Abstract One of the main problems to be solved in the commercial production of Nile tilapia is the use of large volumes of steroids during the sex reversion process. The precise evaluation of the time after hatching to start the steroid treatment could help reduce its use in the short-term. The main objective of this work was to evaluate the sex proportion and the growth obtained in a mixed population of Nile tilapia fed fluoxymesterone at different days (3, 6, 9, 12, and 15) after hatching. A one-factor experiment was designed, with the day, after hatching, that the fluoxymesterone (5 mg) began to be supplied as factor (3, 6, 9, 12 and 15). Initial stocking density was 0.4 larvae L-1. All groups were evaluated by triplicate. Steroid treatment finished at day 25 after larvae stocking. Squash technique was used to determine sex proportion at the end of the experiment (45 days). Growth evaluation was performed based on wet weight and total length obtained from each biometry. The results showed the highest percentage of males (92%) in the fish fed fluoxymesterone from day three after hatching. No anabolic effect on growth was observed in any steroid-treated fish. A negative effect on growth was observed after withdrawal of the steroid in the fish that were fed fluoxymesterone for the longest time. These results show that it is necessary to supply the fluoxymesterone prior to the onset of sex differentiation (5-6 days after hatching) to achieve a permanent reversion of the sex differentiation process.

Abstract Objective: To identify the acceptance, the profile of the potential consumer and the assessment of the willingness to pay for products derived from the Nile tilapia in the regions of the state of Oaxaca. Methodology: Through a binomial logistic regression model, it was proposed to examine the willingness to pay (WTP) for two attributes of sausege Nile tilapia (free of hormones and high nutritional value). Results: The empirical results show a WTP for consumers whose monthly income is estimated to be above 20,000 pesos. Being precisely these two attributes the most valued by respondents, in the background the preference to acquire a 100% Oaxacan product and with only a variation of 2% for each $ 10.00 MX, the price can be mentioned. Limitations: One of the limitations of the model is that it does not allow observing the effect of the different categories of the variables age and education, for example, which of the different categories of education is significant and which is not. Conclusions: The target market for products derived from Nile tilapia are families whose income ranges between 10,000 and 15,000 Mexican pesos, who prefer to buy sausages in bulk, nutritious, without chemical preservatives and with a 100% Oaxacan brand.

Resumen Objetivo: Identificar la aceptación, el perfil del consumidor potencial y la valuación de la disposición a pagar para productos derivados de tilapia del Nilo en las regiones del estado de Oaxaca. Metodología: A través de un modelo de regresión logística binomial se propuso examinar la disponibilidad a pagar (DAP) para dos atributos de embutidos de tilapia (libre de hormonas y alto valor nutricional). Resultados: Los resultados empíricos muestran una DAP para los consumidores cuyos ingresos quincenales se estiman por arriba de 10,000 pesos. Son, precisamente, estos dos atributos los más valorados por los encuestados. En un segundo plano puede mencionarse la preferencia de adquirir un producto cien por ciento oaxaqueño. Respecto a la respuesta al precio, la variación porcentual es de 2%, lo que implica que ante un aumento en el precio de 10 pesos la demanda bajará solo 2%. Limitaciones: Una de las limitaciones del modelo es que no permite observar el efecto de las diferentes categorías de las variables edad y escolaridad, por ejemplo, ¿cuál de las diferentes categorías de escolaridad es significativa y cuál no lo es? Conclusiones: El mercado objetivo para los productos derivados de tilapia del Nilo son familias cuyos ingresos oscilan entre los 10,000 y 15,000 pesos mexicanos, quienes prefieren la compra de los embutidos a granel, nutritivos, sin conservadores químicos y con origen cien por ciento oaxaqueño.

RESUMEN Una alternativa para reducir el uso de hormonas con aplicación inmediata en el cultivo comercial de la tilapia del Nilo, es la evaluación precisa de los tiempos de masculinización en variedades domesticadas. El objetivo del trabajo fue evaluar el porcentaje de masculinización y el crecimiento obtenido en la tilapia del Nilo alimentada con alimento comercial adicionado con 17ɑ-metiltestosterona a diferentes tiempos. Para ello se evaluaron cinco tiempos (0, 10, 15, 20 y 25 días) de administración de hormona a una población mixta de tilapia del Nilo variedad Spring. Para cada tratamiento se utilizaron tres réplicas. Los alevines fueron sembrados a densidad de 0.5 alevines L-1 en un sistema de recirculación cerrado. El cultivo consistió de 30 días en acuarios de acrílico de 85 L y 20 días en tanques exteriores de 1000 L. La determinación del sexo se realizó con la técnica de squash. El crecimiento se determinó por medio del peso húmedo y la longitud total obtenida de las biometrías. Los resultados indican una masculinización del 100% desde los 10 días de aplicación del esteroide, pero los mayores valores de crecimiento se observaron en los grupos que recibieron el esteroide por mayor tiempo. Los resultados muestran que no es necesario administrar el esteroide durante 30 días para lograr una masculinización del 100% en variedades domesticadas y que el esteroide tiene efecto positivo en la tasa de crecimiento de los alevínes, persistiendo por algunas semanas después de terminado el tratamiento.

ABSTRACT An alternative to reduce the use of hormones with an immediate application to Nile tilapia commercial culture, is the precise evaluation of masculinization duration in domesticated strains. The main objective of this work was to evaluate the percentage of masculinization and growth obtained in Nile tilapia fed with 17ɑ-methyltestosterone at different times during the fry period. For this, five times (0, 10, 15, 20 and 25 days) of application of the hormonal treatment were evaluated in a mixed population of Nile tilapia’s Spring strain. For each treatment, three replicates were used. Fry were stocked at a density of 0.5 L-1 in a recirculation system. Culture consisted of 30 days in 85 L acrylic aquaria and another 20 days in 1000 L exterior tanks. Squash technique was used for determination of sex. Growth was determined from wet weight and total length obtained in the biometrics. The results obtained indicated a 100% masculinization after 10 days of steroid application; but, the highest values in terms of growth rates were observed in the groups that received the steroid for the longest time. The results show that it is not necessary that the steroid is administered for 30 days to achieve a 100% masculinization in a domesticated line and that the steroid has a positive effect on the growth of the fry which persists for a few weeks after the end of the treatment.

ABSTRACT The use of water temperature to modify sex proportion in Nile tilapia has been suggested as an alternative to eliminating the use of steroids since it was discovered that it has an important role in the sex differentiation process. However, the use of cold-water temperatures to achieve feminization has rarely been explored and never has it been combined with exogenous estrogens. This work aimed to determine if the proportion of females could be increased by combining low concentrations of estrogens with a cold-water temperature, and describing its effect on growth parameters, gonadosomatic index, and fat muscle content. Two experiments were carried out, each one set at a specific water temperature (27.5 and 21.5°C). In each experiment four treatments (per triplicate) were evaluated (control -no estrogens-, estradiol-17β E2, 17α-ethinylestradiol EE2 and diethylstilbestrol DES). Higher feminization rates were observed in all groups, including the control group, reared at 21.5°C. Growth parameters showed significantly higher values (P < 0.05) for the groups reared at 27.5°C. The control group and the group fed E2 reared at 21.5°C showed significantly higher (P < 0.05) values of gonadosomatic index than that observed in the groups reared at 27.5°C. Fat muscle content was significantly higher (P < 0.05) in both experiments for the groups fed E2 and EE2. The fry used showed a high tendency towards feminization by exposure to a cold-water temperature. Our results allow us to consider E2 (21.5°C) the best option for the development of YY technology.

ABSTRACT YY technology has been developed in response to the demand of environment-friendly techniques to produce all-male populations in Nile tilapia culture. However, the first part of this technique still requires feminization of XY fry. Use of estrogen mixtures to achieve feminization has never been tested in Nile tilapia, so the aim of this study was to evaluate the effect of different combinations of the three most important estrogens (17β-estradiol E2, diethylstilbestrol DES, and 17a-ethinylestradiol EE2) on sex proportion, growth, and gonadal development. Mixtures evaluated were E2-DES, E2-EE2, DES-EE2, and E2-DES-EE2. No significant differences in growth were observed at the end of the experiment between control fish and fish fed estrogen mixtures. However, final survival was significantly lower (P < 0.05) in fish fed E2-DES and E2-DES-EE2. All estrogen mixture-treated groups produced progenies with a significantly higher (P < 0.001) proportion of males than the predicted 1:1 sex ratio. No significant differences were observed in gonadosomatic index between fish of the control group and fish fed estrogen mixtures. The proportion of deformed gonads was higher in groups fed E2-DES and E2-DES-EE2. The paradoxical masculinization observed in all estrogen mixtures was probably provoked by the interaction of estrogens with androgen receptors or the inhibition of aromatase expression, which resulted in testosterone accumulation and testis development. These results address the need for further research towards understanding the role of steroids in sexual development since these findings add to a short list of studies that report paradoxical effects after using steroids.

Hormonal induction of spotted sand bass Paralabrax maculatofasciatus, was investigated in order to induce and synchronize spawning. Three experiments were conducted using wild fish captured in the Gulf of California: 1) LHRHa (luteinizing hormone-releasing hormone analogue) induced spawning with concentrations of 25, 50, 100 μg kg-1 and saline solution, 2) Effects of LHRHa on motility and sperm density, and 3) Induction and incubation of spawns obtained using LHRHa. In experiments 2 and 3 using concentrations of 12.5, 25, 50 μg kg-1 and saline solution. In experiment 1, a higher spawning ratio was observed for the concentration of 25 μg kg-1; however, no significant differences were observed in the proportion of floating (viable) eggs. In experiment 2, significant differences (P < 0.05) were observed in duration of sperm motility and sperm density, with highest duration registered for wild fish (control group) and highest density registered for laboratory control group and concentration of 12.5 μg kg-1. In experiment 3, significant differences (P < 0.05) were observed between treatments in volume of spawned eggs and proportion of fertilized eggs, with higher values shown for the concentrations of 50 and 12.5 μg kg-1, respectively. Survival at hatching and proportion of live yolk-sac larvae were significantly higher (P < 0.05) for the concentration of 12.5 μg kg-1. LHRHa was effective in inducing and synchronizing the spawning of spotted sand bass, a process which will be used for massive egg production.

Se analizó la inducción hormonal en la cabrilla arenera Paralabrax maculatofasciatus, para inducir y sincronizar el desove. Se desarrollaron tres experimentos utilizando peces capturados en el Golfo de California: 1) Inducción al desove con LHRHa, usando concentraciones de 25, 50, 100 μg kg-1 y solución salina, 2) efectos del LHRHa sobre la motilidad y la densidad espermática, y 3) inducción e incubación de desoves obtenidos con LHRHa. En los experimentos 2 y 3 se utilizaron concentraciones de 12.5, 25, 50 μg kg-1 y solución salina. En el primer experimento se observó una proporción de desoves más elevada utilizando la concentración de 25 μg kg-1, pero, no se observaron diferencias significativas en la proporción de huevos flotantes (viables). En el segundo experimento se observaron diferencias significativas (P < 0.05) en la duración de la motilidad y densidad espermáticas, con la mayor duración en peces silvestres (grupo control), y la mayor densidad en el grupo control de laboratorio a una concentración de 12.5 μg kg-1. En el tercer experimento se observaron diferencias significativas (P < 0,05) en el volumen de huevos desovados y proporción de huevos fertilizados, con los mayores valores en las concentraciones de 50 y 12,5 μg kg-1, respectivamente. La supervivencia a la eclosión y proporción de larvas vitelinas vivas fue significativamente mayor (P < 0,05) en la concentración de 12,5 μg kg-1. El LHRHa fue eficaz para inducir y sincronizar desoves de cabrilla arenera utilizados para la producción masiva de huevos.

Abstract: Three experiments assessed the effects of cold-shock induced triploidy on (1) the incidence of abnormal cell cleavage during embryogenesis, (2) hatching success and the proportion of live yolk-sac larvae in normally cleaved versus abnormally cleaved embryos, and (3) survival of triploid larvae of spotted sand bass (Paralabrax maculatofasciatus). All spawns were obtained by hormonal induction (LHRHa). Triploidy was induced by cold shock shortly after fertilization. In experiment 1, the percentage of abnormal cell cleavage was significantly higher (P < 0.05) in the cold-shocked group than in the control group, while the hatching rate and the proportion of live yolk-sac larvae were significantly lower (P < 0.05). In experiment 2, when normally and abnormally cleaved embryos from the control and cold-shocked groups were incubated separately, normal cleaved embryos in the cold-shocked group showed a significantly higher hatching rate and proportion of live yolk-sac larvae than abnormally cleaved embryos in the same group. No difference was observed in the control group. In experiment 3, a significant decrease (P < 0.05) in the triploidy count was observed throughout the larval period. Final survival was drastically lower for triploid larvae compared to cold-shocked diploids and untreated eggs. Low triploidy percentages at the end of the larval period would seriously hinder the development of triploid sand bass culture.

Resumen: Se realizaron 3 experimentos para evaluar los efectos de la triploidía inducida por choque frío sobre (1) la incidencia de división celular anormal durante la embriogénesis, (2) la tasa de eclosión y la proporción de larvas vitelinas vivas en los embriones con división celular normal contra los embriones con división anormal y (3) la supervivencia de larvas triploides de la cabrilla arenera (Paralabrax maculatofasciatus). Los desoves se obtuvieron por inducción hormonal (LHRHa). La triploidía se indujo por choque frío poco después de la fecundación. En el experimento 1, el porcentaje de embriones con división anormal fue significativamente más alto (P < 0.05) en las larvas tratadas con choque frío que en el grupo control, mientras que la tasa de eclosión y la proporción de larvas vitelinas vivas fueron significativamente más bajas (P < 0.05). En el experimento 2, cuando los embriones con divisiones normales y anormales de ambos grupos fueron incubados por separado, los embriones con divisiones celulares normales en el grupo de choque frío presentaron una tasa de eclosión y una proporción de larvas vitelinas vivas significativamente más altas que los embriones con división celular anormal del mismo grupo. No se observaron diferencias en el grupo control. En el experimento 3, se observó una disminución significativa (P < 0.05) en la cantidad de triploides a lo largo del periodo larvario. La supervivencia final fue drásticamente menor para las larvas triploides en comparación con las larvas que resultaron diploides después del choque frío o que no recibieron tratamiento. Los bajos porcentajes de triploides al final del periodo larvario limitan el desarrollo del cultivo de la cabrilla arenera triploide.

Sex-reversal by exogenous hormones is the most common technique used to generate monosex populations of Nile tilapia (Oreochromis niloticus). However, this technique has provoked a negative perception in recent years. Because of this, alternative techniques have been developed, including the production of YY males. Although the final product (for sale) is not administered hormones, the first part of this technique still requires the feminization of XY fry by use of estrogens, including some of a synthetic nature, such as diethylstilbestrol (DES), an estrogen that has shown particularly excellent results in related species. The aim of this study was to evaluate the effect of increasing concentrations of DES (100, 200, 300, and 400 mg kg-1) during the fry stage on the sex proportion, growth and gonadosomatic index (GSI) of Nile tilapia. The 400 mg kg-1 concentration was the one that produced the highest proportion of females (91 %). However, increasing the concentration of DES provided through diet does not guarantee a 100 % feminization rate. Additionally, the growth, survival and GSI, showed a significant decrease (p < 0.05) in all groups fed with DES compared to the control group. It is possible that the anabolic effect of DES observed in other species is not present in Nile tilapia.

La reversión sexual a través de hormonas exógenas es la técnica más usada para obtener poblaciones monosexo de tilapia del Nilo (Oreochromis niloticus). Sin embargo, esta técnica ha generado una percepción negativa en los últimos años. Debido a lo anterior, se han desarrollado técnicas alternativas incluyendo la producción de machos YY. Aunque con esta técnica el producto final (para vender) no recibe hormona, la primera parte de esta técnica aun requiere la feminización de alevines XY a través de estrógenos, incluyendo algunos de naturaleza sintética como el dietilestilbestrol (DES), el cual ha mostrado excelentes resultados en especies relacionadas. El objetivo del presente trabajo fue evaluar el efecto de concentraciones crecientes de DES (100, 200, 300, 400 mg kg-1) durante el periodo de alevín en la proporción de sexos, crecimiento e índice gonadosomático (IGS) de la tilapia del Nilo. La concentración de 400 mg kg-1 fue la que arrojó la mayor proporción de hembras (91 %). Sin embargo, incrementar la concentración de DES proporcionada a través de la dieta no garantiza una feminización del 100 %. Adicionalmente, el crecimiento, la supervivencia y el IGS, mostraron un descenso significativo (p < 0.05) en todos los grupos alimentados con DES, en comparación con el grupo control. Es posible que el efecto anabólico del DES observado en otras especies no este presente en la tilapia del Nilo.

ABSTRACT. Triploidy has become a recommended tool for aquaculture since problems associated with gonadal maturation can be eliminated or reduced by producing triploid fish, which are functionally sterile. Although the possibility of sterilizing a large number of individuals has helped for triploidy to become an important issue economically, the physiological changes caused by the addition of a third set of chromosomes provides the opportunity to study basic processes in fish with a higher ploidy status. At physiological level the consequences of triploidy are closely related to the increase of cell size and its subsequent impact on various metabolic and biochemical processes. The aim of this work is to describe the main physiological consequences reported for marine and freshwater fishes resulting from the induction of triploidy. Understanding these consequences is of vital importance to maximize the performance of triploid fish under culture.

RESUMEN. La triploidía se ha convertido en una herramienta recomendable para la acuicultura, ya que los problemas asociados con la maduración gonadal pueden ser eliminados o bien reducidos mediante la producción de peces triploides, los cuales son funcionalmente estériles. Aunque la posibilidad de esterilizar una gran cantidad de individuos ha convertido a la triploidía en un tema relevante económicamente, los cambios fisiológicos provocados por la adición de un tercer juego de cromosomas, ofrecen la posibilidad de estudiar procesos básicos en peces con diferente nivel de ploidía. A nivel fisiológico, la triploidía está estrechamente relacionada con el incremento del tamaño celular y sus repercusiones en varios procesos metabólicos y bioquímicos. El objetivo del presente trabajo es describir las principales consecuencias fisiológicas reportadas para peces marinos y dulceacuícolas, resultado de la inducción a la triploidía. Comprender estas consecuencias es de vital importancia para maximizar el desempeño de los peces triploides durante el cultivo.

Early maturity during tilapia culture is a recurring problem. To avoid this, a series of techniques have been developed, including the production of YY-males. This technique involves the use of hormones to produce phenotypic females (XY genotype). However, incomplete transformations are frequently observed and the produced atypical feminized males (AFM) could display an ambiguity in the phenotypic expression of behavioral patterns. The aim of this study was to measure the frequency and intensity of aggressive behavior as well as the role that initial residence plays when involving three phenotypes (males, females and AFM). The experiment consisted of three stages. Resident fish were AFM in the first stage, males in the second and females in the third. In each stage the resident fish confronted males, females and AFM acting as intruders. Aggressive behavior was exercised more frequently by resident fish. Intersexual confrontations showed higher levels of aggression compared to intrasexual confrontations. The frequency of confrontations was not significantly different in confrontations involving AFM, however, differences were observed in intensity of aggression. It is possible that an incomplete transformation at physiological level could be responsible for an inaccurate decoding of signal during confrontations.

La madurez temprana durante el cultivo de tilapia es un problema recurrente. Para evitarlo, existe una serie de técnicas, incluyendo la producción de machos-YY. Esta técnica implica el uso de hormonas para producir hembras fenotípicas (genotipo XY). Sin embargo, son frecuentes transformaciones incompletas y los machos feminizados atípicos (MFA) producidos podrían mostrar ambigüedad en la expresión fenotípica de los patrones de comportamiento. El objetivo del presente trabajo fue determinar la frecuencia e intensidad del comportamiento agresivo, así como el papel que juega la residencia inicial al involucrar tres fenotipos (machos, hembras y MFA). El experimento abarcó tres etapas. En la primera etapa, MFA actuaron como residentes, en la segunda machos, y en la tercera, hembras. En cada etapa el residente enfrentó a machos, hembras y MFA que actuaron como intrusos. El comportamiento agresivo lo ejercieron con mayor frecuencia los peces residentes. Las confrontaciones intersexuales mostraron mayores niveles de agresión en comparación con las intrasexuales. La frecuencia de confrontaciones no fue significativamente diferente en confrontaciones que incluyeron MFA, sin embargo, se observaron diferencias en la intensidad de la agresión. Es posible que una transformación incompleta a nivel fisiológico pueda ser responsable de una decodificación incorrecta de señales durante las confrontaciones.

Abstract Conditions for the feminization of undifferentiated XY fry of Nile tilapia (Oreochromis niloticus) fed on a diet supplemented with estradiol-17β (E2) were investigated in order to produce functional phenotypical females (genetic males). Different E2 concentrations (60 and 120 mg kg-1) were tested over a period of 30 days in a closed recirculating system. Fry were fed ad libitum at 1-h intervals. The effects on growth, gonadal development and body composition were evaluated at sexual maturity. Sex-reversed females were produced in both E2 treatments. The proportion of males was significantly lower (p < 0.05) in both E2 treatments compared to the control group. Fish with atypical papilla and normal ovaries were produced in both E2 concentrations. These fish were considered sex-reversed females. Growth was significantly higher (p < 0.05) in the males compared to both the females and the sex-reversed ones in all groups analyzed. No testicular tissue was observed in any of the ovaries of the sex-reversed females analyzed. The percentage of fat in muscle increased and that of protein decreased significantly (p < 0.05) in the sex-reversed females compared to that observed in the control group. Identified sex-reversed females will be used in the production of YY males through mating with normal males, as part of a developing breeding program to produce a male genetic population in the southern region of Mexico.

Resumen Se investigaron las condiciones para la feminización de alevines XY de la tilapia del Nilo (Oreochromis niloticus) a través de una dieta suplementada con estradiol-17β (E2) con la finalidad de producir hembras fenotípicas funcionales (machos a nivel genético). Se pusieron a prueba dos concentraciones de E2 (60 y 120 mg kg-1) durante 30 días en un sistema de recirculación cerrado. Los alevines fueron alimentados ad libitum a intervalos de 1-h. Los efectos sobre el crecimiento, el desarrollo gonadal y la composición corporal fueron evaluados a la madurez sexual. Se observó una disminución significativa (p < 0.05) en la proporción de machos en los grupos tratados con E2, en comparación con el grupo control. Se detectaron peces con papilla genital atípica y ovarios normales en ambas concentraciones de E2. Estos peces se consideraron hembras revertidas. El crecimiento fue significativamente mayor (p < 0.05) en los machos, en comparación con las hembras normales y las hembras revertidas en todos los grupos analizados. No se observó tejido testicular en ninguno de los ovarios de las hembras revertidas analizadas. El porcentaje de grasa en músculo aumentó, mientras que el de proteína disminuyó significativamente (p < 0.05) en las hembras revertidas, en comparación con lo observado en el grupo control. Las hembras revertidas identificadas se utilizarán en la producción de machos YY mediante su cruza con machos normales, como parte de un programa de cría para la producción de poblaciones compuestas al 100% por machos genéticos en la región sur de México.

Successful YY technology depends on the production of XY females. However, their identification is complicated because they are indistinguishable from normal females. Atypical fish could offer an alternative for a more rapid and precise identification. Progeny of atypical fish was evaluated in order to produce YY-males. In total, nine atypical fish and 18 normal males were selected. The fish were placed in 8 m³ concrete tanks at a 2:1 sex ratio. The produced fry were collected and reared at 28 ± 1°C in 85 L aquaria. Juveniles were placed in net cages for 30 days and finally in 8 m³ concrete tanks until the age of 120 days. Progeny test was achieved evaluating differences between sexes in the genital papilla structure. Six of the nine atypical fish selected showed the 3:1 sex ratio (male-female) expected for sex-reversed females. A significantly higher proportion of males than the expected 3:1 distribution were observed in two atypical fish. This boost in male proportion could be attributed to a parental effect interacting with the water temperature during the fry stage. Use of atypical fish could help reduce the time and effort spent to identify XY females during the initial stage of YY technology.

La aplicación exitosa de la tecnología YY depende de la producción de hembras XY. Sin embargo, su identificación es complicada, ya que son indistinguibles de las hembras normales. Los peces atípicos podrían ofrecer una alternativa para una más rápida y precisa identificación. Se evaluó la progenie de nueve peces atípicos con la finalidad de producir machos YY. Los alevines obtenidos se criaron a 28 ± 1°C en acuarios de 85 L. Los juveniles fueron colocados en jaulas flotantes por 30 días y, finalmente, en estanques de 8 m³ hasta los 120 días de edad. La prueba de progenie se realizó evaluando las diferencias entre sexos en la estructura de la papila genital. Seis de los nueve peces atípicos seleccionados mostraron la proporción de sexos 3:1 (macho-hembra) esperada para hembras revertidas. Se observó una proporción de machos significativamente mayor a la distribución 3:1 esperada en dos peces atípicos. Este aumento en la proporción de machos puede ser atribuido a la interacción del efecto parental con la temperatura del agua durante la etapa de alevín. El uso de peces atípicos podría reducir el tiempo y esfuerzo empleados en la identificación de hembras XY durante la etapa inicial de la tecnología YY.