Initially, we will collect 24 brood stock parents, spawn to produce the first batch of Red Drum offspring (10,000+ offspring). Fin clips will be obtained from all brood stock and genotyped. The offspring will be raised in outdoor ponds until they reach a size of 6-10 inches, when they will be released into the wild as part of first-ever Red Drum restocking effort in the Louisiana. Offspring will be tagged for scientific data collection and documentation of program success. One or more tagging methods will be employed including a genetic approach termed Parentage Based Tagging (PBT). The benefit of PBT is that they are permanent, whereas other tag types are subject to shedding or loss. Inclusion of both tagging approaches (genetic & typical) will allow for a comparison to be made between the two. Tag information will be added to a reference database for the re-capture phase of the program. A parental brood stock genetic identification panel will be developed by the genetics lab for this particular brood stock spawn and will serve as the reference genetic database for 2022.
The next component consists of sampling to capture/re-capture individuals. This can occur through LDWF's marine fisheries independent gillnet monitoring program, as well as in collaboration with the recreational fishery with RFRI.net and CCA Louisiana (statewide nonprofits dedicated to the conservation of Louisiana's marine resources) leading this effort. External tag information from captured fish will be provided to the relevant partners. Tagged fish can be recovered as soon as the offspring are able to be sampled in the fishery. Tissue samples will be taken from both tagged and untagged fish and provided to the contracted genetic lab for PBT analyses. For the PBT analyses, these fish will be genotyped and compared to the parental broodstock genetic identification panel developed by the genetics lab. This will allow individuals to be identified as hatchery or wild fish. If they are hatchery fish, their age and origin of stocking can be recovered providing highly accurate information on the success of the enhancement program.
Parentage Based Tagging in Louisiana
Understanding the contribution of hatchery produced individuals to a fishery is paramount to management, as many have questioned the economic costs and benefits of hatchery based stock enhancement. Historically, the standard approach has been to tag and recapture hatchery fish using a variety of methods including, but not limited to coded wire (CWT) or dart (DT) tags, chemical tagging of otoliths, or employing natural marks. All of these approaches are time-consuming from a marking perspective. Most recently, genetic approaches have been incorporated into stock assessment and have been shown to overcome problems (i.e. tag loss, tag-based handling mortality, etc.) associated with tagging. In general, this approach is known as Parentage-Based-Tagging, and consists of annually genotyping the brood stock and developing a diagnostic genetic identification panel. By genotyping the brood stock, millions of the hatchery offspring are “genetically tagged” through their DNA. This genetic information can be recovered from any individual at any life history stage through the acquisition of a non-lethal fin clip for genotyping. Next, genetically tagged offspring are released into the wild and re-captured through agency monitoring or in collaboration with the recreational fishery. These recaptured fish are genotyped and compared to the parental brood stock genetic identification panel and individuals can be identified as hatchery or wild fish. This approach has a high detection rate (i.e. hatchery vs. wild), with most studies showing detection rates of more than 96%. If the recovered fish are hatchery fish, information such as hatchery origin, fish age, or release site can be determined and estimates as to the percentage of hatchery fish in the overall population can be determined to assess the success of a hatchery program annually. This overall approach has been used with salmonids in the Pacific Northwest for more than a decade with tremendous success.