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The use of circle hooks (16/0) instead of J hooks (size 2) on pelagic longline gear, reduced the incidental capture of immature loggerhead sea turtles (Caretta caretta) and did not affect the catch rates or fish size of the target species (primarily swordfish (Xiphias gladius) and tuna (Thunnus spp.)). There was also a significant difference in hook location between the two hooks, with more J hooks being swallowed.

The biting behavior of the loggerhead sea turtle, Caretta caretta, a common bycatch species in longline fisheries, was studied on 30 wild specimens held temporarily at rescue centers. Chemicals from squid baits elicited significantly more biting behavior than those from mackerel baits. 

The use of blue-dyed bait (both squid and fish) as a means to reduce seabird interactions with pelagic longline fishing gear was tested during Japanese longline fishery survey cruises off South Africa in the Southern Ocean.  The incidental catch of seabirds was lower for both blue-dyed squid and fish baits compared to non-dyed baits. The catch per unit effort (CPUE) of albatrosses decreased when blue-dyed squid and fish baits were used during all years of the study. The CPUE of petrels was lower during two years when blue-dyed bait was used.  The CPUE of the target southern bluefin tuna (Thunnus maccoyii) was also reduced during all three years when blue-dyed bait was used, except in 2003 when blue-dyed fish bait was used.  A second experiment testing the use of tori lines and blue-dyed bait (both types) resulted in no interactions with seabirds.

The use of blue-dyed bait (both squid and fish) as a means to reduce seabird interactions with pelagic longline fishing gear was tested during Japanese longline fishery survey cruises off South Africa in the Southern Ocean.  The incidental catch of seabirds was lower for both blue-dyed squid and fish baits compared to non-dyed baits. The catch per unit effort (CPUE) of albatrosses decreased when blue-dyed squid and fish baits were used during all years of the study. The CPUE of petrels was lower during two years when blue-dyed bait was used.  The CPUE of the target southern bluefin tuna (Thunnus maccoyii) was also reduced during all three years when blue-dyed bait was used, except in 2003 when blue-dyed fish bait was used.  A second experiment testing the use of tori lines and blue-dyed bait (both types) resulted in no interactions with seabirds.

From 2001 to 2006, 71 pop-up satellite archival tags (PSATs) were deployed on five species of pelagic shark (blue shark [Prionace glauca]; shortfin mako [Isurus oxyrinchus]; silky shark [Carcharhinus falciformis]; oceanic whitetip shark [C. longimanus]; and bigeye thresher [Alopias superciliosus]) in the central Pacific Ocean to determine species-specific movement patterns and survival rates after release from longline fishing gear. Only a single post-release mortality could be unequivocally documented: a male blue shark, which succumbed seven days after release. Meta-analysis of published reports and the current study (n=78 reporting PSATs) indicated that the summary effect of post-release mortality for blue sharks was 15% (95% CI, 8.5–25.1%) and suggested that catch-and-release in longline fisheries can be a viable management tool to protect parental biomass in shark populations. Pelagic sharks displayed species-specific depth and temperature ranges, although with significant individual temporal and spatial variability in vertical movement patterns, which were also punctuated by stochastic events (e.g., El Niño-Southern Oscillation). Pelagic species can be separated into three broad groups based on daytime temperature preferences by using the unweighted pair-group method with arithmetic averaging clustering on a Kolmogorov-Smirnov Dmax distance matrix: 1) epipelagic species (silky and oceanic whitetip sharks), which spent >95% of their time at temperatures within 2°C of sea surface temperature; 2) mesopelagic-I species (blue sharks and shortfin makos, which spent 95% of their time at temperatures from 9.7° to 26.9°C and from 9.4° to 25.0°C, respectively; and 3) mesopelagic-II species (bigeye threshers), which spent 95% of their time at temperatures from 6.7° to 21.2°C. Distinct thermal niche partitioning based on body size and latitude was also evident within epipelagic species.

Comment in Marine Ecology Progress Series: Campana et al. (2009; Mar Ecol Prog Ser 387:241–253) explored the survival of blue sharks (Prionace glauca) captured and released from the North Atlantic commercial longline fishery. The authors of this comment think that Campana et al.'s comments and comparisons do not accurately reflect a previous survival study of blue sharks in Hawaii (Moyes et al. 2006; Trans Am Fish Soc 135:1389–1397). The differences in mortality between the studies, ~5% in the Hawaii-based fishery and ~35% in the North Atlantic fishery, were suggested to be due to failure of Moyes et al. (2006) to accurately reflect commercial fishing conditions. Careful examination of the data, however, suggests that the mortality depends on fishery specific features—hook type, soak time and handling of the bycatch during release—rather than the respective tagging protocols. Survival studies based on pop-up satellite archival tags (PSATs) are cost-prohibitive; alternative (e.g. biochemical) approaches to estimate stress and morbidity are needed to supplant PSAT studies and to increase sample sizes. Standardization of fishing methods and sampling protocol is needed for future survival studies, to reduce experimental bias and improve the cost: benefit relationship.

Incidental captures of the franciscana dolphin (Pontoporia blainvillei) by artesinal coastal fishermen of Buenos Aires, Argentina were investigated. Data was collected on carcasses of 54 incidentally captured dolphins between 2003 and 2009. Results indicated that the majority (69%) were animals four years old and younger, 74% of entangled animals were sexually immature and 85% were physically immature. Entanglements were not associated with any disease or physiological disorder. No bycatch mitigation techniques were tested for this paper.

Sharks, turtles, billfish, and marine mammals are frequently caught accidentally in commercial fisheries. Although conservationists and fisheries managers encourage the release of these nontarget species, the long-term outcome of released animals is uncertain. Using blue sharks (Prionace glauca), we developed a model to predict the long-term survival of released animals based on analysis of small blood samples. About 5% of the sharks were landed in obviously poor condition (lethargic and unresponsive to handling); these moribund sharks were sampled and euthanized. A subset of the remaining sharks was sampled and tagged with pop-up satellite archival tags (PSATs). Each of the PSATs that reported data (11 tags) showed that the sharks roamed at sea for at least 3 weeks post-release. Five variables differentiated moribund sharks from survivors: plasma Mg2þ (moribund, 1.57 6 0.08 mM; survivor, 0.98 6 0.05 mM; P , 0.00001), plasma lactate (moribund, 27.7 6 4.1 mM; survivor, 5.80 6 2.96 mM; P , 0.001), erythrocyte heat shock protein 70 (Hsp70) mRNA (relative levels: moribund, 3.96 6 0.53; survivor, 1.00 6 0.29; P , 0.005), plasma Ca2þ (moribund, 3.70 6 0.14 mM; survivor, 3.13 6 0.11; P , 0.005), and plasma Kþ (moribund, 7.01 6 0.66 mM; survivor, 5.12 6 0.44 mM; P , 0.05). These analyses were used to develop logistic regression models that could ‘‘predict’’ the long-term survival of captured sharks, including a larger group of sharks that we sampled but did not tag. The best logistic model, which incorporated Mg2þ and lactate, successfully categorized 95% of fish of known outcome (19 of 20). These analyses suggest that sharks landed in an apparently healthy condition are likely to survive long term if released (95% survival based on biochemical analyses; 100% based on PSATs). 

Several seabird bycatch mitigation techniques were tested aboard distant water tuna fisheries in the South African EEZ.  Two types of bird scaring designs, light lines with short streams and  hybrid lines with a mix of streamer lengths were compared to unweighted branch lines. In addition, unweighted to weighted branch lines, as well as  night versus day setting with a combination of bird scaring lines were tested for their effects on seabird avoidance and targeted fish catch rates.  A total of twenty seven seabird species were observed, but white-chinned petrels (Procellaria aequinoctialis) were the most common seabird observed and had the highest seabird mortality rate in the study. Albatross (black-browed (Thalassarche melanophris), yellow-nosed (Thalassarche chlororhynchos) and shy (Thalassarche cauta)) also suffered high mortality rates while stealing bait from the petrels.  Other common surface foraging species included cape petrels (Daption capense). Hybrid lines did appear to reduce sea bird attacks, but the results are not conclusive because the birds could still attack the line at points not protected by the bird scaring lines.  Sets made at night caught far fewer seabirds (0.439 birds/1000 hooks vs. 2 birds/1000 hooks) and catch rates were 18 times higher on the unweighted compared to weighted branch lines (1.07 birds/1000 hooks and 0.06 birds/1000 hooks respectively). The weighted and unweighted branch lines did not affect targeted fish catch rates.

Key pelagic shark species are caught in the North Pacific by Japanese longline fisheries as bycatch. These species include blue shark (Prionace glauca) and shortfin mako (Isurus oxyrinchus). In this study, fishery-independent data was leveraged by utilizing a generalized linear mixed model to standardize these data and identify changes in spatio-temporal catch rates. For blue shark, catch was recorded from temperate waters of the western and central North Pacific. Shortfin mako were distributed in coastal and offshore waters along the Kuroshio-Oyashio transition zone and the Mixed Water Region. The yearly changes in the catch per unit effort (CPUE) of blue shark illustrated a downward trend until 2008 and an upward trend thereafter, whereas those of shortfin mako exhibited a flat trend with large fluctuations from 1994 to 2008, and a down-and-up trend thereafter. Successfully leveraging this otherwise unreliable dataset suggest it can now be utilized to improve the stock assessment and management of these shark species.