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Diets of NW Atlantic fishes and squid


This page provides diet composition data for 174 species of fish and squid, based on over 123,000 stomach samples collected by the National Marine Fisheries Service between 1973 and 1990 during annual Bottom Trawl Surveys. These surveys were conducted each spring and fall, and occasionally summer and winter, between Cape Fear, North Carolina and Nova Scotia. I provide over 1,000 pie charts and extensive tabular summaries of diets based on data from 1973-80 and 1981-90 separately due to extreme differences in sampling and data processing methods. I STRONGLY discourage anyone from combining these data sets for any analyses, except when prey are lumped to the highest taxa levels (e.g., fish, polychaets, echinoderms, etc.). Do not attempt to examine long term trends in predation on fishes by combining these data sets! During 1973-80, stomach samples were preserved in the field and later processed in the laboratory. Prey weights were recorded to the nearest 0.01 grams. Tables for 1973-80 summarize the diets of 152 species, based on 40,000 samples.   During 1981-90 stomach samples were processed at sea where prey volumes to the nearest 0.1 cc were estimated. Tables for 1981-90 summarizes the diets of 117 species, based on 83,693 samples.  Besides differences in prey measurement units, basic differences in the likelihood of prey identification at specific taxon levels make comparisons among these periods difficult. Invertebrate prey were identified more accurately, and to lower taxonomic levels in the laboratory processed samples (1973-80). In contrast, fish prey were more accurately identified to species, while most invertebrates were identified only to higher taxonomic levels in the field processed samples (1981-90). Consequently, comparisons between these two periods are biased by differences in the probability of identification and should be done cautiously. Throughout the data you will see much lower diversity of fish prey in the 1973-80 data set compared to the 1981-90 data. You will also notice that for most species, predation on fish prey is much greater during the 1981-90 period simply because the fish prey were more likely to be identified.

Scientific and common names of fishes and invertebrates referred to in the following text, tables and charts are based on the American Fisheries Society's standardized names lists whenever possible.  To retrieve tabular data on a species first allow the table to fully load into your browser, then do a text search on the scientific name of the species you are interested in using your browser's FIND or SEARCH option.  Note that some species occur as both predator and prey. To obtain data on the diet of a predator, repeat the search until you find the species listed as a predator in the table heading. Alternatively, to find all predators of a given prey, continue repeating the search until you find all the occurrences of the species within the predator diets. Note, you may want to avoid printing these tables from your browser, as many of them are several hundreds to several thousand of pages long. Instead, you may wish to download the table, or to cut-and-paste sections of interest.

 Tables currently provided

Species list, sample sizes, and predator length statistics



Predator Diet Composition

   All data pooled



   By season



   By year



   By 10 cm length class



   By Geographic area



   By season and geographic area



Predator identification

   All predators of Prey



Both time periods
   All Predators of Fish Prey1
Variable definitions for fields found in the above tables can be found at reptvars.htm

1Table fishpds.txt is sorted by prey phylogeny, and by predator scientific name within each prey. Use your browser's find bottom to search for prey by its scientific name or AFS common name in uppercase (e.g. find 'PYSCINAM=PARALICHTHYS DENTATUS'). Use repeat find on substrings to find prey with similar names (e.g. 'PYSCINAM=PARALICHTHYS' would find both summer flounder and fourspot flounder). Variables are the same as in reptvars.htm, except data for 1973-80 and 1981-90 are denoted by 'a' and 'b' suffixes, respectively. Higher taxa prey refer to unidentified prey of that group, for example PYSCINAM=FISH refers to unidentified fish prey. Its statistics do not include fish prey identified to lower taxa. To find all predators of clupeids, search for PYSCINAM=CLUPEIDAE, then scroll down the page further to find predators of any clupeid prey identified to genus or species.


Graphs currently provided:


Pie charts

Over 1,000 pie charts of the diets of 71 species of fish and 2 squids are provided on this web site. These charts are based on the data presented in the tables listed above. Pie charts are only provided for species with at least 20 stomach samples in a given grouping.

Pooled data - these pie charts are of all samples pooled for each time period.


Pies grouped by category - Thumbnail gallery of pies for each species by different grouping categories.

1973-80 time period

Pies based on mean prey weights

Pies based on mean percent prey weights (I recommend this as the least biased diet composition index, at least for the 1981-90 period).


1981-90 time period

Pies based on mean prey volumes

Pies based on mean percent prey volume (I recommend this as the best diet composition index for this data).


Click here for graphs of ontogenetic changes in diet for 32 major fish and 2 squid species: Ontogenetic changes

Additional information can be found in a summary of ontogenetic changes from a (paper in preparation on this topic).



Trophic Studies

Brief descriptions of my research activities can be found on the following pages.

2. Seminar describing the diet and ecology of summer flounder, Paralichthys dentatus.

3. Seminars describing fish diets and guild structure in the Gulf of Maine.

4. Some preliminary summary statistics of goosefish, Lophius amerianus, diets, based on the NMFS bottom trawl surveys.

5. Predator guild structure in five geographic areas of the NW Atlantic.

6. Ongoing study of ontogenetic shifts in diet by NW Atlantic fishes.

7. Studies of predator-prey size relationships.

8. Largely unsuccessful attempt to use NMFS data to examine temporal shifts in trophic structure

This page was last modified on November 13, 2007

Copyright © 1999, 2007 by Rodney Rountree. All rights reserved

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