Lichatowich, Jim. Salmon without Rivers: a History of the Pacific Salmon Crisis. Island Press, 1999.
In Chapter 7 of Salmon Without Rivers, Lichatowich discusses solutions to the four main problems causing the declining abundance of salmon: facilitating salmon egg transfer, eliminating predators of salmon, controlling ocean troll fishery, and strengthening salmon passage at high dams (pg 152). In 1925, experts met in Seattle; finally acknowledging and discussing the extent of these issues, and how to solve them. One conclusion that came from the meeting was that substantial research of salmon and their decline was still needed (proposed by Gilbert). Considered by some to be the first fisheries biologist in the US, “as early as 1913, Gilbert had used an ingenious method to work out the basic life histories of the Pacific Salmon…The salmons scales grow roughly in proportion to the growth of the fish, and as the scales grow, circular ridges are deposited on their surface. These rings, called circuli, are similar to the rings in a cross sectional cut of a tree. Narrow spacing between tree rings means slow growth, whereas wide spacing indicates rapid growth” (pg 164). This methodology still influences current knowledge of salmon life history, for example, from Gilbert’s idea of dividing “juvenile salmon into two general categories, stream and ocean, based on their life histories. Stream-type fish remained in fresh water for a year and migrated to sea in the spring of their second year of life. Ocean-type fish migrated to sea shortly after emerging from the gravel during their first year of life” (pg 164). As you can see, Gilbert’s findings about scales provided information that led to a topic integral to fish conservation: life history. This advancement in the knowledge of Pacific salmon life history improved harvest recommendations by expanding our understanding of issues like the homing of salmon, and when hatcheries should release them. Life history answers broad questions like, what/ when/ where/ and how salmon do things; and also very specific questions like, “that salmon populations were composed of individual fish that exploited their environment in different ways. He speculated that this life history diversity had an ecological basis, and that it was an integral part of the relationship between the fish and it’s environment” (pg 165). One issue that hatcheries (at the time) had with Gilbert’s findings was that they believed that human controlled production was more efficient than natural ecological processes (165), and therefore continued to degrade fish natural life history by operating hatcheries on their own terms. By taking a more ecological and scientific approach, harvest management can be improved. All of the problems causing the decline of salmon, introduced in the 1920’s Seattle meeting, are human caused. Researching salmon life history, and applying convergent evidence to harvest management, will likely improve salmon abundance.
Other aspects of salmon ecology that should be considered are the general changing effects that human urbanization has on salmon habitat. Examples include the effects of climate change, recreation, disturbance, and energy development. By studying and managing these things with a greater environmental ethic, humans can create greater biodiversity of salmon habitat, and provide better chances for natural ecological processes to work.