PFK Fishnews: Catfish and characin feed together

[AquaticQuotient.com]

Catfish and characin feed together

Scientists from Brazil have discovered an unusual feeding association between a small loricariid catfish (Parotocinclus maculicauda) and an undescribed species of darter tetra (Characidium sp.). Publishing their results in the latest issue of the journal Neotropical Ichthyology, Rafael Leitão, Érica Caramaschi and Jansen Zuanon report a case of the nuclear-follower association in an Atlantic forest stream in southeastern Brazil.

The nuclear-follower association is an interspecific interaction defined by the presence of a nuclear species that promotes a disturbance during foraging and a follower species that feeds on the items exposed or flushed out by the former.

The authors performed in situ diurnal observations of the association between Parotocinclus maculicauda and Characidium sp. while snorkeling in the do Ouro River, a fourth order tributary of the São Pedro River, Macaé River drainage. The sample site was bordered by secondary Atlantic forest, and is a clear-water stream with rocks, logs and dead leaves scattered over a sand-bottomed substrate. The stream was less than a metre deep and 3–10 m wide.

According to the authors: “The association was registered only when both fish species were positioned on a rocky substrate (large rocks up to 1m in diameter) covered by periphyton and a fine sediment layer, in areas of high water flow (current speed up to 50cm/s at the stream bottom).

“Individuals of the minute catfish P. maculicauda were observed grazing singly or in groups on periphytic algae attached to the rocks, making head and body movements over short distances ahead and sideways during foraging...When foraging the catfish occasionally drifted downstream for a short distance displaced by the water flow, but quickly resumed its position.

“This activity set frequently suspended the sediment deposited on the rock surface, resulting in small clouds of particles drifting away and quickly dispersing by the fast flowing water. The feeding association was characterized by the presence
of a single individual of Characidium sp. standing downstream of, and in close proximity (ca. 5cm) with the foraging catfish.

“At this position, the darter adopted a sit-and wait foraging tactic...and fed on particles suspended by the grazing activity of the catfish...The nuclear-follower interaction lasted between a few seconds to about five minutes and each of these events occasionally occurred more than once during the 40 min observation session.

“Although we observed a ratio of one individual of Characidium sp. to about 15 P. maculicauda, feeding association events comprised almost always only one individual of each species. However, we observed a single case of one individual of the darter alternately following two closely positioned catfishes.”

The authors hypothesize that the feeding association “...possibly occurs because the two species occupy similar micro-habitats, and forage during the same daytime period.”

They also note that the nuclear-follower association is common in marine fishes (e.g. many reef species), but relatively rare in freshwater fishes.

For more information, see the paper: Leitão, RP, ÉP Caramaschi and J Zuanon (2007) Following food clouds: feeding association between a minute loricariid and a characidiin species in an Atlantic forest stream, southeastern Brazil. Neotropical Ichthyology 5: 307–310.


Full article by Ng Heok Hee here...

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