ikely, there will never be a North Carolina stock assessment for bay scallop or shrimp. They are the two species the Division of Marine Fisheries currently manages that are considered annual crops.

Annual crop species are species that are short-lived and highly fecund — capable of producing large numbers of offspring, or recruits. The productivity of annual crop species is often highly dependent on environmental factors, such as weather and water temperature. For example, cold stun events can kill off overwintering white shrimp. Because environmental conditions can be highly variable, so can the annual number of recruits that join the population each year. A favorable environment is more likely to result in the production of a large number of recruits in these species. For this reason, it is possible for annual crop species to increase from low abundance in one year to high abundance the next year.

For annual crop species, natural mortality can often exceed fishing mortality. Natural mortality is mortality due to factors other than fishing such as predation, disease and old age. Although fishing does reduce the population size over a fishing season, fishing would not normally reduce recruitment strength for the following year, unless the spawning stock — mature fish — has been reduced below some minimum threshold.

Annual crop species are typically difficult to assess and/or are data limited. Because environmental factors have a major role in influencing the size of the population for these species, collection of environmental data is critical to understanding their population dynamics; however, the role the environment plays often is not well understood, and so is difficult to account for in an assessment model. Loss and degradation of habitats also play a big role in the abundance of both shrimp and scallops, thus making them even harder to assess.

Another issue that makes assessment difficult for annual crop species is timing. The division has a process in place for conducting stock assessments of state-managed species. This process can take up to a year and a half or more. Annual crop species exhibit substantial year-to-year variability and there is little to no relationship between one year’s recruits and the next. For this reason, fishery managers should act on information about the most current conditions, but the nature of the assessment process makes it impossible to provide the necessary information in a timely manner. It is not possible to provide the most current data without compromising the integrity of the assessment process.