The aquaculture industry is continuously seeking for fish that may have a commercial value. The most viable species are those that already have a commercial interest, that are easy to culture and that have the nutritive and acceptability characteristics required by the market. There is currently an increasing global trend towards diversification of the spectrum of cultured aquatic organisms, especially towards the use of native species with high potential for cultivation (^{FAO, 2010}; ^{Pérez-Velázquez et al., 2015}). Dormitator latifrons, also known as chame, popoyote, puyeque and Pacific fat sleeper (^{Rodríguez-Montes de Oca et al., 2012}), is a fish that lives in tropical and subtropical climates, with preference for brackish water with temperatures between 21 and 30°C (^{FAO, 2010}), although it has been found in water temperatures of up to 40°C (^{Ancieta & Landa, 1977}). It is distributed from California to Perú, inhabiting Pacific coastal waters, lagoons and estuarine systems (^{Yañez-Arancibia & Díaz-González, 1977}).

Fish muscle has high nutritional value and is recommended for human consumption, as it is a valuable source of high quality protein and essential fatty acids (^{FAO, 2014}). However, the content of lipids and fatty acids of the fish flesh varies greatly depending on the diet, just as in the wild it depends on environmental factors and the physiological state of the animals (^{Rueda et al., 1997}; ^{Bhouri et al., 2010}; ^{Osibona, 2011}). This study aimed to determine the proximate composition and fatty acid profile of the muscle of wild and cultured specimens of D. latifrons to assess the nutritional quality of this flesh for human consumption, as well as the possible aquaculture potential of this fish species.

Two hundred wild specimens of D. latifrons (weight 15.0 ± 0.2 g, length 15.01 ± 2.26 cm) were collected from the lagoon "El Quelele" in Nayarit, Mexico. A cast net was used to catch the fish. Of the total organisms collected, six were randomly selected and frozen immediately (-25°C) for later analysis. After a prophylactic treatment with trichlorphon (Neguvon^®) (^{Vega-Villasante et al., 2017}) for elimination of parasites, the remaining fish were confined in a circular pond of 19 m³ capacity, at a density of 10.2 fish m^-3 in the Laboratorio de Calidad de Agua y Acuicultura Experimental, Puerto Vallarta, Jalisco, Mexico. The fish were fed (10% of total biomass) for four months with a feed (Purina^®) formulated for the growing phase of tilapia (35% protein, 8% lipid and 4% ash). After four months, all fish were collected and frozen (-25°C) until use. Six cultured specimens (weight 150.0 ± 17.0 g, length 18.1 ± 6.2 cm) and the six wild fish previous frozen were used for analysis. Muscle samples of wild and cultured fish were analyzed in triplicate and reported as dry matter according to the methodology proposed by the ^{AOAC (1995)}. Total nitrogen was determined by the Kjeldahl method and multiplied by 6.25 to estimate the crude protein content. Total lipid content was determined by the Soxhlet method using petroleum ether as extracting solution. The content of ash was determined by calcining samples in a muffle furnace at 550°C for 4 h until a constant dry weight was reached. The nitrogen-free extract was determined by the difference of the sum of the other major components. The lipid fraction was extracted from fresh muscle samples of wild and cultured fish following the method described by ^{Folch & Sloane-Stanley (1957}). Fatty acid methyl esters (FAME) were prepared according to ^{Metcalfe et al. (1966}), and analyzed by gas chromatography (Hewlett Packard^® 5890II) using a flame ionization detector, a capillary column (Supelco Omegawax^® 320; 30×0.32 mm, 0.25 μ thick film) and helium as carrier gas. The initial temperature of the furnace was 140°C, but 5 min after injection of the sample (1 μL) the temperature was increased to 240°C and maintained for 30 min. Fatty acids were identified and quantified by comparison with the retention times of commercial standards (Supelco FAME Mix; 37 Component FAME Mix; FAME Mix GLC 90; C19) and well-characterized profiles of marine oil samples (PUFA1 and PUFA3). The concentration of fatty acids was calculated with the computer program HP^® ChemStation rev. A.06 for Windows^®, and expressed as weight percent of the total lipids in muscle tissue of D. latifrons. The proximate composition and fatty acid profiles of the muscle of wild and cultured fish were compared using one-way analysis of variance, followed by a Tukey's test to determine possible differences between treatments. Significance levels were set at P < 0.05. All statistical analyzes were performed using Sigma-Stat 3.0 for Windows^®.

Proximate analysis of the muscle showed significant differences (P < 0.05) in the content of crude protein, total lipids, and ash (Table 1). The relative content of crude protein in the muscle of wild fish was significantly higher (88.3 ± 0.6%) compared to cultured fish (82.4 ± 3.5%). These results coincide with those reported by other authors comparing wild and cultured fish (^{Rueda et al., 1997}; ^{González et al., 2006}; ^{Oz & Dikel, 2015}) (Table 1). These differences are usually explained by a higher accumulation of lipid content in cultured fish, which results in a lower amount of protein; this may be associated with factors such as the movement of fish or their diet (^{Nakamura et al., 2007}). In most cases, the concentration of lipids in the muscle of cultured fish is higher than in wild specimens.

As mentioned above, this is related to the type of diet and exercise during captivity. Total lipids increased from 1.7 to 5.3% in cultured D. latifrons, compared to wild specimens. These results coincide with those reported by other authors that compared wild and cultured freshwater fish (^{Rueda et al., 1997}; ^{González et al., 2006}; ^{Tanamati et al., 2009}; ^{Sharma et al., 2010}) (Table 1). The accumulation of lipids may also be related to feeding frequency; when fish that have been through a long time of fasting eat their fill, much of the energy is transformed into fat (^{Rueda et al., 1997}; ^{Orban et al., 2003}; ^{Rodríguez et al., 2004}; ^{Periago et al., 2005}; ^{González et al., 2006}; ^{López et al., 2006}; ^{Bhouri et al., 2010}; Osibona, 2011). ^{Acuña-Reyes (2013}) mentions that, from the nutritional point of view, fish could be classified according to their lipid content: lean or "white" (<1%), semi-fat (up to 2-7%) and fatty or "blue "(>7%). Following this classification and according to the results of the study, D. latifrons can be considered a semi-fat fish. The levels of oleic acid (C18:1n9) and linoleic acid (C18:2n6), were significantly higher (P < 0.05) in cultured fish (14.29 ± 1.46%, 20.48 ± 4.26%) compared to wild fish (6.97 ± 1.69%, 2.99 ± 2.06%) respectively (Table 2), meaning that the diet fed to the cultured fish contained vegetable oils. The total relative content of saturated fatty acids (SFA) was significantly higher (P < 0.05) in wild fish (42.47 ± 1.48%) compared to cultured fish (36.94 ± 0.91%). These values are lower than those reported for tilapia (Oreochromis mossambicus) (63.0%) and carp (Cyprinus carpio) (55.6%) (^{Jabeen & Chaudhry, 2011}), but higher than those reported for other freshwater species of commercial importance such as wild zander (Sander lucioperca), with 30.5-32.9% (^{Çelik et al., 2005}); wild (33.5%) and cultured (36.5%) yellow perch (Perca flavescens) (^{González et al., 2006}); and wild (28.04%) and cultured (20.74%) rainbow trout (Oncorhynchus mykiss) (^{Oz & Dikel, 2015}) (Table 2).

Among the SFA, palmitic acid (C16:0) was the main fatty acid (42% to 47% of total SFA) found in wild (17.80 ± 4.72%) and cultured (17.26 ± 2.39%) fish; there was no statistical difference between them. These results agree with those reported by other authors for freshwater fish. Palmitic acid is also the main saturated fatty acid in wild S. lucioperca (19.6-20.8%) (^{Çelik et al., 2005}); wild (17.5%) and cultured (20.9%) Perca flavescens (^{González et al., 2006}); wild (25.6%) and cultured (30.6%) Pseudoplatystoma corruscans; wild (20.9%) and cultured (25.9%) Piaractus mesopotamicus (^{Tanamati et al., 2009}); wild (23.97%) and cultured (31.80%) Labeo rohita (^{Sharma et al., 2010}); wild (30.87-35.05%) Cyprinus carpio; wild (44.1-47.11%) Oreochromis mossambicus (^{Jabeen & Chaudhry, 2011}); wild Pelteobagrus fulvidraco (21.87%) (^{Zhang et al., 2014}) (Table 2). The total content of monounsaturated fatty acids (MUFA) was significantly higher (P < 0.05) in cultured fish than in wild specimens (10.9 ± 0.68% and 16.85 ± 0.27%, respectively). Similarly, the concentration of linoleic fatty acid (C18:2n6) was almost seven times higher in cultured fish (20.48 ± 4.26%) than in wild fish (2.99 ± 2.06%). The increase in the concentration of these fatty acids in the muscle of cultured organisms may be related to the type of oil used in the preparation of balanced diets for cultured fish (^{George & Bhopal, 1995}; ^{Grigorakis et al., 2002}; ^{Badillo-Zapata et al., 2010}). Since the values were calculated as a proportion of total fat, the absolute value of this fatty acid (linoleic) is significantly higher.

Among LC-PUFAs, the relative concentration of EPA and DHA, was lower in cultured D. latifrons, although no significant differences were observed. Only the sum of EPA and DHA showed significant differences; wild fish had a higher content (P < 0.05) compared to cultured specimens (9.65 ± 0.05% and 5.82 ± 0.85%, respectively). EPA and DHA are found mainly in marine oils and are poorly synthesized, or not at all, by vertebrates, so that their presence in cultured fish is very limited or null if the formulated diet do not contain them (^{Yeganeh et al., 2012}). Some studies have suggested looking for alternatives to fish oil as a source of long-chain n-3 fatty acids (e.g., microalgae), and also that increasing the content of vegetable oils in formulated feed reduces the nutritional quality of cultured fish (^{Alasalvar et al., 2002}; ^{Strobel et al., 2012}; ^{Badillo-Zapata et al., 2014}). In the present study, the n-3/n-6 ratio was higher in the wild than in cultured fish (6.04 and 0.85, respectively). The content of n-3 and n-6 fatty acids must be balanced in the diet fed to cultured fish. ^{Strobel et al. (2012}) report that substituting fish oil with vegetable oils in the diet of cultured fish usually causes a decrease in the content of long-chain n-3 fatty acids. Therefore, including vegetable oils in the diet of cultured fish may have a detrimental effect on the proportion of essential fatty acids, altering the n-3/n-6 ratio. Similar results have been reported by some authors who compared wild and cultured fish, attributing them to the type of food consumed by fish in the natural environment and a lack of a higher content of n-3 fatty acids in commercial formulated diets fed to cultured organisms: wild (3.02) and cultured (2.88) Dicentrarchus labrax (^{Alasalvar et al., 2002}); wild (1.24-1.81) and cultured (0.3-0.5) Cyprinus carpio (^{Yeganeh et al., 2012}); wild (3.08) and cultured (0.46) Oncorhynchus mykiss (^{Oz & Dikel, 2015}).

The aquaculture potential of D. latifrons is currently under study. Since no specific formulated diet is available yet, it is recommended to use the commercial feed for tilapia. However, the results of the present study show that this diet is not appropriate for D. latifrons, and further studies are needed to find a suitable formula. It is worth noting that despite being wild fish acclimated to culture conditions, they adapted quickly and accepted being fed formula feed. However, considering that the values were estimated as relative quantities, it can be said that the fish muscles contained a sufficient amount of EPA and DHA, as found in wild specimens. Further study is needed on the fatty acid requirements of D. latifrons to modulate its fatty acid profile by favoring n-3 acids over n-6 acids. Based on the results obtained in the present study, the analysis of the proximate composition and fatty acid profile of muscle tissue of wild and cultured D. latifrons shows that this species is a rich source of protein and essential fatty acids. This study found that wild organisms have a higher content of EPA and DHA, as well as a higher n-3/n-6 ratio, compared with cultured fish. These results show that the nutritional characteristics of D. latifrons could be beneficial for human consumption and could make it a species with aquaculture potential; however, more research should be done to determine the nutritional requirements of the species, including lipids. This study sets the foundation for further studies on the dietary manipulation of D. latifrons to control the composition of essential fatty acids in cultured fish.