Science Advisory Report 2013/001

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

Summary

General

• Problems with the projections from the population models for Scallop Production Area (SPA) 1A, 1B, 3 and 4 were addressed in the 2011 assessment. This year’s assessment advice uses these improved models.
• Changes were made to the survey gear used in the 2012 scallop survey in SPAs 1A, 1B, 3, and 4. A comparative survey was conducted to address the impact of the new gear on estimates of catch. The results of the comparative work indicate that the two gears were comparable and no conversion factor was required.
• As in previous assessments, 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 2012/2013 and 2013/2014 require estimates of expected biomass growth (and condition) and natural mortality for future years. These estimates are based on current conditions and, therefore, may not reflect actual changes over the next two years.

SPA 1A

• Total landings were 208.6 t during the 2011/2012 fishing season against a Total Allowable Catch (TAC) of 200 t.  An interim TAC of 100 t was set for 2012/2013.
• Commercial catch rate in 2011/2012 was 12.1 kg/h, below the long-term median (1995/96 to 2010/11) of 15.5 kg/h. Recruitment to the fishery has been low and the numbers of commercial size scallops has been fished down. Recruitment is expected to be at low levels for at least the next two years.
• The condition factor (meat weight for 100 mm shell) increased in all subareas of SPA 1A in 2012. All subareas in 1A are above the long-term median (1997 to 2011) for condition.
• The survey index of commercial scallop numbers decreased by 9% from 2011 to 2012, while the biomass index in 2012 increased by 9% from 2011 due to the overall increase in condition.
• Population biomass estimated by the model was 1,277 t (meats) in 2012, up slightly from the estimate of 1,179 t for 2011 and approximately equal to the median biomass of 1,222 t (1997 to 2011).
• A catch of 200 t for 2012/2013 is projected to correspond to the reference exploitation rate (0.15) and is predicted to result in a 9.4% decline in biomass for 2013.

SPA 1B

• Total landings of all fleets in 2011/2012 were 303.4 t against a TAC of 300 t. An interim TAC of 100 t was set for the Full Bay Fleet for the 2012/2013 fishing season.
• Commercial catch rates for the Full Bay and Mid Bay fleets have been stable over the past couple seasons in Scallop Fishing Areas (SFA) 28B and 28C. Catch rates in SPA 28D have declined for Upper Bay and Full Bay fleets.
• The condition factor increased in all subareas of SPA 1B in 2012, and now all subareas are above the long-term median.  
• The survey index of commercial scallop numbers decreased or stayed the same in all parts of SPA 1B except Scots Bay, which increased.
• Commercial biomass from the survey in 2012 has remained similar to estimates from 2011 for SPAs 28B and 28D, and decreased by 35% in SPA 28C. Recruit biomass from the survey increased in SPAs 28B and 28C.
• Population biomass estimated by the model was 1,743 t (meats) in 2012, essentially unchanged from the estimate of 1,781 t for 2011 and below the median biomass of 1,870 t (1997 to 2011).
• A catch of 325 t for 2012/2013 is projected to correspond to the reference exploitation rate (0.15) and is predicted to result in a 0.1% increase in biomass for 2013.

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 2011/2012 fishing season were 264.5 t against a TAC of 300 t.  An interim TAC of 100 t was set for the 2012/2013 fishing season, and 145.2 t had been landed by 15 October 2012 when the fishery was closed.
• For the 2011/2012 fishing season only, SPA 3 was subdivided into 3A and 3B. The TAC in 3A was set at 225 t and 261.7 t was landed. The TAC in 3B was set at 75 t and 2.9 t was landed.
• Commercial catch rates for St. Mary’s Bay declined 21% in 2012, while June catch rates for the Brier/Lurcher area in 3A and 3A+3B increased by 17 and 13%, respectively. The increase in catch rate from October 2011 to October 2012 was 19%.
• As in 2011, the 2012 survey area outside of St. Mary’s Bay was partitioned according to areas being regularly or lightly fished since 2002, and separate survey indices have been developed for these areas, referred to as “Inside” and “Outside.”
• The condition factor decreased in St. Mary’s Bay from 2010 to 2012, but it increased in the “Inside” and “Outside” areas in 2012.
• Survey indices indicate increases in commercial biomass for all subareas of SPA 3. In St. Mary's Bay and the “Outside” area, there was an increase in survey index of commercial scallop numbers, while there was a slight decrease in the “Inside” area.   
• As in 2011, the 2012 population model only used survey data from St. Mary’s Bay and the “Inside” area.
• Population biomass estimated by the model was 1,039 t (meats) in 2012, an increase of 14% from the estimate of 914 t for 2011, which was the median biomass from 1996 to 2011.
• A catch of 175 t for 2012/2013 is projected to correspond to the reference exploitation rate (0.15) and is predicted to result in a 2.3% decline in biomass for 2013.
• The population model underestimated the biomass for 2011 and 2012. If condition increases above levels seen this year, the model may once again underestimate the population biomass and a TAC above 175 t would result in a lower probability of decline in biomass than predicted. It is unlikely that this increased productivity can be sustained over the next few years without increased levels of recruitment.

SPA 4

• Total landings in the 2011/2012 fishing season were 114.1 t against a TAC of 120 t. An interim TAC of 100 t was set for the 2012/2013 fishing season.
• Commercial catch rate in 2011/2012 decreased from the 2010/2011 rate and is at the long-term median.
• The condition factor declined from 2011 to 2012.
• The survey index of commercial scallop numbers in 2012 indicates minimal change from 2011, while survey biomass of commercial size scallops increased by 9%. The survey estimate of recruits is the lowest in the time series, and low levels of recruitment to the fishery will probably continue for at least the next two years.
• Population biomass estimated by the model was 716 t (meats) in 2012, an increase of 5% from the estimate of 681 t for 2011 and just below the median biomass of 754 t (1983 to 2011).
• A catch of 110 t for 2012/2013 is projected to correspond to the reference exploitation rate of 0.15 and is predicted to result in a 12.7% decline in biomass for 2013.

SPA 5

• Total landings in 2012 were 6.0 t against a TAC of 10 t.
• Commercial catch rate decreased by almost half from 2011 and is below the long-term median. The commercial catch rate is now the fourth lowest since 1997.
• The annual survey was discontinued as of 2009 in this SPA.
• Since 2007, the average annual catch has been 6.8 t and the average catch rate has been 16.0 kg/h.

SPA 6

• Total landings for Full Bay and Mid Bay fleets in the 2011/2012 fishing season were 55.5 t against a TAC of 140 t.  
• Mid Bay catch rates in 2011/2012 decreased in all subareas of SPA 6, and are below their long-term average catch rates.  The largest decreases were observed for subareas 6B (7.0 kg/h versus an average of 10.1 kg/h) and 6D (7.6 kg/h versus an average of 14.4 kg/h).
• The condition factor increased in all subareas of SPA 6 from 2011 to 2012.
• Survey indices of commercial scallop numbers decreased by 46% and 15% in subareas 6A and 6B, respectively, and biomass decreased by 19% and 7%. In subarea 6C, there were increases in both numbers (36%) and biomass (46%).
• Shell height frequencies suggest that recruitment will be low for at least the next year.
• This year, commercial catch rates have decreased for all areas and are currently lower than their long-term averages further suggesting that biomass in SPA 6 has declined.

This Science Advisory Report is from the 13-14 November 2012 Assessment of Bay of Fundy Scallop. Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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