Science Advisory Report 2019/041

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

Summary

Overall – Divisions 2HJ3KLNOP4R

• Landings remained near 50,000 t from 2007 to 2015 but have since steadily declined to a two-decade low of 27,700 t in 2018. Overall effort remained at approximately 3.5 to 4.5 million trap hauls per year over that time.
• Overall CPUE was at a time-series low in 2018.
• Despite modest increases in the past two years, the trawl survey exploitable biomass index has remained at its lowest level for the past four years. Meanwhile, the trap survey index has declined by nearly 60% in the last two years to a time-series low.
• Despite modest increases in some divisions in the past two years, overall recruitment into the exploitable biomass will remain low in most divisions in 2019.
• Total mortality in exploitable crab is estimated to be near time-series’ averages in most divisions. It has declined from very high levels in most divisions during the past two years, with the exception of Division (Div.) 3K, where it remains at a time-series high. 
• Exploitation rate indices were at or near time-series highs in most divisions in 2017. In 2018, exploitation rates subsequently increased to a new high in Div. 3L Inshore, remained high in Divs.2HJ, 3K, and 3LNO, and declined to be near or below long-term average levels in Divs. 3Ps and 4R3Pn.
• In 2019 most divisions are projected to fall within the cautious zone of the proposed Precautionary Approach Framework. Div. 3L Inshore would be in the critical zone. These projections assume status-quo landings.
• The thermal habitat index (defined as the areal extent of <2°C bottom water) has returned to near-average conditions in all divisions in recent years. Broad-scale climate indices appear favourable for improved recruitment to occur in most major areas of the stock range over the next few years.
• Ecosystem conditions in the NL Bioregion are indicative of an overall low productivity at the lower trophic levels (phytoplankton and zooplankton) in recent years and changes in zooplankton community structure that may impact the transfer of energy to higher trophic levels. 
• A sharp decline in male size-at-maturity (i.e. terminal molt size) in most divisions in recent years may dampen short-term prospects for recruitment into the exploitable biomass.
• Elements of the Precautionary Approach Framework presented in this assessment are tentative. Limit Reference Points defining the critical zone have been established by a peer-reviewed Science process, but Upper Stock Reference lines defining the cautious and healthy zones remain under development.

Assessment Division 2HJ

• Landings have remained near 1,700 t for the past four years while effort has remained consistent.
• Standardized CPUE has remained near the decadal average in recent years.
• The exploitable biomass index has changed little during the past 15 years. A modest increase in 2018 reflects an increase in residual biomass.
• Recruitment into the exploitable biomass has changed little during the past 15 years. The 2018 trawl and trap surveys suggest recruitment will remain unchanged in 2019.
• Total mortality in exploitable crab had been at its highest level in recent years, but declined slightly in 2018.
• The exploitation rate index has been above the long-term average for the past three years. Status quo removals in 2019 would decrease the exploitation rate index, but it would remain at a relatively high level.
• Following the proposed Precautionary Approach the stock status would be in the provisional cautious zone in 2019.
• Size-at-terminal molt in males has precipitously declined in recent years, suggesting potentially dampened short-term recruitment prospects into the exploitable biomass.
• Poor monitoring and coverage levels of the collaborative post-season (CPS) trap survey in recent years compromises the integrity of biomass estimation. Efforts should be made to ensure the survey is fully complete with protocols followed moving forward.

Assessment Division 3K

• Landings have remained relatively low for the past three years (6,000 t in 2018). Effort has been maintained near a two-decade low for the past six years.
• Standardized CPUE increased in 2018 from a time-series low in 2017, but remains below the times-series average.
• Despite localized improvements, the post-season trawl and trap survey exploitable biomass indices have remained near time-series lows for the past five years.
• Despite localized improvements, the post-season trawl and trap survey indices of recruitment into the exploitable biomass have remained near time-series lows for the past five years.
• Total mortality in exploitable crab has remained at its highest level during the past four years.
• The exploitation rate index declined from a decadal high to near time-series average levels in 2018. Under status quo removals in 2019 the exploitation rate index would be unchanged.
• Following the proposed Precautionary Approach the stock status would be in the provisional cautious zone in 2019.
• Size-at-terminal molt in males has precipitously declined in recent years, suggesting potentially dampened short-term recruitment prospects into the exploitable biomass.

Assessment Division 3L Inshore

• Landings declined by 56% from a time series high in 2015 to 3,700 t in 2018. In 2018, the landings were 16% below the TAC. Effort remained at a time series high in 2018.
• Standardized CPUE has declined by 68% since 2013 to below 5 kg/trap, its lowest level in the time series.
• The exploitable biomass is severely depleted. The post-season trap survey exploitable biomass index remained near a time-series low in 2018. Crab Management Areas (CMAs) 6B and 6C had total catch rates of approximately 1 kg/trap in the 2018 surveys.
• Recruitment into the exploitable biomass steadily declined to a time-series low in 2017. In 2018, recruitment indices from DFO and CPS trap surveys remained near their lowest levels. Localized improvements in overall biomass available to the fishery could occur within the next 2 years.
• The overall trap survey-derived exploitation rate index has increased since 2013 and remained at its highest observed level in 2018. Status quo removals would maintain the exploitation rate at a time series high in 2019.
• Size-at-terminal molt in males has precipitously declined in recent years, suggesting potentially dampened short-term recruitment prospects into the exploitable biomass.
• Following the proposed Precautionary Approach, the stock status would be in the critical zone in 2019.

Assessment Division 3LNO Offshore

• Landings declined by 43% from 2016 to 14,000 t in 2018 because of reductions in the TAC, to the lowest level in two decades. Effort expanded rapidly from 1992 to the mid-2000s and has oscillated at a similar level since.
• Standardized CPUE most recently peaked near a time-series high in 2013 and has since declined by 49% to its lowest level since 1992.
• The trawl-derived exploitable biomass index showed a modest increase in 2018, but both it and the trap-derived exploitable biomass index remain at or near time-series’ lows.
• Recruitment into the exploitable biomass has been at or near time-series lows in both the trawl and trap surveys in the past three years, but increased slightly in 2018.
• Total mortality declined from its highest observed level in 2016 to a relatively low level in 2018.
• The exploitation rate index increased by a factor of five from 2014 to 2017, and remained high in 2018. The exploitation rate index would decline to near the long-term average with status quo removals in 2019.
• Following the proposed Precautionary Approach the stock status would be in the provisional cautious zone in 2019.
• Size-at-terminal molt in males has precipitously declined in recent years, suggesting potentially dampened short-term recruitment prospects into the exploitable biomass.

Assessment Division 3Ps

• Landings increased from decadal lows to 1,900 t in 2018. The landings exceeded the TAC, which was set at 1,792 t. Effort has declined by 60% since 2014 to be near its lowest level in two decades.
• Standardized CPUE increased from time-series low levels in 2016 and 2017 to more than 5 kg/trap in 2018.
• The in-season trawl survey exploitable biomass index was at a time-series low in 2016, but has improved during the past two years. The post-season trap survey index suggests an increase in the exploitable biomass throughout the major fishing grounds.
• Recruitment into the exploitable biomass was near a decadal high in 2018, with the exception of Fortune Bay. Despite a small decline in recruitment available to the 2019 fishery, survey data of pre-recruit abundance suggest short-term prospects are positive relative to the recent 2013-16 low period. The distribution of pre-recruit crab appears concentrated on the major fishing grounds of the division.
• Total mortality in exploitable crab has varied considerably throughout the time series, but was low in 2018. The exploitation rate index was near its lowest observed level in the time series in 2018 and status quo removals would result in the exploitation rate index being near a time series low in 2019.
• Following the proposed Precautionary Approach, the stock status would be in the provisional cautious zone in 2019.
• Discards declined sharply in 2018 to be near the long-term average. A continuation of current measures is recommended to re-establish a strong residual biomass to help minimize discards.

Assessment Division 4R3Pn

• Landings have steadily declined since a recent peak in 2013 and were 250 t in 2018. Meanwhile, effort has remained at a low level.
• Standardized CPUE has declined since 2013 to below the long-term average.
• The exploitable biomass is severely depleted, with few residual crab in the population. The trap survey exploitable biomass index most recently peaked in 2012 and declined to a time series low in 2017. The index increased slightly in 2018, reflecting localized improvements in CMA 12EF.
• Recruitment into the exploitable biomass was low from 2014 to 2017, but survey data from 2018 suggest localized improvements may occur in 2019, particularly in CMA 12EF.
• The overall exploitation rate index declined to below the long-term average in 2018. Status quo removals in 2019 would result in little change to the exploitation rate index.
• Poor monitoring coverage throughout this division results in large uncertainty in the biomass estimates provided in 2018 and predictions for 2019. Caution is warranted when developing conclusions from these estimates.
• This division was not included in the scientific proposed Precautionary Approach due to data deficiencies.

This Science Advisory Report is from the February 19-21, 2019 2HJ3KLNOP4R 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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