Interannual variability in life-stage specific survival and life history diversity of coho salmon in a coastal Oregon basin

We quantified the population dynamics and life history diversity of seven brood years of coho salmon using a life-cycle approach. Four life history patterns, composed of fry, fry–nomad, parr, and yearling migrants indicated the importance of connectivity and access to a full range of freshwater and estuarine rearing environments through the year. Survival of each life history type varied annually with the yearling migrants contributing an average of 70% to the spawners in all but one return year. Fifty eight percent of the spawners of the 2013 return year had an estuarine rearing strategy, primarily parr migrants that overwintered in the estuary. Fry migrants, thought to be surplus production, were consistently observed in the estuary and represented in the returning spawners. The annual contribution of alternative rearing strategies to the spawners may support the resilience and viability of the population. We recommend that life cycle models of coho salmon account for the contribution of estuary migrants to the productivity and persistence of coho salmon in support of management and restoration of populations.

Differential migration in Pacific salmon and trout: Patterns and hypotheses

Migrations affect the population dynamics, life history, evolution, and connections of animals to natural ecosystems and humans. Many species and populations display partial migration (some individuals migrate and some do not), and differential migration (migration distance varies). Partial migration is widely distributed in fishes but the term differential migration is much less commonly applied, despite the occurrence of this phenomenon. This paper briefly reviews the extent of differential migration in Pacific salmon and trout (genus Oncorhynchus), a very extensively studied group. Three hypotheses are presented to explain the patterns among species: 1) phylogenetic relationships, 2) the prevalence of partial migration (i.e., variation in anadromy), and 3) life history patterns (iteroparous or semelparous, and duration spent feeding at sea prior to maturation). Each hypothesis has some support but none is consistent with all patterns. The prevalence of differential migration, ranging from essentially non-existent to common within a species, reflects phylogeny and life history, interacting with the geographic features of the region where juvenile salmon enter the ocean. Notwithstanding the uncertain evolution of this behavior, it has very clear implications for salmon conservation, as it strongly affects exposure to predators, patterns of fishery exploitation and also uptake of toxic contaminants.

The life of Fabian, an Azara’s owl monkey (Aotus azarae) of the Argentinean Chaco

Species-life history patterns provide insights into the adaptative strategies and importance of social behaviours. The cathemeral activity pattern of Aotus azarae allowed researchers from the Owl Monkey Project of Formosa, Argentina, to witness remarkable life changing events over the complete lifespan of several individuals. Here we summarize the life of Fabian, a male owl monkey we followed from the moment he started searching for a mate until he died. Although still not consistently considered in models of social evolution of mammals, our discovery of a subpopulation of solitary owl monkey floaters forced us to rethink some aspects of their characteristic social organization and mating system. Through the life of Fabian we present some representative examples of the intrasexual competition regulating the social system of the members of this genus during the different stages in the life of individuals, while reporting the first case of extra-pair copulation in wild owl monkeys.