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 Southeast Fisheries Science Center
Galveston Laboratory
4700 Avenue U
Galveston, Texas 77551-5997
409-766-3500 (voice) 409-766-3508 (fax)
June 26, 2008
To All Concerned:
FORECAST FOR THE 2008 BROWN SHRIMP
SEASON IN THE WESTERN GULF OF MEXICO,
FROM THE MISSISSIPPI RIVER TO THE U.S. -
MEXICO BORDER.
Prediction Summary
Each year at this time scientists at the
National Marine Fisheries Service (NOAA
Fisheries) Southeast Fisheries Science
Center's Galveston Laboratory forecast
brown shrimp production from the western
Gulf of Mexico for the following year
(July 2008 – June 2009). Data obtained
from NOAA Fisheries Galveston Laboratory
Fishery Management Branch, NOAA
Fisheries port agents, National Climatic
Data and Weather Centers, Louisiana
Department of Wildlife and Fisheries,
Texas Parks and Wildlife Department, and
the commercial shrimp industry
contributed to this forecast. Juvenile
brown shrimp abundance and growth
estimates are obtained through
monitoring the inshore commercial shrimp
fisheries in Texas and the inshore and
nearshore fisheries in Louisiana.
Environmental variables are further
assessed to quantify the amount and type
of habitat required for growth and
survival of young shrimp. Collectively,
these indices provide the estimate of
stock strength prior to movement into
the offshore fishery.
The Galveston Bay bait index forecasts a
yield of 21.8 million pounds of
production in offshore Texas waters from
July 2008 through June 2009. This is
approximately 4.4 million pounds below
the 1960-2006 historical average.
However, the 2008 environmental model
variables showed favorable conditions in
the bay system and predicts above
average production for Texas offshore
waters. Louisiana indices point to
slightly below average brown shrimp
yield this season from west of the
Mississippi River to the Texas-Louisiana
border. Input variables used in this
model are dependent on May catch
production from Louisiana. Due to
economic factors, many vessels in
Louisiana as well as in Texas remained
at the dock. Thus commercial fishery
data used in these models may not
adequately reflect overall shrimp
abundance this year. Despite these
factors, we chose to use this prediction
model as our best estimate of
production. Yield from Louisiana inshore
and nearshore waters will be
approximately 29.2 million pounds.
Overall, the western Gulf of Mexico
should expect an annual brown shrimp
production of approximately 51.0 million
pounds during the 2008-2009 season. This
is below the 1960-2006 historical
average of 57.0 million pounds for the
two-state area.
Peak recruitment of postlarval brown
shrimp into Texas and western Louisiana
estuaries occurs during February through
early April. Salinity, temperature, and
water height have been identified as
important factors affecting the fate of
young shrimp entering the estuaries. The
amount of favorable nursery area appears
to be related to the distribution of
high salinity waters as well as to tidal
water height in interior marshes. Bay
water temperatures greater than 68° F in
April and May have been observed in
years of above average production. In
2008, rainfall amounts were below the
historical averages; warm air and water
temperatures, high salinities and above
average tidal water heights (Tables 1
through 3) in estuarine marsh habitats
were favorable for survival and growth
of brown shrimp. Although predicted
values are below average, environmental
factors reflect a strong biological
potential.
Environmental Model
The Environmental Model is used to
predict the annual harvest related to
the historical production. The model
uses Galveston air temperature during
mid-April (the key component), rainfall
during early March, and bay water height
during late April and early May. These
components are additive in the model,
thus higher values indicate higher
catch. Although temperature during
mid-April was relatively low, rainfall
values during March and water height
(Table 3) values during April and May
were above average this year.
Collectively, the factors suggest above
average production of brown shrimp from
Texas as related to environmental
conditions conducive for optimal shrimp
growth and survival.
Catch per Unit Effort (CPUE) in the
Inshore Texas Fishery
Texas bay commercial brown shrimp catch
rates and size composition data for May
2008 were obtained from NOAA Fisheries
port agents. Catch rates recorded during
the reporting period may not adequately
portray catch-per-unit effort due to low
effort. Low dockside prices and high
fuel costs contributed to the decrease
in effort. Based on the available data,
all Texas bays experienced below average
catch rates as compared with the
(1986-2006) historical average (Table
4). Unlike previous years, white shrimp
were prevalent throughout Galveston Bay.
The May brown shrimp size composition in
San Antonio Bay was dominated by small
shrimp (100+ count). Galveston and
Aransas Bays catches were primarily of
81-100 and 71-80 count/pound shrimp,
respectively.
Baxter Bait Index
Consistently, for the past 48 years, our
most reliable estimate of subsequent
brown shrimp production off the Texas
coast comes from monitoring the
Galveston Bay bait shrimp fishery during
late April through mid-June (Baxter Bait
Index; Table 5). Notable recruitment
into the commercial bait fishery was
observed the first of week of May and
continued throughout the reporting
period. High salinities increased
available nursery habitat allowing for a
wider distribution of young brown
shrimp. As seen in the commercial bay
fishery, the bait fishery was also
limited by higher fuel prices resulting
in lower effort. Using the period from
1981 through 2007 in the bait versus
offshore landings modified regression
model, a value of 21.8 million pounds is
the estimate of production from Texas
offshore waters. This value is 4.4
million pounds below the average catch
of 26.2 million pounds for the 1960 -
2006 period.
Louisiana Inshore - Offshore
Production
Catch information from Louisiana inshore
and offshore fisheries in May is used to
estimate total production for the
biological year from May through April
(Table 6). Using 2008 May catch data
(7.4 million pounds) in our Louisiana
model, we predict a harvest of 29.2
million pounds for Louisiana west of the
Mississippi River for the 2008-2009
season. This is below the historical
average of 30.8 million pounds.
Louisiana Department of Wildlife and
Fisheries scientists estimated that 1.48
million acres of marsh with salinities
greater than 10 ppt were available this
year for brown shrimp, a decrease of
approximately 0.42 million acres as
compared to this time last year.
Moreover, record freshwater discharge
from the Mississippi River may affect
shrimp yield.
Summary
The 2008 indices of juvenile shrimp
abundance indicate a below average brown
shrimp harvest for the western Gulf of
Mexico during the July 2008 - June 2009
season. Environmental conditions favor
above average shrimp production this
year, but the total catch from the
shrimp fishery is expected to be below
average. If you would like more
information regarding this forecast, or
for other marine fishery information,
please contact us at 409-766-3500, or
visit our web site at <http://galveston.ssp.nmfs.gov/>.
Sincerely,
Roger Zimmerman, Ph.D.
Laboratory Director
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