Brief Oil Exposure Reduces Fitness in Wild Gulf of Mexico Mahi-Mahi (Coryphaena hippurus).

The Deepwater Horizon (DWH) disaster released 3.19 million barrels of crude oil into the Gulf of Mexico (GOM) in 2010, overlapping the habitat of pelagic fish populations. Using mahi-mahi (Coryphaena hippurus)─a highly migratory marine teleost present in the GOM during the spill─as a model species, laboratory experiments demonstrate injuries to physiology and behavior following oil exposure. However, more than a decade postspill, impacts on wild populations remain unknown. To address this gap, we exposed wild mahi-mahi to crude oil or control conditions onboard a research vessel, collected fin clip samples, and tagged them with electronic tags prior to release into the GOM. We demonstrate profound effects on survival and reproduction in the wild. In addition to significant changes in gene expression profiles and predation mortality, we documented altered acceleration and habitat use in the first 8 days oil-exposed individuals were at liberty as well as a cessation of apparent spawning activity for at least 37 days. These data reveal that even a brief and low-dose exposure to crude oil impairs fitness in wild mahi-mahi. These findings offer new perspectives on the lasting impacts of the DWH blowout and provide insight about the impacts of future deep-sea oil spills.

Enhanced oxygen unloading in two marine percomorph teleosts.

Teleost fishes are diverse and successful, comprising almost half of all extant vertebrate species. It has been suggested that their success as a group is related, in part, to their unique O2 transport system, which includes pH-sensitive hemoglobin, a red blood cell ß-adrenergic Na+/H+ exchanger (RBC ß-NHE) that protects red blood cell pH, and plasma accessible carbonic anhydrase which is absent at the gills but present in some tissues, that short-circuits the ß-NHE to enhance O2 unloading during periods of stress. However, direct support for this has only been examined in a few species of salmonids. Here, we expand the knowledge of this system to two warm-water, highly active marine percomorph fish, cobia (Rachycentron canadum) and mahi-mahi (Coryphaena hippurus). We show evidence for RBC ß-NHE activity in both species, and characterize the Hb-O2 transport system in one of those species, cobia. We found significant RBC swelling following ß-adrenergic stimulation in both species, providing evidence for the presence of a rapid, active RBC ß-NHE in both cobia and mahi-mahi, with a time-course similar to that of salmonids. We generated oxygen equilibrium curves (OECs) for cobia blood and determined the P50, Hill, and Bohr coefficients, and used these data to model the potential for enhanced O2 unloading. We determined that there was potential for up to a 61% increase in O2 unloading associated with RBC ß-NHE short-circuiting, assuming a - 0.2 ∆pHa-v in the blood. Thus, despite phylogenetic and life history differences between cobia and the salmonids, we found few differences between their Hb-O2 transport systems, suggesting conservation of this physiological trait across diverse teleost taxa.

Toxicity of perfluoroalkyl substances (PFAS) toward embryonic stages of mahi-mahi (Coryphaena hippurus).

Perfluoroalkyl substances (PFAS) are highly persistent organic pollutants that have been detected in a wide array of environmental matrices and, in turn, diverse biota including humans and wildlife wherein they have been associated with a multitude of toxic, and otherwise adverse effects, including ecosystem impacts. In the present study, we developed a toxicity assay for embryonic stages of mahi-mahi (Coryphaena hippurus), as an environmentally relevant pelagic fish species, and applied this assay to the evaluation of the toxicity of "legacy" and "next-generation" PFAS including, respectively, perfluorooctanoic acid (PFOA) and several perfluoroethercarboxylic acids (PFECA). Acute embryotoxicity, in the form of lethality, was measured for all five PFAS toward mahi-mahi embryos with median lethal concentrations (LC50) in the micromolar range. Consistent with studies in other similar model systems, and specifically the zebrafish, embryotoxicity in mahi-mahi generally (1) correlated with fluoroalkyl/fluoroether chain length and hydrophobicity, i.e., log P, of PFAS, and thus, aligned with a role of uptake in the relative toxicity; and (2) increased with continuous exposure, suggesting a possible role of development stage specifically including a contribution of hatching (and loss of protective chorion) and/or differentiation of target systems (e.g., liver). Compared to prior studies in the zebrafish embryo model, mahi-mahi was significantly more sensitive to PFAS which may be related to differences in either exposure conditions (e.g., salinity) and uptake, or possibly differential susceptibility of relevant targets, for the two species. Moreover, when considered in the context of the previously reported concentration of PFAS within upper sea surface layers, and co-localization of buoyant eggs (i.e., embryos) and other early development stages (i.e., larvae, juveniles) of pelagic fish species to the sea surface, the observed toxicity potentially aligns with environmentally relevant concentrations in these marine systems. Thus, impacts on ecosystems including, in particular, population recruitment are a possibility. The present study is the first to demonstrate embryotoxicity of PFAS in a pelagic marine fish species, and suggests that mahi-mahi represents a potentially informative, and moreover, environmentally relevant, ecotoxicological model for PFAS in marine systems.

Mahi-mahi (Coryphaena hippurus) life development: morphological, physiological, behavioral and molecular phenotypes.

BACKGROUND: Mahi-mahi (Coryphaena hippurus) is a commercially and ecologically important fish species that is widely distributed in tropical and subtropical waters. Biological attributes and reproductive capacities of mahi-mahi make it a tractable model for experimental studies. In this study, life development of cultured mahi-mahi from the zygote stage to adult has been described. RESULTS: A comprehensive developmental table has been created reporting development as primarily detailed observations of morphology. Additionally, physiological, behavioral, and molecular landmarks have been described to significantly contribute in the understanding of mahi life development. CONCLUSION: Remarkably, despite the vast difference in adult size, many developmental landmarks of mahi map quite closely onto the development and growth of Zebrafish and other warm-water, active Teleost fishes.

Relationship between trace element concentrations and body length in dolphinfish (Coryphaena hippurus) in the northwest Atlantic Ocean.

Dolphinfish (Coryphaena hippurus) is a popular seafood choice worldwide, however, except for mercury (Hg) and selenium (Se), little is known about the concentration of other trace elements in dolphinfish muscle tissue, especially in the northwest Atlantic Ocean. This study investigated the relationship between body length (61 to 94 cm fork length) and trace element [silver (Ag), arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), Hg, manganese (Mn), nickel (Ni), lead (Pb), Se, and zinc (Zn)] concentrations in muscle tissue of dolphinfish caught off Long Island, New York (n = 16). There was a positive relationship with body length for As and Hg, a negative relationship with body length for Cu and Zn, and no relationship with body length for Cd, Fe, Mn, Pb, and Se. A negative relationship between the Se:Hg molar ratio and body length and Se:Hg molar ratio and Hg concentration was observed. Dolphinfish were low in Hg with only 18.9% (n = 3) of individuals exceeding the U.S. EPA human health criterion of 0.3 µg/g wet weight, making this species a suitable seafood choice to reduce dietary intake of Hg at the investigated body length. All fish had a Se:Hg molar ratio > 1:1 indicating that Se may have a protective effect against Hg toxicity. The selenium health benefit value (HBVSe) for all individuals was > 1, indicating there may be health benefits from consuming dolphinfish.

An integrated systems-level model of the toxicity of brevetoxin based on high-resolution magic-angle spinning nuclear magnetic resonance (HRMAS NMR) metabolic profiling of zebrafish embryos.

Brevetoxins (PbTx) are a well-recognized group of neurotoxins associated with harmful algal blooms, and specifically recurrent "Florida Red Tides," in marine waters that are linked to impacts on both human and ecosystem health including well-documented "fish kills" and marine mammal mortalities in affected coastal waters. Understanding mechanisms and pathways of PbTx toxicity enables identification of relevant biomarkers to better understand these environmental impacts, and improve monitoring efforts, in relation to this toxin. Toward a systems-level understanding of toxicity, and identification of potential biomarkers, high-resolution magic angle spinning nuclear magnetic resonance (HRMAS NMR) was utilized for metabolic profiling of zebrafish (Danio rerio) embryos, as an established toxicological model, exposed to PbTx-2 (the most common congener in marine waters). Metabolomics studies were, furthermore, complemented by an assessment of the toxicity of PbTx-2 in embryonic stages of zebrafish and mahi-mahi (Coryphaena hippurus), the latter representing an ecologically and geographically relevant marine species of fish, which identified acute embryotoxicity at environmentally relevant (i.e., parts-per-billion) concentrations in both species. HRMAS NMR analysis of intact zebrafish embryos exposed to sub-lethal concentrations of PbTx-2 afforded well-resolved spectra, and in turn, identification of 38 metabolites of which 28 were found to be significantly altered, relative to controls. Metabolites altered by PbTx-2 exposure specifically included those associated with (1) neuronal excitotoxicity, as well as associated neural homeostasis, and (2) interrelated pathways of carbohydrate and energy metabolism. Metabolomics studies, thereby, enabled a systems-level model of PbTx toxicity which integrated multiple metabolic, molecular and cellular pathways, in relation to environmentally relevant concentrations of the toxin, providing insight to not only targets and mechanisms, but potential biomarkers pertinent to environmental risk assessment and monitoring strategies.

Embryonic buoyancy control as a mechanism of ultraviolet radiation avoidance.

Pelagic fish have long been presumed to produce buoyant embryos which float and hatch at or near surface waters. Due to their transparency and rapid development, mahi embryos are thought to be especially vulnerable to stressors occurring in surface waters, such as ultraviolet radiation (UVR) and increased temperatures. In the present study, we suggest a possibly critical mechanism of UVR avoidance by pelagic fish embryos. Specifically, we provide evidence that mahi embryos are able to sense UVR and may alter buoyancy as a means of reducing exposure to the most harmful stressors occurring in the upper layers of the water column. Further, once the UVR exposure was terminated, embryos displayed fast recovery of positive buoyancy indicating this response is rapidly dynamic and not pathological. The mechanism behind buoyancy control is not known, but evidence from the current study suggests that ammonia sequestration, as seen in multiple other fish species, is not the primary control mechanism employed by embryonic mahi. Finally, expression of antioxidant and UV repair enzymes were investigated to elucidate possible involvement in observed buoyancy changes and to explore alternative methods of repairing UVR damage.

Deepwater Horizon crude oil exposure alters cholesterol biosynthesis with implications for developmental cardiotoxicity in larval mahi-mahi (Coryphaena hippurus).

During the spring and summer of 2010, the Deepwater Horizon (DWH) oil well released over three million barrels of crude oil into the Gulf of Mexico. As the oil dispersed it contaminated ecosystems that support numerous Gulf species including mahi-mahi (Coryphaena hippurus). The timing of the spill, and location of the surface slick, coincided with the spawning of many species in the region, raising concerns over embryonic and larval exposure. Numerous abnormalities due to crude oil exposure have been documented in fish early life stages, including cardiotoxicity; however, knowledge of the molecular mechanisms that cause these phenotypes is still limited. Several transcriptomic studies have presented cholesterol biosynthesis as one of the top enriched pathways following PAH exposure. In this study we exposed mahi-mahi embryos to DWH oil collected from the surface slick. At exposures ranging from ∑PAH 1.69 µg/L to ∑PAH 5.99 µg/L, the resulting larvae demonstrated significant increases in farnesyl-diphosphate farnesyltransferase 1 (fdft1) and an upward trend in 3-Hydroxy-3-Methylglutaryl-CoA Reductase (hmgcr) expression, genes that encode key enzymes in the cholesterol biosynthetic pathway. In addition to the increased expression of genes in cholesterol biosynthetic pathway, a significant decrease in total cholesterol was observed in larval homogenates, at ∑PAH 8.3 µg/L. These data confirm earlier transcriptomic studies and show that oil may diminish cholesterol and adversely impact numerous cellular functions due to altered membrane stability.

Collagen Peptide Upregulates Osteoblastogenesis from Bone Marrow Mesenchymal Stem Cells through MAPK- Runx2.

Collagen is the most abundant extracellular fibrous protein that has been widely used for biomedical applications due to its excellent biochemical and biocompatibility features. It is believed that the smaller molecular weight collagen, i.e., collagen peptide (CP), has more potent activity than native collagen. However, the preparation of CP from fish bone collagen is a complex and time-consuming process. Additionally, the osteogenic effect of CP depends on its molecular weight and amino acid composition. Considering the above concept, the present work was undertaken to extract the CP directly from Mahi mahi fish (Coryphaena hippurus) bones and test its osteogenic potential using bone marrow mesenchymal stem (BMMS) cells. The hydrolyzed collagen contained triple alpha chains (110 kDa) and a peptide (~1 kDa) and the peptide was successfully separated from hydrolyzed collagen using molecular weight cut-off membrane. CP treatment was up-regulated BMMS cells proliferation and differentiation. Interestingly, CP accrued the mineral deposition in differentiated BMMS cells. Protein and mRNA expression revealed that the osteogenic biomarkers such as collagen, alkaline phosphatase, and osteocalcin levels were significantly increased by CP treatment in differentiated BMMS cells and also further elucidated the hypothesis that CP was upregulated osteogenesis through activating Runx2 via p38MAPK signaling pathway. The above results concluded that the CP from Mahi mahi bones with excellent osteogenic properties could be the suitable biomaterial for bone therapeutic application.

Morphology and cardiac physiology are differentially affected by temperature in developing larvae of the marine fish mahi-mahi (Coryphaena hippurus).

Cardiovascular performance is altered by temperature in larval fishes, but how acute versus chronic temperature exposures independently affect cardiac morphology and physiology in the growing larva is poorly understood. Consequently, we investigated the influence of water temperature on cardiac plasticity in developing mahi-mahi. Morphological (e.g. standard length, heart angle) and physiological cardiac variables (e.g. heart rate fH, stroke volume, cardiac output) were recorded under two conditions by imaging: (i) under acute temperature exposure where embryos were reared at 25°C up to 128 h post-fertilization (hpf) and then acutely exposed to 25 (rearing temperature), 27 and 30°C; and (ii) at two rearing (chronic) temperatures of 26 and 30°C and performed at 32 and 56 hpf. Chronic elevated temperature improved developmental time in mahi-mahi. Heart rates were 1.2-1.4-fold higher under exposure of elevated acute temperatures across development (Q10≥2.0). Q10 for heart rate in acute exposure was 1.8-fold higher compared to chronic exposure at 56 hpf. At same stage, stroke volume was temperature independent (Q10∼1.0). However, larvae displayed higher stroke volume later in stage. Cardiac output in developing mahi-mahi is mainly dictated by chronotropic rather than inotropic modulation, is differentially affected by temperature during development and is not linked to metabolic changes.

Assessment of early life stage mahi-mahi windows of sensitivity during acute exposures to Deepwater Horizon crude oil.

Windows of exposure to a weathered Deepwater Horizon oil sample (slick A) were examined for early life stage mahi-mahi (Coryphaena hippurus) to determine whether there are developmental periods of enhanced sensitivity during the course of a standard 96-h bioassay. Survival was assessed at 96 h following oil exposures ranging from 2 h to 96 h and targeting 3 general periods of development, namely the prehatch phase, the period surrounding hatch, and the posthatch phase. In addition, 3 different oil preparations were used: high- and low-energy water accommodated fractions of oil and very thin surface slicks of oil (∼1 µm). The latter 2 were used to distinguish between effects due to direct contact with the slick itself and the water underlying the slick. Considering the data from all 3 exposure regimes, it was determined that the period near or including hatch was likely the most sensitive. Furthermore, toxicity was not enhanced by direct contact with slick oil. These findings are environmentally relevant given that the concentrations of polycyclic aromatic hydrocarbons eliciting mortality from exposures during the sensitive periods of development were below or near concentrations measured during the active spill phase. Environ Toxicol Chem 2017;36:1887-1895. © 2016 SETAC.

Heart Performance Determination by Visualization in Larval Fishes: Influence of Alternative Models for Heart Shape and Volume.

Understanding cardiac function in developing larval fishes is crucial for assessing their physiological condition and overall health. Cardiac output measurements in transparent fish larvae and other vertebrates have long been made by analyzing videos of the beating heart, and modeling this structure using a conventional simple prolate spheroid shape model. However, the larval fish heart changes shape during early development and subsequent maturation, but no consideration has been made of the effect of different heart geometries on cardiac output estimation. The present study assessed the validity of three different heart models (the "standard" prolate spheroid model as well as a cylinder and cone tip + cylinder model) applied to digital images of complete cardiac cycles in larval mahi-mahi and red drum. The inherent error of each model was determined to allow for more precise calculation of stroke volume and cardiac output. The conventional prolate spheroid and cone tip + cylinder models yielded significantly different stroke volume values at 56 hpf in red drum and from 56 to 104 hpf in mahi. End-diastolic and stroke volumes modeled by just a simple cylinder shape were 30-50% higher compared to the conventional prolate spheroid. However, when these values of stroke volume multiplied by heart rate to calculate cardiac output, no significant differences between models emerged because of considerable variability in heart rate. Essentially, the conventional prolate spheroid shape model provides the simplest measurement with lowest variability of stroke volume and cardiac output. However, assessment of heart function-especially if stroke volume is the focus of the study-should consider larval heart shape, with different models being applied on a species-by-species and developmental stage-by-stage basis for best estimation of cardiac output.

Histamine production by Raoultella ornithinolytica in mahi-mahi meat at various storage temperatures.

Mahi-mahi meat was inoculated with Raoultella ornithinolytica at 5.0 log CFU/g and stored at -20°C, 4°C, 15°C, 25°C, or 37°C to investigate bacterial growth and formation of total volatile base nitrogen and histamine in mahi-mahi meat. R. ornithinolytica grew rapidly in samples stored at temperature above 15°C. The histamine contents quickly increased to higher than 50 mg/100 g in samples stored at 25°C and 37°C within 12 hours as well as those stored at 15°C within 48 hours. The total volatile base nitrogen contents increased to higher than the index level (30 mg/100 g) for fish decomposition at 25°C within 48 hours and 37°C within 24 hours. However, bacterial growth and histamine formation were controlled by cold storage of the samples at 4°C or below. Once the frozen mahi-mahi samples stored at -20°C for 2 months were thawed and stored at 25°C after 24 hours, histamine started to accumulate rapidly (>50 mg/100 g of fish).

A novel system for embryo-larval toxicity testing of pelagic fish: Applications for impact assessment of Deepwater Horizon crude oil.

Key differences in the developmental process of pelagic fish embryos, in comparison to embryos of standard test fish species, present challenges to obtaining sufficient control survival needed to successfully perform traditional toxicity testing bioassays. Many of these challenges relate to the change in buoyancy, from positive to negative, of pelagic fish embryos that occurs just prior to hatch. A novel exposure system, the pelagic embryo-larval exposure chamber (PELEC), has been developed to conduct successful bioassays on the early life stages (ELSs; embryos/larvae) of pelagic fish. Using this unique recirculating upwelling system, it was possible to significantly improve control survival in pelagic fish ELS bioassays compared to commonly used static exposure methods. Results demonstrate that control performance of mahi-mahi (Coryphaena hippurus) embryos in the PELEC system, measured as percent survival after 96-hrs, significantly outperformed agitated static exposure and static exposure systems. Similar significant improvements in 72-hr control survival were obtained with yellowfin tuna (Thunnus albacares). The PELEC system was subsequently used to test the effects of photo-induced toxicity of crude oil to mahi-mahi ELSs over the course of 96-hrs. Results indicate a greater than 9-fold increase in toxicity of Deepwater Horizon (DWH) crude oil during co-exposure to ambient sunlight compared to filtered ambient sunlight, revealing the importance of including natural sunlight in 96-hr DWH crude oil bioassays as well as the PELEC system's potential application in ecotoxicological assessments.

Captura, esfuerzo y captura incidental de la pesca con espinel en el centro de Perú

El objetivo del presente trabajo es dar a conocer algunas características de los viajes de pesca, esfuerzo, captura, peces objetivos, áreas de pesca y captura incidental obtenida a partir de observadores a bordo y bitácoras de pesca. El 85% de los lances se produjeron en los primeros 574 Km de distancia a la costa (309 millas náuticas). El lance más distante estuvo a 1320 Km (712 millas náuticas). Se lanzaron 382000 anzuelos para perico, en 224 lances y 29 viajes de pesca, 94.6% de la captura en peso fue de perico, 2.7% de tiburón azul (Prionace glauca) y 1.3% de diamante (Isurus oxyrinchus). Además, 103790 anzuelos capturaron tiburón, en 109 lances y 12 viajes de pesca, 81,9% de la captura en peso fue de tiburón azul y 16.8% de diamante. La Captura por Unidad de Esfuerzo (CPUE) para perico mostró diferencias significativas entre estaciones, con un máximo entre noviembre y enero. En lo que refiere a tiburón, la CPUE por estaciones también mostró diferencias significativas, los meses con mayores capturas fueron setiembre y octubre. La tortuga verde, Chelonia mydas agassizii, fue la más capturada y dos de cada tres fueron juveniles. Todas las tortugas cabezonas, Caretta caretta, fueron juveniles. Se reporta la captura de un petrel y al parecer, la captura de mamíferos sería escasa. Considerando el gran esfuerzo de esta pesquería, existe la necesidad de monitorearla para contar con información que permita establecer las correspondientes medidas de manejo.

The aims of this study is to report some characteristics of fishing trips, effort, catches, fishing areas and bycatch through observations on board and logbooks. 85% of sets were in the first 574 Km of distance from the coast (309 nautical miles). Farthest set was located at 1320 Km (712 nautical miles). A total of 382000 hooks were used to catch Mahi mahi, in 224 sets and 29 fishing trips, 94.6% of catch was Mahi mahi, 2.7% blue shark (Prionace glauca) y 1,3% mako shark (Isurus oxyrinchus). Also, 103790 hooks were used to catch sharks, in 109 sets y 12 trips, 81.9% of catch was blue sharks and 16.8% mako sharks. Catch per Unit of Effort (CPUE) for Mahi mahi shows significative difference among seasons; with a peak from November to January. CPUE for shark shows significative difference among seasons, with peaks in September and October. The Green turtle Chelonia mydas agassizii was the most caugth species and two of three were juveniles. All Loggerhead turtles, Caretta caretta, caught were juveniles. A petrel is reported as bycatch and, probably, mammal bycatch is scarce. Considering the huge effort of this fishery, it is important to monitor it and establish management actions.

Variabilidad en la abundancia relativa, estructura por tallas y proporción de sexos del dorado Coryphaena hippurus (Pisces: Coryphaenidae) en el Golfo de Tehuantepec, México / Variability in the relative abundance, size structure and sex ratio of the dolphinfish Coryphaena hippurus (Pisces: Coryphaenidae) in the Gulf of Tehuantepec, México

The dolphinfish (Coryphaena hippurus), is an oceanic epipelagic fish found worldwide in tropical and subtropical waters, with a high dispersal capability via large-scale migrations. This fast-swimming top-level predator is abundant in the Gulf of Tehuantepec, where it is caught incidentally by artisanal fisheries, and represents a target species for both recreational and commercial fisheries in Mexico, Ecuador, Peru and Central America. Nowadays, local fishery information on this species is scarce, thus our objective was to analyze the size structure by sex and the catch-per-unit-effort (CPUE) tendency of dolphinfish caught in the Gulf of Tehuantepec, from 2000 to 2007. For this, fishery catches information was obtained from the artisanal fleet, at six landing sites in the Gulf, and the sex ratio, fork length (FL) and the catch per unit effort (CPUE) were estimated. From all sampling sites, a total of 3 494 females, and 3 877 males were obtained, and dolphinfish size as fork length (FL) ranged from 20.5 to 152cm. Fish size ranged from 25.5 to 148cm furcal length (FL) in males, and 20.5 to 129cm FL in females. The sex ratio (males:females) was 1:1, except in April-May (1:1.5, p<0.05) and November (1:0.5, p<0.05). The sex ratio at different size classes showed a significant bias towards females at smaller sizes (<75cm FL), whereas the males were predominant in larger size classes (>100cm FL). The size structure was bimodal, with a variation in the size average; the modes were defined as the small group (FL=50-55cm) and the large size group (FL=100-110cm). The CPUE showed seasonal changes: values were high for the November-December period, and values were lower for July-August. The seasonal and inter annual variation in the abundance of dolphinfish is probably related to a pre-spawning migration in close relation to the rain-drought regime characteristic of the region, and the associated wind upwelling season of “Tehuanos” in the Gulf of Tehuantepec. Rev. Biol. Trop. 62 (2): 611-626. Epub 2014 June 01.

El dorado Coryphaena hippurus es un depredador oceánico epipelágico que se distribuye en aguas tropicales y subtropicales de todos los océanos. Son peces con alta capacidad de dispersión por su migración a gran escala. El Golfo de Tehuantepec es una de las áreas de mayor abundancia de C. hippurus, donde se registran capturas incidentales en la pesca artesanal y sostiene pesquerías recreacionales y comerciales de pequeña escala en México, Ecuador, Perú y Centroamérica. Aquí se analizan los cambios inter-anuales en la estructura de tallas por sexo del dorado durante 2000-2007, así como la tendencia de la captura por unidad de esfuerzo (CPUE) de dorado efectuada por la flota ribereña. Los resultados están basados en 3 494 hembras y 3 877 machos capturados por pesca artesanal en 6 localidades del Pacífico Sur provenientes de muestreos mensuales. Se estimó la CPUE a partir del número de organismos capturados por viaje de pesca. Los machos pre- sentaron tallas entre 25.5 a 148cm de longitud furcal (Lf), mientras que en hembras las tallas registradas fueron de 20.5 a 129cm Lf. La proporción de sexos mostró patrones estacionales a lo largo del año y diferencias con respecto de Lf, a tallas pequeñas predominaron las hembras (<75cm FL) y a tallas grandes los machos (>100cm Lf). La estructura de Lf mostró una tendencia bimodal, con una variación en la Lf promedio de 2000 a 2007; las modas estuvieron definidas como el grupo de tamaño pequeño (Lf=50-55cm) y el grupo de tamaño grande (Lf=100 a 110cm). La CPUE tuvo cambios estacionales: los periodos más altos se registraron en noviembre-diciembre y mayo; los más bajos en julio-agosto. La variación estacional e interanual en la abundancia del dorado probablemente se encuentre relacionada con una migración pre desove, en estrecha relación con el régimen lluvias-estiaje característico de la región, y la temporada de surgencias eólicas asociadas a la temporada de “Tehuanos” en el Golfo de Tehuantepec.