Tarpon Megalops Atlanticus Research Articles

Characterizing Juvenile Common Snook and Tarpon Habitat to Guide Conservation and Restoration of Coastal Wetlands

To conserve or restore juvenile fish habitat, resource managers, restoration practitioners, and engineers need fine-scale information to understand what conditions they need to preserve or what specifications are needed to create new habitat. The objective of this study was to develop statistical models using a dataset of 18 coastal ponds in Southwest Florida, USA, to predict the abundance of juvenile common snook Centropomus undecimalis (hereafter snook) and presence of juvenile tarpon Megalops atlanticus, both of which are flagship species used for conservation and restoration of subtropical and tropical wetlands. Model predictors included water conditions and characteristics of vegetation, sediment, and geographic position. Modeling results indicated that juvenile snook used coastal ponds that were directly connected to tidal creeks. In contrast, juvenile tarpon were more likely to be present in coastal ponds that were separated from tidal creeks by dense mangrove forest (e.g., elevation > 0.48 m above Mean Low Water) characterized by highly organic sediment and low dissolved oxygen, to which tarpon are well adapted. Overlap between snook abundance and tarpon presence was greatest where connections between ponds and the nearest tidal creek were at a relatively low elevation (e.g., -0.12 m relative to Mean Low Water). Although these findings are most applicable to management and conservation of populations in areas along the Gulf coast of Florida (i.e., in areas of similar tidal range and coastal geomorphology), incorporating more detailed habitat surveys to better capture landscape context, geomorphology, and connectivity into fish sampling designs should be broadly applicable to estuarine fish ecology.

Emigration of Juvenile Tarpon Megalops atlanticus from Ephemerally Connected Coastal Ponds

Worldwide, coastal wetlands are threatened by disrupted hydrology, urbanization, and sea-level rise. In southwest Florida, coastal wetlands include tidal creeks and coastal ponds, which are the primary habitats used by juvenile Tarpon, Megalops atlanticus, an important sport fish. Coastal ponds can occur near uplands and are ephemerally connected to the open estuary, creating conditions of variable dissolved oxygen and salinity. Juveniles can tolerate wide-ranging abiotic conditions, but little is known about how they egress from their remote nursery habitats, which often requires them to cross > 1 km of mangrove forest to reach the open estuary. The objective of this study was to (1) compare Tarpon body condition among ponds close to the open estuary versus those ponds farther away on the Cape Haze peninsula of Charlotte Harbor, Florida, and (2) using acoustic telemetry determine what factors contribute to Tarpon emigration from the ponds to open estuarine waters. We tested the hypothesis that distinct groups of Tarpon occur in isolated ponds, leading to variation in fish length and body condition, and that opportunities for emigration from these ponds hinge on high water events. No pond stood out as having Tarpon of low body condition. Factors contributing to increased probabilities of Tarpon emigration were low barometric pressure, high-water level, and Tarpon body length. Tarpon emigrated from ponds near tidal creeks during summer king tides, while tropical cyclone conditions were needed to allow for movement from ponds farther in the landscape. The juvenile Tarpon were later detected at the mouths of large rivers 30 km up-estuary. The characterizations of water levels and event criteria needed for successful Tarpon nurseries should aid in habitat conservation and the creation of Tarpon nursery habitat in restoration designs.

Diet of age-0 tarpon Megalops atlanticus near their northern range limit in the western Atlantic Ocean

Diet of age-0 tarpon Megalops atlanticus near their northern range limit in the western Atlantic Ocean

Individual variation and repeatability of Atlantic tarpon Megalops atlanticus migrations in the southern US: implications for conservation and management

Individual variation and repeatability of Atlantic tarpon Megalops atlanticus migrations in the southern US: implications for conservation and management

The effects of temperature and salinity on the blood chemistry and survival of juvenile Atlantic tarpon Megalops atlanticus.

Atlantic tarpon Megalops atlanticus are highly migratory sportfish that support recreational fisheries throughout their range. In US waters, juveniles can be found in coastal and estuarine habitats along the Gulf of Mexico and Atlantic seaboard, with temperature limiting their northern latitudinal distribution. Juveniles may overwinter in these areas during the first several years of life. Low temperatures are known to cause mortality in adults, but the challenges of temperature are less understood for juveniles. Furthermore, salinity, which can change dramatically in these habitats, may have a synergistic effect with temperature. To examine the physiological effects of temperature and salinity on juvenile tarpon, wild fish were acclimated to a range of conditions that potentially occur in the northern range of their estuarine habitats. The haematology of juvenile tarpon was examined in two salinity (≤2 and ≥30 ppt) and temperature (15 and 25°C) treatments, followed by a low-temperature tolerance test. After 2 weeks in treatment conditions, blood samples were analysed for haematocrit, pH, red blood cell concentration, haemoglobin content and plasma osmolality. Increased plasma osmolality was observed in fish at low temperature (15°C compared to 25°C) and at high salinity (≥30 ppt compared to ≤2 ppt). Blood pH was increased at 15°C compared to 25°C, with the highest pH at 15°C and low salinity. Haemoglobin, haematocrit and red blood cell concentration were higher at 25°C than 15°C, with haemoglobin lowest at 15°C and low salinity. For the low-temperature tolerance test, all fish were acclimated to 15°C for 2 weeks, then transferred to separate tanks where temperature was gradually decreased at 0.9 ± 0.1°C/h until fish lost equilibrium. Fish at low salinity lost equilibrium more rapidly (1 ppt, 12.65 ± 0.46°C) than fish at high salinity (30 ppt, 11.26 ± 0.14°C). The results indicate juvenile tarpon are susceptible to low temperature, which is exacerbated by low salinity, findings useful in the assessment of juvenile tarpon overwintering habitat.

PERFIL DOS PESCADORES RECREATIVOS NA LAGUNA DA JANSEN, SÃO LUÍS, ESTADO DO MARANHÃO

This study provided to analyze the profile of recreational fishermen who frequent Laguna da Jansen on the island of São Luís - MA, Eastern Amazon, because of the socio-economic importance of the activity as an important source of employment and income. Data were collected from June to August 2020 from semi-structured online interviews applied to the study’s target audience using the “snowball” method. 78 questionnaires were applied, of which 95% were men, aged between 26-35 years (35%), 40% with professional occupation in the private sector, and average monthly salary ranging from 1 to 3 minimum wages (47%). Most of the interviewees use: reel and spinning reels (31%), with artificial baits (54%) and landed fishing (37%). They have the snnoks Centropomus spp. (34%), the tarpon Megalops atlanticus (31%), and the ladyfish Elops saurus (15%) as target species. Recreational fishing in Laguna da Jansen has shown to be very promising, but it needs improvements in the local infrastructure, such as the construction of a fishing pier, kiosks with specific stores for fishing materials, and selling food products, cleaning, public lighting, and treatment of domestic effluents and improving the system for opening and closing the gates, optimizing the flow of water exchange, and minimizing eutrophication due to the accumulation of organic matter and other organic and inorganic compounds.

Juvenile tarpon Megalops atlanticus use of natural and managed marsh habitats in coastal South Carolina

Juvenile tarpon Megalops atlanticus use of natural and managed marsh habitats in coastal South Carolina

Age and growth of early-life-stage Atlantic tarpon (Megalops atlanticus) from the northcentral Gulf of Mexico.

Age and growth of early-life-stage Atlantic tarpon Megalops atlanticus collected from Mississippi coastal waters in the northcentral Gulf of Mexico (GOM) are described using otolith microstructure analysis. Tarpon leptocephali (n= 95, 16.0-27.8 mm standard length, LS ) collected from June throughOctober 2013-2018, ranged in age from 22 to 43 days (mean=30.9± 0.5 days). Leptocephalus somatic growth rates ranged 0.46-1.24 mm day-1 (mean=0.76 ± 0.02 mm day-1 ), and leptocephalus otolith growth rates ranged 1.78-3.97 μm day-1 (mean=2.58 ± 0.04 μm day-1 ). Growth rates were inversely correlated to leptocephalus age, indicating the shrinkage phase associated with leptocephalus metamorphosis. Juvenile tarpon (n= 358, 50-359 mm fork length, LF ) were collected from August through December 2007-2018. Juveniles exhibited a positive allometric relationship (adjusted R2 = 0.99, P< 0.001) between length and mass. The age of 100 juveniles (71-277 mm LF ) ranged from 76 to 174 days. Juvenile growth rate was estimated as 1.56 ± 0.11 mm day-1 . Significant (P< 0.001) linear relationships were found between juvenile age and otolith metrics, including otolith mass (R2 = 0.81) and radius (R2 = 0.68). Evaluation of the backcalculated hatch dates suggests that specimens in the collection hatched from late May through mid-September with slight peaks during July and August. A Rao's Spacing Test of Uniformity indicates the presence of significant lunar periodicity in leptocephalus hatch dates (n= 95, U= 250.1, P< 0.05), with 50% of the leptocephali hatched within 5 days (before or after) of the full moon. This study fills critical gaps in the scientific knowledge of tarpon and provides estimates of early-life-history metrics for an iconic game fish at the northernmost extent of its GOM range.

Regional-scale variability in the movement ecology of marine fishes revealed by an integrative acoustic tracking network

Marine fish movement plays a critical role in ecosystem functioning and is increasingly studied with acoustic telemetry. Traditionally, this research has focused on single species and small spatial scales. However, integrated tracking networks, such as the Integrated Tracking of Aquatic Animals in the Gulf of Mexico (iTAG) network, are building the capacity to monitor multiple species over larger spatial scales. We conducted a synthesis of passive acoustic monitoring data for 29 species (889 transmitters), ranging from large top predators to small consumers, monitored along the west coast of Florida, USA, over 3 yr (2016-2018). Space use was highly variable, with some groups using all monitored areas and others using only the area where they were tagged. The most extensive space use was found for Atlantic tarpon Megalops atlanticus and bull sharks Carcharhinus leucas. Individual detection patterns clustered into 4 groups, ranging from occasionally detected long-distance movers to frequently detected juvenile or adult residents. Synchronized, alongshore, long-distance movements were found for Atlantic tarpon, cobia Rachycentron canadum, and several elasmobranch species. These movements were predominantly northbound in spring and southbound in fall. Detections of top predators were highest in summer, except for nearshore Tampa Bay where the most detections occurred in fall, coinciding with large red drum Sciaenops ocellatus spawning aggregations. We discuss the future of collaborative telemetry research, including current limitations and potential solutions to maximize its impact for understanding movement ecology, conducting ecosystem monitoring, and supporting fisheries management.

Knowledge on the use of catch material for craftwork/handicrafts by an urban fishing community

The present study aimed to investigate knowledge on the use of catch material for craftwork by the members of the fishing community of Brasília Teimosa. Among the 98 artisanal fishermen interviewed, 64.6% demonstrated knowledge on the use of catch material for craftwork, but reported not participating in the creation of such craftwork. The fishermen cited 36 common names, mainly Actinopterigii (53.8%) and Crustacea (29.2%). The most caught species were the queen triggerfish Balistes vetula (13.1%) and the Atlantic tarpon Megalops atlanticus (12.3%). The most cited material was the entire body or taxidermied parts of the body (48.8%), followed by the skin (20.1%) for the fabrication of jewelry and souvenirs. Some catches had more than one raw material cited, such as sharks and the queen triggerfish. The main market pressure on fishing activity in the community of Brasília Teimosa is for food consumption. Catches destined for the production of craftwork are appreciated as a food source or captured incidentally. However, many of the species cited are on national and international conservation priority lists. Thus, regardless of the end use, the exploitation of these fishing resources should be performed with caution to avoid further harm to these populations and not compromise the sustainability of the activity, considering the cultural particularities of the populations that use these resources for subsistence and/or the generation of income.

ESTADO DE CONSERVAÇÃO DO CAMURUPIM Megalops atlanticus (ACTINOPTERYGII: MEGALOPIDAE): UMA REVISÃO SISTEMÁTICA ENTRE 2010 E 2019

O camurupim Megalops atlanticus (Valenciennes, 1847) é amplamente distribuído em águas tropicais e subtropicais. Devido a sua superexplotação, compõe a lista brasileira de espécies ameaçadas. Realizou-se um levantamento bibliográfico para analisar os estudos sobre M. atlanticus procurando identificar as lacunas de conhecimento, bem como propor medidas que auxiliem o processo de conservação dessa espécie. A seleção dos artigos foi através do protocolo Prisma (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). O mecanismo de “busca avançada” foi usado nas bases de dados Science Direct, Google Scholar, Scopus e Scielo, com a palavra-chave “Megalops atlanticus”. As variáveis dos artigos foram divididas em três seções: dinâmica populacional, conservação e exploração. Além disso, foram registrados o local e o habitat de cada estudo. Foram selecionados 25 artigos, a maioria publicada em 2018, distribuídos ao longo do continente americano com apenas um trabalho no território brasileiro. O Brasil não possui monitoramento eficaz da sobrexplotação de M. atlanticus, evidenciando que a implementação de programas de monitoramento é prioritária. Mesmo com vulnerabilidade reconhecida, ainda há poucosestudos sobre essa e spécie no Brasil. Pesquisas sobre a biologia da espécie são necessáriaspara auxiliar a sua conservação. Assim, os resultados apresentados podem estimular futuras pesquisas em território brasileiro, contribuindo para a preservação da espécie.Palavras-chave: dinâmica populacional, manejo, Megalopidae.

Fish Assemblages and Fisheries Resources in Puerto Rico's Riverine Estuaries

AbstractTropical estuaries are diverse and productive habitats with respect to their fish assemblages and associated fisheries, but these ecosystems and fisheries are imperiled by multiple anthropogenic threats. Despite the economic, social, and biodiversity value of tropical estuarine fish assemblages, they are poorly understood, especially those on Caribbean islands. We sampled the fish assemblages of four estuaries that were broadly representative of riverine estuaries in Puerto Rico, including the Río Grande de Arecibo, Río Espiritu Santo, Río Mameyes, and Río Sabana. We used a combination of passive (gill nets) and active (seine) gears at locations that spanned the salinity gradient of each estuary during July–October 2013–2014 (rainy season) and March 2015 (dry season). Fish species richness among the riverine estuaries varied from 18 to 29 and was highest in the Río Espiritu Santo estuary. Nonmetric multidimensional scaling differentiated fish assemblages among estuaries but not by season or consistently by location within an estuary. Spearman's rank correlation analysis also revealed dissimilarity among each estuary's fish assemblage, as most pairwise correlations between the species compositions were not significant. We identified common and widespread species among estuaries, including sport fishes, such as the Tarpon Megalops atlanticus and Common Snook Centropomus undecimalis. As the only multi‐river assessment of riverine estuary fish assemblages in Puerto Rico, our results provide the best available information about the spatial variability of assemblages and fisheries resources. This information will benefit future conservation and fisheries management efforts, which are needed due to increasing anthropogenic impacts, such as illegal harvest, invasive species, and water diversions.

Consistency of elemental and isotope-ratio patterns across multiple scales from individual fish.

Assays of elemental and stable-isotope ratios across growth increments of scales have the potential to provide a non-lethal alternative to otolith chemistry for identifying migration and ontogenetic trophic shifts. A central assumption when employing scales as otolith analogues is that any scale from an individual will provide equivalent information about the chemical history of that fish. This assumption was investigated with multiple scales from wild and captive euryhaline Atlantic tarpon Megalops atlanticus from the north-west Gulf of Mexico. Elemental (Sr:Ca) and isotope-ratio (δ13 C and δ15 N) life-history profiles were compared among multiple scales from each fish. All three chemical proxies showed highly consistent patterns among non-regenerated scales, while patterns in regenerated scales diverged, indicating rapid regrowth of interior scale material at the onset of regeneration. Patterns of Sr:Ca and δ13 C covaried, supporting their use as salinity proxies, while δ15 N patterns were consistent with ontogenetic diet shifts. Water samples taken from aquaria holding captive fish were used to calculate partition coefficients for a suite of elements in M. atlanticus scales for future quantification of migratory movements in the region. Together, these results support the assumption that non-regenerated scales from individual M. atlanticus provide equivalent chemical histories, further validating their use as a viable non-lethal alternative to otoliths.

Low-temperature tolerance of juvenile tarpon Megalops atlanticus

The tarpon Megalops atlanticus is a tropical to subtropical species whose pole-ward distribution is thought to be limited by low water temperatures. In the western north Atlantic Ocean juvenile tarpon occur in estuaries of the South Atlantic Bight (SAB) north of Florida near the northern limit of its distribution, but it is currently unknown whether these individuals can survive winter, grow to maturity, and contribute to the adult population. As a first step to determine whether juvenile tarpon can survive winter conditions in the SAB, we conducted laboratory experiments to estimate minimum lethal temperatures of tarpon exposed to 1) ambient fluctuating winter water conditions and 2) a constant rate of temperature decline. Juvenile tarpon exposed to ambient winter water conditions had a mean ± standard deviation (SD) minimum lethal temperature of 13.7 ± 3.4 °C. When exposed to a constant rate of temperature decline (2 °C day−1), mean ± SD minimum lethal temperature (9.2 ± 0.8 °C) was lower than when tarpon were exposed to ambient fluctuating conditions. A combination of our results with all published data on the cold tolerance of juvenile tarpon resulted in an overall mean ± SD minimum lethal temperature of 12.0 ± 2.8 °C. Based on available long-term temperature records from SAB estuaries, overwinter survival of juvenile tarpon is unlikely in most aquatic habitats (e.g., tidal creeks, flats, open water). Similar to other estuarine transient fishes, juvenile tarpon likely exploit seasonably favorable nursery habitats and then migrate to other locations to overwinter.

Body size and the air-breathing organ of the Atlantic tarpon Megalops atlanticus

The air-breathing organ (ABO) of the Atlantic tarpon is formed by four parallel ridges of alveolar-like respiratory tissue that extend along the length of the physostomous gas bladder. The large and complex surface of each ridge is formed by a cartilage matrix that is completely infiltrated by a thin respiratory epithelium. Comparison of a size series of specimens demonstrates isometric growth of the ABO, and histological and SEM studies show comparable levels of tissue complexity. These findings suggest that air-breathing capacity, which is required for the survival of juvenile fish in their hypoxic nursery habitat, is retained in older tarpon inhabiting more oxygenated marine coastal habitats. The retention of air breathing in adult tarpon may be related to their occasional occurrence in hypoxic waters and their high rates of aerobic metabolism.

Salinity measurements from pop-up archival transmitting (PAT) tags and their application to geolocation estimation for Atlantic tarpon

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 357:101-109 (2008) - DOI: https://doi.org/10.3354/meps07288 Salinity measurements from pop-up archival transmitting (PAT) tags and their application to geolocation estimation for Atlantic tarpon Jiangang Luo1,*, Jerald S. Ault1, Michael F. Larkin1, Luiz R. Barbieri2 1University of Miami Rosenstiel School of Marine and Atmospheric Sciences (RSMAS), Division of Marine Biology and Fisheries, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA 2Florida Fish & Wildlife Conservation Commission, Florida Fish & Wildlife Research Institute, 100 8th Avenue SE, St. Petersburg, Florida 33701, USA *Email: jluo@rsmas.miami.edu ABSTRACT: A new wet/dry sensor was developed by the satellite-based pop-up archival transmitting (PAT) tag manufacturer to determine the wet and dry status of a tag, designed to indicate whether or not to initiate uplink transmissions to overhead satellites to extend tag battery life. We discovered that the wet/dry sensor can also be used to measure the salinity of coastal waters after we recovered a PAT tag showing oscillating readings of wet/dry sensor values that mimicked tidal cycles. We conducted a calibration experiment on 6 PAT tags to evaluate the stability, resolution, and accuracy of the sensor to obtain salinity measurements. Our results indicated that the wet/dry sensor was stable, and the resolution and accuracy of the sensor were good at low salinities (<20 psu), but relatively poor at high salinities. We then provide an example showing how the salinity information can be used to improve geolocation estimation for a large coastal marine fish, the Atlantic tarpon Megalops atlanticus. KEY WORDS: Salinity · PAT tags · Wet/dry sensor · Geolocation · Atlantic tarpon Full text in pdf format PreviousNextCite this article as: Luo J, Ault JS, Larkin MF, Barbieri LR (2008) Salinity measurements from pop-up archival transmitting (PAT) tags and their application to geolocation estimation for Atlantic tarpon. Mar Ecol Prog Ser 357:101-109. https://doi.org/10.3354/meps07288 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 357. Online publication date: April 07, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Recreational Catch and Release: Resource Allocation between Commercial and Recreational Fishermen

AbstractMaximizing catch rates and maximizing sustainable harvest are competing objectives for fisheries. In recreational fisheries, catch rate maximization may be the desired objective for species that are treasured more for their sporting value than for their harvest. This may be achieved through catch‐and‐release fishing, where there is no harvest. This objective, however, contrasts with management measures that require fish to be released because of size or season limits that constrain harvest to allowable catch levels and is not compatible with the management objective of obtaining maximum sustainable yield (MSY) as envisioned by many management institutions. These two objectives also conflict when commercial and recreational fisheries compete for the same resource. Partially, for this reason, many U.S. fisheries have been allocated entirely to the recreational sector (e.g., Atlantic sailfish Istiophorus platypterus, Atlantic blue marlin Makaira nigricans, white marlin Tetrapturus albidus, bonefish Albula vulpes, and tarpon Megalops atlanticus). Here, I apply a logistic surplus production model to an arbitrary fish stock to explore the potential benefits of recreational catch and release for a stock equally allocated to recreational and commercial sectors. The findings show that the stock will grow because of recreational releases if the commercial harvest is not allowed to increase beyond its MSY allocation. This results in higher sustainable catch rates for recreational anglers and a stable harvest for commercial fishers. This option would benefit both user groups.

First records of the subtropical fish Megalops atlanticus (Osteichthyes: Megalopidae) in the Cantabrian Sea, northern Spain

Meristic and morphometric data of a specimen of tarpon Megalops atlanticus caught off the Asturias coast, northern Spain, are reported. This is the first record of this species in Spanish waters.

Mercury Contamination in Freshwater, Estuarine, and Marine Fishes in Relation to Small-Scale Gold Mining in Suriname, South America

The extent of mercury contamination in Surinamese food fishes due to small-scale gold mining was investigated by determination of the total mercury concentration in 318 freshwater fishes, 109 estuarine fishes, and 110 fishes from the Atlantic Ocean. High background levels were found in the piranha Serrasalmus rhombeus (0.35 microg Hg x g(-1) muscle tissue, wet mass basis) and the peacock cichlid Cichla ocellaris (0.39 microg x g(-1)) from the Central Suriname Nature Reserve. Average mercury levels in freshwater fishes were higher in piscivorous species than in nonpiscivorous species, both in potentially contaminated water bodies (0.71 and 0.19 microg x g(-1), respectively) and in the control site (0.25 and 0.04 microg x g(-1), respectively). Mercury concentrations in piscivorous freshwater fishes were significantly higher in rivers potentially affected by gold mining than in the control site. In 57% of 269 piscivorous freshwater fishes from potentially contaminated sites, mercury levels exceeded the maximum permissible concentration of 0.5 microg Hg x g(-1). The highest mercury concentrations (3.13 and 4.26 microg x g(-1)) were found in two piranhas S. rhombeus from the hydroelectric reservoir Lake Brokopondo. The high mercury levels in fishes from Lake Brokopondo were to some extent related to gold mining because fishes collected at eastern sites (i.e., close to the gold fields) showed significantly higher mercury concentrations than fishes from western localities. In the estuaries, mercury levels in ariid catfish (0.22 microg x g(-1)) and croakers (0.04-0.33 microg x g(-1)) were distinctly lower than those in piscivorous fishes from contaminated freshwater sites. In the isolated Bigi Pan Lagoon, the piscivores snook Centropomus undecimalis (0.04 microg x g(-1)) and tarpon Megalops atlanticus (0.03 microg x g(-1)) showed low mercury levels. Mercury levels were significantly higher in marine fishes than in estuarine fishes, even with the Bigi Pan fishes excluded. High mercury concentrations were found in the shark Mustelus higmani (0.71 microg x g(-1)), the crevalle jack Caranx hippos (1.17 microg x g(-1)), and the barracuda Sphyraena guachancho (0.39 microg x g(-1)), but also in nonpiscivorous species such as Calamus bajonado (0.54 microg x g(-1)), Haemulon plumieri (0.47 microg x g(-1)), and Isopisthus parvipinnis (0.48 microg x g(-1)). Mercury levels were positively correlated with the length of the fish in populations of the freshwater piscivores S. rhombeus, Hoplias malabaricus, and Plagioscion squamosissimus, in estuarine species (Arius couma, Cynoscion virescens, and Macrodon ancylodon), and in S. guachancho from the Atlantic Ocean.