Science Advisory Report  2013/023

Assessment of Lobster (Homarus americanus) in Lobster Fishing Areas (LFA) 35-38

Summary

The Fishery

• Current lobster (Homarus americanus) landings are very high in the Bay of Fundy (Lobster Fishing Areas, LFAs 35-38) as a whole and in the individual LFAs.  Landings in 2011-12 were more than 5 times the 50-year annual mean (1,628 t), were more than 2 times higher than 2005-06 (latest year in the 2007 assessment), and each of the last 5 years has been a new record high. 
• Reported effort in LFAs 35-38 has increased both in terms of average days fished since 1997-98 and in total trap hauls since 2005-06 (1.2 times those reported for 2005-06).
• Commercial catch per unit effort (CPUE in kg/trap haul) in the Bay of Fundy has increased in all LFAs since 2005-06.  In the Bay of Fundy as a whole, the 2011-12 CPUE (1.9 kg per trap haul) was 1.8 times that of 2005-06.  This increase in CPUE, coupled with increased fishing effort, explains the increase in landings in the Bay of Fundy since 2005-06.
• The largest size of female lobsters in the legal portion of the catch in commercial traps has trended downward in the last decade in some parts of the Bay of Fundy (LFA 36 and part of LFA 35).

Assessment

• Two fishery dependent indicators of the abundance of legal size (landings and commercial CPUE) are at record highs.
• The catch rate in the Fishermen’s and Scientists Research Society standard traps is considered an indicator of sublegal abundance. The time series is short, but the catch rates in the last two years are two of the highest for LFA 35.
• The proportion of summer Research Vessel survey sets with lobsters indicates a wider distribution of lobsters at sufficient density to be caught routinely in the trawl survey.
• The mean number of lobster per tow in the summer Research Vessel survey was consistently low from 1970 to the late 1990s and increased thereafter. Numbers increased dramatically in the most recent years (2011 and 2012).   
• There is insufficient information to reliably estimate the exploitation rate for the Bay of Fundy as a whole, but the rate is expected to be lower than in LFA 34. Given that the environmental conditions remain favorable for lobster, the current levels of fishing effort do not appear to threaten the sustainability of lobster stocks in LFAs 35-38.
• Historical and current estimates of size at maturity for the Bay of Fundy (North Head) were evaluated.  Evidence indicates that the size at maturity has declined in the Bay of Fundy since the 1980s.
• The contribution of egg production from larger females has declined in recent years. 
• Given the important gap between the minimum legal size and size at onset of 50% maturity (SOM50), and the low reproductive capability of small mature individuals, additional measures that increase or maintain egg production from larger sizes (e.g. protection of large females greater than SOM50) should be considered.   Such measures can improve stock resilience if conditions become less favorable for lobster production.
• Despite an increase in lobster abundance over the last 20 years, observed egg production has not increased in the same manner.  Mating success of small mature females was lower and, thus, their contribution to egg production was lower than expected.  
• A precautionary approach proposed for lobster in LFAs 35-38 utilizes reference points for the abundance of legal sizes (landings, commercial catch rate), and legal and sublegal sizes (summer RV catch rate).  These indicators are above their Upper Stock References (USR), indicating that the lobster stock in LFAs 35-38 is in the healthy zone.
• Landings-based reference points for the abundance of legal size lobsters are based on the median of the lobster landings from 1985-2009.  The USR for LFAs 35-38 as a whole is 1,575 t.  The 3-year running mean is 6,936 t for the season ending 2011-12, putting these LFAs in the healthy zone, well above this USR.
• A proposed USR for abundance of legal size lobster is 50% of the median commercial CPUE for the period 2005-06 to 2008-09.  The current 3-year mean (1.6 kg per trap haul) is well above the proposed USR (0.58 kg per trap haul).
• A proposed fishery-independent USR for legal and sublegal lobster abundance is 80% of the median catch rate in summer Research Vessel survey in the Bay of Fundy for the period 1985-2009.  The median for this period is 2.4 lobsters per tow, the proposed USR is 80% of this, or 1.9 lobsters per tow.  The 3-year running mean as of 2012 was 25.7 lobsters per tow, which is well above the proposed USR.

Ecosystem Considerations

• Based on previous patterns in the North Atlantic Oscillation, warmer than average water temperatures might be expected on the southwest Scotian Shelf and Bay of Fundy in the next few years.  In terms of longer term trends in temperature, there is a slightly increasing trend in the Bay of Fundy that may be significant, but the Halifax station indicates no long term trend in temperature.
• The trends in the summer Research Vessel survey biomass indices for potential predators of lobster (e.g. Atlantic wolffish, cod, cusk, haddock, longhorn sculpin, sea raven, spiny dogfish, white hake) indicate most are at low levels relative to their long-term means.  
• The area affected by lobster traps (fishery footprint) in any given year in LFAs 35-38 is calculated to be less than 0.05% of the total area.

This Science Advisory Report is from the February 12-14, 2013, Review of Framework and Assessment for LFA 34-38 Lobster Stocks: Part 2 - 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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