Rodgveller et al: Evidence of hook competition in longline surveys 
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Table 1 
Preferred depth ranges (m) and average peak number of fish caught per 45 hooks (one skate of gear) for giant grenadier ( Alba - 
trossia pectoralis) (grenadier) and rockfish (shortraker [Seiostes borealis] and rougheye [Sefoasies aleutianus] rockfish) caught 
during the National Oceanic and Atmospheric Administration Alaska Fisheries Science Center annual longline surveys in the 
six management areas, 1979-2003. Preferred depth range is defined as the range in which the catch rate was at least 20% of the 
average peak catch rate (peak catch). 
Area 
Grenadier 
Rockfish 
Preferred depth (m) 
Peak catch 
Preferred depth (m) 
Peak catch 
Bering Sea 
350-1000 
5.3 
250-550 
1.0 
Aleutian Islands 
400-1000 
9.8 
250-500 
4.1 
Western Gulf 
400-1000 
14.4 
250-450 
2.8 
Central Gulf 
350-1000 
8.8 
300-500 
1.8 
West Yakutat 
350-1000 
5.5 
250-500 
4.2 
East Yakutat and Southeast 
550-1000 
3.5 
300-600 
4.8 
Table 2 
Average number of giant grenadier ( Albatrossia pectoralis) (grenadier) and rockfish (shortraker [Sebastes borealis ] and rough- 
eye [Sebastes aleutianus ] rockfish) caught per 45 hooks (one skate of gear) in their preferred depth range in each management 
area during the National Oceanic and Atmospheric Administration Alaska Fisheries Science Center annual longline surveys, 
1979-2003. Preferred depth range is defined as the range in which the catch rate was at least 20% of the average peak catch rate. 
The average sablefish (Anoplopoma fimbria) catches (SB catch) and the average number of baited hooks retrieved in the preferred 
depth ranges are also shown. Total catch is the sum of the average number of grenadier and sablefish caught per skate or the sum 
of the average number of sablefish and rockfish caught per skate. Catches and baited hooks are an average from 1995 through 
2003 because baited hooks were not counted before 1995. 
Grenadier Rockfish 
Area 
Grenadier 
catch 
SB 
catch 
Baited 
hooks 
Total 
catch 
Rockfish 
catch 
SB 
catch 
Baited 
hooks 
Total 
catch 
Bering Sea 
6.6 
3.9 
14.9 
10.5 
3.5 
8.6 
18.9 
12.1 
Aleutian Islands 
15.2 
5.0 
7.9 
20.2 
4.3 
3.0 
9.0 
7.3 
Western Gulf 
18.1 
6.4 
7.2 
24.5 
3.0 
9.2 
4.0 
12.2 
Central Gulf 
9.1 
10.5 
9.1 
19.6 
1.4 
8.4 
10.2 
9.8 
West Yakutat 
3.8 
10.6 
15.3 
14.4 
4.3 
5.5 
19.8 
9.8 
East Yakutat and Southeast 
3.1 
11.3 
17.9 
14.4 
3.3 
9.5 
16.4 
12.8 
fered substantially by species in each area. For example, 
in the East Yakutat and Southeast area the preferred 
rockfish depth range was 300-600 m and the peak 
catch rate was 4.8 fish/45 hooks, but in the Western 
Gulf area it was 250-450 m and the peak catch rate 
was 2.8 fish/45 hooks. The highest grenadier catch 
rates occurred in the Western Gulf area and were also 
relatively high in the Central Gulf and the Aleutian 
Islands areas. The highest rockfish catch rates were in 
the East Yakutat and Southeast area, West Yakutat, 
and the Aleutian Islands areas (Table 1). 
The number of baited hooks retrieved was similar at 
grenadier and rockfish preferred depths in each area; 
however, in the Aleutian Islands, Western Gulf, and 
Central Gulf areas, the total number of sablefish and 
rockfish caught at rockfish preferred depths was less 
than the number of sablefish and grenadier caught at 
grenadier preferred depths (Table 2). This finding indi- 
cates that there were many fish species other than sa- 
blefish and rockfish caught at rockfish preferred depths 
than at grenadier preferred depths. 
Longline correlations 
In 11 out of 12 cases, there were significant negative cor- 
relations between sablefish and grenadier and between 
sablefish and rockfish catch rates. The correlations 
between sablefish and grenadier catch rates were nega- 
tive in all six management areas. Correlations between 
sablefish and rockfish catch rates were negative in five of 
the six management areas (Table 3). Sample sizes varied 
between grenadier and rockfish in some areas because, 
