Marina V. Diaz

Maternal effects on fecundity and egg quality of the Patagonian stock of Argentine Hake (Merluccius hubbsi)

The influences of age, size, and condition of spawning females on fecundity and oocyte quality were analyzed for the Patagonian stock of Argentine Hake (Merluccius hubbsi). Samples of mature females were collected in the spawning area as part of 2 research surveys conducted in January 2010 and 2011, during the peak of the reproductive season. Batch fecundity (BF) ranged between 40,500 (29 cm total length [TL]) and 2,550,000 (95 cm TL) hydrated oocytes, and was positively correlated with TL, gutted weight, age, hepatosomatic index (HSI), and the relative condition factor (Kn). Relative fecundity ranged between 85 and 1040 hydrated oocytes g–1 and showed significant positive relationships with gutted weight, HSI, and Kn; however, coefficients of determination were low for all regressions. Dry weights of samples of 100 hydrated oocytes ranged between 1.8 and 3.95 mg and were positively correlated with all variables analyzed, including batch and relative fecundity. Multiple regression models created with data of the morphophysiological characteristics of females supported maternal influences on fecundity and egg weights. Within the studied size range (29–95 cm TL), larger individuals had better somatic and egg condition, mainly revealed by higher HSI and hydrated oocytes with larger oil droplets (275.71μm [standard error 1.49]). These results were associated with the higher feeding activity of larger females during the spawning season in comparison with the feeding activity of young individuals (<5 years old); the better nutritional state of larger females, assumed to result from more feeding, was conducive to greater production of high-quality eggs.

Employment of morphometric variables to assess nutritional condition of Argentine anchovy larvae Engraulis anchoita Hubbs & Marini, 1935

Las causas mas importantes de mortalidad larval son la depredacion e inanicion. Esta ultima puede ser estimada mediante el estudio de la condicion nutricional. El objetivo del presente estudio fue evaluar la condicion nutricional de larvas de E. anchoita empleando tecnicas morfometricas en tres areas del mar Argentino con diferentes caracteristicas hidrograficas para establecer variaciones regionales e interpoblacionales: area costera de El Rincon, Plataforma Continental y zona de frentes de marea de Peninsula Valdes. Las larvas provenientes de El Rincon presentaron una tasa de crecimiento mas elevada (pendiente de la curva de crecimiento = 3,575) pero menores indices de condicion de Fulton (15,71 ± 3,58, n = 41) y Le Cren (0,63 ± 0,13, n = 41) en comparacion con los especimenes recolectados en las otras dos zonas (P < 0,001). El analisis de componentes principales empleando variables morfometricas y el peso, mostro la separacion de larvas provenientes de El Rincon con respecto a otras capturadas en las restantes areas. Estos resultados podrian ser explicados como una consecuencia de un incremento en la mortalidad denso dependiente o por competencia por el alimento en el area de El Rincon debido a un ano en el que se registro una produccion larval excepcionalmente elevada. Nuestros resultados muestran que el uso de las variables morfometricas y el peso permiten hallar diferencias en la tasa de crecimiento y la condicion nutricional de las larvas de anchoita recolectadas en areas caracterizadas por escenarios oceanograficos diferentes.

The use of morphological and histological features as nutritional condition indices of Pagrus pagrus larvae

Morphometrical and histological techniques were employed to characterize Pagrus pagrus larvae nutritional condition. Larvae were reared in laboratory under controlled conditions with the main objective of testing whether these methodologies allowed finding differences between larvae from different feeding treatments. Once yolk was consumed (three days after hatching) larvae were assigned to a feeding treatment: starved during the whole experiment; delayed feeding, starved during three days; fed during the entire experiment. Algae (Nannochloropsis oculata) and rotifers (Brachionus plicatilis) were provided to larvae for feed treatments. Larvae were fixed daily; for morphometrical purposes in 5% formaldehyde solution, and in Bouin for histological sections. Results herein obtained showed that both methodologies are sensitive enough to distinguish larvae characterized by different nutritional condition states obtained from the feeding treatments. Consequently, these methodologies could be employed in wild red porgy larvae in order to asses their nutritional condition. These techniques could also be employed to check larval quality obtained with aquaculture purposes to estimate the effects of changes in rearing protocols or kind of food supply and thus, to guaranty a higher survival of early developmental stages of reared larvae.

Descripción micro-anatómica de las larvas de Engraulis anchoita y su aplicación en estudios de condición nutricional

Diverse indices have been used to characterize the nutritional condition of fish larvae. Histological criteria were shown to be reliable in diagnosing nutritional condition, because they involve the study of cellular aspect, structure and tissular integrity. However, since the microscopical appearance of larval tissues varies both as a consequence of nutritional status and developmental stages, it becomes necessary to characterize the employed structures and to take into account the developmental stage of the studied specimen. The aim of this study was to develop a typical micro-anatomical description to assess the nutritional condition of Engraulis anchoita fish larvae collected in the Argentine Sea. Several tissues were diagnosed to calculate a histological condition index (ICH) in regards to anchovy larvae ontogeny. In addition, the tissues analysed were divided into short and long-term indices. A reduction of HCI was observed during yolk exhaustion and at the end of the larval stage. In order to detect slight changes in histological condition, short term tissues proved to be more sensitive to starvation than long term tissues.