Fish stomach or fish gut content analyses refer to methods of analyzing fish diet through assessment of materials found in dissected fish stomachs. Fish stomach contents are typically assessed in terms of mass and/or volume, and then prey items are identified by taxonomists, enumerated, assessed for their state of digestion, and measured or weighed, as necessary.
Fish diet and ecology are highly variable among different fish taxa, and can vary among developmental stages for a single fish as well. Fish stomach contents can therefore be used to identify differences in fish feeding strategies, fish health, habitat-related food availability, as well as to gather information regarding the trophic relationships in aquatic communities. Analyses of fish stomach contents are particularly important to understanding fish ecology and health due to the difficulties associated with observing fish feeding habits ‘in vivo’ (in their natural habitats).
Fish stomach size can vary with body size and among taxa, and likewise, fish prey preference can vary throughout development for a single fish, can vary among habitats for a single species, and can vary particularly among taxa. Fish stomachs analyzed at Biologica typically vary between 1 and 10cm and common prey items include macroinvertebrates, microinvertebrates, icthyoplankton, and fry.
Fish stomachs are either dissected from fish in the field and preserved in formalin (preferred), or intact fish may be shipped frozen.
Because fish stomach analysis can be utilized to gather information regarding fish community and prey community ecology, fish stomach analysis is a tool commonly utilized in biomonitoring studies as a means of assessing fish habitat and fish health. For example, in the event that a benthic community might be disrupted due to development or dredging, fish preying on those organisms may be affected and thus monitoring fish stomach contents could allow researchers to monitor the effects of development on both the benthic community and fish diet.