Population: Brown and white shrimp are abundant in Louisiana and the Gulf of Mexico
Gear: Otter trawls, butterfly nets, skimmer nets
Bycatch: Finfish and other crustaceans are often caught in shrimp trawls. Atlantic croaker, anchovy, spot, sea catfish, gulf menhaden and blue crabs are some of the most commonly caught species. Sea turtles such as the Kemp’s Ridleys and Loggerheads have been recorded as bycatch in shrimp trawls. Federal laws required shrimp trawls to incorporate Turtle Excluder Devices into their trawls (allows sea turtles to escape from the net if caught) or for skimmer nets, follow a tow-time (can only pull a net for a certain amount of time, depending on the season).
The range of the brown shrimp is from Massachusetts all along the Atlantic coast, throughout the Gulf of Mexico, to the east coast of Mexico to Campeche. White shrimp range from New Jersey along the Atlantic coast, throughout the Gulf of Mexico, down to Campeche.
Both Brown and White shrimp have similar life cycles: they spawn in the deeper waters of the Gulf of Mexico, the fertilized eggs hatch into planktonic larvae, develop through a series of molts and return to the estuaries through the tidal passes as post larval shrimp or juvenile shrimp.
The marshes serve as the nursery grounds for juvenile shrimp; growth rates are dependent on salinity and temperature. As the shrimp continue to grow, they begin their journey back into the deeper waters of the open bays and eventually to the Gulf of Mexico. Spawning may begin as early as 12 months old. Major differences between the brown and white shrimp are the seasonal occurrence of each species. Brown shrimp are typically more prevalent in the spring and white shrimp in the fall.
Both shrimp species have 5 pair of walking legs and 5 pair of swimming legs. Differences between the species can be hard to distinguish; brown shrimp have a groove located on either side of the rostrum and may have a greenish or purplish color on their tail fin.
Several species of shrimp occur in Louisiana waters. Brown shrimp (Farfantepenaeus aztecus) and white shrimp (Litopenaeus setiferus) make up the majority of what is harvested by commercial and recreational fishermen. In 2009, 114 million pounds of white and brown shrimp were landed by commercial fishermen in Louisiana.
In general, trawls are used to harvest shrimp. Commercial fishermen are required to follow the Endangered Species Act requirements concerning sea turtles; this includes either adding a turtle excluder device to the trawl or following tow time limits. The fishery is regulated through monitoring, license requirements and seasonal closure of areas.
To commercially harvest and sell shrimp, fishermen will need a commercial fishing license, a gear license for each gear used and a vessel license in the vessel owner’s name.
Shrimp seasons are flexible and are fixed by the Louisiana Wildlife and Fisheries Commission based upon biological and technical data relative to shrimp populations in Louisiana waters. Generally, the spring inshore season will begin in early to mid-May and may extend into July. The fall inshore season usually begins in early to mid-August and extends into December.
LDWF biologists assess the population status through a coast wide monitoring system of extensive field sampling. Weekly trawl samples provide biological data such as size and species caught, as well as the physical parameters, including salinity and temperature. Areas found to have large amounts of small shrimp can be closed to commercial fishing, which allows the juveniles a chance to grow to a harvestable size.
Juvenile shrimp on Grand Isle Beach, photo by LDWF.
For more information: http://www.wlf.louisiana.gov/regulations