Fishes: The Animal Answer Guide

7. Fish Foods and Feeding

87 What do fishes eat? Taking the 31,000-plus fish species worldwide, you could say that fishes eat everything. Some fish species are in fact omnivorous generalists, eating vegetation, insects, other fishes, detritus, zooplankton, you name it. Such generalist feeding habits help explain the amazing success of a few species that have been introduced in many places. Common Carp (Cyprinus carpio, Cyprinidae) and bullhead catfish (Ameiurus, Ictaluridae) are two freshwater examples. Many other fishes are opportunistic feeders, preferring certain foods but able to take advantage of what is available. Bluegill and Pumpkinseed Sunfish (Lepomis, Centrarchidae) eat zooplankton, aquatic insects, larval fish, snails, and just about any other animal that they can fit in their mouths. In contrast, many if not most fishes are more particular about what they can and will eat, specializing on certain food types. Their anatomies reflect these specializations. The freshwater cichlids of South America and Africa, numbering perhaps 2,000 species, include species that specialize on sponges, sediments, algae, leaves, mollusks, insects, phytoplankton, zooplankton , fish scales and fins, fish eyes, fish eggs and embryos, and other fishes. Their lips, gill rakers, and jaw and pharyngeal (throat) teeth are especially suited for their preferred food type. Across the 500-plus families of fishes, the catalog of unusual food types is long, with many surprising entries: •฀ One feeding type attacks parts of other fishes, such as scales and fins. Fin biters have sharp-edged teeth, whereas the teeth of scale eaters are Chapter 7 Fish Foods and Feeding 88 Fishes: The Animal Answer Guide often more file- or rasplike. Fin biters include young piranhas (Serrasalmus , Characidae) in the Amazon, saber-tooth blennies (Aspidontus, Plagiotremus ; Blenniidae) on coral reefs, many African cichlids, some Asian barbs (Puntius, Cyprinidae), freshwater pufferfishes (Tetraodon, Tetraodontidae ), and bumblebee gobies (Brachygobius, Gobiidae). Scale eaters include several African cichlids and leatherjackets (Oligoplites, Carangidae ) on coral reefs. Cookie-cutter sharks (Isistius) sneak up on tuna, marlin, and dolphins and take a single, circular, half-dollar size plug out of their victim’s sides. Unfortunately, several of these so-called “partial consumers” are also popular aquarium fishes, causing no end of headaches for aquarists. •฀ A number of fishes both in marine and fresh water pick parasites from the body, mouth, and gills of other fishes. Specialist cleaners include the cleaner wrasses (Labroides, Labridae), remoras (Echeneidae), and some butterflyfishes (Chaetodon) in the tropical Pacific, and neon gobies (Gobiosoma) in the tropical Atlantic (see “Are fishes social?” in chapter 4). Many other fishes pick parasites part-time, otherwise feeding more generally on small invertebrates (juvenile damselfishes, angelfishes, butterflyfishes , surfperches, wrasses, and centrarchid sunfishes). •฀ Fishes in many habitats feed on the feces of other fishes, an activity called “scatophagy” or “coprophagy.” Scats (Scatophagus), a popular Asian aquarium fish, get their scientific name from this behavior. Large Labeo minnows in Africa accompany hippos, using their excrement as a constantly supplied food source. Coprophagy is common on coral reefs. A study in Palau, Western Caroline Islands, found 45 different species of reef fishes from eight families (mostly sea chubs, damselfishes, wrasses, rabbitfishes, surgeonfishes, and triggerfishes) eating feces from 64 fish species in 11 different families, preferring the feces of planktivores over waste products from herbivores. Madagascar cichlids are considered to be ancestral to the incredibly diverse cichlids of continental Africa, with their equally diverse feeding habits. Unfortunately, the Pinstripe Damba cichlid (Paretroplus menarambo ), such as this one. are extinct in the wild, but the species is kept going through captive breeding. 89 Fish Foods and Feeding •฀ A few fishes specialize on, or at least supplement their diet with, the eyes of other fishes. A narrow-bodied cichlid in Lake Malawi, called the Malawi Eyebiter (Dimidiochromis) does not make a good aquarium fish because of its eye-popping activities. A North American cyprinid, the Cutlip Minnow (Exoglossum maxillingua) will also remove eyes from its tankmates. •฀ Some African cichlids specialize in attacking female cichlids that are carrying young in their mouths (see “Do fishes care for their young?” in chapter 6). These babynappers repeatedly ram the head of the mother until she spits out a few young, which are then snapped up by the predator . More usual food types include small plants or animals in the water column (phytoplanktivores and zooplanktivores), other fishes (piscivores), plants (herbivores), and detritus (detritivores). Many fishes that normally feed on live prey will not hesitate to scavenge on dead things. Fishes that swim above the bottom and...