Fisheries - scallop stocks

The Ministry of Fisheries (now Ministry for Primary Industries) undertakes ongoing research and monitoring to determine the state of the scallop fishery and sustainable catch limits. Surveys of commercial beds are undertaken in Northland and Coromandel including beds at Colville, Mercury Islands, Kuaotunu-Opito. Reports and data available at links below.

Estimates of harvestable biomass, population size structures

Selected sites within Northland and Coromandel fisheries.

Stratum within general areas: Sarah's Gully – 2758548, 6496554, NZMG, 1:50,000, AREA Opito Bay – 2760434, 6494880, NZMG, 1:50,000, AREA Opito Bay deep – 2762382, 6496636, NZMG, 1:50,000, AREA Mercury Cove – 2758606, 6507220, NZMG, 1:50,000, AREA Mercury Deeps – 2756872, 6504948, NZMG, 1:50,000, AREA Colville – 2729469, 6505915, NZMG, 1:50,000, AREA

Surveys were conducted in the Coromandel fishery almost annually between 1978 and 1999, with coverage of the fishery increasing with time.

Currently stratified random surveys, by dredge, also historically used divers. Survey designs were refined over the years using historical survey data, catch-effort information, a review of optimisation procedures, and discussions with managers and fishers.

Estimations of stock biomass only. Scallop population fluctuations (cause of mortality) still poorly understood. Gaps in collection: There was no survey in 2000. Data quality: Not reported Attribute accuracy: Not reported Completeness: Not reported

reports, graphs Digital Format: MS Word, MS Excel

Predictions on sustainable yields. Determining the roles of species in their ecosystems.

See Ministry for Primary Industries

Ongoing

Scallop fishing in Coromandel started 1982 or late 1970s. Additional comments: Between 1992 and 1994, survey results were used to estimate Provisional Yield (Cryer 1994) and set catch limits for the Coromandel fishery. The minimum legal size for scallops taken commercially in the Coromandel fishery was reduced from 100 to 90 mm at the start of the 1995 season. The management plan for the Coromandel fishery (for 1995 to 1997 seasons) adopted an assessment regime whereby the available yield was still calculated using Provisional Yield based on the abundance and biomass of scallops greater than 100 mm shell length, pending research into more appropriate methods. This research was completed in late 1997 when the management plan expired. A more typical Current Annual Yield estimator was adopted in 1998, based on predicted start-of-season recruited biomass and estimates of reference fishing mortality incorporating incidental effects of the dredge method on scallop growth and mortality (Cryer & Morrison 1997). "Black gill" condition reported in several species of filter feeding bivalves around the Coromandel Peninsula in 1999 (Diggles et. al. 2000).