Research Document - 2001/079

Pre-fishery abundance and distribution of American lobster in western Northumberland Strait, 1999 and 2000

By Hanson, J.M.

Abstract

Standardized catch-per tow was calculated for pre-commercial and commercial sizes of American lobster (Homarus americanus) just prior to the late summer-early autumn lobster fishery in 1999 and 2000. The 1999 survey used a 4.2-m beam trawl (45-mm poly-MK2 shrimp netting, 12-mm stretched mesh braided nylon liner) towed at a speed of 5.6 km/h for 10 minutes at each station. There were 126 successful tows. The survey area (> 5-m depths) represented about 5,600 km2 of potential habitat; of this, a 700 km2 area was too rough to fish with the beam trawl. The 2000 survey used a No. 286 otter trawl equipped with rockhopper footgear. The 2000 survey covered all of Lobster Fishing Area (LFA) 25 and 1,500 km2 of LFA 26A (142 successful sets). Lobster was not evenly distributed by depth or by area in either year. Over 95% of the lobster were caught in water < 25 m deep, which was consistent with the surveys occurring during the molting season. In both years, most of the animals caught in the east were >81 mm CL (market size) while relatively few of these large animals were caught in the most westerly area. Very small (pre-commercial size) lobsters were most abundant along the New Brunswick shoreline, suggesting that distinct nursery areas do exist in the LFA. The 1999 survey biomass in LFA 25 (commercial sizes) was about 1,000 t compared to 3,800 t landed during the fishery. The 2000 survey biomass was about 3,800 t compared to estimated landings of 3,400 t. The otter trawl clearly was more effective than the beam trawl for catching lobster. In addition, the survey was conducted in an area inaccessible to the annual September assessment surveys for demersal fishes and may yield a valuable estimate of the density of winter flounder in this area (LFA 25).

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