Science Advisory Report 2021/009

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

Summary

Overall – Divisions 2HJ3KLNOP4R

• Landings have declined since 2009 (53,400 t) to their lowest level in 25 years (total 26,400 t in 2019), reflecting decreasing TACs. Only Assessment Division (AD) 3Ps experienced increased landings in recent years.
• Effort was at or near decadal lows in all ADs during 2019.
• Fishery CPUE increased to or remained near time-series averages within each AD during 2019, with the exceptions of ADs 3L Inshore and 3LNO Offshore, where it is near historic lows within their respective time-series.
• The overall exploitable biomass has increased in both trawl and trap surveys during the past 1-2 years, but remains near historic lows. In 2019, the largest increases occurred in ADs 3K, 3LNO Offshore, and 4R3Pn, while all other ADs had little change or conflicting signals. The coverage of the trawl survey in 2019 was severely reduced due to weather in Divs. 2HJ3K, such that biomass estimates, particularly in AD 2HJ, are likely an overestimate of true stock status.
• Fishery Exploitation Rate Indices (ERIs) were near or below time-series averages in all ADs in 2019, with the exception of ADs 2HJ and 3L Inshore. Status quo removals would further reduce exploitation rates in all ADs in 2020, with the exception of AD 2HJ, where it would remain high.
• Total mortality in exploitable crab has decreased in all ADs over the past 3 years. It remains highest in AD 2HJ and lowest in AD 3LNO Offshore.
• Recent climate conditions and pre-recruit abundance indices suggest favourable prospects for recruitment into the exploitable biomass over the next 2-4 years in most ADs.
• In 2020, all ADs are projected to be in the provisional cautious zone of the DFO Science proposed Precautionary Approach Framework, with the exception of AD 3LNO Offshore, which is projected to be in the provisional healthy zone.

Environment

• Cold bottom temperatures, mostly driven by the Cold Intermediate Layer (CIL), are favorable for the early benthic stages of Snow Crab. These cold conditions are associated to the positive phase of the North Atlantic Oscillation (NAO). The recent NL climate has experienced these cold conditions between the mid-1980s and the mid-1990s, and from about 2012 to 2017. Since Snow Crab biomass is highly correlated with a 6-8 year lagged NAO index, this recent cold period suggests improved environmental prospects for Snow Crab.
• Chlorophyll concentration and zooplankton biomass were below normal in the mid-2010s, increasing to values above the long-term (1999-2015) average after 2017. Additionally, there have been changes in zooplankton community structure (less large energy-rich, and more small less energy-rich copepods) as well as changes in seasonality (weaker spring and stronger summer and fall zooplankton signals) which may change the quality and timing of food availability for upper trophic levels.
• Ecosystem conditions in most of the NL bioregion are indicative of limited productivity of the fish community. Total biomass levels remain much lower than prior to the collapse in the early-1990s. After some recovery since the collapse in the Newfoundland Shelf and Grand Bank ecosystem units, current levels of total biomass are reduced from those observed in the early-2010s.
• The predation index indicates that current predation rate on Snow Crab appears of similar level in the Newfoundland Shelf (2J3K) and Southern Newfoundland (3Ps). These are an order of magnitude higher than the estimated level for the Grand Bank (3LNO). While predation mortality remains among the highest in recent years, they have shown important declines from the peak levels observed in the 2016-2018 period. The conditions that allowed groundfish (known predators of crab) rebuilding in the mid to late 2000s appear to have eroded. If environmental conditions remain favourable, these declines in predation pressure could improve the prospects for Snow Crab in the coming years.

Assessment Division 2HJ

• Recent and ongoing data deficiencies in most assessment metrics are increasingly affecting stock assessment methods.
• This is the only AD not showing recent or projected improvements in the exploitable biomass. Continued high fishery exploitation rates appear to be impairing potential recovery of the exploitable biomass.

Assessment Division 3K

• Localized trap surveys do not yet show improvements of the same magnitude in the exploitable biomass evident in other assessment indices in the major management areas. However, this is consistent with a delayed response of trap surveys to changes in stock size.

Assessment Division 3L Inshore

• There is considerable spatiotemporal variability in stock status among management areas. Recent and projected improvements in the exploitable biomass are most apparent in Bonavista and Trinity Bays (CMAs 5A & 6A).

Assessment Division 3LNO Offshore

• AD 3LNO Offshore is the major contributor to overall stock status trends. Projected improvements in the exploitable biomass are consistent in most management areas.

Assessment Division 3Ps

• There are conflicting signals between the status of the exploitable biomass between the trawl (decrease in 2019) and trap (increase in 2019) survey indices.
• Recent increases in the exploitable biomass appear to be concentrated in the major fishing grounds and there is uncertainty if they will be sustained into 2020.

Assessment Division 4R3Pn

• Recent and ongoing data deficiencies in most assessment metrics are increasingly affecting stock assessment methods.
• Improvements into the exploitable biomass appear limited to Bay St. George (CMA 12C) and the Bay of Islands (CMA 12EF).

This Science Advisory Report is from the February 25-26, 2020 regional peer review meeting on  2GHJ, 3KLNO, 3Ps, 4R3Pn 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.

Science Advisory Report 2021/009 (PDF, 3,638 KB)

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