Research Document - 2002/018

Scallop Production Area 4 in the Bay of Fundy: Stock status and forecast)

By S.J. Smith and M.J. Lundy

Abstract

Scallop landings from Scallop production area (SPA) 4 in 2000/2001were 102 t (meats) against a total allowable catch of (TAC) of 110 t. As of 28 January 2002, 243 t had been landed against the current 2001/2002 TAC of 400 t. Fishing effort (hours) in the 2000/2001 season was the lowest in 26 years. Commercial catch rates to 7 January 2002 have averaged 47 kg/h in 2001/2002, compared to 16 kg/h in the previous season and are expected to increase by the current season's end. Since October 2001, average meat weights in the catch have decreased to 11 g. The average percentage of meats less than 8 g was at 7.4 percent as of the end of January 2002. The recommended upper limit for the percent of meats less than 8 g is 10 percent. The 2001 research vessel survey indicated that, due to the higher than average growth rate, the 1998 year-class was already recruiting to the fishery and had increased the biomass of commercial size scallops (shell height > 80 mm) in 2001, sooner than expected. The remaining portion of the abundant 1998 year-class will recruit to commercial size by the summer of 2002. Concerns about large increases in natural mortality as occurred in 1989/1990, are being addressed by a joint monitoring program conducted with industry. The population dynamics of this scallop population were modelled using a state-space form of the delay-difference model. A new model for the relationship between trends in the number of clappers (dead paired shells) and natural mortality was also included in the population model. Model parameters were estimated using Bayesian Gibbs sampling methods. Posterior distributions of projected biomass were used to evaluate in-season increases to the current TAC and potential future harvests against a biomass reference point based upon a yield-per-recruit model.

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