Session B3 - Survival improvements at Fish Guidance Systems designed to improve safe downstream passage of anadromous and catadromous fish

The range of river herring (A. pseudoharengus and A. aestivalis) is much smaller now than historical records represent during the pre-colonial and pre-industrial revolution phases of New England settlement. Many water control structures in New England are built on top of falls and other natural flow constrictions that were not impediments to river herring passage during antiquity, but are now, despite implementation of technical fish pass design criteria. There are locations in New England, especially in Maine, where river herring ascend falls and other natural features that appear to exceed accepted fish passage criteria. Upstream fish passage at a given site is dependent upon multiple factors, including swimming characteristics of target fish species/life stages and hydraulic conditions during seasonal migration periods. Technical fishpass design criteria are intended to provide for fishpass designs that are conservative in terms of maximum flow speeds, heights of hydraulic drops, and holding area turbulence as defined by an energy dissipation factor. Are there characteristics that allow for upstream fish passage that are not considered in the design criteria? Here we present specific examples of sites where adult river herring pass upstream over seemingly impassable features during seasonal spawning migrations. We identify characteristics of each site relevant to upstream fish passage and compare those natural barrier metrics to commonly used metrics for design of upstream fish passage systems. Our objective is to inform decision making and design implemented in watershed-scale fisheries restoration planning and the design of technical and “nature-like†fishpass systems