Tyler Winter

Comp 3150


Proposed Method for Stomach Content Analysis for Lake Herring, Bloater and Kiyi



In order to determine and compare the diets of herring, bloater and kiyi we will identify, count, and weigh the items in their stomachs. Below is the method that I propose to use for this analysis.



  1. Sampled fish will be weighed, measured and frozen.


  1. Later, fish will be thawed, and the stomachs removed and preserved in 70% alcohol.


  1. Stomach contents will be placed into a watch glass for sorting under a dissecting scope.


  1. The first 100 items will then be identified; macroinvertebrates will be identified to the genus level when possible. Items will be sorted into separate categories (Cx) and the number of items in each category will be recorded (Cc).


  1. Each category and the unidentified items will be placed in separate tared weigh pans and dried at 90c for 2 hours and weighed.


  1. The dry mass of each category (MCx) will be divided by the number of items (NCx) to calculate the mean dry mass for an item (M/NCx).


  1. The MCx of each category will be summed to get the mass of all the sorted items (Ms). MCx when divided by Ms will equal the percentage that each category contributes to the dry mass (PCx). MCx/ Ms = PCx


  1. Ms will be added to the dry mass of the unsorted items (Mu) to equal the dry mass of the stomach contents (Mt). PCx will be multiplied by Mt to estimate the mass of each category in the stomach (TCx). TCx will be pooled for all individuals within a species and used to compare diets between species.




This process will allow me to efficiently analyze the stomach contents of fish by simplifying the counting, sorting and identifying of stomach contents. The data gained will be essential for understanding the ecology of herring, bloater, and kiyi.




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