LDWF Fishery Management Decisions Based On Data From Dependent and Independent Sources

story by LDWF Staff

Many fishermen wonder how the Louisiana Department of Wildlife and Fisheries develops recommendations for fishery management decisions. In part, the answer lies with the anglers themselves.

LDWF biologists carefully weigh all available data when making recommendations on when to open and close recreational and commercial fishing seasons and the setting of daily bag and size limits. A primary source of that data is field sampling.

Fisheries biologists conduct two different types of sampling; fishery independent and fishery dependent sampling. The latter involves the participation of recreational and commercial anglers. Their participation is vital in helping the department make the right call on management determinations.

The following text includes a description of each type of sampling.

Fisheries Independent Sampling

LDWF biologists sample fish populations during independent sampling by using trawls, gill nets, electrofishing, trammel nets, oyster scrapers and other devices

Biologists collect information on a wide variety of species such as spotted seatrout, red drum, black drum, oysters, blue crab, brown shrimp, white shrimp, largemouth bass, crappie, and catfish among others. These efforts provide valuable biological and ecological data.

“Every year is different, every season is different and every fish is different,” said LDWF Biologist Harry Blanchet.

Every year, sampling results are compared to historic data from as far back as the mid-1980s for finfish, the late ‘60s for shrimp and crab and the early ‘70s for oysters. These comparisons are used to identify trends in the fishery over time. The accuracy of the data indicates to what extent the information collected during sampling efforts represents the fishery as a whole.

An example of independent sampling is the work LDWF does prior to the opening of the spring inshore shrimp season. Biologists begin pulling trawls and counting and measuring shrimp in the state’s bays for about a month during April. The goal is to monitor the sizes and growth of the shrimp and how broadly they are distributed to estimate when they are going to be a harvestable size.

Throughout the season, biologists will collect samples of shrimp to monitor the sizes and quantities available. The department will recommend a closure when biologists begin seeing a large number of white shrimp recruiting into the bay.

“We need to provide opportunities for those white shrimp to grow so at that point we close the season,” Blanchet said. “Then we monitor the estuarine area until those white shrimp start growing. When they reach a harvestable size, the Louisiana Wildlife and Fisheries Commission will look at our recommendation and public testimony and set the fall inshore shrimp season.”

Similar sampling and regulatory action is taken for other species.

Fisheries Dependent Sampling

Fisheries independent sampling only tells part of the story, how many species are available for capture, along with their size and location.

In order to tell the other half of the story - the one that estimates how many of each species were harvested by anglers - fishery dependent data is also necessary.

In fisheries dependent sampling, biologists are dependent on recreational and commercial fishermen to provide them with their catch information. This is done through surveys such as the dockside portion of the LA Creel survey or the trip ticket program for commercial landings. Biologists interview fishermen at boat launches and record information about their catch on that particular day. The survey usually takes about five minutes. Blanchet said LDWF has done everything it can to make the survey as convenient for recreational fisherman as possible.

Only one person on the boat has to be interviewed rather than the entire crew. Despite the improvements, Blanchet admits that the survey is often considered an inconvenience to fishermen coming off a long, hot day on the water. LDWF continues to develop ideas to make the survey easier for anglers.

“We try to keep it as short as possible,” Blanchet said. “We’ve spent a lot of time asking the questions: Do we really need this information? Is there a better way to collect this information? How can we collect this without creating any additional burden on the anglers?”

During the survey, biologists count, measure and record the gender of fish. Blanchet said it is important that biologists collect and record information about the fish to ensure accurate numbers and proper identification of each species.

Biologists target certain species more than others based on occurrence and assign their efforts accordingly. For example, it takes much less manpower and hours to sample spotted seatrout than a more rarely caught fish, such as tarpon.

“We would need biologists sitting at every dock every day looking for every fish that came across,’’ Blanchet said. “That would obviously be awfully expensive for something that’s a relatively rare species. So we need a balance between relative importance and sampling manpower.”

Biologists must also make sure samples are coming from marinas across the entire state so the results aren’t biased.

LDWF biologists have also collected ‘trip tickets’ since 1999, a source of fisheries dependent sampling from the commercial fishery. Every commercial fisherman is responsible for recording their catch in the LDWF trip ticket program to help monitor commercial harvest. Biologists also collect age data from commercial fish harvest.


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