ABSTRACT Poecilia sphenops is a native species recently recorded in the Balsas basin and the Amacuzac River in Morelos (Mexico), in which it is abundant and widely distributed. This study analyzed some aspects of the reproductive biology of Poecilia sphenops from the Emiliano Zapata Reservoir, in Central Mexico. Specimens were collected using a 20 m-long seine with a 5 mm mesh size, from January to December 2006. A total of 581 specimens were collected: 407 females (70.0%), 83 males (14.3%) and 91 individuals with no differentiated sex (15.7%). Fish ranged from 20 to 96 mm in total length and 0.01 to 13.07 g in body weight. The female to male sex ratio (4.9:1) deviated significantly from the unity (χ2= 214.2, p<0.05). Monthly variations in gonadosomatic (GSI) and hepatosomatic (HSI) indexes and ovarian development stages showed that P. sphenops spawning season occurred between July and October, concurring with the rainy season. Another reproduction peak was registered in February. The largest length registered for males and females was 96 mm and 83 mm, respectively.

RESUMEN Poecilia sphenops es una especie nativa registrada recientemente en la cuenca del Balsas y el río Amacuzac en Morelos (México), en el cual es abundante y ampliamente distribuida. En este estudio se analizaron algunos aspectos de la biología reproductiva de Poecilia sphenops de la presa Emiliano Zapata, ubicada en el centro de México. Los especímenes fueron recolectados de Enero a diciembre de 2006, utilizando una red de 20 m de largo con una luz de malla de 5 mm. Se recolectaron un total de 581 especímenes: 407 hembras (70.0%), 83 machos (14.3%) y 91 individuos indiferenciados (15.7%). El tamaño de los peces osciló de 2 a 96 mm de longitud total y de 0.01 a 13.07 g de peso corporal. La proporción sexual de las hembras con respecto a los machos (4.9:1) se desvió significativamente de la unidad (χ2= 214.2, p<0.05). La variación mensual de los índices gonadosomático, hepatosomático y del desarrollo de los estadios de los ovarios, mostraron que la época de desove de P. sphenops se llevó a cabo entre julio y octubre, durante la época de lluvias. Otro pico de reproducción fue registrado en Febrero. La talla más grande registrada para los machos y para las hembras fue de 96 mm y 83 mm, respectivamente.

The dolphinfish Coryphaena hippurus, is one of the main species caught by the artisanal fisheries in the Tehuantepec Gulf, Mexico. Age was estimated by counting growth rings in the scales of 266 fish. Dolphinfish size ranged from 20 to 140 cm Fork Length (Lf). The length-weight relationship showed negative allometry in females and positive in males. The relationship between Lf and scale radius for combined data of both sexes was estimated as: Lf = 37.829 R + 3.8209 (r² = 0.8276). The estimated value of the Average Percent Error (1.3%) was considered acceptable. An annual periodicity was identified by a growth mark; marginal Increment Index indicated that a single annulus is formed yearly in April-May, which is related to the gonadosomatic index. Scales reading analysis allowed for the determination of up to four growth rings. Similar data was obtained from length frequency analysis by kernel density estimates. Results of von Bertalanffy's growth function obtained by simple non linear regression were: L∞ = 125.82 cm Lf, k = 0.9955 year-1, t o = -0.037 years for females, and L∞ = 126.29 cm Lf, k = 1.0 year-1, t0 = -0.0385 years for males. From the analysis of monthly length frequency distribution of 7371 dolphinfish, the values obtained were: L∞ = 166.5 cm, k = 1.1 year-1 for females, and L∞ = 167.7 cm, k = 1.3 year-1 for males. Longevity is estimated to be at least 4 years. No differences in growth were found between sexes. Estimated growth parameters were within the range of previous values reported for the dolphinfish at other latitudes and showed the rapid growth of the species.

El dorado Coryphaena hippurus, es una de las principales especies capturadas en la pesquería artesanal en el Golfo de Tehuantepec, México. Se estimó la edad mediante el conteo de anillos de crecimiento en escamas de 266 peces. La longitud furcal (Lf) varió entre 20 y 140 cm. La relación Lf-peso mostró una alometría negativa en hembras y positiva en machos. La relación Lf y radio de la escama para sexos combinados fue: Lf = 37,829R + 3,8209 (r² = 0,8276). El valor del Error Promedio Porcentual (1,3%) se consideró aceptable. Se identificó una periodicidad anual en las marcas de crecimiento; el incremento marginal indicó que el anillo se forma en abril-mayo y coincide con el inicio del desove. El análisis de escamas permitió identificar hasta cuatro anillos de crecimiento, valores similares fueron obtenidos por medio de los estimadores de densidad de Kernel. Los resultados de la ecuación de crecimiento de von Bertalanffy obtenidos por el método de regresión no lineal simple fueron: L∞ = 125,82 cm Lf, k = 0,9955 año-1, t o = -0,037 para hembras, y L∞ = 126,29 cm Lf, k = 1,0 año-1, t0 = -0,0385 para machos. Utilizando el análisis mensual de distribuciones de frecuencia-longitud de 7371 dorados se obtuvo L∞ = 166,5 cm, k = 1,1 año-1 para hembras y L∞ = 167,7 cm, k = 1,3 año-1 para machos. La longevidad estimada es de al menos cuatro años. No se encontró diferencia en el modelo de crecimiento por sexos. Los parámetros de crecimiento estimados se encuentran dentro del intervalo de valores reportados en otras latitudes y muestran el rápido crecimiento de la especie.

The Oaxaca coast in Mexico has a narrow continental shelf and it reaches depths greater than 500 meters near the coast; furthermore it consists of bays and sheltered areas, where high food availability is found. Each week, from March 2001 to December 2005, the unloading areas of artisanal fisheries between the bays of Huatulco and Puerto Escondido in the Oaxaca coast were visited. Data on fishing gear and zones, as well as the species composition of the captures were taken. In the zone, three fishery units operated: shark, pelagic and demersal. All three capture sharks in a direct or incidental way. At the studied region, 419 organisms of S. lewini were registered; from August to September newborn individuals (43.9%, 44 to 64 cm of total length), young of the year (9.3% 65-75 cm Tl) and juveniles (30.3%, 75 to 168 cm Tl) were observed; pregnant females were registered in March, May and June with a fecundity ranging from 18 to 24 embryos (35 to 45 cm Tl). With respect to C. falciformis, 1314 individuals were registered. Newborns (4.7%, 65-71 cm Tl) and young of the year (3.8%, 72 to 80 cm Tl) were observed from January to September; juveniles (65.4%, 80 to 170 cm Tl) were captured throughout the year; from January to November, 52 pregnant females were observed with embryos at different developmental stages. The presence of newborns, young of the year and pregnant females with embryos in advanced development condition, suggest that the coastal waters near the shoreline of the Oaxaca coast are a spawning and nursery area for these shark species