'S*****! 



Figure 2. — The crab scrape used for blue crab fishing. 



rolled over the bottom. The handle was 1.5 m long. 

 The net was manually pushed along a 0.7 km 

 course, waist to chest deep, and parallel to the 

 shoreline. 



The crab scrape, used commercially for catching 

 shedding crabs, had a metal frame 96.5 cm wide 

 and 38.1 cm high. The lead bar on the crab scrape 

 has no teeth, a basic difference between it and a 

 dredge. A 3.8 cm twine net 182.9 cm long was fitted 

 to this frame. The crab scrape is towed from a 

 shallow-draft boat over grassy beds. The crab 

 scrape used in this study was modified by fitting it 

 with a 0.6 cm stretch mesh net to retain small (>3 

 mm) crabs. 



The otter trawl and crab scrape were towed 

 simultaneously beside each other from two small 

 outboard motorboats for 6 min at an engine speed 

 of 2,000 r/min. The push net was then pushed 

 parallel to the trawl and crab scrape tows over the 

 same distance but closer to shore. The depths for 

 the trawl and crab scrape tows ranged from 1 to 2 

 m whereas the push net sampled in depths of 

 0.6-1.1 m. Eighteen samples were collected for 

 each gear type. 



The sex and size class of crabs were determined 

 after each tow. Crab size was determined using 

 carapace width from one lateral spine tip to the 

 other. Crabs >60 mm wide were excluded from 

 consideration in this study because they were not 

 in the most recent year class. Three size classes 

 were used: class I measured 1 to 20.0 mm; class II, 

 20.1 to 40.0 mm; and class III, 40.1 to 60.0 mm. 



The mean number of crabs per square meter is 

 shown in Figure 3. It is apparent that the trawl is 

 comparatively ineffective for classes I and II. The 

 trawl and push net are about equally as effective 

 for class III although neither is as effective as the 

 modified crab scrape for classes I, II, or III. The 



TOTAL AREA FISHED 

 A1552Mi_)08 3 6M^ I2870m2 



to 



CO 



< 



u 



O 



LU 

 CO 



ID 



z 



24 



20 



16 



12 



8 



Trawl 



Push Net 



Crab Scrape 



I il ill I II III 



SIZE CLASS 



I II 



Figure 3. — Mean number of blue crabs per square meter for 

 each haul and total area fished by each gear. Size class (carapace 

 width) I = 1-20.0 mm, II = 20. 1-40.0 mm, and III = 40. 1-60.0 mm. 



crab scrape is the most effective gear for sampling 

 juvenile blue crabs. 



197 



