Limited Diets of Eastern Blacknose Dace (Rhinichthys atratulus Hermann) Within the Highly Urbanized Bronx River, New York, USA

Juliet Hernandez; Matthew J. Lundquist

Limited Diets of Eastern Blacknose Dace (Rhinichthys atratulus Hermann) Within the Highly Urbanized Bronx River, New York, USA

Juliet Hernandez¹ and Matthew J. Lundquist^{1, *}

¹Department of Natural Sciences, Marymount Manhattan College, 221 E 71st St, New York, NY 10021. ^*Corresponding author.

Urban Naturalist Notes, No. 11 (2025)

Abstract
Urbanization, the transformation of natural landscapes into cities, can cause altered hydrology, increased pollutants, and habitat fragmentation in nearby rivers. While biodiversity loss in urban rivers is well documented, the impact of urbanization on food webs is understudied. We examined urban trophic dynamics by analyzing gut contents of Rhinichthys atratulus (Eastern Blacknose Dace) from the highly urbanized Bronx River in New York in the summer of 2023. The diets of R. atratulus were dominated by midge larvae (Chironomidae), with some individuals also containing various combinations of caddisflies (Hydropsychidae), amphipods (Gammaridae), and cladocerans (Diplostraca). Despite other invertebrate taxa documented in the river, R. atratulus consumed only this limited subset. While they are considered generalists in non-urban environments, our findings suggest their dietary specialization in this urban system. This narrowed dietary breadth may reduce aquatic food web resilience against further urbanization impacts.

Download Full-text pdf