9781888569551-ch86

Proceedings of the Third World Fisheries Congress: Feeding the World with Fish in the Next Millenium—The Balance between Production and Environment

Update on the Fishery-Independent Assessment of Shrimp Stocks in British Columbia, Canada

James A. Boutillier, Hai Nguyen, Norm Olsen

doi: https://doi.org/10.47886/9781888569551.ch86

The shrimp trawl fishery in British Columbia, on the west coast of Canada, is a complex collection of fisheries that extends over 36 management areas. The fisheries are located in various zoogeographic areas, from large offshore, open-ocean ecosystems to small isolated fjords. Seven species of shrimp are harvested, and the trawl fisheries vary in complexity from single- to multiple-species fisheries. In addition, many of the shrimp trawl fisheries are new or developing as a result of major shifts in effort into trawl fishery, where little or no information was available from which to assess the stocks.

As a result of discussions and concerns outlined by Boutillier and Joyce (1998) and Boutillier et al. (1997), a suite of management principles was developed for inshore and offshore shrimp fisheries, respectively. Management systems that were adopted in 1998 vary depending on the nature, location, and complexity of the fishery.

Offshore fisheries in the southern and central regions off the west coast of Vancouver Island (WCVI) are controlled using time and area closures. However, this approach may change if a quota system is implemented, as suggested by Martell et al. (2000). For inshore fisheries and the remaining offshore areas, catch ceilings (fixed arbitrary, historically based, or forecasted4) are assigned to each shrimp management area. These catch ceilings are adjusted during the season, if information from fishery-independent biomass indices and catches indicates that the area can sustain fishing pressure less than or greater than the initially prescribed levels.

In this paper, we outline some of the problems facing the assessment of the shrimp stocks targeted by these fisheries, the assessment processes that try to address these problems that have been in use since 1998, and future directions to improve the assessment framework.

We have identified six major issues facing the delivery of assessment framework:

• The trawl fishery targets seven shrimp species. Even though all these species belong to the family Pandalidae, a range of behaviors and life history characteristics (e.g., habitat preferences, migration patterns) affect the manner in which they can be effectively assessed. Some of these key life history characteristics are outlined for each species in Table 1.
• There are too many fisheries to assess with the available resources. The total area includes more than 36 separate management areas and more than 100 individual species quotas.
• How can biomass indices be obtained that are reliable indicators of population status from such a variety of trawlable fishing areas? (What is the most appropriate survey design for each area? What is the most appropriate analytical technique to employ in this survey?)
• How can shrimp that are outside the trawlable areas—particularly in rocky habitats—be assessed?
• How can assessments ensure that the shrimp are available to the trawl survey and not up in the water column, particularly with shrimp that show some pelagic tendencies? (Historically, it was believed that for several pink shrimp, this vertical migration occurred on a diurnal cycle and was related to nocturnal migrations.)
• How much of the trawlable area is actually preferred habitat for each species?