An evaluation of upstream fish passage at Mactaquac Generating Station

Abstract

Mactaquac Generating Station – the lowermost hydroelectric dam on the Wolastoq – is equipped with a trap-lift-and-transport fishway that targets Atlantic salmon (Salmo salar) and river herring (alewife Alosa pseudoharengus and blueback herring A. aestivalis) for upstream passage. Despite having been operational since 1968, the performance of the Mactaquac fishway has not been evaluated prior to this dissertation, which focused on estimating the proportion and timing of upstream passage by target species using biotelemetry (PIT, radio, and acoustic telemetry). The fishway passed a low proportion (<20%) of tagged fish that approached and entered the fishway for all three target species, and individuals that successfully passed upstream experienced considerable passage delays after initially approaching or entering the fishway (Atlantic salmon: mean = 58 d; river herring: mean = 11 d). Based on the evidence that the Mactaquac fishway did not provide effective and timely passage for tagged fish in this dissertation, I conclude that fishway performance is ultimately poor for the target species. The major factors that contributed to poor fishway performance identified during this dissertation included 1) hydraulic conditions in the tailrace and fishway that provided poor attraction to the point of capture for Atlantic salmon, 2) the low capacity of lift and transport containers relative to the size (i.e., several million individuals) and schooling behavior of target river herring populations led to a “migratory bottleneck” downstream of the fishway, which likely contributed to passage delays, low passage efficiency, and selection for larger fish, and 3) dependence on a fishway operator to entrap and pass fish and infrequent fishway operation hours (i.e., 6-8 hours/day, 1-7 days/week) limited passage opportunities for all species. Key recommendations stemming from this research for immediate improvements to upstream passage include increasing fishway operation efforts to 24 hours/day throughout the fishway operation season (all species) and expanding seasonal fishway operation (i.e., from late-April to the end of November) to better reflect the migration windows of target species. My key recommendations for potential fishway upgrades include automating lift and sorting structures to reduce operator dependence and increasing fishway capacity to enable greater quantities of fish to pass at once.