Growth response of Heterobranchus longifilis (Valenciennes, 1840) fingerlings fed raw and boiled Mucuna cochinchinensis seed meal

Feeding trial was conducted in static water to assess the growth of H. longifilis fingerlings fed different I inclusion levels of mucuna seed meal (MSM). Raw and boiled MSM were used in the diets at 10%, 20%, 30% and 40% inclusion levels and the performance of fish fed these diets was compared with fish fed a fishmeal-based diet which contained 40% protein. All diets were prepared to be isonitrogenous and isocaloric A two by five factorial experiment with three replicates using ten fish of average initial weight 1 .46g was carried out. Daily fish ration of five percent body weight was administered two times for eight weeks. The specific growth rate in diets 1 (control) and 6(10% boiled MSM) were similar and significantly (P<0.05) higher than the other dietary groups. The significantly lower growth performance of fish fed diets containing higher inclusion levels of both raw and boiled MSM might be due to incomplete elimination of the antinutritional factors present in MSM by boiling. Other methods of processing MSM to improve its nutritive value should be investigated. (7 page document)

Lago Pellegrini. Caracteristicas limnologicas

Este trabajo trata el estudio biológico del lago Pellegrini y las características limnológicas del ambiente desde el punto de vista pesquero y turístico en el lapso 1980-1998. Se realizaron monitoreos quincenales de calidad de agua y mensuales de plancton, plaguicidas, bacteriológicos, etc. en estaciones de muestreo situadas en el lago propiamente dicho, en el afluente y alrededores. Se analizan los problemas de eutrofización presentes, en la búsqueda de ensayos que disminuyan el deterioro del ecosistema. Los resultados comprueban un proceso de eutrofización natural, agravado por la actividad humana, con florecimientos de algas cianobacterias (Géneros Microcystis y Anabaena) y una disminución de la productividad secundaria y en la población íctica.

Efectos de la eutrofizacion sobre la pesca en el lago Pellegrini.

Por los problemas ocasionados en el deterioro del lago, en la pesca comercial y deportiva, se planteó como objetivo el estudio de las características limnológicas del ambiente relacionando la situación actual con la de años anteriores y además con los aportes exógenos que recibe el ecosistema. Se realizaron monitoreos de calidad físico-química del agua, nutrientes y plancton del lago y su influencia sobre el recurso pesquero, relacionando las capturas reales con los altos rendimientos pesqueros teóricos determinados en base a parámetros químicos, biológicos y morfoedáficos. Los resultados comprueban una disminución de la productividad secundaria y la población de peces, entre otros problemas de eutrofización. Se estudian distintas posibilidades para revertir esta tendencia del lago y recuperar e impulsar la pesquería comercial y deportiva.

Induced diploid meiogynogenesis in the African clariid catfish Heterobranchus longifilis (Valenciennes, 1840) (Pisces: Clariidae)

Diploid meiotic gynogenesis was induced in African catfish, Heterobranchus longifilis by injection of 0.5ml/kg ovaprim on the breeders, followed by application of UV light irradiation on the spermatozoa and temperature shocking of activated eggs. Diploidy was restored by shocking haploid activated eggs at 5 degree C for 40 minutes. The normal control spermatozoa did not receive any UV irradiation nor temperature shock, while the haploid control spermatozoa were irradiated, but did not receive cold shock. The percentage hatchability in the treated group was 25%, while in the control it was 53%. Less than 15 fingerlings had morphological aberrations. After two weeks of indoor rearing, the survival percentage of the treated group was 45% in the control experiment. Cytogenetic analysis of chromosomes revealed 25 chromosomes in the haploid embryo and 50 chromosomes each in diploid gynogenesis and normal diploid control

Embryogenesis of Heterobranchus longifilis (Curvier and Valenciennes, 1840)

Studies on development of H. longifilis (Curvier and Valenciennes, 1840) were conducted at a temperature of 25EC ( 1Ec) in aquaria tanks continuous development were monitored with the use of wild Heerbrugy photomacroscope and length of yolk and larva were monitored using Stereo Olympus microscope with ocular micrometer. The division into animal and vegetal poles was observed 22 minutes after activation. The first cleavage occurred 65 minutes after activation while the second division which was perpendicular to the first line of division occurred 74 minutes after activation. This was quickly followed by the third and fourth cleavage at 80th and 82nd minutes after activation respectively. Morular stage was reached at 4 hours 20 minutes with formation of optic bud at 14 hours 35 minutes. (DBO) Developing embryo hatched after 27 hours of activation at a mean length of 6.63 and mean yolk length of 2.17. Yolk size decrease at an average rate of 38.5 % till the 5th day of total absorption. Growth of larvae proceeded faster in tail-anus region than in anus-snout portion of the body. The rate of yolk absorption and larva development (survival) as monitored in this work gives important information in Research and development programme for H. longifilis larva - an important aspect of Research development and implementation of appropriate technologies in small scale fisheries

Toxicité des sulfures dissous chez le poisson-chat africain, Heterobranchus longifilis (Valenciennes, 1840)

Biological tests were carried out using static bioassay systems to determine the median lethal concentration of total sulfide (H2S, HS, S2) for African catfish (Heterobranchus longifilis, Valenciennes, 1840) at fry and juvenile stages.