Riding the crimson tide: mobile terrestrial consumers track phenological variation in spawning of an anadromous fish

Abstract

When resources are spatially and temporally variable, consumers can increase their foraging success by moving to track ephemeral feeding opportunities as these shift across the landscape; the best examples derive from herbivoreplant systems, where grazers migrate to capitalize on the seasonal waves of vegetation growth. We evaluated whether analogous processes occur in watersheds supporting spawning sockeye salmon (Oncorhynchus nerka), asking whether seasonal activities of predators and scavengers shift spatial distributions to capitalize on asynchronous spawning among populations of salmon. Both glaucous-winged gulls and coastal brown bears showed distinct shifts in their spatial distributions over the course of the summer, reflecting the shifting distribution of spawning sockeye salmon, which was associated with variation in water temperature among spawning sites. By tracking the spatial and temporal variation in the phenology of their principal prey, consumers substantially extended their foraging opportunity on a superabundant, yet locally ephemeral, resource. Ecosystem-based fishery management efforts that seek to balance trade-offs between fisheries and ecosystem processes supported by salmon should, therefore, assess the importance of life-history variation, particularly in phenological traits, for maintaining important ecosystem functions, such as providing marine-derived resources for terrestrial predators and scavengers.

Riparian soil nitrogen cycling and isotopic enrichment in response to a long‐term salmon carcass manipulation experiment

“…The annual return of this predictable and abundant, yet temporally limited, high-quality resource drives the foraging ecology of both terrestrial and aquatic consumers (Schindler et al 2013, Quinn 2018. Carcasses and roe are documented food sources for over 22 species of mammals, birds (Cederholm et al 1989), fishes (Scheuerell et al 2007), and invertebrates (Minakawa et al 2002, Meehan et al 2005, Winder et al 2005.…”

Importance of Riparian Zone: Effects of Resource Availability at Land-water Interface

“…Many terrestrial mammal consumers (e.g. bears, pine marten, cougar, and wolverine) travel among patched habitats following environmental cues to time the seasonal arrival of peak food "rain" [88,89]. A suitable example of large mammal predators influencing nutrient dynamics along riparian zones is bears with their salmon prey (marine-derived nutrients, MDN) [84,90].…”

The evolutionary origins of diadromy inferred from a time-calibrated phylogeny for Clupeiformes (herring and allies)

“…Diadromous fishes have been a long-standing fascination of biologists [1][2][3][4], both because of the impressive physiological and behavioural adaptations necessary for survival in different habitats, and because diadromy has significant implications for the ecology, evolution and biogeography of fishes [5][6][7][8]. For instance, diadromy can impact genetic diversity and amounts of gene flow [9], alter life-history traits [10,11], and have cascading effects between marine, freshwater and terrestrial food webs [12]. Moreover, many of the approximately 250 diadromous fish species found nearly worldwide [7,13,14] are heavily studied iconic food and sport fishes (e.g.…”