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The stable isotope values of nitrogen ([[delta].sup.15]N) and carbon ([[delta].sup.13]C) have been widely used in ecological studies to decipher the trophic relationships and interactions that occur between living organisms. The aim of this study was to determine the trophic relationship between a commercially important tropical Australian marine fish (Protonibea diacanthus (Lacepede, 1802)) (Sciaenidae) and its associated parasites, through stable isotope analysis of nitrogen and carbon ([[delta].sup.15]N and [[delta].sup.13]C). We examined the stable isotope ecology of four parasitic organisms: adult ectoparasitic copepods, and endoparasitic adult digeneans and nematodes and plerocercoids. Nitrogen in endoparasites was consistently depleted when compared with the host; however, digeneans expressed nitrogen signatures almost equivalent to those of the host. Ectoparasitic copepods were the only parasite that was substantially enriched in nitrogen compared with the host. All adult parasitic organisms were carbon depleted when compared with the host tissue associated with the site of infection; however, plerocercoids were enriched. Our findings emphasize the complexity of parasite-host interactions and the varying values of isotopic discrimination between parasite type, life-cycle stage, and location in host. Key words: helminth, copepod, Protonibea diacanthus, black-spotted croaker, marine fish, isotope, parasite ecology, Introduction Parasitism is a complex life history strategy that is ubiquitous across all ecosystems. Parasites are critical components of biodiversity, playing an integral role in ecosystem functioning and food web [...]

Several hypotheses and conceptual models propose to explain mechanisms mediating riverine fish abundance, but few empirical studies to date have explored their utility in tropical systems. This study assesses key components of previous fish recruitment models by exploring spatiotemporal variation in larval fish assemblages in response to predicted key drivers in a tropical Australian river catchment. Data on larval fish composition and abundance, alongside hydrological, hydraulic, habitat and food variables, were collected monthly to bimonthly over one year at eight sites. Variables which best predicted larval fish abundance and diversity were determined with Boosted Regression Trees. The most commonly important predictors were microfauna abundance, structural habitat complexity and temperature, with high values of each predicting high larval fish abundance and diversity. Maximum larval diversity occurred when discharge was highest because several wet-season spawning taxa occurred alongside aseasonally spawning taxa. These findings support previous generic fish recruitment models, demonstrating the utility of their inclusion in the recent Riverine Recruitment Synthesis Model and the applicability of this model for describing processes important for tropical riverine fish recruitment. Key words: habitat complexity, zooplankton, hydrology, Daly River, northern Australia Plusieurs hypotheses et modeles conceptuels proposent d'expliquer les mecanismes qui modulent l'abondance des poissons de riviere, mais peu d'etudes empiriques a ce jour ont explore leur utilite pour les systemes tropicaux. La presente etude evalue des composants cles de modeles anterieurs de recrutement de poissons en explorant les variations spatiotemporelles d'assemblages de larves de poisson en reponse a des facteurs d'influence cles predits dans un bassin versant australien tropical. Des donnees sur la composition et l'abondance de larves de poisson, ainsi que sur des variables hydrologiques, hydrauliques et reliees a l'habitat et a la nourriture ont ete recueillies sur une base mensuelle et bimensuelle pendant un an dans huit sites. Les variables qui predisent le mieux l'abondance et la diversite des larves de poisson sont determinees a l'aide d'arbres de regression stimules. Les predicteurs les plus souvent importants sont l'abondance de la microfaune, la complexite structurale des habitats et la temperature, des valeurs elevees de ces variables predisant une grande abondance et une grande diversite de larves de poisson. La diversite de larves maximum se produit quand le debit est le plus important, puisque plusieurs taxons frayant durant la saison humide sont cooccurrents avec des taxons au frai non saisonnier. Ces constatations appuient des modeles de recrutement generiques anterieurs, demontrant l'utilite de les inclure dans le recent modele Riverine Recruitment Synthesis Model et l'applicabilite de ce modele pour decrire des processus importants pour le recrutement des poissons de riviere tropicaux. [Traduit par la Redaction] Mots-cles : complexite des habitats, zooplancton, hydrologie, riviere Daly, Australie septentrionale, Introduction The early life stages of fishes are well established as being the most perilous, with development and survival of eggs and larvae largely controlling the strength of subsequent year [...]

Background: Despite advances in treatment, residual or recurrent tumors after definitive (chemo) radiotherapy for laryngeal and hypopharyngeal squamous cell carcinoma (SCC) remain a challenge in clinical management and require accurate and timely detection for optimal salvage therapy. This study aimed to compare the diagnostic value of Fluorine 18 (18F) fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) and diffusion‐weighted magnetic resonance imaging (DW‐MRI) in detecting residual or recurrent tumors after definitive (chemo) radiotherapy for laryngeal and hypopharyngeal SCC. Methods: A prospective study was conducted on 30 patients who presented with new symptoms after definitive (chemo) radiotherapy for laryngeal (n = 21) and hypopharyngeal (n = 9) carcinoma. Both 18F‐FDG PET/CT and DW‐MRI were performed and histopathologic analysis served as the standard of reference. Results: Histopathology showed 20 patients as positive and 10 as negative for tumors. 18F‐FDG PET/CT detected all tumors correctly but was falsely positive in one case. DW‐MRI detected tumors in 18 out of 20 positive patients and correctly excluded tumors in all negative patients. The sensitivity and specificity of 18F‐FDG PET/CT were 100% and 90%, respectively, while the values for DW‐MRI were 90% and 100%, respectively. Conclusions: The study concludes that 18F‐FDG PET/CT is slightly superior to DW‐MRI in detecting residual or recurrent tumors after definitive (chemo) radiotherapy for laryngeal and hypopharyngeal SCC. The combined use of 18F‐FDG PET/CT and DW‐MRI can potentially improve specificity in therapy response evaluation. [ABSTRACT FROM AUTHOR]

Anguillid eel populations are under threat globally. A particularly vulnerable life‐cycle stage is the migration of mature adult eels downstream from freshwater habitats through estuaries into the sea to spawn. This study investigated the factors associated with downstream migration of the short‐finned eel Anguilla australis (Richardson 1841) from a coastal wetland (Lake Condah) in south‐east Australia, using acoustic telemetry. Migration was associated with time of the year, higher water level and river flows, decreasing water temperature, and darker moon phases. Larger individuals and those in better condition were more likely to migrate from the wetland. Downstream migration peaked in spring, in contrast to the typical autumn migration period for other temperate anguillids. Variable responses, in comparison to other studies, highlight how migration cues may not be universal. In south‐east Australia, short‐finned eels may have evolved to migrate in multiple phases by first migrating to the estuary during typical seasonal spring flow pulses (e.g., to avoid being stranded in upland reaches during dry summer periods) and then migrating into the ocean in autumn. More research is needed to unravel these processes and causes, especially considering that the relationship between migration and hydrology may be complex and confounded (e.g., by human‐induced disruptions to migratory pathways). [ABSTRACT FROM AUTHOR]

Many animals exhibit partial migration, which occurs when populations contain coexisting contingents of migratory and resident individuals. This individual‐level variation in migration behaviour may drive differences in growth, age at maturity and survival. Therefore, partial migration is widely considered to play a key role in shaping population demography.Otolith chemistry and microstructural analysis were used to identify the environmental‐ and individual‐specific factors that influence migratory behaviour in the facultatively catadromous barramundi (Lates calcarifer) at two distinct life history stages: firstly, as juveniles migrating upstream into fresh water; and secondly, as adults or sub‐adults returning to the estuarine/marine spawning habitat.Monsoonal climate played an important role in determining the migration propensity of juveniles: individuals born in the driest year examined (weak monsoon) were more than twice as likely to undergo migration to freshwater than those born in the wettest (strong monsoon) year. In contrast, the ontogenetic timing of return migrations to the estuary by adults and sub‐adults was highly variable and not strongly associated with the environmental parameters examined.We propose that scarce resources within saline natal habitats during lower rainfall years may provide an ecological incentive for juveniles to migrate upstream, whereas more abundant resources in higher rainfall years may promote resident life histories within estuaries.We conclude that inter‐annual climatic variation, here evidenced by monsoonal strength, likely plays an important role in driving the persistence of diversified life histories within wild barramundi populations. [ABSTRACT FROM AUTHOR]