Hanselman et a\: Applications in adaptive cluster sampling of Gulf of Alaska rockfish 



505 



Table 1 



Data used to determine criterion values c for the 1999 adaptive cluster sampling (ACS) survey. Data from a 1998 ACS survey from 

 a different area is divided by the National Marine Fisheries Service triennial survey data and fishery data from the same area 

 to obtain gear efficiency values. The mean of these gear efficiencies are then multiplied against triennial and fishery data from 

 the new area to yield gear-calibrated CPUEs for the new area. Only numbers in bold were used in calculations, n = the number of 

 observations of that data set; 80% = the 80"^ percentile catch of that data set. 



Data source 



Year 



Mean CPUE (kg/km) 



80% 



ACS results from different area and year 



(divided by) 



CPUEs of corresponding previous area from 

 triennial and fishery data 



(equals) 

 Gear efficiency of the Unimak 



(multiplied by) 



Prior CPUE data from area for 

 1999 ACS survey 



(equals) 



Calibrated CPUE data for 

 1999 ACS survey 



Criterion value c 



1998 



284.94 



223.92 



57 



data we collected. In this comparison we used three new 

 sample sizes: 1) v,, the number of samples that could have 

 been taken in the same amount of time as that for a SRS 

 if sampling time for edge units was neghgible; 2) v^, in 

 which the edge units had taken the same amount of time 

 as non-edge units; and 3) v^, in which the average distance 

 between each tow type was used as effort instead of time 

 (with edge units included). 



survey data (1993, 1996) and fishery data (1996-98) from 

 the observer program for the same area. This gear coef- 

 ficient was then multiplied by the same data for the new 

 area to establish the expected catches. The data used and 

 the calculations are shown in Table 1. To implement alter- 

 native 3, we conducted 13 initial POP and 10 initial SR-RE 

 random tows across the entire area. Catches from these 

 initial tows gave us the following results for each criterion 

 alternative: 



Results Alternative 1 



Formulation of criterion alternatives 



A total of 164 tows were conducted for the ACS experiment. 

 Nearly all tows were made successfully; only a few excep- 

 tions were deemed untrawlable and moved to the nearest Alternative 2 

 trawlable bottom. We determined the POP criterion value 

 for alternatives 1 and 2 (see below) before the survey by 

 looking at the 1998 ACS results from a different geographic Alternative 3 

 area, as well as prior survey and fishery data in our study 

 area. We obtained the criterion value by calculating a gear 

 efficiency coefficient for the 1998 sui-vey by using NMFS 



For alternative 1, the mean of the 80"' per- 

 centile of the data from Table 1 is 641.69 

 kg/km. We rounded this downward to c = 

 540 kg/km ( 1000 kg/nmi) for ease of opera- 

 tion in the field (the design was originally 

 in kg/nmi units). 



The mean calibrated CPUE for the area 

 from Table 1 yielded a criterion value c of 

 220 kg/km (rounded). 

 In this alternative, the mean CPUEs from 

 the initial sample in 1999 yielded criterion 

 values of c = 250 kg/km for POP and c = 418 

 kg/km for SR-RE. 



