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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 postrelease 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 postrelease 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.

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 postrelease 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 postrelease 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.

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. We think that their 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.

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 postrelease. 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).

Shrimp is one of the most valuable fishery resources of Venezuela, with landings about 12 400 t (2007) and worth more than US $35 million. Fishing is carried out along the coast; the industrial trawl fleet used to operate at depths between 10 and 120 m, while fishing with artisanal gears is done close to shore, in coastal lagoons, gulfs and in Lake Maracaibo at depths from 1 to 40 m. The latter represent 84% of landings, mainly from Lake Maracaibo. While only the shrimp is sold by the artisanal fleet, the industrial fleet also sells some fish species, crabs and mollusks. It is been estimated that discards can reach 100 thousand t per year. Due to differences in the spatial distribution of the shrimp and the bycatch, as well as the behavior of the shrimp, more selective fishing systems towards the shrimp were designed, or technological changes in nets were used to restrict the capture of bycatch or facilitate its release after entering the net. In this paper, discards were characterized and various technological changes were tested in nets of common use in shrimp fisheries of Venezuela. The tested systems were: the double lower rope in the industrial trawl; the "fish eye" in the artisanal trawl and the Suripera net. Discards in the industrial fleet were reduced very significantly with the double lower rope, between 26 and 32%, while the commercial catch was maintained or increased. In the artisanal fleet, fish eye allowed reductions of discards between 38 and 54%, without significantly affecting shrimp capture. The Suripera net is very selective, capturing 98% of shrimp, compared to the traditional seine which has 28% efficiency. The possibility of reducing discards is high in industrial or artisanal shrimp fleets operating with trawls, but the seine used by the artisanal fleet operating in Lake Maracaibo may have to be replaced with another more selective gear towards shrimp, like the bottom tangling net. These are examples of how to implement Article 8 of the FAO Code of Conduct for Responsible Fishing (selectivity of the arts in fishing operations) in fisheries of high environmental impact.

Seabird bycatch in the tuna and billfish longline fishery in South African waters has had one of the highest seabird bycatch rates in the world. Research was carried out aboard two Japanese longline vessels in the South African EEZ in 2010. Half of the branch lines on each vessel were weighted using the double-weight configuration, which consists of a weighted section that was inserted into the monofilament section of a branch line 2m above the hook. Each vessel also deployed two "hybrid" bird-scaring lines during every set. the lines had a mix of long and short streamers. The rate of bird attacks on baited hooks was four times higher on unweighted lines. Mortality of seabirds on weighted branchlines combined with bird-scaring lines was six times less than on unweighted lines. The rate of seabird bycatch was more than 13 times higher during the day than at night. The authors conclude that the combination of two bird-scaring lines, weighted branch lines, and night setting qualify as best practices for seabird bycatch mitigation for fleets targeting tuna and related species in the South African EEZ. 

Neodymium-iron-boron (Nd2Fe14B) permanent magnets were used to test behavioral responses in spotted catsharks (Scyliorhinus canicula) and thornback skates (Raja clavata). Both species significantly avoided the Nd2Fe14B magnets more often in comparison to the control and procedural control and they fed significantly more from the control an procedural control in comparison to the magnets. The study also demonstrated a correlation between avoidance speed and distance with water temperature. 

An analysis of the performance of circle hooks in comparison to J-style and tuna hooks on the hooking rates of target and non-target species, specifically sea turtles, in the artisanal surface longline fisheries of Ecuador, Panama, and Costa Rica was performed. The target fisheries were mahi-mahi and a combination of tunas, billfishes, and sharks (TBS). In the TBS fishery, tuna hooks were compared to 16/0 circle hooks from Ecuador and Panama and 18/0 circle hooks from Costa Rica. For the mahi-mahi fishery, 14/0 and 15/0 circle hooks in Ecuador and 16/0 circle hooks in Costa Rica were compared to traditional J-style hooks. Circle hooks reduced sea turtle hooking rates in most of the comparisons. Hooking rates for target and non-target species were not consistent.

Two porpoises were subjected to 3 different underwater sounds (standard Dukane alarm, random Dukane alarm, and a "bird alarm") in a enclosed floating pen. Their behavior during a 15 min test period was compared to behavior during a baseline 15 min period before the test and a recovery period after the test. All alarms resulted in increases in both the distance of the animals' surfacings from the alarms and their respiration rates. The standard Dukane alarm and the bird alarm were more effective than the random alarm in inducing animals to swim away from the source. 

Two captive harbor porpoises were exposed to three sound types (frequency from 100 kHz to 140 kHz, 200 ms long, and presented once per 4 s). Each session consisted of a 10 min period persound, a 5 min period of sound, and a 10 min period after the sound. Behavior was recorded on video and with dataloggers. Animals reacted most to the intial presentations of sound, but the reactinos diminished rapidly in repeated sessions.