The Spot Prawn Fishery: A Status Report - Earth Economics

The Spot Prawn Fishery: A Status Report
and Management, aimed at improving the state
of this type of biological and ecological knowledge.
(See “Spot Prawn Stock Structure and
Management” box below for details.)
A pre-season test fishery has been carried out
in Hood Canal since the 1970s. This research
has been aimed at analyzing relative abundance
and life history characteristics, such as length
frequency ovigery (egg bearing), in order to set
the harvest level for the coming season and determine
the timing and duration of season openings.
The Tulalip, Swinomish, and Suquamish
Tribes also run pre-season test fisheries for
ovigery to determine the percentage of female
prawns that are egg-bearing. These test fisheries
are carried out in the central Sound/Whidbey
Basin. The Hood Canal fishery presently is a
recreational and tribal commercial fishery only.
The State commercial fishery has been closed
since 1992.
The Puget Sound (excluding Hood Canal)
Pandalid Shrimp Harvest Management Plan
(2001a) recognizes that biological information
about Puget Sound pandalid shrimp resources is
currently limited. Both parties “share the goal of
collecting and analyzing additional information to
improve shrimp [prawn] management” (WDFW
2001a). Additional biological information may be
required in order to “make future assessments of
allowable harvests and harvest methods.” This
information may include the following:
•develop quantitative survey methods to estimate
the allowable catch by area, species, and
gear type
•biological basis for the establishment of harvest
seasons; e.g., to deter harvest of ovigerous prawn
•biological criteria for in-season data collection
to evaluate harvest impacts and ensure proper
resource utilization; e.g., count per pound
•designation of minimum size limits of prawn
and appropriate gear mesh size restrictions
•designation of shrimp prawn nursery areas
•identification of sub-areas needing unique
management provisions
•distribution and abundance of prawn species
•methodology for estimation of non-commercial
harvests and other fishery-related mortalities,
including the bycatch of non-target species
(WDFW 2001a)
This additional biological information has not
been collected to date. At the present time, the
SPOT PRAWN STOCK STRUCTURE AND MANAGEMENT
A three-year (2001, 2002, and 2003)
Washington Sea Grant Program will
support spot prawn research in
Washington’s inshore and offshore
fisheries.The need for this program
arose from the fact that, despite the
value of spot prawns to commercial
and recreational fishing interests,
little biological or ecological information
is available for management.
According to the Project
Rationale,“The life cycle of these
animals makes them especially vulnerable
to overexploitation, so this
information [the size, genetic structure,
and relationship between the
species’ various stocks] is necessary
for sound management of the
resource” (Lowry 2000).
The Project’s primary objectives are:
•“To use microsatellite DNA analysis
to investigate the genetic relationships
between prawns from the
major fishing areas in Washington
State, both inshore and offshore.
•“To examine modeled and observed
current and water property patterns
to determine the likelihood of
local retention and exchange of larvae
between putative sub-populations.
•“To use the above two types of
information to define the ranges of
the populations being fished.
•“To use logbook data from the
commercial fishery to determine
major fishing areas offshore and
develop an area-specific biomass
dynamics model for use in setting
maximum catches.
•“To provide fishery management
recommendations regarding
resource sustainability, including
habitat protection and the potential
use of reserves as a management
tool” (Lowry 2000).
The Project methodology will
involve sampling sites in both the
offshore and inshore fisheries and
comparing the genetic makeup of
the animals in these two regions.
Commercial fishing logbook data
will be used to ensure that areas
where spot prawns tend to aggregate
are sampled. Genetic stock
structure and distribution data will
then be compared to oceanographic
movement models in order to
locate areas where larvae are transported,
as well as where they are
retained. An area-specific model of
spot prawn population dynamics
will be developed.
This Project will allow the description
of “the genetic stock structure
of Washington stocks of spot
prawns, within Puget Sound and
the Northern Straits of San Juan de
Fuca as well as offshore. Comparison
of this with oceanographic features
in the areas occupied by spot
prawns will allow us to draw conclusions
about the life history of the
offshore spot prawn populations,
interactions between sub-populations,
and the importance of eddies
to the retention of larvae in submarine
canyons” (Lowry 2000).
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