Since the Miocene profound climatic changes have influenced the biology and ecology of species worldwide, such as their connectivity, genetic population structure, and biogeography. The goal herein is to evaluate the phylogeography of sailfish Istiophorus platypterus between the Atlantic, Indian, and Pacific oceans. Our results evidenced a high genetic diversity and three distinct populations among the ocean basins with limited gene flow among them. In addition, the species is characterized by two deep evolutionary lineages that diverged during the Miocene/Pliocene transition, one of them is circumtropical while the other is restricted to the Atlantic Ocean. These lineages evolved along the successive glacial-interglacial cycles from the Pleistocene and remained isolated from each other in glacial refugium until deglaciation. Assessments of sailfish suggest it may be subject to overfishing and the results herein imply the need to re-evaluate the current stock delimitations and management measures adopted by the Regional Fisheries Management Organizations, especially in the Atlantic and the Indo-Western Pacific oceans to effectively manage the species. In addition, this work highlights that both lineages should at least be treated as two distinct management units in the Atlantic Ocean until their taxonomic status is fully resolved, given their high genetic divergence.

This review documents the current state of knowledge and gaps therein, as determined through a survey of published research on relevant topics, regarding the potential impacts of offshore oil production platforms (OPP) on the biology of highly migratory fish species (HMS) which include tunas, swordfish, billfishes, and oceanic sharks. There is a limited amount of published research directly related to HMS and OPPs. This may be due to the relatively recent offshore expansion of the industry and of studies. Most studies have focused on structure-associated species such as rockfishes and snappers. Within the U.S. exclusive economic zone, the most probable areas of interaction between HMS and OPPs occur in the Gulf of Mexico. This report focuses primarily upon this region, while noting that HMS roam the majority of the world's oceans and may interact with petroleum infrastructure in many other locations. With such large stock boundaries it is unlikely that HMS interactions with OPPs will have a significant impact at the stock level, however, there could be impacts at local or regional levels.

Atlantic blue marlin fin spines were sampled from Venezuelan fleets during 2003-2008 for the purpose of estimating age and growth. Transverse sections of the second spine from the first anal fin were sampled from 1708 individuals. Of these, 1638 (95.9%) were readable (774 males, 744 females and 120 indeterminate). Males ranged in size from 130 to 254 cm LJFL, females from 126 to 370 cm LJFL. Samples were scored for visible growth annuli and age-corrected for early annuli lost as a result of increased spine core vascularization. Maximum age estimates based on visible annuli were 19.6 yrs for males and 31.3 yrs for females. After agecorrection the maximum age estimates were revised to 43.4 and 43.5 for males and females, respectively. The von Bertalanffy growth model and alternate variant models are presented for the observed individual LIFL at-age data, and three derived data sets: (1) mean observed LIFL at age, (2) all back-calculated LJFLs at each age, (3) mean back-calculated LJFL at each age for males, females, and combined sex.

In this study, the feeding habits and reproductive behavior of narrow-barred Spanish mackerel, Scomberomorus commerson , in the northern Persian Gulf during five months from October 2011 to December 2012 have been investigated. Specimens were purchased from the fishermen at several landing sites. Feeding and nutrition results showed that sardines are the major prey items of S. commerson . Secondary prey species included ponyfish, halfbeak and Indian mackerel fishes. Mature females (Stages III, IV) were mostly observed between April to July. By July, most of the studied fishes were in recovery or spent stages (Stages IV, V) indicating the end of the spawning season. The result of gonado-somatic index (GSI) study in 184 male and female specimens indicated the highest reproductive activity from April to July with the peak in July. The total sex ratio of 69 males and 115 females was 0.6:1 and it was not significantly different during study periods except autumn season. The minimum and maximum cavity index (CV) for both sexes were from 22.5% in December to 68.0% in October, respectively. Sardines were the most prevalent components of the diet of S. commerson . Based on the obtained results, it can be suggested that that banning of the Spanish mackerel catch in the June-July, which is the peak of spawning period, may help brood stocks. Banning the sardine catch may also benefit management of S. commerson in the Persian Gulf.

Pop-up satellite archival tags were deployed on 40 white marlin Kajika albida (synonym: Tetrapturus albidus) off the coasts of Maryland and North Carolina (United States), and the island nation of Aruba in the Caribbean. Useful data were available for analysing vertical and horizontal habitat use from 28 individuals. Time at liberty ranged from 10 to 181 d (mean 115, SD 53.3). Seasonal southerly fall migration routes were documented for fish released off the northeastern United States, while those released off Aruba remained in the Caribbean basin. Horizontal movements ranged from 228 to 8084 km (19-100 km d(-1)) based on light-level geolocation estimates using a sea surface temperature and bathymetry-corrected Kalman filter. Analyses included an evaluation of vertical movements using Delta T, the time spent at temperature relative to the uniform temperature surface layer. Movements included exploration of depths as great as 387 m and ambient temperatures as low as 7.8 degrees C. However, the greatest proportion of time was spent in the upper 20 m of the water column for both day (50.8%) and night (81.6%), and time spent in water colder than 7 degrees C below the uniform temperature surface layer was negligible. Overall, this group showed less variability in vertical movement, and less tolerance to colder temperatures compared with similar studies for blue marlin Makaira nigricans and sailfish Istiophorus platypterus. Values for Delta T are presented in tabular format to allow direct input into habitat standardization models used to estimate vertical distribution and population abundance. The large spatial dispersion and disparate tracks illustrated in the present study serve to underscore the complexity of white marlin behaviour and habitat use, and further emphasize the many challenges facing the management and conservation of this overexploited species.

Population dynamics parameters of Scomberomorus commerson in Bushehr area waters of Iran were analyzed between October 2011 and September 2012. Fork length frequencies were collected from the gill net commercial catch. Von Bertalanffy growth function was used to estimate growth parameters K and L∞. Instantaneous total mortality rate (Z), instantaneous natural mortality rate (M) and the instantaneous fishing mortality rate (F) were also calculated. Resource status was evaluated by comparing estimates of the fishing mortality rate with target (Fopt) and limit (Flimit) biological reference points. FiSAT program was used to assess growth and mortality parameters. Based on the growth curve analysis, growth parameters were: K=0.5year−1 and L∞=148cm. Instantaneous total mortality was Z=0.97year−1. The estimate of M=0.56year−1 and F=0.41year−1, resulting in an exploitation rate (F/Z) of E=0.42year−1. Target and limit biological reference points were: Fopt=0.28year−1 and Flimit=0.37year−1. Size at capture at probabilities of 0.25 (L25), 0.5 (L0.5) and 0.75 (L0.75), were 46.3 cm, 55 cm and 60.2 cm respectively. Longevity (Tmax) was calculated as 3/K equal to 6 years. The exploitation rate (E) did not indicate overfishing; however, Fopt and Flimit rates were lower than fishing mortality (F), suggesting that overexploitation occurred. Growth parameters in the present study showed that the gillnet fishery catches of S. commerson that are of ages 1 or 2, which may not have reached maturity. Gillnet mesh size can be a factor why the catch is composed of mostly small, immature fish. Therefore, changes in mesh size and net size should be considered.

For centuries, the mechanisms surrounding spatially complex animal migrations have intrigued scientists and the public. We present a new methodology using ocean heat content (OHC), a habitat metric that is normally a fundamental part of hurricane intensity forecasting, to estimate movements and migration of satellite-tagged marine fishes. Previous satellite-tagging research of fishes using archival depth, temperature and light data for geolocations have been too coarse to resolve detailed ocean habitat utilization. We combined tag data with OHC estimated from ocean circulation and transport models in an optimization framework that substantially improved geolocation accuracy over SST-based tracks. The OHC-based movement track provided the first quantitative evidence that many of the tagged highly migratory fishes displayed affinities for ocean fronts and eddies. The OHC method provides a new quantitative tool for studying dynamic use of ocean habitats, migration processes and responses to environmental changes by fishes, and further, improves ocean animal tracking and extends satellite-based animal tracking data for other potential physical, ecological, and fisheries applications.

Abstract Pop-up satellite archival tags (n = 31) were deployed on Yellowfin Tuna Thunnus albacares in the Gulf of Mexico for periods ranging from 14 to 95 d. Differences in diel vertical behavior were assessed by comparing time spent at temperature relative to the surface temperature (ΔT). Pooled samples revealed that 31% of darkness hours, 20% of twilight hours, and 12% of daylight hours were spent in the uniform-temperature surface layer (i.e., ΔT = 0). Total time spent above 100 m was less during daylight (90.0%) than during darkness (99.8%), suggesting greater exploration of deeper depths during daylight hours. Maximum depth visited ranged from 208 to 984 m, and minimum temperature visited ranged from 5.4°C to 11.8°C. Only a small proportion of total time was spent at temperatures colder than 8°C below the surface temperature. Horizontal excursions for the majority of individuals were less than 100 km from the point of release; however, three individuals moved distances of 411–1,124 km, suggesting that this species has the capability to move relatively long distances within the Gulf of Mexico. The ΔT values are provided in tabular format and serve as direct input variables for use in habitat standardization models.

This paper links 50 years of ongoing ocean scale deoxygenation trends in the tropical Atlantic Ocean to changes in vertical habitat use of large pelagic predators, and the Atlantic fisheries that exploited them. Climate induced warming in this large ocean area (Oxygen Minimum Zones, OMZs) has compressed the volumes of surface mixed layer habitat by about 1 m y-1 over the last 5 decades, concentrating predators, preferred prey, and influencing Atlantic-wide fishing effort patterns into progressively shallower surface zones. This phenomenon increases the catchability of these predators and may contribute to overly optimistic abundance estimates derived from surface fishing gears. Overall, deoxygenation is estimated to have caused a 15% reduction in suitable habitat for tropical pelagic tunas and billfishes in the tropical Atlantic during this time period. To demonstrate ocean scale changes in available habitat we use Hydrobase 3 database to compute decadal matrices of OMZ size (volume and surface area), as well as the reciprocal decline in surface mixed layer from 1955 through 2004. Further, we tracked fishing effort and catch inside and outside of the Atlantic OMZ for 9 major ICCAT assessment species to examine potential compression impacts. We found that during the last decade analyzed (1995-2004), longline fishing effort has coalesced on-top of the Atlantic OMZ, while hooks from outside the OMZ have decreased by about the same proportion. During the initial decade (1955-1964), 3 longline fleets deployed about 500,000 hooks, while by the last decade (1995-2004) longline effort had expanded to 94 fleets and almost 4.2 billion hooks. We determined that at least 7 out of 9 major ICCAT stock assessment species examined here are severely impacted by the OMZ expansion and resulting loss of available habitat. We also point out some significant ecosystem interactions between predators and preferred prey that appear to fuel predator assemblages.in progressively shallow OMZ areas, including some predators that are not sensitive to low ambient DO levels. As deoxygenation is expected to continue during the current cycle of climate change and global warming, and has been observed in other oceans as well, this suggests it may have broad-scale impacts on the sustainability of pelagic fisheries and their management. In order to maintain sustainable fisheries for tropical pelagic fishes, we feel its incumbent upon the assessment community to incorporate hypoxia-based habitat compression impacts for species of concern (identified here) into the assessment process. One potential approach might be accomplished during the Catch-Per-Unit-Effort standardization process, by scaling catchability coefficients (by species and gear) using the progressive decadal decline in available surface mixed layer habitat (in volume) presented here.

Pop-up satellite archival tags (n = 31) were deployed on Yellowfin Tuna Thunnus albacares in the Gulf of Mexico for periods ranging from 14 to 95 d. Differences in diel vertical behavior were assessed by comparing time spent at temperature relative to the surface temperature ( T). Pooled samples revealed that 31% of darkness hours, 20% of twilight hours, and 12% of daylight hours were spent in the uniform-temperature surface layer (i.e., T = 0). Total time spent above 100 m was less during daylight (90.0%) than during darkness (99.8%), suggesting greater exploration of deeper depths during daylight hours. Maximum depth visited ranged from 208 to 984 m, and minimum temperature visited ranged from 5.4◦C to 11.8◦C. Only a small proportion of total time was spent at temperatures colder than 8◦C below the surface temperature. Horizontal excursions for the majority of individuals were less than 100 km from the point of release; however, three individuals moved distances of 411–1,124 km, suggesting that this species has the capability to move relatively long distances within the Gulf of Mexico. The T values are provided in tabular format and serve as direct input variables for use in habitat standardization models. Subject editor: Michelle Heupel, James Cook University, Queensland, Australia *Corresponding author john.hoolihan@noaa.gov Received January 7, 2014; accepted June 8, 2014 211 D ow nl oa de d by [ 71 .4 6. 64 .2 22 ] at 0 8: 36 0 2 N ov em be r 20 14

The recent validation of the roundscale spearfish (Tetrapturus georgii) within the western North Atlantic has introduced new complexities in the management of the overfished white marlin (Kajikia albida) in this region due to historical and contemporary misidentification between the two morphologically similar species. Compounding the management challenge for white marlin, which is currently assessed as a single Atlantic-wide stock, is an unclear picture of the extent of the roundscale spearfish's overall Atlantic distribution. By using genetic tools (mitochondrial DNA ND4L-ND4 locus sequences) for species identification, we confirm that the roundscale spearfish has a much broader distribution than previously known, including the central North Atlantic and much of the western South Atlantic to at least 28 degrees 52'S. This much wider Atlantic distribution of the roundscale spearfish sympatric with its morphologically similar congeners, the white marlin and longbill spearfish (Tetrapturus pfluegeri), raises further management complexities: it increases the geographic scale for species misidentification in catch records that form the basis for stock assessments and uncertainty in currently accepted white marlin biological parameters. Additional vigilance in obtaining accurate species identification by improved fishery onboard observer training and incorporation of genetic tools is recommended for informing management of white marlin, longbill spearfish and roundscale spearfish throughout the Atlantic. (C) 2012 Elsevier B.V. All rights reserved.

SUMMARY Data from yellowfin tuna monitored with pop-up satellite archival tags in the Gulf of Mexico were evaluated for vertical habitat use. The proportions of time spent at temperature relative to the surface temperature (Delta T) were calculated and ranked by increasing depth for periods of darkness and daylight. Percentiles were tabulated for each of the observed frequency distributions. The percentiles of mean Delta T indicated that about 25% of darkness and 4% of daylight periods were spent at surface temperature (i.e. Delta T = 0). The tabulated percentiles represent major input variables used in habitat standardization models. RESUME

Vertical habitat use of sailfish (Istiophorus platypterus) was evaluated using pop-up satellite archival tag data from the eastern tropical Atlantic, western North Atlantic, and eastern tropical Pacific. Data included Argos transmitted depth, temperature, and light level frequency histograms binned at 1-8-h intervals, and four recovered pop-up satellite archival tags that provided high resolution archival data recorded at 30-s intervals. We tabulated the proportions of time spent within each degree of water temperature relative to the surface temperature (Delta T) and proportions of time at temperature, as these are major input variables for habitat standardization models used in stock assessment procedures. Frequency distributions were calculated for daylight, darkness, and twilight for each of the three regions and for all regions combined. Vertical habitat envelopes indicated greater use of deeper strata in the western North Atlantic, compared to the hypoxia-based habitat compressed regions of the eastern Atlantic and Pacific. However, there were no significant differences in Delta T distributions when comparing the three regions, affirming this metric for its application in habitat standardization models.

One of the impacts of ocean warming is a decrease in dissolved oxygen, with implications for valuable pelagic fish species. A study shows that the oxygenated upper ocean layer in the tropical northeast Atlantic thinned at a rate of around one metre per year between 1960 and 2010, and, by tracking individually tagged fish, demonstrates that this contraction in the oxygenated layer limited the movement of blue marlin. Climate model predictions1,2 and observations3,4 reveal regional declines in oceanic dissolved oxygen, which are probably influenced by global warming5. Studies indicate ongoing dissolved oxygen depletion and vertical expansion of the oxygen minimum zone (OMZ) in the tropical northeast Atlantic Ocean6,7. OMZ shoaling may restrict the usable habitat of billfishes and tunas to a narrow surface layer8,9. We report a decrease in the upper ocean layer exceeding 3.5 ml l−1 dissolved oxygen at a rate of ≤1 m yr−1 in the tropical northeast Atlantic (0–25° N, 12–30° W), amounting to an annual habitat loss of ∼5.95×1013 m3, or 15% for the period 1960–2010. Habitat compression and associated potential habitat loss was validated using electronic tagging data from 47 blue marlin. This phenomenon increases vulnerability to surface fishing gear for billfishes and tunas8,9, and may be associated with a 10–50% worldwide decline of pelagic predator diversity10. Further expansion of the Atlantic OMZ along with overfishing may threaten the sustainability of these valuable pelagic fisheries and marine ecosystems.