The FOOD ITEMS Table

The FOOD ITEMS table highlights from a set list, the food items reported to be consumed by a particular fish species. Clicking on any of the highlighted food items (under the Food II field) leads, via a list, to the FOOD ITEM DETAILS, with information on the Food group, Food name, Stage/part, Commonness of the food item, Country where the sample was obtained and a Remarks field.

Food items define predator-prey relationships

A compilation of different food items consumed by a fish species can be used to identify staple food preferences in various fish species for which detailed diet composition data are not available, and in preliminary estimates of trophic level (see Boxes 23, 24 and 25).

The information contained in the FOOD ITEMS table is useful in defining predator-prey relationships among fishes.

Box 24. Hierarchy of food items.

To standardize the fields of the trophic ecology tables in FishBase, a hierarchy of food items was created. This refines choices from Food I (6 choices), via Food II (22 choices) to Food III (55 choices). The hierarchy is as follows:

Food I Food II Food III
Detritus detritus debris; carcasses
plants phytoplankton blue-green algae; dinoflagellates; diatoms; green algae; n.a./other phytoplankton
  other plants benthic algae/weeds; periphyton; terrestrial plants
zoobenthos sponges/tunicates sponges; ascidians
  cnidarians hard corals; n.a./other polyps
  worms polychaetes; n.a./other annelids; non-annelids
  mollusks chitons; bivalves; gastropods; octopi; n.a./other mollusks
  benthic crustaceans ostracods; benthic copepods; isopods; amphipods; stomatopods; shrimps/prawns; lobsters; crabs; n.a./other benthic crustaceans
  insects insects
  echinoderms sea stars/brittle stars; sea urchins; sea cucumbers; n.a./other echinoderms
  other benthic invertebrates n.a./other benthic invertebrates
zooplankton jelly fish/hydroids jellyfish/hydroids
  planktonic crustaceans planktonic copepods; cladocerans; mysids; euphausiids; n.a./other planktonic crustaceans
  other planktonic invertebrates n.a./other planktonic invertebrates
  fish (early stages) fish eggs/larvae
nekton cephalopods squids/cuttlefish
  finfish bony fish
    n.a./other finfish
others herps salamanders/newts; toads/frogs; turtle; n.a./other reptiles
  birds sea birds; shore birds; n.a./other birds
  mammals dolphins; pinnipeds; n.a./other mammals
  others n.a./others
The FOOD ITEMS table should be consulted for the trophic levels assigned to these various groups.
    Maria Lourdes D. Palomares, Pascualita Sa-a and Daniel Pauly
 
Sources

More than 800 references have been used in the FOOD ITEMS table. Among these are Hiatt and Strasburg (1960), Randall (1967), Scott and Crossman (1973), Allen (1985), Randall (1985), Whitehead (1985), Hickley and Bailey (1987), Maitland and Campbell (1992) and Sierra et al. (1994).

Verification of the more than 16,000 records, covering over 4,000 species, in the FOOD ITEMS table was done by checking the taxonomic affinities of the food items. Because some animal groups utilized as food occupy various habitats, inconsistencies occurred in the functional classification of certain food items; examples are the cyclopoid copepods, which, unless otherwise specified, may include both planktonic and benthic forms. In these cases, we deduced the functional group of a food item from the habitat and behavior of the species that consume it, pending further verification.

Fields
 
 
 
 
 
 
We assigned trophic levels to food items

To standardize the entries in the FOOD ITEMS and related trophic ecology tables, a hierarchical structure was created with three levels of precision (Food I, Food II and Food III) for the entries (Box 24). The lower levels of this structure can be viewed by double-clicking on any Food I buttons of the FOOD ITEMS table. This opens the FOOD TROPHS table, which presents, for each food level, estimates of Trophs (+/- s.e.), thus enabling computation of trophs in fish whose diet composition is known (see Box 25). The sources of the troph estimates are given in a Reference field, with a Remark field providing additional information. In cases where the troph was estimated from the troph of other groups, this is indicated in the Remarks field, and no source ref. is given.

Food I indicates broad food groups that are consumed. The Food II buttons, when highlighted, may be clicked to display a list of Food III items available under the respective Food II category. Double-clicking on any item in this list displays the respective FOOD ITEM DETAILS window, with information on Food III presented through the following details:

  • The Food group field, which refers to the family (or higher order group) or common name of a food item;

  • The Food name (text) field refers to the scientific name of the food item, if specified;

  • The Commonness field refers to the percentage of specimens containing the food item, as percentage and as choice, i.e., rare (1-5%); common (6-20%); very common (21-50%); dominant (>50%). But see discussion on frequency data in the DIET table);

  • The food item is further defined in terms of the stage consumed (Prey stage/Part); the choices provided are appropriate subsets of the following list: eggs; larvae/pupae; recruits/juv., juv./adults; adults; n.a./others (for animal food); and roots; stem; leaves/blades; fruits/seeds; n.a./others (for plant food);
Box 25. Estimating trophic levels from individual food items.

As documented in Box 23, trophic levels (‘trophs’) are typically estimated from diet composition data, covering the whole range of food items consumed by a given species at a given locality and season (see the DIET COMPOSITION table). A troph (and its s.e.) can then be estimated, from the mean trophic level of the preys, plus one.

It is also possible to obtain rough estimates of the troph and its s.e. based on individual prey items (rather than a complete diet composition), as recorded in the FOOD ITEMS table, granted that enough food items have been entered for a given species, and that one is willing to accept certain assumptions on the relative importance of these food items in the overall diet of the species.

Examination of diet compositions entered until mid-1999 (n = > 1,800) showed that typically, the relative contribution of different food items to the overall diet composition follows a pattern described by the empirical model:

log10P = 2 – 1.9log10R – 0.161og10G                                             …1)

where   P is the contribution of an item to the total diet in percent;

             R is the rank of the food item (in terms of its relative contribution to the total diet); and

             G is the number of food items (in the DIET table, we always have 1 < G < 10).

In the following, a description of the resampling routine is provided which is used in FishBase to estimate trophs and their s.e. from individual food items. This routine involves three cases:

Case 1: all food items are plants or detritus

Then: troph = 2.0 and s.e. = 0;

Case 2: there is only one food item, and it is neither a plant nor detritus.

Then: troph = 1 + troph of food item & s.e. = s.e. of food item (see FOOD ITEMS table for trophic levels and s.e. of food items; use Food III if possible, or else Food II or else Food I).

Case 3: There are several food items, and at least one is not a plant or detritus.

Then: run Routine A.

Routine A

Count the food items, and call their number G;

Select at random one of these food items, and give it the rank 1 (R = 1);

Given G, and R, solve equation (1) for P;

Select at random one of the remaining food items, give it a rank of 2 (R = 2) and again solve equation (1) for P;

Repeat (2) – (4) until all items have been selected (R = 3, 4 . . . . G);

From the P values, and the trophs specific to each items, estimate a mean troph from:

                                                       … 2)

Compute s.e. of Troph from Sachs (1984)

             … 3)

Save troph and s.e.; repeat (2) – (8), using different random numbers to select first, second, etc. item; stop after 100 loops.

Take grand mean of computed trophs and of their standard errors, output these and stop.

The key point of this routine is that the grand mean s.e. that is estimated considers all possible permutations of the food items in terms of the relative abundance they could have had in a real diet composition. Note that the standard errors and corresponding troph estimates obtained from this routine are tentative, and should be replaced by estimates from diet compositions whenever possible.

Reference

Sachs, L. 1984. Applied statistics. A handbook of techniques. 2nd ed. 707 p. Springer-Verlag, Inc., New York.

Daniel Pauly and Pascualita Sa-a
 

  • The stage of the fish having consumed the above items (Predator stage) may consist of the following choices: larvae; recruits/juv., juv./adults (used as default for cases where the predator stage is not available); adults;

  • The Remarks field refers to a food item that cannot be classified under any of the choices given above. Comments relating to the food item, e.g., size, sex and age may also be provided.

Box 26. Preliminary estimation of trophic levels in fish species without food composition data.

FishBase 2000 includes new routines requiring estimates of trophic level (‘troph’) for all species in an ecosystem, including species for which diet composition¾ from which trophs are usually estimated¾ are lacking. As these routines aggregate data from a large number of species, approximate troph estimates can be used, as long as their central tendency remains realistic.

The approach chosen to estimate trophs for species without food information relies (1) on the demonstrated similarity of trophs in taxonomically related species (see data in ECOLOGY table), and (2) on the equally well established relationship between body size and trophic level, anchored in a value of troph = 3.0 for larvae of about 1 cm (see Fig. 36).

The procedure implementing this approach works as follows:

for species without troph estimates in the ECOLOGY table, identify the nearest relative(s) with troph estimates in the same genus; if none is available, use a troph from the same subfamily. If none is available (or a subfamily is not defined in FishBase), use a troph from the same family. If none is available, use a troph from the same order (all orders in FishBase have at least two species with troph estimate based on field data).

Estimate (mean) slope(b) for data pair(s) in (1) and the equation , where is the mean length in the unexploited population, estimated from , derived from (Pauly and Soriano 1986)a, when the length from which is computed using L’ = 0, and M/K = 2.

Using mean slope obtained in (3) and the for the species with troph, compute new troph from

The trophic level estimates obtained in this fashion are stored separately from the observation-based values in the ECOLOGY table, in a new table called ESTIMATES. Continuous updating of FishBase will ensure that the troph and other estimates in that table are over-written as soon as observation-based values become available. (Users of the CD-ROM version of FishBase 2000 should visit the Internet version of FishBase for latest updates).

Reference

Pauly, D. and M. Soriano. 1986. Some practical extensions to Beverton and Holt’s relative yield-per-recruit model, p. 491-495. In J.L. Maclean, L.B. Dizon and L.V. Hosillos (eds.) The First Asian Fisheries Forum. Asian Fisheries Society, Manila.

__________________

aNote that this equation is also used to derive the troph estimates in the ECOLOGY table that refer to the unexploited stock.

Daniel Pauly and Maria Lourdes Palomares

 


Fig. 36. Relationship between trophic level (troph) estimates and body length (in cm) in 180 species of fishes. The regression lines (forced through the origin, representing larvae with troph = 3, and length » 1 cm) have slopes of ba = 0.24 for first-order carnivores (dotted line and open dots, representing herring and other small pelagic and demersal fishes); and bb = 0.63 for higher-order carnivores (solid line and full dots, representing cod-like and other large piscivorous demersal and pelagic fishes). Adapted from Pauly et al (2001).

How to get there

You get to the FOOD ITEMS table by clicking on the Biology button in the SPECIES window, the Trophic Ecology button in the BIOLOGY window and the Food Items button in the TROPHIC ECOLOGY window. You get to the FOOD TROPHS table by doubleclicking on the Food I buttons of the FOOD ITEMS window. You get to the FOOD ITEM DETAILS window by clicking on the highlighted Food II buttons of the FOOD ITEMS window.

Internet

In the Internet, you find the FOOD ITEMS table if you click on the Food Items link in the ‘More information’ section of the ‘Species Summary’ page. You can create a list of species for which food data are available by selecting the Food Items radio button in the ‘Information by Topic’ section of the ‘Search FishBase’ page.

References

Allen, G.R. 1985. FAO species catalogue. Vol. 6. Snappers of the world. An annotated and illustrated catalogue of lutjanid species known to date. FAO Fish. Synop. 6(125):208 p.

Hiatt, R.W. and D.W. Strasburg. 1960. Ecological relationships of the fish fauna on coral reefs of the Marshall Islands. Ecol. Monogr. 30(1):65-126.

Hickley, D. and R.G. Bailey. 1987. Food and feeding relationships of fish in the Sudd swamps (River Nile, Southern Sudan). J. Fish Biol. 30:147-159.

Maitland, P.S. and R.N. Campbell. 1992. Freshwater fishes of the British Isles. Harper Collins Publishers, London.

Pauly, D., M.L.D. Palomares, R. Froese, P. Sa-a, M. Vakily, D. Preikshot and S. Wallace. Fishing down Canadian aquatic food webs. Can. J. Fish. Aquat. Sci. 58:51-62.

Randall, J.E. 1967. Food habits of reef fishes of the West Indies. Stud. Trop. Oceanogr. Miami 5:665-847.

Randall, J.E. 1985. Guide to Hawaiian reef fishes. Harrowood Books, Newtown Square, Pennsylvania. 74 p.

Scott, W.E. and E.J. Crossman. 1973. Freshwater fishes of Canada. Bull. Fish. Res. Board Can. 184, 966 p.

Sierra, L.M., R. Claro and O.A. Popova. 1994. Alimentacion y relaciones tróficas, p. 263-284. In R. Claro (ed.) Ecología de los peces marinos de Cuba. Instituto de Oceanología Academia de Ciencias de Cuba by Centro de Investigaciones de Quintana Roo, Mexico.

Whitehead, P.J.P. 1985. FAO species catalogue. Vol. 7. Clupeoid fishes of the world. An annotated and illustrated catalogue of the herrings, sardines, pilchards, sprats, anchovies, and wolf herrings. Part I. Chirocentridae, Clupeidae, and Pristigasteridae. FAO Fish. Synop. 7(125)Pt. 1:303 p.

Pascualita Sa-a, Maria Lourdes D. Palomares and Daniel Pauly