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The occurrence of tiger shark Galeocerdo cuvier in the Atlantic Ocean was assessed using at-sea observer data from multiple pelagic longline fisheries. Geographic positions of 2764 G. cuvier recorded between 1992 and 2013 and covering a wide area of the Atlantic Ocean were compared with the currently accepted distribution ranges of the species. Most records fell outside those ranges in both the Southern and Northern Hemispheres, which strongly suggests that the distribution range of G. cuvier in the open ocean is considerably larger than previously described [ABSTRACT FROM AUTHOR]

This paper presents an estimation of growth curves and spatiotemporal distributions of juvenile shortfin mako shark (Isurus oxyrinchus) in the western and central North Pacific Ocean using port sampling data collected from 2005 to 2013. The monthly length compositions show a clear transition of three modes in the size range of smaller than 150-cm precaudal length (PCL), which were believed to represent the growth of age-0 to age-2 classes, and they were then decomposed into age groups by fitting a Gaussian mixture distribution. Simulation data of lengths at monthly ages were generated from the mean and standard deviation of each distribution, and fit with a von Bertalanffy growth function. Parameters of the estimated growth curves for males and females were 274.4 and 239.4 cm PCL for the asymptotic length and 0.19 and 0.25 year-1 for the growth coefficient indicating apparently faster growth than previously reported. Generalised linear models were applied to age-0 to explore the seasonal changes of PCL by area. They were born during late autumn and winter off the coast of north-eastern Japan, an area known to have relatively high productivity compared with other pelagic areas, and gradually expanded their habitat eastward and northward with the seasons as they grew. Growth and spatiotemporal distribution of juvenile shortfin mako provide valuable information on their potential productivity, mechanisms of recruitment and movement. The aims of this study were to estimate the growth and to explore the distribution. The shortfin mako growth was faster than previously reported - sharks were born during autumn and winter off the coast of north-eastern Japan, and gradually expanded their habitat eastward and northward. [ABSTRACT FROM AUTHOR]

Sexual differences in the distribution pattern, sex ratio and the gonad condition of four istiophorid billfishes were investigated in three different tropical areas of the eastern North Pacific Ocean from September to November 2004. Sex ratios of striped marlin Kajikia audax were equal (female : male = 11 : 11) in the open-ocean area (16-18°N, 118-134°W), biased to males (32 : 62) in the near-continental area (13-16°N, 103-107°W), and biased to females (19 : 6) in the near-equatorial area (5°N, 104-120°W). Sex ratios of sailfish Istiophorus platypterus in the near-continental area and shortbill spearfish Tetrapturus angustirostris in the open-ocean area were not biased from 1 : 1 (43 : 36, 11 : 13), and that of blue marlin Makaira nigricans in the near-equatorial area was biased to females (14 : 1). Reproductively active females were found for striped marlin, sailfish and shortbill spearfish. Striped marlin showed a specific spawning area (the near-continental area), and sexual dimorphism in its temporal distribution pattern, which was presumably related to reproduction. On the other hand, the limited distribution with evidence from spawning of sailfish and shortbill spearfish imply that these species complete their life history within limited areas. [ABSTRACT FROM AUTHOR]

Species composition and food habits of four istiophorid billfishes were investigated and compared in three different tropical areas of the eastern North Pacific Ocean by longline operations from September to November 2004. Sailfish Istiophorus platypterus, shortbill spearfish Tetrapturus angustirostris and blue marlin Makaira nigricans had specific habitat preferences and mainly occurred in the near-continent area (13-16° N; 103-107° W), the open-ocean area (16-18° N; 118-134° W) and the near-equator area (5° N; 104-120° W). Small (<140 cm in lower jaw-fork length) striped marlin Kajikia audax mainly occurred in the near-continent area; however, large (≥140 cm) individuals occurred throughout all three areas. Prey compositions of large K. audax in the three areas were different from one other reflecting the prey availability in each area. In the open-ocean area, molid fishes were dominant in mass for both large K. audax (49%) and T. angustirostris (73%), and large K. audax also fed on ostraciid (33%) and scombrid fishes (15%). In the near-continent area, tetraodontid fishes were dominant for large and small I. platypterus (54, 57%), and both large and small K. audax also fed on tetraodontid fishes (3, 12%). Large K. audax in this area fed mainly on scombrid fishes (86%). These results indicate that large K. audax show overlaps but little segregations of its prey with other billfishes. In the near-equator area, stomach contents of large K. audax and M. nigricans were few and billfish prey items were thought to be scarce. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the number of slender mola or Ranzania laevis found in the stomachs of blue marlins or Makaira nigricans at Okinawa Island in Southern Japan. It states that the study examines 10 blue marlins in which the slender mola found in the stomachs of the marlins were measured for mantle length, standard length, and pre-clavus length. It concludes that the high frequency of slender mola in blue marlines is due to the spawning season of slender mola in Hawaii.