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Brown Shrimp Forecast 2016

FORECAST FOR THE 2016 BROWN SHRIMP SEASON IN THE WESTERN GULF OF MEXICO, FROM THE MISSISSIPPI RIVER TO THE U.S. - MEXICO BORDER
The forecast is available as a PDF* file. To download, click on the picture to the right. (The tables are only available in the PDF file.)
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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)

July 7, 2016


To All Concerned:

FORECAST FOR THE 2016 BROWN SHRIMP SEASON IN THE WESTERN GULF OF MEXICO, FROM THE MISSISSIPPI RIVER TO THE U.S. - MEXICO BORDER.


       Scientists at the National Marine Fisheries Service (NOAA Fisheries) Southeast Fisheries Science Center's Galveston Laboratory have prepared the following information on prospects for the upcoming brown shrimp season (July 2016–June 2017) in the western Gulf of Mexico. The data for the forecast comes from the NOAA Fisheries Galveston Laboratory, NOAA port agents, National Climatic Data and Weather Centers, Texas Parks and Wildlife Department, U.S. Army Corps of Engineers, and the commercial shrimp industry. Pre-season estimates of juvenile brown shrimp abundance and growth are obtained by monitoring the inshore 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 available for growth and survival of young shrimp. Collectively, these measures provide an estimate of the size of shrimp stocks prior to their movement into the offshore fishery.

       The 2016 Texas and Louisiana indices of brown shrimp abundance indicate below average production in offshore waters of the northwestern Gulf of Mexico from July 2016 through June 2017. The Galveston Bay bait index forecasts a below average year at 17.3 million pounds from offshore Texas waters. The Louisiana indices also indicate a below average brown shrimp season west of the Mississippi River to the Texas-Louisiana border (21.9 million pounds). When combined, an annual brown shrimp production estimate of approximately 39.2 million pounds can be expected in the western Gulf of Mexico during the 2016–2017 season. This is below the 1960–2014 historical average of 56.4 million pounds for the two-state area.

       Postlarval brown shrimp begin entering estuaries in Texas and western Louisiana in mid-February, depending on environmental conditions, and continue through July. Several waves of postlarve may enter the estuaries; however, peak recruitment occurs from February through early April. A wide array of environmental and biological factors affects the fate of young shrimp entering the estuaries. Three environmental variables: temperature, salinity, and tidal height, have been correlated with subsequent shrimp production.

       Similar to last year, Texas and Louisiana experienced record high rainfall this spring that subsequently led to large freshwater discharges into the estuaries (Tables 1 through 3). This unprecedented flooding in Texas, and to a lesser degree in Louisiana, most likely concentrated young shrimp at the mouth of bays and out of the nursery habitats required for optimal growth and survival. Moreover, extremely low dissolved oxygen levels are still persisting in Texas and western Louisiana’s shallow coastal waters. These extreme environmental factors may impact our forecast of harvest of brown shrimp this year since it is unknown whether survival of shrimp was reduced or shrimp just moved out of our sampling area, because of the reduced salinities and low oxygen levels.

Environmental Model

       The Environmental Model predicts the annual harvest related to the historical production (Table 3). The model uses Galveston air temperature during mid-April, rainfall during early March, and bay tidal height during late April and early May. These components are additive in the model; thus higher values indicate higher catch. The heaviest contributing factor, the temperature during mid-April, was well above average this year (72.3°F). Rainfall during early March was also well above average during the monitoring period (3.0”). Tidal height was above average during late April and early May (6.5'). Based solely on the environmental parameters, (i.e., with the exclusion of the brown shrimp abundance indices) the model suggests above average production off Texas.

Catch per Unit Effort (CPUE) in the Inshore Texas Fishery

        Texas bay commercial brown shrimp catch rates and size composition data for May 2016 were obtained from NOAA Fisheries port agents (Table 4). Data were not available for all Texas bays. Several regulatory changes went into effect in Texas last year. Two notable changes for the commercial bay fishery included an increase in the catch limit from 600 to 800 pounds and extended fishing times from 2 p.m. to 30 minutes after sunset. This year, heavy river runoff hampered the catch, effort, and shrimp size. Galveston Bay experienced lower than average catch rate with catches comprised of very small shrimp (100+ count/pound). Activity and catch rate in Matagorda Bay was low, and below the 1986–2015 historical average this year (Table 4). The brown shrimp size composition reported from Matagorda Bay was dominated by 51–60 count/pound shrimp. Catch rate in San Antonio Bay for the month of May was below average with catches comprised of small shrimp (81–100).

Galveston Bay Production/Baxter Bait Index

       For the past 55 years, the Galveston Bay Bait Index is consistently our most reliable estimate of subsequent brown shrimp production off the Texas coast. The index is derived from monitoring the Galveston Bay bait shrimp fishery during late April through mid-June (Baxter Bait Index; Table 5). Similar to last year, recruitment into the commercial bait fishery was observed at the onset of the sampling period. Juvenile shrimp were abundant; however, due to excessive rainfall, environmental conditions did not remain as favorable towards the end of the sampling period. The overall size of sampled shrimp remained small. Using the Galveston Bay Bait Index model, 17.3 million pounds of brown shrimp is predicted for 2016–2017 catch in Texas offshore waters. This is below the historical average of 25.6 million pounds for 1960– 2014 period.

Louisiana Inshore - Offshore Production

       Catch information from NOAA Fisheries port agents in Louisiana on inshore and offshore fisheries in May is used to estimate production from May through April the following year (Table 6).  Using brown shrimp catch data (2.9 million pounds), we predict a harvest of 21.9 million pounds for Louisiana west of the Mississippi River during the 2016–2017 season.  This is below the 1960–2014 historical average of 30.7 million pounds.  Mississippi River discharge was approximately 813 thousand cubic feet per second in April, slightly lower than last year.

Prediction Summary

       The 2016 indices of juvenile shrimp abundance indicate a below average year of brown shrimp production in offshore waters of the western Gulf of Mexico during the July 2016–June 2017 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://www.galvestonlab.sefsc.noaa.gov
 

Sincerely,

James Nance, Ph.D.
Acting Laboratory Director