Science Advisory Report 2022/012

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

Summary

Overall – Divisions 2HJ3KLNOP4R

• Landings increased from a 25 year low in 2019 (26,400 t) to 29,100 t in 2020. All Assessment Divisions (ADs), except ADs 2HJ and 4R3Pn, experienced increased landings in 2020.
• Effort was at or near decadal lows in all ADs during 2020, except AD 2HJ.
• Fishery CPUE increased to or remained near time-series averages within each AD during 2020, with the exceptions of ADs 3Ps and 4R3Pn, where it was near time-series highs.
• The overall exploitable biomass has increased in both trawl and trap surveys during the past 3 years from historic lows. In 2020, the largest increases occurred in ADs 3K and 3LNO Offshore in the trawl survey, and AD 3Ps in the trap survey. In 2020 there was no trawl survey in AD 3Ps.
• Fishery Exploitation Rate Indices (ERIs) were near time-series lows in all ADs in 2020 except AD 2HJ where it remained high at around 50%. Status quo removals would further reduce exploitation rates in all ADs in 2021, with the exception of AD 2HJ, where it would remain very high at around 75% of the exploitable biomass index.
• Total mortality in exploitable crab has decreased in all ADs in recent years. It remains highest in AD 2HJ and lowest in AD 3LNO Offshore. There is no updated total mortality estimate for AD 3Ps in 2020 but the relatively high presence of old-shelled crab in trap survey data suggests total mortality remains low.
• 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.
• With status quo removals in 2021 all ADs are projected to be above the Limit Reference Points (LRPs).

Environment

• Cold bottom conditions are linked with a positive North Atlantic Oscillation (NAO) and are associated with habitat for the early benthic stages of Snow Crab. The recent NL climate has experienced these colder conditions between the mid-1980s and the mid-1990s, and from about 2012 to 2017. Since Snow Crab exploitable biomass is highly correlated with a 6-8 year lagged NAO index, this period suggests improved environmental prospects for Snow Crab in the short term. However, the last 3 years (2018-20) have shown a trend towards warmer and potentially less favorable environmental conditions.
• Chlorophyll concentrations and zooplankton biomass were below normal in the early and mid-2010s, increasing to values above the long-term (1999-2020) average since 2016-17. Additionally, there have been changes in zooplankton community structure over the past decade (less large energy rich, and more small less energy rich copepods) although the abundance of large calanoid copepods has increased to above-normal levels in some areas since 2017. Additionally, changes in zooplankton seasonality (weaker spring and stronger summer and fall zooplankton signals) may change the quality and timing of food availability for upper trophic levels.
• Ecosystem conditions in the NL bioregion continue to be indicative of limited productivity of the fish community, with total biomass levels much lower than prior to the collapse in the early-1990s. After some recovery since then, total biomass declined in the mid-2010s. While there have been improvements since the lows in 2016-17, especially in the Grand Bank ecosystem unit, current total biomass has not yet returned to the 2010-15 level. The improvements in 2019-20 have favored shellfish, leading to a subtle increase in their dominance in the community structure.
• The predation index indicates that current predation rate on Snow Crab appears of similar level in the Newfoundland Shelf (Divs. 2J3K) and Southern Newfoundland (Subdiv. 3Ps). These are an order of magnitude higher than the estimated level for the Grand Bank (Divs. 3LNO). Predation mortality remains among the highest in recent years. While overall predation has shown important declines from the peaks observed in 2016-18, this pattern is not homogenous within regions. Considering that the rebuilding of groundfish biomass appears to have stalled, the declines in predation pressure could potentially improve the prospects for Snow Crab in the coming years.

Assessment Division 2HJ

• Exploitation rates have been persistently high and the residual biomass is very low. Total mortality in males is high and there have been concerning declines in mature female abundance. There have been large declines in male size-at-terminal molt and short-term recruitment prospects are poor.
• Finfish predation mortality has increased rapidly in 2015-16 in NAFO Div. 2J and remains at high levels, with 2020 being the highest in the time-series.
• Recent and ongoing data deficiencies in most assessment metrics are increasingly affecting stock assessment methods.

Assessment Division 3K

• There are conflicting signals between the status of the exploitable biomass from trawl and trap surveys, with a much greater increase in the trawl survey even considering the delayed response of trap surveys to changes in stock size.
• Male size-at-terminal molt has declined in recent years and may dampen recruitment prospects moving forward.
• The exploitation rate is at a historic low for AD 3K.

Assessment Division 3L Inshore

• The spatiotemporal variability in stock status among management areas in recent years has diminished, with most CMAs rebounding from the recent time-series lows.

Assessment Division 3LNO Offshore

• This AD is the major contributor to overall stock status trends. Projected improvements in the exploitable biomass are consistent in most CMAs.

Assessment Division 3Ps

• There was no trawl survey in AD 3Ps in 2020 due to the global pandemic.
• The large increase in the fishery CPUE and trap survey exploitable biomass appear to be concentrated in the major fishing grounds.

Assessment Division 4R3Pn

• Recent and ongoing data deficiencies in most assessment metrics are increasingly affecting stock assessment, which is impacting the inclusion of AD 4R3Pn in the Department’s developing PA Framework. Notwithstanding, there were some recent signs of improvement in recruitment and biomass in the major fishing areas in AD 4R3Pn.

This Science Advisory Report is from the February 16-18, 2021 Regional Advisory Meeting on the 2HJ, 3KLNOP, and 4R 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 2022/012 (PDF, 4129 KB)

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