LENARZ and ADAMS: SOME STATISTICAL CONSIDERATIONS OF TRAWT SURVEYS 



Table 5. — Variances of means of catch (per L8 km towed) from hypothetical papulations of rockfish that were 

 constructed from 1977 survey data. Calculations are made under random, stratified random, and systematic 

 sampling schemes. Hypothetical populations are composed of two systematic samples with four or five members. 



Variance 



Population 



Members 



Area 



Depth interval (m) 



Random 



Stratified random 



Systematic 



Sebastes alutus 

 S alutus 

 S flavidus 

 S pinniger 

 S pinniger 

 S paucispinis 

 S paucispinis 

 S paucispinis 

 S paucispinis 

 S brevispinis 

 S elongatus 

 S elongatus 

 S. elongatus 

 S elongatus 

 S babcocki 

 S babcocki 

 S babcocki 

 S babcocki 

 S babcocki 

 S. crameri 

 S. crameri 

 S. crameri 

 S. crameri 

 S zacentrus 

 S diploproa 

 S diploproa 

 S diploproa 

 S- diploproa 

 S diploproa 

 S diploproa 

 S entomelas 

 S. entomelas 

 S entomelas 

 S entomelas 

 S entomelas 

 S aleutianus 

 S goodei 



goodei 

 . goodei 

 - goodei 

 '. jordani 

 . jordani 



fordani 

 S jordani 

 S saxicola 

 S saxicola 

 S saxicola 

 S saxicola 

 S saxicola 

 S- saxicola 

 S saxicola 

 S saxicola 

 S. rufus 

 S rufus 

 S rufus 

 S aurora 

 S. aurora 

 S aurora 

 S aurora 

 S melanostomus 

 S. melanostomus 



Average 



S 

 S. 

 S 

 S, 

 S 

 S 



4 

 4 

 4 

 4 

 4 

 4 

 4 

 5 

 5 

 4 

 4 

 4 

 5 

 4 

 4 

 4 

 4 

 4 

 4 

 4 

 5 

 4 

 4 

 4 

 4 

 4 

 5 

 4 

 4 

 4 

 4 

 4 

 4 

 5 

 4 

 4 

 4 

 4 

 4 

 5 

 4 

 4 

 4 

 5 

 4 

 4 

 4 

 4 

 5 

 5 

 4 

 4 

 4 

 4 

 5 

 4 

 5 

 4 

 4 

 4 

 5 



4 

 4 

 2 

 1 

 2 

 1 

 2 

 2 

 3 

 4 

 1 

 2 

 3 

 4 

 2 

 2 

 3 

 4 

 4 

 2 

 2 

 4 

 4 

 4 

 2 

 2 

 2 

 3 

 4 

 4 

 1 

 2 

 2 

 3 

 4 

 4 

 1 

 2 

 2 

 3 

 1 

 2 

 2 

 3 

 1 

 2 

 2 

 2 

 2 

 3 

 3 

 4 

 2 

 2 

 2 

 2 

 2 

 3 

 4 

 2 

 2 



183-273 



366-457 



91-182 



91-182 



91-182 



91-182 



91-182 



183-273 



91-182 



183-273 



91-182 



183-273 



91-182 



183-273 



183-273 



274-365 



366-457 



183-273 



366-457 



274-365 



366-457 



183-273 



366-457 



183-273 



183-273 



274-365 



366-457 



366-457 



183-273 



366-457 



91-182 



91-182 



183-273 



91-182 



183-273 



366-457 



91-182 



91-182 



183-273 



91-182 



91-182 



91-182 



183-273 



91-182 



91-182 



91-182 



183-273 



274-365 



366-457 



91-182 



366-457 



183-273 



183-273 



274-365 



366-457 



274-365 



366-457 



366-457 



366-457 



274-365 



366-457 



1,569 231 



15.517 



0.030 



2,807 



0,062 



3.210,176 



1 1 ,484 



6,045 



9,373 



0,546 



1,217 



0,015 



766 



15,775 



0,994 



1,666 



0,263 



30,055 



1,940 



10,827 



0.879 



475,931 



0,077 



3,770 



313,836 



953 833 



681,840 



53 007 



170,870 



0609 



155,903 



0,337 



0,763 



0,094 



0,751 



196 666 



39,745 



1.479,720 



104,217 



64 595 



155,874 



8,921,814 



1,814 



0,144 



3.677^92 



48652 



2,794,359 



0081 



0,026 



850,717 



1,035 



1,158 



2 562 



2,196 



128 



2,278 



5,613 



18,071 



169 



189 



5,542 



427,483 



1,576 140 



5 162 



0,034 



3,261 



072 



3.203,033 



13 142 



5,266 



10,639 



0,226 



1,436 



0,016 



0,656 



17,090 



1,102 



0,909 



0,197 



31,103 



0,551 



12414 



0372 



378,362 



107 



0,485 



243015 



869,422 



375,130 



25279 



178,211 



0,803 



156 260 



0,402 



0,275 



0,106 



0,849 



199 264 



38 155 



1,367,750 



127,159 



72,201 



163,576 



9,116,721 



2,179 



0,137 



335847 



55,079 



3.362,293 



0,069 



0,007 



916,415 



1,101 



1.285 



1.899 



2.447 



0.144 



2.502 



2,157 



12,091 



0045 



0,008 



4 153 



375349 



3.193.380 



3.195 



0.063 



6.439 



0.141 



2.889.063 



24.503 



3.534 



1.145 



0.336 



2.441 



0.026 



0.656 



1 1 .696 



0.130 



0.063 



0.002 



38.440 



1.000 



2.403 



0.372 



426423 



0.035 



0.281 



367,489 



1 .065.206 



53 290 



0,191 



122,324 



0,090 



158 760 



0.856 



0.723 



0.000 



0,250 



398,003 



35,106 



1,531 744 



335,989 



140 660 



85794 



7,983,423 



004 



137 



431 081 



106,864 



3,068,052 



0.069 



0.000 



388,878 



0,640 



2.789 



2.161 



3.331 



0.000 



0.902 



1.988 



14.440 



0.051 



0.004 



3.686 



375,586 



probably should not outweigh other factors such 

 as logistical constraints in the design of trawl 

 surveys. 



The sign test used to test the significance of 

 differences among sample designs assumed that 

 values for each species were independent. To 



examine this assumption we calculated correla- 

 tion coefficients for each species pair in each 

 combination of depth and area. Only samples 

 containing at least one occurrence of each species 

 of a pair were included. The average of the 

 absolute value of the correlation coefficient is 



665 



