Lethal biotic interactions strongly influence the potential for aquatic non-native species to establish and endure in habitats to which they are introduced. Predators in the recipient area, including native and previously established non-native predators, can prevent establishment, limit habitat use, and reduce abundance of non-native species. Management efforts by humans using methods designed to cause mass mortality (e.g., trapping, biocide applications) can reduce or eradicate non-native populations. However, the impacts of predator and human induced mortality may be mitigated by the behavior or population-level responses of a given non-native species. My dissertation examined the responses of non-native aquatic species to the risk of predation by novel (i.e., no previous exposure) predators in the recipient community and indicators of potential compensatory responses by non-native populations to increased mortality resulting from removal efforts. My dissertation addresses four primary questions. 1) Can first generation, naïve invaders recognize and defend against predators found within the region of invasion through the expression of inducible defenses? 2) Can the overcompensatory potential of a population be predicted through examinations of intraspecific interactions of individuals from the population? 3) What is the relationship between removal effort outcome (i.e., successful or unsuccessful reduction of the target population) and compensatory population responses? 4) Is there a relationship between characteristics of removal efforts that are typically available to managers (e.g., target area size, target area connectivity, removal methodology) and compensatory population responses that could indicate the relative likelihood of compensation resulting from removal efforts? An invading species should be more likely to establish if it can successfully identify and defend against predators in the recipient range, such as through the expression of inducible defenses. Inducible defenses are behavioral or physiological changes that reduce an organism's susceptibility to predation. Through a series of laboratory experiments, I tested whether inducible defenses, in the form of increased burrowing depth, may have benefited the early stage of invasion of Nuttallia obscurata (purple varnish clam), an established Northeast Pacific invader. Specimens of N. obscurata were collected from introduced populations in the Northeast Pacific and from a native population in Japan. The clams were exposed to chemical and physical cues from Northeast Pacific crab predators, including the native Metacarcinus magister (Dungeness crab), an abundant and frequent predator of N. obscurata. While introduced N. obscurata increased their burrowing depth in the physical presence of M. magister, clams collected from their native range showed no such response. This lack of increased burrowing depth by naïve clams in response to a predator native to the newly invaded range, but a significant increase in depth for clams from populations established in the range suggests that while inducible defenses likely did not contribute to the initial establishment of N. obscurata in the Northeast Pacific, they may contribute to their continued persistence and expansion in their introduced range. Some efforts to reduce invasive populations have paradoxically led to population increases. This phenomenon, referred to as overcompensation, occurs when strong negative density-dependent interactions are reduced through increased mortality within a population, resulting in an increase in the population's recruitment rate sufficient to increase the population's overall abundance. Increases in a population's recruitment rate can result from reduced cannibalism of juveniles resulting in lower mortality of new recruits, from increased adult reproductive output, which increases the number of potential recruits, or from reductions in size and/or age at maturity of the unharvested population, which increases the number of reproductive individuals. I predicted the overcompensatory potential of a population of Carcinus maenas (European green crab) in Bodega Harbor, California, using a series of laboratory and field experiments examining intraspecific pressures of adults on juveniles in the population. This measure of intraspecific pressure was used to predict the overcompensatory potential of the population in response to increased mortality from ongoing removal efforts. This prediction was then assessed using pre- and post-removal surveys of juvenile recruitment in Bodega Harbor compared to nearby populations, testing for evidence of overcompensation. While adult C. maenas in Bodega Harbor had limited negative impacts on juveniles, I concluded it was unlikely to result in overcompensation. Relative juvenile abundance did not statistically increase in removal compared to reference populations, consistent with my conclusion from the experiments. Increases in recruitment rates can occur as a result of efforts to remove non-native species. This increase in recruitment can result in overcompensation, but more commonly results in compensation, where recruitment rates increase relative to pre-removal recruitment but does not result in in the population's abundance exceeding pre-removal levels. However, a detailed and accurate prediction of the response of a population to harvest is time consuming and data intensive. This is not feasible for most efforts to eradicate non-native species, which have the greatest chance of success when enacted rapidly after detection. For my final chapter, I performed a literature review and accompanying statistical analysis to determine if typically available information related to the removal effort (site size, site connectivity, and removal technique) could be used to determine increased risk of compensation for a given effort to remove aquatic invasive species. Compensation was closely linked to unsuccessful removal efforts and was observed only among efforts utilizing physical removal methods. However, the frequency with which compensation occurred varied with the exact technique employed, occurring most frequently in removal utilizing electrofishing. Additionally, evidence of compensation was more frequent among larger removal areas with variable connectivity. While other predictors (temperature, effort, etc) might add to the predicative power, the findings of the review provide criteria for managers to determine the relative risk of compensation prior to the start of removal. Further understanding of how invasive species respond to lethal biotic interactions, including anthropogenically mediated control measures, can aid in assessing the risk of invasion for a given species and inform managers of the risk of complications resulting from removal efforts. While inducible defenses may contribute to the long-term success of an introduced species in their recipient range, my findings did not support the idea that inducible defenses triggered by predator cues contributed to their initial introduction in this case. However, research on other non-native species and offspring of previously naïve prey would allow for a clearer picture of the role of inducible defenses in the invasion process. Compensation resulting from removal efforts does not guarantee failure, and certain characteristics of removal efforts seem to indicate increased risk of compensation. Together these components help identify how biotic interactions surrounding mortality risk of an invading species help shape the trajectory of invasion.

When multiple predators foraging together have different individual consumption rates than predators foraging in isolation, they exhibit non-independent multiple predator effects on prey. I examined multiple predator effects in a system consisting of invasive green crabs (Carcinus maenas L.), native rock crabs (Cancer irroratus Say) and benthic macrofauna prey. First, I examined multiple predator effects when green crabs and rock crabs forage on soft-shell clams (Mya arenaria L.) in different habitat types (sand, sand with artificial seagrass) and assessed the behavioural mechanisms responsible for the observed predation effects. Independent multiple predator effects on prey were detected for most conspecific and heterospecific pairs in both habitat types. In general, crab foraging behaviours were not affected by the presence of another predator. Interactions between predators did not influence foraging behaviours because encounters were infrequent, short in duration and predominantly non-aggressive. A non-independent multiple predator effect on prey (marginally significant) was observed when green crabs foraged with rock crabs in artificial seagrass. This effect, however, could not be explained by the observed crab behaviours. Second, I investigated multiple predator effects when green crabs and rock crabs forage on a soft-sediment macrofauna community. Because crabs did not have significant predation effects on the community throughout the experiment, I did not evaluate multiple predator effects on prey. It is possible that crab predation was not important in regulating the macrofauna community, in which case multiple predator effects were non-existent. Predation may have been suppressed due to a combination of factors, including interactions between predators, harsh environmental conditions or a sub-optimal prey field. Alternatively, my ability to detect significant predation effects may have been hindered because of prey movement in and out of cages or low statistical power. Overall, results from this thesis demonstrate that multiple predator effects on prey may differ with habitat and highlights the importance of conducting behavioural observations to better understand interactions between predators and the resulting consequences for prey. Multiple predator effects on a soft-sediment community should be re-evaluated to assess the importance of these crab species in regulating benthic macrofauna under natural conditions.

Orientador: Irene Bastos Franceschini Vicentini / Banca: Antonio Marcos Orsi / Banca: Maíra Aparecida Stefanini / Banca: Margarida Maria Barros Ferreira Lima / Banca: Maria Terezinha Siqueira Bombonato / Resumo: O presente trabalho realizou o estudo dos aspectos estruturais do hepatopâncreas, ovários e da caracterização hormonal de fêmeas de Macrobrachium amazonicum, nos diferentes estágios de maturação gonadal. Para tanto utilizaram-se 150 fêmeas adultas subdivididas entre os cinco diferentes estágios de maturação ovariana. Após serem capturados os animais foram pesados e mortos por choque térmico. Ovários e hepatopâncreas foram coletados e pesados individualmente para obtenção dos índices gonadossomático (IGS) e hepatossomático (IHS). Para as análises de microscopia de luz e eletrônica de transmissão, ovários e hepatopâncreas foram fixados em solução de Karnovsky e seguiram os procedimentos de rotina de inclusão. Os ovários, hepatopâncreas e hemolinfa destinados à quantificação hormonal foram armazenados em ependorfes e preservados em nitrogênio líquido a -70ºC, para posterior processamento de radioimunoensaio visando avaliação das concentrações de estradiol, progesterona e testosterona. Os resultados relacionados ao IGS e IHS demonstram uma correlação inversa entre os ovários e o hepatopâncreas nos diferentes estágios de maturação gonadal. Em relação ao desenvolvimento ovariano, observa-se a distribuição de cinco tipos celulares ao longo dos cinco estágios de maturação gonadal. Desta forma encontram-se as ovogônias ou células germinativas mais jovens no estágio I de maturação ovariana. As células pré-vitelogênicas, observadas a partir do estágio II, apresentam vesículas de retículo endoplasmático rugoso. Essas vesículas são importantes nas fases de vitelogênese endógena e exógena. Os ovócitos em vitelogênese inicial, característicos do estágio III, apresentam a deposição de vitelo endógeno. As células em vitelogênese avançada, próprias do estágio IV de maturação gonadal, são o alvo principal da vitelogênese ...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study described the structural aspects of the hepatopancreas and ovaries, and the hormonal features of females of the freshwater prawn Macrobrachium amazonicum, during the reproductive cycle. The specimens were captured and killed by thermic chock. The gonadosomatic (GSI) and hepatosomatic (HSI) indices were calculated as the percentage of the weight of the gonad and hepatopancreas to total body weight, respectively. Ovaries and hepatopancreas were fixed in Karnovsky solution and destined to light and ultrastructural microscopy studies. Small portions of the ovary, hepatopancreas and hemolymph were frozen in liquid nitrogen, for later steroid quantification (estradiol, progesterone and testosterone). The relationships between GSI and HSI demonstrate an inverse correlation between ovary and hepatopancreas during the maturation cycle. The oocytes distribution is variable depending on the ovarian maturation degree. The ovary in stage I consists of oogonia. The ovary in stage II consists mainly by previtellogenic oocytes that possess vesicles of the endoplasmic reticulum. These vesicles are important to endogenous and exogenous vitelogenesis. Initial vitellogenic oocytes are mainly observed in the ovary in stage III and possess vitelline reserve, called as endogenous vitelogenesis. Ovary in stage IV is composed of late vitellogenic oocytes that uptake exogenous vitellogenin. Mature oocytes present a corion formation. The hepatopancreas is composed by tubules that are lined by a pseudostratified epithelium, which consists of five cell types, identified as E (embryonic), F (fibrillar), B (blisterlike), R (resorptive) and M (basal). These cells present relationships with digestion and nutrient storage, which are very important for the reproductive processes ...(Complete abstract, click electronic access below) / Doutor

The advective motion of seawater governs the transport of almost everything, animate or inanimate, present in the ocean and those lacking the ability to outswim the currents have to follow the flow. This makes modelling of advective ocean transports a powerful tool in various fields of science where a displacement of something over time is studied. The present thesis comprises four different applications of ocean-transport modelling, ranging from large-scale heat transports to the dispersion of juvenile marine organisms. The aim has been to adapt the method not only to the object of study, but also to the available model-data sets and in situ-observations. The first application in the thesis is a study of the oceanic heat transport. It illustrates the importance of wind forcing for not only the heat transport from the Indian to the Atlantic Ocean, but also for the net northward transport of heat in the Atlantic. In the next study focus is on the particle-transport differences between an open and a semi-enclosed coastal area on the Swedish coast of the Baltic Sea. The modelled patterns of sedimentation and residence times in the two basins are examined after particles having been released from a number of prescribed point sources. In the two final studies the transport-modelling framework is applied within a marine-ecology context and the transported entities are larvae of some Scandinavian sessile and sedentary species and non-commercial fishes (e.g. the bay barnacle, the blue mussel, the shore crab and the gobies). The effects of depth distribution of dispersing larvae on the efficiency of the Marine Protected Areas in the Baltic Sea are examined. Further, the diversity in dispersal and connectivity depending on vertical behaviour is modelled for regions with different tidal regimes in the North Sea, the Skagerrak and the Kattegat. The spatial scales dealt with in the studies varied from global to a highly resolved 182-metres grid. The model results, excepting those from the global study, are based on or compared with in situ-data. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Submitted. 4: Manuscript.</p>

Orientador: Wagner Cotroni Valenti / Banca: Helenice Pereira de Barros / Banca: José Eurico Possebon Cyrino / Banca: Gilberto Moraes / Banca: Wilson Massamitu Furuya / Resumo: A formulação de uma dieta balanceada que atenda as exigências dos minerais cálcio e fósforo nas larvas de Macrobrachium rosenbergii, é importante para garantir maior produtividade na larvicultura. Assim, avaliou-se o efeito de diferentes níveis de cálcio e fósforo na dieta sobre as principais variáveis de produção. O delineamento experimental foi em blocos casualizados, em esquema fatorial 3x3, correspondente a três níveis de cálcio (0,35; 1,00 e 1,90%) e três de fósforo (0,70; 1,50 e 2,30%), com três repetições realizadas em blocos temporais. Dois dias após a eclosão, as larvas passaram a ser alimentadas com quantidades crescentes de náuplios de Artemia. A partir do 11º dia (zoea VII), iniciou-se a co-alimentação, fornecendo-se as dietas-teste juntamente com os náuplios de Artemia até o final do ciclo de larvicultura. No 27º dia de cultivo, quando aproximadamente 90% das larvas metamorfosearam-se em pós-larvas (PL), realizou-se a despesca. Foi calculada a taxa de sobrevivência, a biomassa final de PL, a porcentagem de larvas e a produtividade (PL L-1) em cada tratamento. Observou-se que as larvas de M. rosenbergii alimentadas com dieta inerte contendo 0,35 ou 1,07% de Ca total, e 1,50% de P total (1,15% de P disponível) melhoraram significativamente a sobrevivência e o número de pós-larvas produzidas por litro ao final da larvicultura. A inclusão de 1% de P na forma de NaH2PO4 e unicamente o Ca proveniente da dieta basal (0,35%) são adequados para melhorar o desempenho produtivo desta espécie. / Abstract: The formulation of a balanced diet, which provides the requirements of calcium and phosphorus minerals for Macrobrachium rosenbergii larvae is important to guarantee good productivity of post-larvae. Hence, the effect of different levels of calcium and phosphorus in the inert diet on the principal production variables was evaluated during the hatchery. It was used a randomized block experimental design, in a 3x3 factorial scheme, with three levels of calcium (0.35; 1.00 and 1.90 %) and three levels of phosphorus (0.70; 1.50 and 2.30 %), with three replicates. Two days after hatching, larvae started feeding on increasing quantities of Artemia nauplii. Co-feeding started at the 11th day (zoea VII), when test-diets plus Artemia nauplii were supplied up to the end of the rearing cycle. In the 27th day, when approximately 90% of the larvae turned into post larvae (PL), harvest was done. Survival rate, final biomass of PL, percentage of larvae and productivity (PL L-1) were calculated in all treatments M. rosenbergii larvae fed on inert diet containing 0.35 or 1.07 % of total Ca and 1.50 % of total P (1.15 % of P available) had significantly improved survival rate and productivity. Inclusion of 1.0 % of total P and only the dietary Ca from the basal diet (0.35%) are adequate to improve the productive performance on this specie. / Resumen: La formulación de una dieta balanceada que atienda las exigencias de los minerales calcio y fósforo en las larvas de Macrobrachium rosenbergii, es importante para garantizar mejor productividade en la larvicultura. Asi, se evaluó el efecto de diferentes niveles de calcio y fósforo en la dieta sobre las principales variables de producción. El diseño experimental fue en bloques completamente al azar, en esquema factorial 3x3, correspondiente a tres niveles de calcio (0,35; 1,00 e 1,90%) y tres de fósforo (0,70; 1,50 e 2,30%), con tres repeticiones realizadas en bloques temporales. Dos días después de la eclosión las larvas pasaron a ser alimentadas con cantidades crecientes de náuplios de Artemia. A partir del 11º día (zoea VII), se inició la alimentación conjunta, ofreciendo las dietas-teste acompañadas por los náuplios de Artemia hasta el final del ciclo de larvicultura. El 27º día del cultivo, cuando aproximadamente 90% de las larvas se metamorfosearon en postlarvas (PL), se realizó la cosecha. Fue calculada la tasa de sobrevivencia, biomasa final de PL, el porcentaje de larvas y la productividad (PL L-1) en cada tratamiento. Se observó que las larvas de M. rosenbergii alimentadas con dieta inerte conteniendo 0,35 ó 1,07% de Ca total, y 1,50% de P total (1,15% de P disponible) mejoraran significativamente la sobrevivencia y el número de postlarvas producidas por litro al final de la larvicultura. La inclusión de 1% de P en la forma de NaH2PO4 y únicamente el Ca proveniente de la dieta basal (0,35%) son adecuados para mejorar el desempeño productivo de esta especie. / Résumé: La formulation d'un régime alimentaire équilibré que puisse répondre aux besoins de calcium et de phosphore des larves de Macrobrachium rosenbergii est très important pour assurer des meilleures productivités à la fin de la larveculture. L'effet de différents niveaux de calcium et de phosphore sur le régime alimentaire a été evalué sur les principaux variables de production. Une délineation complétement au hasard en schème factoriel 3x3, a été utilisé, en correspondant à trois niveaux de calcium (0,35; 1,00 et 1,90%) et trois niveaux de phosphore (0,70; 1,50 et 2,30%). Chaque traitement a eu 3 répétitions. Deux jours après l'éclosion les larves ont été nourries avec des quantités croissantes de nauplii d'Artemia. A partir du onzième jour (zoea VII), la coalimentation a été introduite en fournissant les diètes-teste en plus des nauplii d' Artemia jusqu'à la fin du cycle de larveculture. Au 27ème jour du cycle où 90% des larves, à peu près, se sont déjà méthamorphosées en pos-larves (PL), la récolte de fin d'élevage a été faite. Le taux de survie, la biomasse finale de PL, la pourcentage de larves et la productivité (PL L-1) ont été calculés pour chaque traitement. On a pu observer que les larves de M. rosenbergii qu'ont été nourries par une diète inerte de 0,35 ou 1,07% de calcium total et 1,50% de P total (1,15% de P disponible) ont eu leurs taux le survie beaucoup ameliorés aussi bien que le numero de pos-larves qu'ont été produites par litre à la fin da la larveculture. L'inclusion de 1% de P sur la forme de NaH2PO4 et le Ca venu de la diète basal (0,35%) sont suffisants pour améliorer la production de cette espèce. / Doutor

Predators can have large effects on prey populations and on the structure and function of communities. In addition to direct consumption of prey, predators often cause prey to alter their foraging behavior, habitat selection, and morphology. These non-lethal effects of predators can propagate to multiple trophic levels and often exert equal or larger effects upon communities than those of direct consumption. For non-lethal predatory effects to occur, prey must detect and respond to predation risk. While the importance of information transfer in this process has been realized, few studies explore how prey responses are influenced by predator characteristics and environmental conditions that influence the transmission of cues indicative of predation risk. In this dissertation I investigate factors that influence how a single prey species evaluates and responds to predation risk. Here, I examined: 1) the type and nature of cues prey use to evaluate predator risk; 2) how predator identity, predator diet, and the relative risk of predators influence prey response to predation risk; 3) how hydrodynamic conditions influence the delivery of predator cues; 4) how biogeographic trends in predator distribution influence prey response to predation risk; and 5) how genetic structure might vary according to prey geographic location and habitat. To address these questions, I used a common intertidal model system consisting of the rocky intertidal whelk Nucella lapillus (Linnaeus, 1758) and a suite of its predators, the native rock crab Cancer irroratus (Say, 1817), Jonah crab Cancer borealis (Stimpson, 1859), and the invasive green crab Carcinus maenas (Linnaeus, 1758). Nucella use chemical cues emanating from their most common predator (Carcinus maenas) and crushed conspecifics to evaluate predation risk. Nucella from different habitats experience different levels of predation risk, and Nucella from habitats with high levels of predation had larger antipredatory responses to predator risk cues than Nucella that experienced less predation. These chemical cues indicative of predation risk are influenced by hydrodynamic conditions, and Nucella have the strongest anti-predatory response in flow velocities of u= ~4- 8 cm s^-1. Furthermore, Nucella from geographic regions where green crabs are historically absent did not elicit anti-predatory responses, while Nucella from regions where green crabs are common frequently responded. Findings from my dissertation research demonstrate that prey detection and response to predation risk is highly dependent upon predator identity, predator diet, environmental forces, and biogeographic patterns in predator and prey distributions.