Research Document - 2013/055
The February 2013 assessment of Northern Shrimp (Pandalus borealis) off Labrador and Northeastern Newfoundland
By D. Orr and D. Sullivan
Abstract
The February 2013 Northern Shrimp (Pandalus borealis) assessment was performed for NAFO Div. 2G, Hopedale + Cartwright Channels as well as Hawke Channel + Div. 3K, which correspond to shrimp fishing areas (SFA) 4, 5 and 6, respectively. Status of the resource in each area was inferred, in part, by examining trends in commercial catch, effort, catch per unit effort (CPUE), fishing pattern and size/sex/age composition of the catches. Fisheries independent data were obtained from annual autumn multispecies research bottom trawl surveys into SFA’s 5 and 6 (1996-2012), as well as, summer Northern Shrimp Research Foundation (NSRF) - Fisheries and Oceans Canada (DFO) shrimp based bottom trawl research surveys into SFA 4 (2005–12). These surveys provide information on distribution, abundance, biomass, size/ sex composition and age structure of shrimp.
Catches increased from 22,000 t in 1994 to over 114,000 t by 2003-04 due mainly to increases in Total Allowable Catch (TAC). The overall 2004-05 TAC was set at 111,552 t and maintained until 2008-09 when it was increased to 120,344 t. This TAC was maintained through to 2009‑10; however, due to operational and commercial constraints, it was not taken. Under the Integrated Fisheries Management Plan (IFMP) Precautionary Approach (PA) framework the SFA 6 TAC decreased by 33 % to 52,387 t by 2011-12 due to resource status declines within SFA 6, resulting in an overall TAC of 87,007 t for that year. Resource status in SFA 6 improved in 2011, therefore, the 2012-13 SFA 6 TAC was increased to 60,245 t; resource indices remained high in SFA 4 therefore the TAC in SFA 4 was increased to 13,018 t resulting in an overall TAC of 96,563 t for the 2012-13 management year. It was anticipated that this TAC will be taken by March 31, 2013.
The SFA 6 large vessel catch per unit effort (CPUE) increased between 1989 and 1997 and oscillated at a high level until 2006-07, thereafter it declined until 2009/10 but has since been increasing. The small vessel CPUE showed a similar pattern. The SFA 5 large vessel CPUE increased from 1992 to 2001 and has oscillated around this higher level since then. Several factors including resource management decisions, market conditions, searching, and distribution of striped shrimp (Pandalus montagui) relative to Northern Shrimp, influenced SFA 4 large vessel CPUE bringing into question its use as a fishery performance indicator.
The resource decreased from a peak in 2006 to near 1996 levels in the south (SFA 6); remained near average on the mid Labrador Shelf (SFA 5) and increased in the north (SFA 4).
The SFA 6 fishable biomass index increased from 310,000 t in 1997 to a peak of nearly 670,000 t in 2006 then declined steeply to 295,000 t in 2010, increased to 409,000 t in 2011 before returning to 316,000 t by 2012. The trend in female spawning stock biomass (SSB) index reflected the trend in the fishable biomass index decreasing to 187,000 t in 2012, which is comparable to the beginning of the time series. Annual total mortality among age 4+ shrimp from RV surveys increased from approximately 34 % to 58 % since 2001. In the long term, the exploitation rate index has varied around 15 %. The exploitation rate decreased from 2004‑05 to 2009-10 and increased in the following two years.
Research survey SSB was assessed to be in the Cautious Zone, within the IFMP PA Framework, for the third time in the four most recent years. The 2012-13 exploitation rate is expected to be about 15 %. If the 60 245 t TAC is maintained through 2013-14 and taken the exploitation rate will increase to 19 %; the third highest level in the time series.
The SFA 5 fishable biomass index increased from around 90,000 t in 1996-99 to 184,000 t in 2001 and has since been approximately 150,000 t with the 2012 estimate at 147,000 t. Female spawning stock biomass (SSB) index increased from 40,000 t in the 1996-99 period to 96,000 t in 2001 but has since decreased with the 2012 estimate at 63,000 t. The SFA 5 exploitation rate has varied without trend around 15 % over most of the time series. Annual female total mortality oscillated between about 35-75 % over the period 1998-2011 averaging about 60 %. Research survey SSB was assessed to be in the Healthy Zone within the IFMP PA Framework. The 2012-13 exploitation rate is expected to be about 16 %. If the 23,300 t TAC is maintained through 2013-14 and taken then the SFA 5 exploitation rate will remain at 16 %.
The SFA 4 fishable biomass index increased from 62,000 t in 2005 to 180,000 t by 2009, decreased to 127,000 t in the next year before increasing to 191,000 t in 2012. Similarly, the female spawning stock biomass (SSB) index increased from 35,000 t in 2005 to 140,000 t by 2009, decreased to 71,000 t in 2010 then increased to 110,000 t in 2012. Annual female total mortality oscillated between about 40-50 % over the period 1999‑2008. Due to high numbers of ovigerous females, no estimates available since then. Exploitation rate, within SFA 4, has been between 6 % and 9 % since 2007-08 and the current estimate is 7 %. Research survey SSB was assessed to be in the Healthy Zone, within the IFMP PA Framework, and it is anticipated that the 2012-13 exploitation rate will be less than 10 %.
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