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Where do baby moggies go?
Purple spotted gudgeons, or as I like to call them, "moggies" are a small colourful freshwater gudgeon. Aside from making great pets in aquaria, they are widespread throughout Australia and are an important component of the fish fauna in small streams of the wet tropics. We know very little about this species, and this extends to the early life history phases. In particular, we know nothing about how they recruit, and dispersal characteristics of early life history phase individuals. There are very few techniques that can be applied to early life history phase fishes to facilitate tracking, and many involve chemicals. Indeed, a new technique is called 'transgenerational marking', but has received limited development.
This study was published as part of my PhD. |
Mass-marking moggies
A larval fish otolith, after laser ablation mass spectrometry to examine the otolith core chemistry
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By injecting an adult female moggie with a dose of an enriched stable isotope of barium or strontium, her entire output of offspring can be mass-marked. The enriched stable isotopes permeate throughout the adult females' body, including her ovaries. At spawning, each egg contains a small amount of the isotope, which the developing embryo accumulates in the core of its earbone, which forms a few days after fertilisation. That enriched isotope remains in the otolith core indefinitely. By removing the otolith from the fish, and examining isotope ratios using a laser ablation system attached to a mass spectrometer, the enriched stable isotope can be detected. Thus, providing a link between the female injected, and her offspring. This technique paves the way for future studies exploring dispersal of Moggies in natural stream systems.
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Is it safe?
By injecting female fish with either enriched Ba137 or Sr87 or a combination of both, three unique markers can be produced to distinguish between populations of larval fish
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A key concern regarding marking techniques is whether they cause deleterious impacts on the marked individual. If they do, estimates of survival and dispersal will be biased, and to use such techniques unethical. To evaluate whether transgenerational marking is safe, I examined the growth and survival of larval fish marked with this technique, and compared them to non-marked fish. Happily, there are no deleterious impacts. Secondly, I performed an effects size meta-analysis, combining the findings of numerous studies that have investigated the impacts of transgenerational marking on fish health. I concluded that impacts were generally minimal, but more research is needed. Future studies should look to utilise a range of different isotopes to produce numerous batch markers to facilitate answering questions regarding movement ecology and evolutionary fitness in freshwater fishes across natural and experimental systems.
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Starrs, D., Davis, J.T., Schlaefer, J., Ebner, B.C., Eggins, S.M., and C.J. Fulton (2014) Maternally transmitted isotopes and their effects on larval fish: a validation of dual isotopic marks within a meta-analysis context. Canadian Journal of Fisheries and Aquatic Sciences 71: 387-397 doi: 10.1139/cjfas-2013-0416 LINK
