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Feeding behaviour of larval greenback flounder Rhombosolea tapirina


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Cox, Elizabeth S 1997 , 'Feeding behaviour of larval greenback flounder Rhombosolea tapirina', Research Master thesis, University of Tasmania.

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Understanding the feeding behaviour of larval fish is critical for determining optimal
management protocols in aquaculture and understanding larval prey selectivity patterns of
wild fish populations. This study examined the feeding performance of cultured greenback
flounder larvae Rhombosolea tapirina, using the live feed organisms Brachionus plicatilis
(rotifers), and Artemia sp., to determine the primary sensory modality involved in feeding,
the relationship between mouth dimensions and prey size selected, and the effect of
previous exposure to a prey species on subsequent prey selection. The proportion of
larvae that fed on rotifers in the light (light intensity of 5-6 µmol.m-2 .s-1 ), increased
significantly from 66% to 96% from day 12 to day 27 post-hatching, respectively. In
comparison, the proportion of larvae that fed on rotifers in total darkness (0 µmol.m-2 .s-1 )
never exceeded 5% during the same period. This indicated that greenback flounder larvae
were primarily dependent upon vision (a light dependent behaviour) to feed, with a lesser
reliance upon non-visually mediated detection of prey. Internal horizontal dimensions of
the mouth of greenback flounder larvae determined from serial histological sections, increased in a linear fashion with both increasing body size and age of larvae. Examination
of the ratio of Artemia prey size (total length, carapace width, and carapace width with
appendages) to larval mouth width, suggested that prey carapace width, not prey width
with appendages, or prey length, limited the size of prey ingested, indicating that larvae
must visually orient to ingest the prey head-on. When greenback flounder larvae were
offered one of three discrete size fractions of Anemia prey, both prey size and larval age
significantly effected larval feeding response. On days 12 - 17 post-hatching, larvae
ingested Artemia prey of a single size range (100 - 200 µm screened size), which was
considerably smaller than they were capable of ingesting. From 19 - 20 days of age and
thereafter, there was a marked change in feeding performance, with larvae able to ingest all
three Artemia prey size ranges offered (100 - 200 µm, 300-390 pm and 450 - 560 µm
screened size, respectively), probably reflecting an ontogenetic increase in larval sensory
capability, swimming speed and prey handling ability. Prior feeding experience of
greenback flounder larvae to either rotifers only (Rotifer Treatment) or a mixed diet of
Artemia and rotifers (Artemia and Rotifer Treatment), significantly effected subsequent prey selection when larvae were offered a mixed diet of Artemia and rotifers, but did not
effect the temporal onset of selection of the novel prey species (Artemia) by Rotifer
Treatment larvae. Therefore the differences in prey selection by larvae with or without
prior exposure to Artemia prey, was not due to the inability of larvae to handle and ingest
a novel prey species, but reflects positive selection for familiar prey species. The latter
indicates a learned component in the feeding behaviour of fish larvae. This has
implications for the timing of the introduction of new live prey species during intensive
culture of marine fish larvae.

Item Type: Thesis - Research Master
Authors/Creators:Cox, Elizabeth S
Keywords: Flatfishes
Copyright Holders: The Author
Copyright Information:

Copyright 1997 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (M.App.Sc.)--University of Tasmania, 1998. Includes bibliographical references

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