Consider the case of the three-spine stickleback. These tiny fish that thrive in oceans and in fresh water might appear to be the same, yet ecologists are finding that they are actually a diverse collection of very specialized individuals.

Being the neighbourhood bully has its obvious advantages, but it becomes useless if your authority is continuously being challenged. In many animal species, however, stable hierarchies are routinely formed in which some individuals seem to slip naturally into their dominant role whereas others resign themselves to play the part of lowly subordinates.

Exposure to estrogen reduces production of immune-related proteins in fish. This suggests that certain compounds, known as endocrine disruptors, may make fish more susceptible to disease.

Ciguatera poisoning, the food-borne disease that can come from eating large, carnivorous reef fish, causes vomiting, headaches, and a burning sensation upon contact with cold surfaces. An early morning walk on cool beach sand can become a painful stroll on fiery coals to a ciguatera victim.

Many native fishes in the Pacific Northwest are threatened or endangered, notably salmonids, and hundreds of millions of dollars are expended annually on researching their populations and on amelioration efforts. Most of the attention and funding have been directed toward to the impacts of habitat alteration, hatcheries, harvest, and the hydrosystem—the "all H's."

Human impacts on the environment have reduced populations of wild species to dangerously low levels. Nowhere is this more apparent than in worldwide fisheries, where thanks to overfishing and habitat destruction, countless species and populations of fish are on the brink of disappearing forever.

Scientists have discovered that management efforts intended to assist migrations of salmon and steelhead trout can have unintended consequences for fish populations. Juveniles that are transported downstream on boats can lose the ability to migrate back to their breeding grounds, reducing their survivorship and altering adaptations in the wild.

Researchers in Spain are reporting that a new DNA identification method could thwart false labeling of shark species used in various seafood products, including the expensive Chinese delicacy known as shark fin soup.

Next week marks a pivotal moment for Eastern Pacific tuna. The Inter-American Tropical Tuna Commission (IATTC), the international body charged with the conservation and management of tuna and associated species in the eastern tropical Pacific Ocean, will meet in San Diego from Nov. 2-7 to consider conservation measures for vulnerable tuna populations.

A giant Atlantic bluefin tuna weighing more than half a ton had the honor of being fitted with the 1000th electronic tracking tag placed on this threatened species when it was caught and released on Monday (October 20) in the Gulf of St. Lawrence off Port Hood, Nova Scotia.

A new study by researchers in Oregon and British Columbia has found that survival of juvenile salmon and steelhead during their migration to the sea through two large Northwest rivers – the Columbia and the Fraser – is remarkably similar despite one major difference.

New research has provided the first detailed look at the internal head skeleton of Tiktaalik roseae, the 375-million-year-old fossil animal that represents an important intermediate step in the evolutionary transition from fish to animals that walked on land.