Reproductive Strategy of the Giant Electric Ray in the Southern Gulf of California

The objective of the present study was to describe and characterize macroscopic and microscopic aspects of the reproductive biology of the Giant Electric Ray Narcine entemedor, a viviparous elasmobranch targeted by commercial fishers in Mexico. A total of 305 individual rays were captured (260 females, 45 males); all males were sexually mature. The median size at maturity for females was estimated to be 58.5 cm TL, the median size at pregnancy was 63.7 cm TL, and the median size at maternity was 66.2 cm TL. The range of ovarian follicles recorded per female was 1–69; the maximum ovarian fecundity of fully grown vitellogenic oocytes was 17, and uterine fecundity ranged from 1 to 24 embryos per female. The lengths of the oblong ovarian follicles varied significantly among months, and the largest ovarian follicles were found in July, August, and September. Median embryo size was largest in August, and the size at birth was between 12.4 and 14.5 cm TL. Histological evidence of secretions from the glandular tissue of the uterine villi indicate that this species probably has limited histotrophy as a reproductive mode. Vitellogenesis in the ovary occurred synchronously with gestation in the uterus. The Giant Electric Ray has a continuous annual reproductive cycle; a period of ovulation occurs between May and September and two peaks of parturition, one in January and one in August, occur, suggesting that embryonic diapause occurs in some individuals. These results provide useful information for the management of this important commercial species in Bahía de La Paz, Mexico, and will allow possible modification of the current Mexican regulations to enable better protection of this species

Adiciones a la ictiofauna de Bahía de La Paz, Baja California Sur, México

One hundred thirty two news fish records are added to Bahía La Paz, making a total of 522 nominal species reported up to day. These records are based on net sampling (gill net enclosing and trawl net), observation of local fisheries activities, and from the identificaction of otoliths (sagitta) collected from sea lion's scats, Zalophus californianus. The shore fishes of Bahía La Paz is mainly conformed by Panamic elements, but the occurrence of northern elements confirm this area as transitional one.Se adicionan 132 nuevos registros de peces para la Bahía La Paz, y con ello se amplía a 522 el número total de especies nominales conocidas. Estos registros se basan en muestreos con redes (chinchorro y red de arrastre), observaciones sistemáticas en campos pesqueros, e identificación de otolitos provenientes de copros de lobo marino, Zalophus californianus. La ictiofauna nerítica de Bahía de La Paz está compuesta mayoritariamente por elementos Panámicos; sin embargo, la presencia de elementros de afinidad norteña confirman a esta área como de transición

Fetal mummification in silky shark (Carcharhinus falciformis) from the Gulf of California, Mexico

The aim of this work was the description of fetal mummification in silky shark. During July of 2001 in Santa Maria fishing camp, Gulf of California Mexico, fourteen pregnant female of silky sharks were captured. In all of them the embryos were found to be dehydrated. However, total observations were possible in only two litters. Six embryos in each analyzed litters were found. All the embryos were mummified, complete and without maceration. Because the litters were totally mummificated in several females, it was suggested that fetal mummification was produced by the environmental condition.<br>A mumificação fetal é caracterizada pela desidatração de embriões mortos dentro do útero da mãe. A perda de embriões pode afetar a sustentabilidade da população explorada, tornando o estudo deste fenômeno de suma importância. Em Julho de 2001 quatorze femeas grávidas do tubarão lombo preto foram capituradas durante uma amostragem no campo pesqueiro de Santa Maria, Golfo de California, México. Todas as fêmeas capturadas apresentaram embriões mumificados. Infelizmente, observações detalhadas dos embriões foram possíveis em apenas duas fêmeas. Cada fêmea analizada apresentava seis embriões, todos completamente mumificados e sem maceração. Embriões completamente mumificados foram encontrados em muitas fêmeas, o que sugere que a mumificação fetal desses embriões pode ter sido causada por condições ambientais