ALBERT

Notes: In a series of three experiments during 1998-99 and 1999-2000 at Gazipur, Bangladesh, the causes of segregation of Ogura cytoplasmic genetic male sterility in local cultivars of radish were studied. Male-sterile populations at the BC5 and BC6 generations were grown under a range of field temperatures for 2 years and the results on pollen fertility tests revealed that the expression of male sterility was not affected by temperature. Neither was a genotype-year interaction found. The unexpected segregation observed in the male-sterile backcross generations might be due to the presence of restorer alleles in the maintainer parents.

Notes: Abstract. Three oilseed meals (mustard, linseed and sesame) of Bangladeshi origin were evaluated as fish meal substitutes in diets of common carp, Cyprinus carpio L. These oilseed meals were included in the diet at various levels (25, 50 and 75% of dietary protein) and the response of fish fed these diets was compared to fish fed a fish meal based control diet (40% protein). On the basis of observed growth rate, food conversion ratio, protein efficiency ratio and apparent net protein utilization, the control diet produced significantly (P〈 0.05) the best growth performance. Growth responses were significantly affected by both type and inclusion level of oilseed protein. Of the oilseed proteins tested, the 25% mustard protein and 25% linseed protein diets produced significantly (P〈 0.05) better growth performances than higher inclusion levels tested. Apparent protein digestibilities (APDs) for all diets were fairly high, ranging from 77.72 to 89.8O%. In general, APD values decreased with increasing plant protein. Fish fed diets containing higher levels of oilseed protein had significantly (P〈 0.05) higher carcass moisture and lower carcass lipid contents. Fish fed 50% mustard protein had histological abnormalities in liver and thyroid tissues. Results are discussed with respect to dietary levels of essential amino acid and anti-nutritional factors.

Notes: This study investigated the effects of nursing duration on the subsequent performance of rohu (R) Labeo rohita and mrigal (M) Cirrhina mrigala in polyculture with monosex male Nile tilapia (T) Oreochromis niloticus at four levels of pond fertilization. Nile tilapia, rohu and mrigal were stocked at a ratio of 4:1:1 in a 90-day trial based on 40 20-m2 pens fixed in four 400-m2 earthen ponds. Growth of carp fingerlings during prolonged nursing (5 or 12 months) was stunted compared with fish nursed over a conventional duration of 3 months (3) but showed superior growth subsequently. Mean daily weight gain of stunted rohu (12) ranged from 2.2 to 2.8 g per fish day−1 compared with 1.1–1.6 g per fish day−1 for younger fish (3). The comparable ranges for mrigal were 1.9–2.8 and 1.4–2.1 g per fish day−1. Growth of Nile tilapia was inversely related to duration of carp nursing at the four levels of fertilization. Nile tilapia showed more response to increasing levels of fertilizer input (Y=−1.421+1.716X, where Y is the daily weight gain of Nile tilapia and X is the fertilizer level, r2=0.98, P〈0.01, n=12). At a high level of fertilization (3.0 kg N:1.5 kg P ha−1 day−1), performance of stunted fingerlings (5 and 12) of both rohu and mrigal was similar (range 2.3–2.8 g per fish day−1, P〉0.05), but younger mrigal (M3) grew faster than rohu (2.1 g per fish day−1 and 1.6 g per fish day−1 respectively). Older rohu (12) appeared to perform particularly well, and Nile tilapia poorly at the lowest level of fertilization (1.5 N:0.75 kg P ha−1 day−1), suggesting the impact of age of seed on competition within polycultures. The net fish yield (NFY) of tilapia was not affected significantly (P〉0.05) by differential stocking age of carps; therefore, combined NFY of the three experimental fish species was not affected by the age of carp, as tilapia was the dominant species in polyculture. The highest combined NFY of all species in the most intensively fertilized pond (3.0 N:1.5 P kg ha−1 day−1) was calculated at 4.06±0.08 g·m−2 day−1, which was significantly higher (P〈0.001) than the yield (1.82±0.12 g·m−2 day−1) from the pond with the lowest fertilization. At the highest fertilizer level, tilapia, rohu and mrigal contributed 72%, 14% and 14%, respectively, to the NFY, whereas the ratio was 60%, 20% and 20% at the lowest fertilization level. The study indicated that yields from tilapia in polyculture with the two carp species in more eutrophic water can be optimized if advanced nursing of carps is practised. Moreover, higher inputs of inorganic fertilizer and advanced nursing of carp are economically attractive under Bangladeshi conditions. Advanced nursing of rohu also improves its performance in more extensive systems when tilapia densities are high.

Notes: Cycles of movement and feeding of African catfish, Clarias gariepinus (Burchell 1822) fingerlings (113.48 ± 1.87 mm total length) were studied using an infrared illumination and video recording system. The study was carried out over a 15-day period with a group of 40 fish held at 30 °C under a 12-h light:12-h dark photoperiod. The fish were nocturnal and took over 70% of their daily ration at night when given access to food 24 h a day. When feeding was restricted to the light phase, feeding activity decreased, but nocturnal feeding was restored from the second day after a return to 24-h food access.

Notes: An 8-week feeding trial was conducted using tilapia, Oreochromis niloticus L., in a recirculation system maintained at 27±0.2°C to observe the negative effects of Sesbania endosperm on growth and nutrient utilization. Five experimental diets were formulated to contain 32% protein, of which fishmeal was the major source. Endosperm separated from Sesbania seeds was included at levels of 0.0%, 2.9%, 5.8%, 8.7% and 11.6% in diets 1 (control), 2, 3, 4 and 5, respectively, equivalent to levels of 0.0%, 9.7%, 19.4%, 29.1% and 38.8%, respectively, of whole Sesbania seeds. Each treatment had two replicates, eight fish per replicate, with a mean initial live weight of 5.2±0.1 g. Fish were fed 20 g per  kg metabolic body weight of fish daily. The body weight gain, metabolic growth rate, feed conversion ratio, protein efficiency ratio, protein productive value and energy retention of fish fed the control and diet 2 were significantly better (P〈0.05) than those of fish fed the other diets. Physical observation showed that the intestines of the fish fed diets that included endosperm contained loose, viscous and sticky material. Fish fed diets 3, 4 and 5 had a lower proportion of dry matter in their faeces, and lower apparent crude lipid and energy digestibility coefficients compared with fish fed the control diet and diet 2. They also had significantly reduced levels of muscle and plasma cholesterol, whole-body crude protein, lipid and gross energy.

Notes: An 8-week feeding trial was conducted in a warmwater recirculation system at 27 ± 0.2 °C to evaluate the nutritive value of dhaincha (Sesbania aculeata) seed meal as a possible fish meal substitute in the diet of tilapia. Five isonitrogenous and isoenergetic diets were formulated to contain 32% crude protein and 18.4 kJ g−1 gross energy. Sesbania seed meal was included in diets at various levels [0%, 9.7%, 19.4%, 29.1% and 38.8% for diets 1 (control), 2, 3, 4 and 5, respectively, which correspond to 0%, 10%, 20%, 30% and 40% of dietary crude protein]. Each treatment had two replicates, eight fish per replicate, with mean initial weight of 7.06 ± 0.03 g. Fish were fed 20 g kg−1 metabolic body weight daily. On the basis of the observed growth rate, feed conversion ratio, protein efficiency ratio, apparent net protein utilization and energy retention, diets 1 (control) and 2 (containing 9.7% Sesbania meal) were similar and significantly (P 〈 0.05) better than the other dietary groups. Fish fed diets 3, 4 and 5 containing higher levels of Sesbania meal showed significantly reduced growth performance compared with those fed diets 1 and 2. Fish fed diets 3, 4 and 5 had significantly lower faecal dry matter (DM) content, apparent crude protein, lipid and energy digestibility and reduced levels of cholesterol compared with the control and diet 2. Fish fed diets containing higher levels (〉9.7%) of Sesbania meal had significantly higher whole-body moisture, lower lipid and gross energy content. The lower growth performance of fish fed diets containing higher levels of Sesbania meal is thought to result from the presence of tannins, saponin and the non-starch polysaccharide content of the seed. The results of this study showed that inclusion of up to 9.7% untreated Sesbania seed meal (10% of the dietary protein) in the diet did not affect the growth performance and nutrient utilization in tilapia.

Notes: Morphological changes are described in Japanese flounder Paralichthys olivaceus larvae and juveniles with emphasis on growth during the period of metamorphosis. Ontogenetic changes in condition factor and lipid, glycogen and protein levels were also analysed to determine the utilization of stored energy. Fish grew from 6·6 to 20·3 mm LT(1·15 to 84·4 mg in mass, M) during the period from 11 to 40 days after hatching (DAH) at 19·3° C. Per cent specific growth rate per day (%G day−1) for wet mass was lowest during the metamorphic phase (21–30 DAH) compared to pre-(11–20 DAH) and post-metamorphic (31–40 DAH) phases. When LT and M were expressed as 〈inlineGraphic alt="inline image" href="urn:x-wiley:00221112:JFB251:JFB_251_mu1" location="equation/JFB_251_mu1.gif"/〉, the b value was highest during the pre-metamorphic phase and lowest during the metamorphic phase. These findings indicate that the developmental changes that occur during metamorphosis of Japanese flounder are closely related to the growth pattern. Moisture, lipid and glycogen contents were also at the lowest level during metamorphosis compared to pre- and post-metamorphosis, which suggest that Japanese flounder use their energy reserves to accomplish metamorphosis due to an apparent decline in feeding during this period.

Notes: We determine the effects of micro-inertia density and the vortex viscosity on laminar free convection boundary layer flow of a thermomicropolar fluid past a vertical plate with exponentially varying surface temperature as well as surface heat flux. The governing nonsimilarity boundary layer equations are analyzed using: first, a series solution for small ? (a scaled streamwise distribution of micro-inertia density), second, an asymptotic solution for large ? and, third, a full numerical solution implicit finite difference method together with Keller-box scheme. Results are expressed in terms of local skin friction and local Nusselt number. The effects of varying the vortex viscosity parameter, ?, surface temperature and the surface heat flux gradient n and m respectively against ? for fluids having Prandtl number equals 0.72 and 7.0 are determined.