Carcass analogues provide marine subsidies for macroinvertebrates and juvenile Atlantic salmon in temperate oligotrophic streams

Abstract

Summary Anadromous fish populations entering freshwater ecosystems provide organic matter and marine‐derived nutrients during spawning and subsequent mortalities of adults. Dams and other impediments to connectivity in rivers and streams have affected anadromous fish populations in many regions and prevented or reduced this influx of organic materials and nutrients. This study used historical data on the timing of delivery of marine‐derived nutrients; we added a carcass analogue (pellets made from the carcasses of Chinook salmon, Oncorhynchus tschawytcha) to simulate potential effects of restored access of anadromous fish to streams. We used stable isotopes to document the extent of nutrient incorporation of nitrogen and carbon from the carcass analogue by macroinvertebrates and juvenile Atlantic salmon (Salmo salar) in salmon nursery streams. We stocked four headwater streams that historically hosted spawning Atlantic salmon and sea lamprey (Petromyzon marinus) in Maine, U.S.A. with Atlantic salmon fry and simulated timing of nutrient addition by spawning sea lamprey in the early summer and Atlantic salmon in the autumn. Macroinvertebrates and Atlantic salmon assimilated nitrogen (12–57% of total N) and carbon (21–65% of total C) from the added pellets, and the magnitude and duration of enrichment varied temporally and with macroinvertebrate functional feeding group. Assimilation of nutrients from carcass analogues was both direct and indirect, and a nutrient legacy was evident in the second year of sampling. Incorporation of nutrients from the pellets at a range of heights in the food web demonstrated the potential for marine‐derived subsidies to contribute to freshwater ecosystem processes in Atlantic salmon nursery streams.

Sea LampreyPetromyzon marinusBiology and Management Across Their Native and Invasive Ranges: Promoting Conservation by Knowledge Transfer

“…Mills et al, 2003;Cochran, 2009;Nislow and Kynard, 2009;Sousa et al, 2012;Guyette et al, 2014;Hogg et al, 2014 Economic values Through commercial exploitation for human food, as live foods in aquaculture, and as bait for sport fishing. Renaud, 1997;Beaulaton et al, 2008;Mateus et al, 2012;Foulds and Lucas, 2014 Threats to their native populations…”

“…The ecological roles of lamprey populations mainly involve nutrient cycling in food webs (e.g., Mills et al, 175 2003), marine-derived nutrient subsidies (e.g., Nislow and Kynard, 2009;Guyette et al, 2014), habitat modifications as ecosystem engineers (e.g., Sousa et al, 2012;Shirakawa et al, 2013;Hogg et al, 2014), prey resources for other animals (e.g., Cochran, 2009), as well as being 180 top predators and parasitic (e.g., Madenjian et al, 2008, Table 1). Recently, for instance, studies have indicated that the returning adults provide considerable inputs of marine-derived nutrients into freshwater ecosystems via metabolic waste, unfertilized eggs, and post-spawning 185 death and body decomposition, which are important for increasing freshwater productivity (Nislow and Kynard, 2009;Guyette et al, 2013).…”

Biofilm nutrient limitation, metabolism, and standing crop responses to experimental application of salmon carcass analog in Idaho streams

“…Although a number of studies have demonstrated that organic nutrient mitigation materials may be transferred to juvenile salmon via direct consumption (Wipfli et al 2004;Kohler et al 2012;Guyette et al 2014), the evidence for the indirect pathways via stimulation of biofilm production is inconsistent and sometimes contradictory across studies (e.g., Wipfli et al 1999;Kohler et al 2008;Cram et al 2011). Although a number of studies have demonstrated that biofilm chlorophyll a or ash-free dry mass (AFDM) may increase in the short term following nutrient enrichment (Kiernan et al 2010;Kohler et al 2012), others have shown that standing crop may not increase if other factors like light are limiting to primary production (Ambrose et al 2004).…”

The delivery, seasonal storage, and trophic transfer of marine-derived nutrients within a stream-riparian ecotone

“…The timing of spawning season within an insect's life cycle, as well as salmon nutrient legacy, will contribute to species and location-specific enrichment (Honea & Gara 2009, Guyette et al 2014). …”

“…The annual resource pulse of salmon nutrients can help support macroinvertebrate populations (Minakawa et al 2002, Lessard & Merritt 2006, Verspoor et al 2011, enrich resident fish populations and increase juvenile salmon survivorship (Bilby et al 1996, Rinella et al 2012, Guyette et al 2014, increase nutrient storage in basal resources, like biofilms (Albers 2010, Reisinger et al 2013, and promote terrestrial plant growth (Naiman et al 2002, Schindler et al 2003, Koyama et al 2005, Reisinger et al 2013). …”