Research Document - 2008/002
Scallop Production Areas in the Bay of Fundy: Stock Status for 2007 and Forecast for 2008
By Smith, S.J., S. Rowe, and M. Lundy
Abstract
This document reviews the status of scallop stocks in Scallop Production Areas (SPAs) 1, 2, 3, 4, 5, and 6 (Bay of Fundy and Approaches) for 2006–2007 with advice for the fisheries in 2007–2008.
Landings in SPA 1A were 168t against a TAC of 150 t for the 2006/2007 season. Commercial catch rates have been declining from a recent peak in 2002. Since the 1998 year-class had recruited to the fishery in this area, recruitment has been minimal and the abundance of commercial size scallops has been fished down. There may be above average recruitment in the 8 to 16 mile area along its border with SPA 4 in two to three years, otherwise recruitment is expected to be below average in the SPA 1A area. Population biomass estimated to be 1245 t (meats) in 2007 has increased over the estimate for 2006 (1233 t) and is above the median biomass of 1080 t (1997 to 2006). A total catch of 150 t in 2007/2008 is expected to result in a probability of 0.16 that exploitation rates will be greater than 0.20. This catch level is expected to result in no change in biomass between 2007 and 2008 assuming that meat weight-at-shell height does not change over that time. Given a catch of 150 t in 2007/2008, a total catch of 150 t in 2008/2009 should result in a probability of 0.30 that the exploitation rate will exceed 0.20.
For SPA 1B landings were 220 t against a TAC of 200 t for the Full Bay Fleet in the 2006/2007 season, and 173 t against a TAC of 200 t for the Mid and Upper Bay fleets in the 2007 season. Commercial catch rates have either increased slightly (Full Bay and Mid-Bay) or stayed the same (Upper Bay) in 2007 relative to last four years and all are above the low levels of the mid to late 1990s. Pre-recruits observed in the 2004 and 2005 survey near the Mid-Bay/Upper Bay line are now recruiting to the commercial fishery. There is no evidence of any above average recruitment for the next two to three years. "Population biomass estimated to be 2380 t (meats) in 2007 has increased over the estimate for 2006 (1983 t) and is above the median biomass of 2006 t (1997 to 2006). A total catch of 400 t in 2007/2008 is expected to result in a probability of 0.38 that exploitation rates will be greater than 0.20. This catch level is expected to result in a 9% increase in biomass between 2007 and 2008 assuming that meat weight-at-shell height does not change over that time. Given a catch of 400 t in 2007/2008, a total catch of 400 t in 2008/2009 should result in a probability of 0.39 that the exploitation rate will exceed 0.20. SPA 2 is considered to be marginal habitat for scallops and is not monitored regularly. Stock status in this area was last assessed in 2006.
Landings for SPA 3 in 2006/2007 were 119 t against a TAC of 200 t. Commercial catch rate has declined in this area since the high of 2003 and the 2007 estimate of 14.6 kg/h is just above the long-term median. The small increase in the 2007 survey biomass estimate for commercial size scallops over the 2006 biomass estimate was probably due to the increase in meat weight only, as mean numbers per tow stayed the same over the two years. The 2007 survey estimated higher than average abundances of scallops in the 10 to 40 mm size range in the Brier/Lurcher area. Better estimates of the strength of this year-class should be available from the 2008 survey. Population biomass estimated to be 449 t in 2007 has decreased over the estimate for 2006 (537 t) and is below the median biomass of 638t (1996-2006). A total catch of 50 t in 2007/2008 is expected to result in a probability of 0.29 that exploitation rates will be greater than 0.20. This catch level is expected to result in a 9% decrease in biomass between 2007 and 2008 assuming that meat weight-at-shell height does not change over that time.
Total landings for SPA 4 in 2006/2007 were 68 t against a TAC of 100 t. Commercial catch rate in 2006/2007 was unchanged from 2005/2006 at 11.38 kg/h. The increased catch rate observed in October 2007 (15.9 kg/h) may be due to increased meat weight at shell height. The survey biomass estimate indicates that there was little change in biomass in 2007 relative to 2006 and that the current population levels are similar to those in the mid-1990s with below average recruitment expected in the upcoming year. The mean numbers of scallops with 20–50 mm shell height in 2007 were three times greater than the mean number in 2006, but were well below the densities observed for the above average 1998 year-class at the same size. These scallops are probably two year-olds and will not recruit to the fishery until 2009/2010. Population biomass estimated to be 712 t (meats) in 2007 has increased over the estimate for 2006 (672 t) and is below the median biomass of 835 t (1983 to 2006). A total catch of 100 t in 2007/2008 is expected to result in a probability of 0.44 that exploitation rates will be greater than 0.20. This catch level is expected to result in an 8% increase in biomass between 2007 and 2008 assuming that meat weight-at-shell height does not change over that time. Given a catch of 100 t in 2007/2008, a total catch of 100 t in 2008/2009 should result in a probability of 0.46 that the exploitation rate will exceed 0.20.
A total of 3.8 t were landed in SPA 5 in 2007 against a TAC of 10 t. Commercial catch rate in 2007 (10.8 kg/h) was lower than that observed for 2006 (12.5 kg/h) and below the long term median of 19.8 kg/h (1977–2006). The mean number per tow of commercial size scallops in 2007 (131/tow) is above the 1997–2006 median (120/ tow) but little recruitment is expected for the next two years. The TAC for 2008 should not exceed the average catch of 10t over the period 1997 to 2007 (excluding the high catch in 2004).
For SPA 6 landings to 26 November 2007 were 68 t against a TAC of 140 t. The Mid-Bay catch rate may be a better refection of population trends than the Full Bay catch rate as it is based on somewhat higher levels of effort, however, this index does not indicate any large changes in the last 10 years. The abundance of commercial size scallops appears to remain unchanged from 2006 in SPA 6A and 6B and has possibly declined in SPA 6C. Above average recruitment was detected in SPA 6A and 6B; however, in the case of the latter, this recruitment appears to be confined to Duck Island Sound. There is no evidence to advise increasing the TAC over its current level.
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