Science Advisory Report  2012/010

Assessment of Scallops (Placopecten magellanicus) in Scallop Production Areas 1 to 6 in the Bay of Fundy

Summary

General

• Problems with the predictions from the population models for Scallop Production Area 1A, 1B, 3 and 4 were identified in the 2009 assessment, and scientific advice on stock status was provided for the 2010/2011 fishery based on trends in survey indices and commercial catch rate time series.  In the interim, improvements to the growth models, redefinition of the survey area, and alignment of catch and survey timing in the model for SPA 3 have been incorporated into this year’s assessment advice.
• Observer coverage has not been routinely available for the scallop fleets in the Bay of Fundy. However, as part of a Species-At-Risk project, observer coverage was funded for the inshore scallop fishery in the Bay of Fundy and approaches in 2008 and 2009. Estimated discards were reported for all species.
• As in previous assessments of these SPAs, future catch levels have been evaluated for the modelled production areas in terms of a reference exploitation rate of 0.15, and whether or not the proposed catch would result in a decrease in biomass from the current year.
• Forecasts of biomass for 2012 and 2013 require estimates of expected biomass growth (and condition) and natural mortality for future years.  At present these estimates are based on current conditions and, therefore, may not reflect actual changes over the next two years.
• Development of an estimate of the spatial footprint of the Bay of Fundy scallop fishery is underway.

SPA 1A

• Landings were 278 t for the Full Bay Fleet during the 2010/2011 fishing year against a Total Allowable Catch (TAC) of 300 t.  An interim TAC of 100 t was set for 2011/2012. The average commercial catch rate in 2010/2011 declined from that in 2009/2010 and was below the long-term median.
• Since the above average 1998 year-class recruited to the fishery in this area, recruitment to the fishery has been low and the abundance of commercial size scallops has been fished down.  Recruitment to the fishery is expected to be at very low levels for at least the next two years.
• The condition factor (meat weight for 100 mm shell) had decreased from 2008 to 2010 but increased in 2011 for two of the three subareas of SPA 1A.
• The survey index of the abundance of commercial size scallops decreased by 6% in 2011 from 2010, while the biomass index in 2011 increased by 5% from 2010 due to the overall increase in condition.
• Population biomass estimated by the model was 1,147 t (meats) in 2011, unchanged from the estimate for 2010 (1,141 t) and below the median biomass of 1,251 t (1997 to 2010).  
• A catch of 200 t for 2011/2012 should result in an exploitation rate (0.16) close to the reference (0.15) and an 8% decline in biomass for 2012.

SPA 1B

• The total landings of all fleets in 2010/2011 were 259.7 t against a TAC of 400 t. The Mid Bay and Upper Bay fleets’ landings were close to their respective TACs, while the Full Bay Fleet only landed 83.6 t against a TAC of 203 t over all three subareas. Economic reasons were reported as being responsible for the reduction of Full Bay effort in SPA 1B.
• Commercial catch rates for the Full Bay Fleet in 2011 remained similar to 2010 in 28B and 28C, while indicating a 20% increase in 28D. The Mid Bay 2011 catch rate for 28B was unchanged from 2010 but had increased by 11% in 28C. The 2011 catch rate for the Upper Bay Fleet was unchanged from 2010 in 28C and 28D.
• The condition factor has declined for all subareas of SPA 1B since 2008 with greatest decline in subarea 28B.
• There do not appear to be any indications in the survey of strong year-classes that could recruit to the fishery in the next two years in any of the areas. Commercial size numbers and biomass from the survey in 2011 have remained similar to estimates from 2010 in 28C and 28D, while declining by 19% for both numbers and biomass in 28B.
• Population biomass estimated by the model was 1,745 t (meats) in 2011, a decrease of 7% from the estimate for 2010 (1,878 t) and below the median biomass of 1,881 t (1997 to 2010).
• A catch of 300 t for 2011/2012 should correspond to the reference exploitation rate (0.15) and is predicted to result in a 3% decline in biomass.

SPA 2

• This area is considered to be marginal habitat for scallops and is not monitored regularly.  SPA 2 was last assessed in 2006 (DFO 2007).

SPA 3

• Total landings for the 2010/2011 fishing year were 73.3 t against a TAC of 50 t. An interim TAC of 100 t was set for October of the 2011/2012 fishing season, and 124.5 t had been landed by October when the fishery was closed.
• Commercial catch rates for the 2011 summer fishery indicated an increase for St. Mary's Bay from 2010 but no change for the Brier/Lurcher area. Generally, October catch rates in Brier/Lurcher are very similar to the summer catch rates in the same area, but the 2011 October catch rate increased by 15% over the 2011 summer rate (and October 2010).
• This year, the survey area outside of St. Mary’s Bay has been partitioned according to areas being regularly fished or not fished at all since 2002, and separate survey indices have been developed for these areas.
• The condition factor had increased in St. Mary’s Bay from 2006 to 2010 but declined in 2011. Outside of the bay, the condition factors had declined since 2006 but increased from 2010 to 2011.
• Survey indices for both St. Mary's Bay and the fished area indicate an increase in numbers per tow and biomass for 2011 while there was no change in the estimate for the unfished area from 2010. There is evidence of a larger than average year-class in St. Mary's Bay, which should recruit to the fishery in 2013. Shell height frequencies for fished and unfished areas outside of St. Mary’s Bay do not indicate a similar large year-class.
• This year, the population model only used survey data from St. Mary’s Bay and the fished area outside of the bay. Population biomass estimated by the model was 796 t (meats) in 2011, an increase of 37% from the estimate for 2010 (579 t) and below the median biomass of 827 t (1996 to 2010).
• A catch of 150 t for 2011/2012 should result in an exploitation rate (0.16) close to the reference (0.15) and no appreciable change in biomass for 2012. This catch includes the 125 t already landed in the fall 2011 fishery.
• In general, the Full Bay Fleet is of the opinion that the assessment underestimates the biomass in the area based on the catch rates of this year’s fishery. More work is required to evaluate the consequences of these different perspectives.

SPA 4

• Total landings in 2010/2011 were 136.3 t against a TAC of 140 t. An interim TAC of 100 t was set for 2011/2012.
• The 2010/2011 catch rate changed little from the 2010 catch rate and is above the long-term median.
• The condition factor had declined from 2008 to 2010 but increased in 2011.
• Survey estimates for mean numbers indicate a 14% decline from 2010 to 2011 while survey biomass of commercial size scallops increased by 9%, probably due to the increase in condition. Given the trends in the pre-recruit estimates, low levels of recruitment to the fishery will probably continue for at least the next two years.
• Population biomass estimated by the model was 656 t (meats) in 2011, an increase of 2% from the estimate for 2010 (641 t) and below the median biomass of 767 t (1983 to 2010).
• Catches for 2011/2012 of 100 t should result in an exploitation rate (0.14) close to the reference (0.15) and is predicted to result in an 7% decline in biomass

SPA 5

• Landings in 2011 were 10 t against a TAC of 10 t.
• The 2011 average commercial catch rate increased from 2010 and was above the long-term median.
• The annual survey was discontinued as of 2009 in this SPA at the request of industry.
• The average catch of 10 t over the period 1997–2010 (excluding the high catch in 2004) has not led to marked increases or decreases in commercial catch rates over that time, which would suggest a relatively stable population size at this level of harvest.

SPA 6

• Landings in 2011 were 104 t against a TAC of 140 t.
• Both catch and catch rates for the Mid Bay Fleet have been relatively stable over the last six years. There were no landings recorded for the Full Bay Fleet in the Quota Cap reports of SPA 6 for 2011.
• The condition factor had increased in all subareas of SPA 6 from 2008 to 2010 but declined in 2011. A change in the timing of the survey from September to August may have resulted in a lower measure of condition due to spawning but previous data does not indicate such a large change would be expected to occur for only this reason.
• Survey indices for abundance and biomass decreased in all subareas of SPA 6 between 2010 and 2011. Shell height frequencies suggest that recruitment will be low for the next year. However, there were indications of a stronger than average year-class in 6B (mainly Duck Island Sound) that should recruit to the fishery in two or three years.
• The Mid Bay commercial catch rates suggest that the biomass of commercial size scallops remains unchanged over recent years, while the surveys are indicating decreases in 2011 relative to 2010. If the condition factors continue to decline for all three areas, population biomass may decrease at the current levels of catch.

This Science Advisory Report is from the Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, Regional Advisory meeting of 16–17 November 2011 on Scallops in the Bay of Fundy Assessment. Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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