Introduction to stock assessment
Unit 1.1: Canada's approach to fisheries science
Definition:
Throughout this training and under the Fisheries Act fish includes:
fish, shellfish, crustaceans, and marine animals
any parts of fish, shellfish, crustaceans, and marine animals
eggs, sperm, spawn, larvae, spat, and juvenile stages of fish, shellfish, crustaceans, and marine animals
Definition:
Fish stocks are groups of the same species with a shared characteristic(s) of interest to managers. Fish stocks are often defined by a management area and can include:
a single population
a smaller subset of 1 population
more than 1 population
Fish in different stocks can also mix or migrate between different management areas.
Fish stocks provide economic and social benefits to coastal communities. Their management plays an important role in maintaining stable and resilient ecosystems. They provide important ecological goods and services to all Canadians.
Sockeye Salmon. Photo credit: DFO
Example: Sockeye Salmon
Pacific salmon stocks often contain multiple populations that breed in different rivers. A Conservation Unit (CU) is a group of wild salmon that is isolated from other groups. If a CU goes extinct locally, it is unlikely to recolonize that area. A CU can contain 1 or more populations. Stock Management Units (SMU) are collections of stocks that are managed together with a joint stock status. There are 216 Sockeye Salmon CUs that make up 16 SMUs.
Example: Atlantic Mackerel
A population of Atlantic Mackerel can be found along the east coast from Labrador to North Carolina. However, the Atlantic Mackerel stock managed by Fisheries and Oceans Canada (DFO) only includes the fish found in Canadian waters from Labrador to Nova Scotia, including the Gulf of St. Lawrence.
