Makaira Nigricans Research Articles

Atlantic Blue Marlin, Boops, Chironex Fleckeri, and General Practitioner – Sick Person Optimization Algorithms mization Algorithms

In this paper Atlantic blue marlin (ABM) optimization algorithm, Boops optimization (BO) algorithm, Chironex fleckeri Search Optimization (CSO) algorithm, General practitioner -Sick person (PS) optimization algorithm are applied for solving factual power loss reduction problem. The regular actions of Atlantic blue marlin are emulated to design the Atlantic blue marlin (ABM) optimization algorithm and populace in the examination space is capriciously stimulated. Boops optimization (BO) algorithm is designed by imitating the actions of Boops. Boops possess the obliging stalking physiognomies. As a cluster they stalk the quarry by forming the key and subordinate clusters CSO is based on the drive and search behaviour of Chironex fleckeri. Obviously Chironex fleckeri will exploit the limbs to paralyze the pray by injecting the rancour. In real time world a General practitioner will treat the Sick person with various procedures and it has been imitated to model the Projected PS algorithm. In general people will be inoculated and then with respect to disorder and disease- medical treatment will be given by medicines. Inoculation, medicine and operation are the procedures have been considered as the phases of the projected PS algorithm. Atlantic blue marlin (ABM) optimization algorithm, Boops optimization (BO) algorithm, Chironex fleckeri Search Optimization (CSO) algorithm, General practitioner -Sick person (PS) optimization algorithm validated in IEEE 57, 300 systems and 220 KV network. Factual power loss lessening, power divergence restraining, and power constancy index amplification has been attained.

Fishing effort dynamics around the Galápagos Marine Reserve as depicted by AIS data.

The waters around the Galápagos Marine Reserve (GMR) are important fishing grounds for authorized artisanal vessels fishing within the reserve as well as for national and foreign industrial fleets operating in the wider Ecuadorian Insular Exclusive Economic Zone (IEEZ). Although it was not originally designed for fisheries management, Automatic Identification System (AIS) data provides useful, open access, near real-time and high-resolution information that allows for increased monitoring, particularly around Marine Protected Areas (MPAs) and in Areas Beyond National Jurisdiction. This study uses AIS data provided by Global Fishing Watch to assess the spatial distribution and seasonal dynamics of fishing effort by vessel flag within the GMR and the IEEZ from 2012 to 2021. Based on kernel density estimation analysis, we determinate the core-use areas (50%) and spatial extent (95%) of fishing activities by fleets (Ecuadorian and foreign), gear types and seasons (warm, from December to May; and cold, from June to November). Our results show that the Ecuadorian fleet recorded the most observed fishing hours in the study area, with 32,829 hours in the IEEZ and 20,816 hours within the GMR. The foreign flags with the most observed fishing hours in the IEEZ were Panama (3,245 hours) and Nicaragua (2,468.5 hours), while in the GMR were the 'Unknown flag' (4,991.4 hours) and Panama (133.7 hours). Vessels fished employing different fishing gears, but the waters of the GMR and IEEZ were mostly targeted by tuna purse-seiners and drifting longlines. The spatial distribution of the fishing effort exhibits marked seasonal variability, likely influenced by seasonal migrations of target species such as tunas (e.g., Thunnus albacares, T. obesus and Katsuwonus pelamis), marlins (e.g., Makaira nigricans) and sharks (e.g., Alopias pelagicus). The collection and use of this type of spatial and seasonal information is an essential step to understand the dynamics of fishing activities in national waters and improve fisheries management, particularly in less studied areas and fisheries.

Betanodavirus meningoencephalitis in an Atlantic blue marlin.

Viral nervous necrosis (viral encephalopathy and retinopathy) is caused by piscine nodavirus (Nodaviridae, Betanodavirus). Since 1986, this highly infectious virus has caused mass mortalities of up to 100% in farmed saltwater and freshwater fish around the world (with the exception of South America and Antarctica), affecting >60 species across 10 orders. The Atlantic blue marlin (Makaira nigricans Lacépède, 1802) is a top-level predator found throughout the tropical waters of the Atlantic and Indo-Pacific oceans. Despite their popularity as a sportfish, relatively little is known about the Atlantic blue marlin and other billfish. We describe here chronic betanodavirus infection in a juvenile Atlantic blue marlin, which is, to our knowledge, the first report of disease in M. nigricans.

Seasonally mediated niche partitioning in a vertically compressed pelagic predator guild.

Niche partitioning among closely related, sympatric species is a fundamental concept in ecology, and its mechanisms are of broad interest for understanding ecosystem functioning and predicting the impacts of human-driven environmental change. However, identifying mechanisms by which top marine predators partition available resources has been especially challenging given the difficulty of quantifying resource use of large pelagic animals. In the eastern tropical Pacific (ETP), three large, highly mobile and ecologically similar pelagic predators (blue marlin (Makaira nigricans), black marlin (Istiompax indica) and sailfish (Istiophorus platypterus)) coexist in a vertically compressed habitat. To evaluate each species' ecological niche, we leveraged a decade of recreational fisheries data, multi-year satellite tracking with high-resolution dive data, and stable isotope analysis. Fishery interaction and telemetry-based three-dimensional seasonal utilization distributions suggested high spatial and temporal overlap among species; however, seasonal and diel variability in diving behaviour produced spatial partitioning, leading to low trophic overlap among species. Expanding oxygen minimum zones will reduce the available vertical habitat within predator guilds, likely leading to increases in interspecific competition. Thus, understanding the mechanisms of habitat partitioning among predators in the vertically compressed ETP can provide insight into how predators in other ocean regions may respond to vertically limited habitats.

The rostral micro-tooth morphology of blue marlin, Makaira nigricans.

Billfish rostra potentially have several functions; however, their role in feeding is unequivocal in some species. Recent work linked morphological variation in rostral micro-teeth to differences in feeding behavior in two billfish species, the striped marlin (Kajikia audax) and the sailfish (Istiophorus platypterus). Here, we present the rostral micro-tooth morphology for a third billfish species, the blue marlin (Makaira nigricans), for which the use of the rostrum in feeding behavior is still undocumented from systematic observations in the wild. We measured the micro-teeth on rostrum tips of blue marlin, striped marlin, and sailfish using a micro-computed tomography approach and compared the tooth morphology among the three species. This was done after an analysis of video-recorded hunting behavior of striped marlin and sailfish revealed that both species strike prey predominantly with the first third of the rostrum, which provided the justification to focus our analysis on the rostrum tips. In blue marlin, intact micro-teeth were longer compared to striped marlin but not to sailfish. Blue marlin had a higher fraction of broken teeth than both striped marlin and sailfish, and broken teeth were distributed more evenly on the rostrum. Micro-tooth regrowth was equally low in both marlin species but higher in sailfish. Based on the differences and similarities in the micro-tooth morphology between the billfish species, we discuss potential feeding-related rostrum use in blue marlin. We put forward the hypothesis that blue marlin might use their rostra in high-speed dashes as observed in striped marlin, rather than in the high-precision rostral strikes described for sailfish, possibly focusing on larger prey organisms.

Fishery, systematics and stock dynamics of billfishes landed along the Indian coast

Sailfishes, marlins, spearfishes and swordfishes commonly referred to as billfishes are highlymigratory species, with a worldwide distribution in tropical and subtropical oceans. Thelandings of billfishes along the Indian coast registered an increasing trend with an estimatedlanding of 14,759 t in 2019. Kerala (41%) contributed the maximum followed by Tamil Nadu(28%), Andhra Pradesh (18%), Gujarat (8%) and Maharashtra (2%) to the total billfish landingsduring the last decade. Mechanised gillnetter cum hook and line was the major gear landingbillfishes. The major species landed during 2012-2019 were Istiophorus platypterus (52.2%),Istiompax indica (21.1%), Makaira nigricans (7.3%), Xiphias gladius (17.2%) and Kajikia audax(2.3%). Four of these species could be easily distinguished by COI barcodes but, the stripedmarlin, K. audax showed high sequence similarity with K. albida and cannot be distinguishedby barcodes alone. Control region (889 bp) provided a better phylogenetic signal, consistentwith that of the whole mitochondrial genome topology. The stock status plots of billfishesdepicted that, all the species were in the developing and exploited phase. Growth, mortalityand exploitation rates estimated for four billfishes indicated that the present fishing ratesand biomass levels are at safe levels and there is considerable scope for enhancing theirfishery. Keywords:CO1 barcodes, Exploitation rate, Large pelagics,Life history, Stock status plots

Variability in billfish vertical distribution and fishing interactions driven by environmental conditions in the Eastern Tropical Pacific Ocean

Abstract Blue marlin (Makaira nigricans) and sailfish (Istiophorus platypterus) are ecologically important predators and valuable species throughout the world’s recreational, commercial, and subsistence fisheries. Comparing multi-species vertical habitat use can inform ecological uncertainties such as inter-species competition, as well as relative vulnerabilities to fishing activities. In this study, we identified key differences in both depth use and which environmental variables drive these selections, which highlights the variability in the catchability both as target species in recreational fisheries and bycatch in commercial fisheries. To understand these two species’ vertical habitat use, we examined depth profiles from 26 sailfish and 48 blue marlin tagged with pop-up satellite archival tags deployed in the Eastern Tropical Pacific Ocean. While both species are surface-oriented, we found evidence of vertical niche partitioning where sailfish spend more time at deeper depths than blue marlin. Blue marlin recorded an average mean depth of 18.5 m (±10.8 m) during daytime and 5.2 m (±5.5 m) at nighttime (Figure 31a), while sailfish recorded an average mean depth of 23.6 m (±11.1 m) during daytime and 6.45 m (±4.64 m) at nighttime. Generalized additive mixed models fitted to predict mean and max depth revealed sea level anomaly (SLA), oxygen, sea surface temperature, and mixed layer depth as significant predictors of vertical habitat use for both species. We also examined catch logs from three recreational fishing lodges in Central America to understand the influence of environmental conditions on billfish sightings per unit effort. For blue marlin and sailfish, SLA was a significant predictor in each of the four depth models (mean day, mean night, max day, max night). SLA was the variable with highest percent deviance explained for all four sailfish depth models and three of the four blue marlin depth models and had a positive relationship with all response variables for all four blue marlin depth models and three sailfish depth models (mean daytime, max daytime, max nighttime), where higher positive SLA values were associated with deeper depth responses.

Patrolling the border: Billfish exploit the hypoxic boundary created by the world's largest oxygen minimum zone.

Pelagic predators must contend with low prey densities that are irregularly distributed and dynamic in space and time. Based on satellite imagery and telemetry data, many pelagic predators will concentrate horizontal movements on ephemeral surface fronts-gradients between water masses-because of enhanced local productivity and increased forage fish densities. Vertical fronts (e.g. thermoclines, oxyclines) can be spatially and temporally persistent, and aggregate lower trophic level and diel vertically migrating organisms due to sharp changes in temperature, water density or available oxygen. Thus, vertical fronts represent a stable and potentially energy rich habitat feature for diving pelagic predators but remain little explored in their capacity to enhance foraging opportunities. Here, we use a novel suite of high-resolution biologging data, including in situ derived oxygen saturation and video, to document how two top predators in the pelagic ecosystem exploit the vertical fronts created by the oxygen minimum zone of the eastern tropical Pacific. Prey search behaviour was dependent on dive shape, and significantly increased near the thermocline and hypoxic boundary for blue marlin Makaira nigricans and sailfish Istiophorus platypterus, respectively. Further, we identify a behaviour not yet reported for pelagic predators, whereby the predator repeatedly dives below the thermocline and hypoxic boundary (and by extension, below the prey). We hypothesize this behaviour is used to ambush prey concentrated at the boundaries from below. We describe how habitat fronts created by low oxygen environments can influence pelagic ecosystems, which will become increasingly important to understand in the context of global change and expanding oxygen minimum zones. We anticipate that our findings are shared among many pelagic predators where strong vertical fronts occur, and additional high-resolution tagging is warranted to confirm this.

Seasonal and diel habitat use of blue marlin Makaira nigricans in the North Atlantic Ocean

Abstract Knowledge of blue marlin, Makaira nigricans, movement patterns across a range of spatiotemporal scales is important for understanding the ecology of this epipelagic fish, informing responsible management strategies, and understanding the potential impacts of a changing ocean climate to the species. To gain insight into movement patterns, we analyzed data from 66 blue marlin satellite-tagged between 2001 and 2021 throughout the North Atlantic. We recorded migrations connecting west and east Atlantic tagging locations, as well as long-term residency within small sub-regions. Blue marlin showed a pattern of latitudinal migration, occupying lower latitudes during cooler months and higher latitudes in warmer months. Diving data indicate blue marlin primarily inhabited a shallow vertical habitat with deeper diving associated with higher sea surface temperatures and dissolved oxygen content. Consistent patterns in diel vertical habitat use support the hypothesis that these fish are visual hunters, diving deeper during the day, as well as dawn, dusk, and full moon periods. The wide-ranging movements of blue marlin indicate that traditional spatial management measures, such as static marine reserves, are unlikely to be effective in reducing the fishing mortality of this species. Longer tag deployment durations are required to delineate its annual and multi-annual migratory cycle.

Total mercury, methylmercury, and selenium concentrations in blue marlin Makaira nigricans from a long-term dataset in the western north Atlantic

Mercury in seafood is a neurotoxicant that threatens human health. Dynamic rates of mercury emission, re-emission, and atmospheric deposition warrant studies into mercury concentrations in fish because many are consumed by humans and can serve as sentinels of mercury levels in the environment. We modeled trends in total mercury content in an apex marine fish predator, Atlantic blue marlin Makaira nigricans, whose muscle tissues were opportunistically sampled from North Carolina (USA) sportfishing tournaments over a discontinuous time period: between 1975 and 77 and 1998–2021 (n = 148). The model-estimated influence of marlin weight on total mercury concentration was constant across years (shared slope) allowing for comparisons of weight-corrected mercury concentrations among years. Weight-corrected total mercury concentrations revealed an inter-decadal decline of approximately 45 % between the 1970s and late 1990s and then variable but relatively stable concentrations through 2021. The mean (SD) wet weight concentration of total mercury was 9.47 (4.11) from 1975 to 77 and 4.17 (2.61) from 2020 to 2021. Methylmercury and selenium were measured on a subset of fish to address questions related to human health and consumption. Methylmercury levels (mean = 0.72 μg/g) were much lower than total mercury (mean = 4.69 μg/g) indicating that total mercury is not a good proxy for methylmercury in Atlantic blue marlin. Selenium, examined as a Se:Hg molar ratio and as a selenium health benefit value (HBVSe), showed high protective value against mercury toxicity. Long-term trends in the concentration of mercury in blue marlin should continue to be monitored to determine whether policies to mitigate anthropogenic contributions to global mercury are achieving their intended goals and to provide information to inform safe human consumption.

High-resolution post-release behaviour and recovery periods of two highly prized recreational sportfish: the blue marlin and sailfish

Abstract High recreational catch rates of istiophorid billfishes in the eastern tropical Pacific (ETP) have led to substantial eco-tourism derived economic benefits for the countries in the region, prompting many countries to mandate catch-and-release practices for recreational anglers. Previous estimates of billfish post-release behaviours and recovery periods after these physiologically stressful capture events, however, vary widely depending on the type of tag used. Using high-resolution, multi-sensor biologging tags, we provide a fine-scale, detailed view of the behaviour and recovery periods of blue marlin (Makaira nigricans; n = 9) and sailfish (Istiophorus platypterus, Istiophoridae; n = 9) caught in a typical recreational fishery in the ETP. Angling times ranged from 4 to 90 min, and fish were monitored for periods of 6–70 h after release. Blue marlin showed a characteristic long, deep dive immediately after release, with significantly greater duration associated with longer fight times, a behaviour not typical for sailfish. Diving depths were, however, much shallower than those previously reported for both species due to the shallow thermocline and oxycline present in the ETP. Data from 40 derived metrics from acceleration (i.e. tailbeat period, amplitude, pitch, etc.) and physical parameters (i.e. depth, speed, temperature, oxygen saturation, etc.) used to quantify a recovery period suggest blue marlin and sailfish recover 9.0 ± 3.2 and 4.9 ± 2.8 h after release, respectively. Our high-resolution assessment of post-release behaviour suggests that these billfish are capable of rapid physiological recovery after capture in recreational fisheries, and that catch-and-release practices like those used here can be an effective approach to conserve and sustain billfish populations in the ETP. Predicted climate change caused shallowing of the oxygen minimum zone, however, would increase the vertical habitat compression present in this region, potentially prolonging or inhibiting recovery.

Global habitat loss of a highly migratory predator, the blue marlin (Makaira nigricans)

AbstractAimClimate change is driving the redistribution of species throughout the oceans. However, the speed and magnitude of species responses, including shifts in their distribution, are variable and species specific. Quantifying the effect of environmental conditions on species distributions is crucial to informing management and conservation efforts. Blue marlin (Makaira nigricans) is a wide‐ranging top predator occurring circumglobally in tropical and subtropical waters and is heavily impacted by international longline fisheries. This study aimed to predict the global distribution of blue marlin and characterize the effects of climate variability thereon.LocationGlobal.MethodsTo conduct this study, pop‐up satellite archival tags (n = 144) deployed by recreational anglers through a global citizen science programme were used to generate a large tracking data set (14,928 days, 210,983 km from deployment to pop‐up locations) of blue marlin movement across three ocean basins. State‐space modelled tracking position estimates were used to create a species distribution model to represent global habitat suitability for blue marlin. Habitat suitability was determined by fitting a generalized additive mixed model (GAMM) as a function of environmental covariates which was used to predict monthly global blue marlin habitat from 2000 to 2016.ResultsBlue marlin habitat preference had the strongest association with sea surface temperature. Seasonal variation in blue marlin habitat occurs primarily at the latitudinal edges of the distribution range. Over the duration of the study, 96% of core habitat declined in suitability, with a concurrent poleward increase in suitability of marginal habitat.Main ConclusionsThis study highlights the successful application of citizen‐based science to develop a long‐term global telemetry dataset. The present‐day loss of highly suitable habitat suggests ocean warming may be making equatorial waters less suitable even to highly mobile species. Blue marlin is likely to respond by following preferred habitat as it shifts poleward.

Economic contribution and social welfare of recreational charter boat fisheries in the northeast Atlantic: The cases of Galicia (Spain) and Madeira archipelago (Portugal)

Recreational charter boat fisheries provide alternative economic development to traditional commercial fisheries, especially to coastal communities in warm seas. Charter boat fishing has been little studied in temperate regions, and the factors that trigger its development and social contribution to fishing communities are unknown. We performed an economic analysis of recreational charter boat fisheries in the Eastern North Atlantic to assess their contribution to social welfare. We selected two case studies located in Galicia (NW Spain) and Madeira archipelago (Portugal). The two cases differ in the socioecological attributes in which recreational charter boat fishing is developed (e.g., relevance of commercial fishing, tourism, or targeted species), that were included in the assessment. Up to 7 charter fishing companies were identified in Galicia (10 boats) and 14 in Madeira (18 boats), and information on the costs and benefits of the activity were collected by a questionnaire answered by company managers and skippers. Charter boats in Galicia are operating throughout the year, and anglers mostly engage in bottom fishing targeting demersal predators like ballan wrasse (Labrus bergylta) and European seabass (Dicentrarchus labrax) that they retain. Despite the strong seasonality of the fishery in Madeira, focused on summers, the fishing effort is higher than in Galicia. On average, charter boats go fishing for 39.3 ± 41.5 (SD) fishing journeys and take 2 500 anglers on board per year in Galicia, while in Madeira they fish 63.7 ± 32.7 journeys and take 3 200 anglers on board. Anglers target in Madeira pelagic top predators like blue marlin (Makaira nigricans), or some tuna species, e.g., bigeye (Thunnus obesus), by trolling in a catch and release fishery. The economic balance of companies was more favorable in Madeira, with an average gross annual profit of € 28 883 ± 30 755, while economic yield in Galicia was € 4 444 ± 7 916. We also applied a travel cost method to assess the recreation demand of recreational fishing trips based on a questionnaire answered by 150 clients in Galicia and 55 in Madeira. We estimated the visitor surplus mean value to be € 1 385 per year in Galicia (95% confidence interval, CI95%= € 1 219 – € 1 550), and € 1 738 in Madeira (CI95%= € 1 433 – 2 043). The social annual recreation value of Galician fishery was worth € 3.4 Million, ranging between € 3.0 M and € 3.8 M, a value well below the annual economic impact generated by commercial fishing (€ 700 M). The recreation value of the charter boat fishery in Madeira, € 6.3 M, ranging between € 5.2 M and € 7.5 M, is comparable to the annual economic impact of commercial fishing, that contributes to the local economy with € 12 M.

First insights into the movements and vertical habitat use of blue marlin (Makaira nigricans) in the eastern North Atlantic

BackgroundThe blue marlin (Makaira nigricans) is a vulnerable migratory fish inhabiting tropical and subtropical pelagic waters of the Atlantic, Pacific and Indian Oceans. The biology and spatial ecology of the species in the eastern North Atlantic is poorly understood, despite being exploited in the region by recreational and commercial fisheries. Here, we present results of the first study to use pop-up satellite archival tags to track blue marlin off Madeira, Portugal (n = 3) and obtain insights into the movements and habitat use of the species within the eastern North Atlantic.ResultsBlue marlin were tracked for 24 to 83 days, moving from Madeira to pelagic waters off the Canary Islands, Cape Verde Islands, as well as along the continental shelf brake of Europe and Africa. Blue marlin spent 71% of their time in the upper 5 m and 89% in the upper 50 m, though all individuals dived to depths over 200 m (maximum: 336 m). Temperature at depth ranged from 12 to 28.6 °C, but the greatest proportion of time was spent in waters between 20 and 26 °C. Detailed depth and temperature time-series data were obtained from a tag recovered eight years later. These data show clear diel differences in depth use, involving consistent use of the surface at night and deeper dive activity during the day, predominately to depths greater than 50 m.ConclusionsThe highly migratory patterns of this vulnerable species in the eastern North Atlantic highlights the need for both local and international conservation measures. Depth-use patterns, particularly the high usage of the upper 5 m of the water column, make them susceptible to surface longline fisheries.

Deciphering the Trophic Ecology of Three Marlin Species Using Stable Isotope Analysis in Temperate Waters Off Southeastern Australia

Understanding the unique feeding behaviours of oceanic fish, such as marlin, is key to their effective management. Marlin are notoriously difficult to study, however, and the limited research on marlin feeding shows that diet can vary greatly between species and geographic regions. One region where marlin feeding behaviours are particularly poorly understood are temperate eastern Australian waters. This study collected marlin tissue from game fishing tournaments between latitudes 32°43′06.5″S/152°08′50.1″E to 34°40′12.9″S/150°51′34.3″E between 2010 and 2021, and used stable isotope analysis (SIA) to assess the trophic ecology of the three species of marlin occurring in the region: black (Istiompax indica), blue (Makaira nigricans), and striped (Kajikia audax) marlin. All species had similar δ13C values, but δ15N differed between species, with higher variability observed in blue marlin than in the other two species. Sulphur isotopes were key in identifying the relative contribution of coastal or benthic influences on marlin diet, with δ34S suggesting that blue marlin had less coastal/benthic dietary influence than black or striped marlin. Incorporation of δ34S into SIA for marlin is thus recommended for future studies. Some differences in isotope values across locations and dates were found, however, the uneven sample sizes due to the opportunistic sampling limited the ability to understand spatial or seasonal differences. These findings show that marlin followed similar dietary trends to conspecifics in other regions despite temperate eastern Australian waters being one of the few with three marlin species commonly co-occuring. This suggests that interspecies resource competition is not a major force driving the demography of these species in eastern Australian waters. This research highlights a need for specific management strategies at a species level, particularly for blue marlin. Future research incorporating prey isoscapes and baselines assessed over a wider range of marlin sizes is suggested to further improve our knowledge and capacity to manage the marlin of eastern Australian waters.

Lacunae rostralis: A new structure on the rostrum of sailfish Istiophorus platypterus.

Recent comparative studies of billfishes (Istiophoridae and Xiphiidae) have provided evidence of differences in the form and function of the rostra (bill) among species. Here, we report the discovery of a new structure, lacuna rostralis, on the rostra of sailfish Istiophorus platypterus, which is absent on the rostra of swordfish Xiphias gladius, striped marlin Kajikia audax and blue marlin Makaira nigricans. The lacunae rostralis are small cavities that contain teeth. They were found on the ventral rostrum surface of all I. platypterus specimens examined and dorsally in half of them. Ventrally, the lacunae rostralis were most prominent in the mid-section of the rostrum. Dorsally, they occurred closer to the tip. The density of lacunae rostralis increased towards the rostrum tip but, because they are smaller in size, the percentage of rostrum coverage decreased. The teeth located within the lacunae rostralis were found to be different in size, location and orientation from the previously identified micro-teeth of billfish. We propose two potential functions of the lacunae rostralis that both relate to the use of the bill in feeding: mechanoreception of prey before tapping it with the bill and more efficient prey handling via the creation of suction, or physical grip.

Effect of High-Pressure Treatment on Blue Marlin (Makaira nigricans) Quality During Storage

ABSTRACT The quality effects of high-pressure processing (HPP) under 200, 300, 400, and 500 MPa for 5 min on blue marlin meat stored at 4°C and 15°C were evaluated. Pressurization under a treatment of >300 MPa on marlin samples significantly delayed the increase in aerobic plate count (APC) during storage at 4°C and 15°C. Meanwhile, the samples pressurized more than 200 MPa had considerably lower levels of total volatile basic nitrogen (TVBN) and histamine than control sample during storage at 4°C and 15°C. Overall, these results indicated that pressure up to 300 MPa for 5 min significantly retarded the growth of APC and TVBN and histamine production. Therefore, HPP on marlin meats is a useful technique to prevent quality deterioration, extend the shelf-life, and reduce histamine fish poisoning risk

Trophic relationships revealed by dart tags found in the stomachs of large pelagic fishes in the Atlantic Ocean

Plastic dart tags are the main type of tag used in all major fish tagging projects but their potential for studying trophic relationships has never been addressed. The occurrence of dart tags in the stomach contents of large pelagic fishes and direct observations onboard tagging vessels reveal novel information on predation and cannibalism by tropical tunas in the Atlantic Ocean. The observations were all made during the Atlantic Ocean Tropical Tuna Tagging Programme (AOTTP), which targeted bigeye tuna (Thunnus obesus), yellowfin tuna (Thunnus albacares), skipjack tuna (Katsuwomis pelamis), wahoo (Acanthocybium solandri), and little tunny (Euthynnus alletteratus). During the programme (so far) 5 conventionally tagged fish have been reported in stomach contents from captures made in Brazil, São Tome and Principe, and Ivory Coast: including one yellowfin tuna and two skipjack tunas in a yellowfin tuna, one yellowfin tuna in a blue marlin (Makaira nigricans), and one yellowfin tuna in a non-identified shark. We use these observations to illustrate the potential role that dart tags could play in helping describe trophic interactions among marine pelagic fish species.

Application of Fishery-independent Data as an Alternative Source for Determining Relative Abundance Indices of Blue Marlin, Makaira nigricans (Actinopterygii: Perciformes: Istiophoridae) in the North-eastern Indian Ocean

The present study aimed to determine the abundance index of blue marlin, Makaira nigricans (Lacepède, 1802) utilizing fishery-independent data, i.e., scientific observer, and attempted to bridge the research's gap for low coverage information in the north eastern Indian Ocean. A total of 2,984 set-by-set observer data from 2006-2018, spatially disaggregated by one-degree blocks, were obtained from the Indonesian scientific observer program following commercial longline fleets. A delta-lognormal model was chosen to fit the dataset, using catch as the response variable with seven covariates. A backward procedure based on AIC, BIC and R2 were used to select the best model. Overall, the delta-Gamma performs better when modelling data with a high proportion of zeros than other traditional models. The blue marlin CPUE trend is relatively stable over time, despite the inter-annual fluctuations, which are likely a result of natural variation in the population as opposed to operational changes or inter-annual environmental variation. Given the low spatial coverage compared to logbook data, scientific observer data performed well and produced a robust abundance index of blue marlin in the northeastern Indian Ocean.

Where do the billfish go? Using recreational catch data to relate local and basin scale environmental conditions to billfish occurrence in the Eastern Tropical Pacific

AbstractRecreational fisheries in the Eastern Tropical Pacific (ETP) have increased in popularity since the 1970s, contributing to the eco‐tourism industries of many Central American economies. However, pelagic gamefish face several direct and indirect threats which can affect population health and sustainability. We use daily catch logs from three recreational fishing lodges in Guatemala, Costa Rica, and Panama as records of change in blue marlin (Makaira nigricans) and sailfish (Istiophorus platypterus) sightings per unit effort (SPUE) between 2010 and 2019. Using cross‐correlational analysis, we compared billfish SPUE to the El Niño Southern Oscillation (ENSO) Index and local oceanographic conditions (sea surface temperature [SST] and chlorophyll [chl a]) to understand how billfish availability to recreational fishers is related to environmental conditions at different time lags. Blue marlin occurrence was negatively correlated with the ENSO at time lags of 9–22 months in Guatemala and Costa Rica, while sailfish occurrence was positively correlated with ENSO at time lags of 5–10 months in all three regions. Cross‐correlations with local SST were similar to ENSO patterns; however, results were unclear and nonsignificant for local chl a. By comparing recreational fisher SPUE to reported catch per unit effort (CPUE) of these two species by the international longline and purse seine fisheries, we show possible offshore movement of fish stocks during the 2016 warming event. Recreational fishing records provide an alternative way to monitor the occurrence of targeted fish species. By determining correlations of these species to environmental conditions, we begin to distinguish the effects of natural variability in the environment, from direct anthropogenic impacts.