Fish and invertebrate ecology of Tillas and Islas Sloughs, Smith River estuary, Del Norte County, California

As wetland habitat continues to disappear along the Pacific coast of North America, more research is being conducted to examine the importance of this habitat for the survival of various fish species. Sloughs, marshes, and side channel type habitats have been shown to provide an important niche for estuarine fauna and flora. Before this study, fish and invertebrate fauna of Tillas and Islas Sloughs in the Smith River estuary, California, were not formally examined. During the study period, 26 fish species were found belonging to 14 families. The sloughs were found to be highly productive in terms of fish, invertebrate abundance, and grass and algae cover. However, they were low in diversity, as is typical of estuarine habitats. Abundances of the most dominant fish species, including Chinook salmon, Oncorhynchus tshawytscha, were variably correlated with temperature, salinity, dissolved oxygen, nutrient concentration, and grass and algal cover. The sloughs were shown to be used by permanent resident fishes as well as by spawning adults, juvenile fishes, and foraging visitors. Benthic fauna appeared to be controlled primarily by predation by fish and displayed no significant correlation with environmental parameters.