Following a brief review of their biology, this contribution is an attempt to provide a global overview of the catches of mesopelagic fishes (of which 2.68 million tonnes were officially reported to the FAO) throughout the world ocean from 1950 to 2018, to serve as a baseline to a future development of these fisheries. The overview is based on a thorough scanning of the literature dealing with commercial or experimental fisheries for mesopelagics and their catches, and/or the mesopelagic bycatch of other fisheries. All commercial (industrial and artisanal) fisheries for mesopelagic fishes were included, as well as experimental fisheries of which we were aware, while catches performed only to obtain scientific samples were omitted. The processes of generating bycatch and causing discards are discussed, with emphasis on Russian fisheries. From peer-reviewed and gray literature, we lifted information on mesopelagic fisheries and assembled it into one document, which we then summarized into two text tables with catch data, one by country/region, the other by species or species groups.

BackgroundDespite their importance as vectors of zoonotic parasites that can impact human and animal health, Culicoides species distribution across different habitat types is largely unknown. Here we document the community composition of Culicoides found in an urban environment including developed and natural sites in east central Texas, a region of high vector diversity due to subtropical climates, and report their infection status with haemoparasites.ResultsA total of 251 individual Culicoides were collected from May to June 2016 representing ten Culicoides species, dominated by C. neopulicaris followed by C. crepuscularis. We deposited 63 sequences to GenBank among which 25 were the first deposition representative for six Culicoides species: C. arboricola (n = 1); C. nanus (n = 4); C. debilipalpis (n = 2); C. haematopotus (n = 14); C. edeni (n = 3); and C. hinmani (n = 1). We also record for the first time the presence of C. edeni in Texas, a species previously known to occur in the Bahamas, Florida and South Carolina. The urban environments with natural area (sites 2 and 4) had higher species richness than sites more densely populated or in a parking lot (sites 1 and 3) although a rarefaction analysis suggested at least two of these sites were not sampled sufficiently to characterize species richness. We detected a single C. crepuscularis positive for Onchocercidae gen. sp. DNA and another individual of the same species positive for Haemoproteus sacharovi DNA, yielding a 2.08% prevalence (n = 251) for both parasites in this species.ConclusionsWe extend the knowledge of the Culicoides spp. community in an urban environment of Texas, USA, and contribute to novel sequence data for these species. Additionally, the presence of parasite DNA (Onchocercidae gen. sp. and H. sacharovi) from C. crepuscularis suggests the potential for this species to be a vector of these parasites.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-3283-9) contains supplementary material, which is available to authorized users.

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The prevailing determinant of maturation in fishes is thought to be a redirection of energy from growth to reproduction. Instead, the Gill Oxygen Limitation Theory predicts that maturation, and thus reproduction, is induced when a fish reaches a critical ratio of oxygen supply to demand (Qm/Qmaint). The consistency of this critical ratio has been previously documented in many fishes, but a broader test was lacking. In this study, the authors assess if this critical ratio is consistent across 132 unique fish species, as measured by the slope of the relationship between LmaxD and LmD, where Lmax is the maximum length reached in a given population, Lm is the mean size at first maturity in that population and D is a gill‐related exponent which renders the LmaxD/LmD ratio equivalent to the Qm/Qmaint ratio. The authors found that across all species, the LmaxD/LmD ratio was 1.40 (95% c.i. 1.38–1.42), which was not significantly different from that previously estimated across other species groups (1.35, 95% c.i. 1.22–1.53), especially when phylogenetic relationships were considered (1.25, 95% Bayesian credible interval 1.09–1.40). The consistency of the LmaxD/LmD ratio across taxa, which expresses the difference in metabolic rate at maturity and maximum size, suggests that the scaling of gill surface area is the factor that underlies this ratio, and which triggers the maturation in fishes.

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