Pacific salmon abundance along the West Coast of Canada has been in sharp decline since the early 1990s. Declines have been most severe for coho and chinook salmon despite large additions of hatchery-reared fry and smolts. There is particular concern for populations of wild coho because, in addition to low abundance, up to 80% of the juvenile coho in the coastal waters has been identified as be...

1. Pacific salmon (Oncorhynchus spp.) deliver marine-derived nutrients to the streams in which they spawn and die, and these resource subsidies can increase the abundance of stream biota. In strong contrast, physical disturbance from salmon spawning activity can reduce the abundance of benthic organisms. Previous experimental designs have not established the relative effects of these two contra...

amoebic gill disease (agd) is the most important parasitic disease of atlantic salmon industry inaustralia. atlantic salmon (salmo salar) experimentally infected with neoparamoeba sp. apparently showedagd gross signs on the gill and an amoebic-associated gill pathology. physico-chemical factors of waterduring the experiment were monitored regularly and were approximately constant (temperature: ...

Organisms can control movements of nutrients and matter by physically modifying habitat. We examined how an ecosystem engineer, sockeye salmon (Oncorhynchus nerka), influences seasonal fluxes of sediments, nitrogen (N), and phosphorus (P) in streams of southwestern Alaska. The purpose of this study was to investigate whether salmon act as net importers or net exporters of matter and nutrients f...

The impact of parasites on hosts is invariably negative when considered in isolation, but may be complex and unexpected in nature. For example, if parasites make hosts less desirable to predators then gains from reduced predation may offset direct costs of being parasitized. We explore these ideas in the context of sea louse infestations on salmon. In Pacific Canada, sea lice can spread from fa...

The ecological risks of salmon aquaculture have motivated changes to management and policy designed to protect wild salmon populations and habitats in several countries. In Canada, much attention has focused on outbreaks of parasitic copepods, sea lice (Lepeophtheirus salmonis), on farmed and wild salmon in the Broughton Archipelago, British Columbia. Several recent studies have reached contrad...

In the western United States, pesticides used in agricultural and urban areas are often detected in streams and rivers that support threatened and endangered Pacific salmon. Although concentrations are rarely high enough to cause direct salmon mortality, they can reach levels sufficient to impair juvenile feeding behavior and limit macroinvertebrate prey abundance. This raises the possibility o...

A plasmacytoid leukemia of chinook salmon, Oncorhynchus tshawytscha, has recently been recognized in seawater netpens in British Columbia, Canada. The disease has occurred at several sites and has caused high mortality. Plasmacytoid leukemia is characterized by a generalized invasion of visceral tissues and the orbit of the eye by plasmacytoid cells. The disease was experimentally transmitted t...

Increased farm salmon production has heightened concerns about the association between disease on farm and wild fish. The controversy is particularly evident in the Broughton Archipelago of Western Canada, where a high prevalence of sea lice (ectoparasitic copepods) was first reported on juvenile wild pink salmon (Oncorhynchus gorbuscha) in 2001. Exposure to sea lice from farmed Atlantic salmon...

Cross-boundary nutrient inputs can enhance and sustain populations of organisms in nutrient-poor recipient ecosystems. For example, Pacific salmon (Oncorhynchus spp.) can deliver large amounts of marine-derived nutrients to freshwater ecosystems through their eggs, excretion, or carcasses. This has led to the question of whether nutrients from one generation of salmon can benefit juvenile salmo...