ABSTRACT Background: After its transfaunation from the Atlantic Ocean has been reported, the protozoan Perkinsus marinus has expanded its list of hosts in several species of mollusks in the Pacific Ocean, both in cultivation and in wild populations. Goals: The presence of this parasite was evaluated in the horsemussel Modiolus capax, in the southwestern Gulf of California. Methods: 60 mussels were collected per annual season for one year (summer, autumn, winter 2019-spring 2020, N = 240), in the mining port of Santa Rosalía (SR), Baja California Sur, Mexico. Thioglycollate staining was used to detect presumptive hypnospores and the polymerase chain reaction (PCR) technique for its confirmation. The prevalence, parasite load and intensity of infection were obtained in each sampling. Results: Presumptive hypnospores of the parasite were detected with thioglycollate staining in almost 20% of the samples analyzed, of which only 5% were positive for confirmation with PCR. Neither the prevalence (6.66-33.33%) nor the parasite load (˂ 2.75 hypnospores/g) showed a tendency to increase with time; the intensity of infection ranged from negative to light. Salinity showed correlation with parasite load (r = 0.99, p = 0.002). Conclusions: The results suggest that M. capax in SR presented low susceptibility to the parasite, so its health is not compromised when hosting P. marinus. Although it is the first report of the protozoan in this mussel, continuous monitoring is recommended to know not only the health status of the bivalve in the region, but also of the other species of mollusks that inhabit there.

RESUMEN Antecedentes: Después de haberse reportado su transfaunación del océano Atlántico, el protozoario Perkinsus marinus ha ampliado su listado de hospederos en varias especies de moluscos del océano Pacífico, tanto en cultivo como de poblaciones silvestres. Objetivos: Se evaluó la presencia de este parásito en el mejillón “choro”, Modiolus capax, en el suroeste del Golfo de California. Métodos: Se colectaron 60 mejillones por estación anual durante un año (verano, otoño, invierno 2019-primavera 2020, n = 240), en el puerto minero de Santa Rosalía (SR), Baja California Sur, México. Se utilizó la tinción con tioglicolato para detectar presuntas hipnosporas y la técnica de reacción en cadena de la polimerasa (PCR) para su confirmación. Se obtuvieron la prevalencia, carga parasitaria e intensidad de infección en cada muestreo. Resultado: Se detectaron presuntas hipnosporas del parásito con la tinción de tioglicolato, en casi 20% de las muestras analizadas, de las que sólo el 5% fueron positivas para su confirmación con PCR. Ni la prevalencia (6.66-33.33%) ni la carga parasitaria (˂ 2.75 hipnosporas/g) mostraron una tendencia a aumentar con el tiempo; la intensidad de infección fue de negativa a ligera. La salinidad mostró correlación con la carga parasitaria (r = 0.99, p = 0.002). Conclusiones: Los resultados sugieren que M. capax en SR presentó baja susceptibilidad al parásito, por lo que su salud no se encuentra comprometida al hospedar a P. marinus. Aunque es el primer reporte del protozoario en este mejillón, es recomendable el monitoreo continuo para conocer, no solo el estado sanitario del bivalvo en la región, sino también, de las otras especies de moluscos que ahí habitan.

Abstract: There are abundant reports of symbiosis wherein crustaceans live inside or on mollusks; however, there are few published records of gastropods hosting decapods. This study examines the biological association between fifteen snails (124.86 ± 19.01) from the species Pacific crown conch Melongena patula and the porcelain crab Euceramus transversilineatus. Morphometric relationships of both invertebrates, as well as some sexual characteristics of the crab were conducted. These invertebrates were sampled in the Navachiste Lagoon, in the south eastern Gulf of California, Sinaloa, Mexico. It was found 86.6% of the snails housed at least a female or a male porcelain crab (17.82 ± 3.27 mm total body length) or a pair of them (heterosexual and same sex) with a sexual proportion of 2M:1F. There were no correlations between any of the crab and snail based on their analyzed morphometric relationships. For the crab males, the measurements of both chelae presented relationships with total body length, carapace length, and abdomen width however, no significant differences were observed between the mean width and chelae length of males, females or between sexes. Of the six females collected, four were gravid. Preliminary observations indicated that the porcelain crab E. transversilineatus is a commensal endosymbiont that coexist in short-term association with M. patula. Their population distribution suggests that E. transversilineatus are polygamous with a promiscuous mating pattern.

Resumen: Existen abundantes informes de simbiosis en los que los crustáceos viven dentro o encima de moluscos, sin embargo, hay pocos registros publicados de gasterópodos que alberguen decápodos. Se examinó la asociación biológica entre el caracol corona del Pacífico, Melongena patula, y el cangrejo porcelánido, Euceramus transversilineatus, describiendo las relaciones morfométricas de ambos invertebrados, así como algunas características sexuales del cangrejo. Se muestrearon 15 caracoles (124,86 ± 19,01 mm de altura de concha) en la laguna Navachiste, en el sureste del Golfo de California, Sinaloa, México. El 86,6% de ellos albergaba al menos un cangrejo de porcelana hembra o macho (17,82 ± 3,27 mm de longitud total del cuerpo) o un par (heterosexual y mismo sexo) con una proporción sexual de 2M:1H. No hubo correlaciones entre ninguna de las relaciones morfométricas analizadas entre el cangrejo y caracol. Para los cangrejos, las mediciones de ambas quelas presentaron relaciones con la longitud corporal total, longitud del caparazón y ancho del abdomen en los machos; sin embargo, no se observaron diferencias significativas entre el ancho medio y la longitud de quelas de machos, hembras o entre sexos. De las seis hembras recolectadas, cuatro eran grávidas. Las observaciones preliminares indican que el cangrejo porcelánido E. transversilineatus es un endosimbionte comensal que coexiste en asociación a corto plazo con M. patula. Su distribución poblacional sugiere que E. transversilineatus es polígamo con un patrón de apareamiento promiscuo.

ABSTRACT. The protozoan Perkinsus marinus has been associated with high mortality episodes of the eastern oyster Crassostrea virginica in the USA. The presence of P. marinus on the pleasure oyster Crassostrea corteziensis cultivated in two estuaries on the southeast coast of the Gulf of California was evaluated. Oysters were collected monthly (September 2016 to September 2017) and analyzed using Ray's fluid thioglycollate medium (RFTM) and polymerase chain reaction (PCR). Water parameters and oyster biometrics were also recorded. Pathogen prevalence increased over time from 0 to 100% in oysters from La Pitahaya, and from 0 to 83.33% in those from Bacorehuis. At both oyster farms, infection intensity was light (<1×104 parasites g-1 wet tissue), pathogen prevalence and infection intensity were correlated with oyster size and weight, and there was a strong correlation between P. marinus prevalence and intensity (La Pitahaya r = 0.91; Bacorehuis r = 0.82). The oysters that resulted positive for P. marinus by RFTM also were assayed using PCR. P. marinus presence was confirmed in 98.27% (114/116) of the oysters from La Pitahaya, and 95.83% (46/48) of those from Bacorehuis. The detection of P. marinus confirms that this pathogen is well established in the area with high expression during the warmer season. Despite the light infection intensity of this parasite at both sites, health surveillance of this bivalve in the region is highly advisable.

ABSTRACT The gonadal maturation of the pleasure oyster Crassostrea corteziensis during four cultivation cycles (November 2004-June 2005, N4J5; August 2014-February 2016, A14F16; September 2015-December 2016, S15D16; September 2016-August 2017, S16A17) was studied in the southeastern Gulf of California, Mexico. Although C. corteziensis exhibited the typical reproductive phases (undifferentiated or resting, initial gametogenesis, advanced gametogenesis, maturity, spawning and post-spawning), the intensity of reproduction and the timing of the onset of the different phases of gonadal development varied in each cultivation cycle. Reproductive peaks were observed in different months (N4J5 in May, A14F16 in July, S15D16 in May and S16A17 in June) during spring and summer. Spawning correlated with temperature in the N4J5 and A14F16 cultivation cycles but it showed no correlation with chlorophyll-a concentration in any of the cultivation cycles. C. corteziensis presented an opportunistic continuous reproductive strategy with spawning occurring during several months of the year. The modification of the species' reproduction pattern could contribute to the natural settlement of larvae, increasing the natural production of this native oyster resource in the southeast of the Gulf of California, where it has been fished intensively.

ABSTRACT. The blood cockle Larkinia grandis is a commercially important resource in the Gulf of California, but little information is available on this species. In this study, the interactions between body weight (BW) and shell length (SL), height (SH), and width (SW) were evaluated in a L. grandis population in the Gulf of California, Mexico. Eighty cockles were hand-picked monthly from August 2017 to July 2018 near and/or under mangrove trees on the southeastern coast of the Gulf of California. The range of shell measurements (SL = 142.00-44.57 mm, SH = 85.50-31.15 mm, SW = 76.56-32.03 mm) indicates that the sampled population was dominated by adult specimens. Only the coefficient of variation for BW exhibited high dispersion (23%-45%). The potential relationships between BW and SL, SH, and SW were non-linear. The strongest interaction was found between BW and SW (R2 = 0.934), with the BW-SW relationship best describing the growth of this ark clam. All shell dimension-weight relationships were significant (P ≤ 0.05), indicating both negative (SL-SW and SH-SW) and positive (SL-SH, BW-SL, BW-SH, and BW-SW) allometric growth. The b values ranged from 0.8950, for the LogSH-LogSW relationship, to 2.6240, for the LogBW-LogSH interaction. This preliminary information is useful for developing conservation and sustainable exploitation strategies for this species, which is of economic importance to this region.

RESUMEN. El berberecho Larkinia grandis es un recurso comercialmente importante en el golfo de California, pero hay poca información disponible acerca de esta especie. En este estudio, se evaluaron las interacciones entre el peso corporal (BW) y la longitud (SL), la altura (SH) y el ancho (SW) de la concha en una población de L. grandis en el golfo de California, México. Se recolectaron a mano 80 berberechos mensualmente, desde agosto de 2017 hasta julio de 2018, de cerca y/o debajo de los árboles de mangle, en la costa sureste del golfo de California. El intervalo de medidas de las conchas (SL = 142.00-44.57 mm, SH = 85.50-31.15 mm, SW = 76.56-32.03 mm) indica que la población muestreada estaba dominada por especímenes adultos. Solo el coeficiente de variación para BW exhibió alta dispersión (23%-45%). Las relaciones potenciales de BW con SL, SH y SW no fueron lineales. La interacción más fuerte se encontró entre BW y SW (R2 = 0.934); la relación BW- SW describió mejor el crecimiento de este árcido. Todas las relaciones entre la dimensión y el peso de la concha fueron significativas (P ≤ 0.05), lo cual indica tanto crecimiento alométrico negativo (SL-SW y SH-SW) como positivo (SL-SH, BW-SL, BW-SH y BW-SW). Los valores de b oscilaron entre 0.8950, para la relación LogSH-LogSW, y 2.6240, para la interacción LogBW-LogSH. Esta información preliminar es útil para desarrollar estrategias de conservación y explotación sostenible para esta especie de importancia económica en la región estudiada.

ABSTRACT The squalid callista clam (Megapitaria squalida) is a popular raw seafood item for human consumption; however, as a filter feeder, this clam accumulates heavy metals from natural and anthropogenic sources. The concentrations of copper (Cu), cadmium (Cd), chromium (Cr), nickel (Ni), lead (Pb), zinc (Zn), arsenic (As), and mercury (Hg) in sediments and the soft tissues of M. squalida from two sites on the southeastern coast of the Gulf of California, Mexico, were evaluated from April 2016 to April 2017 on a monthly basis. The metal concentrations in sediments from both sites did not exceed the Mexican and international regulations. Concentrations of Cd and Pb in the clams from Altata bay (2.49 and 5.68 µg/g dw, respectively) and Agiabampo bay (2.38 and 5.54 µg/g dw, respectively) exceeded the permissible limits recommended by Mexican sanitary regulations, thus representing a threat to human health. The higher values of Cd, As, and Hg obtained for the biota sediment accumulation factor in both sampling areas indicate that squalid callista is a strong accumulator of these metals. The metal burdens in sediments and M. squalida soft tissues are influenced by chemicals from agriculture and aquaculture, as well as urban sewage disposal near both sites. This study brings useful information on metal bioaccumulation in one of the most important commercial clam species on the Pacific coast.

RESUMEN La almeja callista escuálida (Megapitaria squalida) es un marisco popular que se consume crudo, pero por ser filtrador, puede acumular metales pesados de fuentes naturales y antrópicas. En el presente trabajo se evaluaron, de abril de 2016 a abril de 2017, las concentraciones mensuales de cobre (Cu), cadmio (Cd), cromo (Cr), níquel (Ni), plomo (Pb), zinc (Zn), arsénico (As) y mercurio (Hg) en sedimentos y tejidos blandos de M. squalida de dos sitios de la costa sureste del Golfo de California, México. Los niveles de metales en los sedimentos de ambos sitios no excedieron las regulaciones mexicanas e internacionales. Las concentraciones de Cd y Pb en las almejas de la bahía de Altata (2.49 y 5.68 µg/g ps, respectivamente) y la bahía de Agiabampo (2.38 y 5.54 µg/g ps, respectivamente) sí excedieron los límites permisibles recomendados por las regulaciones sanitarias mexicanas, lo que representa una amenaza para la salud humana. El factor de acumulación de sedimentos en la biota para las dos áreas muestreadas indica que la almeja callista escuálida es un acumulador fuerte de Cd, As y Hg. Las concentraciones metálicas en los sedimentos y los tejidos blandos de M. squalida están influenciadas por los productos químicos utilizados en la agricultura y la acuicultura, así como por el suministro de aguas residuales urbanas cercanas a ambos sitios. Este estudio brinda información útil sobre la bioacumulación de metales en una de las especies de almejas comerciales más importantes de la costa del Pacífico.

ABSTRACT Background: Different species of Perkinsus spp. have been associated to mortality of commercial mollusks. Goals: The prevalence of Perkinsus sp. in the callista clam Megapitaria squalida was evaluated monthly (June 2015 to November 2016) to determine the relationship between the infection and size of clam. Methods: 5,000 clam seeds (5.73 mm height of the shell and 0.03 g of initial weight) were placed in a fishing refuge of Altata, Sinaloa. A total of 60 specimens were collected each month to evaluate their growth and parasite prevalence. The water physicochemical parameters (temperature, salinity, pH, dissolved oxygen, depth, and transparency) and the length, height, and width of the shell and final weight of M. squalida were obtained. Results: Ray’s thioglycollate fluid medium test (MFTR) detected spherical cells (10X) of dark color indicating the presence of presumed hypnospores of Perkinsus sp. during the first 17 months of sampling. The mean infection intensity was grade 2 (mild), while the maximum prevalence was 43.33% in the months of November (2015) and March (2016), with an average of 21.05%. None of the Perkinsus sp sample (n = 112) positively detected by MFTR confirmed the presence of the protozoan. There was no correlation (p >0.05) between the prevalence of the pathogen with all the parameters studied. Conclusions: The results suggest that M. squalida is not susceptible to Perkinsus sp. The present represents the first report of Perkinsus sp. in the callista clam M. squalida.

RESUMEN Antecedentes: Diferentes especies del protozoario Perkinsus spp. han sido asociados con mortalidades de moluscos comerciales. Objetivos: Se evaluó la prevalencia de Perkinsus sp. en la almeja Megapitaria squalida (junio 2015 a noviembre de 2016) para determinar la relación de la infección con la talla. Métodos: Se sembraron 5,000 semillas (5.73 mm altura de la concha y 0.03 g de peso inicial) en un refugio pesquero de Altata, Sinaloa. Se recolectaron 60 ejemplares cada mes para evaluar su crecimiento y prevalencia del parásito. Se obtuvieron los parámetros fisicoquímicos del agua (temperatura, salinidad, pH, oxígeno disuelto, profundidad y transparencia) y la longitud, largo y ancho de la concha y peso final de M. squalida. Resultados: La prueba de medio fluido de tioglicolato de Ray (MFTR) detectó células esféricas (10X) de color obscuro, indicando la presencia de presuntas hipnosporas de Perkinsus sp. durante los primeros 17 meses de muestreo. La intensidad de la infección promedio fue de grado 2 (leve), mientras que la prevalencia máxima fue de 43.33% en los meses de noviembre (2015) y marzo (2016), con un promedio de 21.05%. Ninguna de las muestras positivas (n = 112) de Perkinsus sp. con MFTR confirmó la presencia del protozoario. No se obtuvo correlación (p >0.05) entre la prevalencia del patógeno con todos los parámetros estudiados. Conclusiones: Los resultados sugieren que M. squalida es poco susceptible a la infección de Perkinsus sp. El presente trabajo representa el primer reporte de Perkinsus sp. en la almeja chocolata M. squalida.

ABSTRACT Symbiosis between decapods and mollusks provides a unique opportunity to examine some of the evolutionary strategies employed by marine invertebrates. We describe the sexual and reproductive traits of the pearl oyster shrimp, Pontonia margarita Verril, 1869, found symbiotically inhabiting the mantle cavity of the rugose pen shell, Pinna rugosa Sowerby, 1835. Solitary males and females (ovigerous and non-ovigerous) and heterosexual pairs (with ovigerous and non-ovigerous females) were found in a total of 47 rugose pen shells collected from a sandy area with seagrass meadows on the southeastern coast of the Gulf of California, Mexico. The body length (BL) of female P. margarita was correlated with the shell volume of their rugose pen shell host. The sex ratio was female-biased (0.85M:1F). Female P. margarita were larger than their male counterparts in terms of BL, cephalothorax length (CL), and the maximum chelae length of the second pereopod (MCL). The CL and MCL were more strongly correlated for males (r = 0.70, p = 0.01). The number and volume of eggs per ovigerous female varied from 95 to 1,571 and from 5.46 ± 0.48 to 8.85 ± 0.97 mm3, respectively. Our results indicate polygamous behavior and social monogamy among P. margarita, and a short-term pairing system for their association with P. rugosa.

Abstract. The morphometric relationships of the siphon clam Panopea globosa from Sinaloa, Mexico, were analyzed from February 2014 to April 2015. A total of 370 specimens were collected, measured (shell length, width, and height) and weighed (body weight, tissue weight, and shell weight). The coefficient of determination indicated variation in the fitting of morphometric variables among measured traits. The type of relative growth for all morphometric relationships was negative allometry. This is the first report on morphometric relationships of P. globosa from Sinaloa, Mexico.

ABSTRACT The pen shell (Atrina maura) is a filter-feeder bivalve that may accumulate metals in its body. The objective of this study was to determine seasonal concentrations of copper (Cu), chromium (Cr), cadmium (Cd), nickel (Ni), lead (Pb), arsenic (As), zinc (Zn), and mercury (Hg) in soft tissue and muscle of A. maura cultivated in a farm located in the southeastern coast of the Gulf of California from summer 2011 to summer 2012. Except for Cu, the higher metal concentrations were found during the dry season (winter 2011-spring 2012). The mean values in soft tissue fluctuated from 0.064 ± 0.01 µg/g (dry weight [dw]) for Hg to 485.66 ± 71.12 µg/g (dw) for Zn, while for muscle they varied from 0.058 ± 0.03 µg/g (dw) for Hg to 64.83 ± 4.90 µg/g (dw) for Zn. Concentrations of cadmium (18.15 µg/g in soft tissue and 1.82 µg/g in muscle, wet weight [ww]) and lead (2.31 µg/g in soft tissue, ww) exceeded the permissible limits (36.3, 3.64, and 2.31 times, respectively) recommended by the sanitary regulations of the official mexican standards. The results suggest that variation of metal levels in cultivated pen shell could be influenced by seasonality and anthropogenic activities such as agriculture and aquaculture developed around the culture zone. Continual monitoring of metals in farmed pen shell is recommended.

RESUMEN El callo de hacha (Atrina maura) es un bivalvo filtrador que puede acumular metales en su cuerpo. El objetivo de este trabajo fue determinar las concentraciones estacionales de cobre (Cu), cromo (Cr), cadmio (Cd), níquel (Ni), plomo (Pb), arsénico (As), zinc (Zn) y mercurio (Hg) en tejido suave y músculo de A. maura proveniente de una granja del sureste del Golfo de California, del verano de 2011 al verano de 2012. Las concentraciones más altas de todos los metales, con excepción del Cu, se encontraron en la estación de secas (invierno 2011-primavera 2012). Los valores promedio (peso seco) en el tejido suave fluctuaron de 0.064 ± 0.01 µg/g para Hg a 485.66 ± 71.12 µg/g para Zn, mientras que en músculo variarion de 0.058 ± 0.03 µg/g para Hg a 64.83 ± 4.90 µg/g para Zn. Las concentraciones promedio en peso húmedo para cadmio (18.15 µg/g en tejido suave y 1.82 µg/g en músculo) y plomo (2.31 µg/g en tejido suave) excedieron los límites permitidos (36.3, 3.64 y 2.31 veces, respectivamente) por la regulación sanitaria de las Normas Oficiales Mexicanas. Los resultados sugieren que la variación de metales encontrada en el callo de hacha pudo estar influida por la estacionalidad y las actividades antropogénicas desarrolladas en los alrededores de la zona de cultivo, como agricultura y acuacultura. Se recomiendan monitoreos continuos de metales en callo de hacha cultivado.

Abstract Background: For its flesh and flavor, the Pacific oyster Crassostrea gigas is cultivated worldwide, but as filter feeders, this bivalve bioaccumulates heavy metals from different pollution sources, rendering them unsafe for human consumption. Goals: We carried out this study to assess the heavy metal concentrations in cultivated oysters from a farm located on the southeastern coast of the Gulf of California during 2011. Methods: Oyster samples were analyzed monthly (March-December 2011) for cooper (Cu), cadmium (Cd), chromium (Cr), nickel (Ni), lead (Pb), zinc (Zn), arsenic (As), and mercury (Hg). Results: The mean values (µg g-1, dry weight) for each metal were Cu = 51.42 ± 25.92, Cr = 24.97 ± 32.38, Cd = 13.84 ± 4.22, Ni = 10.26 ± 12.18, Pb = 2.18 ± 1.28, As = 0.37 ± 0.08, Zn = 267.42 ± 92.29, and Hg = 0.02 ± 0.01. Conclusions: The results suggest that metal burdens could be influenced by anthropogenic activities such as agriculture and aquaculture surrounding the culture zone. Cu, Cr, Cd, and Pb levels (µg g-1, fresh weight) were above the maximum permissible values and thus pose a threat to human health. Metal concentrations must be monitored periodically.

Resumen Antecedentes: El ostión del pacífico, Crassostrea gigas, es cultivado en el mundo por su sabor y textura de la carne, pero por ser un organismo que se alimenta mediante filtración, puede acumular metales pesados haciéndolo peligroso para su consumo. Objetivos: El presente estudio evaluó la concentración de metales pesados en ostiones cultivados en una granja localizada en la costa sureste del Golfo de California durante 2011. Métodos: Se tomaron muestras de ostión cada mes (marzo-diciembre 2011) para analizar el contenido de cobre (Cu), cadmio (Cd), cromo (Cr), níquel (Ni), plomo (Pb), zinc (Zn), arsénico (As) y mercurio (Hg). Resultados: Los valores promedio (µg g-1, peso seco) de cada metal fueron: Cu = 51.42 ± 25.92, Cr = 24.97 ± 32.38, Cd = 13.84 ± 4.22, Ni = 10.26 ± 12.18, Pb = 2.18 ± 1.57, As = 0.37 ± 0.26, Zn = 267.42 ± 92.29 and Hg = 0.02 ± 0.01. Conclusiones: Los resultados obtenidos sugieren que la carga de metales pudo haber sido influenciada por actividades antropogénicas desarrolladas en los alrededores del área de cultivo, como agricultura y acuacultura. Los niveles de Cu, Cr, Cd y Pb en peso húmedo rebasaron los límites máximos permitidos re presentando un riesgo para la salud humana. La carga de los metales estudiados debe ser monitoreada periódicamente.

Diploid and triploid Crassostrea gigas oysters were cultivated at three farms (Guasave, Navolato and Ahome) in Sinaloa, Mexico, to evaluate their growth and economic performances. Growth rate and survival of oysters were compared in long-line cultivation and were mostly affected by water parameters rather than ploidy or their interaction. The highest growth rates for shell length (8.01 mm month-1) and body weight (9.08 g month-1) were obtained for the Ahome/triploid group. Survival differed significantly from 98.6% for the Guasave/triploids to 76.7% for the Ahome/diploids. After the first production cycle, more than 80% of production costs represent the purchase of cultivation equipment and salaries contributed with around 9%. The Guasave farm produced the highest profits (US$8,053.71 diploids, US$8,182.19 triploids). Use of diploids starting the production cycle on October-November to avoid mortality and improve final profit is recommended.

This study demonstrate the advantage of multi-model approach to calculate the growth of Crassostrea gigas cultivated in the Gulf of California. The generalized von Bertalanffy growth model (VBGM) and its modification to represent the seasonal variations (VBGM seasonal) were tested. The parameters of each model and their confidence intervals were computed using the maximum-likelihood method. The best-fitting model was selected using the Akaike information criterion (AIC). According to the AIC, the VBGM seasonal best described the growth of the C. gigas. The conclusion was that C. gigas exhibits a seasonal growth pattern under the cultivation conditions of the present study.

The evaluation of growth and survival of bivalves represents an important tool in culture. Growth performance and survival of the pen shell Atrina maura cultivated in Isla Los Redos, at the southeastern coast of the Gulf of California, Sinaloa, México, during 15 months (February 2008-May 2009), were described. The mean initial shell height and body weight of seeds (n= 2,500) were 28.41 ± 4.69 mm and 0.3 ± 0.2 g, respectively. Pen shells were cultured in suspension for 4 months, and 11 months in bottom system until harvesting. Biometrics of 50 specimens were measured every month. The average final shell height and weight were 220.48 ± 12.41 mm and 284.26 ± 54.45 g, respectively. There were significant differences among the total weight of each month. The mean daily growth of shell height and body weight were 0.48 mm d-1 and 0.63 g d-1, respectively. Final survival was 88.72%. Results show that A. maura reached the commercial size (≥ 200 mm shell height) after 9 months of culture in Isla Los Redos, Sinaloa, Mexico. This information contribute with basic knowledge for further studies on farming of the pen shell A. maura.

El crecimiento y la supervivencia de bivalvos representan herramientas importantes para evaluar su cultivo. Se describe el crecimiento y la supervivencia del callo de hacha Atrina maura cultivado durante 15 meses (febrero 2008-mayo 2009) en Isla Los Redos, en la costa sureste del Golfo de California, México. El promedio inicial de la altura de la concha y el peso corporal de las semillas (n= 2500) fueron 28,41 ± 4,96 mm y 0,3 ± 0,2 g, respectivamente. Los organismos se mantuvieron 4 meses en suspensión y 11 meses sembrados en arena hasta la cosecha. Se realizaron biometrías de 50 especímenes cada mes. En promedio, los valores de crecimiento finales fueron de 220,48 ± 12,41 mm para la altura de la concha y 284,26 ± 54,45 g para el peso. Se encontraron diferencias significativas en el peso total durante la duración del cultivo. El promedio de la tasa diaria de crecimiento registró un valor de 0,48 mm d-1 y 0,63 g d-1 para la altura de la concha y el peso corporal, respectivamente. La supervivencia final fue de 88,72%. Los resultados muestran que A. maura alcanzó la talla comercial (≥ 200 mm) después de 9 meses de cultivo en Isla Los Redos, Sinaloa, México. Esta información contribuye con conocimiento básico para posteriores estudios en el desarrollo del cultivo de A. maura.

Evaluation of potential culture sites represents a `good practice' alternative to support the development of oyster industry at the northeast of Mexico. The relationship of growth, condition and survival of Crassostrea gigas with the environmental parameters was studied at the Navachiste-Macapule lagoon system (Sinaloa, Mexico) from November 2011 to November 2012. The culture was carried out using 2,520 small oysters (3.5 ± 0.5 mm shell height) in a suspended long-line system. The environmental parameters and oyster biometrics were sampled each 15 days. The mean values were: temperature= 25.01 ± 5.29°C, dissolved oxygen= 6.10 ± 1.93 mg L-1, salinity= 33.5, pH= 7.82 ± 0.39 and depth= 1.66 ± 0.55 m. The concentrations of total suspended solids, particulate organic matter and chlorophyll a fluctuated from 41.94 to 125.22 mg L-1, 8.91 to 15.22 mg L-1, and 13.36 to 3.69 mg m-3, respectively. After 13 culture months, the shell height reached 95.05 ± 9.21 mm, length 85.64 ± 20.01 mm, width 28.76 ± 10.91 mm, and the total weight 83.58 ± 17.18 g. The daily growth rate for the shell height and total weight were 0.25 mm day-1 and 0.23 g day-1, respectively. Significant differences were found for the total weight and the shell metric values throughout the culture. The final survival and mean condition index were 94.72% and 34.65 ± 4.46, respectively. Water temperature exerted a positive stronger effect on shell height and total weight. Results show that C. gigas reached the commercial size (80 mm SH) after 8 months of culture under the environmental conditions of the Navachiste-Macapule lagoon system, Sinaloa, Mexico. Obtained data contribute with basic information on further studies and commercial production cycles of this species in the region.

La evaluación de nuevos lugares con potencial de cultivo en la industria ostrícola representa una `buena práctica' que contribuye con el desarrollo de esta actividad en el noroeste de México. Se realizó un cultivo en suspensión (long-line) con el ostión Crassostrea gigas para estudiar la relación de su crecimiento, condición y supervivencia con las variables ambientales en el sistema lagunar Navachiste-Macapule (Sinaloa, México), de noviembre 2011 a noviembre 2012. Se utilizaron 2.520 semillas (3,5 ± 0,5 mm de altura de valvas). Las variables físicas y químicas del agua, y biométricas del ostión fueron registradas cada 15 días obteniendo los siguientes valores promedio: temperatura= 25,01 ± 5,29°C; oxígeno disuelto= 6,10 ± 1,93 mg L-1; salinidad= 32,88 ± 2.15; pH= 7,82 ± 0,39 y profundidad= 1,66 ± 0,55 m. Las concentraciones de sólidos suspendidos totales, materia orgánica particulada y clorofila a variaron de 41,94 a 125,22 mg L-1; 8,91 a 15,22 mg L-1 y 13,36 a 3,69 mg m-3, respectivamente. La altura de la concha alcanzó 95,05 ± 9,21 mm; la longitud 85,64 ± 20,01 mm; el ancho 28,6 ± 10,91 mm y el peso 83,58 ± 17,18 g. La tasa de crecimiento diaria del ostión fue de 0,25 mm día-1 para la altura de la concha y de 0,23 g día-1 para el peso. Se encontraron diferencias significativas en el peso total y en los valores métricos de las conchas. La supervivencia final fue de 94,72%, y el índice de condición promedio de 34,65 ± 4,46. La temperatura del agua ejerció un fuerte efecto positivo en la altura de las valvas y el peso total del ostión. Los resultados muestran que C. gigas alcanzó la talla comercial (80 mm de altura de las valvas) después de 8 meses de cultivo bajo las condiciones ambientales del sistema lagunar Navachiste-Macapule, Sinaloa, México. Los datos obtenidos contribuyen con información básica necesaria para futuros estudios y ciclos de producción comercial de esta especie en la región.