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Postmortem examination of a wild Lutjanus erythropterus exhibiting emaciation associated with multifactorial causes is presented. Skeletal muscle analysis for heavy metals revealed presence of threefold cadmium concentration in comparison with the European standards. Multifocal necrosis and muscle atrophy (condition factor K = 0.92) were also noted. Other anomalies recorded included abdominal distension and bilateral sunken eyes. The liver showed scant vacuolation, melano‐macrophage centres and diffuse granulomatous lesions also occurring in the viscera and mesenteries. Intensity of infection varied from 2 to 9 parasites, while 16S rRNA sequences revealed the opportunistic pathogen Photobacterium damselae complex only in affected organs. This is the first record of non‐aetiologic and aetiologic factors occurring concurrently in a wild fish in Oman. Although no definitive conclusions can be drawn, these findings highlight the urgent need for further fish health assessment regarding these pathologies and other diseases that pose a health risk to other fish species. [ABSTRACT FROM AUTHOR]

During 4 quantitative-systematic oceanographic cruises at 99 sampling stations in the Gulf of California (January and July 2007, August 2012, and June 2013), we found 2 trematode species (non-encysted mesocercaria stage) parasitizing the hemocoel of 2 krill species at near-shore locations. Copiatestes sp. parasitized Nematoscelis difficilis in January 2007, and Paronatrema mantae parasitized Nyctiphanes simplex in July 2007. Both trematode species had an intensity of 1 parasite per host. This is the first endoparasite known for N. difficilis, the first record of P. mantae infecting zooplankton, and the first confirmed trematode parasitizing krill species in the Gulf of California. We provide quantitative evidence that these 2 trematode species infect krill with considerably low station prevalence (0.03-0.16%) and low population abundances (<1.2 trematodes 1000 m(-3)). A review of trematodes parasitizing krill indicates that syncoeliid trematodes also have (with few exceptions) low population densities and prevalence and lower species diversity than previously thought (suggesting a broader zoogeographic distribution range of these parasites). Due to the low host specificity of syncoeliid trematodes that typically infect more than 1 secondary intermediate host species in their complex life cycle, we propose that N. simplex and N. difficilis are intermediate hosts (although non-conspicuous) for the transmission of syncoeliid trematodes in the Gulf of California.