Seasonal changes in biomass of macrophytes stranded on Yoro Beach along a sargassacean forest in Wakasa Bay,Sea of Japan

ABSTRACT:   Macrophytes stranded on a beach provide food and habitat for many kinds of animals and play important roles in coastal ecosystems. Macrophytes stranded on a sampling beach (56 m long) along a sargassacean forest (400 m long and 88 m wide) were collected every 10 days from late April 2003 to late May 2004. The weight of macrophytes stranded per meter of beach amounted to 1733 g dry wt/m per year. Sargassacean plants were dominant and constituted 72.9% (1263 g dry wt/m per year) of whole stranded macrophytes. Large numbers of macrophytes were stranded just after heavy winter storms and the maximum weight of stranded macrophytes in winter was 407 g dry wt/m. Stranded macrophytes also increased in May to July; the deterioration period of sargassacean species in this region, and the maximum weight in this period was 233 g dry wt/m. The number of sargassacean plants stranded with holdfast increased only in winter. These results suggest that winter storms have an important role in stranding sargassacean plants at Yoro Beach.     

Evaluation of carbohydrate rich diets through common carp culture in manured tanks

Four diets (T₀–T₃) were formulated reducing the fishmeal (Indian) component by 100 g kg^–1 from 300 to 0 g kg^–1 and including proportionately increasing quantities of maize. Diets were fed for 120 days at 50 g kg^–1 body weight to triplicate groups of common carp (av. wt. 2.11–2.18 g) stocked at 1 m^–2 in mud bottomed cement tanks (18 m²), fertilized with poultry manure. Fish growth, SGR and FCR in the different treatments were statistically not significantly different ( P  > 0.05). PER was lowest for the 300 g fishmeal kg^–1 diet treatment (diet T₀), increasing with decrease in dietary fishmeal content (diets T₁–T₃). Fish survival ranged from 96.29 to 100%. Diets influenced carcass composition and digestive enzyme activity. A significant increase in lipid deposition was recorded with increasing dietary carbohydrate content. Amylase, protease and lipase activities were higher in fish fed with diets T₂ and T₃. The protein sparing effect of dietary carbohydrate and the economic implication of eliminating fishmeal from the diet are discussed.     

Fish community composition of a tropical nonestuarine embayment in Zanzibar,Tanzania

ABSTRACT:   By using a seine net, fish samples were taken from the nonestuarine Chwaka Bay (Zanzibar, Tanzania) from the mangroves, mud/sand flats and seagrass beds. Sampling was done twice per month between November 2001 and October 2002. In total, 150 fish species belonging to 55 families were identified. Diversity ( H' ) ranged from 1.9 in mud/sand flats to 3.4 within the Chwaka seagrass beds. Mean density of fishes was significantly higher in the mangrove creeks than in any other habitat (mean = 238.7 ind./1000 m²). Highest, but non-significantly different mean biomasses were recorded in the mangrove creeks (1.7 kg/1000 m²) and in the Marumbi seagrass beds (1.6 kg/1000 m²). The mangrove channel had the lowest biomass (0.6 kg/1000 m²). A high overlap in species composition (as high as 93.4% similarity) was found for adjoining habitats (i.e. mangrove creeks and mangrove channel), while habitats that were far apart showed low overlap (6.6% similarity for the Marumbi seagrass beds and mangrove creeks). On average, 58.4 and 63.2% in terms of abundance and biomass, respectively, of the fish assemblage of Chwaka Bay were of commercial fishery importance. Thus, Chwaka Bay appears to be an important juvenile habitat for various commercially important fish species.     

Biomass and production of the euphausiid Euphausia pacifica along the coastal waters off north-eastern Japan

ABSTRACT:   Biomass and production of Euphausia pacifica off south-eastern Hokkaido (41–43°N), Sanriku (38–41°N), and Joban (36–38°N) were investigated every two months from March 1997 to February 1998. High biomass was found in summer–autumn off south-eastern Hokkaido, and in the late winter–early summer off Sanriku and Joban. Annual mean biomass was 381, 314 and 258 mg C/m² off south-eastern Hokkaido, Sanriku, and Joban, respectively. The total production (sum of flesh, moults and eggs) during the survey period off south-eastern Hokkaido (3829 mg C/m²) was comparable with that off Sanriku (3872 mg C/m²); both were much higher than that off Joban (2243 mg C/m²). Somatic production during the survey period contributed the highest proportion (51.5–70.9%) to the total production in each coastal area. The somatic production–biomass ratio in each coastal area (5.2–6.9) was an intermediate value among 25 populations of 16 euphausiid species previously reported. This effect resulted from the negative factor of stagnated growth of adults during summer–winter, coupled with positive factors including continuous occurrence of larvae which show high growth rate throughout the year off Sanriku and Joban, and the numerous larvae occurring in October off south-eastern Hokkaido.     

The dietary protein requirement of a bagrid catfish, Mystus nemurus (Cuvier & Valenciennes), determined using semipurified diets of varying protein level

Triplicate groups of Mystus nemurus (Cuvier & Valenciennes) were fed isoenergetic semipurified diets containing seven dietary protein levels from 200 to 500 g kg^–1 diet for 10 weeks. Dietary protein was supplied by graded amounts of a protein mixture (tuna muscle meal:casein:gelatine) at a fixed ratio of 50:37.5:12.5. Mystus nemurus fingerlings of initial weight 7.6 ± 0.2 g were fed close to apparent satiation at 2.5% of their body weight per day in two equal feedings. Growth performance and feed utilization efficiency increased linearly with dietary protein level from 202 to 410 g kg^–1 diet and declined with protein levels of 471 g kg^–1 diet or above. Protein efficiency ratio and apparent net protein utilization started to decline when the fish were fed with dietary protein levels exceeding 471 g kg^–1 diet. Fish fed with lower protein diets (202–295 g kg^–1 diet) had significantly ( P  < 0.05) higher carcass lipid content compared with fish fed with higher protein diets. Carcass lipid contents were inversely related to moisture content. Dietary protein did not significantly affect fish carcass protein and ash content. Using two-slope broken-line analysis, the dietary protein requirement for M. nemurus based on percentage weight gain was estimated to be 440 g kg^–1 diet with a protein to energy ratio of 20 mg protein kJ^–1 gross energy. This level of protein in the diet is recommended for maximum growth of M. nemurus fingerlings weighing between 7 and 18 g under the experimental conditions used in this study.     

The influence of different levels of dietary vitamin E on sea bass Dicentrarchus labrax flesh quality

Sea bass Dicentrarchus labrax fillet quality was investigated after feeding with four diets (A, B, C or D) containing different levels of dietary vitamin E (139 mg kg^–1, 254 mg kg^–1, 493 mg kg^–1 and 942 mg kg^–1, respectively). Six-hundred and eighty fish (mean initial weight 208 g) were equally divided into four 20 m³ tanks and fed for 87 days. Filtered seawater with a temperature ranging from 18.2 to 26.3 °C was supplied continuously. At the end of the experiment, fish were stored at 1 °C for 12 days. At one, three, six, nine and 12 days, 20 fish per group were processed for proximate composition, vitamin E and induced thiobarbituric acid reactive substances (TBARs) analyses. No significant differences in proximate composition were registered between groups. The flesh lipid content ranged from 88.0 g kg^–1 (group B) to 96.8 g kg^–1 (group A). Vitamin E fillet content was significantly different between groups, reaching levels of 98.0, 150.7, 225.2 and 302.0 μg g^–1 lipids for group A, B, C and D, respectively. Induced TBARs values were statistically different only for group A compared with the other groups. No significant variations were registered in relation to preservation time. Because of the positive influence of vitamin E on seafood quality and the correlation between its dietary level and flesh deposition, the α-tocopherol content of the diet should be well above fish minimum requirements.     

Bioencapsulation of erythromycin using adult brine shrimp, Artemia franciscana (Latreille)

Live adult brine shrimp, Artemia franciscana (Latreille), were enriched with erythromycin to determine if Artemia could accumulate therapeutic levels for subsequent feeding to young fish. Three trials were conducted to determine the erythromycin incorporation and survival rates of enriched Artemia when fed either liposomes containing erythromycin or various erythromycin suspensions. Erythromycin concentration in Artemia fed a liposome suspension was low (∼ 5 μg mL⁻¹) relative to Artemia fed the direct suspension (> 100 μg mL⁻¹) over the same time period. When enriched with suspensions up to 1 g erythromycin L⁻¹ sea water for 14 h, Artemia survival was not significantly affected ( P > 0.05) relative to controls. Using a suspension of 1 g L⁻¹, tissue erythromycin concentrations of 109 ± 16 μg erythromycin mL⁻¹  Artemia homogenate (mean ± SEM) were achieved after 12 h. Concentrations above 170 μg mL⁻¹ were obtained using suspensions of 2–5 g L⁻¹, but Artemia survival significantly ( P < 0.05) decreased.     

Relationships between critical photon irradiance for growth and daily compensation point of juvenile Sargassum macrocarpum

SUMMARY: This study was designed to determine the critical photon irradiance for growth and daily compensation point of juvenile Sargassum macrocarpum . Sampling and measurement of natural light conditions were carried out in the S. macrocarpum population at a depth of 8 m off Kiwado in Fukawa Bay, Yamaguchi Prefecture, Japan, from April to June 1998. Photosynthesis and respiration of the juvenile thalli, and diurnal changes in solar irradiance were measured for the same period. The critical photon irradiance for growth of the juvenile thalli observed on the population floor was 1.0–1.5% on the sea surface. The photosynthetic rate of leaf of juvenile thalli increased linearly with increasing photon irradiance when light levels were lower than 50 μM/m² per s. The respiratory rate and light compensation point of the juvenile thalli were 2.49 μL O₂/cm² per h and 4.98 μM/m² per s, respectively. The daily compensation point was estimated with a mathematical model based on photosynthesis–light equations and diurnal changes in solar irradiance. For a day of average solar irradiance over the period of the present study, the estimated daily compensation point of the juvenile thalli was 1.3% on the sea surface. This value agreed well with the observed critical photon irradiance for growth of juvenile S . macrocarpum on the population floor. The results of the study confirm that the mathematical model is effective for estimating the daily compensation point.     

Carbohydrate level in the diet of silver barb, Puntius gonionotus (Bleeker) fingerlings: effect on growth, nutrient utilization and whole body composition

Five iso-nitrogenous (300 g crude protein kg⁻¹ diet) semi-purified diets with graded levels of carbohydrate at 220 (D-1), 260 (D-2), 300 (D-3), 340 (D-4) and 380 (D-5) g kg⁻¹ diet were fed ad libitum to Puntius gonionotus fingerlings (average weight 0.59±0.01 g) in triplicate groups (20 fish replicate⁻¹) for a period of 90 days to determine the effect of the dietary carbohydrate level on the growth, nutrient utilization, digestibility, gut enzyme activity and whole-body composition of fish. Fifteen flow-through cement tanks of 100 L capacity with a flow rate of 0.5 L min⁻¹ were used for rearing the fish. The maximum weight gain, specific growth rate, protein efficiency ratio, RNA:DNA ratio, whole-body protein content, protease activity, protein and energy digestibility and minimum feed conversion ratio (FCR) were found in the D-2 group fed with 260 g carbohydrate kg⁻¹ diet. The highest protein and energy retention was also recorded in the same group. However, from the second-order polynomial regression analysis, the maximum growth and nutrient utilization of P. gonionotus fingerlings was 291.3–298.3 g carbohydrate kg⁻¹ diet at a dietary protein level of 300 g kg⁻¹ with a protein/energy (P/E) ratio of 20.58 −20.75 g protein MJ⁻¹.     

Evaluation of indigenous marine periphytic Amphora, Navicula and Cymbella grown on substrate as feed supplement in Penaeus monodon postlarval hatchery system

Three isolated marine diatoms ( Amphora , Navicula and Cymbella ) grown on substrate were evaluated as feed supplement for Penaeus monodon postlarvae (PL) in hatchery system for a period of 19 days without changing water. Specific growth rate (day⁻¹) (0.27 ± 0.0) and survival (%) (56.3 ± 1.8) of PLs were significantly higher ( P  < 0.05) in treatment tanks when compared with the control (0.20 ± 0.0; 36.0 ± 1.5, respectively). Shrimp PLs reared in substrate-based tanks had significantly higher ( P  < 0.05) levels of protein, lipid (521.0 ± 7.0; 304.0 ± 2 g kg⁻¹ dry weight, respectively), ecosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (189.0 ± 2.0; 176.0 ± 2 g kg⁻¹ of total fatty acid, respectively) than the control (435.0 ± 22.0; 258.0 ± 22 g kg⁻¹ dry weight; 172.0 ± 5.0; 152 ± 2 g kg⁻¹ total fatty acid, respectively). The periphytic diatoms contained protein and lipid (430–490; 230–260 g kg⁻¹ dry weight, respectively), EPA (30–150 g kg⁻¹ of total fatty acids), DHA (20–30 g kg⁻¹ of total fatty acids) and nine essential amino acids. The results showed that isolated marine periphytic diatoms grown on substrate could be used as feed supplement in enhancing the growth and survival of P. monodon postlarvae.     

Use of salt to control ichthyophthiriosis and prevent saprolegniosis in silver perch, Bidyanus bidyanus

The ciliate protozoan, Ichthyophthirius multifiliis , and the fungus, Saprolegnia parasitica , cause the diseases ichthyophthiriosis and saprolegniosis respectively. Both diseases are difficult to control and can cause high mortalities of freshwater fish, including the Australian silver perch, Bidyanus bidyanus (Mitchell). The efficacy of salt (NaCl) in controlling and preventing these diseases in silver perch was evaluated in aquaria and tanks. Low pH levels were also evaluated as a control for ichthyophthiriosis. Concentrations of 2 or 3 g L⁻¹ salt controlled infestations of I. multifiliis , and fish were free of both theronts and trophonts by day 8 at temperatures of 17.3–21.3 °C and by day 6 at 19.2–23.5 °C. Fish treated with 1 g L⁻¹ salt remained infested and all fish in a control treatment (0 g L⁻¹ salt) died. Although the mean survival rates of infested fish at pH levels of 5 or 6 were only 13.9% and 7.6%, respectively, there were no theronts or trophonts on surviving fish after 12 days. Silver perch harvested from a pond and treated with 2 or 3 g L⁻¹ salt did not become infected with S. parasitica and survival was 100%, whereas 16.6% of untreated (0 g L⁻¹ salt) fish became infected and survival was only 66.7%. A concentration of 2 g L⁻¹ NaCl is recommended for the control of ichthyophthiriosis and the prevention of saprolegniosis in silver perch held in tanks, aquaria and re-circulating aquaculture systems.     

Comparative performance of juvenile red abalone, Haliotis rufescens, reared in laboratory with fresh kelp and balanced diets

Juvenile Haliotis rufescens were reared in the laboratory in order to investigate the extent to which fresh kelp and formulated feeds with 250 g kg⁻¹ (25P) and 380 g kg⁻¹ protein content (38P) affected their growth rate, gut residence time (GRT), food consumption ( C ), food conversion ratio (FCR) and digestibility. Abalone from 38P attained the highest growth rate (70.5 ± 4.2 μm day⁻¹; 98.3 ± 6.95 μg day⁻¹), followed by 25P (47.9 ± 2.79 μm day⁻¹; 67.4 ± 2.82 μg day⁻¹) and kelp (23.6 ± 3.36 μm day⁻¹; 28.2 ± 4.11 μg day⁻¹). No significant differences were observed in consumption rate among treatments (0.61–0.68% body weight per day), yet kelp-fed abalone exhibited higher FCR (2.44), protein efficiency ratio (4.42), and apparent digestibility of dry matter (69.5%), protein (69.8%) and gross energy (79.2%) than 38P organisms (59.8, 62.4 and 62.2%, respectively). They also showed longer GRT (23.1 ± 0.93 h). This study demonstrated that formulated diets with 250 g kg⁻¹ and 380 g kg⁻¹ protein inclusion can sustain higher growth rates of juvenile H. rufescens than fresh algae. These differences seem to be due to the amount of dietary protein. Kelp meal appears to improve the consumption and digestibility of balanced diets, and its inclusion in formulated diets is recommended.     

Effects of processing on physical characteristics of diets with distinct levels of carbohydrates and lipids: the outcomes on the growth of pacu (Piaractus mesopotamicus)

The use efficiency and feed conversion of extruded and pelletized diets were compared. Eight isoproteic diets (220 g kg⁻¹ digestible protein) were assayed for 90 days in a 2 × 2 × 2 multifactorial design with two carbohydrate levels (400 and 500 g kg⁻¹), two lipids levels (40 and 80 g kg⁻¹) and two diet processing (pelletization and extrusion) with three repetitions. The growth of Piaractus mesopotamicus fed with these diets and the quality control indices of diets were gauged. The density of extruded diets was lower as carbohydrate level was 400 g kg⁻¹ and lipid 40 g kg⁻¹. The interaction carbohydrate and diet processing presented higher leaching value for low carbohydrate level in extruded diet. Fish fed with extruded diets presented the best feed conversion and protein efficiency ratio. When high levels of carbohydrate and lipid are combined, the weight gain is impaired. The interaction between diet processing diet and lipid levels resulted in the best fish performance when pelletized diets with 40 g kg⁻¹ lipid or extruded diets with 80 g kg⁻¹ lipid were considered. The protein efficiency ratio increased with the increment of carbohydrates in the pelletized diets. The fish show low tolerance to lipids and a preference for carbohydrate when the lipid productive values are taken into account.     

Effects of digestible protein levels in isonitrogenous diets on growth performance and tissue composition of juvenile Atractoscion nobilis

A study was undertaken to estimate the effects of isonitrogenous diets (ca. 604 g kg⁻¹ crude protein) containing formaldehyde-treated (FT) fish meal and graded levels of digestible protein (DP) (541, 491, 372, 347 and 247 g kg⁻¹) on growth performance and tissue composition of juveniles white seabass. Five diets were formulated to contain increasing levels of FT fish meal (from 0 to 384 g kg⁻¹) and decreasing levels of non-treated fish meal (from 480 to 96 g kg⁻¹). Each dietary treatment was fed in triplicate to apparent satiation to groups of 25 fish for 50 days. Significantly higher growth performance and feed conversion ratio were obtained in fish-fed diets containing 491 or 541 g kg⁻¹ DP, compared with all other treatments. Apparent digestibility coefficient of protein in the diets was not significantly affected by the inclusion of treated fish meal in the diets. Estimation of protein requirements using a broken-line regression analysis indicated that maximum weight gain would be obtained with a diet containing 503 ± 23 g kg⁻¹ DP. The results from this study suggest that a single-diet formulation using protein treated with formaldehyde as filler might be useful to estimate the requirement of DP for fish.     

Perception of light intensity by Haliotis discus discus based on locomotor activity patterns

ABSTRACT:   An apparatus to measure the locomotor activity of aquatic benthic organisms at variable low light levels was developed and the diurnal behavioral pattern of the abalone Haliotis discus discus was measured at various low light intensities. During the experiment, abalone were exposed to 12 h light–dark cycles of complete darkness, 0 µmol/m²/s throughout the 12 h dark cycle and, during periods I (days 1–8) and III (days 19–26), the 12 h light cycles were set at 10 µmol/m²/s. During period II (days 10–17), abalone were exposed to a light level during the 12 h light cycles of 1 × 10⁻⁵, 1 × 10⁻⁶, 1 × 10⁻⁷ or 1 × 10⁻⁸ µmol/m²/s and the changes in locomotor activity assessed. At daytime levels of 1 × 10⁻⁵ µmol/m²/s, typical behavioral patterns were observed of high locomotory activity during the night-time cycle. However, at lower light intensities, the distinction between day and night activity patterns became less clear and, at intensities lower than 1 × 10⁻⁷ µmol/m²/s, the difference between activity during the light and dark cycles became negligible. Based on this, we conclude that the threshold of light level perception in relation to locomotor activity is approximately 1 × 10⁻⁷ µmol/m²/s. The significance of these results in relation to the entrainment of behavior in abalone is discussed.     

Dietary methionine requirement of juvenile Arctic charr Salvelinus alpinus (L.)

The dietary methionine requirement of juvenile Arctic charr Salvelinus alpinus (L.) was assessed by feeding diets supplemented with graded levels of DL-methionine (9, 12, 15, 18, 21, and 24 g kg⁻¹dietary protein) for 16 weeks at 12°C. All diets contained 400 g kg⁻¹ protein, 170 g kg⁻¹ lipid, 66 g kg⁻¹ ash and an estimated 17.5 MJ digestible energy (DE) kg⁻¹. When live-weight gain was examined using quadratic regression, the estimate of methionine requirement for optimal growth was 17.6 g kg⁻¹ of dietary protein (DP) or 7 g kg⁻¹ of the diet. Requirements estimated on the basis of carcass protein and energy gains were 18.8 and 17.9 g kg⁻¹ DP, respectively. Plasma methionine concentrations and ocular focal length variability measurements did not provide a sensitive measure of requirement, because each responded in a linear fashion to increasing dietary methionine levels. Based on the prevalence of cataracts, the methionine level required to prevent lens pathology (26.7 g kg⁻¹ DP) appears to be higher than that required for maximum growth.     

Bioremediation of organically enriched sediment deposited below fish farms with artificially mass-cultured colonies of a deposit-feeding polychaete <Emphasis Type="Italic">Capitella</Emphasis> sp. I

ABSTRACT:   For bioremediation of organically enriched sediment deposited below fish farms, the extremely high potential for population growth of a deposit-feeding polychaete, Capitella sp. I, in the organically enriched sediment, and the effect on decomposition of organic matter in the sediment, were examined. A mass-culturing technique was conducted for this species. Bioremediation experiments were conducted on the organically enriched sediment in a fish farm in Kusuura Bay, Japan in 2003–2006. Approximately 1.7 million individuals of the worms were placed on the sediment below one net pen in December 2003, 9.3 million individuals in November 2004, and 2.2 million individuals in November 2005. After the worms were spread on the sediment, they rapidly increased in number and reached the highest densities of approximately 134 000 inds/m² in February 2004, 527 000 inds/m² in March 2005 and 103 000 inds/m² in January 2006. In the process of rapid population growth, the decomposition of the organic matter of the sediment was enhanced markedly. Our results demonstrate that the promotion of population growth by spreading cultured colonies of Capitella can enhance the decomposition rate of organic matter markedly in organically enriched sediment below fish farms. This method is promising for minimization of the negative effects of fish farms.     

Optimal dietary lipid level of silver barb, Puntius gonionotus fingerlings in relation to growth, nutrient retention and digestibility, muscle nucleic acid content and digestive enzyme activity

Five iso-nitrogenous (300 g kg⁻¹ diet) purified diets with graded level of lipid at 40 (D-1), 60 (D-2), 80 (D-3), 100 (D-4) and 120 (D-5) g kg⁻¹ diet were fed to Puntius gonionotus fingerlings for 90 days to determine their dietary lipid requirement. Two hundred and twenty-five fingerlings (average weight 2.34 ± 0.03 g) were equally distributed in five treatments in triplicate groups with 15 fish per replicate. Fifteen flow-through cement tanks of 100 L capacity with a flow rate of 0.5 L min⁻¹ were used for rearing the fish. Specific growth rate (SGR), feed conversion ratio (FCR), nutrient digestibility, retention, digestive enzyme activity, RNA : DNA ratio and whole-body composition were considered as the response parameters with respect to dietary lipid levels. Maximum SGR and minimum FCR with highest RNA : DNA ratio, whole-body protein content and digestive enzyme activity was found in D-3 group fed with 80 g kg⁻¹ diet lipid. Nutrient digestibility was similar in all the groups irrespective of the dietary lipid level. Maximum protein and energy retention was recorded at 80 g kg⁻¹ dietary lipid fed group. However, from the second-order polynomial regression analysis, the maximum growth of P. gonionotus fingerlings was found at 96.9 g lipid kg⁻¹ diet.     

Protracted spawning of St Lawrence River northern pike (Esox lucius): simulated effects on survival, growth, and production

Abstract –  An individual-based early life history model demonstrated that the timing and distribution of St Lawrence River northern pike ( Esox lucius ) spawning could affect subsequent young-of-year (YOY) production during nursery and influence year-class formation. Three different spawning patterns have emerged from empirical studies, where egg deposition occurred along the entire littoral gradient beginning in seasonally flooded emergent habitats in tributaries, progressing to submerged aquatic vegetation in shallow bays, and ending in deep water littoral habitats (up to 6 m). The spawning period is protracted, and typically lasts 6–8 weeks due to the presence of a strong thermal gradient. The model used temperature as the driving variable to predict egg abundance, stage-specific development, growth, survival, and ultimately relative production of YOY northern pike within 1-ha plots representative of the three habitats. Earlier spawning (mean 21 days) and higher mean daily survival and growth yielded higher YOY net production for tributaries (mean = 3095.4 g ha⁻¹, SD = 2028.6) relative to the shallow bay habitat (202.5 g ha⁻¹, SD = 125.7). In contrast, deep littoral habitat represented an ecological sink with little production (<0.9 g ha⁻¹). The results demonstrate the importance of the linkage between spawning and nursery processes in determining reproductive success.     

Effect of fermentation on the nutritive value of sesame seed meal in the diets for rohu, Labeo rohita (Hamilton), fingerlings

Six isonitrogenous (350 g kg⁻¹ crude protein) and isoenergetic (17573 kJ kg⁻¹) experimental diets incorporating raw and fermented sesame ( Seasamum indicum ) seed meal at 200, 300, and 400 g kg⁻¹ into a fishmeal based diet were fed to rohu Labeo rohita fingerlings for 60 days and the growth performance and feed utilization efficiency of the fish was studied. The antinutritional factor phytic acid, from raw sesame seed meal, could be reduced below detection limit by fermentation with lactic acid bacteria ( Lactobacillus acidophilus ). Fermentation of the oilseed meal resulted in reduction of the tannin content from 20 to 10 g kg⁻¹. In terms of growth response, feed conversion ratio and protein efficiency ratio, a diet containing 400 g kg⁻¹ fermented sesame seed meal resulted in a significantly ( P  < 0.01) best fish performance. In general, growth and feed utilization efficiencies of fish fed fermented sesame seed meal diets were superior to those fed raw oilseed meal diets. Apparent protein digestibility (APD) values decreased with increasing levels of raw oilseed meal. APD was, however, significantly ( P  < 0.01) higher at all levels of incorporation of fermented sesame seed meal, while diets containing raw oilseed meal resulted in poor protein and lipid digestibility. Carcass protein and lipid contents of fish fed fermented sesame seed meal diets increased with increasing level of incorporation, being highest with 400 g kg⁻¹ fermented oilseed meal-containing diet. The results showed that sesame seed meal may be incorporated in carp diets up to 200 g kg⁻¹ and 400 g kg⁻¹ in raw and treated (fermented) forms respectively.