Science Advisory Report 2009/033

Assessment of Lobster in
Lobster Fishing Area 41 (4X + 5Zc)

Summary

• The abundance indicators suggest that lobster abundance in LFA 41 has been either stable without trend or has trended higher since 1999. The current catch rate model indicates catch rates have trended inconsistently or increased in different areas of LFA 41. The DFO bottom trawl survey shows increased mean number of lobster per tow, but the time series is short and further development of this data set is recommended.
• Total trap hauls (fishing pressure indicator) in 2007 returned to pre-Jonah crab fishery levels of 225,000, down from the peak of 593,000 in 1998-99 season presumably because of reduced fishing for Jonah crab.
• Exploitation rate for lobster in LFA 41 has not been directly estimated but is inferred to be low. The size structure has remained stable except for apparent recent decreases in sizes in the Crowell Basin area. The results suggest a low exploitation level similar to that estimated in the USA 2006 lobster assessment of Georges Bank (Fishing Mortality, F, of 0.3).
• The sex ratio is skewed towards more females as conservation rules protecting berried females result in lower fishing mortality on females. The decrease in the proportion of males occurred during the first 10 years of the fishery, with the largest change on Georges Bank, and has since remained stable.
• Landings in adjacent fisheries have increased significantly in the last 10 years, indicating additional pressure on the lobster resources in these areas.
• Indicators of lobster recruitment in LFA 41 are not currently available. Standard size-based methods are not applicable in LFA 41 since the fishery is conducted primarily in deeper areas where recruitment is not expected to occur. The US National Marine Fisheries Service has used their trawl survey to track recruit abundance and, as the time series develops, a similar approach will be applied using Canadian data. The 2006 USA lobster assessment concluded stable abundance for the Georges Bank stock and much of the Gulf of Maine stock with very little variability in abundance in recruit and post-recruit size classes over the time series (1982-2004) on Georges Bank.
• A high percentage of females in the catch of the LFA 41 fishery catch are larger than the 50% size of maturity (Georges Bank 98%, Southeast Browns 96%, SWB 77%, Georges Basin 91%, Crowell Basin 63%); and data from length compositions indicate many have spawned more than once. Four of these areas show no trend in this proportion over time; Crowell Basin has shown a decrease in the proportion of mature females.
• Bycatch in the LFA 41 lobster fishery is recorded on observed trips. Species that occur most frequently as bycatch are Jonah crab, cusk, hake (red and white), cod, rock crab and redfish. Other than Jonah crab, all animals are required to be released. High survival is expected for invertebrates, but survival may be lower for some fish species.
• The effect of fishing on bottom habitat has not been evaluated but, relative to other bottom contact gear types, is expected to be low due to the small size of the gear footprint and relatively low density of traps in this large fishing area.

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