The distribution, abundance, and ecology of larval tunas from the entrance to the Gulf of California

ENGLISH: This study is based on collections of larvae of Thunnus albacares, Euthynnus llneatus, and Auxis sp. obtained from surface and oblique net tows made during seven cruises, each along a comparable track in the entrance of the Gulf of California and each during a different month. Concomitant measurements of surface temperature, salinity, and zooplankton were made at each of the plankton stations. The catches of larval Auxis sp. were examined by analysis of variance techniques to determine which environmental features were associated with the spawning of this tuna as indicated by the distribution of larvae and to gain some insight into the behavior of the larvae themselves. The testing indicated that the spawning of Auxis sp. varied significantly among the different months of the cruises. The testing also indicated that if the larvae were capable of avoiding the sampling apparatus, this ability was not related to features associated with time of day such as light conditions. The analysis did not detect any change in the vertical distribution of the larvae among the months of the experiment. It was concluded that the larvae did not exhibit a diel vertical movement. The measurements of temperature, salinity, and zooplankton volumes were treated as covariates in the analysis. The surface temperature proved to be a highly important factor in explaining the distribution of larvae, but salinity and zooplankton volumes were not. Catches of Thunnus albaeares and Euthynnus lineatus were rare during the course of the study; these are discussed in qualitative terms with respect to the time of the year and the surface temperature. The distribution of larval tunas in the area of study was compared with the distribution of surface water masses. It appeared that these masses had no influence per se on the distribution of larvae. SPANISH: Este estudio está basado en las recolecciones de larvas de Thunnus albacares, Eutbynnus lineatus, y Auxis sp. obtenidas según los arrastres superficiales y oblicuos de la red, realizados durante siete cruceros, cada uno a la entrada del Golfo de California a lo largo de un derrotero comparable, y cada uno durante distintos meses. Las mediciones correspondientes de la temperatura superficial, salinidad y de zooplancton se realizaron en cada una de las estaciones de plancton. Las capturas de larvas Auxís sp. fueron examinadas mediante el análisis de la varianza para determinar cuales características ambientales se encontraban asociadas con el desove de este atún según lo indicaba la distribución de las larvas, y para obtener alguna idea del comportamiento de las larvas en sí mismas. Las pruebas indicaron que el desove de Auxis sp. varió significativamente entre los diferentes meses de los cruceros; indicaron también que si las larvas eran capaces de evitar el aparato de muestreo, esta habilidad no se relacionaba a las características asociadas con la hora del día de acuerdo a las condiciones de luz. El análisis no demostró ningún cambio en la distribución vertical de las larvas durante los meses del experimento. Se determinó que las larvas no exhiben un movimiento vertical diario. Las mediciones de temperatura, salinidad, y de los volúmenes de zooplancton fueron tratadas como covariables en el análisis. La temperatura superficial demostró ser un factor altamente importante en la explicación de la distribución de las larvas, pero la salinidad y los volúmenes de zooplancton no lo fueron. Las capturas de Thunnus albacares y Eutbynnus lineatus fueron pocas durante el curso de este estudio; éstas se discuten en términos cualitativos respecto a la época del año y a la temperatura superficial. La distribución de los atunes larvales en el área de estudio fue comparada con la distribución de las masas superficiales de agua. Parece que estas masas no tienen influencia per se en la distribución de las larvas. (PDF contains 40 pages.)

Hydrobiological studies of an irrigation tank with reference to the culture of large murrel, Channa marulius (Hamilton) and striped murrel Channa striatus (Bloch)

The importance of selection of species for culture according to the ecological niches and fish food organisms is highlighted with respect to the Fox Sagar, an irrigation take. The tank was infested with submerged vegetation as well as minnows and weed fishes, which rendered the tank unsuitable for the culture of Indian major carps. The tank was stocked with 8000 fingerlings of Channa marulius and C. striatus during 1981 by the local fisherman co-operative society. Only partial harvest was possible during 1982 because of high water level. The final harvest was in April-May, 1983. The yield obtained was 3640 kg during the culture period of about 20 months.

Keys to the larvae of the species of the genera Diamesa, Eukiefferiella, Orthocladius, Cricotopus, Psectrocladius and Chaetocladius. [Translation from: Larvae and pupae of midges of the subfamily Orthocladiinae of the fauna of the USSR (Diptera, Chironomidae = Tendipedidae) (ed. V.Y. Pankratova) p76-8,151-152,173-174,188-189. Leningrad, Nauka, 1970. ]

Eudiaptomus vulgaris Schmeil is the most abundant copepod in Lake Maggiore and forms also, in respect to other entomostraca, the most important element, through its average biomass and because it is fairly numerous throughout the year. Plankton samples collected in a systematic and quantitative way, gave the opportunity to study some aspects of the dynamics of the population of this copepod, in safety in view of the uncertainty which in this kind of study can ensue when samples are taken only at a single station - in consequence of the changes in size of population between different water masses. The results of the biometrical observations are of the population of Eudiaptomus vulgaris is presented.

A contribution to the algal flora of the Kola Peninsula [Translation from: Trudy Institut Botaniki Trudy Institut Botaniki Kharkivskii. Univ Vol. 4, pp. 53-76, 1941]

During recent years in connection with the industrialisation of the Kola Peninsula, the study of this district in the botanical respect, in particular the study of the microflora of various bodies of water, began to advance markedly. This article describes the algal flora of the Kola Peninsula. Morphological descriptions are given for three Tetraspora: Tetraspora simplex, Tetraspora tenera, Tetraspora imperfecta. Chlorophysema aduata is also described, and short descriptions of further algae found in the Kola Peninsula are given.

Studies on the optimum protein to energy ratio of African catfish (Clarias batrachus Burchell)

A laboratory trial was conducted to determine the optimum dietary protein to energy (P/E) ratio of African catfish, Clarias gariepinus. The experiment was carried out in a flow-through system for 6 weeks. There were 12 treatments each with two replicates having 10 fish each with a mean initial weight of 1.80 ± 0.02g. Twelve semi-purified diets were formulated with four digestible crude protein levels (23, 26.5, 30 and 33.5%) and three digestible energy levels (2.25, 2.75 and 3.25 Kcal/g). The fish were fed three times daily at satiation level. The results of the study showed that, diet containing 33.5% digestible protein and 2.75 kcal/g digestible energy with a protein to energy ratio of 121 .8 (mg protein/kcal) appeared to be best utilized for growth.