Large pelagic fishes are often broadly distributed and capable of long-distance movements. These factors can promote gene flow that makes it difficult to disentangle intra- vs. inter-specific levels of genetic differentiation. Here, we assess the relationship of two istiophorid billfishes, white marlin (Kajikia albida) and striped marlin (K. audax), presently considered sister species inhabiting separate ocean basins. Previous studies report levels of genetic differentiation between these species that are smaller than those observed among populations of other istiophorid species. To determine whether white marlin and striped marlin comprise separate species or populations of a single globally distributed species, we surveyed 2520 single nucleotide polymorphisms (SNPs) in 62 white marlin and 242 striped marlin across the Atlantic, Pacific, and Indian oceans. Multivariate analyses resolved white marlin and striped marlin as distinct groups, and a species tree composed of separate lineages was strongly supported over a single lineage tree. Genetic differentiation between white marlin and striped marlin (F-ST = 0.5384) was also substantially larger than between populations of striped marlin (F-ST = 0.0192-0.0840), and we identified SNPs that allow unambiguous species identification. Our findings indicate that white marlin and striped marlin comprise separate species, which we estimate diverged at approximately 2.38 Mya.

Electronic waste is a dominant global issue with over 50 million tons generated annually. Still, as an amalgamation of precious and rare raw materials, electronic waste is a considerable economic resource with the most valuable components located on the printed circuit boards. Gold is widely used in electronics in numerous applications, although principally for contact points and external connectors. The recovery of gold, due to its high value, is one of the main motivations for recycling e-waste. Although pyrometallurgy and hydrometallurgy processing are still the preferred modes of recovery for gold, the use of high-energy consuming pyro-methods, and the use of gold cyanidation that uses harmful lixiviants are increasingly discouraged. Thiourea has received attention as an alternative lixiviant for gold leaching due to its fast reaction kinetics and less harmful nature. This review aims to provide an up-to-date evaluation of thiourea-gold leaching studies from electronic waste, with emphasis on the recent progression from the classic chemical method to a more sustainable hybrid bioleaching-based system, while its challenges are highlighted. The complementary methods applied for gold retrieval from the pregnant solution are also described with a focus on sustainable methods that have the potential to provide a closed-loop system, the key objective for material recovery in a circular economy.

The objective of this research was to electrocodeposit turmeric particles into copper matrices, and assess the influence of turmeric on the microstructure and properties of those deposits. The incorporation of turmeric had a significant effect on both the grain structure and properties of the copper deposits, with turmeric particles of a Z-average size of 289 +/- 30 and 278 +/- 15 nm having a greater influence on grain refinement than particles of 134 +/- 37 nm, even at much lower deposit particle contents. The incorporated turmeric increased both the hardness and water contact angle of the deposits; however, a reduction in resistance to salt spray corrosion was also observed.

Aim Climate change has influenced the distribution and phenology of marine species, globally. However, knowledge of the impacts of climate change is lacking for many species that support valuable recreational fisheries. Cobia (Rachycentron canadum) are the target of an important recreational fishery along the U.S. east coast that is currently the subject of a management controversy regarding allocation and stock structure. Further, the current and probable future distributions of this migratory species are unclear, further complicating decision-making. The objectives of this study are to better define the contemporary distribution of cobia along the U.S. east coast and to project potential shifts in distribution and phenology under future climate change scenarios. Location Chesapeake Bay and the U.S. east coast. Methods We developed a depth-integrated habitat suitability model using archival tagging data from cobia that were caught and tagged in Chesapeake Bay during summer months and coupled those data with high-resolution ocean models to project the contemporary and future distributions of cobia along U.S. east coast. Results During the winter months, suitable cobia habitat currently occurs in offshore waters off North Carolina and further south, whereas during the summer months, suitable habitat occurs in waters from Florida to southern New England. In warmer years, the availability of suitable habitat increases in northern latitudes. Under continued climate change over the next 40-80 years, suitable habitat is projected to shift northward and decrease over the shelf. Main conclusions Habitat distributions suggest cobia overwinter offshore and could inhabit waters further north during warmer months, into state jurisdictions that do not have strict management regulations for cobia. When waters are warmer, distributions are projected to shift poleward and seasonal migrations may begin earlier. These results can inform resource allocation discussions between fishery managers and resource users.

While commercial and recreational fisheries are often considered to compete with one another, in the Atlantic bluefin tuna fishery along the U.S. east coast individual fishermen are permitted to fish either commercially or recreationally on a trip-by-trip basis. How these individuals choose to fish can affect whether the fishery adheres to domestic bluefin tuna regulations and could impact the United States' ability to comply with international management measures. We applied a contingent sequential stated choice survey to bluefin tuna fishermen to identify key factors governing disposition decisions, evaluate the impact of inertia (habit formation), and forecast future harvest patterns. Those who primarily fished recreationally demonstrated more opportunistic harvest tendencies than their commercial counterparts, who were more stable in their preference to harvest fish for sale. Simulations based on model results indicated that fish disposition (harvest commercially, harvest recreationally, or release) varied widely based on regulatory, individual, and fishery characteristics. Such results can help managers to forecast harvest patterns and adopt regulatory tools to ensure that harvest remains within prescribed limits.

Background Cobia ( Rachycentron canadum ) is a cosmopolitan marine fish that inhabits tropical, sub-tropical, and temperate marine and estuarine waters and supports a major recreational fishery along the U.S. Atlantic and Gulf of Mexico coasts. Recent changes in U.S. cobia management have sparked controversy and highlighted limitations in our understanding of the species’ biology. This study utilized pop-up satellite archival tags (PSATs) to assess the movements, habitat utilization, and post-release survival of cobia that summer in Virginia waters. Results PSATs were deployed on 36 cobia caught in Virginia state waters using standard recreational techniques in August 2016 and August–September 2017. All fish larger than 37-in total length were tagged, and several of these were hooked deeply. No mortalities were inferred for the 20 cobia whose PSATs reported and remained attached for at least 10 days. Premature release of tags was an issue, and only five PSATs remained attached for the full 180-day deployment period. Some fish undertook long seasonal movements, with one individual entering Florida waters well beyond the current stock demarcation boundary. Several fish overwintered in waters offshore of North Carolina near the continental shelf break. Cobia demonstrated a strong affinity for waters ≥ 20 °C, even in the coldest months. They displayed distinct seasonal differences in habitat utilization, spending high proportions of their time near the surface during the summer months and extended periods at depths ≥ 20 m in the winter months. Conclusions Cobia are hardy fish with low post-release mortality when handled respectfully. Their migratory patterns are clearly temperature driven, and seasonal changes in habitat utilization means varied vulnerability to fishing gears. Further understanding of cobia migratory patterns, particularly in conjunction with spawning activity, is needed to best manage this species.

The western stock of Atlantic bluefin tuna receives recruits principally from spawning habitats in the Gulf of Mexico although the recent discovery of bluefin tuna larvae in the western North Atlantic Slope Sea calls into question whether there is another key source of recruits to the western stock. We tested whether age-0 juveniles occurring in the US Mid-Atlantic Bight during the late summer might originate from Slope Sea spawning by estimating the hatch date distribution based on otolith microstructural analysis given larval production occurs approximately two months later in the Slope Sea (late June to early August) than in the Gulf of Mexico (early April to mid-June). Following a review of the literature on ageing methodology for Thunnini species, we attempted trials on both sectioned and whole un-sectioned otoliths, and adopted the latter based on higher precision levels. Estimated ages ranged from 122 to 175 (days post hatch) for fish ranging 23.2-36.3 cm fork length. Hatch dates ranged 20 March to 12 May 2010, exhibiting a unimodal distribution. Hatch dates mainly occurred in early-April 2010, which corresponded to the spawning and larval production period for the Gulf of Mexico. Estimated growth rate (size-at-age) was 1.1 mm d(-1). Thus, we failed to observe evidence for recruitment from the newfound Slope Sea spawning region, albeit our sample represents only a single year and region. More conclusive inferences on recruitment from the Slope Sea spawning will depend on a greater sample of age-0 juveniles sampled across years or molecular approaches that can identify recruits in older juveniles and adults.

AbstractGenomic methodologies offer unprecedented opportunities for statistically robust studies of species broadly distributed in environments conducive to high gene flow, providing valuable information for wildlife conservation and management. Here, we sequence restriction site‐associated DNA to characterize genome‐wide single nucleotide polymorphisms (SNPs) in a broadly distributed and highly migratory large pelagic fish, striped marlin (Kajikia audax). Assessment of over 4,000 SNPs resolved spatiotemporal patterns of genetic connectivity throughout the species range in the Pacific and, for the first time, Indian oceans. Individual‐based cluster analyses identified six genetically distinct populations corresponding with the western Indian, eastern Indian, western South Pacific, and eastern central Pacific oceans, as well as two populations in the North Pacific Ocean (FST = 0.0137–0.0819). FST outlier analyses identified a subset of SNPs (n = 59) putatively under the influence of natural selection and capable of resolving populations separated by comparatively high degrees of genetic differentiation. Temporal collections available for some regions demonstrated the stability of allele frequencies over three to five generations of striped marlin. Relative migration rates reflected lower levels of genetic connectivity between Indian Ocean populations (mR ≤ 0.37) compared with most populations in the Pacific Ocean (mR ≥ 0.57) and highlight the importance of the western South Pacific in facilitating gene flow between ocean basins. Collectively, our results provide novel insights into rangewide population structure for striped marlin and highlight substantial inconsistencies between genetically distinct populations and stocks currently recognized for fisheries management. More broadly, we demonstrate that species capable of long‐distance dispersal in environments lacking obvious physical barriers to movement can display substantial population subdivision that persists over multiple generations and that may be facilitated by both neutral and adaptive processes. Importantly, surveys of genome‐wide markers enable inference of population‐level relationships using sample sizes practical for large pelagic fishes of conservation concern.

The billfishes are a group of highly migratory fishes comprising two extant families. The family Xiphiidae is monotypic and contains only the broadbill swordfish (Xiphias gladius Linnaeus, 1758), while the nineother species of billfishes constitute the family Istiophoridae. The outcomes of past phylogenetic investigations using partial nuclear and mitochondrial (mtDNA) sequences recommended a restructuring of Istiophoridae, by expanding the three existing genera into five: Makaira, Istiophorus, Kajikia, Istiompax, and Tetrapturus. However, several aspects of the Istiophoridae phylogeny remain unresolved, including the position of the genus Istiompax. In this investigation, we sequenced the whole mitogenomes for all istiophorid billfish species. Phylogenetic analyses supported the presence of five genera within Istiophoridae and resolved the placement of Istiompax as the sister taxon to Kajikia + Tetrapturus. Genetic identity between the striped marlin [Kajikia audax (Philippi, 1887)] and the white marlin [Kajikia albida (Poey, 1860)] was found to be higher than between Indo-Pacific and Atlantic clades of both the blue marlin (Makaira nigricans Lacepede, 1802) and sailfish [Istiophorus platypterus (Shaw, 1792)], suggesting recent isolation or ongoing genetic connectivity between K. audax and K. albida. An assessment of mtDNA gene regions identified NADH dehydrogenase subunit 4 (ND4) as best reflecting the phylogenetic reconstruction using the whole mitogenomes, while cytochrome b (Cytb) was the only gene region able to separate all species of billfishes in the present study. Our investigation increased the phylogenetic resolution of istiophorid billfishes and underscores the need for further investigations to fully resolve the complex genetic relationships within Tetrapturus and Kajikia.

The Atlantic Bluefin Tuna Thunnus thynnus is the target of a recreational fishery along the U.S. East Coast that is thought to be of considerable economic value. In some years, recreational landings have exceeded the sector’s annual subquota due to changes in fish availability, limited predictability of angler effort, and difficulties in real-time monitoring of catch. Understanding the drivers of angler behavior is critical for predicting how effort and harvest may vary as a function of changing fish availability, regulations, or costs. To investigate angler decision making, preferences, and values, we surveyed private recreational anglers from Maine to North Carolina and employed discrete choice experiments to determine how regulatory and nonregulatory trip-specific variables influence trip-taking behavior. A latent class-ranked logit model identified two distinct classes of anglers who exhibited differing preferences in regard to the importance of nonconsumptive aspects of Bluefin Tuna fishing (e.g., catch and release). Income and recent Bluefin Tuna targeting were the primary determinants of class membership, and higher-income anglers who had targeted Bluefin Tuna in the past 5 years were significantly more likely to be in the class that derives substantive benefits from nonconsumptive angling activities. An annual consumer surplus exceeding US$14 million was estimated for the 2015 fishery. We considered potential angler welfare impacts of possible management changes (compensating surplus) and identified a large amount of latent effort currently present in the fishery in the form of consumptiveoriented anglers. As a result, liberalization of harvest regulations could potentially lead to a large influx of effort into the fishery, which could impede the ability of managers to maintain harvest levels within prescribed limits. Over the past several decades, resource management scholars have advocated for better integration of the social sciences into fisheries management (Voiland and Duttweiler 1984; Fenichel et al. 2013). Understanding the human component of fisheries is important for predicting how management actions will affect the well-being of fishery participants, as well as for informing the allocation of fishery resources among competing user groups (Orbach 1980). In addition, without properly understanding the preferences and motivations of anglers, predicting behavioral responses (e.g., effort and harvest) is difficult and can potentially undermine management’s effectiveness and threaten a fishery’s sustainability (Fulton et al. 2011; Fenichel et al. 2013; Hunt et al. 2013). Fishing behavior may, for example, change as stock status or management strategies change, and simply extrapolating past behavior under different conditions could lead to inaccurate predictions (Fulton et al. 2011). Furthermore, while determining the preferences and motivations of recreational anglers is challenging (compared with commercial fishers, who are often thought to be largely motivated by profit), understanding drivers of angler behavior for a given fishery is critical for *Corresponding author: william.m.goldsmith@gmail.com Received December 3, 2017; accepted March 14, 2018 This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. North American Journal of Fisheries Management 38:680–697, 2018

Despite broad spatial distributions in the Atlantic, Pacific, and Indian oceans, relatively little is known about spearfishes (family Istiophoridae, genus Tetrapturus) due to their pelagic nature and relative scarcity. The limited biological understanding of spearfishes includes uncertain taxonomic relationships complicated by conserved morphology, thus specific identification relies heavily on geographic location of capture. Previous phylogenetic studies incorporating a limited number of loci and few representatives of each species have been unable to consistently resolve the four currently recognized species comprising Tetrapturus. In the present study, we surveyed 14 nuclear microsatellite loci and the mitochondrial DNA control region across relatively large numbers of samples per species to genetically discriminate spearfish species. Molecular data resolved roundscale spearfish (n = 89) (Tetrapturus georgii Lowe, 1841) and Mediterranean spearfish (n = 12) (Tetrapturus belone Rafinesque, 1810) as genetically distinct groups. Longbill spearfish (n = 79) (Tetrapturus pfluegeri Robins and de Sylva, 1963) and shortbill spearfish (n = 29) (Tetrapturus angustirostris Tanaka, 1915) were not consistently resolved. A single individual collected in the western central Atlantic Ocean off Brazil assigned to shortbill spearfish and likely represents a vagrant. Additionally, a spearfish sampled from the Indian Ocean off eastern South Africa was morphologically identified as a longbill spearfish, and the molecular profile of this specimen was consistent with the morphological identification. Our study represents the most extensive molecular evaluation of the spearfishes to date. Results reported here underscore the substantial level of genetic similarity between longbill and shortbill spearfishes, and suggest high-resolution genomic methods may be required to unambiguously resolve these species.

Biological invasions represent an important component of global change, with potentially huge detrimental effects on native biological biodiversity and ecosystems. Knowledge about invasion history provides information about the invasion process and the origin and genetic composition of invading populations. To clarify the source and invasive routes of a successful world-wide invader, the veined rapa whelk, Rapana venosa, genetic variability of samples from five representative native populations from coasts of Japan and China and 13 worldwide invasive populations was analyzed using 11 nuclear microsatellite loci. A dramatic decrease of genetic variation was detected in the invasive populations compared with the native populations. The results demonstrated that R. venosa was capable of establishing itself in many areas despite a dramatic genetic bottleneck, suggesting that a remarkable reduction of genetic diversity is not a limiting factor for short-term success of this invasive species. Considering the lack of mitochondrial variation previously observed in the invasive populations, the dramatic genetic bottleneck and the allele distribution detected using microsatellites suggested that the original introduced Black Sea population could have been founded by very few individuals, perhaps only a single female and a single male. The initial invasive Black Sea population was likely an accidental introduction from Japan, and then invaded the Adriatic Sea by range expansion, which served as a source for subsequent invasive populations in Europe and America by various transport vectors. In addition, microsatellite alleles in the invasive populations showed a tendency to mutate with the addition or deletion of a single repeat, which is consistent with the stepwise mutation model. Our findings provide a good example of how an aquatic invader with a drastic genetic bottleneck and very low genetic diversity rapidly expands its geographical range.

The genetic basis of population structure in white marlin (Kajikia albida) is not well understood. Previous evaluation of genetic population structure in this species utilized a small number of molecular markers to survey genetic variation across opportunistically collected samples of adults, resulting in statistically significant levels of genetic differentiation for some pairwise comparisons and global levels of genetic differentiation that approached statistical significance. This study increased statistical power to improve resolution of genetic population structure in white marlin by surveying a larger number of molecular markers across sample collections of increased size, including collections from additional geographic locations and a robust collection of larvae. Increased statistical power resulted in lower levels of genetic heterogeneity compared with the previous study, and results were consistent with the presence of a single genetic stock of white marlin in the Atlantic Ocean. These results indicate that when statistical power is low, the ability to distinguish noise from a true signal of population structure is compromised. This relationship is especially important for population genetic assessments of marine fishes where genetic differentiation, if it exists, is expected to be low.

Pop-up satellite archival tags (PSATs) are a valuable tool for estimating mortality of pelagic fishes released from commercial and recreational fishing gears. However, the high cost of PSATs limits sample sizes, resulting in low-precision post-release mortality estimates with little management applicability. We evaluate the performance of a lower-cost PSAT designed to enable large-scale post-release mortality studies. The tag uses solar rather than battery power, does not include a depth sensor, and transmits daily summaries of light and temperature data rather than high-resolution habitat profiles, contributing to a substantially lower per-unit price. We assessed the tag’s ability to detect mortality while also estimating the post-release mortality of juvenile (119–< 185 cm) Atlantic bluefin tuna (Thunnus thynnus) caught using light-tackle angling methods along the US east coast.

The comparative morphology of the scales of roundscale spearfish Tetrapturus georgii and white marlin Kajikia albida was investigated. In addition, variation in scale morphology across different body regions within each species was analysed. Although considerable morphological variation was observed among scales from different body regions in both species, scales of K. albida generally have pointed anterior ends, fewer posterior points and are more heavily imbricated than those of T. georgii, which are frequently rounded anteriorly, often have many posterior points and are separated farther within the skin. In all sampled body regions and individuals, scales of T. georgii are significantly broader and have a lower length‐to‐width aspect ratio than those of K. albida. Superficial to the scales are denticular plates, which are ossified formations occurring on the surface layer of the epidermis; these were observed and described for T. georgii, K. albida and blue marlin Makaira nigricans. Detailed scale descriptions allow for a more accurate characterization of the variation within and differences between these two species and could potentially be a valuable tool for investigating istiophorid systematics.

White Marlin Kajikia albida are targeted by recreational fisheries in tropical and subtropical waters of the Atlantic Ocean. Off the U.S. East Coast, the vast majority of White Marlin are released after capture. Federal regulations prohibit anglers from removing a White Marlin from the water unless the fish is to be retained; however, numerous photographs of anglers holding White Marlin out of the water are posted on the Internet each summer, demonstrating that there is considerable noncompliance with this management measure. To better understand the effect of air exposure on postrelease survival of White Marlin, we attached pop-up satellite archival tags (PSATs; programmed to release after 30 d) to individuals that were caught on natural baits rigged with circle hooks and that were removed from the water for a period of 1 min (n = 6 fish), 3min (n = 5 fish), or 5 min (n = 7 fish). We compared our results with those from a previous study in which PSATs were used to follow the fates of 59 White Marlin that were caught on circle hooks but not removed from the water. The proportion of postrelease mortalities increased with air exposure duration; the overall rate of postrelease mortality was significantly higher for White Marlin that were subjected to air exposure (33.3%) than for those that remained in the water (1.7%). These data provide strong support for the current U.S. regulation prohibiting the removal of a White Marlin from the water if the fish is to be released. Effective communication of the deleterious effects of air exposure on White Marlin should help to deter the practice of removing fish from the water among members of the recreational angling community, which has been supportive of other conservation measures for this species.

Bluefin Tuna Thunnus thynnus are highly sought after in commercial and recreational fisheries along the East Coast of North America. To appropriately assess and manage Atlantic Bluefin Tuna (ABT), it is necessary to understand their habitat use during multiple ontogenetic stages. We tagged 17 juvenile ABT in the northwest Atlantic Ocean with pop-up satellite archival tags (PSATs) to determine environmental factors that may affect habitat use. The PSATs were deployed off the coast of Massachusetts in August and September 2012. A generalized linear mixed model was applied to determine factors affecting the mean depth occupied by fish, and beta regression was used to understand factors affecting the proportion of time spent below the thermocline. Thermocline depth significantly affected the mean depth occupied by juvenile ABT and the proportion of time they spent below the thermocline. Time period (dawn, day, dusk, and night) also significantly affected the mean depth occupied by juvenile ABT. Additionally, the time period x lunar illumination interaction had a significant effect on the proportion of time spent below the thermocline. This study is the first to demonstrate that environmental factors such as thermocline depth, time period, and lunar illumination can significantly impact vertical habitat use by juvenile ABT and demonstrates the utility of generalized linear mixed models for investigating fish habitat use.

The combination of oceanographic barriers and habitat heterogeneity are known to reduce connectivity and leave specific genetic signatures in the demographic history of marine species. However, barriers to gene flow in the marine environment are almost never impermeable which inevitably allows secondary contact to occur. In this study, eight sampling sites (five along the South African coastline, one each in Angola, Senegal and Portugal) were chosen to examine the population genetic structure and phylogeographic history of the cosmopolitan bluefish (Pomatomus saltatrix), distributed across a large South-east Atlantic upwelling zone. Molecular analyses were applied to mtDNA cytochrome b, intron AM2B1 and 15 microsatellite loci. We detected uncharacteristically high genetic differentiation (FST 0.15-0.20; P<0.001) between the fish sampled from South Africa and the other sites, strongly influenced by five outlier microsatellite loci located in conserved intergenic regions. In addition, differentiation among the remaining East Atlantic sites was detected, although mtDNA indicated past isolation with subsequent secondary contact between these East Atlantic populations. We further identified secondary contact, with unidirectional gene flow from South Africa to Angola. The directional contact is likely explained by a combination of the northward flowing offshore current and endogenous incompatibilities restricting integration of certain regions of the genome and limiting gene flow to the south. The results confirm that the dynamic system associated with the Benguela current upwelling zone influences species distributions and population processes in the South-east Atlantic.

White marlin, a highly migratory pelagic marine fish, support important commercial and recreational fisheries throughout their range in the tropical and subtropical Atlantic Ocean. More than 10 000 individuals can be caught annually in the United States recreational fishery, of which the vast majority are captured on circle hooks and released alive. The probability of post-release mortality of white marlin released from circle hooks has been documented to be <0.02, but the associated physiological stress resulting from capture and handling techniques has not been characterized despite its importance for understanding the health of released fish. We examined the physiological response of 68 white marlin caught on circle hooks in the recreational fishery and followed the fate of 22 of these fish with pop-up satellite archival tags programmed to release after 30 days. Measures of plasma sodium, chloride, glucose and lactate concentrations taken from fish that were briefly and consistently (mean = 120 s, standard deviation = 40 s) removed from the water increased with angling time, but post-release mortality was inversely related to angling time. The probability of post-release mortality was predicted by elevated plasma potassium concentrations and was more than 10 times greater than has been previously reported for white marlin caught on circle hooks that were not removed from the water. This disparity in estimates of post-release mortality suggests that removal of fish from the water for physiological sampling greatly heightens stress, disrupts homeostasis and thus increases the probability of post-release mortality. Our results demonstrate that elevated concentrations of plasma potassium predict mortality in white marlin and that the probability of post-release mortality is highly dependent on post-capture handling procedures.