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Mining activities are a current environmental issue due to heavy metal release and subsequent metal uptake by organisms. In this study, we quantified the concentrations of essential (Cu, Zn) and toxic (Cd, Pb) elements in the muscle of 248 leopard groupers, Mycteroperca rosacea, captured by spearfishing and free diving close to a mining district in the Gulf of California during 2014-2015. We analysed metals using high-resolution inductively coupled plasma source mass spectrometry (HR-ICP-MS). We analysed metal concentrations by fish size, sex, maturity, season, year and risk factor for human consumption. The results indicated common levels of essential elements (Cu: 11 ± 34.3 μg/g, Zn: 377 ± 1390 μg/g) in comparison with toxic elements (Cd: 0.06 ± 0.1 μg/g, Pb: 0.98 ± 1.5 μg/g). Cadmium was within the permissible limit of Mexican standards (0.5 μg/g), but lead content bordered its limit (1.0 μg/g). Heavy metal concentrations were comparable between males and females. Metal variations were not significantly correlated with sex, maturity, season or year (p 0.05). The evaluation of benefits (daily mineral intake) and risks (target hazard quotients) to health indicated that these fish did not represent a risk of adverse effects to consumers within worldwide limits, while the nutritional benefits were high.

Mercury and selenium concentrations and Se:Hg molar ratio in edible muscle and hepatopancreas of the crab Callinectes arcuatus from coastal lagoons of northwest Mexico were determined using atomic absorption spectrophotometry. The three coastal lagoons were Santa Maria La Reforma (SMLR), Urias (UR), and Huizache-Caimanero (HC); samplings were carried out from December 2016 to October 2017. The mercury ranges in the muscle of C. arcuatus in SMLR, UR, and HC lagoons were 0.31–0.52, 0.15–0.45, and 0.22–0.55 μg g−1, respectively. In hepatopancreas, the values ranged from 0.08 to 0.15, 0.06 to 0.15, and 0.05 to 0.12 μg g−1 in SMLR, UR, and HC lagoons, in that order. For selenium concentrations in C. arcuatus muscle, the ranges 11.64–20.14, 14.88–19.71, and 15.27–29.51 μg g−1 were determined in SMLR, UR, and HC lagoons, respectively. While for hepatopancreas, the ranges were 34.34–44.13, 27.77–40.45, and 15.16–49.80 μg g−1, in that order. No significant relationships (p > 0.05) between mercury and selenium concentrations (in white meat and hepatopancreas) were observed in C. arcuatus carapace width and length. Se:Hg molar ratio values were 98.1 ± 20.8, 171.4 ± 81.6, and 176.8 ± 51.2 for SMLR, UR, and HC lagoons, in that order. This high ratio (> 1) in C. arcuatus edible muscle indicated that selenium concentration was sufficient to neutralize possible mercury toxicity, so it does not represent danger to humans when it is consumed.

The concentrations of essential (Cu, Zn) and toxic (Cd, Pb) elements were quantified in the muscle of leopard groupers, Mycteroperca rosacea, in a mining district in the Gulf of California. Metal concentrations were analyzed by size, sex, maturity, season, year, and a risk factor for human consumption. Results indicated elevated levels of essential elements (Cu: 11±34.3 μg/g, Zn: 377±1390 μg/g), up to 10 times higher than concentrations of toxic elements (Cd: 0.06±0.1 μg/g, Pb: 0.98±1.5 μg/g). Cadmium was within permissible limit stated by Mexican norm (0.5 μg/g), but lead bordering its limit (1.0 μg/g). Heavy metal concentrations were comparable between males and females. Metal variations were not significantly correlated to the sex, maturity, season, or year (p>0.05). The evaluation of benefits (Daily Mineral Intake) and risks (Target Hazard Quotients) to health indicated that these fish did not represent adverse effects to the consumer, within worldwide limits, but the nutritional benefits are high.

The present study shows the human health risk of Cd, Cu, Hg and Zn by consumption of clams Megapitaria squalida from Northwest Mexico, collected in 2013. The mean concentration for each metal in the soft tissue was: Zn > Cu > Cd > Hg; and mean values of 68.89 ± 37.59—30.36 ± 27.19, 8.77 ± 1.35—6.80 ± 0.36, 4.47 ± 0.21—3.18 ± 0.63 and 0.99 ± 0.81—0.52 ± 0.16 µg/g, respectively. Clam age was significantly negatively correlated (p

Adult sharpnose sharks (Rhizoprionodon longurio) with a mean total length of 110.93 ± 5.30 cm were obtained from a local fishery in Mazatlan (Southeast Gulf of California, Mexico). The total mercury content in muscle was analyzed by cold vapor atomic absorption spectrophotometry. The minimum and maximum total mercury content were 0.77 ± 0.23 and 2.33 ± 0.57 µg/g (dry weight), respectively. Only 6.6 % of the organisms did show mercury content higher than the permissible limit. No significant relationship was observed between weight and total mercury content in edible muscle of the sharks (r = 0.364, p > 0.05). The Hazard Quotient values for total mercury (0.005–0.015) and methyl mercury (0.022–0.065) indicated no risk by edible muscle consumption of the shark Rhizoprionodon longurio.

Mercury (Hg) was measured in the muscle, liver, and gonads of Haemulopsis elongatus and Pomadasys macracanthus from Mazatlan (SE Gulf of California) to determine the relationships of the hepatosomatic index (HSI) and gonadosomatic index (GSI) of fish with Hg concentrations in the corresponding tissues. Health risk to consumers was assessed by using the hazard quotient (HQ), considering the average rate of fish consumption in Mexico and Hg concentration in the edible tissue. In H. elongatus, the highest Hg levels were measured in the liver (3.748 μg g-1); in P. macracanthus, the highest Hg concentration was quantified in the muscle (0.574 μg g-1). In P. macracanthus, the HSI was negatively correlated with Hg concentration in the liver; in H. elongatus, there was also a negative relationship between Hg levels in gonads and the GSI. Mean HQ values in Haemulopsis elongatus (0.005) and Pomadasys macracanthus (0.002) were below the value (HQ ≥ 1) of concern. The significant reduction of HSI and GSI with Hg increase in the liver and gonads may suggest that Hg bioaccumulation in these fish shows adverse physiological effects. Though HQ values in both species were below the unit, i.e., the consumption of the muscle from this species does not represent a health risk, it is necessary to carry out surveys of fish consumption rates in coastal areas of Mexico to do a more precise health risk assessment associated to Hg intake.

Mercury and selenium concentrations and Se:Hg molar ratio in edible muscle and hepatopancreas of the crab Callinectes arcuatus from coastal lagoons of northwest Mexico were determined using atomic absorption spectrophotometry. The three coastal lagoons were Santa María La Reforma (SMLR), Urías (UR), and Huizache-Caimanero (HC); samplings were carried out from December 2016 to October 2017. The mercury ranges in the muscle of C. arcuatus in SMLR, UR, and HC lagoons were 0.31-0.52, 0.15-0.45, and 0.22-0.55 μg g

The leopard grouper Mycteroperca rosacea is endemic to northwestern Mexico. It has been classified as vulnerable by the IUCN since 2008. M. rosacea has high commercial value and is caught yearround in Baja California Sur (BCS). Biological information on this species, especially in its natural environment, is scarce, and the objective of this study was to analyze its reproductive biology in Santa Rosalia, BCS. A total of 345 specimens were collected from March 2014 to May 2015. The sex ratio was 2.0: 1.0 (females: males, P < 0.05). Population size at first maturity (L 50 ) was estimated at 40.77 cm TL; 37.31 cm TL for males and 42.44 cm TL for females. Gonadic development was synchronous by group, with a reproductive period occurring from March to May in 2014 and 2015 (at 20-23oC). The gonadosomatic index achieved maximum values in May 2014 and March 2015, as did the highest frequencies of mature and spawning individuals, indicating that there was a clear seasonal pattern of reproduction, and a negative correlation with temperature for both sexes. The hepatosomatic index and the condition index indicated that M. rosacea is not a species that requires storing of energy for reproductive events, as it seems to have food available year-round. Normal 0 21 false false false ES X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; line-height:115%; mso-pagination:widow-orphan; font-size:12.0pt; mso-bidi-font-size:11.0pt; font-family:"Times New Roman","serif"; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-ansi-language:ES; mso-fareast-language:EN-US;}

With the aim to expand the understanding of the feeding ecology of the swordfish, two supplementary techniques were used: analysis of stomach contents, including 244 samples; and analysis of stable carbon (δ13C) and nitrogen (δ15N) isotopes, with 128 samples of muscle tissues from animals collected in the western coast of Baja California. Samples were obtained from swordfish captured by the longline fleet that operates along the western coast of Baja California peninsula. Thirty-three different prey types were identified through the analysis of stomach contents. Based on the index of relative importance (IRI), cephalopods accounted for 98.91%, fish 0.88%, and pelagic crustaceans 0.21%. The stable isotope analysis showed δ15N values between 13.05‰ and 19.66‰, and δ13C values between − 19.32‰ and − 15.60‰, indicating that the swordfish feeds primarily on oceanic species. The stable isotope mixing model (SIAR) established that prey species that most contribute to the diet of Xiphias gladius were cephalopods, followed by the crustacean Pleuroncodes planipes, and the fish Lagocephalus lagocephalus. The SIBER test corroborates similar diets between sexes and sex-maturity groups, indicating that all swordfish analyzed essentially occupied the same trophic niche.

We evaluated the total Hg concentration in different tissues of squalid callista Megapitaria squalida in order to measure Hg distribution in tissue and to estimate human health risk. Samples were obtained by free diving in the SW Gulf of California, Mexico. Concentrations are given on a wet weight basis. A total of 89 squalid callista specimens were obtained, presenting an average Hg concentration of 0.07 ± 0.04 µg g−1. There were no significant differences (p > 0.05) in Hg concentration between tissues (visceral mass = 0.09 ± 0.08 µg g−1; mantle = 0.06 ± 0.07 µg g−1; muscle = 0.06 ± 0.04 µg g−1). The low Hg values found in squalid callista and its low risk quotient (HQ = 0.03) suggest that the consumption of squalid callista does not represent a human health risk. However, HQ calculated using MeHg was > 1, it which could indicate a potential risk related to consumption of clams.

Five leopard grouper Mycteroperca rosacea specimens were captured in the Gulf of California, two of which presented a rare orange pigmentation on both sides of the body. The remaining individuals presented changes to the normal pigmentation pattern on the left or right flanks. The possible causes of these phenomena are discussed.

Feeding habits determine many aspects of living organisms, where it lives, the time of day that it is active, energy flow, biomass consumed and intra- and interspecific interactions, it which provides information to make predictions about the effects of fisheries on predator-prey relationships. Accurate predictions require a thorough understanding of predator diets and prey selection. In this study, specimens of the crevalle jack Caranx caninus were obtained between October 2012 and October 2014 in the SE Gulf of California, Mexico, in order to determine its feeding habits and prey selection. A total of 238 specimens were obtained, of which 94 (39.5%) had stomachs containing food and 144 (60.5%) had empty stomachs. A total of 10 prey items were identified, corresponding to seven families that included fishes, crustaceans and cephalopods. According to the Index of Relative Importance (IRI) the most important prey were Anchoa spp. (IRI = 91.2%), Engraulis mordax (IRI = 1.8%), and fish from the Clupeidae family (IRI = 1.0%). The crevalle jack’s diet did not change with the season (warm or cold). The crevalle jack was considered a tertiary predator (trophic level = 4.3) that tends to feed on a reduced number of prey, characterizing it as a specialist and selective predator of engraulid fishes (Levin’s index, Bi = 0.08; E = 0.6).

espanolEl estudio de los habitos alimentarios de la barracuda mexicana, "Sphyraena ensis" Jordan y Gilbert, 1882, es importante para conocer los aspectos relevantes de su ecologia trofica (presas consumidas, amplitud de dieta, nivel trofico y flujos de energia), ya que brindan informacion valiosa sobre la dinamica de las comunidades marinas. En este contexto, el objetivo del presente trabajo fue determinar los habitos alimentarios de la barracuda mexicana, S. ensis, asi como las variaciones troficas con respecto a sexo (machos, hembras), tallas (individuos pequenos, medianos y grandes) y estacionalidad (lluvias y secas). Se obtuvieron muestras mensuales durante el periodo de febrero de 2014 a enero de 2015 en la region de San Blas, Nayarit, Mexico. En total se capturaron 308 organismos, con tallas de entre 30.6 y 58.7 cm de longitud total y pesos de entre 405 y 836 g. De los estomagos analizados, 264 (86%) contenian alimentos y 44 (14%) estaban vacios. El espectro trofico de la barracuda mexicana se conformo de 13 tipos de presa, agrupadas en 11 familias, 12 generos y 9 especies. De acuerdo con el indice de importancia relativa, las presas mas importantes fueron los peces, particularmente Sardinops spp. (40.36%), Hemiramphus saltator (40.24%), Opisthopterus dovii (10.83%), Anchoa spp. (4.17%) y Mugil cephalus (3.05%). Con base en los resultados obtenidos, la barracuda mexicana puede categorizarse como un depredador ictiofago oportunista de la zona epipelagica costera que se alimenta, principalmente, de especies de peces que forman densos cardumenes. Su espectro trofico no presento variaciones significativas por sexo y talla, pero el consumo de las presas mas importantes vario significativamente por estacion. EnglishUnderstanding the feeding habits of the Mexican barracuda, "Sphyraena ensis" Jordan and Gilbert, 1882, is important to elucidate relevant aspects of its trophic ecology (prey intake, diet breadth, trophic level, and energy flows), which in general provide valuable information on the dynamics of marine communities. Therefore, the purpose of this work was to assess the dietary habits of the Mexican barracuda, S. ensis, and to determine dietary variations by sex (males, females), size (small, medium, and large individuals), and season (rainy and dry). Monthly samples were obtained from February 2014 to January 2015 in the San Blas region, Nayarit, Mexico. A total of 308 specimens were captured. Individuals measured between 30.6 and 58.7 cm total length and weighed between 405 and 836 g. Of the analyzed stomachs, 264 (86%) contained food and 44 (14%) were empty. The diet of the Mexican barracuda comprised 13 prey items from 11 families, 12 genera, and 9 species. According to the index of relative importance, the most important prey were fishes, particularly Sardinops spp. (40.36%), Hemiramphus saltator (40.24%), Opisthopterus dovii (10.83%), Anchoa spp. (4.17%), and Mugil cephalus (3.05%). We conclude that the Mexican barracuda can be categorized as an opportunistic ichthyophagous predator in coastal epipelagic zones that feeds mainly on schooling fish species. The trophic spectrum did not vary significantly by sex or size, but the consumption of preferred prey varied significantly by season.

Mercury and selenium were assessed in Mustelus henlei, which is a carnivorous predatory shark that is important for the coastal communities of the northern Mexican Pacific (NMP). Sixty-two individuals were sampled; muscle and liver were isolated and analyzed by atomic absorption spectrophotometry. The mean Hg concentrations (wet weight) obtained for muscle (0.08 ± 0.10 μg g−1) and liver (0.09 ± 0.26 μg g−1) were below the allowed limits (

With the aim of determining the benefit from consumption of dolphinfish Coryphaena hippurus from La Paz and Cabo San Lucas in the southern area of the Gulf of California, mercury (Hg) and selenium (Se) were measured in liver and muscle of specimens (n = 362) collected between 2006 and 2013. Mean levels of Hg in muscle (0.61 μg g-1) and liver (0.42 μg g-1) of all individuals from La Paz were significantly higher (p < 0.05) than in fish from Cabo San Lucas; in the case of Se, mean concentrations in liver (1.54 μg g-1) of all individuals from La Paz were significantly higher (p < 0.05) than in fish from Cabo San Lucas. Hg levels in muscle were positively and significantly (p < 0.05) correlated with fork length and weight of fish; in liver, Hg and Se were significantly (p < 0.05) correlated with fork length and weight of specimens. Levels of Hg and Se in muscle and liver among years varied significantly (p < 0.05); although there was not a defined pattern of temporal fluctuations for both elements, the lowest Hg levels occurred in 2009 when surface water temperatures were the highest for the sampled years. With respect to the Se health benefit value (HBVSe), results were positive and above the unit in all cases; it implies that consumption of dolphinfish in the southern Gulf of California is beneficial.

With the aim of knowing annual variations of Hg concentrations in muscle and liver of blue marlin (Makaira nigricans) from the southern Gulf of California, fish were collected between 2005 and 2012 in three areas. In general, Hg levels were more elevated in liver than in muscle. Variations of Hg concentrations in muscle and liver among the studied years were not significant. Hg levels in muscle and liver increased significantly with length and weight of fish. In comparison to other studies, Hg levels in muscle and liver were lower. With respect to maximum permissible limits (1.0 µg g−1 wet weight) of Hg in Mexico, the average concentration (1.91 µg g−1 wet weight) in the edible portion (muscle) of blue marlin was over the legal limit; this issue is worth research efforts in relation to the rate of ingestion of this species and the co-occurrence of selenium in the edible portion.

Several abiotic factors influence the ecological responses of aquatic invertebrates to metal toxicity. We examined the effect of salinity (10, 20, and 30 psu) and temperature (25 and 32 °C) on acute and chronic arsenic (As) toxicity to the euryhaline rotifers, Proales similis and Brachionus ibericus. In general, higher salinities and low temperature resulted in lower arsenic toxicity. The population growth studies indicated that P. similis was more sensitive than B. ibericus to As. Arsenic toxicity intensified the vulnerability of P. similis to B. ibericus competition. Life table parameters decreased with increasing As levels in the medium. Chronic toxicity bioassays were more sensitive than acute toxicity tests for determining the adverse effect of As to rotifers. Our findings provide useful insights on the effect of arsenic on rotifer populations exposed to different temperature and salinity scenarios. Proales similis could be an important complement to brachionid rotifers for marine toxicity bioassays.

Background. The leopard grouper, Mycteroperca rosacea (Streets, 1877), is endemic to north-western Mexico and has high commercial value. Although facts of its basic biology are known, information on its trophic ecology, in particular, is scarce. The objective of the presently reported study was to characterize the feeding habits of M. rosacea through the analysis of stomach contents, and to determine possible variations linked to sex (male or female), size (small, medium, or large), or season (spring, summer, autumn, or winter), in order to understand the trophic role that this species plays in the ecosystem where it is found. Materials and methods. Fish were captured monthly, from March 2014 to May 2015 by spearfishing in Santa Rosalía, BCS, Mexico. Percentages by the number, by weight, and frequency of appearance of each food category, the index of relative importance (%IRI), and prey-specific index of relative importance (%PSIRI) were used to determine the importance of each prey item in the leopard grouper diet. Diet breadth was calculated using Levin’s index. Possible differences in the diet by sex, size, or season were identified through a multivariate PERMANOVA analysis. Results. A total of 341 leopard grouper specimens were collected, 309 of which had stomachs containing food. A total of 28 prey species were identified. According to the %IRI, the contribution to the diet of the coastal pelagic prey Nyctiphanes simplex and Sardinops sagax (Jenyns, 1842) was 87%, whereas according to the %PSIRI the contribution to the diet of those two prey species was 57%, in addition to several demersal prey species. A PERMANOVA analysis indicated that there were significant differences in the diet of leopard grouper by sex, size, and season, but the interactions sex–size, sex–season, size–season, and sex–size–season, were not significant. Conclusion. Mycteroperca rosacea was identified as a carnivorous predator with narrow trophic width, with significant differences in diet according to the sex, size, season, and size–sex interactions, which could be the result of different energetic requirements, hunting abilities, and food availability. The %PSIRI turned out to be the most adequate index to determine the feeding habits of fish, as it provides a better mean value to determine the most important prey.

Occupying the upper levels of trophic webs and thus regulating prey at lower levels, sharks play an important role in the trophic structure and energy dynamics of marine ecosystems. In recent years, the removal of these individuals from upper trophic levels as a result of overfishing has negatively affected ecosystems. We analysed the diet of blue sharks (Prionace glauca) caught off the west coast of Baja California Sur, Mexico, during the months of February–June in 2001, 2005 and 2006. We employed both stomach content and stable isotope analyses as each method provides distinct yet important information regarding the role of blue sharks in marine food webs, allowing us to estimate the relative contribution of different prey items to this predator's diet. Of the 368 stomachs analysed, 210 contained food (57%) and 158 (43%) were empty. Based on stomach contents and the index of relative importance (IRI), the pelagic red crab (Pleuroncodes planipes) was the most important prey, followed by the squids Gonatus californiensis (34.1%) and Ancistrocheirus lesueurii (10.4%). The mean (±SD) values for δ15N (16.48 ± 0.94‰) and δ13C (−18.48 ± 0.63‰) suggest that blue sharks prefer feeding in oceanic waters. The trophic level based on stomach content analysis was 4.05, while that based on the stable isotope analysis was 3.8, making blue sharks top consumers in the marine ecosystem of Baja California Sur, Mexico.

The demographic response of the brackish-water rotifers Proales similis and Brachionus plicatilis to mercury (0.5, 2, 8 and 32 μg L−1 of HgCl2) at different salinity levels (10 and 20‰) and two temperature (25 °C and 32 °C) regimes were evaluated. Median lethal concentration (LC50) for P. similis and B. plicatilis was 10 and 16 μg L−1, respectively, showing that Proales similis was more sensitive to mercury than B. plicatilis. The rate of population increase (r) for both species was greater at 10‰ salinity and 32 °C (ranged from 0.6 to 0.95 d−1). The r-value decreased as the concentration of mercury in the medium increased. Regardless of the temperature, at lower salinity and higher mercury concentration (32 μg L−1), P. similis died within six days. The survivorship of P. similis and B. plicatilis was higher at 25 °C than at 32 °C (ranged from 5 to 8 and 7–13 d, respectively). Fecundity was higher at 32 °C than at 25 °C for both rotifers species. There was a significant effect of the interaction among salinity, temperature, and mercury in both species on the reproductive variables such as net and gross reproductive rates, generation time and the rate of population increase. Considering the sensitivity of P. similis, we suggest that this species be included in the list of marine bioassay organisms.

Total mercury (Hg) concentrations were determined by atomic absorption spectrophotometry in muscles and liver of composite samples of Mugil cephalus and M. curema collected during November 2013 and in January, April, and July 2014 from the coastal lagoons Altata-Ensenada del Pabellón (AEP), Ceuta (CEU), and Teacapán-Agua Brava (TAG) of Sinaloa State. The mean Hg contents and information on local consumption were used to assess the possible risk caused by fish ingestion. Mean total mercury levels in the muscles ranged from 0.11 to 0.39 μg/g, while the range for liver was 0.12-3.91 μg/g. The mean Hg content of the liver was significantly (p 0.001) higher than that of the muscles only in samples collected from AEP. Although total Hg levels in the muscles were lower than the official permissible limit, the HQ values for methyl mercury calculated for the younger age classes of one fishing community were1, indicating a possible risk for some fishing communities of the Mexican Pacific coast.

The first record in Mexican waters of albinism and synophthalmia (partial cyclopia) in the Pacific angel shark, Squatina californica is presented. Albinism is not lethal, but synophthalmia may cause the death of the individual immediately after birth.

Artisanal fisheries in Mexico account for approximately 40% of the total national catch. In 2009, Baja California Sur (BCS) had the second largest catch of elasmobranchs on the Mexican Pacific coast. This paper characterizes and describes the artisanal elasmobranch fishery of Pacific coast of BCS from 2000 to 2010. Sixty artisanal camps were documented, of which 45 targeted elasmobranchs, using primarily gillnets and longlines. We identified 52 elasmobranch species. Gillnetting accounted for 73.5% of the fishing effort and most frequently captured Rhinobatos productus, Mustelus henlei and Myliobatis californica. Longline fishing accounted for 26.5% of effort, most frequently capturing Prionace glauca and Isurus oxyrinchus. The prevalence of juveniles of several species (e.g., Cephaloscyllium ventriosum, Galeorhinus galeus, Isurus oxyrinchus, and Myliobatis californica) within landings suggests that fishing effort may be opportunistically directed at breeding or nursery areas. Despite the dominance of species with wide distributions, we observed a significant biogeographic pattern in the abundance of some species relative to Bahia Magdalena. Results of the present study will be useful to detect changes in the structure of commercially exploited elasmobranch populations, and to provide useful indications for management purposes. La pesquería artesanal en México soporta aproximadamente el 40% de la captura total nacional. En 2009 Baja California Sur (BCS) fue el segundo estado con mayor registro de captura de elasmobranquios de todo el Pacifico Mexicano. En el presente trabajo se realizó la caracterización y descripción de la pesquería artesanal de elasmobranquios en la costa Pacífico de BCS del 2000 al 2010. Se registraron 60 campos artesanales, de los cuales en 45 se capturaron elasmobranquios usando como artes de pesca redes y palangres. Se identificaron 52 especies de elasmobranquios. Las redes representaron el 73.5% del esfuerzo pesquero, las especies que se capturaron con mayor frecuencia fueron Rhinobatos productus, Mustelus henlei y Myliobatis californica. Por otra parte los palangres representaron el 26.5% del esfuerzo pesquero, las especies capturadas con mayor frecuencia fueron, Prionace glauca e Isurus oxyrinchus. La presencia de especímenes juveniles de varias especies en los desembarques (p. ej. Cephaloscyllium ventriosum, Galeorhinus galeus, Isurus oxyrinchus, Myliobatis californica) sugiere que el esfuerzo pesquero podría ser oportunista dirigido a las zonas de crianza o de reproducción. A pesar del dominio de especies con distribuciones amplias, se observó un patrón biogeográfico significativo en la abundancia de algunas especies al sur y al norte de Bahía Magdalena. Los resultados del presente estudio serán de utilidad para poder detectar los posibles cambios en la estructura poblacional de los elasmobranquios explotados comercialmente.

We determined total Hg and Se contents of hepatopancreas, exoskeleton, and muscle, and the Se:Hg molar ratios in the muscle of shrimps Farfantepenaeus californiensis and Litopenaeus stylirostris caught in NE Pacific Mexican waters. Total Hg mean values in muscle, hepatopancreas, and exoskeleton were 0.31 ± 0.26, 0.28 ± 0.29, and 0.24 ± 0.06 μg g-1, and 0.46 ± 0.46, 0.41 ± .034, and 0.24 ± 0.06 μg g-1 for F. californiensis and L. stylirostris, respectively. In all tissues, the mean concentrations of Se tended to be close to one order of magnitude higher than the respective Hg values. In F. californiensis, the hepatopancreas of the larger commercial size had significantly (p

The present study determined the average Mercury bioaccumulation in the muscle tissue of four shark species (Carcharhinus falciformis, Prionace glauca, Sphyrna zygaena and Isurus oxyrinchus) captured in the Baja California Peninsula. We also evaluated biomagnification of some prey consumed by sharks. All sharks’ species had mercury levels over the limit specified by the Mexican government for human consumption. Blue shark (P. glauca) presented highest mercury values (1.96 ± 1.48 lg/g Hg d.w.) and it was the unique specie that showed a negative correlation with mercury content (Rs = -0.035, p = 0.91). Scomber japonicus was the prey with high content of Mercury (0.57 ± 0.02 lg/g).

The objective of this study was to establish the trophic niche of the silky shark and to determine the ecological role of this predator in the ecosystem close to Baja California. The trophic spectrum was analyzed from samples taken during summer and autumn (2000–2002) from the fishing camps of Punta Lobos and Punta Belcher on the western coast of Baja California Sur. A total of 263 stomach contents were analyzed (143 with food; 120 empty). The index of relative importance (IRI) showed that at Punta Lobos, silky sharks fed mainly on red crabs Pleuroncodes planipes (%IRI = 83%), whereas at Punta Belcher the main food item was the jumbo squid Dosidicus gigas (%IRI = 41%), followed by chub mackerel Scomber japonicus (%IRI = 33%). According to the Levin Index (Bi), the trophic niche breadth in silky sharks is low (Bi =

Concentrations of mercury (Hg) were quantified in muscle tissues of the Pacific angel shark, Squatina californica sampled from Southern Gulf of California, Mexico, considering total length, sex, diet and the dietary risk assessment. High Hg levels are typically associated with carnivorous fishes, however S. californica showed low Hg concentrations (1.0 µg g(-1)) in muscle (0.24 ± 0.27 µg g(-1) wet weight; n = 94). No effect of sex, total length and weight on Hg concentrations were observed in the shark (p 0.05). Hg concentrations were highest in the darkedge mishipman: Porichthys analis (0.14 ± 0.08 µg g(-1)) and red-eye round herring Etrumeus teres (0.13 ± 0.05 µg g(-1)) relative to other prey species, which could suggest that Hg concentrations in S. californica were influenced by these species. Given the relatively low concentration of Hg across age-classes and sex, consumption of S. californica's muscle tissue poses limited risk to humans.

Mercury (Hg) is the most dangerous trace element present in the edible parts of fishes and invertebrates. With the aim of having a general view on Hg occurrence in commercially exploited biota (fish and invertebrates) from selected estuarine systems of Mexico, we compiled information related to Hg levels in fish (elasmobranchs and teleosts), shrimps, clams, mussels and oysters from impacted estuarine areas and other coastal ecosystems in the Pacific Ocean and the Gulf of Mexico. Levels of Hg in the Asiatic clam Corbicula fluminea (a freshwater species) were relatively low (< 0.32 µg g−1) in comparison to individuals collected in moderate or severely impacted sites. In the case of marine mollusks ( Crassostrea corteziensis and Mytella strigata) Hg concentrations were comparable to those from low or moderately contaminated sites. In shrimps, Hg values were low (< 0.72 µg g−1) and consistently higher in hepatopancreas tissue than in muscle. Rays had lower Hg levels ( < 0.4 µg g−1 wet weight) than sharks (< 2.0 µg g−1 wet weight). Teleost fish have been studied more thoroughly than other groups; Hg levels in muscle tissue varied by two orders of magnitude (from 0.02 to 1.58 µg g−1 dry weight). Among studied organisms, fish are known as the main pathway of Hg entrance to humans. It is necessary to generate information of the rates of consumption of fish, especially of predator species. Considering legal limits of Hg and methyl Hg (1.0 and 0.5 µg g−1 wet weight, respectively) in edible portion of fish in Mexico, at present there is risk to the human population for the consumption of the scalloped hammerhead shark Sphyrna lewini.

We determined total mercury (Hg) distribution in muscle and liver of ten ray species and assessed health risk considering Hg levels in muscle and average consumption of rays in Mexico. Rays were collected from five sites in NW Mexico between March and November 2012. Hg concentrations ranged from 4.465 μg g(-1) in muscle of the longtail stingray Dasyatis longa to 0.036 μg g(-1) in liver of the diamond stingray Dasyatis dipterura. Considering all the individuals, Hg in muscle (1.612±1.322 μg g(-1)) was significantly (p0.05) higher than in liver (0.745±0.616 μg g(-1)). Regarding local health risk assessment, none of the ray species may cause adverse effects on consumers.

Elasmobranchs are frequently apex predators in marine ecosystems, and information on their diet is essential for understanding trophic relationships in these systems. The diet of the sicklefin smooth-hound, Mustelus lunulatus, was investigated through analysis of gut contents. The diet was relatively homogeneous and was dominated by crustaceans, consisting mostly of the anomuran crab Munida tenella (percentage of the prey-specific index of relative importance (%PSIRI) ¼ 30.5) and the bigtooth rock crab Cancer amphioetus (%PSIRI ¼ 9.9). Use of cumulative prey curves as a measure of precision indicated that data were sufficient to fully describe the diet of M. lunulatus. Further studies are necessary to fully characterize diet across sexes and successive age-classes.

The capture of two Gorgona guitarfish, Rhinobatos prahli, in the Gulf of Tehuantepec represents the first record for the species in Mexican waters and its northernmost range extension in the eastern Pacific.

The stomach contents of 50 Cortez damselfish Stegastes rectifraenum captured at Los Frailes, Baja California Sur, Mexico were analysed to describe their diet. According to our results, S. rectifraenum is an omnivorous species with a preferente for certain prey; invertebrates (benthic copepods) and algae (Bryopsis spp. and Ectocarpus spp.). Other animal components (Cerithium spp. and Olivella spp.) can also be found in their diet. No differences were observed between genders (analysis of similarity (ANOSIM), R 1⁄4 0.002, P 1⁄4 0.001) or among seasons (ANOSIM, R 1⁄4 0.046, P 1⁄4 0.001), therefore their food can be available all year at the rocky reef at Los Frailes.

A case of bicephaly in embryos of the blue shark Prionace glauca in the Mexican Pacific Ocean is described. Malformed female shark embryos were found in pregnant females caught in the Gulf of California (Punta Arenas) and off the western coast of Baja California Sur, Mexico (San Lazaro). Abnormal sharks showed a symmetric bicephaly that could be caused by the high number of embryos found in the uterus of the blue shark, which is the most fecund species of shark in the world. The abnormality probably began during the embryonic development.

The aim of this study was to determine the biomagnification of mercury through the principal prey of the blue shark, Prionace glauca, off the western coast of Baja California Sur, Mexico, as well as the relationship between mercury and selenium in blue sharks. High levels of mercury were found in shark muscle tissues (1.39 ± 1.58 μg/g wet weight); these values are above the allowed 1.0 μg/g for human consumption. The mercury to selenium molar ratio was 1:0.2. We found a low correlation between mercury bioaccumulation and shark size. Juveniles have lower concentrations of mercury than adults. Regarding the analyzed prey, the main prey of the blue shark, pelagic red crab, Pleuroncodes planipes, bioaccumulated 0.04 ± 0.01 μg/g Hg wet weight, but the prey with higher bioaccumulation was the bullet fish Auxis spp. (0.20 ± 0.02 μg/g wet weight). In terms of volume, the red crab P. planipes can be the prey that provides high levels of mercury to the blue shark.

We analyzed total mercury and selenium bioaccumulation in muscle tissue and cartilage fibers (fins) from smooth hammerhead shark, Sphyrna zygaena, caught off Baja California Sur, Mexico. In muscle tissue, the mercury concentration ranged from 0.005 to 1.93 microg g(-1) ww (wet weight), which falls within the safety limits for food set by international agencies (Hg1.0 microg g(-1) ww). Only one specimen showed a mercury value that exceeded this limit. In fins, the mercury bioaccumulation was lower (0.05). Selenium in muscle ranged from 0.11 to 1.63 microg g(-1) ww, while in fins it ranged from 0.13 to 0.56 microg g(-1) ww.

This is the first report of morphological abnormalities in the longtail stingray Dasyatis longa in the Gulf of California, Mexico. A young female (36.7 cm disc width) captured in a gill-net had deformed and incomplete pectoral fins, the anterior margins of which were separated from the head. The mouth was also deformed and the eyes and spiracles were situated on the lateral part of the head instead of on the dorsal surface. Some morphometric measurements are included. We conclude that the malformation of its mouth would prevent this stingray from surviving to adulthood.

The first record of an abnormality in the finescale triggerfish Balistes polylepis is described. In December 2010, a malformed specimen was caught in the southern Gulf of California, Mexico. The abnormality was a skeletal deformation consisting of a reduction in the shape and number of caudal vertebrae. The hypurals were not developed. The cause of finescale triggerfish deformation, who survived weighing approximately 68% less than normal, remained unknown.