Gulf shrimp system

Email lawrence.r.beerkircher@noaa.gov

Landings From The Gulf Of Mexico Ports. For the states of Florida, Alabama, Mississippi, Louisiana , and Texas

The shrimp data collection procedures were changed in 1978 in several ways. The vessel identification number (i.e., the Coast Guard documentation number) was not included in dealer records. All dealer records were coded with 9s in the vessel identification field. The vessel identification number was recorded when an interview was conducted, and it was also included on the interview records. Another change that was implemented at this time was to record only the month in which the trip occurred, instead of the month and day.

In 1981, these procedures were discontinued and the pre-1978 procedures were re-implemented, i.e., the former method of recording the vessel identification number and the month and day when the trip was unloaded for both dealer and interview records.

Pounds and value for the shrimp catches are collected by size, although the data collection procedures have changed over the years. Prior to 1984, all landings were grouped into a standard set of eight market or size categories (i.e., <15, 15-20, 21-25, 26-30, 31-40, 41-50, 51-67, and >68 shrimp count per pound). In 1984, port agents began recording the landings data in the size ranges in which the shrimp were purchased by dealers.

In addition to changes in size ranges, more detailed information on fishing effort was collected beginning in 1984. This change included the addition of data on the number of trawls, the size of trawls, the period of the day that the shrimping occurred (i.e., day or night), and the actual number of hours fished.

If the shrimp data are used in a fixed record format, it is essential that all records associated with a single trip be identified and used properly. There are several fields that should be used to identify the records associated with a fishing trip. A number is recorded on each shrimp schedule that port agents prepare; however, this number is not unique for the entire Gulf of Mexico. The schedule number is only unique for a given port and month (the month in the date of landing field. A suggested means of associating all of the records with a single fishing trip is to sort the data by port, month and schedule number, and as an additional assurance the official number can be used in the sort. Because the data on pounds and value are disaggregated for each record, totals for pounds and value for a specific species, port, area of fishing, etc. can be accomplished by simply adding all of the data in the respective fields. However, determining the number of fishing trips and the amount of fishing effort (i.e., days fished) is more complicated.

Data on the number of trips are provided in the NUMBER_OF_TRIPS field and is always 1 for unconsolidated records. As discussed above, port agents may combine the information for several trips into a consolidated record. In this case, the value entered in the Trip field would be the number of trips combined by the port agents in the respective schedule. The number of trips is not provided on every computer record; it is only provided on one of the records for each trip. Thus, the user must be careful to associate all of the computer records for a specific trip in order to assure that the correct numbers of trips for the desired analysis are counted.

Care must be taken when trip information is needed that requires records for a single trip to be split. For example, if an analysis of white shrimp is being done and the number of fishing trips on which white shrimp were caught is needed, the analyst has to make sure that the trips on which fishermen caught both brown and white shrimp are counted. It is possible that the number of trips is recorded on a brown shrimp record and not a white shrimp record and unless special provisions are made, the number of trips on which white shrimp were caught could be under-counted. Furthermore, care must be taken, because double counting of trips can occur if the number of trips is calculated separately for several species and then added together without an accurate accounting of the number of trips on which more than one species were caught.

Calculating the number of days fished has a different type of problem associated with it. As described above, information on the number of days fished is only provided on Interview records. Because interviews are conducted for only a sample of the fishing trips, the number of days fished must be estimated by expanding the sample information to the total universe that is desired. For example, if the total number of days fished is needed for shrimp caught off the coast of Texas, this number would have to be estimated by expanding the days fished information on the interview records to the total records for all shrimp caught in areas off the coast of Texas.

Because different assumptions can be made to accomplish whatever expansions are needed, it is possible that different analysts could calculate different estimates of days fished for essentially the same research question. A method of estimating directed fishing effort for individual species of shrimp is presented in Nichols,1984. Literature Cited Nichols, S. 1984. Updated assessment of brown, white, and pink shrimp in the U.S. Gulf of Mexico. Southeast Fisheries Center, Miami, Florida. 21 p.

Dealer Codes

We rebuilt the historical dealer codes from the old two digit numeric to the nine column character dealer code beginning in 2001.

So in pre 2001, there will only be two significant digits anyway.

And after 2001 the state Dealer Codes were used.

Data requested is confidential unless at the granularity of the data requested there are more than three dealers reporting data. Data is non-confidential if there is no dealer information.