Science Advisory Report  2013/024

Assessment of Lobster (Homarus americanus) in Lobster Fishing Area (LFA) 34

Summary

The Fishery

• Lobster (Homarus americanus) landings in Lobster Fishing Area (LFA) 34 in 2011/12 (23,292 t) are a record high at 2.7 times the 50-year annual mean (1961 to 2010: 8,575 t), and are1.4 times higher than 2004/05 (latest year in the 2006 assessment).
• There has been a shift to a higher proportion of landings originating from midshore and offshore portions of LFA 34. Landings in the nearshore still comprise the bulk of the landings (63%) but have increased by a factor of just 1.2 since 2004/05. In the midshore and offshore, landings doubled relative to 2004/05.
• Total fishing effort as measured in terms of trap hauls has not increased since 2004/05. There have been spatial shifts in fishing effort and commercial catch rates that explain the spatial shift in landings.
• Commercial catch per unit effort (CPUE) in 2011/12 (1.1 kg/trap haul) increased substantially from 2004/05 (0.74 kg/trap haul) and from 1998-99 (0.58 kg/trap haul).
• Downward shifts in size structure were evident for some areas in the nearshore and midshore. There was no indication of a downward shift in size structure in the offshore.

Assessment

• Two fishery dependent indicators of the abundance of legal sizes (landings and commercial CPUE) are at record highs. 
• A standardized CPUE index and a Temperature Corrected Abundance Index both indicate the abundance of sublegal lobsters in the last 2-3 years is the highest since 1999-00.
• The increasing trend in the summer Research Vessel survey, number of lobsters per tow in the Eastern Gulf of Maine area, is consistent with the increasing trend in lobster landings in LFA 34.
• The mean number of lobsters per tow in a joint industry/DFO trawl survey (ITQ survey) in LFA 34 has increased since 2000, with the highest values in the last 3 years. Catch rates are much higher in the nearshore, with a mean of over 240 lobsters per tow in each of the last 3 years, compared to 8-15 lobsters per tow in the midshore and less than 5 in the offshore.
• Exploitation rates in LFA 34 overall (0.8 for females) have not increased since 2000-01 but are high relative to other lobster assessment areas. There is mixed evidence for increased exploitation in the nearshore in the last 10-12 years.
• A truncated size distribution observed in the nearshore for decades suggests that exploitation rates have been high nearshore for many years. Exploitation rate is lower in the offshore portion of LFA 34 (0.49 for females) and has not increased since 2000-01.
• Size at onset of 50% maturity for 2011 was estimated at 96.5 mm carapace length in Lobster Bay, which is similar to a previous estimate of 95 mm. Only a small portion of females below the minimum legal size reach maturity.
• Despite increases in lobster abundance, the potential and observed egg production indices for subareas of the nearshore and midshore for the most recent time period showed no increase relative to the 1990-1995 time period.
• A precautionary approach proposed for lobster in LFA 34 utilizes reference points for the abundance of legal sizes (landings, commercial catch rate) and the abundance of legal and sublegal sizes combined (ITQ survey). These indicators are above their Upper Stock References (USR), indicating that the lobster stock in LFA 34 is in the healthy zone.
• Landings-based reference points are based on the median of lobster landings from 1985-2009. The Upper Stock Reference (USR) is 8,867 t. The 3-year running mean of landings is 21,147 t for the season ending 2011-12, putting LFA 34 lobster in the healthy zone, well above this USR.
• A proposed USR based on commercial CPUE is 80% of the median CPUE for the period 1998-99 to 2008-09. The current 3-year running mean (1.0 kg/trap haul) is well above the USR (0.62 kg/trap haul).
• A proposed fishery independent USR for legal and sublegal lobster abundance is 80% of the median catch rate in the ITQ survey for the period 1996-2009. The current 3-year running mean (71.9) is well above the USR (19.0 lobsters per tow).
• Environmental conditions for lobster production appear very favorable. High exploitation rates in the nearshore portion of LFA 34 have not inhibited the substantial increases in abundance in the last 10-12 years. Given that the environmental conditions remains favorable for lobster, the current levels of fishing effort do not appear to threaten the sustainability of lobster stocks in LFA 34.
• The percentage of reproduction contributed by larger females (>100 mm carapace length) is low and has likely declined relative to 20 years ago. Since it is uncertain how long favorable environmental conditions will continue, it is recommended that consideration be given to implement measures that increase egg production from larger sizes.

Ecosystem Considerations

• Based on previous patterns in the North Atlantic Oscillation, warmer than average water temperatures might be expected in LFA 34 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 main species caught as incidental catch in the fishery were those that can be retained for bait and sale: Jonah crab (male only), rock crab (male only) and various sculpin/sea raven species. Other major species included cusk, cod, hermit crabs and whelks. The total incidental catch and incidental catch of non-retainable species represent 15% and 4.2% of the total lobster landings respectively. Lobster discards (post-release survival known to be high) were estimated at 0.7 kg for each 1.0 kg of lobster landed or 14,634 t (2009-10). Undersize lobsters account for approximately 97% of the lobster discards.
• The area affected by lobster traps (fishery footprint) in any given year in LFA 34 as a whole is calculated to be less than 0.1% 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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