Science Advisory Report 2017/023

Assessment of Newfoundland and Labrador (divisions 2HJ3KLNOP4R) Snow Crab

Summary

Divisions 2HJ3KLNOP4R

• Landings peaked at 53,500 t in 2009 and have since gradually declined to 42,000 t in 2016. Divisions 3LNO have accounted for about 80% of the landings in recent years.
• Fishery catch per unit of effort (CPUE) was at or near historical lows in most divisions in 2016.
• The overall exploitable biomass index has declined by 80% since 2013. All divisions are at or near their lowest observed levels of biomass, with an overall decline of 40% in 2016.
• Overall recruitment into the exploitable biomass was at its lowest observed level in 2016. No improvement or further reductions in recruitment are expected in the next 3–4 years. Thermal habitat, pre-recruit biomass, and predation indices collectively suggest poor broad-scale recruitment prospects.
• Total mortality in exploitable crabs has increased to be at or near time series’ highs and pre-recruit fishing mortality rates have been at decadal highs in all divisions in recent years.
• Status quo removals would maintain exploitation rate indices above long–term average levels in most divisions. Divisions 3LNO, where the majority of remaining biomass occurs, will elevate to an exceptionally high level of exploitation.

Divisions 2HJ

• Landings have remained relatively low at less than 2,000 t since 2011. Meanwhile, effort has been substantially reduced and remained at or near its lowest level in the past four years.
• CPUE increased steadily from 2011–15 but decreased throughout the division in 2016 to a relatively low level. No improvements are anticipated in 2017.
• The trawl survey and collaborative post-season (CPS) trap survey-based exploitable biomass indices both increased sharply in 2014 and since declined by about half to relatively low levels.
• Recruitment has been relatively low throughout the 2000s. It spiked to a recent high in 2014 but subsequently decreased to more typical levels in both the trap and trawl surveys in the past two years.
• Short-term recruitment prospects appear poor as the pre-recruit biomass index was at or near its lowest level in the past two years.
• Despite abrupt annual fluctuations, the pre-recruit fishing mortality index has been increasing since 2005. It was at its highest level in a decade in 2016.
• Total mortality in exploitable crabs was at its highest observed level in 2016.
• While below historic peaks, the exploitation rate index doubled to 60% in 2016. Exploitation rates above 50% are associated with high levels of soft-shell discards. Status quo removals in 2017 would increase the exploitation rate index to 67%.

Division 3K

• Landings declined by 63% since 2009 to 5,600 t in 2016, a time series’ low. Effort has remained near its lowest level for the past five years.
• CPUE has been low for the past six years reflecting recent lows in most management areas. It is expected to remain low in 2017.
• The post-season trawl and trap survey exploitable biomass indices both declined since 2008 to their lowest observed level in the past two years.
• Recruitment is at or near time series’ lows throughout most of the division.
• Recruitment is expected to remain low in the short term with trawl and trap pre-recruit indices near time series’ lows throughout the division.
• Maintaining current removals would leave the overall exploitation rate index unchanged in 2017, reflecting slight changes throughout most of the division. However, White Bay (crab management area [CMA] 3B) would double, to a historical high.

Divisions 3LNO Offshore

• Landings have remained at 22,000-29,000 t since 1999. Effort has gradually increased over this period, to a historic high in 2016.
• CPUE declined by a third from near a time series’ high in 2013 to a two decade low in 2016. Substantial declines have occurred in all but management area MSex in recent years and further declines are anticipated in 2017.
• Both the trawl and trap surveys show considerable spatial contraction in high catch rates of exploitable crabs in recent years. The trawl survey exploitable biomass index, which covers the entire division, has precipitously declined since 2013 to a historic low. Both indices declined by about 50% in 2016, with the CPS trap survey index declining between 27–74% in the various management areas.
• Overall recruitment was at a historic low in 2016, reflecting low levels throughout most of the division.
• Recruitment prospects are very poor. The pre-recruit biomass index has been at its lowest level for the past three years.
• The pre-recruit fishing mortality index has been at or near the time series’ high in the past two years.
• The exploitation rate index doubled to 60%, a historic high, in 2016. Status quo removals would double the index again in 2017, with increases occurring in all management areas.

Division 3L Inshore

• Landings increased throughout the 2000s and remained at about 8,000 t since 2013. Effort had oscillated without trend from 2005–16 but increased by 40% in 2016 to a time series’ high.
• Overall CPUE was near its highest observed level during 2014–15 but abruptly declined by about 40% in 2016 to its lowest level in a decade. This reflected decreases ranging from 20-48% in the various management areas.
• The post season trap survey exploitable biomass index changed little from 2004–15 but declined by a third in 2016. This reflected decreases ranging from 12–46% in the various management areas.
• Overall recruitment into the exploitable biomass has steadily declined since 2010 to a time series low. Recruitment indices from DFO and CPS trap surveys in all management areas were at or near their lowest levels in 2016.
• Recruitment is expected to remain low in most management areas in the short-term as inferred from pre-recruit indices from DFO and CPS trap surveys. However, improvements appear likely for Bonavista Bay (CMA 5A).
• The overall trap survey-based exploitation rate index increased gradually from 2006–16 to a time series’ high. Maintaining status quo removals would increase the exploitation rate by 52% in 2017. This reflects projected increases of 14-85% in all management areas, which would each remain near or achieve new time series’ highs.

Subdivision 3Ps

• Landings declined from a recent peak of 6,700 t in 2011 to a time series low of 1,200 t in 2016. Effort reached a historic high in 2014 and has since decreased by half, with only 40-60% of the TAC taken in the past two years.
• CPUE has steadily declined since 2009 to a record low in 2016, reflecting precipitous declines throughout most of the Subdivision in recent years.
• The exploitable biomass index declined by 88% since 2010 to a time series low in 2016.
• Overall recruitment has declined since 2009 to its lowest observed level.
• Recruitment is expected to remain low in the short term (2-3 years) as the pre-recruit biomass index has remained at its lowest level for four consecutive years.
• Total mortality in exploitable crabs declined from its highest level in 2013 to about average in 2016. Coincidentally, the exploitation rate index has also declined by more than half since its 2013 peak due to the substantial decline in fishing.
• The impact of maintaining the current level of fishery removals on the exploitation rate is unknown.
• Concern is expressed that discards comprised half the catch in 2016. The four highest levels in the pre-recruit fishing mortality index have occurred during the past four years. Continuing to fish under elevated mortality levels on sub-legal-sized crabs could potentially impair reproductive capacity.

Divisions 4R3Pn

• Landings increased from a historic low of 190 t in 2010 to between 700-900 t since 2012. Effort has been relatively unchanged since 2012.
• Overall CPUE has been low throughout the time series relative to most other divisions. However, most management areas within Divisions 4R3Pn experienced catch rates near time series’ highs during 2012–14. CPUE has declined back to low levels in most management areas in the past two years but remains relatively strong in CMAs 12C and 12G.
• The post-season trap survey exploitable biomass index most recently peaked in 2011 and has since gradually declined, reflecting patterns in most surveyed areas.
• Overall recruitment most recently peaked in 2012 and has since declined to low levels in all surveyed areas.
• Recruitment prospects appear relatively weak for the next 2-3 years, as pre-recruit indices have been low in most surveyed areas following relatively high levels within the 2008–13 period.
• The overall exploitation rate index has increased since 2013 in all surveyed areas. Status quo removals would elevate the exploitation rate index to a new high, predominately reflecting a large increase in the Bay of Islands (CMAs 12EF).

Ecosystem Perspective

• The ecosystem changes observed in the late 1980s and early 1990s involved the collapse of the finfish community, and the increase in shellfish. Consistent signals of finfish rebuilding appeared in the mid-late 2000s, which coincided with the decline in shellfish. Despite the observed increases in finfish, overall ecosystem biomass is still significantly below pre-collapse levels.
• Finfish biomass has been relatively stable in 2010–15, but recent surveys are suggesting a downward trend. This is most evident on the Grand Bank (Divisions 3LNO). Overall, it appears that the conditions that led to the start of finfish rebuilding have weakened. This may be linked to the simultaneous reductions in capelin and shrimp availability, as well as other changes in ecosystem conditions.
• Predation mortality on Snow Crab has increased since the late 2000s and early 2010s in most divisions, and shows important differences in magnitude across ecosystem units. Southern Newfoundland (Subdivision 3Ps) has predation levels an order of magnitude higher than other areas. Still, predation mortality in the Grand Bank (Divisions 3LNO) and Newfoundland Shelf (Divisions 2J3K) has coarsely increased five-fold over the last 4 to 5 years.
• Trends in predation mortality suggest that this factor may already be an important driver for Snow Crab in Southern Newfoundland (Subdivision 3Ps), and it may become one in other areas in the short to medium term.

This Science Advisory Report is from the February 21-24, 2017 Newfoundland and Labrador Snow Crab Assessment. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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