The Challenger Scallop Enhancement Company Ltd. (CSEC) conducts an annual stratified survey for scallops (Pecten novaezelandiae) and dredge oysters (Ostrea chilensis) in the Challenger fishery area (Golden Bay, Tasman Bay and the Marlborough Sounds). Sampling frequency: annual (Apr/May/Jun). Surveys began in 1994 and are ongoing. The nmber of sites varies depending on survey year. Three regions: 3 to 34 strata per region. Overall, between 150 and 526 dredge tows (stations) were completed per survey. The total number of samples is 6356. Extent of site: dredged area (per station) varies from 379m2 to 3960m2. Depth of sampling: 5-71 m (chart datum). Number of replicates: 1 to 70 stations per stratum. Measured variables: Scallops (counts, weights, size frequency subsample), dredge oysters (counts, weights), bycatch (counts, weights: type of data varies depending on survey year). Environmental (depth, windforce, tow geographic position, tow time, dredge fullness). Sampling protocol & QA: Sampling protocol and initial QA set by NIWA, survey conducted by industry (CSEC).