Branching complexity and morphological characteristics of coarse woody structure as lacustrine fish habitat

Abstract

The objective of this study was to quantify the physical characteristics of coarse woody structure (CWS) as fish habitat in a north temperate lake. Sixteen species of fish were observed in submerged CWS habitat. Branching complexity, distance above the bole, area below the bole, distance to other CWS, and water depth around CWS were significantly related to abundance of schooling cyprinids (Cyprinidae), rock bass (Ambloplites rupestris), smallmouth bass (Micropterus dolomieu), bluegill (Lepomis macrochirus), yellow perch (Perca flavescens), and walleye (Sander vitreus). Branching complexity was the most common characteristic of CWS related to richness, diversity, and total adult abundance of fish taxa, but was not correlated with the total lengths of fish found in submerged trees. Branching-complexity values ranged from 1 (simple) to 500 (moderately complex) in the littoral zone; for comparison, a living riparian conifer had a branching-complexity value of over 1000. Most CWS in the littoral zone was composed of simple trees without branching, but fish tended to inhabit CWS with branching-complexity values greater than 45. This study shows the importance of CWS with fine branching as littoral-zone fish habitat.