Abstract Manager

Developing compensation habitat is a key component of transportation projects when avoidance and mitigation measures cannot fully avoid impacts to fish and fish habitat. Compensation requirements are identified by Fisheries and Oceans Canada (DFO) through policies for applying measures to offset adverse effects to fish and fish habitat; however, in sensitive wetland complexes these measures often intersect with requirements to address terrestrial Species at Risk (SAR), creating design and implementation challenges. The Long Point Causeway Rehabilitation project, located near Port Rowan, Ontario, involved replacement of a deteriorating timber pile bridge within the UNESCO-designated Long Point Biosphere Reserve, a Ramsar Wetland of International Importance, and adjacent to Big Creek National Wildlife Area. The project area supports multiple aquatic and terrestrial SAR, including SAR fish, turtles, snakes, and birds. Compensation habitat was required to offset unavoidable impacts associated with bridge replacement in this highly constrained and sensitive environment. The objective of the compensation design was to provide an overall net benefit to SAR fish while integrating habitat features for co-occurring terrestrial SAR. Offset measures included excavation of compensation ponds, installation of anchored shoreline logs and brush piles to provide basking and refuge habitat for SAR turtles and snakes, submerged resting structures for aquatic turtles, and seeding of constructed berms to stabilize soils and protect nearshore habitat. But, achieving these objectives simultaneously can be difficult.  For example, design criteria for SAR Spotted Turtle required extensive shallow water areas, with approximately 30–35% of pond area designed at depths less than 0.25–0.30 m, creating challenges when trying to maintain water depths for fish pond deepness in a hydrologically flashy ecosystem. Implementation and post-construction observations identified several key challenges. Extensive shallow areas reduced the availability of functional aquatic habitat during low water periods and created conditions highly conducive to invasive Phragmites reestablishment, particularly as all compensation areas had previously supported dense Phragmites stands prior to excavation. Most significantly, the project demonstrated that incorporating compensation measures for terrestrial SAR into fisheries offsetting can create challenges to fisheries habitat quality if trade-offs are not carefully managed. This case study highlights the importance of clearly defining compensation objectives, recognizing limitations of multi-species habitat compensation and realistically addressing invasive species during design.