Gut fluorescence technique to quantify pigment feeding in Downs herring larvae

Mestre, Julie (2018) Gut fluorescence technique to quantify pigment feeding in Downs herring larvae. Marine Ecology Progress Series, 607, 129-142. (doi:10.3354/meps12775).

Abstract

The ingestion of chlorophyll pigments (chlorophyll a and phaeopigments) by Downs
herring Clupea harengus larvae (8−13 mm) collected in the English Channel and the North Sea
during winter 2014 (International Bottom Trawl Survey) was quantitatively estimated via gut fluorescence analysis, a method classically used for copepods. Our results confirmed the consumption of chlorophyll pigments either directly, or indirectly through the consumption of herbivorous
copepods. Higher mean pigment ingestion rates were observed for small larvae (8−11 mm, 52 ±
51 [SD] ng chl a eq. ind.−1 d−1), whereas lower mean rates (43 ± 48 ng chl a eq. ind.−1 d−1) were
measured in larger larvae (12−13 mm). This decrease in the rate of pigment ingestion coincided
with an ontogenetic shift in prey preference that occurred at 12−13 mm. Chlorophyll pigment
ingestion covered on average up to 18% of the daily metabolic needs of 8−13 mm herring larvae
and thus constitutes a non-negligible part of the larval diet mainly during the first feeding stages.
Direct ingestion of autotrophic protist prey primarily involved small larvae (8−11 mm, 73 ± 38 to
84 ± 34%), as it can synergistically increase digestion efficiency of other prey items (e.g. copepods). The gut fluorescence method applied to fish larvae provides a global estimate of total
ingested pigments and a snapshot of their diets. As a fast and easy method, it should be deployed
in future surveys to compare food intake (ingestion) in different areas, and to quantitatively assess
the nutritional status of fish larvae in the field.

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Contributors

Author: Julie Mestre

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