Each year since 2009 to present Marine Institute (MI) staff and contractors sample at sea on board fishing vessels fishing for shellfish species to observe and record fishing activity. Approximately 50-80 Shellfish at sea observer sampling trips are completed annually although this varies year on year and was lower earlier in the time series. In 2021 a Skipper Self-Sampling Programme was set up to enable skippers to record catch and effort data at operational level. Skippers fill out 10-14 fishing days of catch and effort data along with the associated biological data for 8 strings of pots, across the fishing season. The data recorded in observer and self-sampling trips include the quantities of catches, landings and discards of several species such as Homarus gammarus (Lobster), Cancer pagurus (Brown Crab), Maja brachydactyla (Spider Crab), Necora puber (Velvet Crab), Buccinum undatum (Whelk), and the bycatch associated with these fishing events. Furthermore, all individuals or a sample (depending on catch volume) of the target species captured are measured to the nearest millimeter. Other biological traits such as the sex, whether females are berried and whether any individuals are missing or have regenerating chelae is recorded providing a significant amount of valuable biological information on these species. The observer and skipper self-sampling programmes provide data at the level of individual fishing operations in contrast to fishery dependent data collection programmes which report aggregated data. The sampling levels of both programmes are low relative to the thousands of trips undertaken by the Shellfish fishing fleet annually. Furthermore there is high variance between vessels (related to location of fishing). The low sampling level and high variance reduces precision and even accuracy in these data sets especially when reported at local level where the data supports are diluted.