Istiophorus Platypterus Research Articles

Sailfish generate foraging opportunities for seabirds in multi-species predator aggregations.

While various marine predators form associations, the most commonly studied are those between subsurface predators and seabirds, with gulls, shearwaters or terns frequently co-occurring with dolphins, billfish or tuna. However, the mechanisms underlying these associations remain poorly understood. Three hypotheses have been proposed to explain the prevalence of these associations: (1) subsurface predators herd prey to the surface and make prey accessible to birds, (2) subsurface predators damage prey close to the surface and thereby provide food scraps to birds, and (3) attacks of underwater predators lower the cohesion of prey groups and thereby their collective defences making the prey easier to be captured by birds. Using drone footage, we investigated the interaction between Indo-Pacific sailfish (Istiophorus platypterus) and terns (Onychoprion sp.) preying on schooling fish off the eastern coast of the Malaysian peninsula. Through spatio-temporal analysis of the hunting behaviour of the two predatory species and direct measures of prey cohesion we showed that terns attacked when school cohesion was low, and that this decrease in cohesion was frequently caused by sailfish attacks. Therefore, we propose that sailfish created a by-product benefit for the bird species, lending support to the hypothesis that lowering cohesion can facilitate associations between subsurface predators and seabirds.

Parasitism of Pennella instructa on indo-pacific sailfish Istiophorus platypterus and its commensality relation with goose barnacle, Conchoderma virgatum along Eastern Arabian Sea

Parasitism of Pennella instructa on indo-pacific sailfish Istiophorus platypterus and its commensality relation with goose barnacle, Conchoderma virgatum along Eastern Arabian Sea

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.

Hunting behavior of a solitary sailfish Istiophorus platypterus and estimated energy gain after prey capture

Foraging behavior and interaction with prey is an integral component of the ecological niche of predators but is inherently difficult to observe for highly mobile animals in the marine environment. Billfishes have been described as energy speculators, expending a large amount of energy foraging, expecting to offset high costs with periodic high energetic gain. Surface-based group feeding of sailfish, Istiophorus platypterus, is commonly observed, yet sailfish are believed to be largely solitary roaming predators with high metabolic requirements, suggesting that individual foraging also represents a major component of predator–prey interactions. Here, we use biologging data and video to examine daily activity levels and foraging behavior, estimate metabolic costs, and document a solitary predation event for a 40 kg sailfish. We estimate a median active metabolic rate of 218.9 ± 70.5 mgO2 kg−1 h−1 which increased to 518.8 ± 586.3 mgO2 kg−1 h−1 during prey pursuit. Assuming a successful predation, we estimate a daily net energy gain of 2.4 MJ (5.1 MJ acquired, 2.7 MJ expended), supporting the energy speculator model. While group hunting may be a common activity used by sailfish to acquire energy, our calculations indicate that opportunistic individual foraging events offer a net energy return that contributes to the fitness of these highly mobile predators.

Trends and variability in local abundances of sailfish Istiophorus platypterus in Pacific waters of Costa Rica: Controls and effects on recreational fisheries

Fishing tourism represents a vital industry in Costa Rica, generating over US$520 million and attracting 150,000 tourists every year. The main objective of this study is to examine trends and variability in local abundances of sailfish Istiophorus platypterus, the main sportfish in Pacific waters of Costa Rica, and quantify the influence of environmental and anthropogenic factors. We compiled and analyzed sailfish information collected from sportfishing operations. Sailfish abundances were examined in relation to environmental conditions and commercial fishing. Timeseries analyses showed significant declining trends in local abundances of sailfish in the southern and central Pacific of Costa Rica over the last decade. Bycatch records from the commercial purse seine fleet operating in Costa Rican waters also show a declining trend in sailfish numbers. On the other hand, commercial landings from the national longline fleet show a significant increase of 108%, on average, over the past decade. Different numerical models indicated that fishing pressure from the national fleet and also sea surface temperature with different time lags affect local abundances of sailfish. While other countries in Central and North America protect sailfish and other species of tourist interest, Costa Rica still allows the landing and sales of billfishes as seafood. The results presented in this study highlight the need to allow for the recovery of local abundances of sailfish and promote the development of the coastal communities that depend on marine tourism as their main source of income.

Osteocranium of the Sailfish (Istiophorus platypterus, Shaw & Nodder, 1792) from Malacca Strait

The features and morphometrics of the sailfish's osteocranium are examined in this study (Istiophorus platypterus, Shaw & Nodder, 1792). I. platypterus has a total weight of ±20 kg with a total length of ±218 cm. The stages of the research process included preparing samples, preparing osteocraniums, documenting photos, editing images, and identifying terminology related to osteocraniums. The Laboratory of Mathematics and Natural Sciences at Almuslim University handled every aspect of the research. The osteocranium preparation process was carried out physically and chemically. Each bone was documented using a camera and edited using Adobe Photoshop CS6. The neurocranium is divided into four components: the olfactory (ethmoidal), which comprises 6 bones. The orbitale comprises 4 bones, the otic comprises 5, and the occipital comprises 4 bones. The branchiocranium is divided into five components: the oromandibular structure consisting of 3 bones, the mandibular arc (suspensorium) composed of 4 bones, the opercular apparatus consisting of 4 bones, and the hyoid arc composed of 6 bones, and the branchial arc composed of 4 bones.

Quantifying Catch Rates, Shark Abundance and Depredation Rate at a Spearfishing Competition on the Great Barrier Reef, Australia.

Simple SummaryCatch-per-unit-effort at a spearfishing competition in North Queensland, Australia was 1.25 fish per hour. Citizen scientists reported 358 sharks comprising of 10 species/groups, with 3.11 sharks observed per hour. Twelve percent of all sharks sighted in this study were regarded as potentially dangerous to humans. This is the first scientific study of shark depredation for spearfishing. C. amblyrhynchos were primarily responsible for depredation, with 5.9% of speared fish taken. Sixty percent of interviewees perceived that shark numbers have increased in the past 10 years.We developed and applied a method to quantify spearfisher effort and catch, shark interactions and shark depredation in a boat-based recreational spearfishing competition in the Great Barrier Reef Marine Park in Queensland. Survey questions were designed to collect targeted quantitative data whilst minimising the survey burden of spearfishers. We provide the first known scientific study of shark depredation during a recreational spearfishing competition and the first scientific study of shark depredation in the Great Barrier Reef region. During the two-day spearfishing competition, nine vessels with a total of 33 spearfishers reported a catch of 144 fish for 115 h of effort (1.25 fish per hour). A subset of the catch comprised nine eligible species under competition rules, of which 47 pelagic fish were weighed. The largest fish captured was a 34.4 kg Sailfish (Istiophorus platypterus). The most common species captured and weighed was Spanish Mackerel (Scomberomorus commerson). The total weight of eligible fish was 332 kg and the average weight of each fish was 7.1 kg. During the two-day event, spearfishers functioned as citizen scientists and counted 358 sharks (115 h effort), averaging 3.11 sharks per hour. Grey Reef Sharks (Carcharhinus amblyrhynchos) comprised 64% of sightings. Nine speared fish were fully depredated by sharks as spearfishers attempted to retrieve their catch, which equates to a depredation rate of 5.9%. The depredated fish included four pelagic fish and five reef fish. The shark species responsible were Grey Reef Shark (C. amblyrhynchos) (66%), Bull Shark (Carcharhinus leucas) (11%), Whitetip Reef Shark (Triaenodon obesus) (11%) and Great Hammerhead (Sphyrna mokarran) (11%). There were spatial differences in fish catch, shark sightings and rates of depredation. We developed a report card that compared average catch of fish, sightings of sharks per hour and depredation rate by survey area, which assists recreational fishers and marine park managers to assess spatio-temporal changes. The participating spearfishers can be regarded as experienced (average 18 days a year for average 13.4 years). Sixty percent of interviewees perceived that shark numbers have increased in the past 10 years, 33% indicated no change and 7% indicated shark numbers had decreased. Total fuel use of all vessels was 2819 L and was equivalent to 6.48 tons of greenhouse gas emissions for the competition.

Assessment of the Impact on 20 Pelagic Fish Species by the Taiwanese Small-Scale Longline Fishery in the Western North Pacific Using Ecological Risk Assessment.

Simple SummaryIn this study, a semi-quantitative ecological risk assessment (ERA) was used to evaluate the ecological risks of fishing impact on 20 pelagic fish species by the small-scale longline fisheries in the western North Pacific Ocean. More than 2.38 million individual landing records at Nangfangao and Hsinkang fishing ports, eastern Taiwan from 2001–2021 were used in this study. The productivity was estimated based on the mean ranking (high, median, and low) of seven life history parameters and the susceptibility was calculated by the multiplication of the catchability, selectivity and post-capture mortality. The ERA results indicated sharks have higher ecological risk than those of tunas and billfishes, except yellowfin tuna (Thunnus albacares). The shortfin mako shark (Isurus oxyrinchus) and dusky shark (Carcharhinus obscurus) have the highest risk. Yellowfin tuna, other shark species, and sailfish (Istiophorus platypterus) have medium risk. While the striped marlin (Kajikia audax), and albacore tuna (T. alalunga) have the lowest risk. Although ERA cannot replace the conventional stock assessment methods that can produce solid management information on catch and effort, yet it can provide useful information for precautionary management measures.Ecological risk assessment (ERA) has been applied on assessing the relative risk of bycatch species in recent years. ERA index is calculated by productivity of species and susceptibility of fisheries on fish species. In this study, a semi-quantitative method was used to evaluate the risks of exploitation for 20 pelagic fish species by the small-scale longline fisheries in the western North Pacific Ocean. The productivity was estimated based on the ranking (high, median, and low) of seven life history parameters. The susceptibility was calculated by the multiplication of the catchability, selectivity and post-capture mortality. The ERA results indicated the risks of sharks are higher than those of tunas and billfishes, except yellowfin tuna (Thunnus albacares). The shortfin mako shark (Isurus oxyrinchus) and dusky shark (Carcharhinus obscurus) have the highest risk. Other shark species, yellowfin tuna, and sailfish (Istiophorus platypterus) have medium risk. While the striped marlin (Kajikia audax), and albacore tuna (T. alalunga) have the lowest risk. Stock assessment and rigorous management measures such as catch quota and size limit are recommended for the species in high or medium ecological risk and a consistent monitoring management scheme is suggested for those in low ecological risk.

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.

Habitat suitability of Indo-Pacific sailfish Istiophorus platypterus (Shaw, 1792) in the Arabian Sea

Istiophorus platypterus (Shaw, 1792) is the most common billfish species in the Arabian Sea and contributes more than 50% of the total billfish landings in India. The abundance of I. platypterus was more off Maharashtra and Gujarat in the northern Arabian Sea and in Lakshadweep islands with higher catches during March, April and December. The aim of the study was to predict the suitable habitat of occurrence and potential fishing ground of I. platypterus by correlating the spatial catch rates with environmental parameters along the Arabian Sea. Generalised Additive Modelling (GAM) showed significant relationship between the catch and the predictor variables [sea surface salinity (SSS), sea surface temperature (SST), sea surface height anomaly (SSHa), current speed (CS) and chlorophyll (Chl)]. SSS from 32 to 36 ppt had a positive effect on the expected abundance. Similarly, SST showed a positive effect from 25 to 28°C and thereafter had a negative effect on catch rate. The highest catch values associated with the SSHa was >0.4 m and partial effect of SSHa on catch was negative below 0.4 m. Current speed higher than 0.4 m s-1 showed negative effects on catch rate and lower Chl-a values which ranged between 0.04-2.14 mg m-3 in the study area showed a positive effect. All explanatory variables (SST, SSHa, CS, Chl) except SSS were found to be highly significant covariates (p<0.01, p<0.01, p<0.001 and p<0.05 respectively) and 38.2% of variance was explained by the model with these variables. The paper discusses the fishery and trend of billfishlandings along the Indian coast in relation to various remotely sensed data and defines the optimum habitat suitability for I. platypterus. Keywords: Additive models, GAMs, Large pelagics, Northern Indian Ocean

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.

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.

Biomimetics Design Optimization and Drag Reduction Analysis for Indonesia N219 Seaplanes Catamaran Float

Design optimization on the Indonesia N219 seaplane catamaran is necessary to provide better service to rural islands of Indonesia. This research aims at decreasing drag using a design based on biomimicry by imitating the hydrodynamic characteristics of sailfish (Istiophorus platypterus) for pontoon floats. The design is then validated using a numerical fluid test using ANSYS Fluent to see the reduction in drag due to the change from a conventional or Wipeline® 13000 design to a biomimetics adaptation design. Next, further optimization was carried out based on the adaptation design based on trim tests, clearance tests, and deadrise angle dimensions suitable for biomimicry designs at Froude number speeds of 0.4 to 0.7. The design results with the adaptation of biomimicry show that a change in the design with this optimization affects a drag reduction that reaches 30% of the total drag generated by the conventional design.

Global phylogeography of sailfish: deep evolutionary lineages with implications for fisheries management

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.

BILLFISH CATCHES FROM OCEANIC RECREATIONAL FISHING IN THE ROYAL CHARLOTTE BANK, BAHIA, BRAZIL

The aim of this study was to analyze the oceanic recreational fishing in the Royal Charlotte Bank, state of Bahia, Brazil. Only data from an oceanic recreational fishing operator based in the municipality of Canavieiras, southern Bahia, were used, from 2012 to 2017. Overall, 103 fish specimens were caught and released, during this period, belonging to the following species: Makaira nigricans, Kajikia albida, and Istiophorus platypterus. Fishery operations occurred from October to March, with the highest catch in number in December (56.3%). The largest annual catch was recorded in 2013, with 39 individuals. The catch per unit effort ranged from 1.0 to 1.4 fishes per trip, with the highest value in December. Even though data presented here are partial, they can help to establish a strategic scenario for the fishing sector in Bahia, along with data from other fishing sectors (artisanal, industrial, subsistence and scientific).

The complete mitochondrial genome of the Capsaloides cristatus (Platyhelminthes, Monogenea), a pathogen of the sailfish (Istiophorus platypterus)

This study reports the complete mitochondrial genome of the Capsaloides cristatus (Monogenea: Capsalidae) collected from the gill lamella of Istiophorus platypterus. The total length of the mitogenome was 13,948 bp, containing 12 typical platyhelminthic protein-coding genes, 22 tRNA genes, 2 rRNA genes and a putative non-coding region, with the atp8 gene being absent. The total A + T content was 65.99%, which was significantly higher than that of the C + G content (34.01%). There were two kinds of start codons (ATG and GTG) and three kinds of terminated codons (TAA, TAG and TGA) in the 12 protein-coding genes. Phylogentic analysis revealed close relationships among the genera Capsaloides, Capsala, Benedenia and Neobenedenia with high bootstrap value supported. This study will provide useful molecular data for a better understanding of the species identification and phylogenetic position of C. cristatus.