Data Collection

Fishery Dependent Sampling (sampling from the fleet)

Landings, or daily vessel unloads, are reported monthly to the National Marine Fisheries Service.  Detailed daily activity of each menhaden vessel in the Gulf fleet is reported via the Captain's Daily Fishing Report, or CDFR.  Captains of each vessel record details on every purse-seine set that the crews make in a given day.  Information is recorded on the time and duration of every purse-seine set, the location, weather conditions, and finally, the estimated number of fish caught in each set.  These reports are sent by the companies weekly to the NMFS for entry into the gulf menhaden database.  Currently, annual CDFR data sets span from 1982 to 2009; each annual data base contains information on over 20,000 individual purse-seine sets.  Additionally, the 1979-1981 CDFR data forms have been scanned and archived for future use.

Biostatistical protocols for sampling the reduction fishery consist of a sampler randomly selecting a vessel at dockside, and then randomly selecting 10 fish (20 in 1964-1971) from a bucket of fish obtained from the top of the fish hold.  Each of these fish is measured for fork length (mm) and weight (g), and a scale patch is removed for ageing.  The sample is not assumed to represent the entire fish hold, but rather the last purse-seine set of the fishing day.  In recent years, about 4,000-5,000 fish have been processed annually.   At the end of the fishing season, biostatistical data are merged with landings on a port-week basis to produce estimated landings of fish at age (in numbers).  Estimates are summed over all port-weeks for the entire fishing season to produce annual estimates of total catch at age.

Fishery Independent Sampling (agency sampling)

Each state agency has its own sampling protocols which identify juvenile gulf menhaden abundance based on catch per-unit-effort.  Data are acquired from Mississippi, Louisiana, and Texas using bag seines, beam plankton nets, and otter trawls.  The indexes of juvenile abundances are then used to estimate recruitment into the fishery in coming years.