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 This research aims to evaluate the effect of molasses as a source of organic carbon on the growth and lipid profile of Dunaliella salina cultivated under different light regimes to determine its strategy and potential use to produce biodiesel. Two sources of nutrients (F/2 medium, F/2; molasses, M) and two light conditions (12 h light: 12 h darkness, 12L:12D) conformed four treatments (F/2 12L:12D, F/2 D, M 12L:12D, and MD) that were investigated with three replicates each. The concentration of microalgae produced by the groups under light conditions was more than double that of those grown in darkness. The highest biomass produced (46.91 ± 6.47 g L-1) was obtained in the F/2 medium with 12L:12D treatment, while the lowest (18.99 ± 0.78 g L-1) was in the M 12L:12D group. Regardless of the culture conditions, the lipids were mainly composed of the C16:0 and C18 fatty acids. The use of molasses as a culture medium produced the highest amount of C18:1, regardless of the light regime. Molasses promoted the highest production of fatty acids methyl esters. Depending on the culture medium, D. salina cells showed different percentages of saturated (SFA), monounsaturated (MFA), and polyunsaturated (PUFA) fatty acids. The highest amount of saturated fatty acids was obtained in F/2 12L:12D. The highest amount of polyunsaturated fatty acids was presented in the mixotrophic culture (molasses and light). The cultures grown with molasses were rich in monounsaturated fatty acids. An inexpensive industrial by-product, Cane molasses could be a low-cost feedstock for biodiesel in cultivating D. salina.

ABSTRACT The nutritional quality of tilapia fillet is characterized by low omega-3 polyunsaturated fatty acids (n-3 PUFAs). The objective of the present study was to evaluate the effect of different dietary concentrations of chia (Salvia hispanica) and flaxseed (Linum usitatissimum) meal on the omega-3 fatty acid content of tilapia (Oreochromis niloticus) fillet. Six experimental diets incorporating 5, 10, and 15% chia or flaxseed meals, respectively, were given to the fish (238.36 ± 7.61 g, initial weight) for 45 days before harvesting. The α-linolenic acid (ALA) and n-3 PUFA contents in the fillet differed significantly among diets (P < 0.05). Diets containing 15% chia or flaxseed meal had the highest concentrations of ALA (4.80 and 4.75%, respectively) and n-3 PUFA (13.65 and 15.92%, respectively). Thus, chia or flaxseed meal dietary inclusion increased the ALA and n-3 PUFA contents in the tilapia fillet. Chia or flaxseed meals are useful and potential alternatives to improve the nutritional value of O. niloticus fillets.

ABSTRACT Larkinia grandis (Broderip & G.B. Sowerby I, 1829), an important fishing resource for Mexican communities, is an Arcidae clam. It is also considered a species with aquaculture potential. In this work we investigated the gonadal phases and sexuality in a population of L. grandis in the Gulf of California. Our findings support the hypothesis that there is one male per female in the population studied. It also documents that the shape, position and color of the gonads of L. grandis are consistent with observations in other Arcidae species. Additionally, five gonadal phases are differentiated and described in males and females (development, mature, spawning, post-spawning and resting), with a noticeable presence of brown cells during post-spawning and the onset of the resting phase, suggesting that those cells are involved in the reabsorption of remnants. Additionally, asynchronous gametogenesis in males, synchronic gametogenesis in females and batch spawning are defined. The results of this contribution can be used in the efforts to protect this bivalve.

Resumen Introducción: El caracol marino Hexaplex nigritus es un murícido fuertemente explotado en el Golfo de California para consumo y artesanías. Cuando se reproducen, los adultos se agregan en forma de arrecifes artificiales facilitando su identificación y extracción, lo cual, ha mermado su población en dicha zona. Objetivo: Investigar el desove y desarrollo intracapsular y larvario de esta especie como herramientas para su producción en cautiverio con fines de repoblamiento. Métodos: Se recolectaron 18 progenitores que fueron mantenidos en un sistema cerrado con parámetros y alimentación controladas durante abril 2017 hasta septiembre 2018. Se registró: crecimiento de progenitores, desove de masas ovígeras, cantidad de cápsulas y número de embriones y larvas dentro de las cápsulas. La temperatura de incubación fue de 28.2 ± 1.5 °C. Las principales estructuras morfológicas de embriones y larvas fueron documentadas conforme su desarrollo. Resultados: El desarrollo embrionario intracapsular y de la larva velígera hasta su asentamiento tuvieron una duración de 14-15 y 31-32 días, respectivamente. Cada hembra de 80-88 mm de longitud produjo alrededor de 4 masas ovígeras, 627 cápsulas y 663 993 larvas velígeras extracapsulares por año. Conclusiones: La fácil adaptación y el potencial reproductivo mostrado por H. nigritus en laboratorio se presentan como estrategias promisorias para su repoblación y conservación.

Abstract Introduction: The marine snail Hexaplex nigritus is a heavily exploited muricid in the Gulf of California for consumption and handcrafts. When they reproduce, adults aggregated in the form of artificial reefs facilitating their identification and extraction, situation that has reduced their population in that area. Objective: In order to investigate the spawning and intracapsular and larval development of this species as tools for its production in captivity for repopulation purposes. Methods: Eighteen brooders were collected and kept in a closed system with controlled parameters and feeding from April 2017 to September 2018. Growth of parents, spawning of ovigerous masses, number of capsules, and number of embryos and larvae within the capsules, were registered. The main morphological structures of embryos and larvae were documented according to their development. Results: Intracapsular embryonic development and veliger larva until its establishment lasted 14-15 and 31-32 days, respectively. Each 80-88 mm length female produced around 4 ovigerous masses, 627 capsules and 663 993 extracapsular veliger larvae per year. Conclusions: Easy adaptation and reproductive potential shown by H. nigritus in the laboratory are presented as promising strategies for its repopulation and conservation.

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.

RESUMEN Objetivo. Detectar la presencia de presuntas hipnosporas del protozoario Perkinsus sp. en una población silvestre de la almeja chocolata mexicana (Megapitaria squalida) del sureste del Golfo de California, usando el medio fluido de tioglicolato de Ray (RFTM). Materiales y métodos. Cada mes durante un ciclo anual, se capturaron 30 especímenes con una longitud entre 56.17 y 69.04 mm. La prevalencia e intensidad de la infección y los parámetros del agua se registraron mensualmente desde septiembre 2012 a septiembre 2013. Resultados. Se detectó la presencia de presuntas hipnosporas de Perkinsus sp. en muestras de tejido de la almeja chocolata mexicana usando la prueba RFTM, por la presencia de corpúsculos redondos y oscuros que representan hipnosporas del parásito. Los muestreos mensuales revelaron un rango de prevalencia e intensidad de la infección de 0-43.33% y 1-4 (infección negativa = 0 hipnosporas/preparación, a moderada = 34 hipnosporas/ preparación), respectivamente. Conclusiones. Perkinsus sp. es reportado por primera vez en una población silvestre de M. squalida en la parte más al sureste del Golfo de California. Los resultados indican que el parásito está disperso intraespecíficamente y, potencialmente, parasitaría un nuevo huésped en la región.

ABSTRACT Objective. To detect the presence of presumptive hypnospores of the protozoan Perkinsus sp. in a wild population of the Mexican chocolata clam Megapitaria squalida in the southeastern Gulf of California, using Ray's fluid thioglycollate medium (RFTM). Material and methods. Thirty specimens with size between 56.17 and 69.04 mm were captured each month, during an annual cycle. Infection prevalence and intensity and water parameters were recorded monthly from September 2012 to September 2013. Results. Perkinsus sp. was detected in tissue samples from the Mexican chocolate clam using the RFTM test by the presence of dark round corpuscles that represent parasite's hypnospores. Monthly samplings revealed a prevalence of 0-43.33% and an infection intensity ranging from 1 to 4 (no infection = 0 hypnospores/entire preparation, to moderate = 34 hypnospores/entire preparation). Conclusions. Perkinsus sp. is reported for the first time in a wild population of M. squalida in the southesternmost Gulf of California. The results indicate that this protozoan is dispersed intraspecifically and would now, potentially, parasiting a new host in the region.

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 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 The trypsin enzyme of white shrimp Penaeus vannamei is a polymorphic molecule, which longest isolated and sequenced cDNA encoded a pre-proenzyme of 255 amino acids. Three of the described sequences are translated in the digestive gland, and SDS-PAGE detects the isoforms. The three isoforms named C, B and A are distributed by an individual to originate three trypsin phenotypes (CBA, CB and CA) that have already been isolated and characterized by defining theirs biochemical and kinetical differences. The CBA phenotypes exerted higher hydrolytic capabilities than the others. The trypsin phenotypes are inherited in a Mendelian fashion, and external or internal factors do not modulate them. In commercial hatcheries in Sinaloa, México, the most abundant phenotype was CBA, followed by CB and CA. The following two hypotheses may explain this finding: phenotype CA is not chosen throughout the selection process of breeders because they do not fit the anatomical characteristics desired by professionals in aquaculture or it is possible that shrimps with the CA phenotype die during the early stages of development. Two experimental designs were developed trying to explain such hypotheses and, in both experiments, CA phenotype frequency declined to zero when shrimps reached around 5 g of body weight. So far, no evidence explains the mortality of juvenile shrimps with phenotype CA. Research is needed to explain why CA phenotypes disappeared, how the survival of this phenotype can be improved, and how to produce shrimps with the most hydrolytic capability in support of the shrimp aquaculture industry.

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 This study aimed to determine weight-size relationships and to fit the best growth model of the Cortez oyster Crassostrea corteziensis from early juvenile to adult during one single culture cycle. The morphometric data (n = 50 oysters sampled each two weeks during January 2010 to March 2011) of shell height-shell length [SH-SL], shell height-shell width [SH-SW], shell width-shell length [SW-SL], body weight-shell length [BW-SL], body weight-shell height [BW-SH] and body weight-shell-width [BW-SW] (log-transformed) were determined by regression analysis. The SL and SH measurements (R2 = 0.98) were consistently proportional to the BW, being the BW-SL and BW-SH morphometric relationships the more suitable for growth evaluation of C. corteziensis in culture. Four different equations of the Schnute model, as well as Special cases 1 and 2 (equivalent to the Von Bertalanffy growth model, VBGM, and Logistic models, respectively), were evaluated utilizing length-at-age data to estimate individual growth parameters. The parameters were obtained using the maximum likelihood algorithm and the Akaike information criterion was applied to rank the models examined. The growth curve displayed a rapid increase until the size of 41.68 ± 16.18 mm in length. In the present study, the symmetrical sigmoid curve was the best hypothesis that fit the data; however, it is assumed that the age data are sufficiently informative to describe the growth pattern of C. corteziensis, with either Schnute model Special case 2. Results from morphometry and growth model in this study represent useful tools to analyze growth performance of the Cortez oyster in culture better.