Habitat associations of exploited fish species in the Lower Amazon river–floodplain system

1. Modification of floodplain morphology and land use is widely recognized as a major threat to fish communities of river–floodplain systems. We assess habitat associations of major exploited fish species in the Lower Amazon, where modifications are more extensive than in the Central or Upper Amazon. 2. Habitat was characterized in terms of physical environment, vegetation cover, distance from river and mean depth. Habitat associations of late juvenile and adult fish of the 14 major exploited species were established by comparing the distribution of the habitat sampled with the distribution of the habitat sampled weighed by a fish abundance index (catch per unit of effort). 3. Eight species showed significant habitat associations, generally being most abundant in floodplain lakes. Five of these eight species were associated with open water. Of the three exceptions, two preferred flooded forest lakes and another macrophyte-dominated channels. The majority of those species with significant associations also preferred waters shallower than 7.25 m and relatively distant from the river mainstream. 4. While flooded forest is often assumed to be a key habitat for Amazon fish, only two of the main exploited species in the Lower Amazon had a significant association with this habitat. The majority of exploited species, including one that is associated with flooded forest in the central and upper Amazon, either showed no habitat associations or preferred open water lakes. The full range of pristine and modified floodplain habitats should be considered as important to fish conservation and fisheries productivity