FORECAST FOR THE 2006 BROWN SHRIMP SEASON IN THE WESTERN GULF OF MEXICO, FROM THE MISSISSIPPI RIVER TO THE U.S. - MEXICO BORDER

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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 23, 2006

To All Concerned:

FORECAST FOR THE 2006 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 NOAA Fisheries Southeast Fisheries Science Center's Galveston Laboratory forecast brown shrimp production from the western Gulf of Mexico for the upcoming year (July 2006 – June 2007). Data obtained from NOAA Fisheries Galveston Laboratory, NOAA port agents, National Climatic Data and Weather Centers, Louisiana Department of Wildlife and Fisheries, Texas Parks and Wildlife Department, and the commercial shrimp industry contribute to this forecast. Juvenile brown shrimp abundance and growth estimates are obtained by monitoring the inshore commercial shrimp fisheries in Texas and the inshore and nearshore fisheries in Louisiana. In addition, environmental variables are measured to assess the favorability of conditions in habitat for growth and survival of young shrimp. Collectively, these indices provide an estimate of inshore stock strength prior to shrimp movement into the offshore fishery.

The 2006 abundance indices are varied relative to offshore brown shrimp production estimates. The Galveston Bay bait index forecasts a below average year at 23.8 million pounds from offshore Texas waters from July 2006 through June 2007. The 2006 Louisiana indices point to an above average yield of approximately 37.8 million pounds of brown shrimp this season from west of the Mississippi River to the Texas-Louisiana border. Overall, the western Gulf of Mexico could expect an annual brown shrimp production of approximately 61.6 million pounds during the 2006-2007 season. This is above the 1960-2004 historical average of 56.8 million pounds for the two-state area.

Postlarval brown shrimp begin entering estuaries in Texas and western Louisiana in mid-February and continue through July, depending on environmental conditions. Several waves of postlarve may enter; however, peak recruitment occurs from February through early April. A wide array of environmental and biological parameters affects the fate of young shrimp entering the estuaries. Three environmental variables, temperature, salinity and water height, have been correlated with subsequent shrimp production. Optimal shrimp growth has been documented in waters of greater than 68° F. Favorable nursery area appears to be related to the distribution of high salinity waters as well as tidal water height in interior marshes. As in 2005, rainfall this year has been below normal for Texas and western Louisiana (Table 1). While monthly average air temperatures were warmer than historical levels, cold fronts occurring in mid-February and the latter part of March dropped temperatures for several days and resulted in low tides in estuaries. This may have increased shrimp mortality and decreased the amount of available nursery area during this critical time. Warmer air temperatures in April and May accompanied by high salinities, required for optimal growth and survival of young shrimp, were observed this year (Tables 1 and 2); however, small shrimp predominated throughout our monitoring period, notably in Texas bays.

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. Temperature, rainfall and water height values were above average this year (Table 3), and suggest below average production off Texas as related to environmental conditions conducive for optimal shrimp growth and survival.

Catch-per-Unit-Effort in the Inshore Texas Fishery

Texas bay commercial brown shrimp catch rates (heads-on; pounds per hour) and size composition data for May 2006 were obtained from NOAA Fisheries port agents. However, we note that catch rates
recorded this spring may not adequately portray brown shrimp catch-per-unit effort due to low shrimping effort in some Texas bays. Smaller than average shrimp, low dockside prices and high fuel costs were cited as reasons for the decrease in effort. Based on the data available, all Texas bays experienced below average catch rates as compared to the historical average (Table 4). Matagorda Bay experienced one of the lowest catch-per-unit effort as compared to the 1986 through 2005 historical average. Small shrimp predominated in all Texas bays. The dominant size category in San Antonio and Galveston Bays was 81-100; all other Texas bays had 100+ count per pound shrimp.

Baxter Bait Index

For the past 46 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). Strong recruitment into the commercial bait fishery was consistent with the historical trend with the first wave occurring in April. Catch-per-unit-effort was decreasing during the last week of the survey (second week of June), suggesting peak recruitment into the fishery had occurred. Using the bait versus offshore landings regression model (1981 - 2005), a value of 23.8 million pounds is forecast for 2006 production in Texas offshore waters. This value is 2.4 million pounds below the long-term (1960 – 2004) average catch of 26.2 million pounds.

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). High fuel costs and low shrimp prices in combination with the detrimental effects of last year’s hurricanes changed shrimp effort patterns this year. Fewer vessels were active; however, catch rates (catch-per-unit-effort) were high. Using May 2006 brown shrimp catch (12.0 million pounds) in our Louisiana model, we predict a harvest of 37.8 million pounds for Louisiana west of the Mississippi River for the 2006-2007 season. This is above the historical average of 30.6 million pounds. Favorable nursery conditions during the spring may have improved Louisiana’s production. Louisiana Department of Wildlife and Fisheries scientists estimated that 2.29 million acres of marsh with salinities greater than 10 ppt were available this year for brown shrimp, an increase of approximately 1.38 million acres as compared to this time last year.

Forecast Summary

Based on 2006 brown shrimp abundance indices, brown shrimp production off Texas will be below average for the July 2006-June 2007 season. Louisiana production, on the other hand, will be above average for the May 2006 through April 2007 season. 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/galv>.

Sincerely,
Roger Zimmerman, Ph.D.
Laboratory Director