A retrospective of the hake stocks off the Atlantic and Pacific coasts of the United States: Uncertainties and challenges facing assessment and management in a complex environment

摘要

Hake stocks off the northeast and northwest coasts of the United States and Canada have been commercially exploited since the early 1950s and have been major contributors to the historic world-wide hake catches. During the last two decades annual U.S. hake catches have averaged approximately 300,000 tonnes with the dominant share coming from the coastal Pacific hake (Merluccius productus) stock. Pacific hake occurs over the continental shelf with a number of localized sub populations found in coastal inland waters of Washington State and the Province of British Columbia. In the northwest Atlantic two sympatric species occur, the commercially sought coastal silver hake (Merluccius bilinearis) and the offshore hake (Merluccius albidus), which is generally distributed in deeper waters. As with many of the 12 world-wide species of hakes in the genus Merluccius, the U.S. hake species share common attributes in their biology, ecology and population dynamics which may be dictated by the production cycles and circulation patterns characteristic of northerly ecosystems. For instance, both species exhibit a migration pattern centered on spawning in one region followed by feeding in another, both are fast swimming ambush predators that take advantage of high euphausid production as young but transition to a piscivorous diet with age, and both are known to exhibit highly variable, density-dependent related life history characteristics as population regulatory mechanisms. However, these species can be contrasted in many different ways related to specific adaptations within the unique ecosystems in which they live, the diverse and changing fisheries targeting them, and the complexity of stock assessment tools and management structures that have emerged in an attempt to provide a sound scientific basis for setting catch limits. This paper takes a retrospective and contemporary look at these two species, comparing and contrasting our current state of knowledge, highlighting uncertainties and identifying the complex challenges facing assessment and management