Gutless diet analysis

Posted on May 26, 2009

Working out the range of foods consumed by an animal population helps to clarify how it is supported by particular types of prey.  A standard way to collect dietary information is to examine the contents of predator guts, but because the feeding patterns of individuals are often quite flexible, many guts must normally be examined to obtain a reliable picture for the population as a whole.  A promising alternative approach, trialled through a study of the diets of perch and roach in a Finnish lake, is to use the fact that a predator’s body composition mirrors that of its prey.  In particular, variations in stable carbon and nitrogen isotopes across individuals should give an indication of the diet width for the whole population.  Unlike conventional diet analysis, this technique reflects the feeding history, rather than just the last meal, of each predator, so that accurate population-level information can be achieved with smaller sample sizes.  The researchers found that after mass removal of fish from the lake, isotope variances increased, presumably because the food spectrum expanded in response to the lower availability of fish prey.  The isotope variance of perch later contracted sharply, at a time that coincided with increased fish prey in the form of young-of-the-year perch and roach.

Reference:  Syvaranta, J. & Jones, R.  2008.  Changes in feeding niche widths of perch and roach following biomanipulation, revealed by stable isotope analysis.  Freshwater Biology 53, 425–434.

Posted in: fish, predation