324 
Fishery Bulletin 99(2) 
away from or into the path of the net and to the extent that 
escape after entering the net depends on fish size. 
Perez-Comas ( 1996) used a sophisticated estimation pro- 
cedure but, conceptually, his vulnerability estimates were 
proportional to the length-specific ratios of catch rates in 
4V2-inch and 3-inch mesh (i.e. V L proportional to C L /K I , 
where C L and K L are catch rates with 4V2 and 3-inch gear). 
It is likely that catch rates for small fish in 3-inch mesh 
Table 7 
Average depth distributions, i.e. probabilities of depth given length or p(d \L), and CVs for shortspine thornyhead (sexes combined) 
between 36°00'N and 48°30'N lat and between 100 and 699 fm during October-December based on eight National Marine Fisheries 
Service bottom trawl surveys. Length groups and depth intervals defined as in Table 5. All eight surveys took 14-50 cm shortspine 
thornyhead. The symbol “ — “ means that the CV could not be calculated because the average depth distribution was zero. 
Depth intervals (fm) 
Fork length (cm) 
100-199 
200-299 
300-399 
400-499 
500-599 
600-699 
Depth distributions 
14 
0.3863 
0.6127 
0.0011 
0.0000 
0.0000 
0.0000 
16 
0.4221 
0.5752 
0.0027 
0.0000 
0.0000 
0.0000 
18 
0.4607 
0.5330 
0.0061 
0.0000 
0.0003 
0.0000 
20 
0.4969 
0.4816 
0.0185 
0.0006 
0.0024 
0.0000 
22 
0.4349 
0.5056 
0.0567 
0.0002 
0.0025 
0.0002 
24 
0.3920 
0.4944 
0.1079 
0.0028 
0.0025 
0.0006 
26 
0.3506 
0.4383 
0.1989 
0.0075 
0.0028 
0.0019 
28 
0.2780 
0.3779 
0.3271 
0.0117 
0.0032 
0.0021 
30 
0.2011 
0.3174 
0.4373 
0.0405 
0.0020 
0.0016 
32 
0.1718 
0.2694 
0.4564 
0.0824 
0.0130 
0.0070 
34 
0.1214 
0.2042 
0.4773 
0.1309 
0.0404 
0.0259 
36 
0.0826 
0.1874 
0.4169 
0.2025 
0.0662 
0.0445 
38 
0.0291 
0.1544 
0.3592 
0.2522 
0.1168 
0.0884 
40 
0.0190 
0.0797 
0.3410 
0.2175 
0.1868 
0.1560 
42 
0.0164 
0.0906 
0.1919 
0.1709 
0.2713 
0.2589 
44 
0.0039 
0.0518 
0.2034 
0.1698 
0.2908 
0.2804 
46 
0.0056 
0.0437 
0.1539 
0.1608 
0.3453 
0.2907 
48 
0.0080 
0.0440 
0.1429 
0.1342 
0.3108 
0.3602 
50 
0.0034 
0.0386 
0.1970 
0.1095 
0.3033 
0.3482 
CV 
14 
0.18 
0.11 
0.45 
— 
— 
— 
16 
0.14 
0.10 
0.44 
— 
— 
— 
18 
0.06 
0.05 
0.25 
— 
1.00 
- 
20 
0.08 
0.08 
0.26 
0.45 
0.91 
— 
22 
0.09 
0.07 
0.25 
0.66 
1.00 
1.00 
24 
0.10 
0.06 
0.21 
0.27 
0.76 
0.74 
26 
0.11 
0.09 
0.11 
0.15 
0.43 
0.65 
28 
0.10 
0.07 
0.03 
0.20 
0.75 
0.52 
30 
0.12 
0.07 
0.04 
0.22 
0.67 
0.69 
32 
0.15 
0.08 
0.05 
0.17 
0.31 
0.35 
34 
0.19 
0.14 
0.09 
0.14 
0.23 
0.59 
36 
0.18 
0.16 
0.10 
0.12 
0.34 
0.27 
38 
0.23 
0.21 
0.10 
0.13 
0.27 
0.25 
40 
0.43 
0.23 
0.12 
0.09 
0.11 
0.17 
42 
0.57 
0.25 
0.15 
0.17 
0.11 
0.17 
44 
0.69 
0.11 
0.12 
0.15 
0.11 
0.13 
46 
0.66 
0.28 
0.13 
0.16 
0.07 
0.12 
48 
0.41 
0.26 
0.18 
0.15 
0.11 
0.09 
50 
0.46 
0.26 
0.15 
0.12 
0.08 
0.13 
