A collective navigation hypothesis for homeward migration in anadromous salmonids

Abstract

Anadromous salmon (genera Oncorhynchus and Salmo) spend much of their lives feeding in productive northern oceans and then return home to natal sites for reproduction with remarkable accuracy. The mechanisms used for navigation by individuals during migrations are thought to include geomagnetic, celestial and olfactory cues, but rarely are social interactions between individuals considered. Mounting evidence from other taxa indicates that individuals in larger groups can better sense and respond to environmental cues, thus potentially increasing their ability to navigate. Here, we propose that salmon might similarly benefit from col lective navigation on their homeward journey. To explore this, we compiled data from multiple studies and found strong evidence that rates of successful homing increase with population abundance, consistent with collective navigation. We then discuss how collective navigation could benefit salmon during each stage of their seaward and homeward migrations, and complement this with a review of salmon sociality. Next, we analyse historic high seas catch records and provide new insight into schooling structure of salmon in the marine environment. We argue that collective navigation likely represents a presently under appreciated Fish and Fisheries ; 17 (2016), 2. -S. 525-542 https://dx.doi.org/10.1111 mechanism enhancing the navigational ability of salmon as well as other migra tory species, and outline critical tests of our hypothesis.

Social Information Links Individual Behavior to Population and Community Dynamics

“…This point was made by Schmidt et al , who showed that eavesdropping on the reproductive performance of conspecifics can enhance breeding habitat selection and, consequently, population growth. When individuals gain reproductive benefits by using social information that increases in abundance or quality with the density of information-producing individuals [21,22,[28][29][30], this [24,83]. While usually beneficial, reliance on social information can be detrimental if followed leaders are misinformed; for instance (D) bison (Bison bison) have been led by misinformed individuals to foraging grounds with high mortality risk due to hunting by humans [40].…”

“…Here, we build on several key reviews -4,18] to formalize and generalize ideas presented in recent theoretical (e.g., [23,32,39]) and empirical (e.g., [22,24,40]) papers. Our synthesis unifies…”

“…What makes social information ecologically pertinent is that it not only affects individual behavior, but [ 2 8 7 _ T D $ D I F F ] it can also induce strong correlations in the behaviors and space use of many individuals [21][22][23][24]. Thus, social information can drive a range of behaviors, from mild conspecific attraction with no subsequent parallel behaviors (i.e., simple aggregation in space), to the highly synchronized individual actions that underpin the collective motion of flocks, herds, and schools [25,26].…”

Social information use and the evolution of unresponsiveness in collective systems

“…For animal groups, this form of model may be applied to decisions, for example, relating to movement in response to predators, or larger scale movements associated with migrations. In the latter case, there is substantial evidence to suggest that both the decision of whether to migrate or not [27] and the accuracy of migration [28,29] are affected by social interaction.…”

A simple game-theoretic model for upstream fish migration

“…The conventional research suggests that schooling has many aspects of benefits, such as improvements of navigational performance (Berdahl et al 2014;Torney et al 2015), hearing perception (Larsson 2009(Larsson , 2012, and foraging efficiency (Di-Poi et al 2014;Wang et al 2016). These benefits are modelled in a lumped manner as…”