Salmoninae Commensal Bacteria Show a Positive Correlation Between Antibiotic Resistance and Mercury Resistance Profiles

Bacterial isolates from natural sites with high toxic and heavy metal contamination more frequently contain determinants for resistance to antimicrobials. Natural strains were isolated from the ingesta and external slime of Salmo salar (Linnaeus, 1758) and Salvelinusjontinalis (Mitchell, 1814). Fish specimens were acquired from Casco Bay hatcheries, Casco, ME where there is no history of antibiotic use. Seventy-nine bacterial strains, including many well-documented salmonid commensals (an association from which the fish derives no benefit), were identified using 165 rRNA gene sequencing. Mercury resistant isolates were selected for initially on 25μM HgCI2. Strains were then grown at 20-24°C on Trypticase Soy Agar (TSA) plates containing 0-1000μM HgCl2 or 0-130μM Phenyl Mercuric Acetate (PMA). Mercury in the hatchery feed water due to ubiquitous non-point source deposition has selected for the mercury resistance observed in bacterial strains. Antibiotic resistance determinations, as measured by Minimum Inhibitory Concentration MIC) assays were performed on the 79 bacterial isolates using Sensititrel antimicrobial susceptibility panels. A positive linear correlation between the mercury (pMA and HgCl2) MIC's and antibiotic resistance for all observed strains was demonstrated. Conjugation experiments with Pseudomonas, Aeromonas, and Azomonas donors confirmed phenotypic transfer of penicillin and cephem resistances to Escherichia coli DH5a recipients. Conjugation experiments with Pseudomonas donors showed minimal transfer of tetracycline and minoglycoside resistances to Escherichia coli DH5a recipients. Our study suggests that the accumulation of antimicrobial resistances observed in these natural bacterial populations may be due to the indirect selective pressure exerted by environmental mercury.

Diphyllobothriasis, Brazil

Cases of human diphyllobothriasis have been reported worldwide. Only 1 case in Brazil was diagnosed by our institution from January 1998 to December 2003. By comparison, 18 cases were diagnosed from March 2004 to January 2005. All patients who became infected ate raw fish in sushi or sashimi.

Development and application of DNA techniques for validating and improving pinniped diet estimates

Polymerase chain reaction techniques were developed and applied to identify DNA from .40 species of prey contained in fecal (scat) soft-part matrix collected at terrestrial sites used by Steller sea lions (Eumetopias jubatus) in British Columbia and the eastern Aleutian Islands, Alaska. Sixty percent more fish and cephalopod prey were identified by morphological analyses of hard parts compared with DNA analysis of soft parts (hard parts identified higher relative proportions of Ammodytes sp., Cottidae, and certain Gadidae). DNA identified 213 prey occurrences, of which 75 (35%) were undetected by hard parts (mainly Salmonidae, Pleuronectidae, Elasmobranchii, and Cephalopoda), and thereby increased species occurrences by 22% overall and species richness in 44% of cases (when comparing 110 scats that amplified prey DNA). Prey composition was identical within only 20% of scats. Overall, diet composition derived from both identification techniques combined did not differ significantly from hard-part identification alone, suggesting that past scat-based diet studies have not missed major dietary components. However, significant differences in relative diet contributions across scats (as identified using the two techniques separately) reflect passage rate differences between hard and soft digesta material and highlight certain hypothesized limitations in conventional morphological-based methods (e.g., differences in resistance to digestion, hard part regurgitation, partial and secondary prey consumption), as well as potential technical issues (e.g., resolution of primer efficiency and sensitivity and scat subsampling protocols). DNA analysis of salmon occurrence (from scat soft-part matrix and 238 archived salmon hard parts) provided species-level taxonomic resolution that could not be obtained by morphological identification and showed that Steller sea lions were primarily consuming pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon. Notably, DNA from Atlantic salmon (Salmo salar) that likely originated from a distant fish farm was also detected in two scats from one site in the eastern Aleutian Islands. Overall, molecular techniques are valuable for identifying prey in the fecal remains of marine predators. Combining DNA and hard-part identification will effectively alleviate certain predicted biases and will ultimately enhance measures of diet richness, fisheries interactions (especially salmon-related ones), and the ecological role of pinnipeds and other marine predators, to the benefit of marine wildlife conservationists and fisheries managers.

The fatty acid profiles and energetic substrates of two Nile tilapia (Oreochromis niloticus, Linnaeus) strains, Red-Stirling and Chitralada, and their hybrid

Protein and lipid content as well as the fatty acid (FA) composition of storage tissues were analysed in two varieties of Oreochromis niloticus (Red-Stirling and Chitralada) and their hybrid. The animals were maintained in cages for 11 months. The samples were taken when the animals weighed 10, 50, 100, 250 and 500 g. The results showed that changes in the metabolic processes occur during an increase in body mass in both varieties of tilapia and also their hybrid, but that these differences are not found in animals collected at the commercial weight. The protein content of the fillet and liver decreased with growth and the same protein content associated with growth was found for fillet lipid content. The genetic variety did not influence the FA profile of the fillet, but different genotypes had different hepatic FA compositions. Even with the same lipid content, the hepatocytes of Chitralada accumulated higher levels of polyunsaturated fatty acids (PUFA) n6 in triglycerides and increased C22:6n3 in the hepatocyte membranes. The higher n6PUFA content was compensated by a lower fraction of saturated FA in the hepatocyte triglycerides. The skin of Chitralada also had higher n6PUFA and C22:6n3 contents, suggesting a higher ability to deposit PUFA in the skin due to alterations in the liver synthetic pathway.

Ricerca, mediante tecniche di proteomica, di biomarcatori proteici utili nella valutazione della qualità degli alimenti di origine animale

In the last decades, the increase of industrial activities and of the request for the world food requirement, the intensification of natural resources exploitation, directly connected to pollution, have aroused an increasing interest of the public opinion towards initiatives linked to the regulation of food production, as well to the institution of a modern legislation for the consumer guardianship. This work was planned taking into account some important thematics related to marine environment, collecting and showing the data obtained from the studies made on different marine species of commercial interest (Chamelea gallina, Mytilus edulis, Ostrea edulis, Crassostrea gigas, Salmo salar, Gadus morhua). These studies have evaluated the effects of important physic and chemical parameters variations (temperature, xenobiotics like drugs, hydrocarbons and pesticides) on cells involved in the immune defence (haemocytes) and on some important enzymatic systems involved in xenobiotic biotransformation processes (cytochrome P450 complex) and in the related antioxidant defence processes (Superoxide dismutase, Catalase, Heat Shock Protein), from a biochemical and bimolecular point of view. Oxygen is essential in the biological answer of a living organism. Its consume in the normal cellular breathing physiological processes and foreign substances biotransformation, leads to reactive oxygen species (ROS) formation, potentially toxic and responsible of biological macromolecules damages with consequent pathologies worsening. Such processes can bring to a qualitative alteration of the derived products, but also to a general state of suffering that in the most serious cases can provoke the death of the organism, with important repercussions in economic field, in the output of the breedings, of fishing and of aquaculture. In this study it seemed interesting to apply also alternative methodologies currently in use in the medical field (cytofluorimetry) and in proteomic studies (bidimensional electrophoresis, mass spectrometry) with the aim of identify new biomarkers to place beside the traditional methods for the control of the animal origin food quality. From the results it’s possible to point out some relevant aspects from each experiment: 1. The cytofluorimetric techniques applied to O. edulis and C. gigas could bring to important developments in the search of alternative methods that quickly allows to identify with precision the origin of a specific sample, contributing to oppose possible alimentary frauds, in this case for example related to presence of a different species, also under a qualitative profile, but morpholgically similar. A concrete perspective for the application in the inspective field of this method has to be confirmed by further laboratory tests that take also in account in vivo experiments to evaluate the effect in the whole organism of the factors evaluated only on haemocytes in vitro. These elements suggest therefore the possibility to suit the cytofluorimetric methods for the study of animal organisms of food interest, still before these enter the phase of industrial working processes, giving useful information about the possible presence of contaminants sources that can induce an increase of the immune defence and an alteration of normal cellular parameter values. 2. C. gallina immune system has shown an interesting answer to benzo[a]pyrene (B[a]P) exposure, dose and time dependent, with a significant decrease of the expression and of the activity of one of the most important enzymes involved in the antioxidant defence in haemocytes and haemolymph. The data obtained are confirmed by several measurements of physiological parameters, that together with the decrease of the activity of 7-etossi-resourifine-O-deetilase (EROD linked to xenobiotic biotransformation processes) during exposure, underline the major effects of B[a]P action. The identification of basal levels of EROD supports the possible presence of CYP1A subfamily in the invertebrates, still today controversial, never identified previously in C. gallina and never isolated in the immune cells, as confirmed instead in this study with the identification of CYP1A-immunopositive protein (CYP1A-IPP). This protein could reveal a good biomarker at the base of a simple and quick method that could give clear information about specific pollutants presence, even at low concentrations in the environment where usually these organisms are fished before being commercialized. 3. In this experiment it has been evaluated the effect of the antibiotic chloramphenicol (CA) in an important species of commercial interest, Chamelea gallina. Chloramphenicol is a drug still used in some developing countries, also in veterinary field. Controls to evaluate its presence in the alimentary products of animal origin, can reveal ineffective whereas the concentration results to be below the limit of sensitivity of the instruments usually used in this type of analysis. Negative effects of CA towards the CYP1A- IPP proteins, underlined in this work, seem to be due to the attack of free radicals resultant from the action of the antibiotic. This brings to a meaningful alteration of the biotransformation mechanisms through the free radicals. It seems particularly interesting to pay attention to the narrow relationships in C. gallina, between SOD/CAT and CYP450 system, actively involved in detoxification mechanism, especially if compared with the few similar works today present about mollusc, a group that is composed by numerous species that enter in the food field and on which constant controls are necessary to evaluate in a rapid and effective way the presence of possible contaminations. 4. The investigations on fishes (Gadus morhua, and Salmo salar) and on a bivalve mollusc (Mytilus edulis) have allowed to evaluate different aspects related to the possibility to identify a biomarker for the evaluation of the health of organisms of food interest and consequently for the quality of the final product through 2DE methodologies. In the seafood field these techniques are currently used with a discreet success only for vertebrates (fishes), while in the study of the invertebrates (molluscs) there are a lot of difficulties. The results obtained in this work have underline several problems in the correct identification of the isolated proteins in animal organisms of which doesn’t currently exist a complete genomic sequence. This brings to attribute some identities on the base of the comparison with similar proteins in other animal groups, incurring in the possibility to obtain inaccurate data and above all discordant with those obtained on the same animals by other authors. Nevertheless the data obtained in this work after MALDI-ToF analysis, result however objective and the spectra collected could be again analyzed in the future after the update of genomic database related to the species studied. 4-A. The investigation about the presence of HSP70 isoforms directly induced by different phenomena of stress like B[a]P presence, has used bidimensional electrophoresis methods in C. gallina, that have allowed to isolate numerous protein on 2DE gels, allowing the collection of several spots currently in phase of analysis with MALDI-ToF-MS. The present preliminary work has allowed therefore to acquire and to improve important methodologies in the study of cellular parameters and in the proteomic field, that is not only revealed of great potentiality in the application in medical and veterinary field, but also in the field of the inspection of the foods with connections to the toxicology and the environmental pollution. Such study contributes therefore to the search of rapid and new methodologies, that can increase the inspective strategies, integrating themselves with those existing, but improving at the same time the general background of information related to the state of health of the considered animal organism, with the possibility, still hypothetical, to replace in particular cases the employment of the traditional techniques in the alimentary field.

The Effects of Smolt Stocking Strategies on Migratory Path Selection of Adult Atlantic Salmon in the Penobscot River, Maine

Understanding the homing behavior of Atlantic salmon Salmo salar is vital to the restoration program employed on the Penobscot River, Maine. To produce significant adult returns, managers currently stock hatchery-raised smolts in specific river sections, providing smolts the opportunity to imprint on chemical signals and enabling their return to productive spawning and rearing habitat as adults. In this study, we used observational evidence from passive integrated transponder telemetry to determine whether adults returning from smolt stockings behaved in a way that suggested strong homing to smolt stocking locations. Adults returning from smolt stocking locations located in or at the mouth of the Piscataquis River were more likely to be detected as entering the Piscataquis River than were adults returning from the upper Penobscot River smolt stocking locations. In general, returning adult Atlantic salmon that had been stocked near or in tributaries as smolts chose a path more quickly than those that had been stocked in more downstream or main-stem locations. These results suggest that Atlantic salmon smolts should be stocked at specific sites with superior habitat for spawning kind juvenile survival to capitalize on the strong homing tendency in adults. This technique call also be utilized to allow for natural selection and the development of localized stocks.

Responses of Atlantic Salmon Parr to Output of Pulsed Ultrasonic Transmitters

The output from some pulsed ultrasonic transmitters commonly used in fish movement studies is faintly audible to humans. This study was undertaken to determine if the output from these and some other transmitters is detectable by Atlantic salmon (Salmo salar) parr. Classical conditioning of cardiac deceleration was attempted using the transmitter's output as the conditioned stimulus. The results from 29 experimental and 14 control fish suggest that the parr were unable to detect the output from these transmitters.

Descaling Injury Impairs the Osmoregulatory Ability of Atlantic Salmon Smolts Entering Seawater

The effect of descaling injury on the osmoregulatory ability of hatchery Atlantic salmon Salmo salar smolts in seawater was investigated. Experimental series were initiated during early, middle, and late periods of the spring smolt migration (April 25, May 11, and May 31, respectively). For each time series, descaled smolts (subjected to descaling on 10% of the body surface area) and control smolts (held out of water for 15 s) were transferred to seawater at 0, 1, 3, or 7 d posttreatment. After fish were held in 35% seawater for 24 h, gill and blood samples were collected and analyzed for Na(+),K(+)-ATPase activity and plasma osmolyte levels. Based on gill Na(+),K(+)-ATPase activity, the three series spanned the period from early smolting (increasing activity) to de-smolting (decreasing activity). In each series, descaled fish transferred to seawater at 0 and 1 d posttreatment had greater plasma osmolality than control fish; descaled fish transferred to seawater at 3 d posttreatment did not differ from controls. The greatest perturbation in osmolality (70 milliosmoles) was observed at the peak of smolting (middle series), whereas lesser increases were seen for early and late-series smolts. The observed osmotic perturbations in descaled fish would probably reduce performance and decrease survival during smolt migration.

Migratory Urge and Gill Na(+),K(+)-ATPase Activity of Hatchery-Reared Atlantic Salmon Smolts from the Dennys and Penobscot River Stocks, Maine

Hatchery-reared Atlantic salmon Salmo salar smolts produced from captive-reared Dennys River and sea-run Penobscot River broodstock are released into their source rivers in Maine. The adult return rate of Dennys smolts is comparatively low, and disparity in smolt quality between stocks resulting from genetic or broodstock rearing effects is plausible. Smolt behavior and physiology were assessed during sequential 14-d trials conducted in seminatural annular tanks with circular flow. "Migratory urge'' (downstream movement) was monitored remotely using passive integrated transponder tags, and gill Na(+),K(+)-ATPase activity was measured at the beginning and end of the trials to provide an index of smolt development. The migratory urge of both stocks was low in early April, increased 20-fold through late May, and declined by the end of June. The frequency and seasonal distribution of downstream movement were independent of stock. In March and April, initial gill Na(+),K(+)-ATPase activities of Penobscot River smolts were lower than those of Dennys River smolts. For these trials, however, Penobscot River smolts increased enzyme activity after exposure to the tank, whereas Dennys River smolts did not, resulting in similar activities between stocks at the end of all trials. There was no clear relationship between migratory urge and gill Na(+),K(+)-ATPase activity. Gill Na(+),K(+)-ATPase activity of both stocks increased in advance of migratory urge and then declined while migratory urge was increasing. Maximum movement was observed from 2 h after sunset through 1 h after sunrise but varied seasonally. Dennys River smolts were slightly more nocturnal than Penobscot River smolts. These data suggest that Dennys and Penobscot River stocks are not markedly different in either physiological or behavioral expression of smolting.

Brown trout redd superimposition in relation to spawning habitat availability

The relationship between redd superimposition and spawning habitat availability was investigated in the brown trout (Salmo trutta L.) population inhabiting the river Castril (Granada, Spain). Redd surveys were conducted in 24 river sections to estimate the rate of redd superimposition. Used and available microhabitat was evaluated to compute the suitable spawning habitat (SSH) for brown trout. After analysing the microhabitat characteristics positively selected by females, SSH was defined as an area that met all the following five requirements: water depth between 10 and 50 cm, mean water velocity between 30 and 60 cm s)1, bottom water velocity between 15 and 60 cm s)1, substrate size between 4 and 30 mm and no embeddedness. Simple regression analyses showed that redd superimposition was not correlated with redd numbers, SSH or redd density. A simulation-based analysis was performed to estimate the superimposition rate if redds were randomly placed inside the SSH. This analysis revealed that the observed superimposition rate was higher than expected in 23 of 24 instances, this difference being significant (P menor que 0.05) in eight instances and right at the limit of statistical significance (P = 0.05) in another eight instances. Redd superimposition was high in sections with high redd density. High superimposition however was not exclusive to sections with high redd density and was found in moderate- and low-redd-density sections. This suggests that factors other than habitat availability are also responsible for redd superimposition. We argue that female preference for spawning over previously excavated redds may be the most likely explanation for high superimposition at lower densities.

Spawning and habitat management in salmonid populations at the southern edge of their natural ranges = Reproducción y gestión del hábitat en poblaciones de salmónidos en el extremo meridional de sus distribuciones naturales

Las poblaciones de salmónidos en la Península Ibérica (trucha común, Salmo trutta; y salmón atlántico, Salmo salar) se encuentran cerca del límite meridional de sus distribuciones naturales, y por tanto tienen una gran importancia para la conservación de estas especies. En la presente Tesis se han investigado algunos aspectos de la reproducción y de la gestión del hábitat, con el objeto de mejorar el conocimiento acerca de estas poblaciones meridionales de salmónidos. Se ha estudiado la reproducción de la trucha común en el río Castril (Andalucía, sur de España), donde se ha observado que la freza ocurre desde diciembre hasta abril con el máximo de actividad en febrero. Este hecho representa uno de los periodos reproductivos más tardíos y con mayor duración de toda la distribución natural de la especie. Además, actualmente se sabe que el resto de poblaciones andaluzas tienen periodos de reproducción similares (retrasados y extendidos). Análisis en la escala de la distribución natural de la trucha común, han mostrado que la latitud explica parcialmente tanto la fecha media de reproducción (R2 = 62.8%) como la duración del periodo de freza (R2 = 24.4%) mediante relaciones negativas: a menor latitud, la freza ocurre más tarde y durante más tiempo. Es verosímil que un periodo de freza largo suponga una ventaja para la supervivencia de las poblaciones de trucha en hábitats impredecibles, y por tanto se ha propuesto la siguiente hipótesis, que deberá ser comprobada en el futuro: la duración de la freza es mayor en hábitats impredecibles que en aquellos más predecibles. La elevada tasa de solapamiento de frezaderos observada en el río Castril no se explica únicamente por una excesiva densidad de reproductores. Las hembras de trucha eligieron lugares específicos para construir sus frezaderos en vez de dispersarse aleatoriamente dentro del hábitat adecuado para la freza que tenían disponible. Estas observaciones sugieren que las hembras tienen algún tipo de preferencia por solapar sus frezaderos. Además, en ríos calizos como el Castril, las gravas pueden ser muy cohesivas y difíciles de excavar, por lo que el solapamiento de frezaderos puede suponer una ventaja para la hembra, porque la excavación en sustratos que han sido previamente removidos por frezas anteriores requerirá menos gasto de energía que en sustratos con gravas cohesivas que no han sido alteradas. Por tanto, se ha propuesto la siguiente hipótesis, que deberá ser comprobada en el futuro: las hembras tienen una mayor preferencia por solapar sus frezaderos en ríos con sustratos cohesivos que en ríos con sustratos de gravas sueltas. En el marco de la gestión del hábitat, se han empleado dos enfoques diferentes para la evaluación del hábitat físico, con el objeto de cuantificar los cambios potenciales en la disponibilidad de hábitat, antes de la implementación real de determinadas medidas sobre el hábitat. En primer lugar, se ha evaluado el hábitat físico del salmón atlántico en el río Pas (Cantabria, norte de España), en la escala del microhábitat, empleando la metodología IFIM junto con un modelo hidráulico bidimensional (River2D). Se han simulado una serie de acciones de mejora del hábitat y se han cuantificado los cambios en el hábitat bajo estas acciones. Los resultados mostraron un aumento muy pequeño en la disponibilidad de hábitat, por lo que no sería efectivo implementar estas acciones en este tramo fluvial. En segundo lugar, se ha evaluado el hábitat físico de la trucha común en el río Tajuña (Guadalajara, centro de España), en la escala del mesohábitat, empleando la metodología MesoHABSIM. Actualmente, el río Tajuña está alterado por los usos agrícolas de sus riberas, y por tanto se ha diseñado una restauración para mitigar estos impactos y para llevar al río a un estado más natural. Se ha cuantificado la disponibilidad de hábitat tras la restauración planteada, y los resultados han permitido identificar los tramos en los que la restauración resultaría más eficaz. ABSTRACT Salmonid populations in the Iberian Peninsula (brown trout, Salmo trutta; and Atlantic salmon, Salmo salar) are close to the southern limit of their natural ranges, and therefore they are of great importance for the conservation of the species. In the present dissertation, some aspects of spawning and habitat management have been investigated, in order to improve the knowledge on these southern salmonid populations. Brown trout spawning have been studied in the river Castril (Andalusia, southern Spain), and it has been observed that spawning occurs from December until April with the maximum activity in February. This finding represents one of the most belated and protracted spawning periods within the natural range of the species. Furthermore, it is now known that the rest of Andalusian populations show similar (belated and extended) spawning periods. Broad-scale analyses throughout the brown trout natural range showed that latitude partly explained both spawning mean time (R2 = 62.8%) and spawning duration (R2 = 24.4%) by negative relationships: the lower the latitude, the later the spawning time and the longer the spawning period. It is plausible that a long spawning period would be an advantage for survival of trout populations in unpredictable habitats, and thus the following hypothesis has been proposed, which is yet to be tested: spawning duration is longer in unpredictable than in predictable habitats. High rate of redd superimposition observed in the river Castril was not only caused by high density of spawners. Trout females chose specific sites for redd construction instead of randomly dispersing over the suitable spawning habitat. These observations suggest that female spawners have some kind of preference for superimposing redds. Moreover, in limestone streams such as Castril, unused gravels can be very cohesive and hard to dig, and thus redd superimposition may be an advantage for female, because digging may require less energy expenditure in already used redd sites than in cohesive and embedded unused sites. Hence, the following hypothesis has been proposed, which is yet to be tested: females have a higher preference for superimposing redds in streambeds with cohesive and embedded substrates than in rivers with loose gravels. Within the topic of habitat management, two different approaches have been used for physical habitat assessment, in order to quantify the potential change in habitat availability, prior to the actual implementation of proposed habitat measures. Firstly, physical habitat for Atlantic salmon in the river Pas (Cantabria, northern Spain) has been assessed at the microhabitat scale, using the IFIM approach along with a two dimensional hydraulic model (River2D). Proposed habitat enhancement actions have been simulated and potential habitat change has been quantified. Results showed a very small increasing in habitat availability and therefore it is not worth to implement these measures in this stream reach. Secondly, physical habitat for brown trout in the river Tajuña (Guadalajara, central Spain) has been assessed at the mesohabitat scale, using the MesoHABSIM approach. The river Tajuña is currently impacted by surrounding agricultural uses, and thus restoration was designed to mitigate these impacts and to drive the river to a more natural state. Habitat availability after the planned restoration has been quantified, and the results have permitted to identify in which sites the restoration will be more effective.

Identification of the salmonid IL-17A/F1a/b, IL-17A/F2b, IL-17A/F3 and IL-17N genes and analysis of their expression following in vitro stimulation and infection

Date of Acceptance: 15/04/2015

First report of three Kudoa species from Eastern Australia: Kudoa thyrsites from Mahi mahi (Coryphaena hippurus), Kudoa amamiensis and Kudoa minithyrsites n. sp. from sweeper (Pempheris ypsilychnus)

Fish species around the world are parasitized by myxozoans of the genus Kudoa, several of which infect and cause damage of commercial importance. In particular, Kudoa thyrsites and Kudoa amamiensis infect certain cultured fish species causing damage to muscle tissue, making the fish unmarketable. Kudoa thyrsites has a broad host and geographic range infecting over 35 different fish species worldwide, while K. amamiensis has only been reported from a few species in Japanese waters. Through morphological and molecular analyses we have confirmed the presence of both of these parasites in eastern Australian waters. In addition, a novel Kudoa species was identified, having stellate spores, with one polar capsule larger than the other three. The SSU rDNA sequence of this parasite was 1.5% different from K. thyrsites and is an outlier from K. thyrsites representatives in a phylogenetic analysis. Furthermore, the spores of this parasite are distinctly smaller than those of K. thyrsites, and thus it is described as Kudoa minithyrsites n. sp. Although the potential effects of K. minithyrsites n. sp. on its fish hosts are unknown, both K. thyrsites and K. amamiensis are associated with flesh quality problems in some cultured species and may be potential threats to an expanding aquaculture industry in Australia.

Silica reduces the toxicity of aluminium to a tropical freshwater fish (Mogurnda mogurnda)

The toxicity of aluminium (Al) to fish in acidic waters has been well documented. It was therefore expected that Al toxicity would be significant in fish communities in Gadjarrigamarndah (Gadji) Creek, a seasonally flowing stream in tropical northern Australia. This creek receives acidic groundwater containing elevated concentrations of Al from earlier land irrigation of treated mine tailings water from the former Nabarlek uranium mine. It was hypothesised that Al toxicity was reduced by high levels of silica (Si) in the water, and the subsequent formation of Al-silicate complexes. This prompted a laboratory assessment of the toxicity of Gadji Creek water to sac-fry of the native fish, Mogurnda mogurnda, followed by more detailed investigation of the toxicity of Al and the influence of Si in reducing Al toxicity. No mortality of M. mogurnda sac-fry was observed in two toxicity tests using Gadji Creek water collected in August 1997 and September 1998. The majority of Al (80-95%) was calculated to be complexed with humic substances and sulfate, with <1% being complexed with silicate. Assessment of the influence of silica on the acute toxicity of Al in the absence of natural organic complexants (i.e. in reconstituted freshwater, pH 5) revealed that Si reduced Al toxicity. As the molar ratio of Si:Al was increased, the percent survival of M. mogurnda sac-fry increased until there was no significant (P > 0.05) difference from the controls. However, speciation modelling again predicted that little (<3%) Al complexed with silicate, with the speciation and bioavailability of Al remaining constant as the molar ratio of Si:Al increased. Therefore, the original hypothesis that Al-silicate complexes in solution reduced the toxicity of Al to M. mogurnda could not be supported. This potential mechanism, and an alternative hypothesis, that Si competes with Al for binding sites at the fish gill surface, requires further investigation. Crown Copyright (C) 2002 Published by Elsevier Science Ltd. All rights reserved.

Catch and effort from a recreational trolling fishery in a large lake

Over recent decades recreational fisheries have grown substantially throughout the world. Despite this increase, catches from recreational fisheries have often been ignored in fisheries management, although this is now being remedied. Monitoring recreational fisheries can be expensive, and the primary means used for monitoring is angler (creel) surveys, typically funded from sales of fishing licences. The studies presented in this thesis examine different approaches to monitoring recreational trolling fisheries’ catch and effort, where fishing licenses are not required and there are no reporting requirements. I present results from a complemented roving/mail-in survey undertaken during 2013-2014 to estimate recreational effort and catch of Atlantic salmon (Salmo salar) and brown trout (S. trutta) in the largest lake in the European Union, Lake Vänern, Sweden. I also evaluate different angler catch reporting methods (mail-in, tournament reports and face-to-face interviews) and compare catch rates within and among spring and fall fishing periods. In addition, mail-in survey data are examined for recall bias.   I estimate that 28.7 tonnes of salmon and trout combined were harvested by the recreational trolling fishery in 2014, more than the commercial and subsistence fisheries combined. Seasonal differences in both recreational effort and catch were observed. Effort, in boat hours, was significantly higher in spring than in fall. Catch rates of trout were higher in fall than in spring, but there were no seasonal differences in catches of salmon. Harvest per boat day did not differ significantly among catch reporting methods, indicating that all three methods could be useful for managers interested in harvest rates. In contrast, total and released catch per boat day differed among reporting methods, with tournament anglers catching more fish in total. Finally, there was little evidence for recall bias in mail-in surveys, indicating that mail-in surveys are useful for collecting unbiased catch data. My study is the most comprehensive angler survey to date for Lake Vänern, and my results should be of immediate use to local fisheries managers and should also be of interest to researchers and managers interested in estimating catch and effort for fisheries at large spatial scales.