could be a more effective means of reviving a depleted population in areas having no sign of recruitment.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Examining the Toxicity, Exposure, and Regulatory Approach to Potential Human Health Risks of the Algal Toxin Domoic Acid

Domoic acid is a neurotoxin produced by the marine diatom genus Pseudo-nitzschia and causes cell death primarily in the area of the brain responsible for long-term memory. The resulting severe illness has been termed amnesic shellfish poisoning. Domoic acid accumulates in shellfish and planktivorous fish that consume Pseudo-nitzschia, resulting in exposure to humans through consumption of planktivorous seafood. A regulatory standard in seafood was developed shortly after its discovery in 1987 to protect against acute effects. This regulatory standard has not been revised despite significant recent data in the scientific literature. This dissertation is divided into four sections: (1) an identification of anthropogenic and natural drivers of nutrient dynamics as well as social dynamics that can contribute to current and future exposure to domoic acid; (2) a review of the weight of evidence for revisiting the current regulatory standard based on recent low level chronic effects data in the toxicological literature, sensitive subpopulation information and long term seafood consumption data; (3) an analysis of monitoring data on the presence of Pseudo-nitzschia in ocean waters and domoic acid in seafood to examine spatial and temporal trends in human exposure; and (4) evaluation of the regulatory framework for natural toxins in seafood with domoic acid as an example. Nutrient and social dynamics have the potential to drive exposure in humans. Recent toxicological data are not reflected in the current standard as it is based on data for acute toxicity and protects against gross observable neurotoxicity rather than chronic effects. The recent literature has shown that exposure to domoic acid can result in more subtle physical and behavioral brain impacts that have been observed in limited human data as well as extensive data on laboratory animals and marine mammals. Toxicological studies have demonstrated that certain groups such as the young, and the elderly are much more sensitive to domoic acid exposure. This is of particular concern because monitoring data for domoic acid in seafood are limited and may not ensure protection of the public. Pseudo-nitzschia is ubiquitous both temporally and spatially. This dissertation concludes that the regulatory approach warrants revisiting

Green Economics: Assessing The Feasibility Of A New England Green Crab (Carcinus Maenas) Fishery Through Fishermen Perspectives

The European green crab (Carcinus maenas) is a well-adapted invasive species that has flourished throughout coastal New England. Its arrival has caused numerous negative environmental and socioeconomic impacts, including the decline of the Maine soft shell clam (Mya arenaria) fishery. Increases in north Atlantic sea surface temperatures have simultaneously propelled the proliferation of C. maenas and caused northward shifts in the geographic ranges of commercially relevant species, including the American lobster (Homarus americanus). C. maenas represents an underutilized species that H. americanus and M. arenaria fishers can target to supplement any lost income if C. maenas markets are economically viable. The research explores the development of the C. maenas fishery, describes any barriers to the industry and dissects the economic feasibility of markets based on minimum price points and current landings data. Maine-based fishers were interviewed regarding their views on the current industry and the principle obstacles facing the industry. Past and current landings data was analyzed to determine trends in economic value. The biggest barrier to further industry development is the price per pound of hard-shell crabs. The market value of current landings is far below the threshold of what is considered acceptable to fishers, but the price point is rising. For the fishery to expand, consumer demand must be created. Stakeholders should target farmers markets and chain grocers to further market product. This study was conducted with a limited sample size and analyzed just the perspectives of one sector of the seafood supply chain. Future studies should operate on a larger scale and evaluate the viewpoints of wholesalers and consumers