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Abstract--Bluefin tuna (Thunnus thynnus) of the western Atlantic Ocean are often incidentally caught in the pelagic longline fishery that targets swordfish (Xiphias gladius) and yellowfin tuna (Thunnus albacares) in the [...]

Abstract--Procedures for sampling genomic DNA from live billfishes involve manual restraint and tissue excision that can be difficult to carry (mr and may produce stresses that affect fish survival. We [...]

Abstract--We examined 536 permit (Trachinotus falcatus, 65-916 mm FL) collected from the waters of Florida Keys and from the Tampa Bay area on Florida's Gulf coast to describe their growth [...]

Bycatch in pelagic longline fisheries is of substantial international concern, and the mitigation of bycatch in the Gulf of Mexico has been considered as an option to help restore lost biomass following the 2010 DEEPWATER HORIZON oil spill. The most effective bycatch mitigation measures operate upon a differential response between target and bycatch species, ideally maintaining target catch while minimizing bycatch. We investigated whether bycatch vs target catch rates varied between day and night sets for the United States pelagic longline fishery in the Gulf of Mexico by comparing the influence of diel time period and moon illumination on catch rates of 18 commonly caught species/species groups. A generalized linear model approach was used to account for operational and environmental covariates, including: year, season, water temperature, hook type, bait, and maximum hook depth. Time of day or moon phase was found to significantly alter catch rates for 88% of the taxa examined. Six taxa--swordfish (Xiphias gladius Linnaeus, 1758); tiger shark (Galeocerdo cuvier Peron and Lesueur, 1822); silky shark (Carcharhinus falciformis Miiller and Henle, 1839); oilfish (Ruvettus pretiosus Cocco, 1833); bigeye thresher shark (Alopias superciliosus Lowe, 1841); and escolar (Lepidocybium flavobrunneum Smith, 1843)--exhibited higher catch rates at night, while eight taxa--skipjack tuna (Katsuwonus pelamis Linnaeus, 1758); wahoo (Acanthocybium solandri Cuvier, 1832); white marlin [Kajikia albida (Poey, I860]; dolphinfish (Coryphaena sp.); yellowfin tuna (Thunnus albacares Bonnaterre, 1788); rays (Pteroplatytrygon violacea Bonaparte, 1832, Mobulidae sp.); lancetfish (Alepisaurus sp.), and blue marlin (Makaira nigricans Lacepede, 1802)--had higher daytime catch rates. These results reveal that shifts in effort between daytime and nighttime fishing (which are highly correlated with shifts between yellowfin tuna and swordfish targeting strategies) could have substantial, species-specific effects on bycatch rates. Whether driven by fishery conditions, market influences, or management measures, such temporal shifts in the timing of pelagic longline sets may have important implications for species-specific conservation goals and warrant further consideration. [ABSTRACT FROM AUTHOR]

The vertical movement patterns of eight Swordfish Xiphias gladius from 109- to 249-cm lower jaw fork length in the western North Atlantic were studied utilizing pop-up archival transmitting tags. Deployments ranged from 120 to 151 d. Swordfish demonstrated significant differences in depth and temperature distributions between daytime and nighttime periods. Individual Swordfish behavior was characterized by occupying surface waters of less than 100 m during the night and depths greater than 400 m during daytime hours, vertical movements between the surface and depth occurring during crepuscular hours. The maximum depth recorded was 1,448 m (one of the deepest recorded depths for the species). Daytime surfacing behavior was seen in all tagged Swordfish, a rare finding for Swordfish in tropical latitudes. A dominant diurnal period of 1 cycle/d was found from a power spectral density analysis of five of the tagged Swordfish, a novel method for determining periodicity in the behavior of tagged animals. Regression analysis indicated a significant positive relationship between depth and fraction of the moon illuminated, supporting anecdotal and vessel logbook information from local Swordfish fisheries indicating changes in depth in relation to lunar phase. [ABSTRACT FROM AUTHOR]

The article examines the impact of the rapid switch from J-hooks to circle hooks on pelagic fish hooking survival rates in the U.S. longline fishery. It mentions the use of a repeated measures logistic regression approach to test the hypothesis of no change in the survival of the fish. It notes the variation in hooking survival by fishing zone for white marlin and albacore. It also emphasizes the potential of using circle hooks to increase hooking survival.

The article examines the performance of non-offset and 10° offset circle hooks in commercial pelagic longline fishing (PLL) in the U.S. It mentions that the basis of their performance are catch rates, percent mortality, and the percentage of deep-hooked target and bycatch species. It emphasizes that the offset circle hook can reduce fishing efficiency compared to its non-offset type. It also notes higher mortality rate in blue marlin by using offset circle hooks than the non-offset one.

The article discusses a study on the parameters needed to calculate dolphinfish fecundity, particularly the potential annual fecundity of a female that lives through its first year. Regionally-specific maturity ogives was tested and the results in terms of effectiveness of current fishery regulations were considered. It indicates that C. hippurus has a coordinated suite of life history traits that make it resilient to moderate levels of fishing.

Swordfish are highly specialized top-level predators that have been challenging to study. In this paper, data from 31 pop-up satellite archival tags attached to swordfish from (i) the eastern Pacific, (ii) central Pacific, and (iii) western North Atlantic-Caribbean were analyzed. Common across locations was a pronounced diel vertical pattern with daytime hours spent primarily below the thermocline and nighttime hours spent in warmer waters, close to the surface. One exception to this pattern was periodic daytime basking events which were most common in cooler waters off California. Maximum daytime depths were significantly correlated with light penetration as measured by the diffuse attenuation coefficient at 490 nm. Temperature did not appear to influence daytime depths, and swordfish tolerated both extremely low temperatures (4°C) and rapid and dramatic temperature changes (>20°C). Temperature did appear to influence the nighttime depths in the Pacific where fish typically remained in the surface mixed layer. In contrast, in the warm tropical Atlantic this was not the case, and nighttime depths were much deeper. In all areas, nighttime depth increased around the full moon. Given the parallels between the vertical movement patterns of swordfish and those of the deep sound scattering layer we suggest that swordfish vertical distribution patterns, especially during daytime, are influenced largely by resource availability. At night, when swordfish are typically targeted by fisheries, both ambient light and temperature influence movements. Understanding vertical movement patterns of swordfish can help evaluate gear vulnerability, improve population assessments, and potentially reduce fisheries bycatch. [ABSTRACT FROM AUTHOR]

Oxygen minimum zones (OMZs) below near-surface optimums in the eastern tropical seas are among the largest contiguous areas of naturally occurring hypoxia in the world oceans, and are predicted to expand and shoal with global warming. In the eastern tropical Pacific (ETP), the surface mixed layer is defined by a shallow thermocline above a barrier of cold hypoxic water, where dissolved oxygen levels are ≤3.5 mL L−1. This thermocline (∼25-50 m) constitutes a lower hypoxic habitat boundary for high oxygen demand tropical pelagic billfish and tunas (i.e., habitat compression). To evaluate similar oceanographic conditions found in the eastern tropical Atlantic (ETA), we compared vertical habitat use of 32 sailfish ( Istiophorus platypterus) and 47 blue marlin ( Makaira nigricans) monitored with pop-up satellite archival tags in the ETA and western North Atlantic (WNA). Both species spent significantly greater proportions of their time in near-surface waters when inside the ETA than when in the WNA. We contend that the near-surface density of billfish and tunas increases as a consequence of the ETA OMZ, therefore increasing their vulnerability to overexploitation by surface gears. Because the ETA OMZ encompasses nearly all Atlantic equatorial waters, the potential impacts of overexploitation are a concern. Considering the obvious differences in catchability inside and outside the compression zones, it seems essential to standardize these catch rates separately to minimize inaccuracies in stock assessments for these species. This is especially true in light of global warming, which will likely exacerbate future compression impacts. [ABSTRACT FROM AUTHOR]

The article presents a study on the habitat utilization and movement patterns of the longbill spearfish Tetrapturus Pfluegeri Robins and de Sylva, found in the Eastern Tropical South Atlantic Ocean. The study used the pop-up satellite archival tags (PSATs) to monitor the movement and habitat utilization of two long bill species near Ascencion Island in the South Atlantic. The study reveals that minimum-maximum depth ranges and interpolated ambient isotherms were generated for each fish.

The article presents a study on the use of pop-up satellite archival tag (PSAT) technology in determining the vertical movement rate of billfishes. It notes that the investigators deployed and recovered intact PSAT's from two blue marlin, two white marlin and two sailfish. The rates of vertical movements was then determined from the recovered PSAT's. The result showed that the total number of descent events were smaller. The highest frequencies occurred within the 5-20 meter range. The investigators further revealed in their analysis that the higher movement rates of the billfish reflect burst swimming events.

The article examines young-of-year bonefish sampling data and specimens collected during the 1990s as part of juvenile fish monitoring conducted by the State of Florida Fish and Wildlife Commission. It is stated that beach seine sampling was conducted within 39 months between July 1994 and July 1998 at seven sites in the Florida Keys. The objectives of the study were to assess the seasonality of leptocephalous and juvenile catches with a temporally more extensive dataset, estimate juvenile bonefish growth rates from length-frequency data, and explore juvenile bonefish feeding habits via gut content analysis.

Management and conservation of many highly migratory fish species are based on population assessments that rely heavily on catch and effort data from the pelagic longline fishing industry. In 2003, we monitored hook time at depth for shallow-set commercial longlines (i.e., four hooks between surface buoys) targeting swordfish Xiphias gladius in the Windward Passage between Haiti and Cuba. We deployed temperature-depth recorders (TDRs) on about every 13th hook and attached them to branchlines just above the hook. Most TDRs were placed on branchlines that were predicted by catenary geometry to be at the deepest hook position between floats. Additional TDRs were also placed at the shallowest predicted hook position. We monitored 10 pelagic longline sets with a length (mean ± SE) of 44.9 ± 2.0 km. Time at depth for each TDR was binned into 5-m depth intervals. The expected bimodal distributions of hook time at depth were not observed; modes were 40 m for both the shallowest and deepest predicted hook positions. The majority of the hook depth distributions for shallow and deep hook positions achieved only 43% and 31%, respectively, of the depths predicted by catenary equations (i.e., <92 and <127 m). Individual TDRs were poor estimators of hook time at depth for other TDRs in the same catenary hook position during the same set (significant mean depth differences = 76.2-100%) and were even worse predictors of the depths fished during other sets (significant mean depth differences = 100%). Hook depth predictions based on catenary geometry drastically overestimated actual fishing depth in this study. These results indicate that the use of catenary geometry for estimating hook depth and subsequent vertical fishing effort is inadequate and fails to capture both within- and among-set variability, potentially resulting in biased stock assessments. [ABSTRACT FROM AUTHOR]

The article focuses on the use of appropriate methodologies and enzyme-linked immunosorbent assay for non-lethal sex identification in billfish tagging studies where gender is typically unknown. ELISA was developed to quantify vitellogenin-derived yolk proteins in muscle tissue biopsy samples from Atlantic blue marlin.

The article focuses on the transboundary movement of sailfish Istiophorus platypterus off the Pacific coast of Central America. The sailfish is one of the most important caught istiophods along the Pacific Coast of Central America. Tagging of the sailfish using pop-up satellite was made to determine their movement.

The article focuses on the spawning evidence of blue marlin (Makaira nigricans) in Bermuda waters and elevated mercury levels in large specimens. The gonads of 11 adult female blue marlin were evaluated histologically for reproductive status. 70 percent of the females caught in July were actively spawning.

Burnt tuna syndrome (BTS) is a term used to describe changes in raw tuna (sashimi) that is characterized by pale color, poor texture, and an “off” flavor. This reduction in tuna quality results in a much lower price for the fisher and significantly affects the profitability of tuna fisheries. In this study, we examine how at-sea factors, including the capture process, affect the quality of yellowfin tuna, Thunnus albacares caught in the northern Gulf of Mexico pelagic longline fishery. Hook timers were used to record the elapsed time between a tuna taking the hook and its eventual landing. The elapsed time on the hook, tuna length, and fish boarded alive were found to be positively correlated with the proportion of tuna grading #1, while fish boarded dead and days on ice were found to be negatively correlated. [ABSTRACT FROM AUTHOR]

Many predator species make regular excursions from near-surface waters to the twilight (200 to 1,000 m) and midnight (1,000 to 3,000 m) zones of the deep pelagic ocean. While the occurrence of significant vertical movements into the deep ocean has evolved independently across taxonomic groups, the functional role(s) and ecological significance of these movements remain poorly understood. Here, we integrate results from satellite tagging efforts with model predictions of deep prey layers in the North Atlantic Ocean to determine whether prey distributions are correlated with vertical habitat use across 12 species of predators. Using 3D movement data for 344 individuals who traversed nearly 1.5 million km of pelagic ocean in [Formula: see text]42,000 d, we found that nearly every tagged predator frequented the twilight zone and many made regular trips to the midnight zone. Using a predictive model, we found clear alignment of predator depth use with the expected location of deep pelagic prey for at least half of the predator species. We compared high-resolution predator data with shipboard acoustics and selected representative matches that highlight the opportunities and challenges in the analysis and synthesis of these data. While not all observed behavior was consistent with estimated prey availability at depth, our results suggest that deep pelagic biomass likely has high ecological value for a suite of commercially important predators in the open ocean. Careful consideration of the disruption to ecosystem services provided by pelagic food webs is needed before the potential costs and benefits of proceeding with extractive activities in the deep ocean can be evaluated.