Contribution of macro- and micro-consumers to the decomposition of fish carcasses in low-order streams: an experimental study

Abstract

Vertebrate carrions, in particular fish, can provide a significant source of organic matter to lotic systems. Most studies related to animal matter degradation have been undertaken in Western North America, where entire lotic networks depend on large masses of anadromous salmonids, but less is known of other aquatic environments. In this study, the decomposition process of trout was analyzed in a Northern Italian stream, investigating the different importance of macro (invertebrates)—and micro (fungi)—consumers. Trout carcasses exhibited an exponential mass loss over time and attracted a rich community of microbic and invertebrate colonists. Final values for fish decay were significantly affected by the presence of macro-consumers; nevertheless, the role of macroinvertebrates seems to be not as predominant as in other ecological systems. Our study indicates that in lotic environments, which lack specialized necrophagous or sarcophagous invertebrate taxa equivalent to those found in terrestrial environments (such as maggots or carrion beetles), micro-consumers play a main role in fish carrions decomposition.