Science Advisory Report  2011/003

Assessment of Divisions 2G-3K Northern Shrimp

Summary

• The thermal regime has been warming over the past decade. Effects of a warm regime on shrimp distribution and behaviour are unknown. However, a warm surface regime is believed, from the literature, to be detrimental to shrimp early survival and subsequent recruitment.
• Shrimp and Capelin are key forage species in NAFO Divisions 2J3KL (SFAs 5, 6 and 7). Capelin abundance is at very low levels while some groundfish are increasing. Together this may increase predation pressure on shrimp.
• Resource status was updated based on a DFO fall multi-species research vessel (RV) bottom trawl survey series (1996-2010), which provided information on shrimp distribution, abundance, biomass, recruitment, size, and sex composition in the Div. 2J portion of SFA 5 and Hawke Channel + Div. 3K (SFA 6). Trends in stock size were also inferred from fishery catch per unit effort (CPUE) and fishing patterns.
• The Northern Shrimp Research Foundation (NSRF) in partnership with DFO conducted annual shrimp based research surveys in Division 2G (SFA 4) during 2005-2010.
• The resource has been decreasing in the south (SFA 6) and remained at 2009 levels in the north (SFA 4 and 5).

SFA 6 (Hawke Channel and NAFO Division 3K)

• Catch decreased from a peak level in 2007/08 of 81,000 t to the 2010/11 TAC of 61,632 t. The TAC was reduced for 2010/11 under the IFMP PA framework.
• The large vessel CPUE increased significantly between 1992 and 1997 and remained reasonably constant until 2006. Thereafter it declined significantly until 2009 with an increase in 2010. The 2010 CPUE was close to the mean of the series. The small vessel CPUE showed a similar pattern, but there are some concerns regarding the effort data, derived from logbooks.
• Fishable biomass in the fall RV survey increased significantly from 2003 to nearly 670,000 t in 2006 and then declined to about 300,000 t by 2010. This decrease is significant. Female spawning stock biomass showed a similar pattern declining from 460,000 t in 2006 to 190,000 t in 2010.
• The recruitment indices reached a peak in 2006 and then continuously declined to near the lowest level in the time series.
• Total mortality from age 3+ in one year to age 4+ in the following year, from the RV survey data, increased from 23% to 41% over the period 2004 to 2010.
• Under the current TAC, the exploitation rate in 2010/11 would be 20% by March 31, 2011, the highest in the time series.
• Female spawning stock biomass (SSB) was assessed to be in the Cautious Zone of the IFMP PA framework for the second consecutive year and there is a declining trend. The 2010/11 exploitation rate is expected to be about 20%.

SFA 5 (Hopedale and Cartwright Channels)

• Catches increased from 15,000 t in 1997–2002 to around 23,000 t and remained at about that level until the present.
• In recent years CPUE has been above the long term mean with little change.
• Female spawning stock biomass and fishable biomass indices increased after 1999 and has since remained at or above the mean.
• The recruitment index has remained near the mean since 2003.
• Exploitation rate has varied without trend between 15-20% over the time series.
• Female spawning stock biomass was assessed to be in the Healthy Zone of the IFMP PA Framework. The exploitation rate for 2009/10 was estimated to be 19%, above the base target exploitation rate of 15% for the Healthy Zone. However flexibility is allowed in this zone and this level of exploitation is not a concern.

SFA 4 (NAFO Division 2G)

• Catches increased from 4,000 t in 1994 to 10,000 t in 2004/05 and remained at about that level until the present. 
• CPUE has increased since 2008/09 and is now above the long-term mean. This may be partially due to changes in fishing pattern.
• There was no strong evidence of change in either female spawning stock biomass or fishable biomass indices over the period 2007–2010.  The current survey female spawning stock biomass is 70,000 t while the fishable biomass is 127,000 t.
• The recruitment index was roughly twice as high in the 2008–2010 period as it was in the previous three years.
• Over the period 2006–2010, the exploitation rate has been about 9%.
• Female spawning stock biomass was assessed to be in the Healthy Zone of the IFMP PA framework. The exploitation rate is below the base target exploitation rate of 15% for the Healthy Zone.

This Science Advisory Report has resulted from a Fisheries and Oceans Canada, Canadian Science Advisory Secretariat zonal advisory process held 15-25 February 2011 on the assessment of northern and striped shrimp in Shrimp Fishing Areas (SFAs) 2-6. Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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