188 



Fishery Bulletin 102(1) 



WP Bigeye 



WP Distant 



Other fish 



Tuna 



Billfish - 



Sharks 



-0.2 



Great barracuda (0.94) 

 -Mahi mahi(1.15) 

 -«— Lancetfish (LN) (0.99) 

 Lancetfish (SN) (0.97) 



 e — Snake mackerel (1.06) 

 -Barracudas (0.96) 

 *- Opah (11) 

 ■9-Escolar (0.97) 



-9 Sickle pomfret (1 .2) 



-e-Pomfret (0.99) 

 - &— Escolars (1.07) 

 — ° — OHfish (1.12) 

 -^Skipjack (1 12) 

 ■«-Wahoo(1) 

 ?Yellowfin (1.61) 

 : e Albacore(1.45) 

 ! e Bigeye(1.18) 

 tShortbill spearfish (0.98) 

 -^Swordfish (1.04) 

 _e_ Stnped marlin (1.23) 

 — e— Sailfish (1.51) 

 — e — Black marlin (1.32) 

 -o-Blue marlin (1.14) 

 Hammerhead (0.87) 

 Grey reef shark (1 .49) 



1 Pelagic thresher shark (1.16) 



■® Bigeye thresher shark ( 1 .06) 

 -° Tiger shark (1) 



Other fish - 



Pomfret (1.43) 

 -Mahi mahi (1.45) 

 Lancetfish (LN) (1.02) 

 e— Great barracuda (0.84) 



— e Opah (1.24) 



e Barracudas (0.97) 



— e — — Sickle pomfret (2.13) 



Escolar (1.15) 



-Lancetfish (SN) (0 84) 

 Snake mackerel (3.56) 



-Ollfish (1.17) 



Tuna 



Billfish 



-e Sllvertip shark (1.17) 



■Q-Silky shark (115) 

 -6— Thresher sharks (0.88) 

 -s— Short finned mako (0.91 ) 

 "^Pelagic stingray (0.92) 



"Long finned mako (0 96) 



Sharks  



-° — Blacktip shark (1.3) 

 9 Blue shark (0.93) 

 -^Oceanic whitetip (0.91) 



e Whip stingray (1 .37) 



e Crocodile shark (1 .2) 



0.0 



I 



0.2 



Skipjack (0.91) 



Wahoo (0.97) 

 e-Yellowfin (2.02) 

 & Albacore(1.51) 

 - e "Bigeye(1.32) 

 ■Black marlin (0.89) 

 Striped marlin (1.19) 



— Shortbill spearfish (1.17) 

 -°— Sailfish (1 .04) 

 -° — Swordfish (0.89) 

 — s— Blue marlin (0 98) 

 Tiger shark (1.2) 

 — Crocodile shark (0.95) 

 Hammerhead (0 88) 



Whip stingray (1.01) 



Sllvertip shark (1 .46) 



■Blue shark (0.95) 



Blacktip shark (0.91) 



-e-Silky shark (1.5) 



e Pelagic stingray (1) 

 e Oceanic whitetip (1 .06) 



"Pelagic thresher shark (1.81) 



-Bigeye thresher shark (1.17) 

 "Short finned mako (0.91) 



-0.2 



0.0 



0.2 



Soak time coefficient 



Figure 4 (continued) 



For some species (e.g. seabirds, skipjack tuna, and mahi 

 mahi), soak time had a negative effect on catch rates that 

 was often statistically significant (Fig. 4). For skipjack 

 tuna in the Western Pacific distant fishery, for example. 

 catch rates decreased from 1.3 (CI ±0.2) per 1000 hooks 

 for a soak time of 5 hours to 1.0 (CI ±0.1) per 1000 hooks 

 (20 hours). Soak time had a small or statistically insignifi- 

 cant effect on catch rates for several species, such as yel- 

 lowfin tuna and shortbill spearfish. 



Fixed effects 



Exposure to dusk had a positive effect on the catch rates 

 for most species (Fig. 5). Dusk often had a negative effect 

 on the catch rates of billfish, such as striped marlin and 

 sailfish. For most species, however, the effect of dawn was 

 weaker, and it influenced the catch rates of fewer species. 

 Like soak time, timing made a substantial difference to 

 catch rates (Table 4). For a soak time of 12 hours in the 

 South Pacific yellowfin fishery, for example, longlinc seg- 



ments exposed to both dawn and dusk have a catch rate 

 of 2.0 (CI ±0.5) escolar per 1000 hooks. The catch rate is 

 0.8 (CI ±0.1) per 1000 hooks for segments that were not 

 exposed to dawn or dusk. 



The effects of timing on catch rates were most pro- 

 nounced in the South Pacific bluefin tuna fishery. The 

 fishery also showed the greatest range in soak time coef- 

 ficients, and the coefficients tended to be larger than those 

 of other fisheries (Fig. 4). 



Separately, the fixed effects often had statistically signifi- 

 cant relationships with catch rates of the seven species that 

 we investigated in detail. However, the interaction between 

 soak time and each fixed effect was less frequently signifi- 

 cant. Season was significant, for example, in none of the 

 six models that included a soak-time-season interaction 

 term. By comparison, season was significant in six of the 

 18 models that included season as a factor but not with a 

 soak-time-season interaction term. The effect of soak time 

 was not significant for southern bluefin tuna in any model 

 for the South Pacific bluefin tuna fishery. It was significant 



